CAVEOLIN INTERACTION WITH PROTEIN-KINASE-C - ISOENZYME-DEPENDENT REGULATION OF KINASE-ACTIVITY BY THE CAVEOLIN SCAFFOLDING DOMAIN PEPTIDE

Caveolar localization of protein kinase C and the regulation of caveol ar function by protein kinase C are well known, This study was underta ken to examine whether caveolin subtypes interact with various protein kinase C isoenzymes using the caveolin scaffolding domain peptide. Wh en protein kinase C-alpha, -epsilon, and -zeta were overexpressed in C OS cells followed by subcellular fractionation using the sucrose gradi ent method, all the isoenzymes (alpha, epsilon, and zeta) were detecte d in the same fraction as caveolin. The scaffolding domain peptide of caveolin-1 and -3, but not -2, inhibited the kinase activity and autop hosphorylation of protein kinase C-alpha and -zeta, but not of protein kinase C-epsilon, overexpressed in insect cells. Truncation mutation studies of the caveolin-1 and -3 peptides demonstrated that a minimum of 16 or 14 amino acid residues of the peptide were required for the i nhibition or direct binding of protein kinase C, Thus, the caveolin pe ptide physically interacted with protein kinase C and regulated its fu nction. Further, this regulation occurred in a protein kinase C isoenz yme-dependent manner. Our results may provide a new mechanism regardin g the regulation of protein kinase C isoenzyme activity and the molecu lar interaction of protein kinase C with its putative binding proteins .