This gene encodes a death agonist that heterodimerizes with either agonist BAX or antagonist BCL2. The encoded protein is a member of the BCL-2 family of cell death regulators. It is a mediator of mitochondrial damage induced by caspase-8 (CASP8); CASP8 cleaves this encoded protein, and the COOH-terminal part translocates to mitochondria where it triggers cytochrome c release. Multiple alternatively spliced transcript variants have been found, but the full-length nature of some variants has not been defined.Tissue specificity: Isoform 2 and isoform 3 are expressed in spleen, bone marrow, cerebral and cerebellar cortex. Isoform 2 is expressed in spleen, pancreas and placenta (at protein level). Isoform 3 is expressed in lung, pancreas and spleen (at protein level). Isoform 4 is expressed in lung and pancreas (at protein level)