Suzuki A, Tsutomi Y, Akahane K, Araki T, Miura M
Drug Safety Research Laboratory, Daiichi Pharmaceutical Co., Ltd., Tokyo R&D Center, Japan.
Oncogene. 1998 Aug 27;17(8):931-9. doi: 10.1038/sj.onc.1202021.
The death receptor Fas transduces apoptotic death signaling mediated by caspases. In the present study, human hepatoma HepG2 cells showed the Fas-mediated apoptosis mediated by caspase, especially caspase 3, only in the presence of actinomycin D. Interestingly, cytosolic proteins extracted from intact HepG2 cells induced caspase 3 inactivation. Our results reveal that this inactivation was triggered by the direct inhibition of activated caspase 3 by IAP gene family ILP. In addition, a 53 kDa protein was co-immunoprecipitated with anti-human caspase 3 antibody from intact HepG2 cells. This protein was a complex-protein of procaspase 3 and the cell cycle regulator p21WAF1 (p21). P21 bound to only procaspase 3, but not to activated caspase 3. We also demonstrate that p21 protein-loaded HepG2 cells resist to Fas-mediated apoptosis even in the presence of actinomycin D. Here we report that caspase 3 inactivation for the resistance to Fas-mediated apoptosis is induced by a procaspase 3/p21 complex formation and direct inhibition of activated caspase 3 by ILP.
死亡受体Fas转导由半胱天冬酶介导的凋亡死亡信号。在本研究中，人肝癌HepG2细胞仅在放线菌素D存在的情况下才显示出由半胱天冬酶介导的Fas介导的凋亡，尤其是半胱天冬酶-3。有趣的是，从完整的HepG2细胞中提取的胞质蛋白可诱导半胱天冬酶-3失活。我们的结果表明，这种失活是由IAP基因家族ILP对活化的半胱天冬酶-3的直接抑制所触发的。此外，用抗人半胱天冬酶-3抗体从完整的HepG2细胞中共免疫沉淀出一种53 kDa的蛋白质。该蛋白质是前半胱天冬酶-3与细胞周期调节因子p21WAF1（p21）的复合蛋白。P21仅与前半胱天冬酶-3结合，而不与活化的半胱天冬酶-3结合。我们还证明，即使在放线菌素D存在的情况下，加载p21蛋白的HepG2细胞也能抵抗Fas介导的凋亡。我们在此报告，对半胱天冬酶-3的失活以抵抗Fas介导的凋亡是由前半胱天冬酶-3/p21复合物的形成以及ILP对活化的半胱天冬酶-3的直接抑制所诱导的。
