IDENTIFICATION AND CHARACTERIZATION OF THE GLEPP1/RECEPTOR LIGAND

糖尿病性肾小球硬化和其他硬化性疾病进展为ESRD 肾小球疾病（如FSGS）与蛋白质泄漏有关 通过肾小球过滤器（肾病综合征）。一个主要的细胞 负责维持肾小球滤过器完整性的是 足细胞，其叉指状足在肾小球周围突起 基底膜，并在其间形成肾小球滤液。 在肾脏中心的事先支持下，我们已经鉴定、克隆和 测序了两种重要的蛋白质， 肾小球滤过器这是一种新的足细胞足突受体 酪氨酸磷酸酶（称为GLEPP 1）和足糖萼蛋白（主要负 最初由法夸尔发现的足突带电分子， 负责通过充电保持足突分开的同事 排斥）。最近对GLEPP 1受体的分析表明， GLEPP 1受体样PTK导致肾小球变得更加 白蛋白可渗透（渗漏），可能部分通过抑制PTB 酶的功能。因此，一个直接的和以前未知的机制， 已经确定了对肾小球过滤器的控制。同时，新 有资料表明，在其他细胞中，PTPases调节细胞间 类似于狭缝光阑的结（专用于 细胞间连接），其用作足部之间的过滤装置 足细胞的突起。在本申请中，我们提出（a）识别 使用重组GLEPP 1胞外结构域的GLEPP 1配体 构建体和哺乳动物cDNA表达克隆策略，和（B） 测试干扰GLEPP 1-配体相互作用的假设 使用分离的肾小球调节肾小球滤过器的通透性 渗透性测定长期目标是开发药理学 可以通过这种机制调节肾小球通透性的药物。

Progression to ESRD of diabetic glomerulosclerosis and other sclerosing glomerular diseases (e.g. FSGS) is associated with a leak of protein through the glomerular filter (the Nephrotic Syndrome). A major cell responsible for maintaining the integrity of the glomerular filter is the podocyte, whose interdigitating foot processes about the glomerular basement membrane, and between which the glomerular filtrate is formed. With prior support from the Renal Center we have identified, cloned and sequenced two major proteins of importance for the function of the glomerular filter. These are a novel podocyte foot process receptor tyrosine phosphatase (called GLEPP1) and podocalyxin (the major negatively charged molecule of the foot process originally identified by Farquhar and colleagues which is responsible for keeping foot processes apart by charge repulsion). Recent analysis of the GLEPP1 receptor shows that antibodies to the GLEPP1 receptor-like PTPase cause the glomerulus to become more permeable to albumin (leaky), probably in part by inhibiting the PTPase function of the enzyme. Thus a direct and previous unknown mechanism of control of the glomerular filter has been identified. At the same time new information shows that in other cells PTPases regulate intercellular junctions that are analogous to the slit diaphragms (specialized intercellular junctions) that serve as filtration devices between the foot processes of the podocyte. In this application we propose (a) to identify the GLEPP1 ligand using a recombinant GLEPP1 extracellular domain construct and a mammalian cDNA expression cloning strategy, and (b) to test the hypothesis that interference with the GLEPP1-ligand interaction modulates glomerular filter permeability using an isolated glomerular permeability assay. The long term goal will be to develop pharmacologic agents which can modulate glomerular permeability through this mechanism.