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Cells with DNA damage caused by ultraviolet radiation can become cancerous. Normally, cells damaged by excessive exposure to sunlight are eliminated when they undergo programmed cell death or apoptosis. The protein kinase Rho-associated kinase (ROCK) has been implicated in promoting apoptosis in various cell types. To explore how it might do so, Ongusaha et al. identified proteins that preferentially associated with ROCK in cultured human embryonic kidney cells that had been exposed to radiation. One such protein was c-Jun N-terminal kinase (JNK)-interacting protein 3 (JIP3), a scaffold protein that regulates the activity of JNK, a protein kinase that can promote apoptosis. ROCK phosphorylated JNK in vitro, and pharmacological inhibition of ROCK in cultured cells blocked the association of JIP3 with ROCK and also the phosphorylation of JIP3 in response to irradiation. Epidermal cells from ROCK+/- mice, which have about half the normal amount of ROCK, showed decreased phosphorylation of JNK and decreased apoptosis after exposure to ultraviolet radiation. Thus, the authors propose that signaling from ROCK to JNK through JIP3 may constitute an important part of the cell death pathway that gets rid of damaged skin cells and protects organisms from skin cancer. -- LBR
Sci. Signal.1, ra14 (2008).
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