Association of protein kinase C with GABA_A receptors containing α1 and α4 subunits in the cerebral cortex: Selective effects of chronic ethanol consumption

Previous studies have suggested that protein kinase C (PKC) isoforms differentially influence the sensitivity of γ-aminobutyric acid_A (GABA_A) receptor responses in brain. Both PKCγ and PKCε knock-out mice exhibit altered ethanol potentiation of GABA_A receptor mediated Cl^- flux. Furthermore, chronic ethanol consumption alters GABA_A receptor function and receptor subunit peptide expression by mechanisms that are not yet understood. The present study explored the possibility that PKC isoforms are directly associated with GABA_A receptors, and this association is influenced by chronic ethanol exposure. GABA_A receptors containing α1 or α4 subunits were immunoprecipitated from solubilized protein derived from the membrane fraction of rat cerebral cortex using selective antibodies. Immunoprecipitated receptors were screened by western blot analysis for the presence of PKCδ, γ and ε isoforms. We found pronounced labeling of PKCγ but not PKCδ or PKCε in the α1 and α4 subunit immunoprecipitates. Immunoprecipitation with PKCγ, but not with IgG antibody also yielded GABA_A receptor α1 and α4 subunits in the immunoprecipitate. The association of PKCγ with α1-containing receptors was decreased 44 ± 11 % after chronic ethanol consumption. In contrast, PKCγ associated with α4-containing receptors was increased 32 ± 7% after chronic ethanol consumption. These results suggest that PKCγ may be involved in GABA_A receptor adaptations following chronic ethanol consumption.