Caspases Are Activated in a Branched Protease Cascade and Control Distinct Downstream Processes in Fas-induced Apoptosis

作者：Hirokazu Hirata, Atsushi Takahashi, Susumu S. Kobayashi, Shin Yonehara, Hirofumi Sawai, Toshiro Okazaki, Kokichi Yamamoto, Masataka Sasada · 发表于：The Journal of Experimental Medicine · 年份：1998 · DOI：10.1084/jem.187.4.587 · 被引用次数：449 · 研究领域：Cell death mechanisms and regulation、RNA Interference and Gene Delivery、Mitochondrial Function and Pathology

Two novel synthetic tetrapeptides, VEID-CHO and DMQD-CHO, could selectively inhibit caspase-6 and caspase-3, respectively. We used these inhibitors to dissect the pathway of caspase activation in Fas-stimulated Jurkat cells and identify the roles of each active caspase in apoptotic processes. Affinity labeling techniques revealed a branched protease cascade in which caspase-8 activates caspase-3 and -7, and caspase-3, in turn, activates caspase-6. Both caspase-6 and -3 have major roles in nuclear apoptosis. Caspase-6 cleaves nuclear mitotic apparatus protein (NuMA) and mediates the shrinkage and fragmentation of nuclei. Caspase-3 cleaves NuMA at sites distinct from caspase-6, and mediates DNA fragmentation and chromatin condensation. It is also involved in extranuclear apoptotic events: cleavage of PAK2, formation of apoptotic bodies, and exposure of phosphatidylserine on the cell surface. In contrast, a caspase(s) distinct from caspase-3 or -6 mediates the disruption of mitochondrial membrane potential (permeability transition) and the shrinkage of cytoplasm. These findings demonstrate that caspases are organized in a protease cascade, and that each activated caspase plays a distinct role(s) in the execution of Fas-induced cell death.