Figure 1.

The main features of extrinsic and intrinsic apoptosis pathways. Fas receptor-mediated pathway is shown as an example of extrinsic apoptotic pathway. Extrinsic apoptosis is initiated by ligation of death receptor Fas leading to the formation of DISC and activation of caspases. Sometimes, BID cleavage into truncated BID (tBID) and mitochondrial route is required for caspase activation in extrinsic apoptosis. Intracellular stress conditions initiate intrinsic pathway of apoptosis, where Bcl-2 family members and MMP play major roles. MMP can be mediated by pore-forming activity of Bax and/or tBID or by mPT. If caspases are inhibited, apoptosis may be executed by apoptosis-inducing factor (AIF) and endonuclease G (ENDOG).