Mitochondria, apoptosis and the Bcl-2 family

描述（由申请人提供）：Bcl-2家族蛋白在细胞凋亡的控制中起关键作用。特别是，在小鼠中进行的基因靶向研究表明，Bax和巴克（依此类推，可能还有博克）是关键的效应子;在缺乏这些蛋白质的情况下，细胞在许多形式的凋亡中表现出缺陷。我们的重点是这些Bcl-2家族蛋白如何调节线粒体外膜透化（MOMP），在许多细胞死亡途径的主要事件。MOMP导致细胞色素c和其他凋亡触发蛋白从线粒体易位！这些蛋白质反过来调节caspase的激活和凋亡的执行阶段。然而，即使半胱天冬酶是无活性的或不存在的，MOMP仍然似乎通过启动关键线粒体功能的丧失以及活性氧的产生而使大多数细胞死亡。因此，这一过程的调控和机制至关重要。在这里，我们提出的研究，将有助于阐明Bcl-2家族蛋白在MOMP的作用。我们将使用无细胞系统来梳理这些蛋白质的作用机制，以及全细胞和体内方法，这将把这些研究扩展到更生理的背景。Bcl-2家族有三个主要的亚类：“BH 1 -4”蛋白，其是抗凋亡的;“BH 1 -3”蛋白，其包括促凋亡家族成员Bax、巴克和博克，以及“仅BH 3”蛋白，其也是促凋亡的。BH 3-only蛋白的数量更多，在不同的细胞应激条件下通过转录和翻译后机制被特异性激活，并且似乎调节其他两个亚家族。我们的目标，这解决每个类别的Bcl-2家族依次是，首先，探索通过BH 3-唯一的蛋白质调节激活的MOMP型蛋白质的机制;第二，研究膜透化的机制由MOMP型蛋白质;和第三，了解Bcl-xL，BH 1 -4类的成员，可以防止MOMP和MOMP发生后重新密封的MOMP。

DESCRIPTION (provided by applicant): Bcl-2-family proteins play a key role in the control of apoptosis. In particular, gene targeting studies in mice have shown that Bax and Bak (and by analogy, perhaps Bok) are critical effectors; in the absence of these proteins, cells show deficiencies in many forms of apoptosis. Our focus is on how these Bcl-2-family proteins regulate mitochondrial outer membrane permeabilization (MOMP), a primary event in many cell death pathways. MOMP leads to the translocation of cytochrome c and other apoptotic trigger proteins from the mitochondria! inner membrane space into the cytoplasm; these proteins in turn regulate caspase activation and the execution phase of apoptosis. However, even if caspases are inactive or absent, MOMP nevertheless appears to doom most cells to die, through initiating a loss of key mitochondrial functions as well as the generation of reactive oxygen species. Thus, the regulation and mechanism of this process are of critical importance. Here we propose studies that will help elucidate the roles of Bcl-2-family proteins in MOMP. We will use both cell-free systems, to tease apart the mechanisms of action of these proteins, and whole-cell and in vivo approaches, which will extend these investigations to a more physiological context. There are three principal subgroups of the Bcl-2 family: "BH1-4" proteins, which are anti-apoptotic; "BH1-3" proteins, which include the pro-apoptotic family members Bax, Bak and Bok, and the "BH3-only" proteins, which are also pro-apoptotic. The BH3-only proteins are more numerous, are activated specifically through transcriptional and post-translational mechanisms in the context of different cellular stresses, and appear to regulate the other two subfamilies. Our aims, which address each category of the Bcl-2 family in turn, are first, to explore the mechanisms through which the BH3-only proteins regulate the activation of Bax-type proteins; second, to investigate the mechanism of membrane permeabilization by Bax-type proteins; and third, to understand how Bcl-xL, a member of the BH1-4 category, can both prevent MOMP and also reseal the MOM after MOMP has occurred.