Proteolytic Processing of the Caspase-9 Zymogen Is Required for Apoptosome-mediated Activation of Caspase-9
Proteolytic Processing of the Caspase-9 Zymogen Is Required for Apoptosome-mediated Activation of Caspase-9
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Caspase-9 酶原的蛋白水解加工是凋亡体介导的 Caspase-9 激活所必需的
DOI：
10.1074/jbc.m112.441568
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发表时间：
2013-05-24
影响因子：
4.8
通讯作者：
Shi, Yigong
中科院分区：
文献类型：
--
作者：
Hu, Qi;Wu, Di;Shi, Yigong
在细胞凋亡开始时，Apaf-1 凋亡体介导单链 caspase-9 酶原通过自蛋白水解过程成熟。加工后的 caspase-9 和凋亡体形成全酶，具有强大的蛋白水解活性，比游离的加工后的 caspase-9 高 2-3 个数量级。一个尚未解决的重要问题是 caspase-9 加工的作用，一些实验数据表明它是可有可无的。在本研究中，我们证明，与野生型 caspase-9 相比，未加工的单链 caspase-9 三重突变体 E306A/D315A/D330A (Casp9-TM) 无法再被凋亡体充分激活。与野生型caspase-9的蛋白酶活性相比，在凋亡体存在下Casp9-TM的蛋白酶活性显着降低。在凋亡体存在下，Casp9-TM 的蛋白酶活性减弱可能是由于 Casp9-TM 形成同二聚体的能力显着降低。这些数据确定了 caspase-9 的自蛋白水解加工在其激活过程中的重要作用。
Maturation of the single-chain caspase-9 zymogen through autoproteolytic processing is mediated by the Apaf-1 apoptosome at the onset of apoptosis. Processed caspase-9 and the apoptosome form a holoenzyme with robust proteolytic activity that is 2-3 orders of magnitude higher than that of free processed caspase-9. An unresolved important question is the role of caspase-9 processing, with some experimental data suggesting its dispensability. In this study, we demonstrate that, in contrast to wild-type caspase-9, the unprocessed single-chain caspase-9 triple mutant E306A/D315A/D330A (Casp9-TM) could no longer be adequately activated by the apoptosome. Compared with the protease activity of wild-type caspase-9, that of Casp9-TM in the presence of the apoptosome was drastically reduced. The crippled protease activity of Casp9-TM in the presence of the apoptosome is likely attributable to a markedly reduced ability of Casp9-TM to form homodimers. These data identify an essential role for the autoproteolytic processing of caspase-9 in its activation.