Receptor for activated C kinase-1 facilitates protein kinase C-dependent phosphorylation and functional modulation of GABA(A) receptors with the activation of G-protein-coupled receptors.
GABA(A) receptors are the principal sites of fast synaptic inhibition in the brain. These receptors are hetero-pentamers that can be assembled from a number of subunit classes: alpha(1-6), beta(1-3), gamma(1-3), delta(1), epsilon, theta;, and pi, but the majority of receptor subtypes is believed, however, to be composed of alpha, beta, and gamma2 subunits. A major mechanism for modulating GABA(A) receptor function occurs via the phosphorylation of residues within the intracellular domains of receptor subunits by a range of serine/threonine and tyrosine kinases. However, how protein kinases are targeted to these receptors to facilitate functional modulation remains unknown. Here we demonstrate that the receptor for activated C kinase (RACK-1) and protein kinase C (PKC) bind to distinct sites on GABA(A) receptor beta subunits. Although RACK-1 is not essential for PKC binding to GABA(A) receptor beta subunits, it enhances the phosphorylation of serine 409, a residue critical for the phospho-dependent modulation of GABA(A) receptor function in the beta1 subunit by anchored PKC. Furthermore, RACK-1 also enhances GABA(A) receptor functional modulation in neurons by a PKC-dependent signaling pathway with the activation of muscarinic acetylcholine receptors (mAChRs). This PKC-dependent modulation of neuronal GABA(A) receptors was mirrored by an increase in the phosphorylation of GABA(A) receptor beta subunits with the activation of mAChRs. Our results suggest a central role for RACK-1 in potentiating PKC-dependent phosphorylation and functional modulation of GABA(A) receptors. Therefore, RACK-1 will enhance functional cross talk between GABA(A) receptors and G-protein-coupled receptors and therefore may have profound effects on neuronal excitability.
Brandon
Nicholas J
NJ
Medical Research Council, Laboratory of Molecular Cell Biology and Department of Pharmacology, University College London, London WC1E 6BT, United Kingdom.
Jovanovic
Jasmina N
JN
Smart
Trevor G
TG
Moss
Stephen J
SJ
D000818:Animals; D001665:Binding Sites / Q000502:physiology; D002478:Cells, Cultured; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D007668:Kidney / Q000166:cytology / Q000378:metabolism; D046911:Macromolecular Substances; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding / Q000502:physiology; D011493:Protein Kinase C / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000502:physiology; D021122:Protein Subunits; D051381:Rats; D017207:Rats, Sprague-Dawley; D020239:Receptor Cross-Talk / Q000502:physiology; D000075370:Receptors for Activated C Kinase; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011963:Receptors, GABA-A / Q000378:metabolism; D011976:Receptors, Muscarinic / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology
D007527:Isoenzymes; D046911:Macromolecular Substances; D021122:Protein Subunits; D000075370:Receptors for Activated C Kinase; D011956:Receptors, Cell Surface; D011963:Receptors, GABA-A; D011976:Receptors, Muscarinic; D011493:Protein Kinase C; D019204:GTP-Binding Proteins