PROTEIN-KINASE-C ENHANCES RECOMBINANT BOVINE ALPHA-1-BETA-1-GAMMA-2L GABA(A) RECEPTOR WHOLE-CELL CURRENTS EXPRESSED IN L929 FIBROBLASTS

The beta 1 and gamma 2L subunits of the gamma-aminobutyric acid type A receptor (GABAR) contain phosphorylation sites for PKC. To determine the effect of PKC on GABAR function, whole-cell recordings were obtain ed from mouse fibroblasts expressing recombinant alpha 1 beta 1 gamma 2L receptors, and catalytically active PKC (PKM) was applied via the r ecording pipette. The first experiment was a population study. Intrace llular application of PKM increased GABAR currents, and the enhancemen t was antagonized by coapplication of the PKC inhibitory peptide. No a cceleration or deceleration of GABAR desensitization was observed. The second experiment was a reimpalement study in which paired recordings were made successively from individual cells. Enhancement of GABAR cu rrents by PKM was again obtained. PKM increased GABAR currents at high (>10 mu M) but not at low (<10 mu M) GABA concentrations, resulting i n increases in both EC(50) and maximal GABAR current. Thus, PKC phosph orylation enhanced recombinant alpha 1 beta 1 gamma 2L GABAR current b y increasing maximal current without increasing the affinity of GABA f or the GABARs.