Bax directly induces release of cytochrome c from isolated mitochondria
Bax directly induces release of cytochrome c from isolated mitochondria
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DOI：
10.1073/pnas.95.9.4997
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发表时间：
1998-04-28
影响因子：
11.1
通讯作者：
Reed, JC
中科院分区：
文献类型：
--
作者：
Jürgensmeier, JM;Xie, ZH;Reed, JC
Bax是Bcl-2蛋白家族中的一个促凋亡蛋白，位于线粒体外膜上，Bax是通过其通道蛋白的功能直接促进细胞死亡还是通过抑制细胞死亡蛋白酶的调节因子间接促进细胞死亡，目前还存在争议我们在这里表明，向分离的线粒体中加入亚微摩尔量的重组Bax蛋白可以诱导细胞色素c（Cyt c）释放，而代表Bax BH 3结构域的肽是无活性的。当置于纯化的胞液中时，线粒体和Bax均不单独诱导蛋白水解加工和caspase活化，相反，Bax和线粒体的组合触发线粒体释放Cyt c并诱导胞液中caspase活化，来自经Bax处理的线粒体的上清液也诱导caspase加工和活化。重组Bcl-X-L蛋白可抑制线粒体Cyt c的释放，并抑制caspase的激活。相反，广泛特异性的半胱天冬酶抑制剂苄氧羰基-缬氨酰-丙氨酰-乙酰-（O-甲基）-氟甲基酮（zVAD-fatomy）和半胱天冬酶抑制蛋白X-IAP对体外线粒体中的Cyt c的释放没有影响，但阻止了随后的胞质提取物中半胱天冬酶的激活。与经典的线粒体通透性转换诱导剂Ca 2+不同，Bax在体外不诱导线粒体肿胀。由于细胞器肿胀引起的渗透性转变导致外膜破裂，因此，研究结果，解离这两个事件，这意味着Bax使用另一种机制触发释放的细胞色素c从线粒体。
Bax is a pro-apoptotic member of the Bcl-2 protein family that resides in the outer mitochondrial membrane, It is controversial whether Bax promotes cell death directly through its putative function as a channel protein versus indirectly by inhibiting cellular regulators of the cell death proteases (caspases), We show here that addition of submicromolar amounts of recombinant Bax protein to isolated mitochondria can induce cytochrome c (Cyt c) release, whereas a peptide representing the Bax BH3 domain was inactive. When placed into purified cytosol, neither mitochondria nor Bax individually induced proteolytic processing and activation of caspases, In contrast, the combination of Bax and mitochondria triggered release of Cyt c from mitochondria and induced caspase activation in cytosols, Supernatants from Bax-treated mitochondria also induced caspase processing and activation. Recombinant Bcl-X-L protein abrogated Bax-induced release of Cyt c from isolated mitochondria and prevented caspase activation. In contrast, the broad-specificity caspase inhibitor benzyloxycarbonyl-valinyl-alaninyl-aspartyl-(O-methyl)-fluoromethylketone (zVAD-fmk) and the caspase-inhibiting protein X-IAP had no effect on Bax-induced release of Cyt c from mitochondria in vitro but prevented the subsequent activation of caspases in cytosolic extracts. Unlike Ca2+, a classical inducer of mitochondrial permeability transition, Bax did not induce swelling of mitochondria in vitro. Because the organellar swelling caused by permeability transition causes outer membrane rupture, the findings, therefore, dissociate these two events, implying that Bax uses an alternative mechanism for triggering release of Cyt c from mitochondria.