Mechanisms of Bcl-2 protein function.

The Bcl-2 protein blocks a distal step in an evolutionarily conserved pathway for programmed cell death and apoptosis. The gene encoding this protein was first discovered because of its involvement in the t(14;18) chromosomal translocations commonly found in B-cell lymphomas. Overexpression of Bcl-2 also occurs in many other types of human cancers, and prevents cell death induced by nearly all anticancer drugs and radiation. Since the discovery of Bcl-2 over ten years ago, several cellular and viral homologs have been identified, some of which suppress cell death and others which promote apoptosis. Many of these proteins can interact with each other through a complex network of homo- and heterodimers. Though functionally important, dimerization events still do not explain in a broader sense how these proteins actually control cell life and death. Recent findings that Bcl-2 can function both as an ion channel and as an adapter or docking protein however are beginning to provide insights into the molecular mechanisms through which these proteins regulate the programmed cell death pathway in normalcy and disease.