Epithelial Na channel (ENaC) polymorphisms in hyptertention

描述(由申请人提供)：血压的控制部分是通过调节肾远端肾单位的钠重吸收。在这里，上皮性钠通道(ENaC)的活性对钠的重吸收是有限的。醛固酮是肾素-血管紧张素-醛固酮系统(RAAS)中的最后一种激素，它能增加ENaC的活性，从而提高血压。人类通过一种经典的负反馈机制控制血压，当血压下降时，RAAS激活ENaC。所有形式的遗传性单基因高血压都与盐敏感有关，是在血压升高时ENaC不适当激活的结果。这些严重但罕见的高血压疾病要么是ENaC功能突变的获得，要么是它的上游调节因子RAAS的结果。更普遍但不那么严重的原发性高血压是多基因倾向于高血压的表现，生活方式的选择和环境因素加剧了这种倾向。许多原发性高血压，特别是在非裔美国人中，与盐敏感和低肾素和醛固酮水平有关。由于负反馈调节，盐敏感、低肾素和低醛固酮的高血压与ENaC功能障碍有关。分子遗传学研究发现，ENaC的序列变异(多态)在非裔美国人群体中丰富。最近发现在非裔美国人中流行的四种ENaC基因(α-T334A、C618F、T663A和β-T594M)可能与低肾素/醛固酮高血压有关；然而，这些多态对ENaC功能的影响仍有待测试。因此，目前尚不清楚这些基因多态是否在某些形式的盐敏感型高血压中起到致病作用。目前的提案通过检验ENaC基因多态增加通道活性的假设来解决这个问题。我们的实验室有能力进行这项研究，因为我们能够评估重组ENaC在哺乳动物表达系统中的功能。我们将利用这一专业知识来解决两个具体目标：1)确定ENaC多态对通道活性的影响；2)确定多态ENaC增加活性的细胞/分子机制。初步结果支持这项调查的可行性，并表明这一调查路线将产生重大和新颖的发现。

DESCRIPTION (provided by applicant): Blood pressure is controlled, in part, by regulated sodium reabsorption at the distal renal nephron. Here, activity of the epithelial Na channel (ENaC) is limiting for sodium reabsorption. Aldosterone, the final hormone in the renin-angiotensin-aldosterone-system (RAAS), increases ENaC activity to increase blood pressure. Humans control blood pressure through a classic negative-feedback mechanism with RAAS activating ENaC as blood pressure falls. All forms of inheritable, monogenic hypertension are associated with salt-sensitivity and result from inappropriate activation of ENaC in the face of elevated blood pressure. These severe but rare hypertensive diseases result from either gain of function mutations in ENaC or its upstream regulator RAAS. The more prevalent but less severe essential hypertension is a manifestation of a polygenic predisposition towards elevated blood pressure exacerbated by life-style choices and environmental factors. Much essential hypertension particularly that in African American populations is associated with salt-sensitivity and low renin and aldosterone levels. Due to negative-feedback regulation, hypertension with salt-sensitivity, low renin and aldosterone implicates ENaC dysfunction. Molecular genetic studies identified sequence variations (polymorphisms) in ENaC enriched in African American populations. Possible linkage between four ENaC polymorphisms prevalent in African American populations, (alphaT334A, C618F, T663A and beta T594M) with low-renin/aldosterone hypertension has recently been suggested; however, the effects of these polymorphisms on ENaC function remain to be tested. Thus, it is unclear if these polymorphisms can play a causative role in some forms of salt-sensitive hypertension. The current proposal addresses this question by testing the hypothesis that ENaC polymorphisms increase channel activity. Our laboratory is well positioned to conduct this investigation for we are capable of assessing function of recombinant ENaC in a mammalian expression system. We will utilize this expertise to address two Specific Aims: 1) Determine the effects of ENaC polymorphisms on channel activity; and 2) Determine the cellular/molecular mechanisms by which polymorphic ENaC has increased activity. Preliminary results support the feasibility of this investigation and suggest that this line of inquiry will yield significant and novel findings.