Mitochondria-mediated caspase activation at the apoptosome.
A. Apoptotic stimuli trigger the release of apoptogenic factors from the mitochondrial intermembrane space to the cytosol, such as cytochrome c which induces the formation of the apoptosome and the activation of procaspase-9. B. By the action of cytochrome c (Cyto C) and dATP the Apaf-1 protein adopts a conformation that allows the formation of a heptameric, wheel-like structure, the apoptosome. Procaspase-9 molecules can bind to the inner “hub” region of the apoptosome and are activated by dimer formation. Active caspase-9 dimers further mediate activation of effector caspases [Acehan, 2002].