FIGURE 3.

The molecular mechanism of apoptosis. Classic regulatory pathways of apoptosis include extrinsic pathway and intrinsic pathway. Intrinsic pathway is mitochondria dependent and regulated by BCL2 protein family which can influence the release of cytochrome C from the mitochondria. Cytochrome c can bind to the cytosolic protein Apaf-1 and promote the formation of an apoptosome to recruit and activate caspase-9, which in turn activates caspase-3 and leads to cell apoptosis. Extrinsic pathway is initiated by the transmission of death signals from the cell’s surface through the binding of ligands and the death receptors, resulting in the aggregation and recruitment of initiator caspases that subsequently activates executioner caspase 3, leading to apoptosis.