Regulation of calcium signaling by the PKD2 gene product

常染色体显性遗传性多囊肾病（Autosomal dominant polycystic kidney disease，ADPKD）是最常见的遗传病之一。它影响1/1000的美国人，在肾脏，肝脏和胰腺中发展上皮囊肿。两个独立基因PKD 1和PKD 2中的天然突变导致绝大多数（约99%）ADPKD病例。PKD 1编码具有长胞外结构域的大质膜蛋白，而PKD 2编码TRP超家族的离子通道（目前命名为TRPP 2）。我们和其他人已经表明，PKD 1与TRPP 2物理相互作用，形成一个离子通道复合物（PKD 1/TRPP 2），连接细胞外刺激钙离子内流。然而，这些基因的突变如何导致ADPKD仍然是未知的。与β-连环蛋白无关的Wnt通路分支缺陷（非经典Wnt通路）也与囊肿发生相关。我们认为PKD 1/TRPP 2介导的信号传导与非经典Wnt通路之间存在功能性相互作用。我们将通过以下问题来验证这一假设：1）PKD 1或PKD 2中的致病性突变是否会破坏非经典Wnt信号通路？2)PKD 1/TRPP 2复合物的激活过程如何受到非经典Wnt通路的调节？（3）这两条通路在体内是否交叉？这些问题将通过细胞培养、斑马鱼胚胎和小鼠的补充方法来解决。这些研究将有助于我们了解PKD 1和TRPP 2的基本特性及其在囊肿发生中的作用。由于ADPKD的病理生理学基础尚不清楚，这些实验将为治疗策略的发展奠定基础。

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common genetic diseases. It affects 1 in 1000 Americans with the development of epithelial cysts in the kidney, liver, and pancreas. Naturally occurring mutations in two separate genes, PKD1 and PKD2, are responsible for the vast majority (~99%) of all cases of ADPKD. PKD1 encodes a large plasma membrane protein with a long extracellular domain, while PKD2 encodes an ion channel of the TRP superfamily (currently named, TRPP2). We and others have shown that PKD1 physically interacts with TRPP2 to form an ion channel complex (PKD1/TRPP2) that links extracellular stimuli to Ca2+ influx. However, it still remains unknown how mutations in these genes cause ADPKD. Defects in the limb of the Wnt pathway not associated with beta-catenin (non-canonical Wnt pathway) have been also associated with cystogenesis. We propose that there is a functional interaction between PKD1/TRPP2-mediated signaling and the non-canonical Wnt pathway. We will test this hypothesis by asking: 1) Can pathogenic mutations in PKD1 or PKD2 disrupt non-canonical Wnt signaling pathway? 2) How the activation process of the PKD1/TRPP2 complex is modulated by the non-canonical Wnt pathways? And 3) Do these two pathways intersect in vivo? These questions will be addressed by complementary approaches in cell culture, zebrafish embryos, and the mouse. The proposed studies will help us understand fundamental properties of PKD1 and TRPP2 and their roles in cystogenesis. As the pathophysiological basis of ADPKD is unknown, these experiments will set the stage for the development of therapeutic strategies.