VASCULAR ANGIOTENSIN II RECEPTORS

肾素-血管紧张素系统在心血管调节和 血管紧张素II(Ang II)是其主要介体。血管紧张素II激活 受体在控制反应性方面很重要，但 与许多其他受体相比，在很大程度上是间接研究的 已知的主要氨基酸结构是什么。血管紧张素II受体已经被 难以提纯和克隆。我们现在已经从一只大鼠的主动脉中分离出了cDNA 文库：一种克隆，编码一种具有以下特征的受体 血管平滑肌血管紧张素Ⅱ受体。在COS细胞中转染此基因 克隆，[125I]Sar1-ile8-Ang II结合是可饱和的，Kd为0.3 nM， 并且受体有一系列合适的结合抑制效力 Ang II&Gt；Ang III&Gt；Ang I，Ang II的IC50为1.6 NM。这个 非肽类“1型”血管紧张素Ⅱ受体拮抗剂DuP753的强势竞争 (IC50 6.2 nM)，而“2型”拮抗剂PD123177不竞争。 转基因受体的这些特征与转基因受体的特征相同。 血管受体。我们现在将利用这一进展来延长我们的 血管紧张素Ⅱ受体二级信号传导机制的研究进展 在血管平滑肌中直接探索结构-功能 两性关系。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，因为它还通过G蛋白与磷脂酶C偶联。 其次，我们将尝试解释 血管紧张素转换酶II介导的药理作用可能归因于 存在当前赠款的一项以上主要观察结果 周期--即血管血管紧张素Ⅱ受体顺次激活 A磷脂酶C和A磷脂酶D，意味着不同的时相和 紧张性信号机制。这一问题涉及到 一个受体如何耦合到不同的效应器机制。要实现 这些目标我们提出了三个具体目标：1.严格描述 我们分离到的cdna克隆并对其进行结构分类。 G蛋白偶联受体超家族；2.鉴定和鉴定 鉴定其他Ang II受体亚型；以及3.定义 血管紧张素Ⅱ受体与不同效应器偶联的结构决定因素 磷脂酶。这些数据将为分子研究提供重要的见解 血管紧张素转换酶II的作用机制应对 了解血压和高血压的正常控制。在……里面 特别是，现在应该可以解决这个问题，即 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.