BAD (Bcl2-antagonist Of Cell Death) is a member of the Bcl2 family and acts to promote apoptosis by forming heterodimers with the survival proteins Bcl2 and BclxL, thus preventing them from binding with BAX. Bad is found on the outer mitochondrial membrane and, once phosphorylated in response to growth stimuli, translocates to the cytoplasm. The phosphorylation status of Bad represents a key checkpoint for death or cell survival. JNK-induced phosphorylation of BAD serine 128 promotes the apoptotic role of BAD by opposing the inhibitory effect of growth factor on Bad-mediated apoptosis. Cdc2-induced phosphorylation of Bad serine 128 has an inhibitory effect on its interaction with 14-3-3 proteins. The latter interaction is critical for Bad phosphorylation at serine 155, a site within the BH3 domain that leads to the release of BclxL and the promotion of cell survival.
Images: Immunoblots of SDS-extracts from human Jurkat (3 x 105), A431 (2 x 105), mouse CTLL2 (2.5 x 105), and L929 (2 x 105) cells. Extracts were blotted with 1.0 and 2.0 μg/mL anti-BAD. Incubation with anti-Bad was overnight at 4° C and detection was by the ECL procedure (Amersham). One and five minute exposures are shown. The band that co-migrates with recombinant Bad is indicated by the arrow. The identity of the other bands is unknown.
