INDUCTION AND PHOSPHORYLATION OF PROTEIN-KINASE C-ALPHA AND MITOGEN-ACTIVATED PROTEIN-KINASE BY HYPOXIA AND BY RADIATION IN CHINESE-HAMSTERV79 CELLS

Protein kinase C (PKC) and mitogen-activated protein (MAP) kinase are protein-serine/threonine kinases which are important regulators of div erse cellular processes including metabolism, proliferation and differ entiation. This study shows that both hypoxia and X irradiation of ser um-deprived Chinese hamster V79 cells cause the induction and phosphor ylation of the PKC-alpha isoform. The increased induction and phosphor ylation of PKC occur mainly in the nuclear fraction. Unlike the PKC ac tivator TPA, neither hypoxic nor radiation stress causes translocation of PKC-alpha from the cytosol to the membrane. The induction of PKC-a lpha by hypoxia is accompanied by an increased expression of MAP kinas e but, in contrast, this does not occur when PKC-alpha is induced by r adiation. Radiation, like TPA, cause a complete redistribution of MAP kinase from the cytosol to the nucleus. (C) 1996 by Radiation Research Society.