Figure 1

The core pathway of programmed cell death. Multiple pathways lead to the activation of the executioners of death, the caspases (reviewed in [53]). IAPs (inhibitors of apoptosis) have been shown to block the conversion of pro-caspases into active enzymes, and Reaper, Hid, Grim, and Diablo/Smac prevent IAPs from carrying out this protective function. Caspases can also be activated with the aid of Apaf-1, which in turn appears to be regulated by cytochrome c and dATP. The Bcl-2 family appears to function in regulating the release of pro-apoptotic components from mitochondria as well as by possibly inhibiting Apaf-1 directly. This pathway integrates knowledge gained in multiple species, showing that apoptosis appears to be regulated in a similar manner regardless of the organism. One notable exception is that the C. elegans homologs of IAPs do not appear to function in programmed cell death.