Apoptotic Network Integrated at the Mitochondrion

描述（由申请人提供）：细胞凋亡在多细胞生物体内稳态的发展和维持中起重要作用。细胞凋亡的损伤不仅是癌症发展的核心，而且使肿瘤对细胞毒性疗法难以治疗。BCL-2家族蛋白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。我们先前的研究有助于描绘哺乳动物的核心凋亡途径。仅BH 3分子激活多结构域促凋亡BAX和巴克以释放细胞色素c用于半胱天冬酶激活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将仅BH 3的分子隔离到惰性复合物中，从而防止BAX和巴克的活化。遗传学研究表明，促凋亡BAX和巴克的缺乏在由包括癌症治疗剂在内的多种死亡信号触发的细胞凋亡中产生了深刻的阻断。因此，多结构域成员BAX或巴克的激活似乎是启动子介导的细胞死亡程序的必经之路。然而，目前尚不清楚是否所有的仅BH 3分子都能够激活BAX和巴克，仅BH 3分子如何激活BAX和巴克，以及哪种仅BH 3分子以及它如何被每个特定的死亡信号激活以启动凋亡信号级联。新出现的证据表明，抗凋亡BCL-2成员被不同的仅含BH 3的分子选择性地灭活，但是单个仅含BH 3的分子在拮抗抗凋亡BCL-2成员中的详细功能图仍然缺失。此外，抗凋亡BCL-2成员是否通过直接抑制BAX/巴克和/或螯合仅BH 3分子来抑制凋亡仍有争议。最后，确定BAX和巴克如何在活细胞中保持检查是至关重要的。它们是否受到抗凋亡BCL-2成员或其他相关蛋白（如VDAC 2）的控制？为了解决这些问题，我们建议表征BH 3-only分子，分配和鉴定单个BH 3-only分子以整合凋亡信号级联和依赖于细胞因子的死亡程序，剖析BH 3-only分子激活BAX和巴克的机制，并建立不同BCL-2亚家族之间差异调节的功能网络。我们的最终目标是将BCL-2家族的死亡/生存决定机制转化为抗癌策略。

DESCRIPTION (provided by applicant): Apoptosis plays an essential role in the development and maintenance of homeostasis within multicellular organisms. Impairment of apoptosis is not only central to cancer development but also renders tumors refractory to cytotoxic therapy. The BCL-2 family proteins, consisting of both anti-apoptotic and proapoptotic members, constitute a crucial checkpoint in the cell death pathway. Our prior studies have helped delineate the core apoptotic pathway in mammals. The BH3-only molecules activate multidomain proapoptotic BAX and BAK to releases cytochrome c for caspase activation and initiate caspase-independent mitochondrial dysfunction. Conversely, anti-apoptotic BCL-2/BCL-XL sequesters BH3-only molecules into inert complexes, thus preventing the activation of BAX and BAK. Genetic studies revealed that absence of proapoptotic BAX and BAK creates a profound block in apoptosis triggered by diverse death signals including cancer therapeutics. Thus, activation of a multidomain member, BAX or BAK, appears to be an obligate gateway to the mitochondrion-mediated cell death program. However, it remains unclear whether all the BH3-only molecules are capable of activating BAX and BAK, how the BH3-only molecules activate BAX and BAK, and which BH3-only molecule and how it is activated by each specific death signal to initiate the apoptotic signaling cascade. Emerging evidence suggests that anti-apoptotic BCL-2 members are selectively inactivated by different BH3-only molecules, but detailed functional map of individual BH3-only molecules in antagonizing anti-apoptotic BCL-2 members is still missing. Moreover, it remains debated whether anti- apoptotic BCL-2 members inhibit apoptosis through direct inhibition of BAX/BAK and/or sequestration of BH3-only molecules. Finally, it is critical to determine how BAX and BAK are kept in check in viable cells. Are they kept in check by anti-apoptotic BCL-2 members or by other associated proteins such as VDAC2? To address these questions, we propose to characterize the BH3-only molecules, assign and identify individual BH3-only molecules to integrate apoptotic signaling cascades and mitochondrion-dependent death program, dissect the mechanisms by which BH3-only molecules activate BAX and BAK, and establish a functional network of differential regulation among various BCL-2 subfamilies. Our ultimate goal is to translate the mechanisms governing death/survival decision by BCL-2 family into anti-cancer strategies.