Which of the following is an antiapoptotic gene?
Apoptosis results from the activation of enzymes called caspases (so named because they are cysteine proteases that cleave proteins after aspaic residues). The activation of caspases depends on a finely tuned balance between production of pro- and anti-apoptotic proteins. Two distinct pathways converge on caspase activation: the mitochondrial pathway and the death receptor pathway pro-apoptotic members of the family called Bax and Bak, which dimerize, inse into the mito- chondrial membrane, and form channels through which cytochrome c and other mitochondrial proteins escape into the cytosol. These sensors also inhibit the anti-apoptotic molecules Bcl-2 and Bcl-xL (see fuher on), enhancing the leakage of mitochondrial proteins. Cytochrome c, together with some cofactors, activates caspase-9. Other proteins that leak out of mitochondria block the activities of caspase antagonists that function as physiologic inhibitors of apop- tosis. The net result is the activation of the caspase cascade, ultimately leading to nuclear fragmentation. Conversely, if cells are exposed to growth factors and other survival signals, they synthesize anti-apoptotic members of the Bcl-2 family, the two main ones of which are Bcl-2 itself and Bcl-xL. These proteins antagonize Bax and Bak, and thus limit the escape of the mitochondrial pro-apoptotic proteins. Cells deprived of growth factors not only activate the pro-apoptotic Bax and Bak but also show reduced levels of Bcl-2 and Bcl-xL, thus fuher tilting the balance toward death. ref Robbins 9/e p19
BAX
BAD
BCL-X
BIM
General pathology