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Wei R, Li D, Jia S, Chen Y, Wang J. MC4R in Central and Peripheral Systems. Adv Biol (Weinh) 2023; 7:e2300035. [PMID: 37043700 DOI: 10.1002/adbi.202300035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2023] [Revised: 02/25/2023] [Indexed: 04/14/2023]
Abstract
Obesity has emerged as a critical and urgent health burden during the current global pandemic. Among multiple genetic causes, melanocortin receptor-4 (MC4R), involved in food intake and energy metabolism regulation through various signaling pathways, has been reported to be the lead genetic factor in severe and early onset obesity and hyperphagia disorders. Most previous studies have illustrated the roles of MC4R signaling in energy intake versus expenditure in the central system, while some evidence indicates that MC4R is also expressed in peripheral systems, such as the gut and endocrine organs. However, its physiopathological function remains poorly defined. This review aims to depict the central and peripheral roles of MC4R in energy metabolism and endocrine hormone homeostasis, the diversity of phenotypes, biased downstream signaling caused by distinct MC4R mutations, and current drug development targeting the receptor.
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Affiliation(s)
- Ran Wei
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Road, Shanghai, 200025, China
- Shanghai National Clinical Research Center for Metabolic Diseases, Key Laboratory for Endocrine and Metabolic Diseases of the National Health Commission of the PR China, Shanghai National Center for Translational Medicine, Shanghai, 200025, China
- Department of Endocrinology, Shanghai Fifth People's Hospital, Fudan University, Shanghai, 200240, China
| | - Danjie Li
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Road, Shanghai, 200025, China
- Shanghai National Clinical Research Center for Metabolic Diseases, Key Laboratory for Endocrine and Metabolic Diseases of the National Health Commission of the PR China, Shanghai National Center for Translational Medicine, Shanghai, 200025, China
| | - Sheng Jia
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Road, Shanghai, 200025, China
- Shanghai National Clinical Research Center for Metabolic Diseases, Key Laboratory for Endocrine and Metabolic Diseases of the National Health Commission of the PR China, Shanghai National Center for Translational Medicine, Shanghai, 200025, China
| | - Yuhong Chen
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Road, Shanghai, 200025, China
- Shanghai National Clinical Research Center for Metabolic Diseases, Key Laboratory for Endocrine and Metabolic Diseases of the National Health Commission of the PR China, Shanghai National Center for Translational Medicine, Shanghai, 200025, China
| | - Jiqiu Wang
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Road, Shanghai, 200025, China
- Shanghai National Clinical Research Center for Metabolic Diseases, Key Laboratory for Endocrine and Metabolic Diseases of the National Health Commission of the PR China, Shanghai National Center for Translational Medicine, Shanghai, 200025, China
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Ji RL, Liu T, Hou ZS, Wen HS, Tao YX. Divergent Pharmacology and Biased Signaling of the Four Melanocortin-4 Receptor Isoforms in Rainbow Trout ( Oncorhynchus mykiss). Biomolecules 2023; 13:1248. [PMID: 37627313 PMCID: PMC10452266 DOI: 10.3390/biom13081248] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 08/13/2023] [Accepted: 08/14/2023] [Indexed: 08/27/2023] Open
Abstract
The melanocortin-4 receptor (MC4R) is essential for the modulation of energy balance and reproduction in both fish and mammals. Rainbow trout (Oncorhynchus mykiss) has been extensively studied in various fields and provides a unique opportunity to investigate divergent physiological roles of paralogues. Herein we identified four trout mc4r (mc4ra1, mc4ra2, mc4rb1, and mc4rb2) genes. Four trout Mc4rs (omMc4rs) were homologous to those of teleost and mammalian MC4Rs. Multiple sequence alignments, a phylogenetic tree, chromosomal synteny analyses, and pharmacological studies showed that trout mc4r genes may have undergone different evolutionary processes. All four trout Mc4rs bound to two peptide agonists and elevated intracellular cAMP levels dose-dependently. High basal cAMP levels were observed at two omMc4rs, which were decreased by Agouti-related peptide. Only omMc4rb2 was constitutively active in the ERK1/2 signaling pathway. Ipsen 5i, ML00253764, and MCL0020 were biased allosteric modulators of omMc4rb1 with selective activation upon ERK1/2 signaling. ML00253764 behaved as an allosteric agonist in Gs-cAMP signaling of omMc4rb2. This study will lay the foundation for future physiological studies of various mc4r paralogs and reveal the evolution of MC4R in vertebrates.
