Identification of a novel bioactive peptide

描述（由申请人提供）：G蛋白偶联受体（gpcr）是人类基因组中最大的基因家族，积累了治疗药物最成功的生化靶点。大约140种gpcr的天然配体是未知的，因此它们被称为“孤儿”受体。这些天然配体的鉴定是开始研究其功能的关键一步，并具有开发新型药物的潜力。我们已经开发了一种分离这种天然配体的策略，通过在合适的细胞系中表达克隆的受体，并在加入组织提取物的部分后监测受体的激活。这种新颖的策略最终将使我们能够纯化活性分子并确定其结构。在这个应用中，我们建议应用这种高度创新的技术来分离、鉴定和表征孤儿受体bombesin亚型-3 （BRS-3）的天然配体，这仍然是难以捉摸的。缺乏BRS-3受体的小鼠会出现贪食、低代谢和肥胖表型，预计BRS-3受体在整合和调节摄食背后的复杂生理过程中发挥重要作用。该受体不结合两种已知的哺乳动物糖蛋白对应物，即青蛙肽神经素B和胃泌素释放肽，它们与其他两种糖蛋白受体亚型（BB-1和2）结合。在分离天然配体后，我们将对其药理作用进行表征，并对其进行研究。随后，我们建议在行为喂养实验中对BRS-3配体进行研究，以确定其作用模式。BRS-3配体将成为解答BRS-3系统在能量平衡调节中的功能意义和生理作用的宝贵工具。

DESCRIPTION (provided by applicant): G protein-coupled receptors (GPCRs) constitute the largest gene family in the human genome and accumulate the most successful biochemical targets for therapeutic drugs. The natural ligands of about 140 GPCRs are unknown and they are thus called "orphan" receptors. Identification of these natural ligands forms the crucial step to start studying their function and holds the potential for development of novel pharmaceutical drugs. We have developed a strategy to isolate such natural ligands by expressing the cloned receptors in suitable cell lines and monitoring activation of the receptors after adding fractions of tissue extracts. This novel strategy will ultimately allow us to purify the active molecules and determine their structure. In this application, we propose to apply this highly innovative technique to isolate, identify and characterize the natural ligand of the orphan receptor bombesin subtype-3 (BRS-3) that is still elusive. BRS-3 receptor is expected to play an important role in integrating and modulating the complex physiology underlying feeding as evidenced by the fact that mice devoid of BRS-3 receptor are hyperphagic, hypometabolic and develop an obese phenotype. This receptor does not bind the two known mammalian bombesin counterparts of the frog peptide neuromedin B and gastrin-releasing peptide that bind to the other two bombesin receptor subtypes (BB-1 and 2). Following the isolation of the natural ligand, we will characterize the pharmacological effects, study the Subsequently, we propose to study the BRS-3 ligand in a behavioral feeding assay in order to determine its mode of action. The BRS-3 ligands will prove as an invaluable tool to answer the functional significance and understand the physiological role of the BRS-3 system in the regulation of energy balance.