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

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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- by caspase-3-mediated cleavage in its hinge region, thus generating a constitutively active catalytic fragment. To determine the role of PKC- cleavage in UV apoptosis signaling, we introduced a caspase-resistant PKC- mutant (D330A) into human keratinocytes by retrovirus transduction. Overexpression of PKC-(D330A) protected keratinocytes from UV-induced apoptosis and enhanced long-term survival. PKC-(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- are critical components of UV-induced apoptosis in human keratinocytes, and the inactivation of PKC- can promote the survival of keratinocytes exposed to UV radiation.