A caspase-resistant mutant of PKC-δ protects keratinocytes from UV-induced apoptosis

Abstract

Keratinocyte apoptosis induced by UV radiation is a major protective mechanism from skin photocarcinogenesis. The induction of apoptosis by UV radiation, as well as a variety of genotoxic stimuli, involves the activation of PKC-δ by caspase-3-mediated cleavage in its hinge region, thus generating a constitutively active catalytic fragment. To determine the role of PKC-δ cleavage in UV apoptosis signaling, we introduced a caspase-resistant PKC-δ mutant (D330A) into human keratinocytes by retrovirus transduction. Overexpression of PKC-δ(D330A) protected keratinocytes from UV-induced apoptosis and enhanced long-term survival. PKC-δ(D330A) partially prevented the release of cytochrome c from the mitochondria and the loss of Mcl-1, a key antiapoptotic protein downregulated during UV apoptosis. Thus, the cleavage and activation of PKC-δ are critical components of UV-induced apoptosis in human keratinocytes, and the inactivation of PKC-δ can promote the survival of keratinocytes exposed to UV radiation. © 2005 Nature Publishing Group All rights reserved.