Activation of Phorbol Ester Responsive Form of Protein Kinase Cζ in Association with Ca²⁺ -Induced Differentiation of Primary Cultured Mouse Epidermal Cells

Abstract

In primary cultured mouse epidermal cells, protein kinase C (PKC) ζconsists of multiple forms: a low salt-eluted PKCζ (1-PKCζ, 79 and 85 kDa) and a high salt-eluted PKCC (h-PKCζ, 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 Ca²⁺ -concentration in culture medium, were examined. After 24 hr-treatment with 1.8 mM Ca²⁺, 79-kDa 1-PKCζ in the particulate fraction was apparently shifted to the 85-kDa form. The phosphatidylserine-dependent kinase activity of this 1-PKCζ was increased in association with the shift. These results suggest the pivotal role of 1-PKCζ in the particulate fraction in the Ca²⁺ -induced epidermal cell differentiation processes.