Molecular strategies for the dominant inhibition of protein kinase C

The regulatory (R) domain of PKC alpha fused to glutathione-S-transferase (GST-R alpha) competitively inhibited PKC activity associated with extracts of Y1 mouse adrenocortical tumor cells and the activities of several specific PKC isozymes. GST-R alpha did not inhibit the activities of cAMP-dependent protein kinase, cGMP-dependent protein kinase or calmodulin-dependent myosin light chain kinase. GST-R alpha inhibited PKC activities 20 times more potently than did a synthetic peptide corresponding to the pseudosubstrate sequence of PKC alpha. In intact yeast cells, the R domain prevented PKC beta-1-induced inhibition of growth and cytokinesis. These results indicate that the R domain of PKC alpha acts as a specific, dominant inhibitor of PKC activity, and suggest that the PKC alpha R domain may provide a useful genetic tool to assess the roles of PKC in various signal transduction processes.