Change search
Refine search result
1 - 50 of 50
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Anderl, Ines
    et al.
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Institute of Biosciences and Medical Technology, BioMediTech, University of Tampere, Tampere, Finland.
    Vesala, Laura
    Ihalainen, Teemu O.
    Vanha-aho, Leena-Maija
    Andó, István
    Rämet, Mika
    Hultmark, Dan
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Institute of Biosciences and Medical Technology, BioMediTech, University of Tampere, Tampere, Finland.
    Transdifferentiation and Proliferation in Two Distinct Hemocyte Lineages in Drosophila melanogaster Larvae after Wasp Infection2016In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 12, no 7, article id e1005746Article in journal (Refereed)
    Abstract [en]

    Cellular immune responses require the generation and recruitment of diverse blood cell types that recognize and kill pathogens. In Drosophila melanogaster larvae, immune-inducible lamellocytes participate in recognizing and killing parasitoid wasp eggs. However, the sequence of events required for lamellocyte generation remains controversial. To study the cellular immune system, we developed a flow cytometry approach using in vivo reporters for lamellocytes as well as for plasmatocytes, the main hemocyte type in healthy larvae. We found that two different blood cell lineages, the plasmatocyte and lamellocyte lineages, contribute to the generation of lamellocytes in a demand-adapted hematopoietic process. Plasmatocytes transdifferentiate into lamellocyte-like cells in situ directly on the wasp egg. In parallel, a novel population of infection-induced cells, which we named lamelloblasts, appears in the circulation. Lamelloblasts proliferate vigorously and develop into the major class of circulating lamellocytes. Our data indicate that lamellocyte differentiation upon wasp parasitism is a plastic and dynamic process. Flow cytometry with in vivo hemocyte reporters can be used to study this phenomenon in detail.

  • 2. Avican, Kemal
    et al.
    Fahlgren, Anna
    Huss, Mikael
    KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Heroven, Ann Kathrin
    Beckstette, Michael
    Dersch, Petra
    Fallman, Maria
    Reprogramming of Yersinia from Virulent to Persistent Mode Revealed by Complex In Vivo RNA-seq Analysis2015In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 11, no 1Article in journal (Refereed)
    Abstract [en]

    We recently found that Yersinia pseudotuberculosis can be used as a model of persistent bacterial infections. We performed in vivo RNA-seq of bacteria in small cecal tissue biopsies at early and persistent stages of infection to determine strategies associated with persistence. Comprehensive analysis of mixed RNA populations from infected tissues revealed that Y. pseudotuberculosis undergoes transcriptional reprogramming with drastic down-regulation of T3SS virulence genes during persistence when the pathogen resides within the cecum. At the persistent stage, the expression pattern in many respects resembles the pattern seen in vitro at 26oC, with for example, up-regulation of flagellar genes and invA. These findings are expected to have impact on future rationales to identify suitable bacterial targets for new antibiotics. Other genes that are up-regulated during persistence are genes involved in anaerobiosis, chemotaxis, and protection against oxidative and acidic stress, which indicates the influence of different environmental cues. We found that the Crp/CsrA/RovA regulatory cascades influence the pattern of bacterial gene expression during persistence. Furthermore, arcA, fnr, frdA, and wrbA play critical roles in persistence. Our findings suggest a model for the life cycle of this enteropathogen with reprogramming from a virulent to an adapted phenotype capable of persisting and spreading by fecal shedding.

  • 3.
    Avican, Kemal
    et al.
    Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Fahlgren, Anna
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Huss, Mikael
    Heroven, Ann Kathrin
    Beckstette, Michael
    Dersch, Petra
    Fällman, Maria
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    Reprogramming of Yersinia from Virulent to Persistent Mode Revealed by Complex In Vivo RNA-seq Analysis2015In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 11, no 1, article id e1004600Article in journal (Refereed)
    Abstract [en]

    We recently found that Yersinia pseudotuberculosis can be used as a model of persistent bacterial infections. We performed in vivo RNA-seq of bacteria in small cecal tissue biopsies at early and persistent stages of infection to determine strategies associated with persistence. Comprehensive analysis of mixed RNA populations from infected tissues revealed that Y. pseudotuberculosis undergoes transcriptional reprogramming with drastic down-regulation of T3SS virulence genes during persistence when the pathogen resides within the cecum. At the persistent stage, the expression pattern in many respects resembles the pattern seen in vitro at 26oC, with for example, up-regulation of flagellar genes and invA. These findings are expected to have impact on future rationales to identify suitable bacterial targets for new antibiotics. Other genes that are up-regulated during persistence are genes involved in anaerobiosis, chemotaxis, and protection against oxidative and acidic stress, which indicates the influence of different environmental cues. We found that the Crp/CsrA/RovA regulatory cascades influence the pattern of bacterial gene expression during persistence. Furthermore, arcA, fnr, frdA, and wrbA play critical roles in persistence. Our findings suggest a model for the life cycle of this enteropathogen with reprogramming from a virulent to an adapted phenotype capable of persisting and spreading by fecal shedding.

  • 4. Bachmann, Julie
    et al.
    Burte, Florence
    Pramana, Setia
    Conte, Ianina
    Brown, Biobele J.
    Orimadegun, Adebola E.
    Ajetunmobi, Wasiu A.
    Afolabi, Nathaniel K.
    Akinkunmi, Francis
    Omokhodion, Samuel
    Akinbami, Felix O.
    Shokunbi, Wuraola A.
    Kampf, Caroline
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Molecular and Morphological Pathology.
    Pawitan, Yudi
    Uhlen, Mathias
    Sodeinde, Olugbemiro
    Schwenk, Jochen M.
    Wahlgren, Mats
    Fernandez-Reyes, Delmiro
    Nilsson, Peter
    Affinity Proteomics Reveals Elevated Muscle Proteins in Plasma of Children with Cerebral Malaria2014In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 10, no 4, p. e1004038-Article in journal (Refereed)
    Abstract [en]

    Systemic inflammation and sequestration of parasitized erythrocytes are central processes in the pathophysiology of severe Plasmodium falciparum childhood malaria. However, it is still not understood why some children are more at risks to develop malaria complications than others. To identify human proteins in plasma related to childhood malaria syndromes, multiplex antibody suspension bead arrays were employed. Out of the 1,015 proteins analyzed in plasma from more than 700 children, 41 differed between malaria infected children and community controls, whereas 13 discriminated uncomplicated malaria from severe malaria syndromes. Markers of oxidative stress were found related to severe malaria anemia while markers of endothelial activation, platelet adhesion and muscular damage were identified in relation to children with cerebral malaria. These findings suggest the presence of generalized vascular inflammation, vascular wall modulations, activation of endothelium and unbalanced glucose metabolism in severe malaria. The increased levels of specific muscle proteins in plasma implicate potential muscle damage and microvasculature lesions during the course of cerebral malaria.

  • 5.
    Bachmann, Julie
    et al.
    KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Burte, Florence
    Pramana, Setia
    Conte, Ianina
    Brown, Biobele J.
    Orimadegun, Adebola E.
    Ajetunmobi, Wasiu A.
    Afolabi, Nathaniel K.
    Akinkunmi, Francis
    Omokhodion, Samuel
    Akinbami, Felix O.
    Shokunbi, Wuraola A.
    Kampf, Caroline
    Pawitan, Yudi
    Uhlén, Mathias
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Sodeinde, Olugbemiro
    Schwenk, Jochen M.
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Wahlgren, Mats
    Fernandez-Reyes, Delmiro
    Nilsson, Peter
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Affinity Proteomics Reveals Elevated Muscle Proteins in Plasma of Children with Cerebral Malaria2014In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 10, no 4, p. e1004038-Article in journal (Refereed)
    Abstract [en]

    Systemic inflammation and sequestration of parasitized erythrocytes are central processes in the pathophysiology of severe Plasmodium falciparum childhood malaria. However, it is still not understood why some children are more at risks to develop malaria complications than others. To identify human proteins in plasma related to childhood malaria syndromes, multiplex antibody suspension bead arrays were employed. Out of the 1,015 proteins analyzed in plasma from more than 700 children, 41 differed between malaria infected children and community controls, whereas 13 discriminated uncomplicated malaria from severe malaria syndromes. Markers of oxidative stress were found related to severe malaria anemia while markers of endothelial activation, platelet adhesion and muscular damage were identified in relation to children with cerebral malaria. These findings suggest the presence of generalized vascular inflammation, vascular wall modulations, activation of endothelium and unbalanced glucose metabolism in severe malaria. The increased levels of specific muscle proteins in plasma implicate potential muscle damage and microvasculature lesions during the course of cerebral malaria.

  • 6.
    Bett, Cyrus
    et al.
    Department of Pathology, University of California, San Diego, La Jolla, California, United States of America.
    Kurt, Tim D.
    Department of Pathology, University of California, San Diego, La Jolla, California, United States of America.
    Lucero, Melanie
    Department of Pathology, University of California, San Diego, La Jolla, California, United States of America.
    Trejo, Margarita
    Department of Neuroscience, University of California, San Diego, La Jolla, California, United States of America.
    Rozemuller, Annemieke J.
    Dutch Surveillance Centre for Prion Diseases, University Medical Centre Utrecht, Utrecht, The Netherlands.
    Kong, Qingzhong
    Department of Pathology, Case Western Reserve University, Cleveland, Ohio, United States of America.
    Nilsson, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Masliah, Eliezer
    Department of Neuroscience, University of California, San Diego, La Jolla, California, United States of America.
    Oldstone, Michael B.
    Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California, United States of America.
    Sigurdson, Christina J.
    Department of Pathology, Immunology, and Microbiology, University of California, Davis, Davis, California, United States of America.
    Defining the Conformational Features of Anchorless, Poorly Neuroinvasive Prions2013In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 9, no 4Article in journal (Refereed)
    Abstract [en]

    Infectious prions cause diverse clinical signs and form an extraordinary range of structures, from amorphous aggregates to fibrils. How the conformation of a prion dictates the disease phenotype remains unclear. Mice expressing GPI-anchorless or GPI-anchored prion protein exposed to the same infectious prion develop fibrillar or nonfibrillar aggregates, respectively, and show a striking divergence in the disease pathogenesis. To better understand how a prion's physical properties govern the pathogenesis, infectious anchorless prions were passaged in mice expressing anchorless prion protein and the resulting prions were biochemically characterized. Serial passage of anchorless prions led to a significant decrease in the incubation period to terminal disease and altered the biochemical properties, consistent with a transmission barrier effect. After an intraperitoneal exposure, anchorless prions were only weakly neuroinvasive, as prion plaques rarely occurred in the brain yet were abundant in extracerebral sites such as heart and adipose tissue. Anchorless prions consistently showed very high stability in chaotropes or when heated in SDS, and were highly resistant to enzyme digestion. Consistent with the results in mice, anchorless prions from a human patient were also highly stable in chaotropes. These findings reveal that anchorless prions consist of fibrillar and highly stable conformers. The additional finding from our group and others that both anchorless and anchored prion fibrils are poorly neuroinvasive strengthens the hypothesis that a fibrillar prion structure impedes efficient CNS invasion.

  • 7. Bollampalli, V. P.
    et al.
    Harumi Yamashiro, L.
    Feng, X.
    Bierschenk, D.
    Gao, Y.
    Blom, Hans
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Henriques-Normark, B.
    Nylén, S.
    Rothfuchs, A. G.
    BCG Skin Infection Triggers IL-1R-MyD88-Dependent Migration of EpCAMlow CD11bhigh Skin Dendritic cells to Draining Lymph Node During CD4+ T-Cell Priming2015In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 11, no 10, article id e1005206Article in journal (Refereed)
    Abstract [en]

    The transport of antigen from the periphery to the draining lymph node (DLN) is critical for T-cell priming but remains poorly studied during infection with Mycobacterium bovis Bacille Calmette-Guérin (BCG). To address this we employed a mouse model to track the traffic of Dendritic cells (DCs) and mycobacteria from the BCG inoculation site in the skin to the DLN. Detection of BCG in the DLN was concomitant with the priming of antigen-specific CD4+ T cells at that site. We found EpCAMlow CD11bhigh migratory skin DCs to be mobilized during the transport of BCG to the DLN. Migratory skin DCs distributed to the T-cell area of the LN, co-localized with BCG and were found in close apposition to antigen-specific CD4+ T cells. Consequently, blockade of skin DC traffic into DLN dramatically reduced mycobacterial entry into DLN and muted T-cell priming. Interestingly, DC and mycobacterial entry into the DLN was dependent on IL-1R-I, MyD88, TNFR-I and IL-12p40. In addition, we found using DC adoptive transfers that the requirement for MyD88 in BCG-triggered migration was not restricted to the migrating DC itself and that hematopoietic expression of MyD88 was needed in part for full-fledged migration. Our observations thus identify a population of DCs that contribute towards the priming of CD4+ T cells to BCG infection by transporting bacilli into the DLN in an IL-1R-MyD88-dependent manner and reveal both DC-intrinsic and -extrinsic requirements for MyD88 in DC migration.

