Role of Clathrin Mediated Endocytosis in Podocyte Biology

项目摘要 慢性肾脏病（CKD）通常会导致不可逆的肾功能恶化， 通常进展为终末期肾病（ESKD）。CKD已经成为一个严重的公众 健康问题和从USRDS获得的数据显示， 美国患有CKD。由于肾小球疾病继发于足细胞功能障碍 占所有CKD的80%以上，这是一种密集的分子和遗传方法， 确定足细胞发育、维持和修复机制可能提供 最近的证据表明，网格蛋白介导的 协调足细胞功能的内吞作用。利用遗传小鼠模型，我们发现 参与介导网格蛋白介导的内吞作用的蛋白质，例如synaptojanin 1，发动蛋白， 和内亲和素对于维持正常功能的过滤屏障是不可或缺的。我们 进一步扩展了我们的发现，GAK，一种对揭开网格蛋白很重要的蛋白质， 同样重要。为了探讨其机制，对富集的肾小球进行了微阵列分析。 进行揭示了大量的肌动蛋白调节基因含有血清反应元件 由血清反应因子调节。我们还利用了人类的肾脏 局灶节段性肾小球硬化（FSGS）患者的活检， 结果显示GAK表达减少和血清应答因子表达增加。 因此，在目标1中，我们将定义GAK损失如何贡献的基本机制 通过血清反应因子介导的异常肌动蛋白动力学导致足细胞功能障碍。 在目标2中，我们将描述GAK的C-末端稳定足细胞功能的作用， 进一步研究足细胞内吞作用和肌动蛋白之间的联系。我们的老鼠模型 疾病与人类FSGS活检结果提供了动力，以进一步确定网格蛋白的作用， 介导的内吞作用的形成和维持一个完整的肾小球滤过屏障。

Project Summary Chronic kidney disease (CKD) often leads to irreversible deterioration of kidney function that often progresses to End Stage Kidney Disease (ESKD). CKD has emerged as a serious public health issue and data obtained from the USRDS reveals that the number 20 million patients in the United States suffer from CKD. As glomerular diseases secondary to podocyte dysfunction account for greater than 80% of all CKD, an intensive molecular and genetic approach to identify mechanisms for podocyte development, maintenance and repair may provide new therapeutic targets Recent evidence suggests an important role of clathrin mediated endocytosis orchestrating podocyte function. Using genetic mouse models, we have discovered proteins involved in mediating clathrin mediated endocytosis such as synaptojanin 1, dynamin, and endophilin, are indispensible for maintaining a normally functioning filtration barrier. We have further extended our findings that GAK, a protein important for uncoating clathrin, is equally important. To probe the mechanism, a microarray analysis on enriched glomeruli was performed revealing a plethora of actin-regulated genes containing a serum response element regulated by the serum response factor. We have also taken advantage of human kidney biopsies from patients with focal segmental glomerulosclerosis (FSGS), which also demonstrated reduced GAK expression and increased serum response factor expression. Therefore In Aim 1, we will define the fundamental mechanisms on how loss of GAK contributes to podocyte dysfunction through abnormal actin dynamics mediated by serum response factor. In Aim 2, we will characterize the role of GAK's C-terminus to stabilize podocyte function and further investigate the link between endocytosis and actin in podocytes. Our mouse models of disease with human FSGS biopsy findings provide impetus to further define the role of clathrin- mediated endocytosis in the formation and maintenance an intact glomerular filtration barrier.