Caspase-8/FLICE functions as an executioner caspase in anticancer drug-induced apoptosis
Caspase-8/FLICE functions as an executioner caspase in anticancer drug-induced apoptosis
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DOI：
10.1038/sj.onc.1203824
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发表时间：
2000-09-21
期刊：
影响因子：
8
通讯作者：
Wesselborg, S
中科院分区：
文献类型：
--
作者：
Engels, IH;Stepczynska, A;Wesselborg, S
Caspase-8在死亡受体引发的细胞凋亡中发挥重要作用，通过裂解促凋亡Bcl-2成员Bid，进一步激活线粒体细胞色素c/Apaf-1通路。由于 caspase-8 也可以独立于死亡受体而被抗癌药物加工，因此我们研究了它在 caspase 级联中的确切作用和顺序。我们发现，在 Jurkat 细胞中，无论是 caspase-8 缺陷还是其抑制剂 c-FLIP 过表达，CD95 介导的细胞凋亡都会受到抑制，但抗癌药物不会抑制细胞凋亡。在缺乏活性 caspase-8 的情况下，抗癌药物仍然诱导 caspase-9、-3 和 Bid 的加工，表明 Bid 裂解不需要 caspase-8，Bcl-x(L) 的过表达阻止了 caspase-8 以及 caspase-9、-6 和 Bid 对药物的反应，但在 CD95 诱导的细胞凋亡中效果较差，通过显性失活 caspase-9 突变体的过表达观察到类似的反应，为了进一步确定 caspase-8 激活的顺序，我们使用了缺乏 caspase-3 的 MCF7 细胞，与这些细胞中裂解的 caspase-9 相比，抗癌药物仅在 caspase-3 转染的 MCF7 细胞中诱导 caspase-8 激活。因此，我们的数据表明，与受体信号转导中的近端作用不同，在线粒体途径中 caspase-8 的功能更像是放大刽子手 caspase。
Caspase-8 plays an essential role in apoptosis triggered by death receptors, Through the cleavage of Bid, a proapoptotic Bcl-2 member, it further activates the mitochondrial cytochrome c/Apaf-1 pathway. Because caspase-8 can be processed also by anticancer drugs independently of death receptors, we investigated its exact role and order in the caspase cascade. We show that in Jurkat cells either deficient for caspase-8 or overexpressing its inhibitor c-FLIP apoptosis mediated by CD95, but not by anticancer drugs was inhibited. In the absence of active caspase-8, anticancer drugs still induced the processing of caspase-9, -3 and Bid, indicating that Bid cleavage does not require caspase-8, Overexpression of Bcl-x(L) prevented the processing of caspase-8 as well as caspase-9, -6 and Bid in response to drugs, but was less effective in CD95-induced apoptosis, Similar responses were observed by overexpression of a dominant-negative caspase-9 mutant, To further determine the order of caspase-8 activation, we employed MCF7 cells lacking caspase-3, In contrast to caspase-9 that was cleaved in these cells, anticancer drugs induced caspase-8 activation only in caspase-3 transfected MCF7 cells. Thus, our data indicate that, unlike its proximal role in receptor signaling, in the mitochondrial pathway caspase-8 rather functions as an amplifying executioner caspase.