  • 8. Braun, Monika
    et al.
    Bjorkström, Niklas K.
    Gupta, Shawon
    Sundström, Karin
    Ahlm, Clas
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Infectious Diseases.
    Klingström, Jonas
    Ljunggren, Hans-Gustaf
    NK Cell Activation in Human Hantavirus Infection Explained by Virus-Induced IL-15/IL15R alpha Expression2014In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 10, no 11, p. e1004521-Article in journal (Refereed)
    Abstract [en]

    Clinical infection with hantaviruses cause two severe acute diseases, hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS). These diseases are characterized by strong immune activation, increased vascular permeability, and up to 50% case-fatality rates. One prominent feature observed in clinical hantavirus infection is rapid expansion of natural killer (NK) cells in peripheral blood of affected individuals. We here describe an unusually high state of activation of such expanding NK cells in the acute phase of clinical Puumala hantavirus infection. Expanding NK cells expressed markedly increased levels of activating NK cell receptors and cytotoxic effector molecules. In search for possible mechanisms behind this NK cell activation, we observed virus-induced IL-15 and IL-15R alpha on infected endothelial and epithelial cells. Hantavirus-infected cells were shown to strongly activate NK cells in a cell-cell contact-dependent way, and this response was blocked with anti-IL-15 antibodies. Surprisingly, the strength of the IL-15-dependent NK cell response was such that it led to killing of uninfected endothelial cells despite expression of normal levels of HLA class I. In contrast, hantavirus-infected cells were resistant to NK cell lysis, due to a combination of virus-induced increase in HLA class I expression levels and hantavirus-mediated inhibition of apoptosis induction. In summary, we here describe a possible mechanism explaining the massive NK cell activation and proliferation observed in HFRS patients caused by Puumala hantavirus infection. The results add further insights into mechanisms behind the immunopathogenesis of hantavirus infections in humans and identify new possible targets for intervention.

  • 9. Bruening, Janina
    et al.
    Lasswitz, Lisa
    Banse, Pia
    Kahl, Sina
    Marinach, Carine
    Vondran, Florian W.
    Kaderali, Lars
    Silvie, Olivier
    Pietschmann, Thomas
    Meissner, Felix
    Gerold, Gisa
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Virology. Umeå University, Faculty of Medicine, Wallenberg Centre for Molecular Medicine at Umeå University (WCMM). Insitute for Experimental Virology, TWINCORE, Centre for Experimental and Clinical Infection Research, a joint venture between the Medical School Hannover and the Helmholtz Centre for Infection Research, Hannover, Germany.
    Hepatitis C virus enters liver cells using the CD81 receptor complex proteins calpain-5 and CBLB2018In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 14, no 7, article id e1007111Article in journal (Refereed)
    Abstract [en]

    Hepatitis C virus (HCV) and the malaria parasite Plasmodium use the membrane protein CD81 to invade human liver cells. Here we mapped 33 host protein interactions of CD81 in primary human liver and hepatoma cells using high-resolution quantitative proteomics. In the CD81 protein network, we identified five proteins which are HCV entry factors or facilitators including epidermal growth factor receptor (EGFR). Notably, we discovered calpain-5 (CAPN5) and the ubiquitin ligase Casitas B-lineage lymphoma proto-oncogene B (CBLB) to form a complex with CD81 and support HCV entry. CAPN5 and CBLB were required for a post-binding and pre-replication step in the HCV life cycle. Knockout of CAPN5 and CBLB reduced susceptibility to all tested HCV genotypes, but not to other enveloped viruses such as vesicular stomatitis virus and human coronavirus. Furthermore, Plasmodium sporozoites relied on a distinct set of CD81 interaction partners for liver cell entry. Our findings reveal a comprehensive CD81 network in human liver cells and show that HCV and Plasmodium highjack selective CD81 interactions, including CAPN5 and CBLB for HCV, to invade cells.

  • 10. Carter, Victoria
    et al.
    Underhill, Ann
    Baber, Ibrahima
    Sylla, Lakamy
    Baby, Mounirou
    Larget-Thiery, Isabelle
    Zettor, Agnès
    Bourgouin, Catherine
    Langel, Ülo
    Stockholm University, Faculty of Science, Department of Neurochemistry.
    Faye, Ingrid
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Otvos, Laszlo
    Wade, John D.
    Coulibaly, Mamadou B.
    Traore, Sekou F.
    Tripet, Frederic
    Eggleston, Paul
    Hurd, Hilary
    Killer bee molecules: antimicrobial peptides as effector molecules to target sporogonic stages of Plasmodium2013In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 9, no 11, article id e1003790Article in journal (Refereed)
    Abstract [en]

    A new generation of strategies is evolving that aim to block malaria transmission by employing genetically modified vectors or mosquito pathogens or symbionts that express anti-parasite molecules. Whilst transgenic technologies have advanced rapidly, there is still a paucity of effector molecules with potent anti-malaria activity whose expression does not cause detrimental effects on mosquito fitness. Our objective was to examine a wide range of antimicrobial peptides (AMPs) for their toxic effects on Plasmodium and anopheline mosquitoes. Specifically targeting early sporogonic stages, we initially screened AMPs for toxicity against a mosquito cell line and P. berghei ookinetes. Promising candidate AMPs were fed to mosquitoes to monitor adverse fitness effects, and their efficacy in blocking rodent malaria infection in Anopheles stephensi was assessed. This was followed by tests to determine their activity against P. falciparum in An. gambiae, initially using laboratory cultures to infect mosquitoes, then culminating in preliminary assays in the field using gametocytes and mosquitoes collected from the same area in Mali, West Africa. From a range of 33 molecules, six AMPs able to block Plasmodium development were identified: Anoplin, Duramycin, Mastoparan X, Melittin, TP10 and Vida3. With the exception of Anoplin and Mastoparan X, these AMPs were also toxic to an An. gambiae cell line at a concentration of 25 µM. However, when tested in mosquito blood feeds, they did not reduce mosquito longevity or egg production at concentrations of 50 µM. Peptides effective against cultured ookinetes were less effective when tested in vivo and differences in efficacy against P. berghei and P. falciparum were seen. From the range of molecules tested, the majority of effective AMPs were derived from bee/wasp venoms.

  • 11. Crawford, Aaron C.
    et al.
    Lehtovirta-Morley, Laura E.
    Alamir, Omran
    Niemiec, Maria Joanna
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Research Group Microbial Immunology, Leibniz Institute for Natural Product Research and Infection Biology–Hans Knoell Institute, Jena, Germany; Center for Sepsis Control and Care (CSCC), University Hospital, Jena, Germany.
    Alawfi, Bader
    Alsarraf, Mohammad
    Skrahina, Volha
    Costa, Anna C. B. P.
    Anderson, Andrew
    Yellagunda, Sujan
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology. Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    Ballou, Elizabeth R.
    Hube, Bernhard
    Urban, Constantin F.
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology. Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    Wilson, Duncan
    Biphasic zinc compartmentalisation in a human fungal pathogen2018In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 14, no 5, article id e1007013Article in journal (Refereed)
    Abstract [en]

    Nutritional immunity describes the host-driven manipulation of essential micronutrients, including iron, zinc and manganese. To withstand nutritional immunity and proliferate within their hosts, pathogenic microbes must express efficient micronutrient uptake and homeostatic systems. Here we have elucidated the pathway of cellular zinc assimilation in the major human fungal pathogen Candida albicans. Bioinformatics analysis identified nine putative zinc transporters: four cytoplasmic-import Zip proteins (Zrt1, Zrt2, Zrt3 and orf19.5428) and five cytoplasmic-export ZnT proteins (orf19.1536/Zrc1, orf19.3874, orf19.3769, orf19.3132 and orf19.52). Only Zrt1 and Zrt2 are predicted to localise to the plasma membrane and here we demonstrate that Zrt2 is essential for C. albicans zinc uptake and growth at acidic pH. In contrast, ZRT1 expression was found to be highly pH dependent and could support growth of the ZRT2-null strain at pH 7 and above. This regulatory paradigm is analogous to the distantly related pathogenic mould, Aspergillus fumigatus, suggesting that pH-adaptation of zinc transport may be conserved in fungi and we propose that environmental pH has shaped the evolution of zinc import systems in fungi. Deletion of C. albicans ZRT2 reduced kidney fungal burden in wild type, but not in mice lacking the zinc-chelating antimicrobial protein calprotectin. Inhibition of zrt2 Delta growth by neutrophil extracellular traps was calprotectin-dependent. This suggests that, within the kidney, C. albicans growth is determined by pathogen-Zrt2 and host-calprotectin. As well as serving as an essential micronutrient, zinc can also be highly toxic and we show that C. albicans deals with this potential threat by rapidly compartmentalising zinc within vesicular stores called zincosomes. In order to understand mechanistically how this process occurs, we created deletion mutants of all five ZnT-type transporters in C. albicans. Here we show that, unlike in Saccharomyces cerevisiae, C. albicans Zrc1 mediates zinc tolerance via zincosomal zinc compartmentalisation. This novel transporter was also essential for virulence and liver colonisation in vivo. In summary, we show that zinc homeostasis in a major human fungal pathogen is a multi-stage process initiated by Zrtl/Zrt2-cellular import, followed by Zrcl-dependent intracellular compartmentalisation.

  • 12. Daskalov, Asen
    et al.
    Gantner, Matthias
    Wälti, Marielle Aulikki
    Schmidlin, Thierry
    Chi N, Celestine
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology. ETH.
    Wasmer, Christian
    Schütz, Anne
    Ceschin, Johanna
    Clavé, Corinne
    Cescau, Sandra
    Meier, Beat
    Riek, Roland
    Saupe, Sven J
    Contribution of specific residues of the β-solenoid fold to HET-s prion function, amyloid structure and stability.2014In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 10, no 6, article id e1004158Article in journal (Refereed)
    Abstract [en]

    The [Het-s] prion of the fungus Podospora anserina represents a good model system for studying the structure-function relationship in amyloid proteins because a high resolution solid-state NMR structure of the amyloid prion form of the HET-s prion forming domain (PFD) is available. The HET-s PFD adopts a specific β-solenoid fold with two rungs of β-strands delimiting a triangular hydrophobic core. A C-terminal loop folds back onto the rigid core region and forms a more dynamic semi-hydrophobic pocket extending the hydrophobic core. Herein, an alanine scanning mutagenesis of the HET-s PFD was conducted. Different structural elements identified in the prion fold such as the triangular hydrophobic core, the salt bridges, the asparagines ladders and the C-terminal loop were altered and the effect of these mutations on prion function, fibril structure and stability was assayed. Prion activity and structure were found to be very robust; only a few key mutations were able to corrupt structure and function. While some mutations strongly destabilize the fold, many substitutions in fact increase stability of the fold. This increase in structural stability did not influence prion formation propensity in vivo. However, if an Ala replacement did alter the structure of the core or did influence the shape of the denaturation curve, the corresponding variant showed a decreased prion efficacy. It is also the finding that in addition to the structural elements of the rigid core region, the aromatic residues in the C-terminal semi-hydrophobic pocket are critical for prion propagation. Mutations in the latter region either positively or negatively affected prion formation. We thus identify a region that modulates prion formation although it is not part of the rigid cross-β core, an observation that might be relevant to other amyloid models.

  • 13.
    Duperthuy, Marylise
    et al.
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    Sjöström, Annika E.
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    Sabharwal, Dharmesh
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    Damghani, Fatemeh
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    Uhlin, Bernt Eric
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    Wai, Sun Nyunt
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    Role of the Vibrio cholerae Matrix Protein Bap1 in Cross-Resistance to Antimicrobial Peptides2013In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 9, no 10, p. e1003620-Article in journal (Refereed)
    Abstract [en]

    Outer membrane vesicles (OMVs) that are released from Gram-negative pathogenic bacteria can serve as vehicles for the translocation of effectors involved in infectious processes. In this study we have investigated the role of OMVs of the Vibrio cholerae O1 El Tor A1552 strain in resistance to antimicrobial peptides (AMPs). To assess this potential role, we grew V. cholerae with sub-lethal concentrations of Polymyxin B (PmB) or the AMP LL-37 and analyzed the OMVs produced and their effects on AMP resistance. Our results show that growing V. cholerae in the presence of AMPs modifies the protein content of the OMVs. In the presence of PmB, bacteria release OMVs that are larger in size and contain a biofilm-associated extracellular matrix protein (Bap1). We demonstrated that Bap1 binds to the OmpT porin on the OMVs through the LDV domain of OmpT. In addition, OMVs from cultures incubated in presence of PmB also provide better protection for V. cholerae against LL-37 compared to OMVs from V. cholerae cultures grown without AMPs or in presence of LL-37. Using a bap1 mutant we showed that cross-resistance between PmB and LL-37 involved the Bap1 protein, whereby Bap1 on OMVs traps LL-37 with no subsequent degradation of the AMP.

