Glutamine Uptake via SNAT6 and Caveolin Regulates Glutamine–Glutamate Cycle
SLC38A6 (SNAT6) is the only known member of the SLC38 family that is expressed exclusively in the excitatory neurons of the brain. It has been described as an orphan transporter with an unknown substrate profile, therefore very little is known about SNAT6. In this study, we addressed the substrate s...
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| Format: | Article |
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MDPI AG
2021-01-01
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| Series: | International Journal of Molecular Sciences |
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| Online Access: | https://www.mdpi.com/1422-0067/22/3/1167 |
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| author | Nikhil R. Gandasi Vasiliki Arapi Michel E. Mickael Prajakta A. Belekar Louise Granlund Lakshmi Kothegala Robert Fredriksson Sonchita Bagchi |
| author_facet | Nikhil R. Gandasi Vasiliki Arapi Michel E. Mickael Prajakta A. Belekar Louise Granlund Lakshmi Kothegala Robert Fredriksson Sonchita Bagchi |
| author_sort | Nikhil R. Gandasi |
| collection | DOAJ |
| description | SLC38A6 (SNAT6) is the only known member of the SLC38 family that is expressed exclusively in the excitatory neurons of the brain. It has been described as an orphan transporter with an unknown substrate profile, therefore very little is known about SNAT6. In this study, we addressed the substrate specificity, mechanisms for internalization of SNAT6, and the regulatory role of SNAT6 with specific insights into the glutamate–glutamine cycle. We used tritium-labeled amino acids in order to demonstrate that SNAT6 is functioning as a glutamine and glutamate transporter. SNAT6 revealed seven predicted transmembrane segments in a homology model and was localized to caveolin rich sites at the plasma membrane. SNAT6 has high degree of specificity for glutamine and glutamate. Presence of these substrates enables formation of SNAT6-caveolin complexes that aids in sodium dependent trafficking of SNAT6 off the plasma membrane. To further understand its mode of action, several potential interacting partners of SNAT6 were identified using bioinformatics. Among them where CTP synthase 2 (CTPs2), phosphate activated glutaminase (Pag), and glutamate metabotropic receptor 2 (Grm2). Co-expression analysis, immunolabeling with co-localization analysis and proximity ligation assays of these three proteins with SNAT6 were performed to investigate possible interactions. SNAT6 can cycle between cytoplasm and plasma membrane depending on availability of substrates and interact with Pag, synaptophysin, CTPs2, and Grm2. Our data suggest a potential role of SNAT6 in glutamine uptake at the pre-synaptic terminal of excitatory neurons. We propose here a mechanistic model of SNAT6 trafficking that once internalized influences the glutamate–glutamine cycle in presence of its potential interacting partners. |
| first_indexed | 2024-03-09T03:46:49Z |
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| issn | 1661-6596 1422-0067 |
| language | English |
| last_indexed | 2024-03-09T03:46:49Z |
| publishDate | 2021-01-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | International Journal of Molecular Sciences |
| spelling | doaj.art-cfc4cad12c0e4d9c956c5079351988d52023-12-03T14:34:13ZengMDPI AGInternational Journal of Molecular Sciences1661-65961422-00672021-01-01223116710.3390/ijms22031167Glutamine Uptake via SNAT6 and Caveolin Regulates Glutamine–Glutamate CycleNikhil R. Gandasi0Vasiliki Arapi1Michel E. Mickael2Prajakta A. Belekar3Louise Granlund4Lakshmi Kothegala5Robert Fredriksson6Sonchita Bagchi7Department of Metabolic Physiology, Institute of Neuroscience and Physiology, University of Göteborg, Box 430, SE-405 30 Göteborg, SwedenDepartment of Pharmaceutical Biosciences, Molecular