Regulation of calcium signaling by the PKD2 gene product

绝大多数是由两个独立基因PKD1和PKD2自然产生的突变造成的 (~99%)常染色体显性遗传性多囊肾病(ADPKD)是最常见的 每1000名美国人中就有1人患有遗传病。ADPKD的特征是上皮性囊肿的发展 在肾脏、肝脏和胰腺。目前，ADPKD尚无有效的治疗方法。PKD1编码一个很大的 具有较长胞外结构域的质膜蛋白(PKD1或Polycystin 1)，已被推测 它可以作为一个非典型的G蛋白偶联受体发挥作用。PKD2编码了瞬变的离子通道 受体潜能超家族(TRPP2、PKD2或多囊蛋白2)。然而，这些分子的功能 蛋白质和PKD1和PKD2突变导致ADPKD的机制(S)一直难以捉摸。我们 最近发现，PKD1和TRPP2在质膜上形成一个复合体，该复合体被 隐藏的WNT配体。WNT蛋白直接与PKD1胞外域结合并诱导钙内流 以及依赖于TRPP2的整个细胞电流。PKD1/TRPP2复合体含有杂乱 (DVLS)，这是一种介导Wnt信号的细胞质蛋白。PKD1/TRPP2复合体有一个 WNT配体在细胞定向迁移和趋化中的重要作用。在青蛙胚胎中，PKD1 与wnt9a和dvl2一起控制肾小管直径。因此，我们假设PKD1 而TRPP2介导WNT诱导的钙信号转导，这是细胞定向迁移所必需的，并有助于 肾小管直径的测定。在这项建议中，我们将确定WNT的机制- 诱导PKD1/TRPP2的激活(特异性靶点1)。确定三硝基甲苯诱导定向细胞的步长(S) 受PKD1和TRPP2特别影响的移徙(具体目标2)。确定DVL是单独还是在 与PKD1和TRPP2下游与Wnt信号功能相关的其他细胞质蛋白的相关性 WNT诱导细胞迁移(特异靶向3)。预计这项提案将阐明 WNT诱导的PKD1/TRPP2的激活及其调控定向细胞的机制 WNT诱导的PKD1/TRPP2介导的迁移和细胞通路的直接下游激活 钙离子信号转导。对这些途径的了解可以作为发现新的 ADPKD的可用药靶点。

Naturally occurring mutations in two separate genes, PKD1 and PKD2, are responsible for the vast majority (~99%) of all cases of autosomal dominant polycystic kidney disease (ADPKD), one of the most common genetic diseases affecting 1 in 1000 Americans. The hallmark of ADPKD is the development of epithelial cysts in the kidney, liver, and pancreas. Currently, there is no effective treatment for ADPKD. PKD1 encodes a large plasma membrane protein (PKD1 or Polycystin 1) with a long extracellular domain and has been speculated that it can function as an atypical G protein coupled receptor. PKD2 encodes an ion channel of the Transient Receptor Potential superfamily (TRPP2, PKD2, or Polycystin 2). However, the molecular function of these proteins and the mechanism(s) by which mutations in PKD1 and PKD2 cause ADPKD have been elusive. We have shown recently that PKD1 and TRPP2 form a complex at the plasma membrane that is activated by secreted WNT ligands. WNT proteins bind directly to the extracellular domain of PKD1 and induce Ca2+ influx and whole cell currents that are dependent on TRPP2. The PKD1/TRPP2 complex contains Dishevelleds (DVLs), which are cytoplasmic proteins that mediate Wnt signaling. The PKD1/TRPP2 complex has an essential role in directed cell migration and chemotaxis in response to a WNT ligand. In frog embryos pkd1 works together with wnt9a and dvl2 to control kidney tubular diameter. Therefore, we hypothesize that PKD1 and TRPP2 mediate WNT-induced Ca2+ signaling that is essential for directed cell migration and contributes to the determination of kidney tubule diameter. In this proposal, we will determine the mechanism of WNT- induced activation of PKD1/TRPP2 (Specific Aim 1). Determine the step(s) in WNT-induced directed cell migration specifically affected by PKD1 and TRPP2 (Specific Aim 2). Determine whether DVLs alone or in association with other cytosolic proteins linked to Wnt signaling function downstream of PKD1 and TRPP2 in WNT-induced cell migration (Specific Aim 3). This proposal is expected to shed light onto the mechanisms of WNT-induced activation of the PKD1/TRPP2, the mechanisms by which these proteins regulate directed cell migration, and cellular pathways activated immediately downstream of WNT-induced PKD1/TRPP2-mediated Ca2+ signaling. Knowledge of these pathways can be used as the springboard for the discovery of new druggable targets for ADPKD.