Mori Shunsuke, Murakami-Mori Kaoru, Nakamura Shuji, Bonavida Benjamin
Department of Microbiology, Immunology, and Molecular Genetics, UCLA School of Medicine, University of California, Los Angeles, CA 90095, USA.
Int J Oncol. 2002 Apr;20(4):819-26.
Fas engagement rapidly induces formation of the death-inducing signaling complex (DISC) that consists of Fas, FADD and pro-caspase-8. Activated caspase-8 at the DISC directly activates downstream caspases, resulting in induction of apoptosis of the independent mitochondria. In this study, we have obtained evidence demonstrating that Fas-mediated apoptosis in AIDS-KS cells takes place in a mitochondria-dependent manner. FADD and pro-caspase-8 were detected in immunoprecipitates with anti-Fas antibody in anti-Fas mAb (CH-11)-treated Hut 78, a typical Fas-sensitive cell line. On the other hand, DISC formation by CH-11 was markedly reduced in AIDS-KS cells. In addition, CH-11-induced activation of caspase-8-like protease in AIDS-KS cells was much less pronounced compared with that in Hut 78; however, a caspase-8 inhibitor, zIETD-fmk, completely blocked the apoptosis. Further, a caspase-9 inhibitor, zLEHD-fmk, markedly inhibited Fas-mediated apoptosis in AIDS-KS cells. Several apoptotic stimuli induce mitochondria activation allowing cytochrome c release from the mitochondria. In the apoptosome, cytochrome c and Apaf-1 activate caspase-9 which subsequently leads to the activation of caspase-3. In AIDS-KS cells, CH-11 triggered cytochrome c release, an event which was inhibited by zIETD-fmk. Further, a caspase-3 inhibitor, zDEVD-fmk completely inhibited the apoptosis. Altogether, the present data provide evidence that the Fas signal in AIDS-KS cells is preferentially transduced through the mitochondria-dependent pathway, which is initiated by caspase-8 activation.
Fas激活迅速诱导死亡诱导信号复合物（DISC）的形成，该复合物由Fas、FADD和前体半胱天冬酶-8组成。DISC处激活的半胱天冬酶-8直接激活下游半胱天冬酶，导致独立线粒体凋亡的诱导。在本研究中，我们获得的证据表明，艾滋病相关卡波西肉瘤（AIDS-KS）细胞中Fas介导的凋亡以线粒体依赖的方式发生。在用抗Fas单克隆抗体（CH-11）处理的典型Fas敏感细胞系Hut 78中，用抗Fas抗体在免疫沉淀物中检测到FADD和前体半胱天冬酶-8。另一方面，CH-11在AIDS-KS细胞中诱导的DISC形成明显减少。此外，与Hut 78相比，CH-11在AIDS-KS细胞中诱导的类半胱天冬酶-8蛋白酶激活明显较弱；然而，一种半胱天冬酶-8抑制剂zIETD-fmk完全阻断了凋亡。此外，一种半胱天冬酶-9抑制剂zLEHD-fmk显著抑制了AIDS-KS细胞中Fas介导的凋亡。几种凋亡刺激可诱导线粒体激活，使细胞色素c从线粒体释放。在凋亡小体中，细胞色素c和凋亡蛋白酶激活因子-1激活半胱天冬酶-9，随后导致半胱天冬酶-3的激活。在AIDS-KS细胞中，CH-11触发了细胞色素c的释放，这一事件被zIETD-fmk抑制。此外，一种半胱天冬酶-3抑制剂zDEVD-fmk完全抑制了凋亡。总之，目前的数据提供了证据，表明AIDS-KS细胞中的Fas信号优先通过由半胱天冬酶-8激活引发的线粒体依赖途径进行转导。
