Roles of KIM-1 in Renal Injury and Repair

描述(由申请人提供)： 申请者提出了一个研究计划，为他在学术医学领域的职业生涯做准备。这项研究将在马萨诸塞州总医院约瑟夫·邦文特尔博士的实验室进行。Bonventre博士是一位对急性肾功能衰竭感兴趣的资深研究员，他成功地培训了具有不同兴趣的研究人员。申请者的长期目标是独立研究急性肾功能衰竭的机制，并改善这种疾病患者的治疗和预后。近端小管对缺血损伤特别敏感，缺血后该段存活的细胞经历了一个活跃的去分化和增殖过程，最终导致了分化良好的极化形态的重建。然而，肾小管上皮细胞修复的机制尚不完全清楚。肾损伤分子-1(KIM-1)是一种1型跨膜蛋白，是一种上皮细胞黏附分子，主要在肾脏损伤后表达。缺血再灌注后，Kim-1与上皮细胞去分化标志物Vimentin共表达。KIM-1在肾癌中也有表达，其状态与去分化上皮细胞表型有关。急性肾功能衰竭患者尿液中可检测到Kim-1的裂解胞外结构域。在前期实验中，我们发现肿瘤坏死因子-α促进769-P细胞中Kim-1的脱落，同时MEK-1、分泌型磷脂酶A2和环氧合酶的抑制剂抑制肿瘤坏死因子-α诱导的769-P细胞中Kim-1的脱落，这些细胞在正常培养条件下表达大量的内源性Kim-I，并有条件地进入培养基中。这个项目的主要目标是确定Kim-1的功能作用和特定的信号机制，控制细胞因子介导的Kim-1在肾上皮细胞中的脱落。本申请中提出的研究将为了解Kim-1在肾小管上皮损伤和修复中的功能作用提供重要的新见解，并可能导致影响肾脏的急性疾病的新的治疗方法。

DESCRIPTION (provided by applicant): The applicant proposes a program of research to prepare him for a career in the academic medicine. The research will be conducted in the laboratory of Dr. Joseph Bonventre at the Massachusetts General Hospital. Dr. Bonventre is an established senior investigator with an interest in acute renal failure who has successfully trained research fellows with a variety of interests. The long-term objective of the applicant is to independently investigate mechanisms of acute renal failure and improve the therapy and outcome of patients with this disease. The proximal tubule is particularly sensitive to ischemic injury and the surviving cells in this segment undergo an active process of dedifferentiation and proliferation after ischemia ultimately resulting in the reconstitution of a well differentiated polarized morphology. However the mechanisms by which the tubular epithelial cells are restored are not fully understand. Kidney Injury Molecule-1 (KIM-1) is a type 1 transmembrane protein and an epithelial cell adhesion molecule, which expresses predominantly in the injured kidney. After ischemia/reperfusion KIM-1 is coexpressed with vimentin, a marker of epithelial cell dedifferentiation. KIM-1 is also expressed in renal cell carcinoma, which state is associated with a dedifferentiated epithelial cell phenotype. The cleaved ectodomain of KIM-1 can be detected in the urine of patients with ischemic acute renal failure. In pilot experiments, we have found that tumor necrosis factor-alpha (TNF-alpha) enhanced the shedding of KIM-1 and, meanwhile, inhibitors of MEK-1, secretory phospholipase A2, and cyclooxygenase diminished the TNF-alpha induced shedding of KIM-1 in 769-P cells, which express abundant level of endogenous KIM-I under normal culture condition and constitively shed into culture media. This project's broad objectives are to define the functional role of KIM-1 and specific signaling mechanisms controlling cytokine mediated-shedding of KIM-1 in renal epithelial cells. The studies proposed in this application will provide important new insights regarding understanding functional role of KIM-1 in injury and repair of the renal tubular epithelium and may lead to new therapeutic approaches in acute diseases affecting the kidney.