MOLECULAR STUDIES ON ANGIOTENSIN II RECEPTORS

描述（改编自研究者摘要）：八肽 血管紧张素II（Ang II）长期以来被认为是血管紧张素II的关键组分。 神经内分泌控制心血管功能。 AngII还扮演了一个 在两栖动物和哺乳动物卵母细胞的发育中起重要作用。 血管紧张素II通过与其高亲和力受体结合发挥作用 AT 1和AT 2。 这两种受体都具有七个跨膜区 拓扑结构和34%的氨基酸同一性。 AT 2诱导的反应 受体对百日咳毒素敏感，表明该受体是一种 Gi蛋白偶联受体 然而，这种受体并没有表现出 GTP-γ诱导转变为低亲和力形式，其特征在于 G蛋白连接受体 因此，有人建议， 受体通过非经典的Gi型G蛋白介导其作用。 本实验室研究的长期目标是：a） 理解配体诱导的细胞反应是如何调节的，和B） 阐明受体介导的信号转导如何调节 决定细胞命运（生长或凋亡）的分子开关。 本提案的主要目的是分析结构-功能 大鼠AT 2受体的关系，并阐明细胞内 响应于Ang II的结合而激活的信号级联 当在非洲爪蟾卵母细胞中表达时，与该受体结合。 我们最近的发现 表明在爪蟾卵母细胞中表达大鼠AT 2受体的激活 导致细胞内IP 3水平升高。 然而，Ang II 与非洲爪蟾卵母细胞中表达的大鼠AT 2受体结合， 细胞内IP 3水平升高。 然而，血管紧张素Ⅱ结合大鼠 非洲爪蟾卵母细胞中表达的AT 2受体对GTP γ S不敏感。 因此，PI假设大鼠AT 2受体介导的活化 在爪蟾卵母细胞中磷脂酶C途径的作用也是通过 这些细胞内源性的非经典Gi蛋白。 实验 旨在确定和表征这种内源性介质的性质， 将大鼠AT 2受体与PLC途径偶联。 为此，PI建议 研究AT 2受体的结构与功能关系， 定点突变体和AT 2：AT 1嵌合蛋白。 PI还建议 分析大鼠AT 2受体激活的其他信号机制 在非洲爪蟾卵母细胞中。 PI希望这些研究能够提供新的见解 AT 2受体的信号转导及其在卵母细胞中的可能作用 发展

DESCRIPTION (Adapted from Investigator's Abstract): The octapeptide angiotensin II (Ang II) has long been recognized as a key component in the neuroendocrine control of cardiovascular function. Ang II also plays an important role in the development of oocytes in both amphibians and mammals. Angiotensin II exerts its effects by binding to its high affinity receptors AT1 and AT2. Both of these receptors share seven-transmembrane domain topology and 34% amino acid identity. The responses induced by the AT2 receptor are sensitive to pertussis toxin suggesting that this receptor is a Gi-protein-coupled receptor. However, this receptor does not demonstrate the GTP-gamma induced shift to a low affinity form that is characteristic of the G-protein-linked receptors. Therefore it was suggested that this receptor mediates its effects through a non-classical, Gi type G-protein. The long-term objectives of the research in this laboratory are: a) to understand how the ligand-induced responses of a cell are regulated, and b) to elucidate how the receptor-mediated signal transduction regulates the molecular switch that determines the fate (growth or apoptosis) of a cell. The primary objective of this proposal is to analyze the structure-function relationship of rat AT2 receptor and to elucidate what are the intracellular signaling cascades that are activated in response to the binding of Ang II to this receptor when expressed in Xenopus oocytes. Our recent findings indicate that activation of rat AT2 receptor expressed in Xenopus oocytes causes an elevation in the intracellular IP3 levels. However, Ang II binding to rat AT2 receptors expressed in Xenopus oocytes causes an elevation in the intracellular IP3 levels. However, Ang II binding to rat AT2 receptors expressed in Xenopus oocytes is not sensitive to GTPgammaS. Therefore, the PI hypothesizes that the rat AT2 receptor mediated activation of the phospholipase C pathway in Xenopus oocytes is also effected through a non-classical Gi-protein endogenous to these cells. Experiments are directed to identify and characterize the nature of this endogenous mediator that couples rat AT2 receptor to PLC pathway. To do this, the PI proposes to study the structure-function relationship of AT2 receptor by generating site-directed mutants and AT2:AT1 chimeric proteins. The PI also proposes to analyze what other signaling mechanisms are activated by rat AT2 receptor in Xenopus oocytes. The PI hopes these studies will provide new insights into the signaling by AT2 receptor and its possible role in oocyte development.