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Affiliation(s)
- Ren-Lei Ji
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA; (R.-L.J.); (T.L.)
| | - Ting Liu
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA; (R.-L.J.); (T.L.)
| | - Zhi-Shuai Hou
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA; (R.-L.J.); (T.L.)
| | - Hai-Shen Wen
- The Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao 266100, China;
| | - Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA; (R.-L.J.); (T.L.)
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3
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Yuan XC, Tao YX. Ligands for Melanocortin Receptors: Beyond Melanocyte-Stimulating Hormones and Adrenocorticotropin. Biomolecules 2022; 12:biom12101407. [PMID: 36291616 PMCID: PMC9599618 DOI: 10.3390/biom12101407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 09/25/2022] [Accepted: 09/28/2022] [Indexed: 11/16/2022] Open
Abstract
The discovery of melanocortins in 1916 has resulted in more than 100 years of research focused on these peptides. Extensive studies have elucidated well-established functions of melanocortins mediated by cell surface receptors, including MSHR (melanocyte-stimulating hormone receptor) and ACTHR (adrenocorticotropin receptor). Subsequently, three additional melanocortin receptors (MCRs) were identified. Among these five MCRs, MC3R and MC4R are expressed primarily in the central nervous system, and are therefore referred to as the neural MCRs. Since the central melanocortin system plays important roles in regulating energy homeostasis, targeting neural MCRs is emerging as a therapeutic approach for treating metabolic conditions such as obesity and cachexia. Early efforts modifying endogenous ligands resulted in the development of many potent and selective ligands. This review focuses on the ligands for neural MCRs, including classical ligands (MSH and agouti-related peptide), nonclassical ligands (lipocalin 2, β-defensin, small molecules, and pharmacoperones), and clinically approved ligands (ACTH, setmelanotide, bremelanotide, and several repurposed drugs).
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Affiliation(s)
- Xiao-Chen Yuan
- College of Animal Science and Technology, Anhui Agricultural University, Hefei 230061, China
| | - Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA
- Correspondence:
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4
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Laiho L, Murray JF. The Multifaceted Melanocortin Receptors. Endocrinology 2022; 163:6608375. [PMID: 35700124 PMCID: PMC9214563 DOI: 10.1210/endocr/bqac083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Indexed: 12/05/2022]
Abstract
The 5 known melanocortin receptors (MCs) have established physiological roles. With the exception of MC2, these receptors can behave unpredictably, and since they are more widely expressed than their established roles would suggest, it is likely that they have other poorly characterized functions. The aim of this review is to discuss some of the less well-explored aspects of the 4 enigmatic members of this receptor family (MC1,3-5) and describe how these are multifaceted G protein-coupled receptors (GPCRs). These receptors appear to be promiscuous in that they bind several endogenous agonists (products of the proopiomelanocortin [POMC] gene) and antagonists but with inconsistent relative affinities and effects. We propose that this is a result of posttranslational modifications that determine receptor localization within nanodomains. Within each nanodomain there will be a variety of proteins, including ion channels, modifying proteins, and other GPCRs, that can interact with the MCs to alter the availability of receptor at the cell surface as well as the intracellular signaling resulting from receptor activation. Different combinations of interacting proteins and MCs may therefore give rise to the complex and inconsistent functional profiles reported for the MCs. For further progress in understanding this family, improved characterization of tissue-specific functions is required. Current evidence for interactions of these receptors with a range of partners, resulting in modulation of cell signaling, suggests that each should be studied within the full context of their interacting partners. The role of physiological status in determining this context also remains to be characterized.
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Affiliation(s)
- Linda Laiho
- Centre for Discovery Brain Sciences, School of Biomedical Sciences, University of Edinburgh, Edinburgh, UK
| | - Joanne Fiona Murray
- Correspondence: J. F. Murray, PhD, Centre for Discovery Brain Sciences, School of Biomedical Sciences, University of Edinburgh, Hugh Robson Building, 15 George Square, Edinburgh EH8 9DX, UK.
