Bcl-2 family proteins and apoptosis.

Bcl-2 family proteins play key roles in apoptosis. They coordinate with other apoptotic proteins in apoptosis to control mitochondria stability both in structure and function, while mitochondria probably act as the main switch of apoptosis. Bcl-2 family proteins can be divided into two types, antiapoptotic proteins and pro-apoptotic proteins. During apoptosis, Bcl-2 family proapoptotic proteins can translocate to the outer membrane of mitochondrion after posttranslational modification by certain proteases such as caspases. Then cytochrome c (cyt.c), apoptosis-inducing factors (AIFs), and other proapoptotic factors are released from mitochondrion, triggering apoptosis. Bcl-2 family antiapoptotic proteins sequestered in mitochondrion have ability to inhibit the release of cyt.c and AIFs, and prevent apoptosis. When interacting with activated proapoptotic proteins, the antiapoptotic proteins lose inhibiting ability of pro-apoptotic factors' release, and again triggering apoptosis. Based on the newest research evolvements, types, structures, localizations, apoptosis regulating mechanisms of Bcl-2 family proteins are reviewed.