Effect of PKG activation on recombinant GABA(A) receptors

The effect of cGMP-dependent protein kinase (PKG) on recombinant human alpha(i) beta(2) gamma(2L) GABA(A) receptors expressed in Xenopus oocytes was studied using the two-electrode voltage-clamp technique. The cGMP analog 8BrcGMP (1 mM) produced an increase in GABA-gated chloride currents. Intracellular injection of the PKG inhibitor peptide, PKGI, prevented the 8BrcGMP-mediated increase in the GABA response indicating that 8BrcGMP enhances GABA, receptor function via activation of PKG. Previous studies have shown that PKG phosphorylates a fusion protein corresponding to the intracellular loop of the beta 1 subunit [McDonald and Moss, J. Biol. Chem., 269 (1994) 18111-18117]. In the present study, site-directed mutagenesis of this phosphorylation site (beta 2ser410) failed to eliminate the effects of 8BrcGMP on the GABA response. These results suggest that there may be other sites on the receptor which are regulated by PKG or that PKC phosphorylates other proteins which may influence GABA(A) receptor function.