Which of the following members of the Bcl2 family promotes apoptosis?

Bax is a pro-apoptotic member of the Bcl2 family and plays a crucial role in promoting apoptosis. It functions by integrating into the mitochondrial membrane, where it facilitates the release of cytochrome c and other pro-apoptotic factors from the mitochondria into the cytoplasm. This release is a key step in the intrinsic pathway of apoptosis, leading to the activation of caspases, which are the executioners of cell death.

Bax is often regulated by other members of the Bcl2 family. For example, anti-apoptotic proteins like Bcl2 and BclxL can inhibit Bax's function and, therefore, prevent apoptosis. In contrast, proteins such as Bad can bind to and inhibit these anti-apoptotic members, thereby allowing Bax to exert its apoptotic effects. Thus, while other members of the Bcl2 family can have opposing roles in regulating cell survival and death, Bax directly promotes apoptosis through its action on the mitochondria.