MOLECULAR STUDIES ON ANGIOTENSIN II RECEPTORS

描述(改编自《调查者摘要》)：八肽 血管紧张素II(Ang II)长期以来一直被认为是 心血管功能的神经内分泌控制。Ang II还扮演一个 在两栖动物和哺乳动物的卵母细胞发育中起着重要的作用。 血管紧张素II通过与其高亲和力受体结合发挥作用 AT1和AT2。这两种受体都有七个跨膜结构域 拓扑结构和34%的氨基酸同源性。AT2诱导的反应 受体对百日咳毒素敏感，提示该受体是一种 Gi-蛋白偶联受体。然而，这种受体并不能证明 GTP-γ诱导向低亲和力形式转变，其特征是 与G蛋白相关的受体。因此，有人建议这一点 受体通过一种非经典的胃肠型G蛋白来调节其作用。 本实验室研究的长期目标是：a) 了解配体诱导的细胞反应是如何调节的，以及b) 为了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。 这项建议的主要目标是分析结构-功能 大鼠血管紧张素Ⅱ受体与细胞内是什么的关系 Ang II结合后激活的信号级联反应 在非洲爪哇卵母细胞中表达时对该受体的作用。我们最新的发现 非洲爪哇卵母细胞中表达的大鼠AT2受体的激活 导致细胞内IP3水平升高。然而，Ang II 与非洲爪哇卵母细胞表达的大鼠AT2受体结合可引起 细胞内IP3水平升高。然而，Ang II与大鼠结合 非洲爪哇卵母细胞表达的AT2受体对GTP-GammaS不敏感。 因此，PI假设大鼠AT2受体介导的激活 在非洲爪哇卵母细胞中磷脂酶C途径的作用也通过一种 这些细胞内源性的非经典Gi蛋白。实验是 旨在识别和表征这种内源性介体的性质 将大鼠AT2受体与PLC通路偶联。为了做到这一点，国际刑警组织建议 用生成法研究AT2受体的构效关系 定点突变体和AT2：AT1嵌合蛋白。印度人民党还建议 分析大鼠AT2受体激活的其他信号机制 在非洲爪哇的卵母细胞中。国际刑警组织希望这些研究将提供新的见解 AT2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.