Molecular Basis of Ang II Receptor Functions

描述（由申请方提供）：用于治疗高血压、心力衰竭和其他心血管疾病的血管紧张素受体阻滞剂（ARB）可防止血管紧张素II（Ang II）的血管紧张素1型受体（AT 1）的激活和信号转导。血管紧张素II与AT 1受体的结合激活信号转导，导致细胞内钙的动员，蛋白激酶的激活和基因转录的激活。然而，通过与AT 1受体结合，Ang II或ARB调节这些过程的分子机制尚不清楚。我们的长期目标是了解Ang II结合的AT 1受体如何激活多个信号转导过程以及ARB如何影响这一过程。为了实现这一目标，我们开发了Ang II类似物和受体突变体，它们在没有G蛋白激活的情况下激活ERK信号传导。目前的建议将解决两个问题：（1）如何AT 1选择性配体引导到受体的结合口袋？以及（2）G蛋白介导的和G蛋白非依赖的AT 1受体信号传导之间的差异在体内的结果是什么？我们将确定细胞外环（ECL）是否直接参与配体受体相互作用和AT 1受体的激活/抑制。我们预期ECL-2在受体的非活性状态（R）下与TM结构域相互作用，以及在活化状态下与Ang II相互作用（特异性目的1）。我们已经发现，AT 1受体在其他条件下不存在的Ang II激活的细胞中与β-抑制蛋白及其片段结合。我们将测试的假设，位点特异性β-抑制蛋白水解是一种新的信号模式与功能的后果。我们将确定β-arrestin切割的位点及其在Ang II激活细胞中的功能后果（特异性目的2）。G蛋白依赖性AT 1受体信号传导与G蛋白非依赖性信号传导不同，因为它引起ERK的核转位。我们将确定Ang II/AT 1受体诱导的ERK 1/2核转位在基因表达激活中的作用（特异性目的3）。这些研究对于更好地理解Ang II/AT 1受体作用机制和开发针对AT 1受体的改进药物至关重要。

DESCRIPTION (provided by applicant): Angiotensin receptor blockers (ARB) used in the treatment of hypertension, heart-failure and other cardiovascular disease conditions prevents activation and signal transduction by the angiotensin type 1 receptor (AT1) for angiotensin II (Ang II). Binding of Ang II to the AT1 receptor activates signal-transduction that leads to mobilization of intracellular calcium, activation of protein kinases, and activation of gene transcription. Yet the molecular mechanism of modulation of these processes by Ang II or ARBs via binding to the AT1 receptor is not clear. Our long-term goal is to understand how the Ang ll-bound AT1 receptor activates the multiple signal transduction process and how ARBs affect this process. Towards this goal, we have developed Ang II- analogs and receptor mutants that activate the ERK-signaling in absence of the G-protein activation. The current proposal will address two issues: (1) how are the AT1-selective ligands guided to the binding pocket in the receptor? and (2) what are the in vivo consequences of the differences between the G-protein mediated and the G-protein independent AT1 receptor signaling? We will determine whether the extracellular loops (ECL) directly participate in the ligand receptor interaction and the activation/inhibition of the AT1 receptor. We anticipate that ECL-2 interacts with the TM domain in an inactive state (R) of the receptor as well as with the Ang II in the activated state (Specific Aim 1). We have discovered that the AT1 receptor engages the beta-arrestin and its fragments in the Ang II activated cells which are absent under other conditions. We will test the hypothesis that site-specific beta-arrestin proteolysis is a novel signaling mode with functional consequences. We will determine the site of beta-arrestin cleavage and its functional consequences in Ang II activated cells (Specific Aim 2). G-protein-dependent AT1 receptor signaling differs from G-protein- independent signaling due to the fact that it causes nuclear translocation of ERK. We will determine the role of Ang ll/AT1 receptor-induced nuclear translocation of ERK 1/2 in activation of gene expression (Specific Aim 3). These studies are essential for a better understanding of the mechanism of Ang II/AT1 receptor action and the development of improved remedies targeting the AT1 receptor.