Hypertension: Role of Smooth Muscle Cullin-3 and the CRL3 Complex

 描述(由申请人提供)：泛素连接酶通过促进底物蛋白质的泛素化来调节蛋白质的周转，底物蛋白质的目标是蛋白酶体的降解。CRL或Cullin-Ring泛素连接酶是进化保守的泛素连接酶中最大的一类。作为该家族的成员之一，cullin-3(CUL3)在动脉血压调节中发挥着重要作用，因为编码CUL3或CUL3接头蛋白的基因突变会导致主要形式的高血压。我们发表的证据和初步数据支持一种新的概念，即血管平滑肌CUL3在动脉血压调节中发挥实质性作用，其调节失调导致高血压。我们假设CUL3是RhoA的调节者，RhoA是一种小的GTP酶，控制着Rho激酶活性、钙敏感性、一氧化氮反应性和血管平滑肌的收缩活动。重要的是，血管CUL3的表达和作用在动脉血压调节中的作用还有待研究。我们将测试这一创新概念，即血压在一定程度上是通过血管平滑肌中依赖CUL3的途径来调节的。具体地说，我们假设a)CUL3活性受损导致高血压，b)导致人类高血压的CUL3突变体不能正确泛素化CUL3底物(如RhoA)，以及c)CUL3突变体主要通过干扰野生型内源性CUL3发挥作用。该项目的目的是：1)验证突变的CUL3对野生型CUL3的显性干扰和CUL3的血管平滑肌特异性缺陷导致血管运动功能受损和高血压的假说，以及2)探索导致人类高血压的CUL3突变导致CUL3底物泛素化受损的分子机制。这些研究在以下方面具有重要意义：蛋白质周转是血管平滑肌功能和动脉压调节的调节器，从机制上确定CUL3基因突变如何导致人类高血压，以及建立CUL3活性受损导致高血压的机制。该项目的长期目标是评估CUL3通路是否可以用作高血压的潜在治疗靶点。

 DESCRIPTION (provided by applicant): Ubiquitin ligases regulate protein turnover by promoting ubiquitination of substrate proteins which targets them for proteosomal degradation. CRL or Cullin-Ring ubiquitin Ligases comprise the largest class of evolutionarily conserved ubiquitin ligases. One member of this family, Cullin-3 (Cul3) plays an important role in arterial pressure regulation as mutations in the genes encoding Cul3 or Cul3 adaptor proteins cause dominant forms of hypertension. Our published evidence and preliminary data support a novel concept that vascular smooth muscle Cul3 plays a substantive role in arterial pressure regulation and its dysregulation causes hypertension. We hypothesize that Cul3 is a regulator of RhoA, a small GTPase which controls Rho kinase activity, calcium sensitivity, nitric oxide responsiveness, and contractile activity in vascular smooth muscle. Importantly, the role of vascular Cul3 expression and action in arterial pressure regulation has yet to be investigated. We will test the innovative concept that blood pressure is regulated, in part, through a Cul3-dependent pathway in vascular smooth muscle. Specifically, we hypothesize that a) impaired Cul3 activity causes hypertension, b) Cul3 mutants causing human hypertension do not properly ubiquitinate Cul3 substrates (such as RhoA), and c) Cul3 mutants act dominantly by interfering with wild-type endogenous Cul3. The aims of the project are to: 1) test the hypothesis that dominant interference of wildtype Cul3 by mutant Cul3 in vascular smooth muscle and vascular smooth muscle-specific deficiency in Cul3 results in impaired vasomotor function and hypertension, and 2) explore molecular mechanisms by which mutations in Cul3, which cause human hypertension result in impaired ubiquitination of Cul3 substrates. These studies are significant in advancing the concept that protein turnover is a regulator of vascular smooth muscle function and arterial pressure regulation, in mechanistically defining how mutations in Cul3 cause human hypertension, and in establishing mechanisms by which impaired Cul3 activity causes hypertension. The long term goal of this project is to assess if the Cul3 pathway can be used as a potential therapeutic target in hypertension.