Suppression of ultraviolet irradiation-induced apoptosis by overexpressionof focal adhesion kinase in Madin-Darby canine kidney cells

Focal adhesion kinase (FAK) has been implicated tea play a role in suppress ion of apoptosis. In this study, we have demonstrated that UV irradiation i nduced cleavage of FAK and two of its interacting proteins Src and p130(Cas ) in Madin-Darby canine kidney cells, concomitant with an increase in cell death. The cleavage of these proteins upon UV irradiation was completely in hibited by ZVAD-FMK, a broad range inhibitor of caspases, and apparently de layed by Bcl2 overexpression. To examine if FAK plays a role in suppressing UV-induced apoptosis, stable Madin-Darby canine kidney cell lines overexpr essing FAK were established. Our results showed that a marked (30-40%) incr ease in cell survival upon UV irradiation was achieved by this strategy. In our efforts to determine the mechanism by which FAK transduces survival si gnals to the downstream, we found that a PAK mutant deficient in binding to phosphatidylinositol 3-kinase failed to promote cell survival. Moreover, t he expression of the Src homology 3 domain of p130(Cas), which competed wit h endogenous p130(Cas) for FAK binding, abrogated the FAK-promoted cell sur vival. Together, these results suggest that the integrity of FAK and its bi nding to phosphatidylinositol 3-kinase and p130(Cas) are required for FAK t o exert its antiapoptotic function.