Roles of KIM-1 in Renal Injury and Repair

描述（由申请人提供）： 申请人提出了一个研究计划，为他在学术医学的职业生涯做准备。这项研究将在马萨诸塞州总医院的Joseph Bonventre博士的实验室进行。Bonventre博士是一位对急性肾衰竭感兴趣的资深研究员，他成功地培训了具有各种兴趣的研究员。申请人的长期目标是独立研究急性肾衰竭的机制，并改善该疾病患者的治疗和结局。近端小管对缺血性损伤特别敏感，并且在缺血后，该部分中的存活细胞经历去分化和增殖的活跃过程，最终导致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还不完全清楚。肾损伤分子-1（KIM-1）是一种1型跨膜蛋白和上皮细胞粘附分子，主要在受损的肾脏中表达。在缺血/再灌注后，KIM-1与波形蛋白共表达，波形蛋白是上皮细胞去分化的标志物。KIM-1也在肾细胞癌中表达，其状态与去分化上皮细胞表型相关。在缺血性急性肾功能衰竭患者的尿液中可以检测到KIM-1的切割胞外域。在初步实验中，我们发现肿瘤坏死因子-α（TNF-α）增强了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减少了TNF-α诱导的769-P细胞中KIM-1的脱落，769-P细胞在正常培养条件下表达丰富水平的内源性KIM-1，并组成性地脱落到培养基中。本项目的主要目标是确定KIM-1的功能作用和控制细胞因子介导的KIM-1在肾上皮细胞中脱落的特定信号传导机制。本申请中提出的研究将为理解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.