Neuropharmacology, Uppsala University, SE-751 23 Uppsala, SwedenDepartment of Neuroscience, Functional Pharmacology, Uppsala University, SE-751 23 Uppsala, SwedenDepartment of Metabolic Physiology, Institute of Neuroscience and Physiology, University of Göteborg, Box 430, SE-405 30 Göteborg, SwedenDepartment of Pharmaceutical Biosciences, Molecular Neuropharmacology, Uppsala University, SE-751 23 Uppsala, SwedenDepartment of Metabolic Physiology, Institute of Neuroscience and Physiology, University of Göteborg, Box 430, SE-405 30 Göteborg, SwedenDepartment of Pharmaceutical Biosciences, Molecular Neuropharmacology, Uppsala University, SE-751 23 Uppsala, SwedenDepartment of Pharmaceutical Biosciences, Molecular Neuropharmacology, Uppsala University, SE-751 23 Uppsala, SwedenSLC38A6 (SNAT6) is the only known member of the SLC38 family that is expressed exclusively in the excitatory neurons of the brain. It has been described as an orphan transporter with an unknown substrate profile, therefore very little is known about SNAT6. In this study, we addressed the substrate specificity, mechanisms for internalization of SNAT6, and the regulatory role of SNAT6 with specific insights into the glutamate–glutamine cycle. We used tritium-labeled amino acids in order to demonstrate that SNAT6 is functioning as a glutamine and glutamate transporter. SNAT6 revealed seven predicted transmembrane segments in a homology model and was localized to caveolin rich sites at the plasma membrane. SNAT6 has high degree of specificity for glutamine and glutamate. Presence of these substrates enables formation of SNAT6-caveolin complexes that aids in sodium dependent trafficking of SNAT6 off the plasma membrane. To further understand its mode of action, several potential interacting partners of SNAT6 were identified using bioinformatics. Among them where CTP synthase 2 (CTPs2), phosphate activated glutaminase (Pag), and glutamate metabotropic receptor 2 (Grm2). Co-expression analysis, immunolabeling with co-localization analysis and proximity ligation assays of these three proteins with SNAT6 were performed to investigate possible interactions. SNAT6 can cycle between cytoplasm and plasma membrane depending on availability of substrates and interact with Pag, synaptophysin, CTPs2, and Grm2. Our data suggest a potential role of SNAT6 in glutamine uptake at the pre-synaptic terminal of excitatory neurons. We propose here a mechanistic model of SNAT6 trafficking that once internalized influences the glutamate–glutamine cycle in presence of its potential interacting partners.https://www.mdpi.com/1422-0067/22/3/1167solute carrier proteinsSNAT6pre-synaptic terminalexcitatory neuronsglutamate–glutamine cyclecaveolin |
| spellingShingle | Nikhil R. Gandasi Vasiliki Arapi Michel E. Mickael Prajakta A. Belekar Louise Granlund Lakshmi Kothegala Robert Fredriksson Sonchita Bagchi Glutamine Uptake via SNAT6 and Caveolin Regulates Glutamine–Glutamate Cycle International Journal of Molecular Sciences solute carrier proteins SNAT6 pre-synaptic terminal excitatory neurons glutamate–glutamine cycle caveolin |
| title | Glutamine Uptake via SNAT6 and Caveolin Regulates Glutamine–Glutamate Cycle |
| title_full | Glutamine Uptake via SNAT6 and Caveolin Regulates Glutamine–Glutamate Cycle |
| title_fullStr | Glutamine Uptake via SNAT6 and Caveolin Regulates Glutamine–Glutamate Cycle |
| title_full_unstemmed | Glutamine Uptake via SNAT6 and Caveolin Regulates Glutamine–Glutamate Cycle |
| title_short | Glutamine Uptake via SNAT6 and Caveolin Regulates Glutamine–Glutamate Cycle |
| title_sort | glutamine uptake via snat6 and caveolin regulates glutamine glutamate cycle |
| topic | solute carrier proteins SNAT6 pre-synaptic terminal excitatory neurons glutamate–glutamine cycle caveolin |
| url | https://www.mdpi.com/1422-0067/22/3/1167 |
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