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5
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Tao YX. Mutations in melanocortin-4 receptor: From fish to men. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2022; 189:215-257. [PMID: 35595350 DOI: 10.1016/bs.pmbts.2022.03.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Melanocortin-4 receptor (MC4R), expressed abundantly in the hypothalamus, is a critical regulator of energy homeostasis, including both food intake and energy expenditure. Shortly after the publication in 1997 of the Mc4r knockout phenotypes in mice, including increased food intake and severe obesity, the first mutations in MC4R were reported in humans in 1998. Studies in the subsequent two decades have established MC4R mutation as the most common monogenic form of obesity, especially in early-onset severe obesity. Studies in animals, from fish to mammals, have established the conserved physiological roles of MC4R in all vertebrates in regulating energy balance. Drug targeting MC4R has been recently approved for treating morbid genetic obesity. How the MC4R can be exploited for animal production is highly worthy of active investigation.
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Affiliation(s)
- Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL, United States.
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6
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Fatima MT, Ahmed I, Fakhro KA, Akil ASA. Melanocortin-4 receptor complexity in energy homeostasis,obesity and drug development strategies. Diabetes Obes Metab 2022; 24:583-598. [PMID: 34882941 PMCID: PMC9302617 DOI: 10.1111/dom.14618] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Revised: 12/05/2021] [Accepted: 12/06/2021] [Indexed: 12/19/2022]
Abstract
The melanocortin-4 receptor (MC4R) has been critically investigated for the past two decades, and novel findings regarding MC4R signalling and its potential exploitation in weight loss therapy have lately been emphasized. An association between MC4R and obesity is well established, with disease-causing mutations affecting 1% to 6% of obese patients. More than 200 MC4R variants have been reported, although conflicting results as to their effects have been found in different cohorts. Most notably, some MC4R gain-of-function variants seem to rescue obesity and related complications via specific pathways such as beta-arrestin (ß-arrestin) recruitment. Broadly speaking, however, dysfunctional MC4R dysregulates satiety and induces hyperphagia. The picture at the mechanistic level is complicated as, in addition to the canonical G stimulatory pathway, the ß-arrestin signalling pathway and ions (particularly calcium) seem to interact with MC4R signalling to contribute to or alleviate obesity pathogenesis. Thus, the overall complexity of the MC4R signalling spectra has broadened considerably, indicating there is great potential for the development of new drugs to manage obesity and its related complications. Alpha-melanocyte-stimulating hormone is the major endogenous MC4R agonist, but structure-based ligand discovery studies have identified possible superior and selective agonists that can improve MC4R function. However, some of these agonists characterized in vitro and in vivo confer adverse effects in patients, as demonstrated in clinical trials. In this review, we provide a comprehensive insight into the genetics, function and regulation of MC4R and its contribution to obesity. We also outline new approaches in drug development and emerging drug candidates to treat obesity.
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Affiliation(s)
- Munazza Tamkeen Fatima
- Department of Human Genetics, Translational Medicine DivisionResearch Branch, Sidra MedicineDohaQatar
| | - Ikhlak Ahmed
- Department of Human Genetics, Translational Medicine DivisionResearch Branch, Sidra MedicineDohaQatar
| | - Khalid Adnan Fakhro
- Department of Human Genetics, Translational Medicine DivisionResearch Branch, Sidra MedicineDohaQatar
- Department of Genetic MedicineWeill Cornell MedicineDohaQatar
- College of Health and Life SciencesHamad Bin Khalifa UniversityDohaQatar
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7
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Liu T, Ji RL, Tao YX. Naturally occurring mutations in G protein-coupled receptors associated with obesity and type 2 diabetes mellitus. Pharmacol Ther 2021; 234:108044. [PMID: 34822948 DOI: 10.1016/j.pharmthera.2021.108044] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 11/15/2021] [Accepted: 11/15/2021] [Indexed: 12/12/2022]
Abstract
G protein-coupled receptors (GPCRs) are the largest family of membrane receptors involved in the regulation of almost all known physiological processes. Dysfunctions of GPCR-mediated signaling have been shown to cause various diseases. The prevalence of obesity and type 2 diabetes mellitus (T2DM), two strongly associated disorders, is increasing worldwide, with tremendous economical and health burden. New safer and more efficacious drugs are required for successful weight reduction and T2DM treatment. Multiple GPCRs are involved in the regulation of energy and glucose homeostasis. Mutations in these GPCRs contribute to the development and progression of obesity and T2DM. Therefore, these receptors can be therapeutic targets for obesity and T2DM. Indeed some of these receptors, such as melanocortin-4 receptor and glucagon-like peptide 1 receptor, have provided important new drugs for treating obesity and T2DM. This review will focus on the naturally occurring mutations of several GPCRs associated with obesity and T2DM, especially incorporating recent large genomic data and insights from structure-function studies, providing leads for future investigations.
