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Solute Carriers in Metabolism: Regulation of known and putative solute carriers in the central nervous system
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Functional Pharmacology. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Description
Abstract [en]

Solute carriers (SLCs) are membrane-bound transporter proteins, important for nutrient, ion, drug and metabolite transport across membranes. A quarter of the human genome codes for membrane-bound proteins, and SLCs make up the largest group of transporter proteins. Due to their ability to transport a large repertoire of substances across, not just the plasma membrane, but also the membrane of internal organelles, they hold a key position in maintaining homeostasis affecting metabolic pathways. Unfortunately, some of the more than 400 identified SLCs are still not fully characterized, even though a quarter of these are associated with human disease. In addition, there are about 30 membrane-bound proteins with strong resemblance to SLCs, of which very little is known. The aim of this thesis is to characterize some of these putative SLCs, focusing on their localization and function in the central nervous system. Since many of the known SLCs play a vital part in metabolism and related pathways, the response to different nutritional conditions has been used as a key method. MFSD14A and MFSD14B, characterized in Paper I, are putative SLCs belonging to the Major Facilitator Superfamily (MFS) and found to be neuronal, differentially expressed in the mouse central nervous system and transiently upregulated in mouse embryonic cortex cultures due to amino acid deprivation. They were also altered in areas of the mouse brain after starvation as well as after high fat diet. In Paper II, the effect on gene regulation due to complete amino acid starvation was monitored in a mouse hypothalamic cell line and 47 different genes belonging to SLCs, or putative SLCs, were found to be affected. Of these, 15 genes belonged to already known amino acid transporters, whereas 32 were putative SLCs with no known function or SLCs not known to react to amino acids. The three SV2 proteins, SV2A, SV2B and SV2C, were studied in Paper III using human neuroblastoma cell lines. The high metabolic state of cancers often result in an upregulation and alteration of transporter proteins, and alterations of the SV2 proteins were found following different treatments performed in this study. Paper IV focused on putative SLCs of MFS type and their role in glucose metabolism. Mouse embryonic cortex cultures were subjected to glucose starvation and the gene expression of 19 putative transporters were analyzed. All but four of the putative transporters were affected either at 3h or 12h of glucose deprivation. In conclusion, several SLCs and putative SLCs studied in this thesis are strongly affected by alteration in metabolism, either due to amino acids or glucose or both. This makes the putative SLCs dynamic membrane-bound proteins, possibly transporters, highly affected by nutritional status and most likely regulated to maintain homeostasis.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. , 44 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1380
Keyword [en]
Solute Carriers, transporter, amino acid starvation, glucose metabolism, MFS, SV2
National Category
Basic Medicine Biochemistry and Molecular Biology Cell Biology
Research subject
Medical Science
Identifiers
URN: urn:nbn:se:uu:diva-331328ISBN: 978-91-513-0104-4 (print)OAI: oai:DiVA.org:uu-331328DiVA: diva2:1148930
Public defence
2017-11-30, B21, Biomedicinskt Centrum (BMC), Husargatan 3, Uppsala, 09:30 (English)
Opponent
Supervisors
Available from: 2017-11-07 Created: 2017-10-12 Last updated: 2017-11-07
List of papers
1. Putative Membrane-Bound Transporters MFSD14A and MFSD14B Are Neuronal and Affected by Nutrient Availability
Open this publication in new window or tab >>Putative Membrane-Bound Transporters MFSD14A and MFSD14B Are Neuronal and Affected by Nutrient Availability
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2017 (English)In: Frontiers in Molecular Neuroscience, ISSN 1662-5099, Vol. 10, 11Article in journal (Refereed) Published
Abstract [en]

