Melanocortin-4 Receptor Traffic and Signaling

Melanocortin-4 受体交通和信号传导

基本信息

批准号：
7848231
负责人：
GIULIA BALDINI
金额：
$ 33.89万
依托单位：
UNIV OF ARKANSAS FOR MED SCIS
依托单位国家：
美国
项目类别：
财政年份：
2009
资助国家：
美国
起止时间：
2009-06-01 至 2013-05-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/7848231
关键词：
ART protein Abbreviations Accounting Agonist Area Arrestins Back Binding Biochemical Biological Assay Brain Brain Diseases Cell membrane Cell surface Cellular biology Coupled Data Defect Desire for food Disease Dissociation Eating Embryo Endocytosis Endoplasmic Reticulum Energy Metabolism Epitopes Fluorescence Fluorescence Microscopy G-Protein-Coupled Receptors GRK GTP-Binding Proteins Green Fluorescent Proteins Hemagglutinin Hormones Human Hypothalamic structure Immunoelectron Microscopy Individual Kidney Knowledge Ligands Link Location Melanocortin 4 Receptor Melanocortin 4 receptor mutation Melanocyte stimulating hormone Membrane Molecular Mood Disorders Neuroblastoma Neurons Obesity Parkinson Disease Pathogenesis Pathway interactions Peroxidases Phosphorylation Play Population Positioning Attribute Post-Translational Protein Processing Protein Dephosphorylation Protein Family Proteins Rattus Receptor Cell Receptor Signaling Recycling Residencies Role Route Schizophrenia Signal Transduction Sorting - Cell Movement Testing Ubiquitination Variant alpha-Melanocyte stimulating hormone base desensitization endoplasmic reticulum stress energy balance feeding hepatocyte growth factor-regulated tyrosine kinase substrate human MC4R protein immortalized cell loss of function member new therapeutic target nexin novel obesity prevention palmitoylation paraventricular nucleus prevent protein activation protein folding protein misfolding public health relevance receptor receptor binding receptor function receptor recycling response tetramethylrhodamine trafficking trans-Golgi Network

项目摘要

DESCRIPTION (provided by applicant): Melanocortin-4 receptor (MC4R) is a G-protein-Coupled Receptor (GPCR) expressed in many areas of the brain including the paraventricular nucleus of the hypothalamus. At this location, MC4R expressing neurons receive signals generated by other neurons that release the orexigenic hormone alpha-MSH, which binds and activates MC4R. MC4R mutations account for most of the monogenetic defects that cause obesity, indicating a role in appetite control. Preliminary data from the PI show that MC4R functions as an atypical GPCR because, rather than being endocytosed in response to agonist stimulation, the receptor is constitutively internalized and recycled back to the plasma membrane. In addition it is found that alpha-MSH sequesters MC4R from the plasma membrane by blocking the receptor in an intracellular localization, rather than by increasing its rate of endocytosis. Preliminary results from the PI also indicate that several variants linked to human obesity have defective traffic along the biosynthetic pathway and are retained in the endoplasmic reticulum (ER). The central hypothesis of this proposal is that MC4R cell traffic is essential to modulate receptor activity. In Aim 1, by using a combination of fluorescence-based and biochemical assays, it is determined whether agonist-dependent post-translational modifications of MC4R and binding to specific factors control recycling of the receptor back to the plasma membrane and receptor re-sensitization. Immunoelectron microscopy will be used to determine the intracellular distribution of endogenous MC4R in neurons of the paraventricular nucleus of rat hypothalamus. In Aim 2 the hypothesis is tested that obesity-linked variants that are inefficiently expressed at the plasma membrane are retained in the ER as misfolded proteins, self-associate, and are inefficiently degraded. Possible routes to rescue cell surface expression of such variants will be investigated. It is anticipated that these studies will broaden our understanding of traffic and signaling of MC4R and of obesity- linked variants and will help find new targets for therapies against obesity. PUBLIC HEALTH RELEVANCE: In the last 10 years it has become clear that appetite and energy expenditure are controlled at a central level and that MC4R, a member of the GPCR family of proteins, plays an essential role in these pathways. The mechanisms of MC4R desensitization have not been studied in detail and here we propose to fill this knowledge gap. Defects in the mechanism by which other GPCR are desensitized appear to be important in the pathogenesis of many diseases including Parkinson's disease, mood disorders, and schizophrenia. Pharmacological strategies aimed at targeting the GPCR desensitization machinery including GRK and ¿-arrestin are currently considered to treat brain disorder. On the basis of the mechanism by which MC4R desensitization occurs, similar pharmacological approaches may be considered for the treatment or prevention of obesity. In addition, we propose to understand the molecular mechanism by which specific human MC4R variants cause obesity and to identify novel factors involved in MC4R traffic and signaling. In conclusion, we anticipate that this project will help understand the cell biology of MC4R and that this will be important to find new therapeutic targets to prevent or reverse obesity.

描述（由申请人提供）： Melanocortin-4 受体（MC4R）是一种 G 蛋白偶联受体（GPCR），在大脑的许多区域（包括下丘脑的室旁核）中表达，在该位置，表达 MC4R 的神经元接收产生的信号。由释放促食欲激素 α-MSH 的其他神经元产生，该激素结合并激活 MC4R 突变，是导致大多数单基因缺陷的原因。 PI 的初步数据表明，MC4R 作为非典型 GPCR 发挥作用，因为该受体不是响应激动剂刺激而被内吞，而是组成性内化并再循环回质膜。初步结果发现，α-MSH 通过阻断细胞内定位的受体来将 MC4R 从质膜上隔离，而不是通过增加其内吞作用的速率。 PI 还表明，一些与人类肥胖相关的物质在生物合成途径中存在缺陷，并保留在内质网 (ER) 中。该提议的中心假设是，在目标 1 中，MC4R 细胞运输对于调节受体活性至关重要。使用基于荧光和生化检测的组合，确定 MC4R 的激动剂依赖性翻译后修饰以及与特定因子的结合是否控制受体返回质膜和受体的再循环免疫电子显微镜将用于确定大鼠下丘脑室旁核神经元中内源性 MC4R 的细胞内分布，在目标 2 中，测试了在质膜上低效表达的肥胖相关变体保留在细胞内的假设。我们将研究挽救此类变体的细胞表面表达的可能途径。预计这些研究将扩大我们对 MC4R 和肥胖相关变异的交通和信号传导的理解，并将有助于找到治疗肥胖的新靶点。公共卫生相关性：在过去 10 年中，已经清楚食欲和能量消耗与肥胖相关。 MC4R 是 GPCR 蛋白家族的成员，在这些途径中发挥着重要作用。MC4R 脱敏机制尚未得到详细研究，在此我们建议填补这一知识。其他 GPCR 脱敏机制的缺陷似乎在许多疾病的发病机制中很重要，包括帕金森病、情绪障碍和精神分裂症，旨在针对 GPCR 脱敏机制（包括 GRK 和 ¿）。目前认为α-arrestin可以治疗脑部疾病，根据MC4R脱敏发生的机制，可以考虑使用类似的药理学方法来治疗或预防肥胖。此外，我们建议了解特定人类的分子机制。 MC4R 变异导致肥胖，并鉴定参与 MC4R 运输和信号转导的新因素总之，我们预计该项目将有助于了解 MC4R 的细胞生物学，这对于寻找预防或逆转肥胖的新治疗靶点非常重要。