Brahmbhatt Hetal, Uehling David, Al-Awar Rima, Leber Brian, Andrews David
Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada, L8S 4L8 Department of Biological Sciences, Sunnybrook Research Institute, University of Toronto, ON, Canada, M4N 3M5.
Drug Discovery Program, Ontario Institute for Cancer Research, Toronto, ON, Canada, M5G 0A3.
Biochem J. 2016 Apr 15;473(8):1073-83. doi: 10.1042/BCJ20160118. Epub 2016 Feb 25.
The pro-apoptotic protein Bax commits a cell to death by permeabilizing the mitochondrial outer membrane (MOM). To obtain small-molecule probes for elucidating the molecular mechanism(s) of Bax activation, we screened for compounds that induced Bax-mediated liposome permeabilization. We identified five structurally different small molecules that promoted both Bax targeting to and oligomerization at membranes. All five compounds initiated Bax oligomerization in the absence of membranes by a mechanism unlike Bax activation by Bcl-2 homology 3 domain (BH3) proteins. Some of the compounds induced Bax/Bak-dependent apoptosis in cells. Activation of Bax by the most active compound was poorly inhibited by the anti-apoptotic protein Bcl-XL and requires a cysteine residue at position 126 of Bax that is not required for activation by BH3 proteins. Our results reveal a novel pathway for Bax activation independent of pro-apoptotic BH3 proteins that may have important implications for the regulation of Bax activity in cells.
促凋亡蛋白Bax通过使线粒体外膜（MOM）通透化，促使细胞走向死亡。为了获得用于阐明Bax激活分子机制的小分子探针，我们筛选了能够诱导Bax介导的脂质体通透化的化合物。我们鉴定出了五种结构不同的小分子，它们既能促进Bax靶向细胞膜，又能促进其在膜上寡聚化。所有这五种化合物在无膜条件下通过一种不同于Bcl-2同源结构域3（BH3）蛋白激活Bax的机制引发Bax寡聚化。其中一些化合物能在细胞中诱导Bax/Bak依赖性凋亡。活性最强的化合物对Bax的激活作用几乎不受抗凋亡蛋白Bcl-XL的抑制，并且需要Bax第126位的半胱氨酸残基，而BH3蛋白激活Bax时不需要该残基。我们的研究结果揭示了一条独立于促凋亡BH3蛋白的Bax激活新途径，这可能对细胞中Bax活性的调控具有重要意义。
