Pathways of caspase activation.

There are at least four pathways to activate caspases, including: (a) the mitochondrial pathway where damage to the mitochondria leads to release of cytochrome c and activation of caspase 9, (b) the death receptor pathway where the TNF family of death receptors activate caspase 8, (c) a pathway connected to the endoplasmic reticulum, and (d) the direct activation of effector caspases by Granzyme B. The IAP family of proteins inhibits caspases 3, 7 and 9.