Dorstyn Loretta, Read Stuart, Cakouros Dimitrios, Huh Jun R, Hay Bruce A, Kumar Sharad
Hanson Centre for Cancer Research, Institute of Medical and Veterinary Science, Adelaide SA 5000, Australia.
J Cell Biol. 2002 Mar 18;156(6):1089-98. doi: 10.1083/jcb.200111107.
The release of cytochrome c from mitochondria is necessary for the formation of the Apaf-1 apoptosome and subsequent activation of caspase-9 in mammalian cells. However, the role of cytochrome c in caspase activation in Drosophila cells is not well understood. We demonstrate here that cytochrome c remains associated with mitochondria during apoptosis of Drosophila cells and that the initiator caspase DRONC and effector caspase DRICE are activated after various death stimuli without any significant release of cytochrome c in the cytosol. Ectopic expression of the proapoptotic Bcl-2 protein, DEBCL, also fails to show any cytochrome c release from mitochondria. A significant proportion of cellular DRONC and DRICE appears to localize near mitochondria, suggesting that an apoptosome may form in the vicinity of mitochondria in the absence of cytochrome c release. In vitro, DRONC was recruited to a >700-kD complex, similar to the mammalian apoptosome in cell extracts supplemented with cytochrome c and dATP. These results suggest that caspase activation in insects follows a more primitive mechanism that may be the precursor to the caspase activation pathways in mammals.
细胞色素c从线粒体的释放对于哺乳动物细胞中Apaf-1凋亡小体的形成及随后的半胱天冬酶-9的激活是必要的。然而，细胞色素c在果蝇细胞半胱天冬酶激活中的作用尚不清楚。我们在此证明，在果蝇细胞凋亡过程中细胞色素c仍与线粒体相关联，并且起始半胱天冬酶DRONC和效应半胱天冬酶DRICE在各种死亡刺激后被激活，而细胞色素c在细胞质中没有任何显著释放。促凋亡Bcl-2蛋白DEBCL的异位表达也未显示细胞色素c从线粒体中释放。相当一部分细胞中的DRONC和DRICE似乎定位于线粒体附近，这表明在没有细胞色素c释放的情况下，凋亡小体可能在线粒体附近形成。在体外，在补充了细胞色素c和dATP的细胞提取物中，DRONC被募集到一个大于700-kD的复合物中，类似于哺乳动物的凋亡小体。这些结果表明，昆虫中的半胱天冬酶激活遵循一种更原始的机制，可能是哺乳动物半胱天冬酶激活途径的前身。
