Regulation of BAX/BAK-Dependent Cell Death

描述（由申请人提供）：BCL-2蛋白家族，包括抗凋亡和促凋亡成员，构成细胞死亡途径中的关键检查点。这些成员对维持主要器官的稳态至关重要，影响它们的突变可能导致癌症。“仅bh3”分子激活“多结构域”促凋亡成员BAX和BAK，触发线粒体依赖的细胞死亡途径，释放细胞色素c激活caspase并启动caspase非依赖性线粒体功能障碍。相反，抗凋亡的BCL-2/BCL-XL在稳定的线粒体复合体中隔离易位的“仅bh3”分子，从而阻止BAX/BAK的激活。功能丧失研究表明，促凋亡的BAX和BAK的缺失会严重阻碍由质膜、细胞核和内质网等多个部位启动的多种死亡信号引发的细胞凋亡。因此，“多结构域”促凋亡成员BAX或BAK的激活似乎是线粒体介导的细胞死亡程序的重要门户。是什么使BAK在线粒体中保持非活性构象，以及它是如何被激活并在细胞死亡中表现出来的，目前尚不清楚。我推断可能存在一种额外的死亡调节蛋白，并确定了一种仅与BAK的非活性构象相互作用的BAK相互作用蛋白，并在BAK被“仅bh3”分子激活时从BAK中移位。对这种新参与者（名为X）的进一步表征及其确切影响将进一步了解“仅bh3”蛋白如何激活BAK和线粒体死亡途径。在此背景下，我提出以下具体目标：(1)分析“多结构域”促凋亡BAX和BAK介导线粒体功能障碍和细胞死亡的机制；(2)确定bak相互作用蛋白(X)在调控细胞凋亡中的作用。

DESCRIPTION (provided by applicant): The BCL-2 family of proteins, consisting of both anti-apoptotic and pro-apoptotic members, constitutes a crucial checkpoint in the cell death pathway. These members are essential for maintenance of major organ homeostasis, and mutations affecting them can result in cancer. The "BH3-only" molecules activate "multi-domain" pro-apoptotic members BAX and BAK to trigger a mitochondrion-dependent cell death pathway, which both releases cytochrome c to activate caspases and initiates caspase-independent mitochondrial dysfunction. Conversely, anti-apoptotic BCL-2/BCL-XL sequesters translocated "BH3-only" molecules in stable mitochondrial complexes, thus preventing the activation of BAX/BAK. Loss of function studies revealed that the absence of pro-apoptotic BAX and BAK creates a profound block in apoptosis triggered by diverse death signals initiated at multiple sites including plasma membrane, nucleus, and endoplastic reticulum. Thus, activation of a "multidomain" pro-apoptotic member, BAX or BAK, appears to be an essential gateway to the mitochondria-mediated cell death program. What maintains BAK in an inactive conformation at mitochondria and precisely how it is activated to manifest in cell death are still unclear. I reasoned that an additional death regulatory protein might exist and have identified a BAK-interacting protein that only interacts with the inactive conformer of BAK and is displaced form BAK upon its activation by "BH3-only" molecules. Further characterization of this novel participant (entitled X) and its precise effects will further understanding of how "BH3-only" proteins activate BAK and the mitochondrial death pathway. In this context, I propose the following specific aims: (1) Dissect the mechanisms by which "multidomain" pro-apoptotic BAX and BAK mediate mitochondrial dysfunction and cell death; (2) Determine the role of BAK-interacting protein (X) in regulating apoptosis.