  • 14. Floyd, Kyle A.
    et al.
    Moore, Jessica L.
    Eberly, Allison R.
    Good, James A. D.
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Shaffer, Carrie L.
    Zaver, Himesh
    Almqvist, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Skaar, Eric P.
    Caprioli, Richard M.
    Hadjifrangiskou, Maria
    Adhesive Fiber Stratification in Uropathogenic Escherichia coli Biofilms Unveils Oxygen-Mediated Control of Type 1 Pili2015In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 11, no 3, article id e1004697Article in journal (Refereed)
    Abstract [en]

    Bacterial biofilms account for a significant number of hospital-acquired infections and complicate treatment options, because bacteria within biofilms are generally more tolerant to antibiotic treatment. This resilience is attributed to transient bacterial subpopulations that arise in response to variations in the microenvironment surrounding the biofilm. Here, we probed the spatial proteome of surface-associated single-species biofilms formed by uropathogenic Escherichia coli (UPEC), the major causative agent of community-acquired and catheter-associated urinary tract infections. We used matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) imaging mass spectrometry (IMS) to analyze the spatial proteome of intact biofilms in situ. MALDI-TOF IMS revealed protein species exhibiting distinct localizations within surface-associated UPEC biofilms, including two adhesive fibers critical for UPEC biofilm formation and virulence: type 1 pili (Fim) localized exclusively to the air-exposed region, while curli amyloid fibers localized to the air-liquid interface. Comparison of cells grown aerobically, fermentatively, or utilizing an alternative terminal electron acceptor showed that the phase-variable fim promoter switched to the "FF" orientation under oxygen-deplete conditions, leading to marked reduction of type 1 pili on the bacterial cell surface. Conversely, S pili whose expression is inversely related to fim expression were upregulated under anoxic conditions. Tethering the fim promoter in the "ON" orientation in anaerobically grown cells only restored type 1 pili production in the presence of an alternative terminal electron acceptor beyond oxygen. Together these data support the presence of at least two regulatory mechanisms controlling fim expression in response to oxygen availability and may contribute to the stratification of extracellular matrix components within the biofilm. MALDI IMS facilitated the discovery of these mechanisms, and we have demonstrated that this technology can be used to interrogate subpopulations within bacterial biofilms.

  • 15.
    Gulati, Sunita
    et al.
    Sch Med, Div Infect Dis & Immunol, Univ Massachusetts, Worcester MA, USA.
    Schoenhofen, Ian C.
    Human Hlth Therapeut Portfolio, Natl Res Council Canada, Ottawa ON, Canada.
    Whitfield, Dennis M.
    Human Hlth Therapeut Portfolio, Natl Res Council Canada, Ottawa ON, Canada.
    Cox, Andrew D.
    Human Hlth Therapeut Portfolio, Natl Res Council Canada, Ottawa ON, Canada.
    Li, Jianjun
    Michael, Frank St.
    Human Hlth Therapeut Portfolio, Natl Res Council Canada, Ottawa ON, Canada.
    Vinogradov, Evgeny V.
    Human Hlth Therapeut Portfolio, Natl Res Council Canada, Ottawa ON, Canada.
    Stupak, Jacek
    Human Hlth Therapeut Portfolio, Natl Res Council Canada, Ottawa ON, Canada.
    Zheng, Bo
    Sch Med, Div Infect Dis & Immunol, Univ Massachusetts, Worcester MA, USA.
    Ohnishi, Makoto
    Natl Inst Infect Dis, Tokyo, Japan.
    Unemo, Magnus
    Örebro University Hospital. WHO Collaborating Ctr Gonorrhoea & Other STIs, Dept Lab Med Microbiol, Örebro University Hospital, Örebro, Sweden.
    Lewis, Lisa A.
    Sch Med, Div Infect Dis & Immunol, Univ Massachusetts, Worcester MA, USA.
    Taylor, Rachel E.
    Dept Med, Biomed Sci Grad Program, Univ Calif San Diego, La Jolla CA, USA; Glycobiol Res & Training Ctr, Dept Cellular & Mol Med, Univ Calif San Diego, La Jolla CA, USA.
    Landig, Corinna S.
    Dept Med, Biomed Sci Grad Program, Univ Calif San Diego, La Jolla CA, USA; Glycobiol Res & Training Ctr, Dept Cellular & Mol Med, Univ Calif San Diego, La Jolla CA, USA.
    Diaz, Sandra
    Dept Med, Biomed Sci Grad Program, Univ Calif San Diego, La Jolla CA, USA; Glycobiol Res & Training Ctr, Dept Cellular & Mol Med, Univ Calif San Diego, La Jolla CA, USA.
    Reed, George W.
    Sch Med, Prevent & Behav Med, Univ Massachusetts, Worcester MA, USA.
    Varki, Ajit
    Dept Med, Biomed Sci Grad Program, Univ Calif San Diego, La Jolla CA, USA; Glycobiol Res & Training Ctr, Dept Cellular & Mol Med, Univ Calif San Diego, La Jolla CA, USA.
    Rice, Peter A.
    Sch Med, Div Infect Dis & Immunol, Univ Massachusetts, Worcester MA, USA.
    Ram, Sanjay
    Sch Med, Div Infect Dis & Immunol, Univ Massachusetts, Worcester MA, USA.
    Utilizing CMP-Sialic Acid Analogs to Unravel Neisseria gonorrhoeae Lipooligosaccharide-Mediated Complement Resistance and Design Novel Therapeutics2015In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 11, no 12, article id e1005290Article in journal (Refereed)
    Abstract [en]

    Neisseria gonorrhoeae deploys a novel immune evasion strategy wherein the lacto-N-neotetraose (LNnT) structure of lipooligosaccharide (LOS) is capped by the bacterial sialyltransferase, using host cytidine-5'-monophosphate (CMP)-activated forms of the ninecarbon nonulosonate (NulO) sugar N-acetyl-neuraminic acid (Neu5Ac), a sialic acid (Sia) abundant in humans. This allows evasion of complement-mediated killing by recruiting factor H (FH), an inhibitor of the alternative complement pathway, and by limiting classical pathway activation ("serum-resistance"). We utilized CMP salts of six additional natural or synthetic NulOs, Neu5Gc, Neu5Gc8Me, Neu5Ac9Ac, Neu5Ac9Az, legionaminic acid (Leg5Ac7Ac) and pseudaminic acid (Pse5Ac7Ac), to define structural requirements of Sia-mediated serum-resistance. While all NulOs except Pse5Ac7Ac were incorporated into the LNnT-LOS, only Neu5Gc incorporation yielded high-level serum-resistance and FH binding that was comparable to Neu5Ac, whereas Neu5Ac9Az and Leg5Ac7Ac incorporation left bacteria fully serum-sensitive and did not enhance FH binding. Neu5Ac9Ac and Neu5Gc8Me rendered bacteria resistant only to low serum concentrations. While serum-resistance mediated by Neu5Ac was associated with classical pathway inhibition (decreased IgG binding and C4 deposition), Leg5Ac7Ac and Neu5Ac9Az incorporation did not inhibit the classical pathway. Remarkably, CMP-Neu5Ac9Az and CMP-Leg5Ac7Ac each prevented serum-resistance despite a 100-fold molar excess of CMP-Neu5Ac in growth media. The concomitant presence of Leg5Ac7Ac and Neu5Ac on LOS resulted in uninhibited classical pathway activation. Surprisingly, despite near-maximal FH binding in this instance, the alternative pathway was not regulated and factor Bb remained associated with bacteria. Intravaginal administration of CMP-Leg5Ac7Ac to BALB/c mice infected with gonorrhea (including a multidrug-resistant isolate) reduced clearance times and infection burden. Bacteria recovered from CMP-Leg5Ac7Ac-treated mice were sensitive to human complement ex vivo, simulating in vitro findings. These data reveal critical roles for the Sia exocyclic side-chain in gonococcal serum-resistance. Such CMP-NulO analogs may provide a novel therapeutic strategy against the global threat of multidrug-resistant gonorrhea.

  • 16.
    Gupta, Soham
    et al.
    Karolinska Inst, Dept Cell & Mol Biol, Stockholm, Sweden..
    Ylä-Anttila, Päivi
    Karolinska Inst, Dept Cell & Mol Biol, Stockholm, Sweden..
    Callegari, Simone
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Social Sciences, Department of Informatics and Media. Karolinska Inst, Dept Cell & Mol Biol, Stockholm, Sweden.
    Tsai, Ming-Han
    Deutsch Krebsforschungszentrum, Heidelberg, Germany..
    Delecluse, Henri-Jacques
    Deutsch Krebsforschungszentrum, Heidelberg, Germany..
    Masucci, Maria G.
    Karolinska Inst, Dept Cell & Mol Biol, Stockholm, Sweden..
    Herpesvirus deconjugases inhibit the IFN response by promoting TRIM25 autoubiquitination and functional inactivation of the RIG-I signalosome2018In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 14, no 1, article id e1006852Article in journal (Refereed)
    Abstract [en]

    The N-terminal domains of the herpesvirus large tegument proteins encode a conserved cysteine protease with ubiquitin- and NEDD8-specific deconjugase activity. The proteins are expressed during the productive virus cycle and are incorporated into infectious virus particles, being delivered to the target cells upon primary infection. Members of this viral enzyme family were shown to regulate different aspects of the virus life cycle and the innate anti-viral response. However, only few substrates have been identified and the mechanisms of these effects remain largely unknown. In order to gain insights on the substrates and signaling pathways targeted by the viral enzymes, we have used co-immunoprecipitation and mass spectrometry to identify cellular proteins that interact with the Epstein-Barr virus encoded homologue BPLF1. Several members of the 14-3-3-family of scaffold proteins were found amongst the top hits of the BPLF1 interactome, suggesting that, through this interaction, BPLF1 may regulate a variety of cellular signaling pathways. Analysis of the shared protein-interaction network revealed that BPLF1 promotes the assembly of a trimolecular complex including, in addition to 14-3-3, the ubiquitin ligase TRIM25 that participates in the innate immune response via ubiquitination of cytosolic pattern recognition receptor, RIG-I. The involvement of BPLF1 in the regulation of this signaling pathway was confirmed by inhibition of the type-I IFN responses in cells transfected with a catalytically active BPLF1 N-terminal domain or expressing the endogenous protein upon reactivation of the productive virus cycle. We found that the active viral enzyme promotes the dimerization and autoubiquitination of TRIM25. Upon triggering of the IFN response, RIG-I is recruited to the complex but ubiquitination is severely impaired, which functionally inactivates the RIG-I signalosome. The capacity to bind to and functionally inactivate the RIG-I signalosome is shared by the homologues encoded by other human herpesviruses.

  • 17.
    Hägglund, Sara
    et al.
    Swedish Univ Agr Sci, Host Pathogen Interact Grp, Dept Clin Sci, Uppsala, Sweden..
    Blodorn, Krister
    Swedish Univ Agr Sci, Host Pathogen Interact Grp, Dept Clin Sci, Uppsala, Sweden..
    Näslund, Katarina
    Swedish Univ Agr Sci, Host Pathogen Interact Grp, Dept Clin Sci, Uppsala, Sweden..
    Vargmar, Karin
    Swedish Univ Agr Sci, Sect Pathol, Dept Biomed Sci & Vet Publ Hlth, Uppsala, Sweden..
    Bergström, Sara K.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry. Uppsala University, Science for Life Laboratory, SciLifeLab. Uppsala Universitet.
    Mi, Jia
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry. Uppsala Univ, Dept Chem BMC, Sci Life Lab, Analyt Chem, Uppsala, Sweden.;Binzhou Med Univ, Med & Pharm Res Ctr, Yantai, Peoples R China..
    Arainga, Mariluz
    Univ Nebraska Med Ctr, Omaha, NE USA..
    Riffault, Sabine
    Univ Paris Saclay, INRA, Unite Virol & Immunol Mol, Jouy En Josas, France..
    Taylor, Geraldine
    Pirbright Inst, Ash Rd, Pirbright, Surrey, England..
    Pringle, John
    Swedish Univ Agr Sci, Host Pathogen Interact Grp, Dept Clin Sci, Uppsala, Sweden..
    Valarcher, Jean Francois
    Swedish Univ Agr Sci, Host Pathogen Interact Grp, Dept Clin Sci, Uppsala, Sweden..
    Proteome analysis of bronchoalveolar lavage from calves infected with bovine respiratory syncytial virus-Insights in pathogenesis and perspectives for new treatments2017In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 12, no 10, article id e0186594Article in journal (Refereed)
    Abstract [en]

    Human and bovine respiratory syncytial viruses (HRSV/BRSV) are major causes of severe lower respiratory tract infections in children and calves, respectively. Shared epidemiological, clinical, pathological and genetic characteristics of these viruses make comparative research highly relevant. To characterise the host response against BRSV infection, bronchoalveolar lavage supernatant (BAL) from i) non-vaccinated, BRSV-infected ii) vaccinated, BRSV-infected and iii) non-infected calves was analysed by tandem mass spectrometry. Proteins were semi-quantified and protein expression was validated by immunoblotting. Correlations between selected proteins and pathology, clinical signs and virus shedding were investigated. Calves with BRSV-induced disease had increased total protein concentrations and a decreased number of proteins identified in BAL. The protein profile was characterised by neutrophil activation and a reduction in identified antioxidant enzymes. The presence of neutrophils in alveolar septa, the expression level of neutrophil-related or antioxidant proteins and LZTFL1 correlated significantly with disease. Citrullinated histone 3, an indicator of extracellular traps (ETs), was only detected in non-vaccinated, BRSV-infected animals. By bringing disequilibrium in the release and detoxification of reactive oxygen species, generating ETs and causing elastine degradation, exaggerated neutrophil responses might exacerbate RSV-induced disease. Neutrophil-mitigating or antioxidant treatments should be further explored.

