Apoptosis is a naturally occurring process by which a cell is directed to Programmed Cell Death. Apoptosis is based on a genetic program that is an indispensable part of the development and function of an organism. In this process, cells that are no longer needed or that will be detrimental to an organism or tissue are disposed of in a neat and orderly manner; this prevents the development of an inflammatory response, which is often associated with Necrotic cell death. There are at least two broad pathways that lead to Apoptosis, an "Extrinsic" and an "Intrinsic" Pathway. In both pathways, signaling results in the activation of a family of Cys (Cysteine) Proteases, named Caspases that act in a proteolytic cascade to dismantle and remove the dying cell. The extrinsic pathway begins outside a cell, when conditions in the extracellular environment determine that a cell must die. The intrinsic apoptosis pathway begins when an injury occurs within the cell. The injury could result in necrosis and produce an inflammatory response, but the apoptotic machinery is in place to ensure that the damaged cell is packaged and removed cleanly, in order to prevent inflammation. Apoptosis in Mitochondria is the best known intrinsic apoptosis pathway (Ref.1 & 2).
References:
1.Teaching resources. Apoptosis.
Wilk S. Sci STKE. 2005 May 24;2005(285):tr16. 2.Apoptosome formation and caspase activation: is it different in the heart? Czerski L, Nunez G. J Mol Cell Cardiol. 2004 Sep;37(3):643-52. Review. 3.Role of mitochondria as the gardens of cell death. Kim R, Emi M, Tanabe K Cancer Chemother Pharmacol. 2005 Sep 21;:1-9 4.Cutting edge: innate immunity conferred by B cells is regulated by caspase-8. Beisner DR, Ch'en IL, Kolla RV, Hoffmann A, Hedrick SM. J Immunol. 2005 Sep 15;175(6):3469-73. 5.TRAIL-induced apoptosis in human vascular endothelium is regulated by phosphatidylinositol 3-kinase/Akt through the short form of cellular FLIP and Bcl-2. Alladina SJ, Song JH, Davidge ST, Hao C, Easton AS. J Vasc Res. 2005 Jul-Aug;42(4):337-47. Epub 2005 Jun 28. 6.The p53 pathway: positive and negative feedback loops. Harris SL, Levine AJ. Oncogene. 2005 Apr 18;24(17):2899-908. Review. 7.Unknotting the roles of Bcl-2 and Bcl-xL in cell death. Kim R. Biochem Biophys Res Commun. 2005 Jul 29;333(2):336-43. 8.Endoplasmic reticulum quality control and apoptosis. Groenendyk J, Michalak M. Acta Biochim Pol. 2005;52(2):381-95. Epub 2005 May 31. 9.Mitochondrial dysfunction and heart disease. Rosenberg P. Mitochondrion. 2004 Sep;4(5-6):621-8. Epub 2004 Oct 28.
|