Pastorino J G, Tafani M, Rothman R J, Marcinkeviciute A, Hoek J B, Farber J L
Department of Pathology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
J Biol Chem. 1999 Oct 29;274(44):31734-9. doi: 10.1074/jbc.274.44.31734.
The overexpression of Bax kills cells by a mechanism that depends on induction of the mitochondrial permeability transition (MPT) (Pastorino, J. G., Chen, S.-T., Tafani, M., Snyder, J. W., and Farber, J. L. (1998) J. Biol. Chem. 273, 7770-7775). In the present study, purified, recombinant Bax opened the mitochondrial permeability transition pore (PTP). Depending on its concentration, Bax had two distinct effects. At a concentration of 125 nM, Bax caused the release of the intermembranous proteins cytochrome c and adenylate kinase and the release from the matrix of sequestered calcein, effects prevented by the inhibitor of the PTP cyclosporin A (CSA). At this concentration of Bax, there was no detectable mitochondrial swelling or depolarization. These effects of low Bax concentrations are interpreted as the consequence of transient, non-synchronous activation of the PTP followed by a prompt recovery of mitochondrial integrity. By contrast, Bax concentrations between 250 nM and 1 microM caused a sustained opening of the PTP with consequent persistent mitochondrial swelling and deenergization (the MPT). CSA prevented the MPT induced by Bax. Increasing concentrations of calcium caused a greater proportion of the mitochondria to undergo the MPT in the presence of Bax. Importantly, two known mediators of apoptosis, ceramide and GD3 ganglioside, potentiated the induction by Bax of the MPT. The data imply that Bax mediates the opening of the mitochondrial PTP with the resultant release of cytochrome c from the intermembranous space.
Bax的过表达通过一种依赖于线粒体通透性转换（MPT）诱导的机制杀死细胞（Pastorino，J.G.，Chen，S.-T.，Tafani，M.，Snyder，J.W.，和Farber，J.L.（1998）J.Biol.Chem.273，7770-7775）。在本研究中，纯化的重组Bax打开了线粒体通透性转换孔（PTP）。根据其浓度，Bax有两种不同的作用。在125 nM的浓度下，Bax导致膜间蛋白细胞色素c和腺苷酸激酶的释放以及被隔离的钙黄绿素从基质中的释放，这些作用可被PTP抑制剂环孢菌素A（CSA）阻止。在这个Bax浓度下，没有可检测到的线粒体肿胀或去极化。低浓度Bax的这些作用被解释为PTP短暂、非同步激活后线粒体完整性迅速恢复的结果。相比之下，250 nM至1 μM之间的Bax浓度导致PTP持续开放，随之而来的是持续的线粒体肿胀和能量耗散（MPT）。CSA阻止了Bax诱导的MPT。在Bax存在的情况下，钙浓度的增加导致更大比例的线粒体发生MPT。重要的是，两种已知的凋亡介质神经酰胺和GD3神经节苷脂增强了Bax对MPT的诱导作用。这些数据表明，Bax介导线粒体PTP的开放，从而导致细胞色素c从膜间空间释放。
