Regulation of BAX/BAK-Dependent Cell Death

描述(由申请人提供)：bcl-2蛋白家族，由抗凋亡和促凋亡成员组成，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动态平衡是必不可少的，影响它们的突变可能导致癌症。“仅BH3”分子激活“多域”促凋亡成员Bax和BAK，触发线粒体依赖的细胞死亡途径，这两个途径都释放细胞色素c来激活caspase，并启动caspase非依赖性线粒体功能障碍。相反，抗凋亡的bcl2/bclxl隔离物使稳定的线粒体复合体中的“仅BH3”分子移位，从而阻止Bax/BAK的激活。功能丧失研究表明，促凋亡的Bax和BAK的缺失在细胞凋亡中造成了深刻的障碍，这些死亡信号在包括质膜、细胞核和内质网在内的多个部位启动了不同的死亡信号。因此，激活一个“多结构域”的促凋亡成员BAX或BAK，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在线粒体上保持不活跃的构象，以及它到底是如何被激活并在细胞死亡中表现出来的，目前尚不清楚。我推测可能存在另一种死亡调节蛋白，并发现了一种与BAK相互作用的蛋白，这种蛋白只与BAK的非活性构象相互作用，当BAK被“只有BH3”分子激活时，它就被取代了。对这个新的参与者(名为X)及其精确影响的进一步表征将进一步了解“仅BH3-”蛋白质如何激活BAK和线粒体死亡途径。在此背景下，我提出了以下具体目标：(1)剖析“多结构域”促凋亡的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.