Junctional complex dysregulation during ischemic injury

缺血性肾组织损伤是许多肾脏疾病患者死亡率和发病率的重要因素。缺血性损伤的主要后果是通过肌动蛋白细胞骨架和细胞-细胞连接复合物（粘附连接和紧密连接）的大规模破坏而导致上皮细胞极性丧失。连接复合物是维持极化离子转运系统、受体和酶分布所必需的，这些都是正常肾功能所需的。ATP耗竭可作为肾缺血的体外模型。在这里，我们建议分析ATP耗竭过程中调节紧密连接的机制，并确定这些调节机制如何保护细胞免受损伤或加速恢复。实验将研究粘附连接（钙粘蛋白介导的细胞间粘附）如何调节紧密连接的组装和功能。我们假设ATP耗竭导致紧密连接的解体是粘附连接解体的结果.将通过操纵上皮细胞中的钙粘蛋白连接（表达突变钙粘蛋白）来检查缺血期间的钙粘蛋白细胞粘附分子连接，并将测定对紧密连接组装和细胞极性的影响。在ATP耗竭过程中，通过粘附连接的信号传导过程也可能被破坏。在本项目中要检验的一个主要假设是，在肾缺血期间，上皮细胞中Rho家族GTP酶的功能受到抑制，导致连接复合物的破坏。Rho家族GTP酶（Rho、Rac和Cdc 42）是Ras基因超家族的成员，并且已经显示出调节肌动蛋白细胞骨架组装。初步证据表明，Rho家族GTP酶控制上皮细胞中的细胞-细胞连接复合物组装。这些信号系统的激活也可以保护细胞免受缺血性损伤。我们的研究将提供新的和基本的洞察缺血期间被破坏的关键调节机制。

Ischemic renal tissue damage is a significant factor in the mortality and morbidity of patients suffering from numerous renal disorders. A primary consequence of ischemic injury is the loss of epithelial cell polarity through large-scale disruption of the actin cytoskeleton and cell-cell junctional complexes (adherens junctions and tight junctions). Junctional complexes are necessary for maintenance of polarized ion transport systems, receptors and enzyme distributions required for proper kidney function. ATP-depletion serves as an in vitro model for renal ischemia. Here we propose to analyze mechanisms that regulate tight junctions during ATP-depletion, and determine how these regulator mechanisms may protect cells from damage or accelerate recovery. Experiments will examine how adherens junctions (cadherin-mediated cell-cell adhesion) regulate tight junction assembly and function. We hypothesize that ATP- depletion causes tight junction disassembly as a consequence of adherens junction disassembly. Cadherin cell adhesion molecule junction during ischemia will be examined by manipulating cadherin junction (expressing mutant cadherins) in epithelial cells, and effects on tight junction assembly and on cell polarity will be assayed. Signaling processes leading through the adherens junction may also be disrupted during ATP-depletion. A major hypothesis to be tested in this project is that Rho-family GTPases functions in epithelial cells are inhibited during renal ischemia leading to disruption of junctional complexes. Rho-family GTPases (Rho, Rac and Cdc42) are members of the Ras gene superfamily, and have been shown to regulate actin cytoskeleton assembly. Preliminary evidence suggests that Rho-family GTPases control cell-cell junctional complex assembly in epithelial cells. Activation of these signaling systems may also protect cells from ischemic injury. Our studies will provide new and fundamental insight into critical regulatory mechanisms that are disrupted during ischemia.