Figure 3.

Pathways of Apoptosis. Apoptosis mainly consist of two main pathways and third is executioner pathway of apoptosis. Extrinsic pathway triggered by external stimuli or ligand molecule and particularly involve death receptors (DRs). The intrinsic pathway is mediated by Bax/Bak insertion into mitochondrial membrane, and subsequently, cytochrome c released which combines with Apaf–1 and procaspase-9 to produce apoptosome followed by the activation of caspase 3 cascade of apoptosis. TNF related apoptosis inducing ligand (TRAIL), cellular FLICE inhibitory proteins (cFLIP), Truncated bid (tBid), B-cell lymphoma protein 2 (Bcl-2), Bcl-2 homologue splice variants (Bcl-xL), Cytochrome (Cyt C), Second mitochondrial activator of caspases (SMAC), Inhibitor of apoptosis proteins (IAPs).