  • 18.
    Jearaphunt, Miti
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Comparative Physiology.
    Noonin, Chadanat
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Comparative Physiology.
    Jiravanichpaisal, Pikul
    Nakamura, Seiko
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Comparative Physiology.
    Tassanakajon, Anchalee
    Söderhäll, Irene
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Comparative Physiology.
    Söderhäll, Kenneth
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Comparative Physiology.
    Caspase-1-like regulation of the proPO-system and role of ppA and caspase-1-like cleaved peptides from proPO in innate immunity2014In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 10, no 4, p. e1004059-Article in journal (Refereed)
    Abstract [en]

    Invertebrates rely on innate immunity to respond to the entry of foreign microorganisms. One of the important innate immune responses in arthropods is the activation of prophenoloxidase (proPO) by a proteolytic cascade finalized by the proPO-activating enzyme (ppA), which leads to melanization and the elimination of pathogens. Proteolytic cascades play a crucial role in innate immune reactions because they can be triggered more quickly than immune responses that require altered gene expression. Caspases are intracellular proteases involved in tightly regulated limited proteolysis of downstream processes and are also involved in inflammatory responses to infections for example by activation of interleukin 1ß. Here we show for the first time a link between caspase cleavage of proPO and release of this protein and the biological function of these fragments in response to bacterial infection in crayfish. Different fragments from the cleavage of proPO were studied to determine their roles in bacterial clearance and antimicrobial activity. These fragments include proPO-ppA, the N-terminal part of proPO cleaved by ppA, and proPO-casp1 and proPO-casp2, the fragments from the N-terminus after cleavage by caspase-1. The recombinant proteins corresponding to all three of these peptide fragments exhibited bacterial clearance activity in vivo, and proPO-ppA had antimicrobial activity, as evidenced by a drastic decrease in the number of Escherichia coli in vitro. The bacteria incubated with the proPO-ppA fragment were agglutinated and their cell morphology was altered. Our findings show an evolutionary conserved role for caspase cleavage in inflammation, and for the first time show a link between caspase induced inflammation and melanization. Further we give a more detailed understanding of how the proPO system is regulated in time and place and a role for the peptide generated by activation of proPO as well as for the peptides resulting from Caspase 1 proteolysis.

  • 19.
    Kanatani, Sachie
    et al.
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Fuks, Jonas M.
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Olafsson, Einar B.
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Westermark, Linda
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Chambers, Benedict
    Varas-Godoy, Manuel
    Uhlen, Per
    Barragan, Antonio
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Voltage-dependent calcium channel signaling mediates GABA(A) receptor-induced migratory activation of dendritic cells infected by Toxoplasma gondii2017In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 13, no 12, article id e1006739Article in journal (Refereed)
    Abstract [en]

    The obligate intracellular parasite Toxoplasma gondii exploits cells of the immune system to disseminate. Upon T. gondii-infection,. Upsilon-aminobutyric acid (GABA)/GABAA receptor signaling triggers a hypermigratory phenotype in dendritic cells (DCs) by unknown signal transduction pathways. Here, we demonstrate that calcium (Ca2+) signaling in DCs is indispensable for T. gondii-induced DC hypermotility and transmigration in vitro. We report that activation of GABAA receptors by GABA induces transient Ca2+ entry in DCs. Murine bone marrow-derived DCs preferentially expressed the L-type voltage-dependent Ca2+ channel (VDCC) subtype Cav1.3. Silencing of Cav1.3 by short hairpin RNA or selective pharmacological antagonism of VDCCs abolished the Toxoplasma-induced hypermigratory phenotype. In a mouse model of toxoplasmosis, VDCC inhibition of adoptively transferred Toxoplasma-infected DCs delayed the appearance of cell-associated parasites in the blood circulation and reduced parasite dissemination to target organs. The present data establish that T. gondii-induced hypermigration of DCs requires signaling via VDCCs and that Ca2+ acts as a second messenger to GABAergic signaling via the VDCC Cav1.3. The findings define a novel motility-related signaling axis in DCs and unveil that interneurons and DCs share common GABAergic motogenic pathways. T. gondii employs GABAergic non-canonical pathways to induce host cell migration and facilitate dissemination.

  • 20.
    Khandige, Surabhi
    et al.
    Odense, Denmark.
    Kronborg, Tina
    Odense, Denmark.
    Uhlin, Bernt Eric
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Möller-Jensen, Jakob
    Odense, Denmark.
    sRNA-Mediated Regulation of P-Fimbriae Phase Variation in Uropathogenic Escherichia coli2015In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 11, no 8, article id e1005109Article in journal (Refereed)
    Abstract [en]

    Uropathogenic Escherichia coli (UPEC) are capable of occupying physiologically distinct intracellular and extracellular niches within the urinary tract. This feat requires the timely regulation of gene expression and small RNAs (sRNAs) are known to mediate such rapid adjustments in response to changing environmental cues. This study aimed to uncover sRNA-mediated gene regulation in the UPEC strain UTI89, during infection of bladder epithelial cells. Hfq is an RNA chaperone known to facilitate and stabilize sRNA and target mRNA interactions with bacterial cells. The co-immunoprecipitation and high throughput RNA sequencing of Hfq bound sRNAs performed in this study, revealed distinct sRNA profiles in UPEC in the extracellular and intracellular environments. Our findings emphasize the importance of studying regulatory sRNAs in a biologically relevant niche. This strategy also led to the discovery of a novel virulence-associated trans-acting sRNA-PapR. Deletion of papR was found to enhance adhesion of UTI89 to both bladder and kidney cell lines in a manner independent of type-1 fimbriae. We demonstrate PapR mediated post-transcriptional repression of the P-fimbriae phase regulator gene papI and postulate a role for such regulation in fimbrial cross-talk at the population level in UPEC. Our results further implicate the Leucine responsive protein (LRP) as a transcriptional activator regulating PapR expression. Our study reports, for the first time, a role for sRNAs in regulation of P-fimbriae phase variation and emphasizes the importance of studying pathogenesis-specific sRNAs within a relevant biological niche.

  • 21. Kusmierek, Maria
    et al.
    Hossmann, Joern
    Witte, Rebekka
    Opitz, Wiebke
    Vollmer, Ines
    Volk, Marcel
    Heroven, Ann Kathrin
    Wolf-Watz, Hans
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Dersch, Petra
    A bacterial secreted translocator hijacks riboregulators to control type III secretion in response to host cell contact2019In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 15, no 6, article id e1007813Article in journal (Refereed)
    Abstract [en]

    Numerous Gram-negative pathogens use a Type III Secretion System (T3SS) to promote virulence by injecting effector proteins into targeted host cells, which subvert host cell processes. Expression of T3SS and the effectors is triggered upon host cell contact, but the underlying mechanism is poorly understood. Here, we report a novel strategy of Yersinia pseudotuberculosis in which this pathogen uses a secreted T3SS translocator protein (YopD) to control global RNA regulators. Secretion of the YopD translocator upon host cell contact increases the ratio of post-transcriptional regulator CsrA to its antagonistic small RNAs CsrB and CsrC and reduces the degradosome components PNPase and RNase E levels. This substantially elevates the amount of the common transcriptional activator (LcrF) of T3SS/Yop effector genes and triggers the synthesis of associated virulence-relevant traits. The observed hijacking of global riboregulators allows the pathogen to coordinate virulence factor expression and also readjusts its physiological response upon host cell contact. Author summary Many bacterial pathogens sense contact to host cells and respond by inducing expression of crucial virulence factors. This includes the type III secretion systems (T3SSs) and their substrates, which manipulate different host cell functions to promote colonization and survival of the pathogen within its host. In this study, we used enteropathogenic Yersinia pseudotuberculosis to elucidate the molecular mechanism of how cell contact is transmitted and translated to trigger this process. We found that multiple global riboregulators control the decay and/or translation of the major transcriptional activator of the T3SS. In the absence of cell contact, these important RNA regulators are coopted by one of the substrate proteins of the T3SS to repress expression of the secretion machinery. Translocation of the substrate protein upon cell contact relieves riboregulator-mediated repression. This leads to a strong induction of the master regulator of T3SS/effector gene expression promoting an increase of the virulence potential and provokes a fast adaptation of the pathogen's fitness, e.g. to compensate for the imposed energetic burden.

  • 22.
    Latorre-Margalef, Neus
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Grosbois, Vladimir
    International Research Center in Agriculture for Development, France.
    Wahlgren, John
    Karolinska Institutet.
    Munster, Vincent J.
    Erasmus Medical Center, The Netherlands ; National Institutes of Health, USA.
    Tolf, Conny
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Fouchier, Ron A. M.
    Erasmus Medical Center, The Netherlands.
    Osterhaus, Albert D. M. E.
    Erasmus Medical Center, The Netherlands.
    Olsen, Björn
    Uppsala University.
    Waldenström, Jonas
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Heterosubtypic Immunity to Influenza A Virus Infections in Mallards May Explain Existence of Multiple Virus Subtypes2013In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 9, no 6, article id e1003443Article in journal (Refereed)
    Abstract [en]

    Wild birds, particularly duck species, are the main reservoir of influenza A virus (IAV) in nature. However, knowledge of IAV infection dynamics in the wild bird reservoir, and the development of immune responses, are essentially absent. Importantly, a detailed understanding of how subtype diversity is generated and maintained is lacking. To address this, 18,679 samples from 7728 Mallard ducks captured between 2002 and 2009 at a single stopover site in Sweden were screened for IAV infections, and the resulting 1081 virus isolates were analyzed for patterns of immunity. We found support for development of homosubtypic hemagglutinin (HA) immunity during the peak of IAV infections in the fall. Moreover, re-infections with the same HA subtype and related prevalent HA subtypes were uncommon, suggesting the development of natural homosubtypic and heterosubtypic immunity (p-value = 0.02). Heterosubtypic immunity followed phylogenetic relatedness of HA subtypes, both at the level of HA clades (p-value = 0.04) and the level of HA groups (p-value = 0.05). In contrast, infection patterns did not support specific immunity for neuraminidase (NA) subtypes. For the H1 and H3 Clades, heterosubtypic immunity showed a clear temporal pattern and we estimated within-clade immunity to last at least 30 days. The strength and duration of heterosubtypic immunity has important implications for transmission dynamics of IAV in the natural reservoir, where immune escape and disruptive selection may increase HA antigenic variation and explain IAV subtype diversity.

  • 23. Latorre-Margalef, Neus
    et al.
    Grosbois, Vladimir
    Wahlgren, John
    Munster, Vincent J.
    Tolf, Conny
    Fouchier, Ron A.M.
    Osterhaus, Albert D.M.E.l
    Olsen, Björn
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Infectious Diseases.
    Waldenström, Jonas
    Heterosubtypic Immunity to Influenza A Virus Infections in Mallards May Explain Existence of Multiple Virus Subtypes2013In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 9, no 6, p. e1003443-Article in journal (Refereed)
    Abstract [en]

    Wild birds, particularly duck species, are the main reservoir of influenza A virus (IAV) in nature. However, knowledge of IAV infection dynamics in the wild bird reservoir, and the development of immune responses, are essentially absent. Importantly, a detailed understanding of how subtype diversity is generated and maintained is lacking. To address this, 18,679 samples from 7728 Mallard ducks captured between 2002 and 2009 at a single stopover site in Sweden were screened for IAV infections, and the resulting 1081 virus isolates were analyzed for patterns of immunity. We found support for development of homosubtypic hemagglutinin (HA) immunity during the peak of IAV infections in the fall. Moreover, re-infections with the same HA subtype and related prevalent HA subtypes were uncommon, suggesting the development of natural homosubtypic and heterosubtypic immunity (p-value = 0.02). Heterosubtypic immunity followed phylogenetic relatedness of HA subtypes, both at the level of HA clades (p-value = 0.04) and the level of HA groups (p-value = 0.05). In contrast, infection patterns did not support specific immunity for neuraminidase (NA) subtypes. For the H1 and H3 Clades, heterosubtypic immunity showed a clear temporal pattern and we estimated within-clade immunity to last at least 30 days. The strength and duration of heterosubtypic immunity has important implications for transmission dynamics of IAV in the natural reservoir, where immune escape and disruptive selection may increase HA antigenic variation and explain IAV subtype diversity.

  • 24.
    Lenman, Annasara
    et al.
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology.
    Liaci, A. Manuel
    Liu, Yan
    Årdahl, Carin
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology.
    Rajan, Anandi
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology.
    Nilsson, Emma
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology.
    Bradford, Will
    Kaeshammer, Lisa
    Jones, Morris S.
    Frängsmyr, Lars
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology.
    Feizi, Ten
    Stehle, Thilo
    Arnberg, Niklas
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology.
    Human Adenovirus 52 Uses Sialic Acid-containing Glycoproteins and the Coxsackie and Adenovirus Receptor for Binding to Target Cells2015In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 11, no 2, article id e1004657Article in journal (Refereed)
    Abstract [en]

    Most adenoviruses attach to host cells by means of the protruding fiber protein that binds to host cells via the coxsackievirus and adenovirus receptor (CAR) protein. Human adenovirus type 52 (HAdV-52) is one of only three gastroenteritis-causing HAdVs that are equipped with two different fiber proteins, one long and one short. Here we show, by means of virion-cell binding and infection experiments, that HAdV-52 can also attach to host cells via CAR, but most of the binding depends on sialylated glycoproteins. Glycan microarray, flow cytometry, surface plasmon resonance and ELISA analyses reveal that the terminal knob domain of the long fiber (52LFK) binds to CAR, and the knob domain of the short fiber (52SFK) binds to sialylated glycoproteins. X-ray crystallographic analysis of 52SFK in complex with 2-O-methylated sialic acid combined with functional studies of knob mutants revealed a new sialic acid binding site compared to other, known adenovirus: glycan interactions. Our findings shed light on adenovirus biology and may help to improve targeting of adenovirus-based vectors for gene therapy.

