EFFCTS OF ANOVEL NTERACTING MOLECULE OFAT1 RECEPTOR ON RENAL FUNCTION

循环血管紧张素II （Ang II）的慢性升高引起持续高血压，并通过Ang II型1受体（AT1受体）依赖性过程增强肾内Ang II的积累。以往的研究表明，AT1受体的c端胞质结构域参与了受体内化的控制，并参与了受体介导的信号转导与特异性生物反应的联系。我们之前克隆了一个新的AT1受体相关蛋白（ATRAP）分子，它可以特异性地与AT1受体的c端相互作用。先前的体外研究结果表明，ATRAP通过组成性激活AT1受体内化，特异性抑制AT1受体信号传导，减少细胞表面AT1受体数量。本研究验证了循环中Ang II的慢性升高以组织特异性方式调节ATRAP蛋白表达的假设。以C57BL6小鼠为研究对象，分别以1000 ng/kg/min或对照体为剂量，经渗透微泵皮下注射。在第12天，注射angii的小鼠的收缩压平均为176+/-1.0 mm Hg，而给药的小鼠的收缩压为122+/-4 mm Hg。使用抗at1受体和抗atrap抗体进行Western blot分析。结果显示，肾和肝脏中AT1受体蛋白水平在Ang II和载药小鼠中是相当的。相比之下，angii输注小鼠肾脏中ATRAP蛋白水平显著降低（降低51%，P<0.05）。两组肝脏中ATRAP蛋白水平也相似。因此，这些结果表明，在Ang ii诱导的高血压中，肾脏和肝脏AT1受体基因表达得到维持，但肾脏ATRAP基因表达被特异性抑制。通过输注Ang II对ATRAP/AT1受体表达比例的肾特异性下调，导致肾脏中AT1受体信号传导相对优于ATRAP抑制，从而允许Ang II慢性升高的持续效应引起血压的进行性升高。少

Chronic elevations of circulating angiotensin II (Ang II) cause sustained hypertension and enhanced accumulation of intrarenal Ang II by an Ang II type 1 receptor (AT1 receptor) -dependent process. Previous studies showed that the C-terminal cytoplasmic domain of AT1 receptor is involved in the control of receptor internalization and in linking receptor-mediated signal transduction to the specific biological response. We previously cloned a novel molecule ATRAP (AT1 receptor-associated protein) that specifically interacts with C-terminal of AT1 receptor. The results of previous in vitro studies showed that ATRAP specifically inhibits AT1 receptor signaling by constitutive activation of AT1 receptor internalization to decrease cell surface AT1 receptor number. The present study tested the hypothesis that chronic elevations in circulating Ang II regulate ATRAP protein expression in a tissue-specific manner. C57BL6 mice were infused with Ang II (1,000 ng/kg/min)or vehicle subcutaneously f … More or 14 days via osmotic minipump. On day 12, systolic blood pressure averaged 176+/-1.0 mm Hg in Ang II-infused mice compared with mice given vehicle (122+/-4 mm Hg) .Western blot analysis using the anti-AT1 receptor and anti-ATRAP antibodies was performed. The results showed that AT1 receptor protein levels in the kidney and liver were comparable in Ang II- and vehicle-infused mice. In contrast, ATRAP protein levels were significantly decreased in the kidney of Ang II-infused mice (51% decrease; P<0.05). ATRAP protein levels in the liver were also similar in the two groups. Therefore, these "results indicate that renal and liver AT1 receptor gene expression is maintained but renal ATRAP gene expression is specifically suppressed in Ang II-induced hypertension. The renal-specific down-regulation of the ratios of ATRAP/AT1 receptor expression by Ang II infusion causes the relative predominance of AT1 receptor signaling over inhibition by ATRAP in the kidney and thus allows the sustained effects of chronic elevations in Ang II to elicit progressive increases in blood pressure. Less