Bax BH3结构域的多肽链(H2-H3)通过抑制Bcl-2的成孔和中和Bcl-2的抗Bax作用而引起细胞凋亡

The Bax BH3 Peptide H2-H3 Promotes Apoptosis by Inhibiting Bcl-2's Pore-forming and Anti-Bax Activities in the Membrane

成孔和蛋白间的相互作用在Bcl-2家族对凋亡的调节过程中起着重要的作用。促凋亡蛋白Bax和抗凋亡蛋白Bcl-2通过在线粒体外膜上形成不同的孔来调节膜的通透性。Bcl-2的过度表达与许多肿瘤的发生密切相关,因此研制能抑制Bcl-2功能的小分子化合物一直是抗肿瘤研究领域的一个重点。由于Bax可以通过其BH3结构域和Bcl-2结合,继而抑制Bcl-2的抗凋亡功能;所以来源于Bax BH3结构域的多肽链(H2-H3)被认为是Bcl-2的拮抗剂。我们最近发现,H2-H3能够激活Bax以及抑制Bcl-2的抗Bax作用,从而诱导细胞色素C的释放和细胞凋亡;但其中的分子机制尚未完全阐明。本文通过对Bcl-2和Bax在脂质体膜上成孔过程的研究,发现:H2-H3可以抑制Bcl-2的成孔;并且可以中和Bcl-2对Bax成孔的抑制作用。造成H2-H3促凋亡功能丧失的点突变同样也会造成H2-H3对Bcl-2的抑制作用。因此本文的研究结果提示:H2-H3的促凋亡功能与其抑制Bcl-2的成孔和中和Bcl-2的抗Bax作用有关。

Pore-formation and protein-protein interactions are considered to play critical roles in the regulation of apoptosis by Bcl-2 family proteins. During the initiation of apoptosis, the anti-apoptotic Bcl-2 and the pro-apoptotic Bax form different pores to regulate the permeability of mitochondrial outer membrane, playing their opposite functions. Overexpression of Bcl-2 has been found in various cancer cells, therefore it is gaining widespread interest to discover small molecules to compromise Bcl- 2 function for anti-cancer treatment. Since Bax binds to Bcl-2＇s hydrophobic groove via its BH3 domain （composed of helices 2 and 3）, by which their functions are inhibited each other, the H2-H3 peptide that contains the functional BH3 domain of Bax has been considered as a potential Bcl-2 antagonist. We recently reported that Bax peptide H2-H3 promotes ceil death by inducing Bax-mediated cytochrome c release and by antagonizing Bcl-2＇s inhibitory effect on Bax. However, the mechanism of how H2-H3 inhibits the anti-apoptotic activity of Bcl-2 remains poorly understood. To address this question, we reconstituted the Bcl-2 or Bax pore-forming process in vitro. We found that H2-H3 inhibited Bcl-2＇s pore formation and neutralized Bcl-2＇s inhibitory effect on Bax pore formation in the membrane, whereas the mutant H2-H3 peptide that does not induce apoptosis in cells was shown to have no effect on Bcl-2% activities. Thus, inhibiting Bcl-2% pore-forming and anti-Bax activities in the membrane is strongly correlated with H2-H3＇s pro-apoptosis function in cells.