Goping I S, Gross A, Lavoie J N, Nguyen M, Jemmerson R, Roth K, Korsmeyer S J, Shore G C
Department of Biochemistry, McIntyre Medical Sciences Building, McGill University, Montreal, Quebec, Canada H3G 1Y6.
J Cell Biol. 1998 Oct 5;143(1):207-15. doi: 10.1083/jcb.143.1.207.
The proapoptotic protein BAX contains a single predicted transmembrane domain at its COOH terminus. In unstimulated cells, BAX is located in the cytosol and in peripheral association with intracellular membranes including mitochondria, but inserts into mitochondrial membranes after a death signal. This failure to insert into mitochondrial membrane in the absence of a death signal correlates with repression of the transmembrane signal-anchor function of BAX by the NH2-terminal domain. Targeting can be instated by deleting the domain or by replacing the BAX transmembrane segment with that of BCL-2. In stimulated cells, the contribution of the NH2 terminus of BAX correlates with further exposure of this domain after membrane insertion of the protein. The peptidyl caspase inhibitor zVAD-fmk partly blocks the stimulated mitochondrial membrane insertion of BAX in vivo, which is consistent with the ability of apoptotic cell extracts to support mitochondrial targeting of BAX in vitro, dependent on activation of caspase(s). Taken together, our results suggest that regulated targeting of BAX to mitochondria in response to a death signal is mediated by discrete domains within the BAX polypeptide. The contribution of one or more caspases may reflect an initiation and/or amplification of this regulated targeting.
促凋亡蛋白BAX在其COOH末端含有一个预测的单一跨膜结构域。在未受刺激的细胞中，BAX位于细胞质中，并与包括线粒体在内的细胞内膜呈外周性结合，但在死亡信号出现后会插入线粒体膜。在没有死亡信号的情况下无法插入线粒体膜与BAX的NH2末端结构域对跨膜信号锚定功能的抑制有关。通过删除该结构域或用BCL-2的跨膜片段替换BAX的跨膜片段，可以恢复靶向作用。在受刺激的细胞中，BAX的NH2末端的作用与该蛋白插入膜后该结构域的进一步暴露有关。肽基半胱天冬酶抑制剂zVAD-fmk在体内部分阻断了BAX受刺激后的线粒体膜插入，这与凋亡细胞提取物在体外支持BAX的线粒体靶向能力一致，该能力依赖于半胱天冬酶的激活。综上所述，我们的结果表明，响应死亡信号时BAX向线粒体的调节性靶向是由BAX多肽内的离散结构域介导的。一种或多种半胱天冬酶的作用可能反映了这种调节性靶向的起始和/或放大。
