Physiologic role of collecting duct ciiliary proteins

描述(申请人提供)：本建议的目的是研究集合管初级纤毛在调节肾脏电解质和水的排泄以及全身血压方面的生理作用。最近的研究表明，肾小管上皮细胞中的中央纤毛在肾脏病理中起重要作用；许多肾囊性疾病基因产物至少部分定位于原发纤毛，这些囊性成分的突变导致囊性肾脏疾病。相比之下，初级纤毛在正常生理条件下调节肾小管上皮细胞的作用尚不清楚。一种流行的假说是，初级纤毛凭借其顶端位置传递机械信号，如小管液体流速，为细胞提供有关细胞取向的信息。这一信息可能对保持肾小管细胞处于分化状态很重要。此外，这种机械转导可能有助于将肾小管液体流量与跨上皮电解质和水的运输联系起来。这样的系统在调节集合管中钾的分泌以及钠和水的重吸收方面可能特别重要。如果是这样，那么集合管中的初级纤毛在控制全身血压方面可能最终是至关重要的。为了检验这一可能性，目前的提案将有两个主要的具体目标： 1)建立时间控制的收集管特异性基因敲除小鼠，这些基因可能参与传递流动调节的纤毛机械感觉(pkd1或Tg737)。由于传统的纤毛基因敲除会导致包囊的形成，本研究将尖锐地敲除成人的纤毛基因。其目标是建立睫状肌基因敲除的动物模型，并在肾囊肿发生之前进行生理学分析。 2)确定纤毛蛋白表达缺陷(多囊蛋白-1或北极星)是否会导致全身血压改变和/或肾脏电解质和水分排泄改变。收集管的电解质和水分输送将发生急性或慢性变化，肾脏对肾脏盐分和水分排泄的适当补偿能力以及血压反应将被确定。 这些研究将开始研究肾脏生理学中一个基本重要但在很大程度上尚未探索的领域--集合管通过初级纤毛与环境相互作用的能力，以调节肾脏盐分和水的排泄以及全身血压。这些研究旨在为随后的纤毛调节肾小管运输过程的机制分析提供基础。最重要的是，这项工作可能会为控制血压和高血压的发展提供新的机制。

DESCRIPTION (provided by applicant): The purpose of current proposal is to study the physiologic role of collecting duct primary cilia in regulating renal electrolyte and water excretion and systemic blood pressure. Recent studies indicate that central cilia in renal tubular epithelial cells play an important role in renal pathology; many renal cystic disease gene products localize, at least in part, to the primary cilia, and mutations in these cystic components leads to cystic kidney disease. In contrast, the role of primary cilia in regulating renal tubular epithelial cells under normal physiologic conditions is unknown. A prevailing hypothesis is that primary cilia, by virtue of their apical location, transduce mechanical signals such as tubule fluid flow rate, that provide the cell with information about cell orientation. This information may be important in keeping tubule cells in a differentiated state. In addition, such mechanotransduction may help link tubule fluid flow rate with transepithelial electrolyte and water transport. Such a system may be particularly important in regulating collecting duct secretion of potassium and reabsorption of sodium and water. If so, then primary cilia in collecting duct may ultimately be vitally important in the control of systemic blood pressure. To test this possibility, the current proposal will have two major specific aims: 1) To generate mice with temporally-controlled collecting duct-specific knockout of genes likely to be involved in transducing flow-regulated cilia mechanosensation (pkdl or Tg737). Since conventional ciliary gene knockouts lead to cyst formation, the current study will acutely knockout target ciliary genes in adults. The goal is to develop animal models of ciliary gene knockout the permit physiologic analysis prior to the development of renal cysts. 2) To determine if deficiency of ciliary protein expression (polycystin-1 or polaris) in mice leads to altered systemic blood pressure and/or altered renal electrolyte and water excretion. Collecting duct electrolyte and water delivery will be acutely or chronically changed and the ability of the kidney to appropriately compensate renal salt and water excretion, as well as the blood pressure response, will be ascertained. These studies will begin to examine a fundamentally important yet largely unexplored area in renal physiology - the ability of the collecting duct to interact with its environment, through the primary cilia, to regulate renal salt and water excretion and systemic blood pressure. Such studies are designed to provide the groundwork for subsequent mechanistic analysis of ciliary regulation of renal tubule transport processes. Most importantly, this work may shed light on novel mechanisms involved in control of blood pressure and development of hypertension.