Human Angiotensin II Receptor Gene Regulation

血管平滑肌细胞（VSMC）的异常生长是各种心血管疾病如动脉粥样硬化、高血压和血管成形术后再狭窄的病理生理学中心。 这些异常可表现为VSMC增殖、分化状态、基因表达模式和形态学的改变。 目前，肽类激素血管紧张素II（Ang II）被认为在高血压和动脉粥样硬化的发展中起关键作用，因为它在VSMC中充当生长促进因子。 对Ang II的生物学反应是通过其与两种不同的高亲和力G蛋白偶联受体（GPCR）的相互作用介导的，这两种受体现在被命名为AT 1 R和AT 2 R。 在表征人AT 1 R（hAT 1 R）基因的同时，证明了人组织可以表达至少8种选择性剪接的hAT 1 R mRNA转录物，其仅在其5 '-非翻译区（5'-UTR）中不同。目前，人们对每个剪接变异体的功能意义或它们是如何被调控的知之甚少。 因此，该项目的长期目标是功能性地表征每个剪接变体，并研究控制这些mRNA表达的分子机制。 对这些过程的理解是至关重要的，因为hAT 1 R基因表达的异常转录、转录后和/或翻译调节可能导致hAT 1 R的过度表达，这将导致过度的Ang II反应性并可能导致心血管疾病。 该提案的具体目标是：1）检验hAT 1 R mRNA剪接变体在人体组织中差异表达的假设，并研究hAT 1 R基因通过远端和近端启动子区的转录调节，2）检验hAT 1 R mRNA剪接变体具有不同的mRNA半衰期的假设，其可由生理刺激调节，3）检验hAT 1 R mRNA剪接变体以不同效率翻译的假设，4）表征hAT 1 R mRNA 5 '-UTR的外显子-1中包含的内部核糖体进入位点（IRES），并鉴定识别该元件的反式作用因子，和5）检验“长”和“短”hAT 1 R同种型可以形成异源二聚体并且这些异源二聚体在功能上不同的假设。

Abnormal growth of vascular smooth muscle cells (VSMC) is central to the pathophysiology of various cardiovascular diseases such as atherosclerosis, hypertension and restenosis after angioplasty. These abnormalities can be manifested as changes in the state of VSMC proliferation, differentiation, gene expression patterns and morphology. Currently, the peptide hormone, angiotensin II (Ang II), is believed to play a pivotal role in the development of hypertension and atherosclerosis since it acts as a growth promoting factor in VSMC. The biological responses to Ang II are mediated by its interaction with two distinct high affinity G protein-coupled receptors (GPCRs) now designated AT1R and AT2R. While characterizing the human AT1R (hAT1R) gene, it was demonstrated that human tissues can express at least eight alternatively spliced hAT1R mRNA transcripts which differ only in their 5'-untranslated regions (5'-UTR). Currently, very little is known about the functional significance of each splice variant or how they are regulated. Therefore, the long term goals of this project are to functionally characterize each splice variant and to investigate the molecular mechanisms that govern the expression of these mRNAs. An understanding of these processes is critical since aberrant transcriptional, post- transcriptional and/or translational regulation of hAT1R gene expression may result in the over-expression of the hAT1R which would lead to exaggerated Ang II responsiveness and possibly result in cardiovascular disease. The Specific Aims of this proposal are to: 1) Test the hypothesis that hAT1R mRNA splice variants are differentially expressed in human tissues and investigate the transcriptional regulation of the hAT1R gene by the distal and proximal promoter regions, 2) Test the hypothesis that hAT1R mRNA splice variants have distinct mRNA half-lives, which can be regulated by physiological stimuli, 3) Test the hypothesis that hAT1R mRNA splice variants are translated with different efficiencies, 4) Characterize the internal ribosome entry site (IRES) harbored in exon-1 of the hAT1R mRNA 5'-UTR and identify trans-acting factors which recognize this element, and 5) Test the hypothesis that "long" and "short" hAT1R isoforms can form hetero-dimers and that these hetero-dimers are functionally distinct.