VASCULAR ANGIOTENSIN II RECEPTORS

肾素血管紧张素系统在心血管调节中是重要的， 血管紧张素II（angII）是其主要介质。 血管紧张素II激活 受体是重要的控制反应，但有 与许多其他受体相比， 其一级氨基酸结构是已知的。 血管紧张素II受体已经被 难以纯化和克隆。 我们现在已经从大鼠主动脉中分离出了cDNA 文库是编码具有受体特征的受体的克隆。 血管平滑肌Ang Ⅱ受体。 在转染了这个的COS细胞中， 克隆，[125 I] Sar 1-ile 8-ang II结合可饱和，Kd为0.3 nM， 并且受体具有适当的结合抑制效力系列 血管紧张素Ⅱ>血管紧张素Ⅲ>血管紧张素Ⅰ，血管紧张素Ⅱ的IC 50为1.6 nM。 的 非肽类“1型”angII受体拮抗剂DuP 753有效竞争 (IC50 6.2nM），而“2型”拮抗剂PD 123177不竞争。 转染的受体的这些特征与转染的受体的那些特征相同。 血管感受器 我们现在将利用这一进展， 以前关于血管紧张素Ⅱ受体次级信号机制的工作 直接探讨血管平滑肌的结构-功能 关系。 将对几个领域进行调查。 首先，我们将研究 血管紧张素II受体与G蛋白偶联超家族的关系 受体，因为它也通过G蛋白与磷脂酶C偶联。 第二，我们将试图解释相当大的异质性， ang II介导的药理学反应归因于 目前补助金的主要意见存在一个以上 周期-也就是说，血管血管紧张素II受体激活顺序 磷脂酶C和磷脂酶D，这意味着不同的阶段和 紧张信号机制。 这一问题涉及以下一般性问题： 一个受体如何与不同的效应机制结合。 实现 针对这些目标，我们提出三个具体目标：1. 严格描述 我们已经分离出cDNA克隆，并将其在结构上分类为 G蛋白偶联受体超家族; 2. 识别和 表征其他angII受体亚型;和3. 来定义 血管紧张素Ⅱ受体与不同效应物偶联结构决定因素 磷脂酶 这些数据将为分子生物学提供重要的见解。 血管紧张素II的作用机制，并应具有重要的意义， 了解血压的正常控制和高血压。 在 特别是，现在应该有可能解决的问题， 血管紧张素Ⅱ受体是高血压的候选基因。

The renin angiotensin system is important in cardiovascular regulation and angiotensin II (ang II) is its primary mediator. Ang II activates receptors that are important in control of responsiveness but which have been studied largely indirectly, in contrast with many other receptors for which primary amino acid structure is known. The ang II receptor has been difficult to purify and clone. We now have isolated from a rat aortic cDNA library a clone that encodes a receptor with characteristics of the vascular smooth muscle ang II receptor. In COS cells transfected with this clone, [125I] Sar1-ile8-ang II binding is saturable with a Kd of 0.3 nM, and the receptor has an appropriate potency series for binding inhibition of ang II>ang III>ang I, with an IC50 for ang II of 1.6 nM. The nonpeptidic "Type 1" ang II receptor antagonist DuP753 competes potently (IC50 6.2 nM), whereas the "Type 2" antagonist PD123177 does not compete. These features of the transfected receptor are identical to those of the vascular receptor. We shall now exploit this advance to extend our previous work on the secondary signalling mechanisms of the ang II receptor in vascular smooth muscle to explore directly the structure-function relationships. Several areas will be investigated. First, we will examine how the ang II receptor relates to the superfamily of G-protein coupled receptors, since it is also coupled to phospholipase C through a G-protein. Second, we will attempt to account for the considerable heterogeneity of ang II-mediated pharmacological responses putatively attributed to the existence of more than one of the major observations of the current grant period - namely, that the vascular ang II receptor activates sequentially a phospholipase C and a phospholipase D, implying different phasic and tonic signalling mechanisms. This issue relates to the general question of how one receptor couples to different effector mechanisms. To achieve these goals we propose three Specific Aims: 1. To characterize rigorously the cDNA clone that we have isolated and to classify it structurally within the superfamily of G-protein coupled receptors; 2. To identify and characterize other ang II receptor subtypes; and 3. To define the structural determinants of ang II receptor coupling to different effector phospholipases. These data will provide important insights into molecular mechanisms of action of ang II and should have important implications for understanding the normal control of blood pressure and hypertension. In particular, it should now be possible to address the issue of whether the ang II receptor is a candidate gene contributing to hypertension.