Regulation of calcium signaling by the PKD2 gene product

常染色体显性遗传性多囊肾病(ADPKD)是最常见的遗传病之一。它影响每1000个美国人中就有一个，伴随着肾脏、肝脏和胰腺上皮性囊肿的发展。在所有ADPKD病例中，绝大多数(~99%)是由两个独立基因PKD1和PKD2自然发生的突变引起的。PKD1编码一个大的质膜蛋白，具有较长的胞外结构域，而PKD2编码Trp超家族的一个离子通道(目前命名为TRPP2)。我们和其他人已经证明，PKD1与TRPP2在物理上相互作用，形成一个离子通道复合体(PKD1/TRPP2)，将细胞外刺激与钙内流联系起来。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(非典型的Wnt途径)无关的Wnt途径的肢体缺陷也与膀胱发生有关。我们认为，在PKD1/TRPP2介导的信号转导和非典型的Wnt通路之间存在着功能上的相互作用。我们将通过以下问题来验证这一假说：1)PKD1或PKD2的致病突变是否会扰乱非典范Wnt信号通路？2)非典范Wnt信号通路如何调控PKD1/TRPP2复合体的激活过程？3)这两条途径在体内是否相交？这些问题将通过细胞培养、斑马鱼胚胎和小鼠的互补方法来解决。这些研究将有助于我们了解PKD1和TRPP2的基本性质以及它们在膀胱发生中的作用。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.