Mechanisms of Bax Activation in Apoptosis

Bax 激活在细胞凋亡中的机制

• 批准号: 7140128
• 负责人: BIN GUO
• 金额: $ 11.97万
• 依托单位: NORTH DAKOTA STATE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-09-01 至 2008-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7140128
• 关键词: Bax gene /protein; apoptosis; biological signal transduction; cell line; cytochrome c; fluorescence polarization; gene deletion mutation; gene expression; genetic regulation; immunoprecipitation; liver cells; mitochondria; monoclonal antibody; neoplastic cell; p53 gene /protein; peptides; phosphorylation; protein binding; protein protein interaction; protein transport; small interfering RNA; transfection /expression vector

DESCRIPTION (provided by applicant): Bax is one of the two key proteins (Bax and Bak) of the Bcl-2 family that control the mitochondrial pathway of apoptosis. In healthy cells, Bax locates in the cytosol and is maintained in the inactive state. The C-termina! transmembrane (TM) domain of Bax, which is responsible for mitochondria targeting, is folded into a hydrophobic pocket on the Bax protein. Apoptotic signals induce conformational changes of the Bax protein and releases the TM domain from the pocket. The activated form of Bax protein migrates to mitochondria. [After insertion into mitochondrial outer membrane, Bax induces the release of pro-apoptotic proteins from mitochondria (cytochrome c, Smac, AIF, etc.) and disruption of mitochondrial membrane potential. These events lead to activation of caspases and apoptotic cell death. The mechanism that maintains Bax in its inactive state in healthy cells is not known until recently we and another group have identified the proteins (Humanin and other proteins) that bind to and suppress Bax activation. However, the mechanism by which apoptotic stimuli release Humanin from Bax and activate Bax remains unknown. We hypothesize that apoptotic stimuli activate unknown protein factor(s) that binds to or modify Bax-Humanin complex, causing the release of Humanin and the activation of Bax. Consequently, the specific aims of this proposal are: 1) To identify the protein factor(s) that activates Bax in response to apoptotic stimuli; 2)To investigate the physiological function of the identified Bax activating factor(s) in apoptosis. The Bax activating proteins will be identified by biochemical fractionation of cytosolic preparation from apoptotic cells. The physiological function of the identified Bax activating proteins will be investigated by overexpression in cancer cells through transfection and by knocking-down their expression using siRNA technique. These studies will help improve our knowledge on the mechanism of Bax activation, a critical decision-making process in apoptosis.

描述（由申请人提供）：Bax 是控制线粒体凋亡途径的 Bcl-2 家族的两个关键蛋白（Bax 和 Bak）之一。在健康细胞中，Bax 位于细胞质中并保持非活性状态。 C端！ Bax 的跨膜 (TM) 结构域负责线粒体靶向，折叠到 Bax 蛋白上的疏水口袋中。凋亡信号诱导 Bax 蛋白的构象变化，并从口袋中释放 TM 结构域。 Bax 蛋白的激活形式迁移至线粒体。 [插入线粒体外膜后，Bax 诱导线粒体释放促凋亡蛋白（细胞色素 c、Smac、AIF 等）并破坏线粒体膜电位。这些事件导致半胱天冬酶激活和细胞凋亡。在健康细胞中维持 Bax 处于非活性状态的机制尚不清楚，直到最近我们和另一个小组鉴定了结合并抑制 Bax 激活的蛋白质（胡曼素和其他蛋白质）。然而，凋亡刺激从 Bax 中释放护脑素并激活 Bax 的机制仍不清楚。我们假设细胞凋亡刺激会激活结合或修饰 Bax-Humanin 复合物的未知蛋白因子，导致 Humanin 的释放和 Bax 的激活。因此，该提案的具体目标是： 1) 鉴定响应细胞凋亡刺激而激活 Bax 的蛋白质因子； 2)研究已鉴定的Bax激活因子在细胞凋亡中的生理功能。 Bax 激活蛋白将通过对凋亡细胞的胞质制剂进行生化分级来鉴定。将通过转染在癌细胞中过度表达并使用 siRNA 技术敲低其表达来研究已鉴定的 Bax 激活蛋白的生理功能。这些研究将有助于提高我们对 Bax 激活机制的了解，Bax 激活是细胞凋亡的关键决策过程。