  • 25.
    Lindberg, Bo G.
    et al.
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Tang, Xiongzhuo
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Dantoft, Widad
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Gohel, Priya
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Seyedoleslami Esfahani, Shiva
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Lindvall, Jessica M.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Stockholm University, Science for Life Laboratory (SciLifeLab).
    Engström, Ylva
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Nubbin isoform antagonism governs Drosophila intestinal immune homeostasis2018In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 14, no 3, article id e1006936Article in journal (Refereed)
    Abstract [en]

    Gut immunity is regulated by intricate and dynamic mechanisms to ensure homeostasis despite a constantly changing microbial environment. Several regulatory factors have been described to participate in feedback responses to prevent aberrant immune activity. Little is, however, known about how transcriptional programs are directly tuned to efficiently adapt host gut tissues to the current microbiome. Here we show that the POU/Oct gene nubbin (nub) encodes two transcription factor isoforms, Nub-PB and Nub-PD, which antagonistically regulate immune gene expression in Drosophila. Global transcriptional profiling of adult flies overexpressing Nub-PB in immunocompetent tissues revealed that this form is a strong transcriptional activator of a large set of immune genes. Further genetic analyses showed that Nub-PB is sufficient to drive expression both independently and in conjunction with nuclear factor kappa B (NF-κB), JNK and JAK/STAT pathways. Similar overexpression of Nub-PD did, conversely, repress expression of the same targets. Strikingly, isoform co-overexpression normalized immune gene transcription, suggesting antagonistic activities. RNAi-mediated knockdown of individual nub transcripts in enterocytes confirmed antagonistic regulation by the two isoforms and that both are necessary for normal immune gene transcription in the midgut. Furthermore, enterocyte-specific Nub-PB expression levels had a strong impact on gut bacterial load as well as host lifespan. Overexpression of Nub-PB enhanced bacterial clearance of ingested Erwinia carotovora carotovora 15. Nevertheless, flies quickly succumbed to the infection, suggesting a deleterious immune response. In line with this, prolonged overexpression promoted a proinflammatory signature in the gut with induction of JNK and JAK/STAT pathways, increased apoptosis and stem cell proliferation. These findings highlight a novel regulatory mechanism of host-microbe interactions mediated by antagonistic transcription factor isoforms.

  • 26. Liu, Ning-Ning
    et al.
    Uppuluri, Priya
    Broggi, Achille
    Besold, Angelique
    Ryman, Kicki
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Kambara, Hiroto
    Solis, Norma
    Lorenz, Viola
    Qi, Wanjun
    Acosta-Zaldívar, Maikel
    Emami, S. Noushin
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Bao, Bin
    An, Dingding
    Bonilla, Francisco A.
    Sola-Visner, Martha
    Filler, Scott G.
    Luo, Hongbo R.
    Engström, Ylva
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Ljungdahl, Per Olof
    Culotta, Valeria C.
    Zanoni, Ivan
    Lopez-Ribot, Jose L.
    Köhler, Julia R.
    Intersection of phosphate transport, oxidative stress and TOR signalling in Candida albicans virulence2018In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 14, no 7, article id e1007076Article in journal (Refereed)
    Abstract [en]

    Phosphate is an essential macronutrient required for cell growth and division. Pho84 is the major high-affinity cell-surface phosphate importer of Saccharomyces cerevisiae and a crucial element in the phosphate homeostatic system of this model yeast. We found that loss of Candida albicans Pho84 attenuated virulence in Drosophila and murine oropharyngeal and disseminated models of invasive infection, and conferred hypersensitivity to neutrophil killing. Susceptibility of cells lacking Pho84 to neutrophil attack depended on reactive oxygen species (ROS): pho84-/- cells were no more susceptible than wild type C. albicans to neutrophils from a patient with chronic granulomatous disease, or to those whose oxidative burst was pharmacologically inhibited or neutralized. pho84-/- mutants hyperactivated oxidative stress signalling. They accumulated intracellular ROS in the absence of extrinsic oxidative stress, in high as well as low ambient phosphate conditions. ROS accumulation correlated with diminished levels of the unique superoxide dismutase Sod3 in pho84-/- cells, while SOD3 overexpression from a conditional promoter substantially restored these cells' oxidative stress resistance in vitro. Repression of SOD3 expression sharply increased their oxidative stress hypersensitivity. Neither of these oxidative stress management effects of manipulating SOD3 transcription was observed in PHO84 wild type cells. Sod3 levels were not the only factor driving oxidative stress effects on pho84-/- cells, though, because overexpressing SOD3 did not ameliorate these cells' hypersensitivity to neutrophil killing ex vivo, indicating Pho84 has further roles in oxidative stress resistance and virulence. Measurement of cellular metal concentrations demonstrated that diminished Sod3 expression was not due to decreased import of its metal cofactor manganese, as predicted from the function of S. cerevisiae Pho84 as a low-affinity manganese transporter. Instead of a role of Pho84 in metal transport, we found its role in TORC1 activation to impact oxidative stress management: overexpression of the TORC1-activating GTPase Gtr1 relieved the Sod3 deficit and ROS excess in pho84-/- null mutant cells, though it did not suppress their hypersensitivity to neutrophil killing or hyphal growth defect. Pharmacologic inhibition of Pho84 by small molecules including the FDA-approved drug foscarnet also induced ROS accumulation. Inhibiting Pho84 could hence support host defenses by sensitizing C. albicans to oxidative stress.

  • 27. Loures, Flávio V
    et al.
    Röhm, Marc
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology.
    Lee, Chrono K
    Santos, Evelyn
    Wang, Jennifer P
    Specht, Charles A
    Calich, Vera L G
    Urban, Constantin F
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology.
    Levitz, Stuart M
    Recognition of Aspergillus fumigatus Hyphae by Human Plasmacytoid Dendritic Cells Is Mediated by Dectin-2 and Results in Formation of Extracellular Traps2015In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 11, no 2, article id e1004643Article in journal (Refereed)
    Abstract [en]

    Plasmacytoid dendritic cells (pDCs) were initially considered as critical for innate immunity to viruses. However, our group has shown that pDCs bind to and inhibit the growth of Aspergillus fumigatus hyphae and that depletion of pDCs renders mice hypersusceptible to experimental aspergillosis. In this study, we examined pDC receptors contributing to hyphal recognition and downstream events in pDCs stimulated by A. fumigatus hyphae. Our data show that Dectin-2, but not Dectin-1, participates in A. fumigatus hyphal recognition, TNF-α and IFN-α release, and antifungal activity. Moreover, Dectin-2 acts in cooperation with the FcRγ chain to trigger signaling responses. In addition, using confocal and electron microscopy we demonstrated that the interaction between pDCs and A. fumigatus induced the formation of pDC extracellular traps (pETs) containing DNA and citrullinated histone H3. These structures closely resembled those of neutrophil extracellular traps (NETs). The microarray analysis of the pDC transcriptome upon A. fumigatus infection also demonstrated up-regulated expression of genes associated with apoptosis as well as type I interferon-induced genes. Thus, human pDCs directly recognize A. fumigatus hyphae via Dectin-2; this interaction results in cytokine release and antifungal activity. Moreover, hyphal stimulation of pDCs triggers a distinct pattern of pDC gene expression and leads to pET formation.

  • 28. Maier, Lisa
    et al.
    Diard, Médéric
    Sellin, Mikael E
    Chouffane, Elsa-Sarah
    Trautwein-Weidner, Kerstin
    Periaswamy, Balamurugan
    Slack, Emma
    Dolowschiak, Tamas
    Stecher, Bärbel
    Loverdo, Claude
    Regoes, Roland R
    Hardt, Wolf-Dietrich
    Granulocytes impose a tight bottleneck upon the gut luminal pathogen population during Salmonella typhimurium colitis.2014In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 10, no 12Article in journal (Refereed)
    Abstract [en]

    Topological, chemical and immunological barriers are thought to limit infection by enteropathogenic bacteria. However, in many cases these barriers and their consequences for the infection process remain incompletely understood. Here, we employed a mouse model for Salmonella colitis and a mixed inoculum approach to identify barriers limiting the gut luminal pathogen population. Mice were infected via the oral route with wild type S. Typhimurium (S. Tm) and/or mixtures of phenotypically identical but differentially tagged S. Tm strains ("WITS", wild-type isogenic tagged strains), which can be individually tracked by quantitative real-time PCR. WITS dilution experiments identified a substantial loss in tag/genetic diversity within the gut luminal S. Tm population by days 2-4 post infection. The diversity-loss was not attributable to overgrowth by S. Tm mutants, but required inflammation, Gr-1+ cells (mainly neutrophilic granulocytes) and most likely NADPH-oxidase-mediated defense, but not iNOS. Mathematical modelling indicated that inflammation inflicts a bottleneck transiently restricting the gut luminal S. Tm population to approximately 6000 cells and plating experiments verified a transient, inflammation- and Gr-1+ cell-dependent dip in the gut luminal S. Tm population at day 2 post infection. We conclude that granulocytes, an important clinical hallmark of S. Tm-induced inflammation, impose a drastic bottleneck upon the pathogen population. This extends the current view of inflammation-fuelled gut-luminal Salmonella growth by establishing the host response in the intestinal lumen as a double-edged sword, fostering and diminishing colonization in a dynamic equilibrium. Our work identifies a potent immune defense against gut infection and reveals a potential Achilles' heel of the infection process which might be targeted for therapy.

  • 29.
    Mohan Kumar, Dipu
    et al.
    Ohio State University, Columbus, USA.
    Yamaguchi, Mamoru
    Ohio State University, Columbus, USA.
    Miura, Koshiro
    Ohio State University, Columbus, USA.
    Lin, Mingqun
    Ohio State University, Columbus, USA.
    Los, Marek
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Health Sciences.
    Coy, Johannes F.
    Vorstand/CSO TAVARLIN AG, Darmstadt, Germany .
    Rikihisa, Yasuko
    Ohio State University, Columbus, USA.
    Ehrlichia chaffeensis Uses Its Surface Protein EtpE to Bind GPI-Anchored Protein DNase X and Trigger Entry into Mammalian Cells2013In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 9, no 10, p. e1003666-Article in journal (Refereed)
    Abstract [en]

    Ehrlichia chaffeensis, an obligatory intracellular rickettsial pathogen, enters and replicates in monocytes/macrophages and several non-phagocytic cells. E. chaffeensis entry into mammalian cells is essential not only for causing the emerging zoonosis, human monocytic ehrlichiosis, but also for its survival. It remains unclear if E. chaffeensis has evolved a specific surface protein that functions as an 'invasin' to mediate its entry. We report a novel entry triggering protein of Ehrlichia, EtpE that functions as an invasin. EtpE is an outer membrane protein and an antibody against EtpE (the C-terminal fragment, EtpE-C) greatly inhibited E. chaffeensis binding, entry and infection of both phagocytes and non-phagocytes. EtpE-C-immunization of mice significantly inhibited E. chaffeensis infection. EtpE-C-coated latex beads, used to investigate whether EtpE-C can mediate cell invasion, entered both phagocytes and non-phagocytes and the entry was blocked by compounds that block E. chaffeensis entry. None of these compounds blocked uptake of non-coated beads by phagocytes. Yeast two-hybrid screening revealed that DNase X, a glycosylphosphatidyl inositol-anchored mammalian cell-surface protein binds EtpE-C. This was confirmed by far-Western blotting, affinity pull-down, co-immunoprecipitation, immunofluorescence labeling, and live-cell image analysis. EtpE-C-coated beads entered bone marrow-derived macrophages (BMDMs) from wild-type mice, whereas they neither bound nor entered BMDMs from DNase X-/- mice. Antibody against DNase X or DNase X knock-down by small interfering RNA impaired E. chaffeensis binding, entry, and infection. E. chaffeensis entry and infection rates of BMDMs from DNase X-/- mice and bacterial load in the peripheral blood in experimentally infected DNase X-/- mice, were significantly lower than those from wild-type mice. Thus this obligatory intracellular pathogen evolved a unique protein EtpE that binds DNase X to enter and infect eukaryotic cells. This study is the first to demonstrate the invasin and its mammalian receptor, and their in vivo relevance in any ehrlichial species.

