Phosphorylation of Bcl-2 protein and association with p21(Ras) in Ras-induced apoptosis

p21(Ras) mediates mitogenic responses and also renders cells susceptible to apoptosis after inhibition of protein kinase C (PKC) activity. Ras-induced apoptosis can be blocked by the proto-oncogene bcl-2, but the biochemical or functional nature of Bcl-2 regulation of Ras-induced apoptosis is not understood. We demonstrate that Bcl-2 and p21(Ras) molecules can be co-immunoprecipitated in Jurkat cells. The level of this association is enhanced when an apoptotic stimulus (inhibition of PKC activity) is delivered. Bcl-2/p21(Ras) association is coincident with new phosphorylation of the Bcl-2 protein. Inhibition of this phosphorylation prevents protection from apoptosis by Bcl-2, providing a functional cor relation to the phosphorylation event. The Bcl-2/p21(Ras) association cannot be competed by exogenous glutathione S-transferase-Ras fusion protein, suggesting that the endogenous complex may be formed before cell lysis. These results provide a possible mechanism of regulation of has-induced apoptosis by Bcl-2.