Regulation of postsynaptic gephyrin cluster size by protein phosphatase 1.
The scaffolding protein gephyrin is essential for the clustering of glycine and GABA(A) receptors (GABA(A)Rs) at inhibitory synapses. Here, we provide evidence that the size of the postsynaptic gephyrin scaffold is controlled by dephosphorylation reactions. Treatment of cultured hippocampal neurons with the protein phosphatase inhibitors calyculin A and okadaic acid reduced the size of postsynaptic gephyrin clusters and increased cytoplasmic gephyrin staining. Protein phosphatase 1 (PP1) was found to colocalize with gephyrin at selected postsynaptic sites and to interact with gephyrin in transfected cells and brain extracts. Alanine or glutamate substitution of the two established serine/threonine phosphorylation sites in gephyrin failed to affect its clustering at inhibitory synapses and its ability to recruit gamma2 subunit containing GABA(A)Rs. Our data are consistent with the postsynaptic gephyrin scaffold acting as a platform for PP1, which regulates gephyrin cluster size by dephosphorylation of gephyrin- or cytoskeleton-associated proteins.
Bausen
Melanie
M
Department of Neurochemistry, Max-Planck Institute for Brain Research, 60529 Frankfurt/Main, Germany.
Weltzien
Felix
F
Betz
Heinrich
H
O'Sullivan
Gregory A
GA
D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000378:metabolism / Q000648:ultrastructure; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology; D006801:Humans; D008387:Marine Toxins; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D019319:Okadaic Acid / Q000494:pharmacology; D010080:Oxazoles / Q000494:pharmacology; D054645:Protein Phosphatase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D018079:Receptors, GABA / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013569:Synapses / Q000187:drug effects / Q000378:metabolism*
D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D008387:Marine Toxins; D008565:Membrane Proteins; D010080:Oxazoles; D018079:Receptors, GABA; D011993:Recombinant Fusion Proteins; C073441:gephyrin; D019319:Okadaic Acid; C059041:calyculin A; D054645:Protein Phosphatase 1