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Alpha-actinin - an amazing journey through time and species
Umeå University, Faculty of Science and Technology, Department of Chemistry. (Lars Backman)
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In eukaryotes, the actin cytoskeleton plays an important role in a large variety of cellular events. Its reorganization is regulated by a plethora of actin-modulating proteins, such as α-actinin.

α-actinin is a ubiquitous actin-binding protein that belongs to the spectrin superfamily. This family, besides α-actinin, includes spectrin, dystrophin and utrophin. Phylogenetic analyses have indicated that the family members arose after several intragene duplications and rearrangements of a common ancestral α-actinin isoform. Up to the invertebrate-vertebrate bifurcation, organisms seemed to have a single, calcium-dependent α‑actinin. After the split, invertebrates have kept this single isoform, in contrast to vertebrates that acquired four distinct isoforms. Of the four vertebrate α-actinin isoforms, the two present in non-muscle cells are typically calcium sensitive while the two muscle isoforms are calcium insensitive.

α-actinin in higher organisms is characterized by the presence of three distinct structural domains: a highly conserved N-terminal actin-binding domain, a central rod domain with four spectrin repeats and a calcium-binding C terminus with EF-hand motifs. In some primitive organisms, such as protozoa and fungi, the rod domain of α-actinin contains only one or two spectrin repeats. With the completion of an ever increasing number of genomes, new and atypical α‑actinin sequences had been available that have not been characterized yet. To obtain a firmer understanding of the evolutionary history of α-actinin, the main objective of this study was to identify, purify and biochemically characterize atypical α‑actinin or α‑actinin-like proteins of the parasite Entamoeba histolytica and of the fungus Schizosaccharomyces pombe. Our results show that both isoforms, despite the much shorter rod domain, are able to bind and cross-link actin filaments and therefore can be considered genuine α-actinins. 

Place, publisher, year, edition, pages
Umeå: Kemiska institutionen, Umeå Universitet , 2011. , 48 p.
URN: urn:nbn:se:umu:diva-44074ISBN: 978-91-7459-205-4 (print)OAI: diva2:417908
Public defence
2011-06-10, KBC huset, KB3A9, Umeå Universitet, Umeå, 10:00 (English)
Available from: 2011-05-20 Created: 2011-05-18 Last updated: 2011-05-20Bibliographically approved
List of papers
1. Characterization of Entamoeba histolytica α-actinin2
Open this publication in new window or tab >>Characterization of Entamoeba histolytica α-actinin2
2007 (English)In: Molecular and Biochemical Parasitology, Vol. 154, 82-89 p.Article in journal (Refereed) Published
Abstract [en]

We have cloned and characterized a second α-actinin isoform in Entamoeba histolytica. This protein, α-actinin2, has a N-terminal actin-binding domain, a C-terminal calcium-binding domain and an intervening rod domain containing two spectrin repeats. The protein binds and cross-links actin filaments in a calcium-dependent manner. Therefore α-actinin2 is a genuine α-actinin except for the shorter rod domain compared to the rod domain of isoforms of higher organisms.

A α-actinin-like protein has previous been implicated in the adherence to the host cell and infection. It is therefore possible that α-actinin2 is involved in mechanism of infection, and in particular in reorganisation of the parasite's cytoskeleton that follows on adherence.

E. histolytica α-actinin2 represents one of the first members of the spectrin superfamily where well defined spectrin repeats are found. The isolation and characterization of this second α-actinin isoform is valuable not only into the study of E. histolytica infection mechanisms, but also for understanding the evolution processes of the spectrin superfamily.

α-Actinin, Entamoeba histolytica, Actin
urn:nbn:se:umu:diva-16098 (URN)10.1016/j.molbiopara.2007.04.010 (DOI)
Available from: 2007-08-17 Created: 2007-08-17 Last updated: 2011-05-20Bibliographically approved
2. The domain structure of Entamoeba α-actinin2
Open this publication in new window or tab >>The domain structure of Entamoeba α-actinin2
2010 (English)In: Cellular & Molecular Biology Letters (Druk), ISSN 1425-8153, E-ISSN 1689-1392, Vol. 15, no 4, 665-78 p.Article in journal (Refereed) Published
Abstract [en]

Entamoeba histolytica, a major agent of human amoebiasis, expresses two distinct forms of α-actinin, a ubiquitous actin-binding protein that is present in most eukaryotic organisms. In contrast to all metazoan α-actinins, in both isoforms the intervening rod domain that connects the N-terminal actin-binding domain with the C-terminal EF-hands is much shorter. It is suggested that these α-actinins may be involved in amoeboid motility and phagocytosis, so we cloned and characterised each domain of one of these α-actinins to better understand their functional role. The results clearly showed that the domains have properties very similar to those of conventional α-actinins.

Place, publisher, year, edition, pages
Springer, 2010
α-actinin, Spectrin repeat, Actin-binding protein
urn:nbn:se:umu:diva-36544 (URN)10.2478/s11658-010-0035-z (DOI)000282175000011 ()20865366 (PubMedID)
Available from: 2010-10-04 Created: 2010-10-04 Last updated: 2011-05-20Bibliographically approved

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