Departamento de Fisiología, Biología Celular, Instituto Nacional de Cardiología, "Ignacio Chávez", Juan Badiano No. 1., Col. Sección XVI, México DF, 14080, Mexico.
J Bioenerg Biomembr. 2013 Oct;45(5):441-8. doi: 10.1007/s10863-013-9508-x. Epub 2013 Mar 28.
Bax, a pro-apoptotic member of the Bcl-2 family of proteins has the ability to form transmembrane pores large enough to allow cytochrome c (Cyt c) release, as well as to activate the mitochondrial permeability transition pore (mPTP); however, no differential study has been conducted to clarify which one of these mechanisms predominates over the other in the same system. In the present study, we treated isolated mitochondria from MCF7 cells with recombinant protein Bax and tested the efficacy of the mPTP inhibitor cyclosporin A (CsA) and of the Bax channel blocker (Bcb) to inhibit cytochrome c release. We also, induced apoptosis in MCF7 cell cultures with TNF-α plus cycloheximide to determine the effect of such compounds in apoptosis induction via mPTP or Bax oligomerization. Cytochrome c release was totally prevented by CsA and partially by Bcb when apoptosis was induced with recombinant Bax in isolated mitochondria from MCF7 cells. CsA increased the number of living cells in cell culture, as compared with the effect of Bax channel blocker. These results indicate that mPTP activation is the predominant pathway for Bax-induced cytochrome c release from MCF7 mitochondria and for apoptosis induction in the whole cell.
Bax 是 Bcl-2 家族蛋白中的一种促凋亡蛋白，它能够形成足够大的跨膜孔，允许细胞色素 c（Cyt c）释放，并激活线粒体通透性转换孔（mPTP）；然而，目前还没有进行差异化研究来阐明在同一系统中哪种机制占主导地位。在本研究中，我们用重组蛋白 Bax 处理 MCF7 细胞分离的线粒体，并测试 mPTP 抑制剂环孢素 A（CsA）和 Bax 通道阻滞剂（Bcb）抑制细胞色素 c 释放的效果。我们还通过 TNF-α和环磷酰胺诱导 MCF7 细胞培养物中的细胞凋亡，以确定这些化合物通过 mPTP 或 Bax 寡聚化诱导细胞凋亡的效果。当用重组 Bax 在 MCF7 细胞分离的线粒体中诱导细胞色素 c 释放时，CsA 完全阻止了细胞色素 c 的释放，而 Bcb 部分阻止了细胞色素 c 的释放。与 Bax 通道阻滞剂的作用相比，CsA 增加了细胞培养物中活细胞的数量。这些结果表明，mPTP 的激活是 Bax 诱导 MCF7 线粒体细胞色素 c 释放和整个细胞凋亡诱导的主要途径。
