DESCRIPTION: UV irradiation of cells elicits complicated cellular responses, called the stress response. Based on Preliminary Data, experiments are proposed to test the hypothesis that UV irradiation causes activation of membrane receptors such as the Fas receptor and TNF receptor I, which results in reduction of apoptosis that is analogous to Fas ligand and TNF2-induced apoptosis. Studies will test the hypothesis that UV irradiation induces apoptosis by activating Fas receptor and subsequent interaction with FADD as a pathway to UV-induced apoptosis. The subsequent role in activation of FLICE will be tested followed by investigation of the role of ICE-like proteases in UV-induced apoptosis. These studies will provide a detailed picture of the pathway for UV-induced apoptosis.