什么是Caspase级联反应

Question

生化当中经常提到CASPASE级联反应，究竟什么是CASPASE级联反应，它有多少条通路，每条通路之间的关系是什么

Answer 1

Caspase 是一类与凋亡密切相关的蛋白水解酶家族,以Caspase前体酶原的形式存在大多后生动物的细胞中.
Caspase在凋亡信号的作用下首先激活启动型Caspase引发Caspase级联反应（Caspase Cascade）,然后通过活化的执行型Caspase裂解特异性底物导致细胞凋亡.Caspase的活化是导致细胞凋亡的中心环节,位于Caspase级联反应上游的启动型Caspase的和下游的执行型Caspase有着明显不同的活化机制.

有一个英文的简单的描述：
Caspase Cascade

Apoptosis or programmed cell death is triggered by a variety of stimuli, including cell surface receptors like FAS, the mitochondrial response to stress, and factors released from cytotoxic T cells. The caspases comprise a class of cysteine proteases many members of which are involved in apoptosis. The caspases convey the apoptotic signal in a proteolytic cascade, with caspases cleaving and activating other caspases that subsequently degrade cellular targets that lead to cell death. The activating caspases include caspase-8 and caspase-9. Caspase-8 is the initial caspase activated in response to receptors with a death domain that interacts with FADD. The mitochondrial stress pathway begins with the release of cytochrome c from mitochondria, which then interacts with Apaf-1, causing self-cleavage and activation of caspase-9. The effector caspases, caspase-3, -6 and-7 are downstream of the activator caspases and act to cleave various cellular targets. Granzyme B and perforin, proteins released by cytotoxic T cells, induce apoptosis in target cells by forming transmembrane pores and triggering apoptosis, perhaps through cleavage of caspases. Caspase independent mechanisms of granzyme B-mediated apoptosis have been suggested.