Identification of the sites for CaMK-II-dependent phosphorylation of GABA(A) receptors

Phosphorylation can affect both the function and trafficking of GABA(A) receptors with significant consequences for neuronal excitability. Serine/threonine kinases can phosphorylate the intracellular loops between M3-4 of GABA(A) receptor beta and gamma subunits thereby modulating receptor function...

Full description

Saved in:

Bibliographic Details
Published in:	The Journal of biological chemistry 2007-06, Vol.282 (24), p.17855-17865
Main Authors:	Houston, Catriona M, Lee, Henry H C, Hosie, Alastair M, Moss, Stephen J, Smart, Trevor G
Format:	Article
Language:	eng
Subjects:	Animals Calcium-Calmodulin-Dependent Protein Kinase Type 2 Calcium-Calmodulin-Dependent Protein Kinases - genetics Calcium-Calmodulin-Dependent Protein Kinases - metabolism Cells, Cultured Cerebellum - cytology Enzyme Activation Humans Mice Patch-Clamp Techniques Phosphorylation Protein Subunits - genetics Protein Subunits - metabolism Protein-Tyrosine Kinases - metabolism Rats Rats, Sprague-Dawley Receptors, GABA-A - genetics Receptors, GABA-A - metabolism Recombinant Fusion Proteins - genetics Recombinant Fusion Proteins - metabolism Serine - metabolism Tyrosine - metabolism
Online Access:	Get full text
Tags:	Add Tag No Tags, Be the first to tag this record!

Description
Summary:	Phosphorylation can affect both the function and trafficking of GABA(A) receptors with significant consequences for neuronal excitability. Serine/threonine kinases can phosphorylate the intracellular loops between M3-4 of GABA(A) receptor beta and gamma subunits thereby modulating receptor function in heterologous expression systems and in neurons (1, 2). Specifically, CaMK-II has been demonstrated to phosphorylate the M3-4 loop of GABA(A) receptor subunits expressed as GST fusion proteins (3, 4). It also increases the amplitude of GABA(A) receptor-mediated currents in a number of neuronal cell types (5-7). To identify which substrate sites CaMK-II might phosphorylate and the consequent functional effects, we expressed recombinant GABA(A) receptors in NG108-15 cells, which have previously been shown to support CaMK-II modulation of GABA(A) receptors containing the beta3 subunit (8). We now demonstrate that CaMK-II mediates its effects on alpha1beta3 receptors via phosphorylation of Ser(383) within the M3-4 domain of the beta subunit. Ablation of beta3 subunit phosphorylation sites for CaMK-II revealed that for alphabetagamma receptors, CaMK-II has a residual effect on GABA currents that is not mediated by previously identified sites of CaMK-II phosphorylation. This residual effect is abolished by mutation of tyrosine phosphorylation sites, Tyr(365) and Tyr(367), on the gamma2S subunit, and by the tyrosine kinase inhibitor genistein. These results suggested that CaMK-II is capable of directly phosphorylating GABA(A) receptors and activating endogenous tyrosine kinases to phosphorylate the gamma2 subunit in NG108-15 cells. These findings were confirmed in a neuronal environment by expressing recombinant GABA(A) receptors in cerebellar granule neurons.
ISSN:	0021-9258 1083-351X