Proteolysis of the mismatch repair protein MLH1 by caspase-3 promotes DNA damage-induced apoptosis
Proteolysis of the mismatch repair protein MLH1 by caspase-3 promotes DNA damage-induced apoptosis
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DOI：
10.1074/jbc.m400971200
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发表时间：
2004-06-25
影响因子：
4.8
通讯作者：
Cryns, VL
中科院分区：
文献类型：
--
作者：
Chen, F;Arseven, OK;Cryns, VL
半胱天冬酶是重要的促凋亡蛋白酶，其通过选择性地在Asp残基处切割蛋白质以改变其功能来执行细胞死亡信号。半胱天冬酶通过激活半胱天冬酶激活的DNA酶和通过使检测或修复DNA损伤的许多酶失活来触发凋亡染色质降解。我们已经确定了错配修复蛋白MLH 1作为一种新的caspase-3底物筛选小池的人前列腺癌cDNA文库编码caspase底物的cDNA。在这份报告中，我们证明了人MLH 1在体外被caspase-3在Asp（418）处特异性切割。此外，MLH 1在通过用肿瘤坏死因子相关凋亡诱导配体（TRAIL）或拓扑异构酶II抑制剂依托泊苷（其损伤DNA）处理而诱导经历凋亡的癌细胞中被胱天蛋白酶-3快速蛋白水解。重要的是，MLH 1的caspase-3的蛋白水解触发其从细胞核到细胞质的部分再分布，并产生促凋亡羧基末端产物。此外，我们证明，caspase-3切割抗性D418 E MLH 1突变体抑制依托泊苷诱导的细胞凋亡，但对TRAIL诱导的细胞凋亡几乎没有影响。这些结果表明，MLH 1的caspase-3的蛋白水解起着重要的功能和以前未被认识到的作用，在执行DNA损伤诱导的细胞凋亡。
Caspases are critical proapoptotic proteases that execute cell death signals by selectively cleaving proteins at Asp residues to alter their function. Caspases trigger apoptotic chromatin degradation by activating caspase-activated DNase and by inactivating a number of enzymes that sense or repair DNA damage. We have identified the mismatch repair protein MLH1 as a novel caspase-3 substrate by screening small pools of a human prostate adenocarcinoma cDNA library for cDNAs encoding caspase substrates. In this report, we demonstrate that human MLH1 is specifically cleaved by caspase-3 at Asp(418) in vitro. Furthermore, MLH1 is rapidly proteolyzed by caspase-3 in cancer cells induced to undergo apoptosis by treatment with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) or the topoisomerase II inhibitor etoposide, which damages DNA. Importantly, proteolysis of MLH1 by caspase-3 triggers its partial redistribution from the nucleus to the cytoplasm and generates a proapoptotic carboxyl-terminal product. In addition, we demonstrate that a caspase-3 cleavage-resistant D418E MLH1 mutant inhibits etoposide-induced apoptosis but has little effect on TRAIL-induced apoptosis. These results indicate that the proteolysis of MLH1 by caspase-3 plays a functionally important and previously unrecognized role in the execution of DNA damage-induced apoptosis.