DOWN-MODULATION OF A NOVEL BAX-ASSOCIATED PROTEIN DURING APOPTOSIS INNORMAL MATURE B-LYMPHOCYTES

We have recently characterized a novel 16-kDa Bax-associated protein. In this study,,ve investigate the regulation of this protein's express ion during in vitro induction of apoptosis in mature splenic B cells. A panel of biochemically distinct apoptotic stimuli induced the dramat ic down-modulation of the 16-kDa protein in B cells; this down-modulat ion was rapid, and did not require DNA fragmentation. Reciprocally, st imuli that induced protection from apoptosis prevented down-modulation of the 16-kDa protein. These regulatory effects were specific, since Bcl-2 and Bas protein levels were not similarly modulated. Stimuli tha t reduce expression of the 16-kDa protein may therefore act indirectly to increase the proapoptotic activity of Bas, perhaps by altering Bas binding to other cellular proteins.