Reis Rosana I, Santos Edson L, Pesquero João B, Oliveira Laerte, Schanstra Joost P, Bascands Jean-Loup, Pecher Christiane, Paiva Antonio C M, Costa-Neto Claudio M
Department of Biochemistry and Immunology, Faculty of Medicine of Ribeirão Preto, University of São Paulo, 14049-900 Ribeirão Preto, Brazil.
Regul Pept. 2007 Apr 5;140(1-2):32-6. doi: 10.1016/j.regpep.2006.11.028. Epub 2007 Jan 18.
Most of the classical physiological effects of the octapeptide angiotensin II (AngII) are produced by activating the AT1 receptor which belongs to the G-protein coupled receptor family (GPCR). Peptidic GPCRs may be functionally divided in three regions: (i) extracellular domains involved in ligand binding; (ii) intracellular domains implicated in agonist-induced coupling to G protein and (iii) seven transmembrane domains (TM) involved in signal transduction. The TM regions of such receptors have peculiar characteristics such as the presence of proline residues. In this project we aimed to investigate the participation of two highly conserved proline residues (Pro82 and Pro162), located in TM II and TM IV, respectively, in AT1 receptor signal transduction. Both mutations did not cause major alterations in AngII affinity. Functional assays indicated that the P162A mutant did not influence the signal transduction. On the other hand, a potent deleterious effect of P82A mutation on signal transduction was observed. We believe that the Pro82 residue is crucial to signal transduction, although it is not possible to say yet if this is due to a direct participation or if due to a structural rearrangement of TM II. In this last hypothesis, the removal of proline residue might be correlated to a removal of a kink, which in turn can be involved in the correct positioning of residues involved in signal transduction.
八肽血管紧张素II（AngII）的大多数经典生理效应是通过激活属于G蛋白偶联受体家族（GPCR）的AT1受体产生的。肽类GPCR在功能上可分为三个区域：（i）参与配体结合的细胞外结构域；（ii）参与激动剂诱导的与G蛋白偶联的细胞内结构域；（iii）参与信号转导的七个跨膜结构域（TM）。这类受体的TM区域具有独特的特征，如存在脯氨酸残基。在本项目中，我们旨在研究分别位于TM II和TM IV的两个高度保守的脯氨酸残基（Pro82和Pro162）在AT1受体信号转导中的作用。两种突变均未引起AngII亲和力的重大改变。功能分析表明，P162A突变体不影响信号转导。另一方面，观察到P82A突变对信号转导有强烈的有害作用。我们认为Pro82残基对信号转导至关重要，尽管目前还无法确定这是由于其直接参与还是由于TM II结构重排所致。在后一种假设中，脯氨酸残基的去除可能与扭结的去除相关，而扭结又可能参与信号转导相关残基的正确定位。
