Activation of phorbol ester responsive form of protein kinase C zeta in association with Ca(2+)-induced differentiation of primary cultured mouse epidermal cells.

In primary cultured mouse epidermal cells, protein kinase C (PKC) zeta consists of multiple forms: a low salt-eluted PKC zeta (1-PKC zeta, 79 and 85 kDa) and a high salt-eluted PKC zeta (h-PKC zeta, 79 and 85 kDa) by anion-exchange column chromatography (K. Nishikawa et al., Cell. Signal. 7, 491-504, 1995). In the present study, PKC isozyme-specific responses during terminal differentiation of epidermal cells, which were induced by the increase of Ca(2+)-concentration in culture medium, were examined. After 24 hr-treatment with 1.8 mM Ca2+, 79-kDa 1-PKC zeta in the particulate fraction was apparently shifted to the 85-kDa form. The phosphatidylserine-dependent kinase activity of this 1-PKC zeta was increased in association with the shift. These results suggest the pivotal role of 1-PKC zeta in the particulate fraction in the Ca(2+)-induced epidermal cell differentiation processes.