Protein Kinase Cϵ Regulates γ-Aminobutyrate Type A Receptor Sensitivity to Ethanol and Benzodiazepines through Phosphorylation of γ2 Subunits

Ethanol enhances gamma-aminobutyrate ( GABA) signaling in the brain, but its actions are inconsistent at GABA(A) receptors, especially at low concentrations achieved during social drinking. We postulated that the epsilon isoform of protein kinase C ( PKC epsilon) regulates the ethanol sensitivity of GABA(A) receptors, as mice lacking PKC epsilon show an increased behavioral response to ethanol. Here we developed an ATP analog-sensitive PKC epsilon mutant to selectively inhibit the catalytic activity of PKC epsilon. We used this mutant and PKC epsilon(-/-) mice to determine that PKC epsilon phosphorylates gamma 2 subunits at serine 327 and that reduced phosphorylation of this site enhances the actions of ethanol and benzodiazepines at alpha 1 beta 2 gamma 2 receptors, which is the most abundant GABA(A) receptor subtype in the brain. Our findings indicate that PKC epsilon phosphorylation of gamma 2 regulates the response of GABA(A) receptors to specific allosteric modulators, and, in particular, PKC epsilon inhibition renders these receptors sensitive to low intoxicating concentrations of ethanol.