  • 30.
    Mueller, Anna A.
    et al.
    Swiss Fed Inst Technol, Inst Microbiol, Zurich, Switzerland..
    Dolowschiak, Tamas
    Swiss Fed Inst Technol, Inst Microbiol, Zurich, Switzerland..
    Sellin, Mikael E.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Microbiology. Swiss Fed Inst Technol, Inst Microbiol, Zurich, Switzerland..
    Felmy, Boas
    Swiss Fed Inst Technol, Inst Microbiol, Zurich, Switzerland..
    Verbree, Carolin
    Swiss Fed Inst Technol, Inst Microbiol, Zurich, Switzerland..
    Gadient, Sandra
    Swiss Fed Inst Technol, Inst Microbiol, Zurich, Switzerland..
    Westermann, Alexander J.
    Univ Wurzburg, Inst Mol Infect Biol, Wurzburg, Germany..
    Vogel, Joerg
    Univ Wurzburg, Inst Mol Infect Biol, Wurzburg, Germany..
    LeibundGut-Landmann, Salome
    Univ Zurich, Inst Virol, Zurich, Switzerland..
    Hardt, Wolf-Dietrich
    Swiss Fed Inst Technol, Inst Microbiol, Zurich, Switzerland..
    An NK Cell Perforin Response Elicited via IL-18 Controls Mucosal Inflammation Kinetics during Salmonella Gut Infection2016In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 12, no 6, article id e1005723Article in journal (Refereed)
    Abstract [en]

    Salmonella Typhimurium (S. Tm) is a common cause of self-limiting diarrhea. The mucosal inflammation is thought to arise from a standoff between the pathogen's virulence factors and the host's mucosal innate immune defenses, particularly the mucosal NAIP/NLRC4 inflammasome. However, it had remained unclear how this switches the gut from homeostasis to inflammation. This was studied using the streptomycin mouse model. S. Tm infections in knockout mice, cytokine inhibition and -injection experiments revealed that caspase-1 (not -11) dependent IL-18 is pivotal for inducing acute inflammation. IL-18 boosted NK cell chemoattractants and enhanced the NK cells' migratory capacity, thus promoting mucosal accumulation of mature, activated NK cells. NK cell depletion and Prf(-/-) ablation (but not granulocyte-depletion or T-cell deficiency) delayed tissue inflammation. Our data suggest an NK cell perforin response as one limiting factor in mounting gut mucosal inflammation. Thus, IL-18-elicited NK cell perforin responses seem to be critical for coordinating mucosal inflammation during early infection, when S. Tm strongly relies on virulence factors detectable by the inflammasome. This may have broad relevance for mucosal defense against microbial pathogens.

  • 31.
    Nordgren, Johan
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Division of Microbiology and Molecular Medicine. Linköping University, Faculty of Medicine and Health Sciences.
    Sharma, Sumit
    Linköping University, Department of Clinical and Experimental Medicine, Division of Microbiology and Molecular Medicine. Linköping University, Faculty of Medicine and Health Sciences.
    Kambhampati, Anita
    Centre Disease Control and Prevent, USA.
    Lopman, Ben
    Centre Disease Control and Prevent, USA.
    Svensson, Lennart
    Linköping University, Department of Clinical and Experimental Medicine, Division of Microbiology and Molecular Medicine. Linköping University, Faculty of Medicine and Health Sciences.
    Innate Resistance and Susceptibility to Norovirus Infection2016In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 12, no 4, p. e1005385-Article in journal (Refereed)
    Abstract [en]

    n/a

  • 32. Papareddy, Praveen
    et al.
    Kalle, Martina
    Sorensen, Ole E.
    Malmsten, Martin
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Morgelin, Matthias
    Schmidtchen, Artur
    The TFPI-2 Derived Peptide EDC34 Improves Outcome of Gram-Negative Sepsis2013In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 9, no 12, p. e1003803-Article in journal (Refereed)
    Abstract [en]

    Sepsis is characterized by a dysregulated host-pathogen response, leading to high cytokine levels, excessive coagulation and failure to eradicate invasive bacteria. Novel therapeutic strategies that address crucial pathogenetic steps during infection are urgently needed. Here, we describe novel bioactive roles and therapeutic anti-infective potential of the peptide EDC34, derived from the C-terminus of tissue factor pathway inhibitor-2 (TFPI-2). This peptide exerted direct bactericidal effects and boosted activation of the classical complement pathway including formation of antimicrobial C3a, but inhibited bacteria-induced activation of the contact system. Correspondingly, in mouse models of severe Escherichia coli and Pseudomonas aeruginosa infection, treatment with EDC34 reduced bacterial levels and lung damage. In combination with the antibiotic ceftazidime, the peptide significantly prolonged survival and reduced mortality in mice. The peptide's boosting effect on bacterial clearance paired with its inhibiting effect on excessive coagulation makes it a promising therapeutic candidate for invasive Gram-negative infections.

  • 33. Parameswaran, Poornima
    et al.
    Sklan, Ella
    Wilkins, Courtney
    Burgon, Trever
    Samuel, Melanie A.
    Lu, Rui
    Ansel, K. Mark
    Heissmeyer, Vigo
    Einav, Shirit
    Jackson, William
    Doukas, Tammy
    Paranjape, Suman
    Polacek, Charlotta
    dos Santos, Flavia Barreto
    Jalili, Roxana
    Babrzadeh, Farbod
    Stanford Genome Technology Center, Stanford University School of Medicine, United States .
    Gharizadeh, Baback
    Grimm, Dirk
    Kay, Mark
    Koike, Satoshi
    Sarnow, Peter
    Ronaghi, Mostafa
    Ding, Shou-Wei
    Harris, Eva
    Chow, Marie
    Diamond, Michael S.
    Kirkegaard, Karla
    Glenn, Jeffrey S.
    Fire, Andrew Z.
    Six RNA Viruses and Forty-One Hosts: Viral Small RNAs and Modulation of Small RNA Repertoires in Vertebrate and Invertebrate Systems2010In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 6, no 2, p. e1000764-Article in journal (Refereed)
    Abstract [en]

    We have used multiplexed high-throughput sequencing to characterize changes in small RNA populations that occur during viral infection in animal cells. Small RNA-based mechanisms such as RNA interference (RNAi) have been shown in plant and invertebrate systems to play a key role in host responses to viral infection. Although homologs of the key RNAi effector pathways are present in mammalian cells, and can launch an RNAi-mediated degradation of experimentally targeted mRNAs, any role for such responses in mammalian host-virus interactions remains to be characterized. Six different viruses were examined in 41 experimentally susceptible and resistant host systems. We identified virus-derived small RNAs (vsRNAs) from all six viruses, with total abundance varying from "vanishingly rare'' (less than 0.1% of cellular small RNA) to highly abundant (comparable to abundant micro-RNAs "miRNAs''). In addition to the appearance of vsRNAs during infection, we saw a number of specific changes in host miRNA profiles. For several infection models investigated in more detail, the RNAi and Interferon pathways modulated the abundance of vsRNAs. We also found evidence for populations of vsRNAs that exist as duplexed siRNAs with zero to three nucleotide 39 overhangs. Using populations of cells carrying a Hepatitis C replicon, we observed strand-selective loading of siRNAs onto Argonaute complexes. These experiments define vsRNAs as one possible component of the interplay between animal viruses and their hosts.

  • 34.
    Raschig, Judith
    et al.
    Univ Hosp Tuebingen, Internal Med 1, Tubingen, Germany..
    Mailaender-Sanchez, Daniela
    Univ Hosp Tuebingen, Internal Med 1, Tubingen, Germany..
    Berscheid, Anne
    Univ Tubingen, Interfac Inst Microbiol & Infect Med, Dept Microbial Bioact Cpds, Tubingen, Germany..
    Berger, Juergen
    Max Planck Inst Dev Biol, Electron Microscopy, Tubingen, Germany..
    Strömstedt, Adam A.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Division of Pharmacognosy.
    Courth, Lioba F.
    Univ Hosp Tuebingen, Internal Med 1, Tubingen, Germany..
    Malek, Nisar P.
    Univ Hosp Tuebingen, Internal Med 1, Tubingen, Germany..
    Broetz-Oesterhelt, Heike
    Univ Tubingen, Interfac Inst Microbiol & Infect Med, Dept Microbial Bioact Cpds, Tubingen, Germany..
    Wehkamp, Jan
    Univ Hosp Tuebingen, Internal Med 1, Tubingen, Germany..
    Ubiquitously expressed Human Beta Defensin 1 (hBD1) forms bacteria-entrapping nets in a redox dependent mode of action2017In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 13, no 3, article id e1006261Article in journal (Refereed)
    Abstract [en]

    Ever since the discovery of endogenous host defense antimicrobial peptides it has been discussed how these evolutionary conserved molecules avoid to induce resistance and to remain effective. Human beta-defensin 1 (hBD1) is an ubiquitously expressed endogenous antimicrobial peptide that exhibits qualitatively distinct activities between its oxidized and reduced forms. Here, we explore these antimicrobial mechanisms. Surprisingly, using electron microscopy we detected a so far unknown net-like structure surrounding bacteria, which were treated with the reduced but not the oxidized form of hBD1. A transmigration assay demonstrated that hBD1-derived nets capture bacteria and inhibit bacterial transmigration independent of bacterial killing. The presence of nets could completely prevent migration of hBD1 resistant pathogens and are stable in the presence of human duodenal secretion with a high amount of proteases. In contrast to HD6, cysteins are necessary for net formation. This redox-dependent function serves as an additional mechanism of action for hBD1 and differs from net formation by other defensins such as Paneth cell-derived human alpha-defensin 6 (HD6). While hBD1red and hBD1ox have distinct antimicrobial profiles and functions, only the reduced form provides additional host protection by entrapping bacteria in extracellular net structures preventing bacterial invasion. Better understanding of the modes of action of endogenous host peptides will help to find new antimicrobial strategies.

  • 35. Rigard, Melanie
    et al.
    Bröms, Jeanette E.
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Clinical Bacteriology.
    Mosnier, Amandine
    Hologne, Maggy
    Martin, Amandine
    Lindgren, Lena
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Clinical Bacteriology.
    Punginelli, Claire
    Lays, Claire
    Walker, Olivier
    Charbit, Alain
    Telouk, Philippe
    Conlan, Wayne
    Terradot, Laurent
    Sjöstedt, Anders
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Clinical Bacteriology.
    Henry, Thomas
    Francisella tularensis IglG Belongs to a Novel Family of PAAR-Like T6SS Proteins and Harbors a Unique N-terminal Extension Required for Virulence2016In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 12, no 9, article id e1005821Article in journal (Refereed)
    Abstract [en]

    The virulence of Francisella tularensis, the etiological agent of tularemia, relies on an atypical type VI secretion system ( T6SS) encoded by a genomic island termed the Francisella Pathogenicity Island ( FPI). While the importance of the FPI in F. tularensis virulence is clearly established, the precise role of most of the FPI-encoded proteins remains to be deciphered. In this study, using highly virulent F. tularensis strains and the closely related species F. novicida, IglG was characterized as a protein featuring a unique alpha-helical N-terminal extension and a domain of unknown function ( DUF4280), present in more than 250 bacterial species. Three dimensional modeling of IglG and of the DUF4280 consensus protein sequence indicates that these proteins adopt a PAAR-like fold, suggesting they could cap the T6SS in a similar way as the recently described PAAR proteins. The newly identified PAAR-like motif is characterized by four conserved cysteine residues, also present in IglG, which may bind a metal atom. We demonstrate that IglG binds metal ions and that each individual cysteine is required for T6SS-dependent secretion of IglG and of the Hcp homologue, IglC and for the F. novicida intracellular life cycle. In contrast, the Francisella-specific N-terminal alpha-helical extension is not required for IglG secretion, but is critical for F. novicida virulence and for the interaction of IglG with another FPI-encoded protein, IglF. Altogether, our data suggest that IglG is a PAAR-like protein acting as a bi-modal protein that may connect the tip of the Francisella T6SS with a putative T6SS effector, IglF.

  • 36. Romilly, Cedric
    et al.
    Lays, Claire
    Tomasini, Arnaud
    Caldelari, Isabelle
    Benito, Yvonne
    Hammann, Philippe
    Geissmann, Thomas
    Boisset, Sandrine
    Romby, Pascale
    Vandenesch, Francois
    A Non-Coding RNA Promotes Bacterial Persistence and Decreases Virulence by Regulating a Regulator in Staphylococcus aureus2014In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 10, no 3, p. e1003979-Article in journal (Refereed)
    Abstract [en]

    Staphylococcus aureus produces a high number of RNAs for which the functions are poorly understood. Several non-coding RNAs carry a C-rich sequence suggesting that they regulate mRNAs at the post-transcriptional level. We demonstrate that the Sigma B-dependent RsaA RNA represses the synthesis of the global transcriptional regulator MgrA by forming an imperfect duplex with the Shine and Dalgarno sequence and a loop-loop interaction within the coding region of the target mRNA. These two recognition sites are required for translation repression. Consequently, RsaA causes enhanced production of biofilm and a decreased synthesis of capsule formation in several strain backgrounds. These phenotypes led to a decreased protection of S. aureus against opsonophagocytic killing by polymorphonuclear leukocytes compared to the mutant strains lacking RsaA. Mice animal models showed that RsaA attenuates the severity of acute systemic infections and enhances chronic catheter infection. RsaA takes part in a regulatory network that contributes to the complex interactions of S. aureus with the host immune system to moderate invasiveness and favour chronic infections. It is the first example of a conserved small RNA in S. aureus functioning as a virulence suppressor of acute infections. Because S. aureus is essentially a human commensal, we propose that RsaA has been positively selected through evolution to support commensalism and saprophytic interactions with the host.

