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The Journal of Neuroscience, 1999:RC9:1-6
RAPID COMMUNICATION
Multiple G Protein-Coupled Receptors Initiate Protein Kinase C
Redistribution of GABA Transporters in Hippocampal Neurons
Matthew L.
Beckman1, 2,
Eve M.
Bernstein1, and
Michael W.
Quick1
1 Department of Neurobiology and 2 The
Medical Scientist Training Program, University of Alabama at
Birmingham, Birmingham, Alabama 35294-0021
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.
Key words:
biotinylation; GAT1; hippocampus; neurotransmitter
uptake; protein trafficking; seven-helix receptor
Copyright © 1999 Society for Neuroscience 0270-6474/99/$05.00/0
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