An endoplasmic reticulum stress-specific caspase cascade in apoptosis -: Cytochrome c-independent activation of caspase-9 by caspase-12
An endoplasmic reticulum stress-specific caspase cascade in apoptosis -: Cytochrome c-independent activation of caspase-9 by caspase-12
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DOI：
10.1074/jbc.m204973200
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发表时间：
2002-09-13
影响因子：
4.8
通讯作者：
Yasuhiko, Y
中科院分区：
文献类型：
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作者：
Morishima, N;Nakanishi, K;Yasuhiko, Y
从procaspase-12激活caspase-12是通过内质网（ER）的损伤特异性诱导的（Nakagawa， T., Zhu， H., Morishima， N., Li， E., Xu， J., Yankner, b.a ., and Yuan， J. (2000) Nature 403, 98-103），然而caspase-12激活的功能后果尚不清楚。我们已经证明重组caspase-12在细胞质提取物中特异性地切割和激活procaspase-9。激活的caspase-9催化procaspase-3的裂解，而procaspase-3是由caspase-9特异性抑制剂抑制的。虽然线粒体释放的细胞色素c被认为是凋亡过程中caspase-9激活所必需的(邹，H., Henzel， W. J., Liu， X., Lutschg， A., Wang， X. (1997) Cell 90,405 -413, Li， P., Nijhawan， D., Budihardjo， I., Srinivasula， S. M., Ahmad， M., Alnemri， E. S., and Wang， X. (1997) Cell 91,479 -489)， caspase-9以及caspase-12和-3在ER应激下小鼠成肌细胞无细胞色素c的胞浆中被激活。这些结果表明，caspase-12可以在不参与细胞色素c的情况下激活caspase-9。为了研究caspase-12在下游caspase激活中的作用，我们使用了一种caspase-12结合蛋白，我们在酵母双杂交筛选中发现了这种蛋白，用于调节caspase-12的激活。结合蛋白保护procaspase-12免受体外加工。结合蛋白的稳定表达使procaspase-12对内质网应激不敏感，从而抑制细胞凋亡和caspase-9和-3的激活。这些数据表明，procaspase-9是caspase-12的底物，内质网应激以不依赖于细胞色素c的方式触发涉及caspase-12、-9和-3的特异性级联反应。
Activation of caspase-12 from procaspase-12 is specifically induced by insult to the endoplasmic reticulum (ER) (Nakagawa, T., Zhu, H., Morishima, N., Li, E., Xu, J., Yankner, B. A., and Yuan, J. (2000) Nature 403, 98-103), yet the functional consequences of caspase-12 activation have been unclear. We have shown that recombinant caspase-12 specifically cleaves and activates procaspase-9 in cytosolic extracts. The activated caspase-9 catalyzes cleavage of procaspase-3, which is inhibitable by a caspase-9-specific inhibitor. Although cytochrome c released from mitochondria has been believed to be required for caspase-9 activation during apoptosis (Zou, H., Henzel, W. J., Liu, X., Lutschg, A., and Wang, X. (1997) Cell 90, 405-413, Li, P., Nijhawan, D., Budihardjo, I., Srinivasula, S. M., Ahmad, M., Alnemri, E. S., and Wang, X. (1997) Cell 91, 479-489), caspase-9 as well as caspase-12 and -3 are activated in cytochrome c-free cytosols in murine myoblast cells under ER stress. These results suggest that caspase-12 can activate caspase-9 without involvement of cytochrome c. To examine the role of caspase-12 in the activation of downstream caspases, we used a caspase-12-binding protein, which we identified in a yeast two-hybrid screen, for regulation of caspase-12 activation. The binding protein protects procaspase-12 from processing in vitro. Stable expression of the binding protein renders procaspase-12 insensitive to ER stress, thereby suppressing apoptosis and the activation of caspase-9 and -3. These data suggest that procaspase-9 is a substrate of caspase-12 and that ER stress triggers a specific cascade involving caspase-12, -9, and -3 in a cytochrome c-independent manner.