BCL-2 family proteins: critical checkpoints of apoptotic cell death.

Apoptosis is a morphologically distinct form of programmed cell death essential for normal development and tissue homeostasis. Aberrant regulation of this pathway is linked to multiple human diseases, including cancer, autoimmunity, neurodegenerative disorders, and diabetes. The BCL-2 family of proteins constitutes a critical control point in apoptosis residing immediately upstream of irreversible cellular damage, where family members control the release of apoptogenic factors from mitochondria. The cardinal member of this family, BCL-2, was originally discovered as the defining oncogene in follicular lymphomas, located at one reciprocal breakpoint of the t(14;18) (q32;q21) chromosomal translocation. Since this original discovery, remarkable efforts marshaled by many investigators around the world have advanced our knowledge of the basic biology, molecular mechanisms, and therapeutic targets in the apoptotic pathway. This review highlights findings from many laboratories that have helped uncover some of the critical control points in apoptosis. The emerging picture is that of an intricate cellular machinery orchestrated by tightly regulated molecular interactions and conformational changes within BCL-2 family proteins that ultimately govern the cellular commitment to apoptotic death.