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KMID : 0670720000050010001
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Journal of the Korean Society Hyperthermia Oncology
2000 Volume.5 No. 1 p.1 ~ p.11
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The Regulatory Mechanism of Apoptosis
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Abstract
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Apoptosis is a cell suicide mechanism to control cell number in tissues and to eliminate individual cells that threaten the animal's survival. Apoptosis plays a central role both in development and in homeostasis. Cells die by apoptosis in the
developing embryo during morphogenesis or synaptogenesis and in the adult animal during tissue turnover or at the end of an immune response. Survival signals from the cell's environment and internal sensors for cellular integrity normally keep a
cell's
apoptotic machinery in check. Mammals have evolved yet another mechanism that enables the organism actively to direct individual cells to self-destruct. Death receptors belong to the tumor necrosis factor (TNF) receptor gene superfamily which is
defined
by similar, cysteine-rich extracellular domains. The central component of machinery is a proteolytic system involving family of proteases called caspases. These enzymes participate in a cascade that is triggered in response to proapoptotic
signals
and
culminates in cleavage of a set of proteins, resulting in disassembly of the cell. Two independent apoptosis pathways are presented that converge on the activation of downstream caspase-3, -6, and -7, key substrate cleavage, and apoptotic death.
One way
involves ligation of death receptors by ligand, resulting in the recruitment of adaptor proteins and procaspase molecules. The complex is an apoptosome. Tn the second pathway, mitochondrial release of cytochrome c by cellular stress, which binds
to
Apaf1, which in turn self-associates and binds procaspase-9, resulting in an apoptosome.
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