Characterization of orphan transporters is of importance due to their involvement in cellular homeostasis but also in pharmacokinetics and pharmacodynamics. The tissue and cellular localization, as well as function, is still unknown for many of the solute carriers belonging to the major facilitator superfamily (MFS) Pfam clan. Here, we have characterized two putative novel transporters MFSD14A (HIAT1) and MFSD14B (HIATL1) in the mouse central nervous system and found protein staining throughout the adult mouse brain. Both transporters localized to neurons and MFSD14A co-localized with the Golgi marker Giantin in primary embryonic cortex cultures, while MFSD14B staining co-localized with an endoplasmic retention marker, KDEL. Based on phylogenetic clustering analyses, we predict both to have organic substrate profiles, and possible involvement in energy homeostasis. Therefore, we monitored gene regulation changes in mouse embryonic primary cultures after amino acid starvations and found both transporters to be upregulated after 3 h of starvation. Interestingly, in mice subjected to 24 h of food starvation, both transporters were downregulated in the hypothalamus, while Mfsdl4a was also downregulated in the brainstem. In addition, in mice fed a high fat diet (HFD), upregulation of both transporters was seen in the striatum. Both MFSD14A and MFSD14B were intracellular neuronal membrane bound proteins, expressed in the Golgi and Endoplasmic reticulum, affected by both starvation and HFD to varying degree in the mouse brain.

Keyword
MFSD14A, HIAT1, MFSD14B, HIATL1, SLC, MFSD, transporter protein
National Category
Neurology
Identifiers
urn:nbn:se:uu:diva-316413 (URN)10.3389/fnmol.2017.00011 (DOI)000392751300001 ()28179877 (PubMedID)
Funder
Swedish Research CouncilThe Swedish Brain FoundationSwedish Society for Medical Research (SSMF)Novo NordiskMagnus Bergvall Foundation
Available from: 2017-03-02 Created: 2017-03-02 Last updated: 2017-10-12Bibliographically approved
2. The gene expression of numerous SLC transporters isaltered in the immortalized hypothalamic cell line N25/2following amino acid starvation
Open this publication in new window or tab >>The gene expression of numerous SLC transporters isaltered in the immortalized hypothalamic cell line N25/2following amino acid starvation
2017 (English)In: FEBS Open Bio, E-ISSN 2211-5463, Vol. 7, no 2, 249-264 p.Article in journal (Refereed) Published
Abstract [en]

Amino acids are known to play a key role in gene expression regulation,and in mammalian cells, amino acid signaling is mainly mediated via twopathways, the mammalian target of rapamycin complex 1 (mTORC1) pathwayand the amino acid responsive (AAR) pathway. It is vital for cells tohave a system to sense amino acid levels, in order to control protein andamino acid synthesis and catabolism. Amino acid transporters are crucialin these pathways, due to both their sensing and transport functions. Inthis large-scale study, an immortalized mouse hypothalamic cell line (N25/2)was used to study the gene expression changes following 1, 2, 3, 5 or 16 hof amino acid starvation. We focused on genes encoding solute carriers(SLCs) and putative SLCs, more specifically on amino acid transporters.The microarray contained 28 270 genes and 86.2% of the genes wereexpressed in the cell line. At 5 h of starvation, 1001 genes were upregulatedand 848 genes were downregulated, and among these, 47 genes from theSLC superfamily or atypical SLCs were found. Of these, 15 were genesencoding amino acid transporters and 32 were genes encoding other SLCsor atypical SLCs. Increased expression was detected for genes encodingamino acid transporters from system A, ASC, L, N, T, xc-, and y+. UsingGO annotations, genes involved in amino acid transport and amino acidtransmembrane transporter activity were found to be most upregulated at3 h and 5 h of starvation.

National Category
Cell Biology
Identifiers
urn:nbn:se:uu:diva-331260 (URN)10.1002/2211-5463.12181 (DOI)
Funder
Swedish Research Council
Available from: 2017-10-12 Created: 2017-10-12 Last updated: 2017-10-18Bibliographically approved
3. Treatment of two human neuroblastoma cell lines with growth factors, ATRA or VIP alters synaptic vesicle glycoprotein 2 (SV2) expression.
Open this publication in new window or tab >>Treatment of two human neuroblastoma cell lines with growth factors, ATRA or VIP alters synaptic vesicle glycoprotein 2 (SV2) expression.
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(English)Manuscript (preprint) (Other academic)
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:uu:diva-331276 (URN)
Available from: 2017-10-12 Created: 2017-10-12 Last updated: 2017-10-12
4. Glucose deprived mouse embryonal cortex cultures respond by altering MFS transporter expression and localization
Open this publication in new window or tab >>Glucose deprived mouse embryonal cortex cultures respond by altering MFS transporter expression and localization
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(English)Manuscript (preprint) (Other academic)
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:uu:diva-331327 (URN)
Available from: 2017-10-12 Created: 2017-10-12 Last updated: 2017-10-12

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