CELL PATHOLOGY IN KIDNEY HYPOXIA ROLE OF BAX

描述（改编自研究者摘要）：本申请 阐述了肾脏中细胞死亡的潜在机制， 缺氧 肾缺血是急性肾衰竭的常见原因， 缺血诱导的损伤由缺氧诱导。 观察到两种损伤 在缺氧阶段和复氧阶段， 可能导致这种损伤的机制是产生反应性的 氧物种。 本申请提出研究一种机制， 这种损伤以Bax的易位为中心，Bax是一种促进死亡的蛋白质， 蛋白质从细胞质到线粒体，这反过来又诱导 细胞色素c从线粒体释放到细胞质中。 的 主要研究者表明，损伤的形态学是凋亡， 不需要分子氧就能发生损伤。 校长 研究人员假设，细胞死亡的形态和性质 随着细胞色素C从线粒体释放到细胞质中 依赖于ATP的供应。 如果ATP可用，则 死亡就是细胞凋亡。 如果ATP不可用， 会导致。 这一假设是基于这样的认识，即细胞凋亡是 ATP依赖的过程。 线粒体中细胞色素c的丢失 损害细胞通过氧化产生ATP的能力， 需要电子传递链完整性的磷酸化 就在那条河上。 因此，如果细胞确实有现成的ATP供应， 通过保存糖酵解，那么凋亡将是细胞的形式， 死亡 因此，本申请的关键要素是研究 Bax易位到线粒体，线粒体的变化， 在线粒体外膜中诱导的渗透性， Bax，细胞色素c释放到胞质溶胶中， 包围 主要研究者提出了四个具体目标。 第一 三种利用大鼠近端肾小管细胞的细胞培养模型。 第一 一个具体的目的是研究Bax在细胞色素c释放中的作用， 缺氧期间的线粒体及其诱导机制 渗透性的变化。 这一具体目标将决定 Bax的细胞色素c泄漏，Bax的相互作用的性质与 与细胞死亡相关的特定蛋白质，以及 线粒体内膜通透性也发生改变。 第二特定 目的是确定Bax易位的分子机制 从细胞质转移到线粒体 重点将 放在磷酸化，核苷酸结合， 应激蛋白的结合。 Bax的缺失突变体将用于 绘制易位所需的蛋白质序列。 第三个具体目标 将研究Bcl-2抑制的分子机制， 细胞色素c在缺氧时释放。 这一具体目标将决定 抑制细胞色素释放所需的Bcl-2序列， 需要与Bax异源二聚化以获得保护活性， Bcl-2与死亡途径相关蛋白的关联， Bcl-2对Bax转录的影响。 第四个具体目标将执行 研究将对培养细胞的观察扩展到肾小管 显微解剖的大鼠肾单位和兔近端小管中的肾脏。 此外，将在缺血再灌注损伤中进行研究。

DESCRIPTION (Adapted from Investigator's Abstract): This application addresses mechanisms underlying cell death in the kidney in response to hypoxia. Renal ischemia is a common cause for acute renal failure and such ischemia-induced injury is induced by hypoxia. Injury is observed both during the hypoxic phase and during the phase of reoxygenation, and one mechanism that may account for such injury is the generation of reactive oxygen species. The present application proposes to study a mechanism for such injury that is centered on the translocation of Bax, a death-promoting protein from the cytosol to the mitochondria which in turn induces the release of cytochrome c from the mitochondria into the cytosol. The principal investigator shows that the morphology of injury is apoptosis and does not require molecular oxygen for the damage to occur. The principal investigator hypothesizes that the morphology and the nature of cell death following the release of cytochrome c from the mitochondria into the cytosol is dependent upon a supply of ATP. If ATP is available, then the form of death that would occur is apoptosis. If ATP is not available, then necrosis would result. This hypothesis is based on the recognition that apoptosis is an ATP-dependent process. The loss of cytochrome c from the mitochondria impairs the ability of the cell to generate ATP through oxidative phosphorylation which necessitates integrity of the electron transport chain in the mitochondrion. Thus, if the cells do have a ready supply of ATP through preserved glycolysis, then apoptosis would be the form of cellular demise. Thus, the critical elements of this application are the study of translocation of Bax to the mitochondrion, the changes in mitochondrial permeability that are induced in the outer mitochondrial membrane induced by Bax, the release of cytochrome c into the cytosol and the cell injury that ensues. The principal investigator proposes four specific aims. The first three utilize a cell culture model of rat proximal tubular cells. The first specific aim will investigate the role of Bax in cytochrome c release from mitochondria during hypoxia as well as the mechanisms by which it induces the permeability change. This specific aim will determine the requirement of Bax for cytochrome c leak, the nature of the interaction of Bax with specific proteins related to cell death, and whether changes in the mitochondrial inner membrane permeability also occur. The second specific aim will determine the molecular mechanisms underlying Bax translocation from the cytosol to the mitochondria during hypoxia. Emphasis will be placed on the roles played by phosphorylation, nucleotide binding, and the association of the stress proteins. Deletion mutants of Bax will be used to map protein sequences required for translocation. The third specific aim will investigate molecular mechanisms that underlie Bcl-2 inhibition of cytochrome c release during hypoxia. This specific aim will determine the sequences of Bcl-2 that are required to inhibit cytochrome release, the requirement of heterodimerization with Bax for protective activity, the association of Bcl-2 with proteins related to death pathways, and the effects of Bcl-2 on Bax turnover. The fourth specific aim will perform studies to extend the observations made on cultured cells to tubules of the kidney in microdissected rat nephrons and rabbit proximal tubules. Additionally, studies will be conducted in ischemia reperfusion injury.