Pörn-Ares M I, Samali A, Orrenius S
Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
Cell Death Differ. 1998 Dec;5(12):1028-33. doi: 10.1038/sj.cdd.4400424.
Calpain activity is thought to be essential for the execution of apoptotic cell death in certain experimental models. In the present study, the physiological inhibitor of calpain, calpastatin, was found to be cleaved in three different apoptotic systems. The 110-120 kDa calpastatin protein of Jurkat T-lymphocytes and U937 monocytic leukemia cells was cleaved to a 65-70 kDa form after the induction of apoptosis with anti-CD95 monoclonal antibody, staurosporine or TNF. Cleavage of calpastatin in apoptotic cells occurred simultaneously with the cleavage of the DNA repair enzyme, poly(ADP-ribose) polymerase. The caspase inhibitors VAD-cmk and IETD-fmk prevented calpastatin cleavage in all three systems. Calpain inhibitor I, however, suppressed calpastatin cleavage only during TNF-induced apoptosis. Other protease inhibitors, such as lactacystin and pepstatin A, did not confer any significant protection against apoptotic calpastatin cleavage. The results from in vitro incubations with cell lysates and purified enzymes showed that calpain I, calpain II and recombinant caspase-3, all cleaved calpastatin, with varying efficiency. In conclusion, the results of the present study suggest that caspases may cleave calpastatin and thus, regulate calpain activity during apoptotic cell death.
在某些实验模型中，钙蛋白酶活性被认为对凋亡性细胞死亡的发生至关重要。在本研究中，发现钙蛋白酶的生理性抑制剂——钙蛋白酶抑制蛋白，在三种不同的凋亡系统中均被裂解。在用抗CD95单克隆抗体、星形孢菌素或肿瘤坏死因子诱导Jurkat T淋巴细胞和U937单核细胞白血病细胞凋亡后，其110 - 120 kDa的钙蛋白酶抑制蛋白被裂解为65 - 70 kDa的形式。凋亡细胞中钙蛋白酶抑制蛋白的裂解与DNA修复酶聚（ADP - 核糖）聚合酶的裂解同时发生。半胱天冬酶抑制剂VAD - cmk和IETD - fmk在所有三种系统中均能阻止钙蛋白酶抑制蛋白的裂解。然而，钙蛋白酶抑制剂I仅在肿瘤坏死因子诱导的凋亡过程中抑制钙蛋白酶抑制蛋白的裂解。其他蛋白酶抑制剂，如乳胞素和胃蛋白酶抑制剂A，对凋亡性钙蛋白酶抑制蛋白的裂解没有显著的保护作用。用细胞裂解物和纯化酶进行体外孵育的结果表明，钙蛋白酶I、钙蛋白酶II和重组半胱天冬酶 - 3均能裂解钙蛋白酶抑制蛋白，但其效率各不相同。总之，本研究结果表明，半胱天冬酶可能裂解钙蛋白酶抑制蛋白，从而在凋亡性细胞死亡过程中调节钙蛋白酶活性。
