CHANNEL PROPERTIES OF POLYCYSTIN 2

本项目研究了由多囊蛋白-2形成的一类新的细胞内钙通道的性质。迄今为止，已经确定了两种主要类型的钙释放通道：兰尼碱受体（RyR）和肌醇1，4，5-三磷酸受体（InsP 3R）。大多数细胞都含有这两种类型的通道，但相对密度差异很大。多种细胞内通道的共存并不令人惊讶，因为细胞需要以特定的反应对不同的刺激做出反应。待检验的假设是：1）多囊蛋白-2是内质网膜上独特的钙渗透通道。2)由多囊蛋白-2形成的钙通道受细胞内因子调节，包括镁、类花生酸、cAMP和多囊蛋白-1。3)蛋白质的特定区域可以被分成功能域。这些结构域是基于在患有常染色体显性多囊肾病（ADPKD）的子集或个体中发现的多囊蛋白-2中的突变。4)多囊蛋白-2通道活性的改变将改变细胞内钙信号传导。这里提出的初步结果表明，第一次多囊蛋白-2使一种新的钙渗透通道的内质网。本项目中概述的实验将在单通道水平上研究多囊蛋白-2的功能特性，并将通道特性与细胞和器官功能相关联。获得的结果将确定可能在分子水平上决定多囊蛋白-2作用机制的调节因子，并可能为多囊肾病患者提供有用的治疗方法。

This project examines the properties of a new class of intracellular Ca channel formed by polycystin-2. To date two major classes of Ca release channel have been identified: the ryanodine receptor (RyR) and the inositol 1,4,5-trisphosphate receptor (InsP3R). Most cells contain both types of channel, but the relative densities vary dramatically. The co-existence of a variety of intracellular channels is not surprising as cells need to respond to diverse stimuli with specific responses. The hypotheses to be tested are: 1) Polycystin-2 is a unique calcium- permeable channel in the endoplasmic reticular membrane. 2) The calcium channel formed by polycystin-2 is regulated by intracellular factors, including magnesium, eicosanoids, cAMP and polycystin-1. 3) specific regions of the protein can be divided into functional domains. These domains are based upon mutations found in polycystin-2 from subsets or individuals affected with autosomal dominant polycystic kidney disease (ADPKD). 4) Changes in channel activity of polycystin-2 will modify intracellular calcium signaling. The preliminary results presented here show for the first time that polycystin-2 makes a novel calcium permeable channel in the endoplasmic membrane. The experiments outlined in this project will investigate the functional properties of polycystin-2 at the single channel level and will correlate the channel properties with cell and organ function. The results to be obtained will identify regulatory factors that may determine the mechanism of action of polycystin-2 at a molecular level and may suggest useful tretments for individuals affected with polycystic kidney disease.