FIG. 5.

Apoptotic pathways. Apoptosis occurs through two main pathways: the extrinsic pathway or death-receptor pathway, and the intrinsic or mitochondrial pathway. Both pathways converge to a final common pathway involving the activation of caspase-3 that culminates in the execution of cell death. In many cell types, the extrinsic and intrinsic pathways are integrated through the cleavage of Bid by caspase-8, consequently conferring on mitochondria a central role in the control of cell death by apoptosis.