title: Physical and functional interactions between the serotonin transporter and the neutral amino acid transporter ASCT2.
abstract: The activity of serotonergic systems depends on the reuptake of extracellular serotonin via its plasma membrane serotonin [5-HT (5-hydroxytryptamine)] transporter (SERT), a member of the Na(+)/Cl(-)-dependent solute carrier 6 family. SERT is finely regulated by multiple molecular mechanisms including its physical interaction with intracellular proteins. The majority of previously identified SERT partners that control its functional activity are soluble proteins, which bind to its intracellular domains. SERT also interacts with transmembrane proteins, but its association with other plasma membrane transporters remains to be established. Using a proteomics strategy, we show that SERT associates with ASCT2 (alanine-serine-cysteine-threonine 2), a member of the solute carrier 1 family co-expressed with SERT in serotonergic neurons and involved in the transport of small neutral amino acids across the plasma membrane. Co-expression of ASCT2 with SERT in HEK (human embryonic kidney)-293 cells affects glycosylation and cell-surface localization of SERT with a concomitant reduction in its 5-HT uptake activity. Conversely, depletion of cellular ASCT2 by RNAi enhances 5-HT uptake in both HEK-293 cells and primary cultured mesencephalon neurons. Mimicking the effect of ASCT2 down-regulation, treatment of HEK-293 cells and neurons with the ASCT2 inhibitor D-threonine also increases 5-HT uptake. Moreover, D-threonine does not enhance further the maximal velocity of 5-HT uptake in cells depleted of ASCT2. Collectively, these findings provide evidence for a complex assembly involving SERT and a member of another solute carrier family, which strongly influences the subcellular distribution of SERT and the reuptake of 5-HT.
authors.affiliation: CNRS, UMR-5203, Institut de Génomique Fonctionnelle, F-34094 Montpellier, France INSERM, U661, F-34094 Montpellier, France Université de Montpellier, F-34094 Montpellier, France.
authors.forename: Pascal
authors.initials: P
authors.lastname: Seyer
authors.affiliation: CNRS, UMR-5203, Institut de Génomique Fonctionnelle, F-34094 Montpellier, France INSERM, U661, F-34094 Montpellier, France Université de Montpellier, F-34094 Montpellier, France.
authors.forename: Franck
authors.initials: F
authors.lastname: Vandermoere
authors.affiliation: CNRS, UMR-5203, Institut de Génomique Fonctionnelle, F-34094 Montpellier, France INSERM, U661, F-34094 Montpellier, France Université de Montpellier, F-34094 Montpellier, France.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Cassier
authors.affiliation: CNRS, UMR-5203, Institut de Génomique Fonctionnelle, F-34094 Montpellier, France INSERM, U661, F-34094 Montpellier, France Université de Montpellier, F-34094 Montpellier, France.
authors.forename: Joël
authors.initials: J
authors.lastname: Bockaert
authors.affiliation: CNRS, UMR-5203, Institut de Génomique Fonctionnelle, F-34094 Montpellier, France INSERM, U661, F-34094 Montpellier, France Université de Montpellier, F-34094 Montpellier, France philippe.marin@igf.cnrs.fr.
authors.forename: Philippe
authors.initials: P
authors.lastname: Marin
mesh_terms: D026962:Amino Acid Transport System ASC / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects / Q000235:genetics; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D015778:Minor Histocompatibility Antigens / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D011485:Protein Binding; D034622:RNA Interference; D012701:Serotonin / Q000378:metabolism*; D050486:Serotonin Plasma Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D013912:Threonine / Q000494:pharmacology
chemical_list: D026962:Amino Acid Transport System ASC; D015778:Minor Histocompatibility Antigens; C420506:SLC1A5 protein, human; C493230:SLC6A4 protein, human; D050486:Serotonin Plasma Membrane Transport Proteins; C498850:Slc1a5 protein, mouse; C493231:Slc6a4 protein, mouse; D013912:Threonine; D012701:Serotonin
keywords: 5-hydroxytryptamine; ASCT2; SERT-interacting protein; glycosylation; neuron; solute carrier