Target protease specificity of the viral serpin CrmA - Analysis of five caspases
Target protease specificity of the viral serpin CrmA - Analysis of five caspases
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DOI：
10.1074/jbc.272.12.7797
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发表时间：
1997-03-21
影响因子：
4.8
通讯作者：
Salvesen, GS
中科院分区：
文献类型：
--
作者：
Zhou, Q;Snipas, S;Salvesen, GS
当牛痘病毒的产物细胞因子反应修饰因子A （CrmA）在动物细胞中异位表达时，可防止由各种刺激引起的程序性细胞死亡。由于CrmA是一种蛋白酶抑制剂，其靶标可能是促进细胞死亡的蛋白酶。我们比较了CrmA与5种可能在细胞凋亡中起作用的蛋白酶的相互作用动力学，其中4种蛋白酶，都是caspase家族的成员，以不同的速率和亲和度被抑制，范围超过5个数量级，1种在实验条件下完全不受抑制。CrmA在抑制caspase方面具有很强的选择性，对白细胞介素-1 β转换酶的亲和力最高，对caspase FLICE的亲和力第二高（K-i = 0.95 nM），被鉴定为连接死亡受体Fas募集的细胞内信号复合体的一个组成部分。基于比较抑制剂动力学，我们提出CrmA不太可能抑制caspases Yama， Mch2，但其对FLICE的抑制作用对于该蛋白酶在fas介导的细胞凋亡过程中成为CrmA的关键靶点具有重要意义。因此，我们的研究结果支持了FLICE催化促进细胞死亡的关键步骤的假设。
When ectopically expressed in animal cells, cytokine response modifier A (CrmA), a product of the cowpox virus, prevents programmed cell death initiated by a variety of stimuli, Since CrmA is a proteinase inhibitor, its target is probably a protease that promotes cell death. The identification of this target is crucial in delineating essential regulation points that modulate the apoptotic program, We have compared the kinetics of interaction of CrmA with five proteases that may play a role in apoptosis, Four of the proteases, all members of the caspase family, are inhibited with widely different rates and affinities ranging over 5 orders of magnitude, One is not inhibited at all under the experimental conditions, CrmA is quite selective in its ability to inhibit caspases, showing the highest affinity for interleukin-1 beta-converting enzyme and the second highest for the caspase FLICE (K-i = 0.95 nM), identified as a component of the intracellular signaling complex recruited by ligation of the death receptor Fas, On the basis of comparative inhibitor kinetics, we propose that CrmA is unlikely to inhibit the caspases Yama, Mch2, or LAP3 in vivo but that its inhibition of FLICE is of a magnitude for this protease to be a key target of CrmA during Fas-mediated apoptosis, Therefore, our results support the hypothesis that FLICE catalyzes a crucial step in the promotion of cell death.