TRPC channels in proteinuric kidney disease

描述（由申请人提供）：典型的瞬时受体电位通道6 （TRPC6）最近被添加到越来越多的涉及家族性蛋白尿肾病的基因中，以肾病和最终肾功能衰竭为特征。有趣的是，迄今为止已知的所有TRPC6突变都是功能突变的增益，这表明通过TRPC6通道增加的Ca+2内流导致足细胞损伤。足细胞中TRPC通道调控的机制在很大程度上是未知的。此外，通过TRPC通道的Ca+2内流增加是否发生在遗传性和获得性蛋白尿肾病中仍是一个问题。我们的初步数据表明，TRPC1和TRPC5在肾小球足细胞中表达，与TRPC6一样，它们定位于狭缝膈附近的足细胞足突。我们在足细胞中进行的粘附试验和伤口试验表明，通道向膜褶边的易位惊人，表明通道定位是一个受调节的过程。血管紧张素在表达AT1R的足细胞中诱导显著的钙瞬变，并且这种钙内流的很大一部分似乎是由TRPC通道介导的。足细胞膜片钳实验证实了trpc样电流的存在。单通道记录表明通道活性受通道向膜的移位调节。当足细胞中的膜运输被药理学和分子技术破坏时，trpc样电流在很大程度上减弱，这支持了通道活性受通道向膜转运调节的观点。基于我们的初步工作，我们假设TRPC1和TRPC5在足细胞中形成了新的通道，这些通道与TRPC6一起，通过调节其转运到质膜，以响应血管紧张素1型受体的上游信号，介导Ca+2内流。

DESCRIPTION (provided by applicant): The canonical transient receptor potential channel 6 (TRPC6) has been recently added to the growing number of genes involved in familial forms of proteinuric kidney disease, characterized by nephrosis and ultimate renal failure. Interestingly, all TRPC6 mutations known to date are gain of function mutations, suggesting that increased Ca+2 influx through TRPC6 channels leads to podocyte injury. The mechanisms for TRPC channel regulation in podocytes are largely unknown. Furthermore, the question remains whether an increase in Ca+2 influx through TRPC channels occurs in both genetic and acquired forms of proteinuric kidney disease. Our preliminary data suggest that TRPC1 and TRPC5 are expressed in glomerular podocytes, where, like TRPC6, they localize to podocyte foot processes, in the vicinity of slit diaphragms. Our adhesion assays and wound assays in podocytes demonstrate a striking translocation of channel to membrane ruffles, indicating that channel localization is a regulated process. Angiotensin induces prominent calcium transients in podocytes expressing the AT1R, and a significant portion of this calcium influx appears to be mediated by TRPC channels. Patch clamp experiments in podocytes confirm the presence of a TRPC-like current. Single channel recordings suggest that channel activity is regulated by channel translocation to the membrane. When membrane trafficking is disrupted by pharmacologic and molecular techniques in podocytes, the TRPC-like current is largely diminished, supporting the notion that channel activity is regulated by channel translocation to the membrane. Based on our preliminary work, we hypothesize that TRPC1 and TRPC5 form novel channels in podocytes, which, in concert with TRPC6, mediate Ca+2 influx by their regulated translocation to the plasma membrane in response to upstream signaling through the Angiotensin Type 1 Receptor. PUBLIC HEALTH RELEVANCE: This work on the role of TRPC channels in proteinuric kidney disease will help identify targets for the development of medications and therapies to treat and prevent diseases such as nephrotic syndrome and diabetic nephropathy, which currently affect many kidney disease patients worldwide.