Calcium/calmodulin-dependent kinase II phosphorylation of the GABAA receptor α1 subunit modulates benzodiazepine binding

gamma-Aminobutyric acid (GABA) is the primary neurotransmitter that is responsible for the fast inhibitory synaptic transmission in the central nervous system. A major post-translational mechanism that can rapidly regulate GABA(A) R function is receptor phosphorylation. This study was designed to test the effect of endogenous calcium and calmodulin-dependent kinase II (CaM kinase II) activation on both allosteric modulator binding and GABA(A) receptor subunit phosphorylation. Endogenous CaM kinase II activity was stimulated, and GABA(A) receptors were subsequently analyzed for bothallosteric modulator binding properties and immunoprecipitated and analyzed for subunit phosphorylation levels. A significant increase in allosteric-modulator binding of the GABA(A) R was observed under conditions maximal for CaM kinase II activation. In addition, CaM kinase II activation resulted in a direct increase in phosphorylation of the GABA(A) receptor alpha1 subunit. The data suggest that the CaM kinase II-dependent phosphorylation of the GABA(A) receptor alpha1 subunit modulated allosteric modulator binding to the GABA(A) receptor.