Allosteric Modulators of the Melanocortin-4 Receptor

描述（由申请人提供）：中枢神经系统的黑素皮质素回路是脂肪的关键组成部分。这些回路的激活抑制了食物摄入，刺激了能量消耗，因此黑素皮素-4受体一直是主要制药公司开发治疗普通肥胖药物的目标。两项强效MC4-R激动剂的临床试验在一些个体中显示出不必要的升压活性。最近，gpcr的变构调节剂被认为是一种恢复生理系统正常时空活动的方法，而没有强效正构激动剂的毒性。MC4R的这种变构调节剂可能既适用于严重综合征型肥胖，也适用于普通肥胖。在高达5%的病例中，由黑素皮素信号缺陷引起的严重早发性肥胖与导致MC4R单倍功能不足的非同义编码突变有关。假设MC4R启动子突变，以及该通路中其他基因的突变最终可能被发现，预计10-30%的严重儿童肥胖可能是由黑素皮皮质素信号缺陷引起的。大多数MC4R突变破坏受体到细胞表面的运输，而不是对配体的亲和力。与过度刺激MC4R可能导致不良副作用的普通肥胖不同，黑素皮质素受体单倍功能不全导致的严重肥胖的成功治疗可能需要将MC4R蛋白水平提高到生理水平，从而潜在地避免副作用。事实上，在MC4R单倍体不足的肥胖患者中已证实存在相对低血压。在本应用中，我们建议鉴定MC4R的变构调制剂，从使用Vanderbilt高通量筛选核心的162,000种化合物的高通量筛选开始。初始命中将被验证，并且子集将在细胞培养模型中广泛表征。然后将使用Vanderbilt合成化学核心进行化合物优化，以开发临床前先导化合物。我们还建议利用我们在这里提出的两种检测方法，MC4R功能的电生理切片制备和MC4R单倍功能不全的小鼠模型，并表征针对MC4R的抗体，以充分表征筛选中发现的变构调节剂的作用机制。最后，我们将尝试鉴定黑素皮质素信号的血清生物标志物，作为分析黑素皮质素信号的变构调节剂的微创工具。

DESCRIPTION (provided by applicant): The melanocortin circuitry of the CNS is a critical component of the adipostat. Activation of these circuits inhibits food intake and stimulates energy expenditure and thus the melanocortin-4 receptor has been a target of the major pharmaceutical companies for the development of drugs for the treatment of common obesity. Two clinical trials of potent MC4-R agonists exhibited unwanted pressor activity in some individuals. Recently, allosteric modulators of GPCRs have been recognized as a method of restoring normal spatio-temporal activity of physiological systems without the toxicity resulting from potent orthosteric agonists. Such allosteric modulators of the MC4R might have application to both severe syndromic obesity, as well as common obesity. Severe early onset obesity due to defective melanocortin signaling is linked, in up to 5% of cases, with non- synonymous coding mutations causing haploinsufficiency of the MC4R. It would not be unusual to expect that 10-30% of severe childhood obesity may thus result from defective melanocortin signaling, assuming MC4R promoter mutations, and mutations in other genes in the pathway may ultimately be discovered. The majority of MC4R mutations disrupt trafficking of receptors to the cell surface, rather than affinity for ligand. In contrast to common obesity, where excessive MC4R stimulation may cause unwanted side effects, successful treatment of severe obesity due to melanocortin receptor haploinsufficiency may involve increasing MC4R protein levels to physiological levels, thus potentially avoiding side effcets. Indeed, relative hypotension has been demonstrated in MC4R haploinsufficient obese patients. In this application, we propose to identify allosteric modulators of the MC4R, beginning with a high throughput screen of 162,000 compounds with the Vanderbilt High Throughput Screening Core. Initial hits will be validated, and a subset will be extensively characterized in cell culture models. Compound optimization will then be performed with the Vanderbilt Synthetic Chemistry Core, to develop preclinical lead compounds. We also propose to utilize two assays we present here, an electrophysiological slice preparation for MC4R function and a mouse model of MC4R haploinsufficiency, and to characterize antibodies against the MC4R to fully characterize the mechanism of action of allosteric modulators identified in the screen. Finally, we will attempt to identify serum biomarkers for melanocortin signaling as a less invasive tool for analysis of allosteric modulators of melanocortin signaling.