Mitochondria plays a central role in the regulation of apoptosis. They are the source of cytochrome c, pro caspase, Smac, AIF, which serve as critical factors for caspase activation. A variety of signal transduction pathways are involved in apoptosis converge upon the mitochondria, suggesting that this organelle may integrate a variety of signals, including protein kinases, cytoskeletal disturbance, and intracellular pH, etc. One major caspase activation cascade is triggered by cytochrome c released from the intermembrane space of mitochondria. Upon receiving apoptotic stimuli and activation of cell surface receptors, the outer membrane of mitochondria becomes permeable to cytochrome c. Bcl 2 or caspase family plays a pivotal role in the regulation of the permeability of the outer membrane of mitochondria in the course of caspase activation. Besides of cytochrome c/Apaf 1/caspase activation pathway, another mitochondria initiated apoptosis pathways are found. As an ignition chamber for apoptosis, mitochondria will be highlighted in apoptosis investigation.
