Paclitaxel-induced apoptosis in BJAB cells proceeds via a death receptor-independent, caspases-3/-8-driven mitochondrial amplification loop
Paclitaxel-induced apoptosis in BJAB cells proceeds via a death receptor-independent, caspases-3/-8-driven mitochondrial amplification loop
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DOI：
10.1038/sj.onc.1206280
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发表时间：
2003-04-17
期刊：
影响因子：
8
通讯作者：
Daniel, PT
中科院分区：
文献类型：
--
作者：
von Haefen, C;Wieder, T;Daniel, PT
Caspase-8是死亡受体触发的细胞凋亡的关键效应子。然而，在以前的研究中，我们证明了caspase-8也可以通过caspase-3下游的线粒体凋亡途径以不依赖于死亡受体的方式被激活。在这里，我们表明，半胱天冬酶-3和-8介导的线粒体放大环，所需的细胞色素c，线粒体通透性转换的最佳释放，并在细胞凋亡与微管损伤剂紫杉醇（紫杉醇）治疗诱导的细胞死亡。与此相反，Smac从线粒体释放遵循不同的模式，因此似乎是独立于细胞色素c的释放调节。紫杉醇诱导的细胞死亡通过使用合成的、细胞可渗透的半胱天冬酶-3-（zDEVD-festival）或半胱天冬酶-8-特异性（zIETD-festival）抑制剂来抑制。细胞凋亡信号不受显性负性FADD突变体（FADD-DN）的影响，从而排除了死亡受体信号在扩增环和药物诱导的细胞凋亡中的作用。抑制剂实验通过使用过表达天然丝氨酸蛋白酶抑制剂、细胞因子应答调节剂A的BJAB细胞得到证实。这些数据表明，线粒体的完全激活，细胞色素c的释放，以及药物诱导的细胞凋亡的执行需要依赖于半胱天冬酶-3和-8激活的线粒体扩增环。此外，这是第一个报告，以证明死亡受体的非依赖性caspase-8在体内的自动加工。
Caspase-8 is a key effector of death-receptor-triggered apoptosis. In a previous study, we demonstrated, however, that caspase-8 can also be activated in a death receptor-independent manner via the mitochondrial apoptosis pathway, downstream of caspase-3. Here, we show that caspases-3 and -8 mediate a mitochondrial amplification loop that is required for the optimal release of cytochrome c, mitochondrial permeability shift transition, and cell death during apoptosis induced by treatment with the microtubule-damaging agent paclitaxel (Taxol). In contrast, Smac release from mitochondria followed a different pattern, and therefore seems to be regulated independently from cytochrome c release. Taxol-induced cell death was inhibited by the use of synthetic, cell-permeable caspase-3- (zDEVD-fmk) or caspase-8-specific (zIETD-fmk) inhibitors. Apoptosis signaling was not affected by a dominant-negative FADD mutant (FADD-DN), thereby excluding a role of death receptor signaling in the amplification loop and drug-induced apoptosis. The inhibitor experiments were corroborated by the use of BJAB cells overexpressing the natural serpin protease inhibitor, cytokine response modifier A. These data demonstrate that the complete activation of mitochondria, release of cytochrome c, and execution of drug-induced apoptosis require a mitochondrial amplification loop that depends on caspases-3 and -8 activation. In addition, this is the first report to demonstrate death receptor-independent caspase-8 autoprocessing in vivo.