PECAM-1—mediated protection from BAX-induced apoptosis is independent of the PI-3K/Akt signaling pathway. HEK 293 cells were transfected with control vector pcDNA3, Bax-encoding plasmid, and PECAM-1—encoding plasmid as indicated and then cultured for 20 hours in the presence or absence of 100 nM wortmannin—a PI-3K inhibitor. (A) Quantification of apoptosis. The number of apoptotic nuclei was counted after Hoechst staining and expressed as the percentage of total nuclei of the transfected cells. (B) Aliquots were subjected to Western blot analysis with the indicated antibodies. Note that (1) expression of PECAM-1 did not affect overall Akt antigen levels or its phosphorylation state, (2) wortmannin inhibited Akt phosphorylation as expected, and (3) blocking activation of Akt had no effect on the ability of PECAM-1 to suppress Bax overexpression—induced apoptosis.