Angiotensin Receptor Regulation By Upstream Short Open Reading Frames

描述（由申请人提供）：血管紧张素II （Ang II）在体液稳态和血压（BP）中起关键作用。我们最近发现，在血管紧张素1a型受体（AT1aR） mRNA 5'先导序列2外显子的短开放阅读框中编码的7个氨基酸肽（PEP7）抑制细胞外信号调节蛋白激酶1和2 （Erk1/2）的Ang II激活，并调节细胞内AT1aR的运输。PEP7还能显著减少Ang II介导的钠摄入量，而对Ang II介导的水摄入量没有任何影响，并能拮抗Ang II诱导的血压升高。Aim 1将确定PEP7抑制Erk1/2激活的信号机制。我们将验证PEP7对Erk1/2活化的抑制是依赖于Ang II的，并通过AT1aR-G蛋白不依赖的ß-阻滞蛋白信号通路介导。我们还将使用药理学和分子方法以及共聚焦显微镜研究PEP7通过抑制AT1aR与ß-阻滞蛋白途径的偶联来调节AT1aR囊泡运输。目的2将阐明PEP7调节体液和电解质稳态的机制。我们将在钠摄入量升高的病理生理模型中研究PEP7在体内的作用，包括低钠血症和等渗性低血容量，以及调节中枢催产素和抗利尿激素途径的条件，以及选择性抑制G蛋白介导的蛋白激酶C和G蛋白独立的Erk1/2信号级联的条件。目的3将通过研究PEP7对Ang II和儿茶酚胺依赖性高血压模型中动脉压的影响来确定PEP7的降压作用是否依赖于Ang II。我们还将确定PEP7在两种盐敏感性模型中是否有效降低血压，以及减少钠摄入量在这些效果中所起的作用。通过实现这些目标，我们将获得对PEP7生物学的深入了解，这可能有助于开发新的干预措施，以治疗因饮食钠而恶化的疾病，如盐敏感性高血压。

DESCRIPTION (provided by applicant): Angiotensin II (Ang II) plays a key role in fluid homeostasis and blood pressure (BP). We have recently found that a seven amino acid peptide (PEP7) encoded within a short open reading frame in exon 2 of the 5' leader sequence of the angiotensin type 1a receptor (AT1aR) mRNA inhibits Ang II activation of extracellular signal-regulated protein kinases 1 and 2 (Erk1/2) and regulates AT1aR trafficking in cells. PEP7 also markedly reduced Ang II-mediated sodium intake without having any effect on Ang II-mediated water intake and it antagonized Ang II- induced increases in BP. Aim 1 will determine the signaling mechanism by which PEP7 inhibits Erk1/2 activation. We will test the hypothesis that PEP7 inhibition of Erk1/2 activation is Ang II dependent and mediated via the AT1aR-G protein-independent ß-arrestin signaling pathway. We will also investigate PEP7 regulation of AT1aR vesicular trafficking by inhibiting AT1aR coupling to the ß-arrestin pathway using both pharmacological and molecular approaches, and confocal microscopy. Aim 2 will elucidate the mechanism by which PEP7 regulates fluid and electrolyte homeostasis. We will investigate PEP7 effects in vivo in pathophysiological models of elevated sodium intake including hyponatremic hypovolemia and isotonic hypovolemia as well as conditions that modulate central oxytocin and vasopressin pathways and those that selectively inhibit G protein-mediated protein kinase C and G protein-independent Erk1/2 signaling cascades. Aim 3 will determine if the antihypertensive effects of PEP7 are Ang II-dependent by investigating PEP7 effects on arterial pressure in models of Ang II- and catecholamine- dependent hypertension. We will also determine if PEP7 is effective at lowering BP in two models of salt-sensitivity and what role reduced sodium intake plays in these effects. By achieving these aims, we will gain insight into PEP7 biology that could be leveraged toward developing novel interventions for diseases that are worsened by dietary sodium, like salt- sensitive hypertension.