Fig. 2

Role of survivin in apoptosis. Apoptosis can be initiated by the death-receptor (extrinsic) pathway or mitochondrial (intrinsic) pathway. Extrinsic pathway acts through caspase-8 and intrinsic pathway acts through caspase-9, but both pathways converge to activate the effector caspases-3,-7. Survivin largely interferes in mitochondrial-mediated apoptotic pathway. Apoptosome complex formed in association of Cyt-c, Apaf-1 and procaspase-9 in presence of dATP that leads to activation of procaspase-9. Survivin most probably blocks activation of caspase-9 by inhibiting apoptosome formation. It may also inhibit initiator caspase-9 and effector caspases-3 directly. Smac/DIABLO is a proapoptotic protein that inhibits activity of IAPs. Survivin antagonize the activity of Smac/DIABLO and may help in the action of another IAPs such as XIAP. XIAP is a strong inhibitor of apoptosis, which interacts directly with caspases and inhibits them