Characterization And Pharmacology Of Receptors For Gastrointestinal Peptides

各种胃肠肽的药理学和分子药理学正在研究中。一个肽受体家族集中在这一年：那些蛙皮素（Bn）相关肽。BN相关肽（GRP、NMB）主要与三种不同的受体（GRP-R、NMB-R）和孤儿受体BRS-3相互作用，以介导胃肠道和中枢神经系统（CNS）中的许多作用。 BRS-3受体受到了相当大的关注，因为BRS-3基因敲除小鼠会出现肥胖、代谢改变和糖尿病。直到最近，还没有选择性激动剂或拮抗剂来评估BRS-3在各种生理/病理生理条件下的重要性。最近，选择性非肽类激动剂MK-5046和拮抗剂Bantag-2均被描述，但关于其药理学的信息有限。我们在具有BRS-3和其他Bn受体的天然细胞和BN-R转染的细胞中进行了详细的研究，将它们的药理学与通用肽激动剂D-Tyr 6，B-Ala 11，Phe 13，Nle 14 Bn（6-14）（肽#1）的药理学进行了比较。我们的研究结果表明，MK-5046和Bantag分别是一种高选择性的激动剂和竞争性拮抗剂，但非肽MK-5046在动力学、亲和力、效力、完全激活所有信号级联的能力和作用持续时间方面与肽激动剂不同。这些差异可能导致生理/病理生理学研究中的重要差异。在最近的一项研究中，我们检查了蛙皮素的合成配体（D-Tyr 6、B-Ala 11、Phe 13、Nle 14 Bn（6-14）（肽#1））作为所有人蛙皮素受体亚型的通用高亲和力激动剂的独特能力的分子基础。在该研究中，使用101种突变受体制备并在CHOP细胞中表达以评估受体亲和力。 鉴定了22个氨基酸有助于这种高亲和力，其中4个特别重要。详细研究了这些中的每一种的化学性质，并研究了有助于高亲和力的每种氨基的特定性质。这些结果现在正在详细的诱变研究中扩展，以确定肽#1对选择性非肽BRS-3激动剂MK-5046和肽拮抗剂Bantag-1的非选择性差异的分子基础。预计差异的定义可能导致设计更具选择性的配体。今年还没有完成的其他研究试图鉴定选择性PACAP/VIP受体配体。H.Coy以及M.Leopoldo教授定义了选择性BN-R非肽配体亲和力的基础，他已经开发了用于Bn受体介导的成像和癌细胞的细胞毒性。

TThe pharmacology and molecular pharmacology of various gastrointestinal (GI) peptides are being investigated. One peptide receptor family was concentrated on during the year: those for bombesin- (Bn) related peptides. Bn-related peptides (GRP, NMB) interact primarily with three distinct receptors (GRP-R, NMB-R) and the orphan receptor, BRS-3 to mediate a number of effects in the GI tract and central nervous system (CNS). The BRS-3 receptor has received considerable attention because BRS-3 knockout mice develop obesity, altered metabolism and diabetes. Until recently there were no selective agonists or antagonist to allow assessment of the importance of BRS-3 in various physiological/pathophysiological conditions. Recently both a selective nonpeptide agonist, MK-5046 and antagonist, Bantag-2 were described however there is limited information on their pharmacology. We performed a detailed study comparing their pharmacology to that of a universal peptide agonist, D-Tyr6, B-Ala11, Phe13, Nle14 Bn (6-14)(peptide #1) in both natural cells possessing BRS-3 and other Bn receptors and BN-R-transfected cells. Our results show that MK-5046 and Bantag are a highly selective agonist, competitive antagonist respectively, however the nonpeptide MK-5046 differs form the peptide agonist in kinetics, affinity, potency, ability to fully activate all signaling cascades and its duration of action. These differences many lead to important differences in physiological/pathophysiological studies. In a recent study we examined the molecular basis for the unique ability of a synthetic ligand of bombesin (D-Tyr6, B-Ala11, Phe13, Nle14 Bn (6-14)(peptide #1)) to function as a universal, high affinity agonist at all human bombesin receptor subtypes. In this study using 101 mutant receptors were made and expressed in CHOP cells to assess receptor affinities. 22 amino acids were identified that contributes to this high affinity of which 4 were especially important. The chemical properties of each of these were investigated in detail and the particular properties of each amino contributing to the high affinity were investigated. These results are now being extending in detailed mutagenesis studies to determine molecular basis for the difference in nonselective of peptide #1 to the selective nonpeptide BRS-3 agonist MK-5046 and the peptide antagonist, Bantag-1. It is anticipated the definition of the difference may lead to design of more selective ligands. Other studies this year not completed yet are attempting to identify selective PACAP/VIP receptor ligands withProf D. H.Coy are as well as with Prof M.Leopoldo to define the basis of affinity of selective BN-R nonpeptide ligands that he has developed for use in Bn receptor mediated imaging and cytotoxicity of cancer cells