Apoptosis (programmed cell death)
The integrity of multicellular organisms depends not only on the body’s ability to produce new cells but on controlled cell death as well. Apoptosis, or programmed cell death, is the opposite of mitosis. It is an active process for destruction of unwanted and superfluous cells. Changes in cell survival contributes to the pathogenesis in such varied disorders as cancer, viral infections, neuropathies and immunopathies. The growing understanding of apoptosis forms the basis for development of new therapeutic strategies controlling cell death.
Apoptosis may be induced by lack of anti-apoptotic stimulation, leading to loss of normal mitochondrion structure and release of the enzyme cytochrome C, or by ligands binding to the TNF receptor family of molecules, such as TNF and lymphotoxin (LT), TNF-Related Apoptosis- Inducing Ligand(s)(TRAIL), and FasL.
In the cytoplasm, the energy-dependent binding of cytochrome C to apoptotic protease-activating factor (Apaf-1) triggers the caspase cascade resulting in degradation of vital cellular proteins and genetic materials. This leads to the formation of apoptotic bodies, which are taken up by surrounding phagocytes without causing inflammation.
