Brain specific non-AT1, non-AT2 angiotensin binding site

描述（由申请人提供）：脑血管紧张素系统存在许多不确定性，其功能存在争议。然而，普遍认为脑血管紧张素导致高血压和其他心血管疾病。随着对血管紧张素II肽片段功能的认识（其中一些具有自己的受体），现在人们知道脑血管紧张素具有多种功能，远远超出了心血管系统的调节范围。我们最近在大脑中发现了一个非AT 1，非AT 2结合位点，这可能会给大脑血管紧张素系统增加额外的复杂性。它比任何一种主要的血管紧张素受体亚型的数量都要高，并且可以作为血管紧张素的一种新受体发挥作用，这种受体可能局限于大脑，或者它可能是一种高度特异性的血管紧张素酶，在血管紧张素肽的代谢中起关键作用。为了更好地理解这种结合位点，本项目旨在进一步表征这种新的、脑特异性的血管紧张素肽的非AT 1、非AT 2结合位点。第一个具体的目的是通过聚丙烯酰胺凝胶纯化和测序技术确定其生化特性，确定结合位点的氨基酸序列和结构。第二个具体目的是确定其药理学特异性，以确定该结合位点是否对血管紧张素肽具有特异性，或者是否具有更广泛的底物/配体特异性。第三个具体目标是研究结合位点在脑中的分布，并确定是否与改变的脑血管紧张素系统调节心血管系统或病理生理学状况有关，脑缺血，如中风、遗传性或实验性高血压和缺乏血管紧张素受体的转基因小鼠中的脑缺血，可以改变特定脑区域中该结合位点的表达。这些变化应该使我们能够做一个功能神经解剖评估其可能参与生理和病理生理的情况。预计这种蛋白质将被证明在脑血管紧张素系统的功能中具有相当重要的意义。由于脑血管紧张素系统因引起心血管疾病而臭名昭著，这项研究可能会导致开发新的治疗高血压和中风的治疗策略。然而，这种结合位点在大脑区域如Meynert的基底核、黑质、杏仁核、脊髓的延髓核和胶状质中以高浓度出现，可以解释脑血管紧张素系统参与阿尔茨海默病和帕金森病、应激和焦虑症、药物滥用和慢性疼痛的可能性。公共卫生相关性：心血管疾病，特别是高血压，是美国的主要死亡原因（2006年为629，000人）。除了导致心力衰竭和肾损伤外，高血压是中风的主要原因，2006年有137，000名美国人死于中风，并使许多其他人患有严重的运动和认知障碍。最常与心血管疾病发病率相关的激素是血管紧张素II（Ang II）。它可以说是最有效的血压升高激素。但除此之外，它还具有与引起高血压的能力分开的病理生理学效应。现在已知血管紧张素II是在大脑中产生的，对调节血压的大脑系统产生强大的影响。也许Ang II升高血压的能力的一半可能通过其在大脑中的作用发生。至少有一家制药公司正在研究专门针对脑血管紧张素系统的药物，以治疗高血压。然而，我们仍然不知道大脑血管紧张素系统如何工作。我们最近发现了一个新的结合位点的血管紧张素II是高度表达和广泛分布在整个大脑中的几个物种，包括人类。该建议旨在确定这种新的血管紧张素结合位点在脑中的结构特性和功能，以评估其在介导或拮抗血管紧张素II在脑中的病理生理作用中的作用。

DESCRIPTION (provided by applicant): There are many uncertainties about the brain angiotensin system and its functionality is controversial. However, it is generally accepted that brain angiotensin causes hypertension and other cardiovascular disorders. With the recognition of functionality of peptide fragments of angiotensin II some having their own receptors, it is now known that brain angiotensins have a multitude of functions extending well beyond regulation of the cardiovascular system. We recently discovered a non-AT1, non-AT2 binding site in the brain that may add an additional layer of complexity to the brain angiotensin system. It is present in higher quantities than either of the major angiotensin receptor subtypes and could function either as a novel receptor for angiotensins that may be limited to the brain, or it could be a highly specific angiotensinase that plays a critical role in the metabolism of angiotensin peptides. To better understand this binding site, this project is directed to further characterizing this novel, brain-specific non-AT1, non-AT2 binding site for angiotensin peptides. The first specific aim is to define its biochemical characteristics through polyacrylamide gel purification and sequencing techniques to determine the amino acid sequence and structure of the binding site. The second specific aim is to determine its pharmacological specificity to determine if this binding site is specific for angiotensin peptides or if it has a broader substrate/ligand specificity. The third specific aim will study the distribution of the binding site in the brain and ascertain whether conditions associated with altered brain angiotensin system regulation of the cardiovascular system or pathophysiological conditions, e.g., brain ischemia as in stroke, genetic or experimental hypertension and in transgenic mice lacking angiotensin receptors, can alter the expression of this binding site in specific brain regions. The changes should enable us to do a functional neuroanatomical assessment of its possible participation in physiological and pathophysiological circumstances. It is anticipated that this protein will prove to be of considerable importance in the functionality of the brain angiotensin system. Since the brain angiotensin system is notorious for causing cardiovascular disease, this research could lead to the development of novel therapeutic strategies for treatment of hypertension and stroke. However the occurrence of this binding site in high concentrations in brain regions such as the nucleus basalis of Meynert, substantia nigra, amygdala, nucleus accumbens and substantia gelatinosa of the spinal cord could explain the proposed involvement of the brain angiotensins system in Alzheimer's and Parkinson's Disease, stress and anxiety disorders, drug abuse and chronic pain. PUBLIC HEALTH RELEVANCE: Cardiovascular disease, especially hypertension, is the leading cause of death (629,000 in 2006) in the US. In addition to causing heart failure and kidney damage, hypertension is the primary cause of strokes, which killed 137,000 Americans in 2006, and leaves many others with severe motor and cognitive impairments. The hormone most commonly associated with cardiovascular morbidity is angiotensin II (Ang II). It is arguably the most potent blood pressure-raising hormone. But in addition, it has pathophysiological effects separate from its ability to cause high blood pressure. It is now known that Ang II is made in the brain and exerts powerful influences on the brain systems that regulate blood pressure. Perhaps half of Ang II's ability to raise blood pressure may occur via its actions in the brain. At least one drug company is investigating drugs that specifically target the brain angiotensin system as a treatment for high blood pressure. However, we still do not know how the brain angiotensin system works. We recently discovered a novel binding site for Ang II that is highly expressed and widely distributed throughout the brain in several species including humans. This proposal aims to determine the structural identity and functionality of this novel angiotensin binding site in the brain to assess its role in mediating or antagonizing the pathophysiological actions of Ang II in the brain.