Essential roles of the Bcl-2 family of proteins in caspase-2-induced apoptosis
Essential roles of the Bcl-2 family of proteins in caspase-2-induced apoptosis
复制标题
DOI：
10.1074/jbc.m506488200
复制
发表时间：
2005-11-18
影响因子：
4.8
通讯作者：
Jiang, XJ
中科院分区：
文献类型：
--
作者：
Gao, ZH;Shao, YF;Jiang, XJ
Caspase-2是一种启动caspase的酶，在应激诱导的多种人类癌细胞的凋亡中是必需的。最近的研究表明，它可以介导抑癌基因P53的死亡功能，并被多聚体蛋白复合体PIDDosome激活。然而，目前还不清楚caspase-2在细胞中如何发挥其凋亡功能，以及它的酶活性是否是凋亡功能所必需的。在本研究中，我们采用体外线粒体细胞色素c释放试验和细胞培养的细胞凋亡分析来探讨caspase-2诱导细胞凋亡的机制。我们发现，活性的caspase-2，但无论是催化突变的caspase-2还是活性的caspase-2及其抑制剂，都不能引起细胞色素c的释放。Caspase-2不能诱导具有Bid(-/-)背景的线粒体释放细胞色素c，加入野生型Bid蛋白可以恢复细胞色素c的释放，但不能通过突变caspase-2裂解位点的Bid恢复细胞色素c的释放。Caspase-2也不能诱导Bax(-/-)Bak(-/-)线粒体释放细胞色素c。在培养细胞中，Bax/Bak基因缺失或Bid基因缺失可抑制caspase-2过表达诱导的细胞凋亡。综上所述，这些结果表明，Bid的蛋白水解性激活以及随后通过Bax/Bak诱导的线粒体凋亡通路是caspase-2触发的细胞凋亡所必需的。
Caspase-2 is an initiating caspase required for stress-induced apoptosis in various human cancer cells. Recent studies suggest that it can mediate the death function of tumor suppressor p53 and is activated by a multimeric protein complex, PIDDosome. However, it is not clear how caspase-2 exerts its apoptotic function in cells and whether its enzymatic activity is required for the apoptotic function. In this study, we used both in vitro mitochondrial cytochrome c release assays and cell culture apoptosis analyses to investigate the mechanism by which caspase-2 induces apoptosis. We show that active caspase-2, but neither a catalytically mutated caspase-2 nor active caspase-2 with its inhibitor, can cause cytochrome c release. Caspase-2 failed to induce cytochrome c release from mitochondria with Bid(-/-) background, and the release could be restored by addition of the wild-type Bid protein, but not by Bid with the caspase-2 cleavage site mutated. Caspase-2 was not able to induce cytochrome c release from Bax(-/-)Bak(-/-) mitochondria either. In cultured cells, gene deletion of Bax/Bak or Bid abrogated apoptosis induced by overexpression of caspase-2. Collectively, these results indicate that proteolytic activation of Bid and the subsequent induction of the mitochondrial apoptotic pathway through Bax/Bak is essential for apoptosis triggered by caspase-2.