Increased induction of Ca2+-mediated differentiation by gamma ray is mediated by endogenous activation of the protein kinase C signaling pathways in mouse epidermal cells.

Abstract

The aim of this study was to determine whether gamma-rays can affect Ca2+-induced differentiation in normal and neoplastic mouse epidermal cells. After gamma-ray irradiation, primary and v-rasHa transformed mouse keratinocytes were cultured for 48 h in 0.12 mM Ca2+-containing media, and cellular translocation from cytosolic to particulated fraction of each PKC isozyme and expressions of differentiation markers were examined. Morphological difference was seen at 48 h after irradiation in both Ca2+-shifted normal and v-rasHa transformed cells; v-rasHa cells were more resistant to the radiation than normal cells. Radiation potentiated granular cell-differentiation marker expressions (filaggrin, loricrin, and SPR-1) in both normal and v-rasHa transformed cells. In the case of spinous cell markers, the expression of keratins K1 and K10, which are usually blocked in v-rasHa cells was increased after irradiation. However, there was no change of K8 expression level, which can be seen only after v-rasHa transfection. Cellular fractionation and immunoblot analysis with antibodies against PKCalpha, delta, epsilon, eta, and xi revealed that PKCalpha was responsible for the differentiation marker expression. These findings suggest that PKCalpha is an important component of the signaling pathway regulating radiation-induced differentiation in both normal and neoplastic epidermal cells.