Melanocortin-4 Receptor Traffic and Signaling

Melanocortin-4 受体交通和信号传导

• 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
• 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

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（由适用提供）：黑色素皮质素-4受体（MC4R）是在大脑许多区域表达的G蛋白偶联受体（GPCR），包括下丘脑的旁牙性核核。在此位置，表达神经元的MC4R会收到其他神经元产生的信号，这些神经元释放了骨质马匹MSH，该神经元绑定并激活MC4R。 MC4R突变解释了导致肥胖症的大多数单基因缺陷，表明在食欲控制中起作用。来自PI的初步数据表明，MC4R起着非典型GPCR的作用，因为，接收器不是响应激动剂刺激的响应内吞作用，而是组成性内部化并回收回到质膜。此外，发现α-MSH隔离从质膜中隔离，通过阻断细胞内定位中的受体，而不是通过增加其内吞作用速率。 PI的初步结果还表明，与人肥胖相关的几种变体沿生物合成途径有缺陷，并保留在内质网中（ER）。该提案的中心假设是MC4R细胞流量对于调节接收器活动至关重要。在AIM 1中，通过使用基于荧光的生化测定的组合，可以确定MC4R的激动剂依赖性的翻译后修饰以及与特定因素的结合是否控制受体回收，将受体回收回到质膜和受体重新启用。免疫电子显微镜将用于确定大鼠下丘脑旁脑室核核心神经元中内源性MC4R的细胞内分布。在AIM 2中，检验了假设，即在质膜上效率低下的肥胖链接变体被保留在ER中，作为错误折叠的蛋白质，自相关，并且无效降解。将研究挽救此类变体的细胞表面表达的可能路线。预计这些研究将扩大我们对MC4R和肥胖相关变体的交通和信号的理解，并将帮助找到针对肥胖症的疗法的新靶标。公共卫生相关性：在过去的十年中，很明显，食欲和能源消耗是在中央一级控制的，而GPCR蛋白质家族的成员MC4R在这些途径中起着至关重要的作用。 MC4R脱敏的机制尚未详细研究，我们在这里建议填补这一知识差距。其他GPCR脱敏外观的缺陷在许多疾病的发病机理中很重要，包括帕金森氏病，情绪障碍和精神分裂症。目前认为旨在以GPCR脱敏机制为目标的药理策略目前被认为是治疗脑部疾病的药理策略。基于MC4R脱敏的机制，可以考虑使用类似的药物方法来治疗或预防肥胖症。此外，我们建议了解特定人类MC4R变体引起肥胖并确定与MC4R流量和信号传导有关的新因素的分子机制。总而言之，我们预计该项目将有助于了解MC4R的细胞生物学，这对于寻找新的治疗靶点以预防或逆转肥胖非常重要。