Molecular Basis of Ang II Receptor Functions

描述（由申请人提供）：我们研究项目的长期目标是阐明血管紧张素II 1型受体（AT 1 R）的结构-功能基础。血管紧张素II（AngII）是肾素-血管紧张素系统对心血管、肾脏和神经系统作用的经典介质。AngII诱导的亚细胞事件包括快速的第二信使反应，随后是各种信号转导级联的激活和基因的转录，包括早期生长反应、生长因子、细胞因子和氧化应激的基因。这些作用是由AngII与AT 1 R（一种七跨膜G蛋白偶联受体）结合引起的。如果AT 1 R活性没有被适当调节，AngII刺激变成慢性的并且可以损害细胞和组织，以及例如导致心肌（心力衰竭）、血管（动脉粥样硬化）或肾脏（肾衰竭）的慢性病症。抑制血管生成素II或AT 1 R阻滞剂（ARB）的药物可有效缓解高血压，许多心血管并发症，并防止人类终末器官损伤。然而，AT 1 R靶向治疗潜力尚未得到充分利用。我们已经证明了来自AT 1 R的G蛋白非依赖性信号传导。新的AT 1 R对Ang II的反应包括受体构象驱动的细胞质支架组装，其使AT 1 R能够与其他GPCR、生长因子受体或粘附受体发生串扰，并且能够形成具有改变的药理学的受体二聚体/寡聚体复合物。值得注意的是，新的AT 1 R支架复合物由“典型的信号”蛋白质组成，特别是增选G蛋白独立功能。我们的研究重点是AT 1 R的药理学、激活和信号传导的分子基础。我们建议，特定的构象变化诱导的激动剂和反激动剂结合，促进AT 1 R选择性地从事/排除信号转导蛋白;不同的图案暴露在动态构象变化过程中，使AT 1 R识别的细胞质或质膜蛋白，从而增加所产生的各种信号。我们将在三个特定目的下检验假设：特定目的1将确定ARB引起的AT 1 R抑制的构象和结构基础。具体目标2将确定机械牵张诱导的ERK 1/2激活所需的AT 1 R与粘附受体的相互作用。具体目标3将确定AT 1 R二聚体/寡聚体复合物形成的机制。这些拟议的研究将推进我们对AT 1 R生物学的认识。 公共卫生相关性：我们的研究将阐明血管活性激素AngII的多重信号应答和ARB疗效的分子基础。介导对AngII反应的受体是AT 1 R。AT 1 R激活的非经典通路可能参与心血管病理生理过程。对AT 1 R生物学这些方面的更深入了解可能为开发新的治疗方法提供独特的机会，以选择性地调节对治疗优势的反应。

DESCRIPTION (provided by applicant): The long-term goal of our research program is to elucidate the structure-function basis of angiotensin II type 1 receptor (AT1R). Angiotensin II (AngII) is the classical mediator of the effects of renin-angiotensin system on cardiovascular, renal and nervous systems. AngII induced sub-cellular events include rapid second messenger response followed by activation of various signal transduction cascades and transcription of genes including genes for early growth response, growth factors, cytokines and oxidative stress. These effects are elicited by the binding of AngII to the AT1R, a seven transmembrane G protein-coupled receptor. If the AT1R activity is not regulated properly, AngII stimulus becomes chronic and can damage the cells and tissue, as well as contribute to chronic disorders of myocardium (heart failure), blood vessels (atherosclerosis) or kidney (renal failure) for example. Drugs that inhibit the production of AngII or the AT1R blockers (ARB) are prescribed to effectively alleviate hypertension, many cardiovascular complications and to prevent end-organ damage in humans. However, the AT1R-targeted therapeutic potential is not fully harnessed. We have shown G protein- independent signaling from AT1R. The novel AT1R responses to Ang II includes receptor conformation driven assembly of cytoplasmic scaffolds that enable AT1R crosstalk with other GPCRs, growth factor receptors or adhesion receptors and a capacity to form receptor dimer/oligomer complexes with altered pharmacology. Remarkably, the novel AT1R scaffolding complexes consist of "typical signaling" proteins specifically co-opted for G protein independent function. Focus of our research has been the molecular basis of AT1R pharmacology, activation and signaling. We propose that specific conformational changes are induced by agonist and inverse-agonist binding which facilitate AT1R to selectively engage/exclude signal transduction proteins; different motifs exposed during the dynamic conformational changes enable the AT1R to recognize the cytoplasmic or plasma membrane proteins and thereby increase the variety of signals that are generated. We will test the hypothesis under three Specific Aims: Specific Aim 1 will determine the conformational and structural basis of AT1R inhibition caused by ARBs. Specific Aim 2 will determine the AT1R interactions with the adhesion receptor required for mechanical stretch-induced ERK1/2 activation. Specific Aim 3 will determine the mechanism by which AT1R dimer/oligomer complexes are formed. These proposed studies will advance our knowledge of AT1R biology. PUBLIC HEALTH RELEVANCE: Our studies will elucidate the molecular basis for the multiple signaling response to the vasoactive hormone AngII and the efficacy of ARBs. The receptor which mediates the response to AngII is AT1R. The non- canonical pathways activated by AT1R may contribute to the progression of cardiovascular pathophysiology. A deeper understanding of these aspects of AT1R biology may offer unique opportunities to develop new therapeutics to modulate responses selectively to therapeutic advantage.