CELL PATHOLOGY IN KIDNEY HYPOXIA. ROLE OF BAX

描述（由申请方提供）：肾小管上皮细胞缺失导致缺血性急性肾衰竭的发生。我们的长期目标是阐明参与缺氧细胞损伤的分子机制，并制定保护策略。我们已经表明，Bax，Bcl-2家族的促凋亡成员，在缺氧/ATP耗竭引起的细胞损伤中起着重要作用，并在再氧合/ATP补充过程中发生的细胞凋亡中起着重要作用。在缺氧期间，Bax从细胞质易位到线粒体并形成寡聚体。以及相关的巴克低聚物。Bax使线粒体透化以释放细胞色素c（Cyt.c）。Cyt.c促进形成蛋白质复合物，即胱天蛋白酶激活和随后的凋亡执行所需的核糖体。抗凋亡Bcl-2的表达不能阻止Bax易位，但能消除Bax和巴克寡聚化，从而消除Cyt.c渗漏。在体实验表明，缺血再灌注过程中Bax和Bcl-2在肾脏中的相互调节。基于这些发现，我们提出了四个具体目标：目标1假设Bax依赖的细胞色素c释放是一个两步过程，涉及易位，然后由BH 3-only蛋白诱导的寡聚化。在这方面的研究将使用基因沉默，体外重建，以及EM-免疫组织化学和FRET技术来检查线粒体外膜透化的机制。目的2推测Bax和巴克形成的孔道结构中含有其他线粒体外膜蛋白。这些实验将使用基于免疫沉淀、2D-PAGE和质谱的肽序列分析。目的3假设不同的ATP需求的顺序阶段的凋亡途径。半胱天冬酶激活及其抑制机制将通过免疫印迹、体外重建、基因表达和诱变来研究。目的4假设Bax表达调节肾小管损伤。Bax启动子在缺血和再灌注过程中的转录调控将使用迁移率变化分析和体外足迹法进行研究。将尝试Bax的体内基因沉默以努力阻断Bax的调节，从而防止缺血性肾中的细胞损伤。

DESCRIPTION (provided by applicant): Loss of tubular epithelium contributes to the development of ischemic acute renal failure. Our long term objective is to elucidate the molecular mechanisms that are involved in hypoxic cell injury and to develop protective strategies. We have shown that Bax, a pro-apoptotic member of the Bcl-2 family, plays a major role in cell injury caused by hypoxia/ATP depletion, and in the apoptosis that develops during reoxygenation/ATP repletion. During hypoxia, Bax translocates from cytosol to mitochondria and forms oligomers. Together with associated Bak oligomers. Bax permeabilizes mitochondria to release cytochrome c (Cyt.c). Cyt.c facilitates the formation of a protein complex, the apoptosome, required for caspase activation and subsequent apoptotic execution. Expression of anti-apoptotic Bcl-2 does not prevent Bax translocation, but abrogates Bax and Bak oligomerization, and thereby Cyt.c leakage. Experiments in vivo showed reciprocal regulation of Bax and Bcl-2 in the kidney during reperfusion after ischemia. Based on these findings, we propose to pursue four specific aims: Aim 1 hypothesizes that Bax dependent cytochrome c release is a two step process involving translocation followed by oligomerization induced by a BH3-only protein. Studies in this aim will use gene silencing, in vitro reconstitution, as well as EM-Immuno histochemistry and FRET techniques to examine the mechanisms of mitochondrial outer membrane permeabilization. Aim 2 hypothesizes that pore structures formed by Bax and Bak contain other mitochondrial outer membrane proteins. These experiments will use immunoprecipitation, 2D-PAGE and mass spectrometry based peptide sequence analysis. Aim 3 hypothesizes differential ATP requirements for sequential stages of the apoptotic pathway. Mechanisms of caspase activation and its inhibition will be studied by immunoblotting, in vitro reconstitution, gene expression and mutagenesis. Aim 4 hypothesizes that Bax expression regulates tubular injury in the kidney. Transcriptional regulation of Bax promoter during ischemia and reperfusion will be studied using mobility shift assays, and in vitro foot-printing. In vivo gene silencing of Bax will be attempted in efforts to block up regulation of Bax and thereby prevent cell injury in the ischemic kidney.