Small Molecule Probes to Investigate Structure and Function of Y Receptors

描述（由申请人提供）：神经肽Y4受体（Y4）是一种375个氨基酸的g蛋白偶联受体（GPCR），主要在外周组织和脑干中表达。在人类中，Y4属于一个受体家族（Y1、Y2、Y4和Y5），与神经肽Y （NPY）、多肽YY （PYY）和胰多肽（PP）结合。NPY、PYY和PP是36种残肽激素，在调节摄食行为和能量稳态中起重要作用。Y4是唯一对NPY和PYY具有低亲和力，而对PP5具有非常高（小摩尔）亲和力的受体亚型。因此，Y4的选择性激动剂可能是肥胖治疗的有希望的候选者。事实上，Obinepitide （TM-30338）是PP和PYY的一种变体，目前正在进行II期临床试验，用于治疗肥胖。然而，由于obineptide是一种肽，稳定性和生物利用度问题仍然存在。迄今为止，与内源性结合位点结合的非肽类y4选择性配体的开发失败。本研究的目的是鉴定Y4受体的小分子变构调节剂。GPCRs的变构调节剂具有更高的选择性，因为变构结合位点在受体亚型之间的进化保守性较低。变构调节剂的治疗潜力进一步增加，因为它们能够调节受体反应，而不是简单地打开或关闭它。变构增强剂的副作用也可能减少，因为治疗仅在受体与其天然配体结合时起作用。在初步工作中，我们采用了一种Y4功能测定法进行高通量筛选（HTS）实验，可以同时检测激动剂、拮抗剂和变构调节剂。我们对2000种化合物进行了中试筛选，获得了几种候选化合物，其中一种是氯硝柳胺，它在EC50~400 nM范围内显示出强大的、选择性的变构增强作用。提出的实验将与计算方法结合使用，使数百万种化合物的虚拟筛选成为可能。我们将构建定量结构活性关系（QSAR）模型，以建立围绕初始击中化合物的文库和富含预测为Y4变构调节剂的新化学型的文库。Y4小分子变构调节剂的鉴定将允许未来药理学探针的发展，并可以为肥胖药物发现计划奠定基础。

DESCRIPTION (provided by applicant): The neuropeptide Y4 receptor (Y4) is a 375 amino acid G-protein coupled receptor (GPCR) that is ex- pressed mainly in peripheral tissues and the brain stem. In humans, Y4 belongs to a family of receptors (Y1, Y2, Y4, and Y5), that bind the ligands neuropeptide Y (NPY), polypeptide YY (PYY) and pancreatic polypeptide (PP). NPY, PYY and PP are 36 residue peptide hormones that play critical roles in regulating feeding behavior and energy homeostasis. Y4 is the only receptor subtype with low affinity for NPY and PYY and very high (picomolar) affinity for PP5. Thus, selective agonists of Y4 could be promising candidates for obesity therapeutics. In fact Obinepitide (TM-30338), a variant of PP and PYY, is currently in phase II clinical trials as a treatment for obesity. However as Obinepitide is a peptide, issues of stability and bioavailability remain. Development of non-peptidic Y4-selective ligands that bind to the endogenous binding site have failed so far. The objective of the present proposal is to identify small molecule allosteric modulators of the Y4 receptor. Allosteric modulators of GPCRs have a higher chance to be selective as allosteric binding sites tend to be evolutionary less conserved between receptor subtypes. The therapeutic potential of allosteric modulators is further increased by their ability to tune the receptor response instead of simply turning it on or off. Side effects may also be reduced for allosteric potentiators because the therapeutic only acts when the receptor is engaged by its native ligand. In preliminary work, we have adapted a Y4 functional assay for high-throughput screening (HTS) experiments that can detect agonists, antagonists and allosteric modulators simultaneously. We con- ducted a pilot screen of 2,000 compounds that yielded several hits including one, Niclosamide that displayed robust, selective allosteric potentiation with an EC50~400 nM. The proposed experiments will be used in combination with computational methods that enable virtual screening of millions of compounds. We will construct quantitative structure activity relationship (QSAR) models to create libraries focused around initial hit compounds and libraries enriched with novel chemotypes predicted to be Y4 allosteric modulators. Identification of small molecule allosteric modulators of Y4 will allow future development of pharmacological probes and can seed drug discovery programs in obesity.