A new mechanism of action of a C2 domain-derived novel PKC inhibitor peptide

Novel protein kinase Cs (nPKCs) contain an N-terminal C2 domain that cannot bind to calcium. We have previously shown that the Aplysia novel PKC Apl II's C2 domain inhibits binding of diacylglycerol (DAG) to the C1 domain and that this inhibition is removed by phosphatidic acid (PA) binding to the C1b domain. Another model for C2 domain regulation of nPKCs suggests that the C2 domain binds to receptors for activated C kinase (RACKs) to assist in kinase translocation and activation. In the present study, we examined how a pharmacological peptide derived from RACK-binding site in the vertebrate novel PKCɛ regulates translocation of PKC Apl II from the cytosol to the plasma membrane. We found that a C2 domain-derived inhibitor peptide inhibited PKC Apl II translocation. This inhibition was removed by R273H mutation in the C1b domain and by phosphatidic acid, which can both remove C2-domain mediated inhibition suggesting that the peptide can regulate C1–C2 domain interactions.

► A C2-domain derived peptide based on RACK binding site inhibits translocation of the novel PKC Apl II.
► Phosphatidic acid and the Arg273 to His mutation both block the effect of the inhibitor peptide.
► The C2-domain derived inhibitor peptide acts by increasing C2-domain mediated inhibition in PKC.