Characterization And Pharmacology Of Receptors For Bombe

炸弹素相关肽（[胃泌素释放肽[GRP]，神经介质素B]）与两种不同的受体（GRP-R, NMB- R）相互作用，介导胃肠道（GI），中枢神经系统（CNS）以及正常和肿瘤组织生长的一系列作用。此外，最近还发现了两个相关受体，一个是与GRP-R具有60%同源性的哺乳动物孤儿受体（BRS-3），另一个是两栖动物的新受体BB-4-R。该项目的目的是了解这些受体的药理学、分子药理学和细胞生物学，以及开发可用于确定其生理作用的特异性激动剂和拮抗剂。正在进行的研究包括在细胞生物学和药理学上与天然受体相似的稳定细胞系中表达这些受体；利用位点定向诱变和受体嵌合体的研究来确定受体结构决定体的选择性和受体拮抗剂和拮抗剂的特异性；bn相关肽的药理学研究来确定选择性激动剂/拮抗剂；研究天然细胞和转染细胞来确定这些受体的转导级联。利用受体模型和诱变研究，我们最近设计了一种BRS-3受体的选择性激动剂（J.Biol.Chem）。（276, 9219-9229, 2001），并描述了两种高亲和力肽拮抗剂对GRP受体选择性的分子基础（J. Biol. 2001）。化学，276,36652-36663,2001)。在BRS-3研究之前，BRS-3受体没有选择性配体，限制了研究其生理作用的能力。利用构象受限的[B-Ala112] bombesin类似物和模型，我们确定了氨基-3苯基丙酸类似物作为第一个选择性BRS-3激动剂。在第二项研究中，GRP受体第4胞外结构域（EC）中存在的三个氨基酸被确定为拮抗剂选择性的关键残基，这种选择性是由阳离子- π相互作用和氢结合介导的。

Bombesin-related peptides ([gastrin-releasing peptide [GRP], neuromedin B) interact with two distinct receptors (GRP-R, NMB- R) to mediate a number of effects in the gastrointestinal tract (GI), central nervous sytem (CNS) and on growth of normal and neoplastic tissues. Furthermore, two related receptors, a mammalian orphan receptor (BRS-3), having 60% homology to GRP-R and a novel receptor in amphibians, BB-4-R has been described recently. The aims of this project are to understand the pharmacology, molecular pharmacology, and cell biology of these receptors as well as to develop specific agonists and antagonists that can be used to determine their physiological roles. Investigations being performed include expression of these receptors in stable cell lines that resemble native receptors in their cell biology and pharmacology; investigations using site-directed mutagenesis and receptor chimeras to define receptor structural determinants of ligand selectivity and specificity for agonists and antagonists, pharmacological studies of BN-related peptides to identify selective agonists/antagonists and studies of native cells and transfected cells to define the transduction cascades of these receptors. Using receptor modeling and mutagenesis studies we have recently designed a selective agonist for the BRS-3 receptor (J.Biol.Chem. 276, 9219-9229, 2001), as well as characterized the molecular basis for the selectivity of two high affinity peptide antagonists for the GRP receptor (J. Biol. Chem. 276, 36652-36663, 2001). Prior to the BRS-3 study, no selective ligands existed for the BRS-3 receptor restricting the ability to investigate its physiological roles. Using conformationally restricted analogues of [B-Ala112] bombesin and modeling we identified an amino-3 phenyl propionic acid analogue as the first selective BRS-3 agonist. In the second study the presence of three amino acids in the 4th extracellular domain (EC) of the GRP receptor were identified as the critical residues for the antagonists selectivity and this selectivity was mediated by cation-pi interactions and hydrogen binding.