Genes, molecules, and mechanisms regulating programmed cell death

Apoptosis is a morphologically distinct form of programmed cellular death that plays a central role during embryogenesis, tissue homeostasis, and to remove not necessary or potentially dangerous cells. Moreover, disregulation of genes mediating or modulating apoptosis contributes to the pathogenesis of a number of human diseases, including cancer, autoimmune diseases, neurodegenerative disorders, viral infections and acquired immunodeficiency syndrome. A number of genes and molecules promoting or protective against cell death is at present-day known and an important information about the external and internal signals involved in stimulation and suppression of apoptosis is also emerging. In the intracellular pathway of the death deregulation of [Ca2+](i) plays a pivotal role. Increased ionized intracellular calcium stimulates both the activation of enzymes (protein kinases, endonucleases, proteases and phospholipases) and plasma membrane K+ channels. This calcium-mediated activation leads to morphostructural changes, such as cell shrinkage, cytoplasmatic blebbing, nuclear chromatin condensation and DNA degradation into oligonucleosomal fragments. At least some genes of the cell death pathway have been conserved throughout animal evolution; ced-3 e ced-9 that regulate the initiation of cellular suicide in the nematode Caenorhabditis elegans are homologous to genes that in mammalian cells are thought to play a similar role (interleukin-1 beta converting enzyme [ICE] family, Bcl-2). It is possible to suppose that these regulators could constitute a target for treatment of disorders related with disregulation of apoptosis.