Brenner C, Cadiou H, Vieira H L, Zamzami N, Marzo I, Xie Z, Leber B, Andrews D, Duclohier H, Reed J C, Kroemer G
Centre National de la Recherche Scientifique, UPR420, Villejuif, France.
Oncogene. 2000 Jan 20;19(3):329-36. doi: 10.1038/sj.onc.1203298.
Bcl-2 family protein including anti-apoptotic (Bcl-2) or pro-apoptotic (Bax) members can form ion channels when incorporated into synthetic lipid bilayers. This contrasts with the observation that Bcl-2 stabilizes the mitochondrial membrane barrier function and inhibits the permeability transition pore complex (PTPC). Here we provide experimental data which may explain this apparent paradox. Bax and adenine nucleotide translocator (ANT), the most abundant inner mitochondrial membrane protein, can interact in artificial lipid bilayers to yield an efficient composite channel whose electrophysiological properties differ quantitatively and qualitatively from the channels formed by Bax or ANT alone. The formation of this composite channel can be observed in conditions in which Bax protein alone has no detectable channel activity. Cooperative channel formation by Bax and ANT is stimulated by the ANT ligand atractyloside (Atr) but inhibited by ATP, indicating that it depends on the conformation of ANT. In contrast to the combination of Bax and ANT, ANT does not form active channels when incorporated into membranes with Bcl-2. Rather, ANT and Bcl-2 exhibit mutual inhibition of channel formation. Bcl-2 prevents channel formation by Atr-treated ANT and neutralizes the cooperation between Bax and ANT. Our data are compatible with a ménage à trois model of mitochondrial apoptosis regulation in which ANT, the likely pore forming protein within the PTPC, interacts with Bax or Bcl-2 which influence its pore forming potential in opposing manners.
包括抗凋亡成员（Bcl-2）或促凋亡成员（Bax）的Bcl-2家族蛋白整合到合成脂质双层中时可形成离子通道。这与Bcl-2稳定线粒体膜屏障功能并抑制通透性转换孔复合物（PTPC）的观察结果形成对比。在此，我们提供了可能解释这一明显矛盾现象的实验数据。Bax与线粒体内膜中最丰富的蛋白质——腺嘌呤核苷酸转位酶（ANT），可在人工脂质双层中相互作用，产生一种高效的复合通道，其电生理特性在数量和质量上均不同于单独由Bax或ANT形成的通道。在单独的Bax蛋白无明显通道活性的条件下，可观察到这种复合通道的形成。Bax与ANT协同形成通道受到ANT配体苍术苷（Atr）的刺激，但受到ATP的抑制，这表明其依赖于ANT的构象。与Bax和ANT的组合不同，ANT与Bcl-2一起整合到膜中时不会形成活性通道。相反，ANT和Bcl-2表现出对通道形成的相互抑制作用。Bcl-2可阻止经Atr处理的ANT形成通道，并消除Bax与ANT之间的协同作用。我们的数据与线粒体凋亡调控的三角关系模型相符，在该模型中，PTPC内可能的成孔蛋白ANT与Bax或Bcl-2相互作用，它们以相反的方式影响ANT的成孔潜力。
