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稳态至关重要，影响它们的突变可能导致癌症。 “仅BH 3”分子激活“多结构域”促凋亡成员BAX和巴克以触发依赖于细胞色素C的细胞死亡途径，其释放细胞色素c以激活半胱天冬酶并启动半胱天冬酶非依赖性线粒体功能障碍。 相反，抗凋亡BCL-2/BCL-XL螯合稳定线粒体复合物中的易位的“仅BH 3”分子，从而防止BAX/巴克的活化。 功能丧失研究表明，促凋亡BAX和巴克的缺乏在细胞凋亡中产生了深刻的阻滞，细胞凋亡由在多个位点（包括质膜、细胞核和内质网）启动的不同死亡信号触发。 因此，“多结构域”促凋亡成员BAX或巴克的激活似乎是介导细胞死亡程序的重要途径。 是什么使巴克在线粒体中保持非活性构象，以及它是如何被激活以在细胞死亡中表现出来的，这些都还不清楚。 我推断可能存在另外的死亡调节蛋白，并且已经鉴定了一种BAK相互作用蛋白，该蛋白仅与巴克的无活性构象体相互作用，并且在其被“仅BH 3”分子激活时从巴克置换。 进一步表征这种新的参与者（标题为X）及其确切的影响将进一步了解“BH 3-only”蛋白质如何激活巴克和线粒体死亡途径。 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BAX和巴克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）在调节细胞凋亡中的作用。

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.