The death substrate Gas2 binds m-calpain and increases susceptibility to p53-dependent apoptosis

Gas2 is a caspase-3 substrate that plays a role in regulating microfilament and cell shape changes during apoptosis, Here we provide evidence that ove rexpression of Gas2 efficiently increases cell susceptibility to apoptosis following UV irradiation, etoposide and methyl methanesulfonate treatments, and that these effects are dependent on increased p53 stability and transc ription activity. To investigate possible pathways linking Gas2 to p53, a y east two-hybrid screen swas performed, indicating m-calpain as a strong Gas 2-interacting protein. Moreover, we demonstrate that Gas2 physically intera cts with m-calpain in vivo and that recombinant Gas2 inhibits calpain-depen dent processing of p53, Importantly, the Gas2 dominant-negative form (Gas2 Delta 171-314) that binds calpain but is unable to inhibit its activity abr ogates Gas2's ability to stabilize p53, to enhance p53 transcriptional acti vity and to induce p53-dependent apoptosis, Finally, we show that Gas2 is a ble to regulate the levels of p53 independently of Mdm2 status, suggesting that, like calpastatin, it may enhance p53 stability by inhibiting calpain activity.