3UTR DETERMINANTS IN ANGIOTENSIN II RECEPTOR REGULATION

血管紧张素II是一种多功能肽激素，它调节血压和体液平衡，并作为某些细胞类型的生长因子。血管紧张素II通过细胞表面鸟嘌呤核苷酸调节蛋白（g蛋白）偶联受体作用于多种靶组织，虽然已经确定了多种受体亚型，但大多数已知的功能是通过AT1A受体亚型介导的。AT1A表达和信号通路通过受体偶联发生在组织特异性的方式。细胞对这些过程的控制尚不清楚。近年来，许多基因的信使RNA 3'非翻译区已被确定为mRNA转录物本身以及翻译产物的重要调节因子。在本应用中，我们提出证据表明，AT1A的3'非翻译区在决定该受体与细胞内信号通路的偶联中起着重要作用。特别是，AT1A与[特异性g蛋白]的偶联，cAMP调节和生长反应（增生/肥大）是由3'非翻译区决定的。AT1A受体的3'非翻译区能够显著改变其翻译蛋白功能的机制是本提案的主要焦点。我们有额外的证据支持这一假设，即特定的mRNA结合蛋白识别AT1A mRNA的3'非翻译区域内的序列，从而改变细胞功能。我们建议表征AT1A mRNA的3'非翻译区，以了解这一重要受体的生物化学和组织特异性表达和信号传导。具体而言，我们将首先确定AT1A 3'非翻译区在控制受体功能中的调节作用，并确定信号事件中的功能变化和改变。其次，我们将确定3‘非翻译区中通过与mRNA结合蛋白相互作用来控制受体功能的序列，并阐明3’非翻译区控制生理反应的机制。第三，我们将鉴定和克隆mRNA结合蛋白的cdna，以确定mRNA结合蛋白与受体特定3'非翻译区序列相互作用的功能意义。了解mRNA结合蛋白及其在AT1A等特定蛋白的生物学功能调控中的作用，将有助于深入了解负责调节细胞功能和信号通路耦合的协调作用。从更广泛的意义上说，澄清AT1A在分子水平上的功能将有助于我们理解肾素血管紧张素系统（主要是血管紧张素II对AT1A的作用）在控制正常生理稳态中的作用，以及该系统在疾病状态下的畸变关联。

Angiotensin II is a multifunctional peptide hormone which regulates blood pressure and fluid balance as well as acting as a growth factor for some cell types. Angiotensin II acts on a variety of target tissues through cell surface guanine nucleotide regulatory protein (G-protein) coupled receptors, and while multiple receptor subtypes have been identified, most known functions are mediated through the AT1A receptor subtype. AT1A expression and signaling pathways through which receptor couple occur in a tissue specific manner. The cellular control of these processes in not known. Recently, the messenger RNA 3' untranslated region of many genes has been identified as an important regulator of the mRNA transcript itself, as well as the translated product. In this application, we present evidence that the 3' untranslated region of the AT1A has a significant role in dictating the coupling of this receptor to intracellular signaling pathways. In particular, the coupling of the AT1A to [specific G-protein,] cAMP modulation and growth responses (hyperplasia/hypertrophy) are determined by the 3' untranslated region. The mechanisms by which the 3' untranslated region of the AT1A receptor can dramatically alter the function of its translated protein is the primary focus of this proposal. We have additional evidence to support the hypothesis that specific mRNA binding proteins recognize sequences within the 3' untranslated region of the AT1A mRNA and, thereby, alter cell function. We propose to characterize the 3' untranslated region of the AT1A mRNA to understand the biochemistry and tissue specific expression and signaling of this important receptor. Specifically, we will first determine the regulatory role of AT1A 3' untranslated region in controlling receptor function and identify the functional changes and alterations in signaling events. Second, we will determine the sequences in the 3' untranslated region which control receptor function by interacting with mRNA binding proteins and elucidate the mechanisms employed by the 3' untranslated region in controlling physiological responses. Third, we will identify and clone the cDNAs of the mRNA binding proteins inorder to determine the functional significance of mRNA binding proteins interacting with specific 3' untranslated region sequences of the receptor. Understanding the mRNA binding proteins and their role in the regulation of biological functions of specific proteins like the AT1A will provide insight into the coordinate actions responsible for regulating cellular functions and coupling to signaling pathways. In a broader sense, clarification of AT1A function at the molecular level will contribute to our understanding of the renin angiotensin system (primarily Angiotensin II actions on AT1A) in controlling normal physiological homeostasis as well as the association of aberrations of the system in disease states.