Dimerization and processing of procaspase-9 by redox stress in mitochondria
Dimerization and processing of procaspase-9 by redox stress in mitochondria
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DOI：
10.1074/jbc.m311819200
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发表时间：
2004-04-09
影响因子：
4.8
通讯作者：
Kurata, S
中科院分区：
文献类型：
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作者：
Katoh, I;Tomimori, Y;Kurata, S
我们研究了通过氧化还原反应激活线粒体内死亡引发剂caspase-9的机制，过氧化氢（H2O2）引起内膜电位（Deltapsim）的轻微降低，几乎没有细胞色素c释放的证据。caspase-9的线粒体内自裂的启动先于caspase级联诱导在细胞质中开始。当暴露于H2O2时，纯化的线粒体显示出procaspase-9加工和释放能力。Bcl-2过表达引起线粒体中活性形式caspase-9的积累，使细胞抵抗氧化还原应激。有趣的是，自加工caspase-9的二硫键二聚体在凋亡前阶段在线粒体中产生。使用底物类似物抑制剂，在线粒体内也可以检测到procaspase-9的二聚体形成。此外，巯基还原剂硫氧还蛋白阻断了caspase-9的激活步骤和细胞死亡诱导。因此，线粒体中氧化还原应激反应的硫醇-二硫转化反应似乎介导了procaspase-9的组装，从而允许自动加工。本研究解释了最近观察到的apaf -1缺失的细胞可以执行凋亡，而凋亡可以被Bcl-2阻断，并支持细胞色素c-Apaf-1-procaspase-9复合物在caspase扩增而不是其起始过程中起作用的观点。
We studied the mechanism of intra-mitochondrial death initiator caspase-9 activation by a redox response, in which hydrogen peroxide (H2O2) caused a subtle decrease in the inner membrane potential (Deltapsim) with little evidence of cytochrome c release. Initiation of the intra-mitochondrial autocleavage of procaspase-9 preceded the onset of caspase cascade induction in the cytosol. Purified mitochondria demonstrated procaspase-9 processing and releasing abilities when exposed to H2O2. Bcl-2 overexpression caused accumulation of the active form caspase-9 in the mitochondria, rendering the cells resistant to the redox stress. Intriguingly, disulfide-bonded dimers of autoprocessed caspase-9 were generated in the mitochondria in the pre-apoptotic phase. Using a substrate- analog inhibitor, dimer formation of procaspase-9 was also detectable inside the mitochondria. Furthermore, thiol reductant thioredoxin blocked the caspase-9 activation step and the cell death induction. Thus, redox stress-responsive thiol-disulfide converting reactions in the mitochondrion seemed to mediate procaspase-9 assembly that allows autoprocessing. This study offers an explanation for the recent observation that Apaf-1-null cells can execute apoptosis, which can be blocked by Bcl-2, and supports the proposition that the cytochrome c-Apaf-1-procaspase-9 complex functions in the caspase amplification rather than in its initiation.