KP-10, a novel protein kinase C substrate in intact mouse epidermal cells, is phosphorylated by novel protein kinase Cη and/or ξ

Abstract

Recently this group found an endogenous substrate protein for Ca(2+)-independent novel protein kinase C (nPKC), i.e. KP-10 (pI 4.7/25,500 M(r)), in primary cultured mouse epidermal cells [Nishikawa, K. et al. (1992) Cell. Signal. 4, 757-776]. In the present study, the nPKC isozymes which phosphorylate KP-10 in these cells were determined. Western blot analysis revealed that PKC alpha, eta and zeta were present in epidermal cell 105,000 g supernatants and that the content of PKC zeta was much higher than those of PKC alpha and eta. Neither PKC beta, delta nor epsilon was detected in the 105,000 g supernatants. Phosphatidylserine and phorbol 12-myristate 13-acetate (PMA)-dependent KP-10 phosphorylating activity was immunoprecipitated by anti-PKC eta and zeta antibodies, but not by antiPKC alpha antibody. These results suggest that PKC eta and/or zeta phosphorylate KP-10 and play pivotal roles in intracellular signal pathways in intact epidermal cells.