IDENTIFICATION AND CHARACTERIZATION OF THE GLEPP1/RECEPTOR LIGAND

糖尿病肾小球硬化及其他硬化的终末期肾病进展 肾小球疾病(如FSGS)与蛋白质泄漏有关 通过肾小球滤过器(肾病综合征)。一个主要细胞 负责维护肾小球滤过器的完整性的是 足细胞，其交错的足突围绕肾小球 基底膜，其间形成肾小球滤液。 在肾脏中心的支持下，我们已经鉴定、克隆和 测序了两个对细胞功能至关重要的主要蛋白质 肾小球滤器。这些是一种新的足细胞足突受体 酪氨酸磷酸酶(称为GLEPP1)和豆腐果苷(主要为负性 足突的带电分子最初是由Farquhar和 负责通过充电将脚部过程分开的同事 排斥力)。最近对GLEPP1受体的分析表明，抗体 GLEPP1受体样PTPase导致肾小球变得更多 对白蛋白具有通透性(渗漏)，可能部分是通过抑制PTPase 酶的功能。因此，一种直接的和以前未知的机制 肾小球滤过器的控制已经确定。同时也是新的 信息显示，在其他细胞中，PTPase调节细胞间 类似于狭缝横隔膜的接头(专用 细胞间连接)作为脚部之间的过滤装置 足细胞的突起。在本申请中，我们建议(A)确定 利用重组GLEPP1胞外区构建GLEPP1配体 构建和一种哺乳动物基因表达克隆策略，以及(B) 检验干扰GLEPP1-配体相互作用的假设 使用分离的肾小球调节肾小球滤过通透性 通透性测定。长期目标将是开发药理学 通过这一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.