title: Multiple G protein-coupled receptors initiate protein kinase C redistribution of GABA transporters in hippocampal neurons.
abstract: Neurotransmitter transporters function in synaptic signaling in part through the sequestration and removal of neurotransmitter from the synaptic cleft. A recurring theme of transporters is that many can be functionally regulated by protein kinase C (PKC); some of this regulation occurs via a redistribution of the transporter protein between the plasma membrane and the cytoplasm. The endogenous triggers that lead to PKC-mediated transporter redistribution have not been elucidated. G-protein-coupled receptors that activate PKC are likely candidates to initiate transporter redistribution. We tested this hypothesis by examining the rat brain GABA transporter GAT1 endogenously expressed in hippocampal neurons. Specific agonists of G-protein-coupled acetylcholine, glutamate, and serotonin receptors downregulate GAT1 function. This functional inhibition is dose-dependent, mimicked by PKC activators, and prevented by specific receptor antagonists and PKC inhibitors. Surface biotinylation experiments show that the receptor-mediated functional inhibition correlates with a redistribution of GAT1 from the plasma membrane to intracellular locations. These data demonstrate (1) that endogenous GAT1 function can be regulated by PKC via subcellular redistribution, and (2) that signaling via several different G-protein-coupled receptors can mediate this effect. These results raise the possibility that some effects of G-protein-mediated alterations in synaptic signaling might occur through changes in the number of transporters expressed on the plasma membrane and subsequent effects on synaptic neurotransmitter levels.
authors.affiliation: Department of Neurobiology and The Medical Scientist Training Program, University of Alabama at Birmingham, Birmingham, Alabama 35294-0021, USA.
authors.forename: M L
authors.initials: ML
authors.lastname: Beckman
authors.forename: E M
authors.initials: EM
authors.lastname: Bernstein
authors.forename: M W
authors.initials: MW
authors.lastname: Quick
mesh_terms: D000818:Animals; D001692:Biological Transport; D019921:Biotinylation; D015153:Blotting, Western; D002352:Carrier Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D015536:Down-Regulation; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D050485:GABA Plasma Membrane Transport Proteins; D019204:GTP-Binding Proteins / Q000502:physiology*; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism*; D007424:Intracellular Fluid / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D026901:Membrane Transport Proteins; D009474:Neurons / Q000378:metabolism / Q000648:ultrastructure; D027361:Organic Anion Transporters; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D017470:Receptors, Glutamate / Q000187:drug effects / Q000502:physiology; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000502:physiology; D017981:Receptors, Neurotransmitter / Q000187:drug effects / Q000502:physiology*; D011985:Receptors, Serotonin / Q000187:drug effects / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D050485:GABA Plasma Membrane Transport Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D027361:Organic Anion Transporters; D017470:Receptors, Glutamate; D011976:Receptors, Muscarinic; D017981:Receptors, Neurotransmitter; D011985:Receptors, Serotonin; C493415:Slc6a1 protein, rat; D005680:gamma-Aminobutyric Acid; D011493:Protein Kinase C; D019204:GTP-Binding Proteins