Regulation of calcium signaling by the PKD2 gene product

两个独立基因PKD 1和PKD 2中自然发生的突变是导致绝大多数 （~99%）的常染色体显性多囊肾病（ADPKD）病例，是最常见的多囊肾病之一。 遗传性疾病影响1/1000的美国人。ADPKD的标志是上皮囊肿的发展 肾脏肝脏和胰腺目前还没有有效的治疗ADPKD的方法。PKD 1编码一个大的 一种质膜蛋白（PKD 1或多囊蛋白1），具有较长的胞外结构域， 它可以作为非典型G蛋白偶联受体发挥作用。PKD 2编码瞬时的离子通道 受体电位超家族（TRPP 2、PKD 2或多囊蛋白2）。然而，这些分子的功能 蛋白质和PKD 1和PKD 2突变引起ADPKD的机制尚不清楚。我们 最近已经表明PKD 1和TRPP 2在质膜上形成复合物，该复合物被 分泌的WNT配体。WNT蛋白直接结合PKD 1的胞外结构域并诱导Ca 2+内流 和依赖于TRPP 2的全细胞电流。PKD 1/TRPP 2复合物含有Dishevelled （DVL），其是介导Wnt信号传导的细胞质蛋白。PKD 1/TRPP 2复合物具有 在响应WNT配体的定向细胞迁移和趋化性中起重要作用。蛙胚胎PKD 1 与WNT 9A和DVL 2一起工作以控制肾小管直径。因此，我们假设PKD 1 和TRPP 2介导WNT诱导的Ca 2+信号传导，其对于定向细胞迁移是必需的，并有助于 肾小管直径的测定。在本提案中，我们将确定WNT的机制- 诱导PKD 1/TRPP 2活化（特异性目的1）。确定WNT诱导定向细胞中的步骤 PKD 1和TRPP 2特异性影响的迁移（特异性目标2）。确定DVL是否单独或 与其他与PKD 1和TRPP 2下游Wnt信号传导功能相关的胞质蛋白的关联， WNT诱导的细胞迁移（具体目标3）。这一建议有望揭示的机制， WNT诱导的PKD 1/TRPP 2活化，这些蛋白调节定向细胞的机制 迁移和细胞途径激活的下游立即WNT诱导的PKD 1/TRPP 2介导的 Ca 2+信号。对这些途径的了解可以作为发现新的 ADPKD的药物靶点

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.