Calcium/calmodulin‐dependent kinase II phosphorylation of the GABA_A receptor α1 subunit modulates benzodiazepine binding

Abstract

c-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 both allosteric 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 a1 subunit. The data suggest that the CaM kinase II-dependent phosphorylation of the GABA A receptor a1 subunit modulated allosteric modulator binding to the GABA A receptor.

Corticotrophin Releasing Factor-Induced Synaptic Plasticity in the Amygdala Translates Stress into Emotional Disorders

“…Our findings are consistent with other behavioral studies that also show that antagonism of CaMKII within the BLA will block the acquisition of aversive behaviors (Tan and Liang, 1997) but not the expression of the behavior (Malinow et al, 1989). Paradoxically, acute CaMKII activation has been reported to enhance GABA A receptormediated transmission (Churn et al, 2002;Kawaguchi and Hirano, 2002). However, a preferential downregulation of GABA A receptors has been reported in the neocortex after withdrawal from periods of elevated GABA A receptor activation, resulting in hyperexcitability and seizure activity (S. S. Casasola et al, 2001).…”

NMDA Receptor Activation Potentiates Inhibitory Transmission through GABA Receptor-Associated Protein-Dependent Exocytosis of GABAAReceptors

“…We next investigated the involvement of CaMKII as follows: (1) it is activated by Ca 2ϩ , (2) it is known to phosphorylate the GABA A R (Churn et al, 2002), (3) infusion of Ca 2ϩ -CaM has been shown to increase GABA A R currents in CA1 pyramidal neurons (Wei et al, 2004), and (4) Ca 2ϩ -CaM-dependent enhancement is blocked by addition of an autoinhibitory form of CaMKII (Wei et al, 2004). When we inhibited CaMKII in cultured neu- , intensity of synaptic, GAD-65-overlapping GABA A R puncta (black bar), as well as the overall number of GABA A R puncta per 10 m length of dendrite (dark gray bar) (n ϭ 5).…”

Diazepam‐induced adaptive plasticity revealed by α1 GABAA receptor‐specific expression profiling

“…Diazepam may thus limit the neuronal responsiveness to changes in intracellular Ca 2+ levels. Several studies have pointed to the presence of consensus sites for CaMKII phosphorylation of the GABA A receptor in c2L, c2S and b subunits (Machu et al 1993;McDonald and Moss 1994), and phosphorylation of the a1 subunit has been demonstrated to lead to an increase in benzodiazepine binding (Churn et al 2002). CaMKIIa has also been shown to positively modulate GABA-induced Cl -currents (Wang et al 1995).…”