INCREASED INDUCTION OF CA2-MEDIATED DIFFERENTIATION BY GAMMA-RAY IS MEDIATED BY ENDOGENEOUS ACTIVATION OF THE PROTEIN-KINASE-C SIGNALING PATHWAYS IN MOUSE EPIDERMAL-CELLS()

Purpose: The aim of this study was to determine whether gamma-rays can affect Ca2+-induced differentiation in normal and neoplastic mouse ep idermal cells. Methods and Materials: After gamma-ray irradiation, pri mary and v-ras(Ha) transformed mouse keratinocytes were cultured for 4 8 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. Results: Morphological diff erence was seen at 48 h after irradiation in both Ca2+-shifted normal and v-ras(Ha) transformed cells; v-ras(Ha) cells were more resistant t o the radiation than normal cells. Radiation potentiated granular cell -differentiation marker expressions (filaggrin, lorierin, and SPR-I) i n both normal and v-ras(Ha) transformed cells. In the case of spinous cell markers, the expression of keratins K1 and K10, which are usually blocked in v-ras(Ha) cells was increased after irradiation. However, there was no change of K8 expression level, which can be seen only aft er v-ras(Ha) transfection. Cellular fractionation and immunoblot analy sis with antibodies against PKC alpha, delta, epsilon, eta, and xi rev ealed that PKC alpha was responsible for the differentiation marker ex pression. Conclusions: These findings suggest that PKC alpha is an imp ortant component of the signaling pathway regulating radiation-induced differentiation in both normal and neoplastic epidermal cells. (C) 19 98 Elsevier Science Inc.