  • 37. Sahu, Sanjaya Kumar
    et al.
    Kumar, Manish
    Chakraborty, Sohini
    Banerjee, Srijon Kaushik
    Kumar, Ranjeet
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Department of Chemistry, Bose Institute, Kolkata, India.
    Gupta, Pushpa
    Jana, Kuladip
    Gupta, Umesh D.
    Ghosh, Zhumur
    Kundu, Manikuntala
    Basu, Joyoti
    MicroRNA 26a (miR-26a)/KLF4 and CREB-C/EBP beta regulate innate immune signaling, the polarization of macrophages and the trafficking of Mycobacterium tuberculosis to lysosomes during infection2017In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 13, no 5, article id e1006410Article in journal (Refereed)
    Abstract [en]

    For efficient clearance of Mycobacterium tuberculosis (Mtb), macrophages tilt towards M1 polarization leading to the activation of transcription factors associated with the production of antibacterial effector molecules such as nitric oxide (NO) and proinflammatory cytokines such as interleukin 1 beta (IL-1 beta) and tumor necrosis factor alpha (TNF-alpha). At the same time, resolution of inflammation is associated with M2 polarization with increased production of arginase and cytokines such as IL-10. The transcriptional and post-transcriptional mechanisms that govern the balance between M1 and M2 polarization, and bacteria-containing processes such as autophagy and trafficking of Mtb to lysosomes, are incompletely understood. Here we report for the first time, that the transcription factor KLF4 is targeted by microRNA-26a (miR-26a). During Mtb infection, downregulation of miR-26a (observed both ex vivo and in vivo) facilitates upregulation of KLF4 which in turn favors increased arginase and decreased iNOS activity. We further demonstrate that KLF4 prevents trafficking of Mtb to lysosomes. The CREB-C/EBP beta signaling axis also favors M2 polarization. Downregulation of miR-26a and upregulation of C/ebpbeta were observed both in infected macrophages as well as in infected mice. Knockdown of C/ebpbeta repressed the expression of selected M2 markers such as Il10 and Irf4 in infected macrophages. The importance of these pathways is substantiated by observations that expression of miR-26a mimic or knockdown of Klf4 or Creb or C/ebpbeta, attenuated the survival of Mtb in macrophages. Taken together, our results attribute crucial roles for the miR-26a/KLF4 and CREB-C/EBP beta signaling pathways in regulating the survival of Mtb in macrophages. These studies expand our understanding of how Mtb hijacks host signaling pathways to survive in macrophages, and open up new exploratory avenues for host-targeted interventions.

  • 38. Scholz, Saskia
    et al.
    Baharom, Faezzah
    Rankin, Gregory
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Maleki, Kimia T.
    Gupta, Shawon
    Vangeti, Sindhu
    Pourazar, Jamshid
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Discacciati, Andrea
    Höijer, Jonas
    Bottai, Matteo
    Björkström, Niklas K.
    Rasmuson, Johan
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Infectious Diseases.
    Evander, Magnus
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Virology.
    Blomberg, Anders
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Ljunggren, Hans-Gustaf
    Klingström, Jonas
    Ahlm, Clas
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Infectious Diseases.
    Smed-Sörensen, Anna
    Human hantavirus infection elicits pronounced redistribution of mononuclear phagocytes in peripheral blood and airways2017In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 13, no 6, article id e1006462Article in journal (Refereed)
    Abstract [en]

    Hantaviruses infect humans via inhalation of virus-contaminated rodent excreta. Infection can cause severe disease with up to 40% mortality depending on the viral strain. The virus primarily targets the vascular endothelium without direct cytopathic effects. Instead, exaggerated immune responses may inadvertently contribute to disease development. Mononuclear phagocytes (MNPs), including monocytes and dendritic cells (DCs), orchestrate the adaptive immune responses. Since hantaviruses are transmitted via inhalation, studying immunological events in the airways is of importance to understand the processes leading to immunopathogenesis. Here, we studied 17 patients infected with Puumala virus that causes a mild form of hemorrhagic fever with renal syndrome (HFRS). Bronchial biopsies as well as longitudinal blood draws were obtained from the patients. During the acute stage of disease, a significant influx of MNPs expressing HLA-DR, CD11c or CD123 was detected in the patients' bronchial tissue. In parallel, absolute numbers of MNPs were dramatically reduced in peripheral blood, coinciding with viremia. Expression of CCR7 on the remaining MNPs in blood suggested migration to peripheral and/or lymphoid tissues. Numbers of MNPs in blood subsequently normalized during the convalescent phase of the disease when viral RNA was no longer detectable in plasma. Finally, we exposed blood MNPs in vitro to Puumala virus, and demonstrated an induction of CCR7 expression on MNPs. In conclusion, the present study shows a marked redistribution of blood MNPs to the airways during acute hantavirus disease, a process that may underlie the local immune activation and contribute to immunopathogenesis in hantavirus-infected patients.

  • 39.
    Seper, Andrea
    et al.
    Institute of Molecular Biosciences, University of Graz, Graz, Austria.
    Hosseinzadeh, Ava
    Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Gorkiewicz, Gregor
    University of Graz, Graz, Austria.
    Lichtenegger, Sabine
    University of Graz, Graz, Austria.
    Roier, Sandro
    University of Graz, Graz, Austria.
    Leitner, Deborah R
    University of Graz, Graz, Austria.
    Röhm, Marc
    Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Department of Clinical Microbiology.
    Grutsch, Andreas
    Institute of Molecular Biosciences, University of Graz, Graz, Austria.
    Reidl, Joachim
    University of Graz, Graz, Austria.
    Urban, Constantin F
    Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Department of Clinical Microbiology.
    Schild, Stefan
    Institute of Molecular Biosciences, University of Graz, Graz, Austria.
    Vibrio cholerae evades neutrophil extracellular traps by the activity of two extracellular nucleases2013In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 9, no 9, article id e1003614Article in journal (Refereed)
    Abstract [en]

    The Gram negative bacterium Vibrio cholerae is the causative agent of the secretory diarrheal disease cholera, which has traditionally been classified as a noninflammatory disease. However, several recent reports suggest that a V. cholerae infection induces an inflammatory response in the gastrointestinal tract indicated by recruitment of innate immune cells and increase of inflammatory cytokines. In this study, we describe a colonization defect of a double extracellular nuclease V. cholerae mutant in immunocompetent mice, which is not evident in neutropenic mice. Intrigued by this observation, we investigated the impact of neutrophils, as a central part of the innate immune system, on the pathogen V. cholerae in more detail. Our results demonstrate that V. cholerae induces formation of neutrophil extracellular traps (NETs) upon contact with neutrophils, while V. cholerae in return induces the two extracellular nucleases upon presence of NETs. We show that the V. cholerae wild type rapidly degrades the DNA component of the NETs by the combined activity of the two extracellular nucleases Dns and Xds. In contrast, NETs exhibit prolonged stability in presence of the double nuclease mutant. Finally, we demonstrate that Dns and Xds mediate evasion of V. cholerae from NETs and lower the susceptibility for extracellular killing in the presence of NETs. This report provides a first comprehensive characterization of the interplay between neutrophils and V. cholerae along with new evidence that the innate immune response impacts the colonization of V. cholerae in vivo. A limitation of this study is an inability for technical and physiological reasons to visualize intact NETs in the intestinal lumen of infected mice, but we can hypothesize that extracellular nuclease production by V. cholerae may enhance survival fitness of the pathogen through NET degradation.

  • 40.
    Sigurlásdóttir, Sara
    et al.
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Engman, Jakob
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Eriksson, Olaspers Sara
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Saroj, Sunil D.
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Zguna, Nadezda
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Lloris-Garcerá, Pilar
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Jonsson, Ann-Beth
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Host cell-derived lactate functions as an effector molecule in Neisseria meningitidis microcolony dispersal2017In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 13, no 4, article id e1006251Article in journal (Refereed)
    Abstract [en]

    The development of meningococcal disease, caused by the human pathogen Neisseria meningitidis, is preceded by the colonization of the epithelial layer in the nasopharynx. After initial adhesion to host cells meningococci form aggregates, through pilus-pilus interactions, termed microcolonies from which the bacteria later detach. Dispersal from microcolonies enables access to new colonization sites and facilitates the crossing of the cell barrier; however, this process is poorly understood. In this study, we used live-cell imaging to investigate the process of N. meningitidis microcolony dispersal. We show that direct contact with host cells is not required for microcolony dispersal, instead accumulation of a host-derived effector molecule induces microcolony dispersal. By using a host-cell free approach, we demonstrated that lactate, secreted from host cells, initiate rapid dispersal of microcolonies. Interestingly, metabolic utilization of lactate by the bacteria was not required for induction of dispersal, suggesting that lactate plays a role as a signaling molecule. Furthermore, Neisseria gonorrhoeae microcolony dispersal could also be induced by lactate. These findings reveal a role of host-secreted lactate in microcolony dispersal and virulence of pathogenic Neisseria.

  • 41. Simon, Sylvia
    et al.
    Schell, Ursula
    Heuer, Natalie
    Hager, Dominik
    Albers, Michael F
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Matthias, Jan
    Fahrnbauer, Felix
    Trauner, Dirk
    Eichinger, Ludwig
    Hedberg, Christian
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Department of Chemical Biology, Max-Planck-Institute of Molecular Physiology, Dortmund, Germany.
    Hilbi, Hubert
    Inter-kingdom Signaling by the Legionella Quorum Sensing Molecule LAI-1 Modulates Cell Migration through an IQGAP1-Cdc42-ARHGEF9-Dependent Pathway2015In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 11, no 12, article id e1005307Article in journal (Refereed)
    Abstract [en]

    Small molecule signaling promotes the communication between bacteria as well as between bacteria and eukaryotes. The opportunistic pathogenic bacterium Legionella pneumophila employs LAI-1 (3-hydroxypentadecane-4-one) for bacterial cell-cell communication. LAI-1 is produced and detected by the Lqs (Legionella quorum sensing) system, which regulates a variety of processes including natural competence for DNA uptake and pathogen-host cell interactions. In this study, we analyze the role of LAI-1 in inter-kingdom signaling. L. pneumophila lacking the autoinducer synthase LqsA no longer impeded the migration of infected cells, and the defect was complemented by plasmid-borne lqsA. Synthetic LAI-1 dose-dependently inhibited cell migration, without affecting bacterial uptake or cytotoxicity. The forward migration index but not the velocity of LAI-1-treated cells was reduced, and the cell cytoskeleton appeared destabilized. LAI-1-dependent inhibition of cell migration involved the scaffold protein IQGAP1, the small GTPase Cdc42 as well as the Cdc42-specific guanine nucleotide exchange factor ARHGEF9, but not other modulators of Cdc42, or RhoA, Rac1 or Ran GTPase. Upon treatment with LAI-1, Cdc42 was inactivated and IQGAP1 redistributed to the cell cortex regardless of whether Cdc42 was present or not. Furthermore, LAI-1 reversed the inhibition of cell migration by L. pneumophila, suggesting that the compound and the bacteria antagonistically target host signaling pathway(s). Collectively, the results indicate that the L. pneumophila quorum sensing compound LAI-1 modulates migration of eukaryotic cells through a signaling pathway involving IQGAP1, Cdc42 and ARHGEF9.

  • 42.
    Urban, Constantin F
    et al.
    Department for Cellular Microbiology, Max Planck Institute for Infection Biology, Berlin, Germany.
    Ermert, David
    Schmid, Monika
    Abu-Abed, Ulrike
    Goosmann, Christian
    Nacken, Wolfgang
    Brinkmann, Volker
    Jungblut, Peter R
    Zychlinsky, Arturo
    Neutrophil extracellular traps contain calprotectin, a cytosolic protein complex involved in host defense against Candida albicans2009In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 5, no 10, article id e1000639Article in journal (Refereed)
    Abstract [en]

    Neutrophils are the first line of defense at the site of an infection. They encounter and kill microbes intracellularly upon phagocytosis or extracellularly by degranulation of antimicrobial proteins and the release of Neutrophil Extracellular Traps (NETs). NETs were shown to ensnare and kill microbes. However, their complete protein composition and the antimicrobial mechanism are not well understood. Using a proteomic approach, we identified 24 NET-associated proteins. Quantitative analysis of these proteins and high resolution electron microscopy showed that NETs consist of modified nucleosomes and a stringent selection of other proteins. In contrast to previous results, we found several NET proteins that are cytoplasmic in unstimulated neutrophils. We demonstrated that of those proteins, the antimicrobial heterodimer calprotectin is released in NETs as the major antifungal component. Absence of calprotectin in NETs resulted in complete loss of antifungal activity in vitro. Analysis of three different Candida albicans in vivo infection models indicated that NET formation is a hitherto unrecognized route of calprotectin release. By comparing wild-type and calprotectin-deficient animals we found that calprotectin is crucial for the clearance of infection. Taken together, the present investigations confirmed the antifungal activity of calprotectin in vitro and, moreover, demonstrated that it contributes to effective host defense against C. albicans in vivo. We showed for the first time that a proportion of calprotectin is bound to NETs in vitro and in vivo.

  • 43. van Mierlo, Joël T
    et al.
    Bronkhorst, Alfred W
    Overheul, Gijs J
    Sadanandan, Sajna A
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Ekström, Jens-Ola
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Heestermans, Marco
    Hultmark, Dan
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Institute of Biomedical Technology, University of Tampere, Tampere, Finland.
    Antoniewski, Christophe
    van Rij, Ronald P
    Convergent evolution of argonaute-2 slicer antagonism in two distinct insect RNA viruses2012In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 8, no 8, article id e1002872Article in journal (Refereed)
    Abstract [en]

    RNA interference (RNAi) is a major antiviral pathway that shapes evolution of RNA viruses. We show here that Nora virus, a natural Drosophila pathogen, is both a target and suppressor of RNAi. We detected viral small RNAs with a signature of Dicer-2 dependent small interfering RNAs in Nora virus infected Drosophila. Furthermore, we demonstrate that the Nora virus VP1 protein contains RNAi suppressive activity in vitro and in vivo that enhances pathogenicity of recombinant Sindbis virus in an RNAi dependent manner. Nora virus VP1 and the viral suppressor of RNAi of Cricket paralysis virus (1A) antagonized Argonaute-2 (AGO2) Slicer activity of RNA induced silencing complexes pre-loaded with a methylated single-stranded guide strand. The convergent evolution of AGO2 suppression in two unrelated insect RNA viruses highlights the importance of AGO2 in antiviral defense.

