Gelles Jesse D, Chen Yiyang, Luna-Vargas Mark P A, Follis Ariele Viacava, Bayiokos Stella G, Mohammed Jarvier N, Sebastian Tara M, Al Noman M Abdullah, Pham Ngoc Dung, Shi Yi, Kriwacki Richard W, Chipuk Jerry E
Laboratory of Mitochondrial Biology in Human Health and Disease, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, New York 10029, USA.
Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, New York 10029, USA.
bioRxiv. 2024 Dec 23:2024.12.23.630122. doi: 10.1101/2024.12.23.630122.
Mitochondria maintain a biochemical environment that cooperates with BH3-only proteins (e.g., BIM) to potentiate BAX activation, the key event to initiate physiological and pharmacological forms of apoptosis. The sphingosine-1-phosphate metabolite 2-trans-hexadecenal (2t-hexadecenal) is one such component described to support BAX activation, but molecular mechanisms remain largely unknown. Here, we utilize complementary biochemical and biophysical techniques to reveal that 2t-hexadecenal non-covalently interacts with BAX, and cooperates with BIM to stimulate early-activation steps of monomeric BAX. Integrated structural and computational approaches reveal 2t-hexadecenal binds an undefined region - a hydrophobic cavity formed by core-facing residues of α5, α6, and gated by α8 - we now term the "BAX actuating funnel" (BAF). We define alkenal length and α8 mobility as critical determinants for 2t-hexadecenal synergy with BIM and BAX, and demonstrate that proline 168 allosterically regulates BAF function. Collectively, this work imparts detailed molecular insights advancing our fundamental knowledge of BAX regulation and identifies a regulatory region with implications for biological and therapeutic opportunities.
线粒体维持着一种生化环境，该环境与仅含BH3结构域的蛋白（如BIM）协同作用，以增强BAX的激活，这是启动生理性和药物性凋亡形式的关键事件。鞘氨醇-1-磷酸代谢物2-反式-十六碳烯醛（2t-十六碳烯醛）就是这样一种被描述为支持BAX激活的成分，但其分子机制仍 largely未知。在这里，我们利用互补的生化和生物物理技术揭示，2t-十六碳烯醛与BAX非共价相互作用，并与BIM协同刺激单体BAX的早期激活步骤。综合的结构和计算方法揭示，2t-十六碳烯醛结合一个未定义区域——由α5、α6面向核心的残基形成并由α8门控的疏水腔——我们现在将其称为“BAX激活漏斗”（BAF）。我们将烯醛长度和α8的流动性定义为2t-十六碳烯醛与BIM和BAX协同作用的关键决定因素，并证明脯氨酸168变构调节BAF功能。总的来说，这项工作提供了详细的分子见解，推进了我们对BAX调节的基础知识，并确定了一个对生物学和治疗机会有影响的调节区域。
