Dopamine and Angiotensin Receptor Interactions in Genetic Hypertension

高血压和盐敏感性是人类发病和死亡的主要原因。然而，在了解病因或个人遗传学、生化调节和环境影响之间的联系方面进展缓慢。我们的研究表明，两种肾调节途径，即多巴胺（抑制性）和血管紧张素（刺激性），在高血压和盐敏感性的病因学中起核心作用。我们报道了G蛋白偶联受体激酶4型（GRK4）活性的增加，由于激活变异，直接导致原发性高血压患者肾近端小管细胞（RPTCs）中多巴胺受体和血管紧张素受体的失调。在动物模型中，过表达GRK4y野生型基因的转基因小鼠为正常血压，而GRK4y 142V转基因小鼠为高血压和盐敏感，而GRK4y486V转基因小鼠为盐敏感。本项目的总体目标是研究肾小管细胞中多巴胺和血管紧张素受体之间的反式调节的新机制，包括蛋白质降解。这些新的机制将在新的小鼠模型中进行检验，在人体中，体内肾功能研究将与从同一个体获得的新鲜空化肾小管细胞的研究相关联。在行政、分析和动物核心实验室的支持下，项目1将测试一种假设，即多巴胺能和血管紧张素受体与几种关键调节蛋白（DiR、D5R、ATiR和GRK4）之间的新型时空相互作用发生在脂筏中，并由人类RPTCs中caveolin-1和GRK4之间的相互作用调节。我们还假设，caveolin-1对DiR功能的促进作用受到GRK4基因变异的损害。项目2将验证这样的假设，即在正常人中，adir介导的抗尿被DiRs和D3RS共同对抗，而这种保护机制在原发性高血压患者中缺乏。来自特定受试者的选择性多巴胺能和血管紧张素系统刺激的生理反应将与来自同一受试者的尿源性细胞的单个肾细胞生理反应相关。这将使我们能够将肾功能反应与同一主题的肾细胞研究联系起来。项目3将验证以下假设：D3R表达或功能下降（由GRK4基因变异引起）引起的高血压是由于NHE3、NCC和ENaC的活性和表达增加所致；它们的表达增加是由于USP48的去泛素化（又称去泛素化）导致降解减少所致。这项基础和转化资助申请将为多巴胺能和肾素-血管紧张素系统之间的相互作用提供新的见解，并提供新的见解，这将导致新的治疗方法。

Hypertension and salt sensitivity are major contributors to human morbidity and mortality. However, there has been slow progress in the understanding of the etiology or the link between personal genetics, biochemical regulation, and environmental influences. Our work has shown that two renal regulatory pathways that counter-regulate sodium reabsorption in the renal tubule, namely, dopamine (inhibitory) and angiotensin (stimulatory), are central in the etiology of hypertension and salt sensitivity. We have reported that increased activity of G protein-coupled receptor kinase type 4 (GRK4), because of activating variants, directly causes the dysregulation of dopamine receptors, as well as the angiotensin receptors, in renal proximal tubule cells (RPTCs) from humans with essential hypertension. In animal models, transgenic mice over expressing GRK4y wild-type gene are normotensive, while GRK4Y 142V transgenic mice are hypertensive and salt-sensitive, while GRK4y486V transgenic mice are salt-sensitive. The overall objective of this program project is the study of novel mechanisms of trans-regulation, including protein degradation, between the dopamine and angiotensin receptors in renal tubule cells. These novel mechanisms will be examined in novel mouse models, and in humans in whom in vivo renal functional studies will be correlated with studies in freshly voided renal tubule cells obtained from the same individual. Supported by administrative, analytical, and animal core laboratories, Project 1 will test the hypothesis that novel spatiotemporal interactions between and among dopaminergic and angiotensin receptors and several key regulatory proteins (DiR, D5R, ATiR, and GRK4) occur in lipid rafts and are regulated by the interaction between caveolin-1 and GRK4 in human RPTCs. We also hypothesize that the facilitatory effect of caveolin-1 on DiR function is impaired by GRK4 gene variants. Project 2 will test the hypothesis that ATiR-mediated antinatriuresis is opposed by DiRs and D3RS, acting in concert in normal human subjects, and that this protective mechanism is deficient in patients with essential hypertension. The physiologic responses to selective dopaminergic and angiotensin system stimulation from a specific subject will be correlated with single renal cell physiological responses from the urine-derived cells obtained from the same subject. This will enable us to correlate renal functional responses with renal cellular studies in the same subject. Project 3 will test the hypothesis that the hypertension that occurs with decreased D3R expression or function (caused by GRK4 gene variants) is due to increased activity and expression of NHE3, NCC, and ENaC; their increased expression is caused by decreased degradation due to their deubiquitination (a.k.a. deubiquitinylation) by USP48. This basic and translational grant application will delineate new insights into the interactions between the dopaminergic and renin-angiotensin systems and provide new insight that will lead to new therapeutic approaches.