  • 44. Vanha-aho, Leena-Maija
    et al.
    Anderl, Ines
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Laboratory of Genetic Immunology, BioMediTech, University of Tampere, Tampere, Finland.
    Vesala, Laura
    Hultmark, Dan
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Laboratory of Genetic Immunology, BioMediTech, University of Tampere, Tampere, Finland.
    Valanne, Susanna
    Rämet, Mika
    Edin expression in the fat body is required in the defense against parasitic wasps in Drosophila melanogaster2015In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 11, no 5, article id e1004895Article in journal (Refereed)
    Abstract [en]

    The cellular immune response against parasitoid wasps in Drosophila involves the activation, mobilization, proliferation and differentiation of different blood cell types. Here, we have assessed the role of Edin (elevated during infection) in the immune response against the parasitoid wasp Leptopilina boulardi in Drosophila melanogaster larvae. The expression of edin was induced within hours after a wasp infection in larval fat bodies. Using tissue-specific RNAi, we show that Edin is an important determinant of the encapsulation response. Although edin expression in the fat body was required for the larvae to mount a normal encapsulation response, it was dispensable in hemocytes. Edin expression in the fat body was not required for lamellocyte differentiation, but it was needed for the increase in plasmatocyte numbers and for the release of sessile hemocytes into the hemolymph. We conclude that edin expression in the fat body affects the outcome of a wasp infection by regulating the increase of plasmatocyte numbers and the mobilization of sessile hemocytes in Drosophila larvae.

  • 45. Vieyres, Gabrielle
    et al.
    Welsch, Kathrin
    Gerold, Gisa
    Institute of Experimental Virology, TWINCORE, Centre for Experimental and Clinical Infection Research; a joint venture between the Medical School Hannover (MHH) and the Helmholtz Centre for Infection Research (HZI), Hannover, Germany.
    Gentzsch, Juliane
    Kahl, Sina
    Vondran, Florian W R
    Kaderali, Lars
    Pietschmann, Thomas
    ABHD5/CGI-58, the Chanarin-Dorfman Syndrome Protein, Mobilises Lipid Stores for Hepatitis C Virus Production2016In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 12, no 4, article id e1005568Article in journal (Refereed)
    Abstract [en]

    Hepatitis C virus (HCV) particles closely mimic human very-low-density lipoproteins (VLDL) to evade humoral immunity and to facilitate cell entry. However, the principles that govern HCV association with VLDL components are poorly defined. Using an siRNA screen, we identified ABHD5 (α/β hydrolase domain containing protein 5, also known as CGI-58) as a new host factor promoting both virus assembly and release. ABHD5 associated with lipid droplets and triggered their hydrolysis. Importantly, ABHD5 Chanarin-Dorfman syndrome mutants responsible for a rare lipid storage disorder in humans were mislocalised, and unable to consume lipid droplets or support HCV production. Additional ABHD5 mutagenesis revealed a novel tribasic motif that does not influence subcellular localization but determines both ABHD5 lipolytic and proviral properties. These results indicate that HCV taps into the lipid droplet triglyceride reservoir usurping ABHD5 lipase cofactor function. They also suggest that the resulting lipid flux, normally devoted to VLDL synthesis, also participates in the assembly and release of the HCV lipo-viro-particle. Altogether, our study provides the first association between the Chanarin-Dorfman syndrome protein and an infectious disease and sheds light on the hepatic manifestations of this rare genetic disorder as well as on HCV morphogenesis.

  • 46. Wallet, Pierre
    et al.
    Benaoudia, Sacha
    Mosnier, Amandine
    Lagrange, Brice
    Martin, Amandine
    Lindgren, Helena
    Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Department of Clinical Microbiology.
    Golovliov, Igor
    Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Department of Clinical Microbiology.
    Michal, Fanny
    Basso, Pauline
    Djebali, Sophia
    Provost, Angelina
    Allatif, Omran
    Meunier, Etienne
    Broz, Petr
    Yamamoto, Masahiro
    Py, Benedicte F.
    Faudry, Eric
    Sjöstedt, Anders
    Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Department of Clinical Microbiology.
    Henry, Thomas
    IFN-gamma extends the immune functions of Guanylate Binding Proteins to inflammasome-independent antibacterial activities during Francisella novicida infection2017In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 13, no 10, article id e1006630Article in journal (Refereed)
    Abstract [en]

    Guanylate binding proteins (GBPs) are interferon-inducible proteins involved in the cellintrinsic immunity against numerous intracellular pathogens. The molecular mechanisms underlying the potent antibacterial activity of GBPs are still unclear. GBPs have been functionally linked to the NLRP3, the AIM2 and the caspase-11 inflammasomes. Two opposing models are currently proposed to explain the GBPs-inflammasome link: i) GBPs would target intracellular bacteria or bacteria-containing vacuoles to increase cytosolic PAMPs release ii) GBPs would directly facilitate inflammasome complex assembly. Using Francisella novicida infection, we investigated the functional interactions between GBPs and the inflammasome. GBPs, induced in a type I IFN-dependent manner, are required for the F. novicida-mediated AIM2-inflammasome pathway. Here, we demonstrate that GBPs action is not restricted to the AIM2 inflammasome, but controls in a hierarchical manner the activation of different inflammasomes complexes and apoptotic caspases. IFN-gamma induces a quantitative switch in GBPs levels and redirects pyroptotic and apoptotic pathways under the control of GBPs. Furthermore, upon IFN-gamma priming, F. novicida-infected macrophages restrict cytosolic bacterial replication in a GBP-dependent and inflammasome-independent manner. Finally, in a mouse model of tularemia, we demonstrate that the inflammasome and the GBPs are two key immune pathways functioning largely independently to control F. novicida infection. Altogether, our results indicate that GBPs are the master effectors of IFN-gamma-mediated responses against F. novicida to control antibacterial immune responses in inflammasome-dependent and independent manners.

  • 47. Watthanasurorot, Apiruck
    et al.
    Jiravanichpaisal, Pikul
    Liu, Haipeng
    Söderhäll, I
    Söderhäll, K
    Bacteria-Induced Dscam Isoforms of the Crustacean, Pacifastacus leniusculus2011In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 7, no 6, article id e1002062Article in journal (Refereed)
    Abstract [en]

    The Down syndrome cell adhesion molecule, also known as Dscam, is a member of the immunoglobulin super family. Dscam plays an essential function in neuronal wiring and appears to be involved in innate immune reactions in insects. The deduced amino acid sequence of Dscam in the crustacean Pacifastacus leniusculus (PlDscam), encodes 9(Ig)-4(FNIII)-(Ig)-2(FNIII)-TM and it has variable regions in the N-terminal half of Ig2 and Ig3 and the complete Ig7 and in the transmembrane domain. The cytoplasmic tail can generate multiple isoforms. PlDscam can generate more than 22,000 different unique isoforms. Bacteria and LPS injection enhanced the expression of PlDscam, but no response in expression occurred after a white spot syndrome virus (WSSV) infection or injection with peptidoglycans. Furthermore, PlDscam silencing did not have any effect on the replication of the WSSV. Bacterial specific isoforms of PlDscam were shown to have a specific binding property to each tested bacteria, E. coli or S. aureus. The bacteria specific isoforms of PlDscam were shown to be associated with bacterial clearance and phagocytosis in crayfish.

  • 48. Webster, Steve J.
    et al.
    Brode, Sven
    Ellis, Lou
    Fitzmaurice, Timothy J.
    Elder, Matthew J.
    Gekara, Nelson O.
    Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Tourlomousis, Panagiotis
    Bryant, Clare
    Clare, Simon
    Chee, Ronnie
    Gaston, Hill J. S.
    Goodall, Jane C.
    Detection of a microbial metabolite by STING regulates inflammasome activation in response to Chlamydia trachomatis infection2017In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 13, no 6, article id e1006383Article in journal (Refereed)
    Abstract [en]

    The innate immune system is a critical component of host defence against microbial pathogens, but effective responses require an ability to distinguish between infectious and noninfectious insult to prevent inappropriate inflammation. Using the important obligate intracellular human pathogen Chlamydia trachomatis; an organism that causes significant immunopathology, we sought to determine critical host and pathogen factors that contribute to the induction of inflammasome activation. We assayed inflammasome activation by immunoblotting and ELISA to detect IL-1 beta processing and LDH release to determine pyroptosis. Using primary murine bone marrow derived macrophages or human monocyte derived dendritic cells, infected with live or attenuated Chlamydia trachomatis we report that the live organism activates both canonical and non-canonical inflammasomes, but only canonical inflammasomes controlled IL-1 beta processing which preceded pyroptosis. NADPH oxidase deficient macrophages were permissive to Chlamydia trachomatis replication and displayed elevated type-1 interferon and inflammasome activation. Conversely, attenuated, non-replicating Chlamydia trachomatis, primed but did not activate inflammasomes and stimulated reduced type-1 interferon responses. This suggested bacterial replication or metabolism as important factors that determine interferon responses and inflammasome activation. We identified STING but not cGAS as a central mediator of interferon regulated inflammasome activation. Interestingly, exogenous delivery of a Chlamydia trachomatis metabolite and STING ligand D cyclic di-AMP, recovered inflammasome activation to attenuated bacteria in a STING dependent manner thus indicating that a bacterial metabolite is a key factor initiating inflammasome activation through STING, independent of cGAS. These data suggest a potential mechanism of how the innate immune system can distinguish between infectious and non-infectious insult and instigate appropriate immune responses that could be therapeutically targeted.

  • 49. Zocher, Georg
    et al.
    Mistry, Nitesh
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Virology.
    Frank, Martin
    Hähnlein-Schick, Irmgard
    Ekström, Jens-Ola
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Arnberg, Niklas
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Virology. Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    Stehle, Thilo
    A sialic acid binding site in a human picornavirus2014In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 10, no 10, p. e1004401-Article in journal (Refereed)
    Abstract [en]

    The picornaviruses coxsackievirus A24 variant (CVA24v) and enterovirus 70 (EV70) cause continued outbreaks and pandemics of acute hemorrhagic conjunctivitis (AHC), a highly contagious eye disease against which neither vaccines nor antiviral drugs are currently available. Moreover, these viruses can cause symptoms in the cornea, upper respiratory tract, and neurological impairments such as acute flaccid paralysis. EV70 and CVA24v are both known to use 5-N-acetylneuraminic acid (Neu5Ac) for cell attachment, thus providing a putative link between the glycan receptor specificity and cell tropism and disease. We report the structures of an intact human picornavirus in complex with a range of glycans terminating in Neu5Ac. We determined the structure of the CVA24v to 1.40 angstrom resolution, screened different glycans bearing Neu5Ac for CVA24v binding, and structurally characterized interactions with candidate glycan receptors. Biochemical studies verified the relevance of the binding site and demonstrated a preference of CVA24v for alpha 2,6-linked glycans. This preference can be rationalized by molecular dynamics simulations that show that alpha 2,6-linked glycans can establish more contacts with the viral capsid. Our results form an excellent platform for the design of antiviral compounds to prevent AHC.

  • 50.
    Åberg, Anna
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Gideonsson, Pär
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Vallström, Anna
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Olofsson, Annelie
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Öhman, Carina
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Rakhimova, Lena
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Borén, Thomas
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Engstrand, Lars
    Brännström, Kristoffer
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Arnqvist, Anna
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    A Repetitive DNA Element Regulates Expression of the Helicobacter pylori Sialic Acid Binding Adhesin by a Rheostat-like Mechanism2014In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 10, no 7, article id e1004234Article in journal (Refereed)
    Abstract [en]

    During persistent infection, optimal expression of bacterial factors is required to match the ever-changing host environment. The gastric pathogen Helicobacter pylori has a large set of simple sequence repeats (SSR), which constitute contingency loci. Through a slipped strand mispairing mechanism, the SSRs generate heterogeneous populations that facilitate adaptation. Here, we present a model that explains, in molecular terms, how an intergenically located T-tract, via slipped strand mispairing, operates with a rheostat-like function, to fine-tune activity of the promoter that drives expression of the sialic acid binding adhesin, SabA. Using T-tract variants, in an isogenic strain background, we show that the length of the T-tract generates multiphasic output from the sabA promoter. Consequently, this alters the H. pylori binding to sialyl-Lewis x receptors on gastric mucosa. Fragment length analysis of post-infection isolated clones shows that the T-tract length is a highly variable feature in H. pylori. This mirrors the host-pathogen interplay, where the bacterium generates a set of clones from which the best-fit phenotypes are selected in the host. In silico and functional in vitro analyzes revealed that the length of the T-tract affects the local DNA structure and thereby binding of the RNA polymerase, through shifting of the axial alignment between the core promoter and UP-like elements. We identified additional genes in H. pylori, with T- or A-tracts positioned similar to that of sabA, and show that variations in the tract length likewise acted as rheostats to modulate cognate promoter output. Thus, we propose that this generally applicable mechanism, mediated by promoter-proximal SSRs, provides an alternative mechanism for transcriptional regulation in bacteria, such as H. pylori, which possesses a limited repertoire of classical trans-acting regulatory factors.

1 - 50 of 50
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf