title: Regulation of glutamate transporter GLT-1 by MAGI-1.
abstract: The sodium-dependent glutamate transporter, glutamate transporter subtype 1 (GLT-1) is one of the main glutamate transporters in the brain. GLT-1 contains a COOH-terminal sequence similar to one in an isoform of Slo1 K(+) channel protein previously shown to bind MAGI-1 (membrane-associated guanylate kinase with inverted orientation protein-1). MAGI-1 is a scaffold protein which allows the formation of complexes between certain transmembrane proteins, actin-binding proteins, and other regulatory proteins. The glutathione S-transferase pull-down assay demonstrated that MAGI-1 was a binding partner of GLT-1. The interaction between MAGI-1 and GLT-1 was confirmed by co-immunoprecipitation. Immunofluorescence of MAGI-1 and GLT-1 demonstrated that the distribution of MAGI-1 and GLT-1 overlapped in astrocytes. Co-expression of MAGI-1 with GLT-1 in C6 Glioma cells resulted in a significant reduction in the surface expression of GLT-1, as assessed by cell-surface biotinylation. On the other hand, partial knockdown of endogenous MAGI-1 expression by small interfering RNA in differentiated cultured astrocytes increased glutamate uptake and the surface expression of endogenous GLT-1. Knockdown of MAGI-1 increased dihydrokainate-sensitive, Na(+) -dependent glutamate uptake, indicating that MAGI-1 regulates GLT-1 mediated glutamate uptake. These data suggest that MAGI-1 regulates surface expression of GLT-1 and the level of glutamate in the hippocampus.
authors.affiliation: Department of Biology and Biochemistry, University of Houston, Houston, TX 77204, USA.
authors.forename: Shengwei
authors.initials: S
authors.lastname: Zou
authors.forename: Juan D
authors.initials: JD
authors.lastname: Pita-Almenar
authors.forename: Arnold
authors.initials: A
authors.lastname: Eskin
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000378:metabolism; D019921:Biotinylation; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D027341:Excitatory Amino Acid Transporter 1 / Q000096:biosynthesis* / Q000235:genetics; D050580:Excitatory Amino Acid Transporter 3 / Q000096:biosynthesis / Q000235:genetics; D005455:Fluorescent Antibody Technique; D005786:Gene Expression Regulation; D005910:Glioma / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D051528:Guanylate Kinases / Q000096:biosynthesis* / Q000235:genetics; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism; D047468:Immunoprecipitation; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / Q000096:biosynthesis / Q000235:genetics; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000235:genetics; D010957:Plasmids / Q000235:genetics; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000737:chemistry; D014162:Transfection
chemical_list: D027341:Excitatory Amino Acid Transporter 1; D050580:Excitatory Amino Acid Transporter 3; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D008565:Membrane Proteins; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; C493398:Slc1a1 protein, rat; C493392:Slc1a3 protein, rat; D018698:Glutamic Acid; D005982:Glutathione Transferase; D051528:Guanylate Kinases; C508141:Magi1 protein, rat