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Affiliation(s)
- Ting Liu
- Department of Anatomy, Physiology and Pharmacology, Auburn University College of Veterinary Medicine, Auburn, AL 36849, United States
| | - Ren-Lei Ji
- Department of Anatomy, Physiology and Pharmacology, Auburn University College of Veterinary Medicine, Auburn, AL 36849, United States
| | - Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, Auburn University College of Veterinary Medicine, Auburn, AL 36849, United States.
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8
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Doering SR, Freeman K, Debevec G, Geer P, Santos RG, Lavoi TM, Giulianotti MA, Pinilla C, Appel JR, Houghten RA, Ericson MD, Haskell-Luevano C. Discovery of Nanomolar Melanocortin-3 Receptor (MC3R)-Selective Small Molecule Pyrrolidine Bis-Cyclic Guanidine Agonist Compounds Via a High-Throughput "Unbiased" Screening Campaign. J Med Chem 2021; 64:5577-5592. [PMID: 33886285 PMCID: PMC8552302 DOI: 10.1021/acs.jmedchem.0c02041] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The central melanocortin-3 and melanocortin-4 receptors (MC3R, MC4R) are key regulators of body weight and energy homeostasis. Herein, the discovery and characterization of first-in-class small molecule melanocortin agonists with selectivity for the melanocortin-3 receptor over the melanocortin-4 receptor are reported. Identified via "unbiased" mixture-based high-throughput screening approaches, pharmacological evaluation of these pyrrolidine bis-cyclic guanidines resulted in nanomolar agonist activity at the melanocortin-3 receptor. The pharmacological profiles at the remaining melanocortin receptor subtypes tested indicated similar agonist potencies at both the melanocortin-1 and melanocortin-5 receptors and antagonist or micromolar agonist activities at the melanocortin-4 receptor. This group of small molecules represents a new area of chemical space for the melanocortin receptors with mixed receptor pharmacology profiles that may serve as novel lead compounds to modulate states of dysregulated energy balance.
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Affiliation(s)
- Skye R Doering
- Department of Medicinal Chemistry and Institute for Translational Neuroscience, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Katie Freeman
- Department of Medicinal Chemistry and Institute for Translational Neuroscience, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Ginamarie Debevec
- Florida International University, Port St. Lucie, Florida 34987, United States
| | - Phaedra Geer
- Florida International University, Port St. Lucie, Florida 34987, United States
| | - Radleigh G Santos
- Nova Southeastern University, 3301 College Avenue, Fort Lauderdale, Florida 33314, United States
| | - Travis M Lavoi
- Florida International University, Port St. Lucie, Florida 34987, United States
| | - Marc A Giulianotti
- Florida International University, Port St. Lucie, Florida 34987, United States
| | - Clemencia Pinilla
- Florida International University, Port St. Lucie, Florida 34987, United States
| | - Jon R Appel
- Florida International University, Port St. Lucie, Florida 34987, United States
| | - Richard A Houghten
- Florida International University, Port St. Lucie, Florida 34987, United States
| | - Mark D Ericson
- Department of Medicinal Chemistry and Institute for Translational Neuroscience, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Carrie Haskell-Luevano
- Department of Medicinal Chemistry and Institute for Translational Neuroscience, University of Minnesota, Minneapolis, Minnesota 55455, United States
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9
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Yeo GSH, Chao DHM, Siegert AM, Koerperich ZM, Ericson MD, Simonds SE, Larson CM, Luquet S, Clarke I, Sharma S, Clément K, Cowley MA, Haskell-Luevano C, Van Der Ploeg L, Adan RAH. The melanocortin pathway and energy homeostasis: From discovery to obesity therapy. Mol Metab 2021; 48:101206. [PMID: 33684608 PMCID: PMC8050006 DOI: 10.1016/j.molmet.2021.101206] [Citation(s) in RCA: 98] [Impact Index Per Article: 32.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Revised: 02/28/2021] [Accepted: 03/03/2021] [Indexed: 02/08/2023] Open
Abstract
Background Over the past 20 years, insights from human and mouse genetics have illuminated the central role of the brain leptin-melanocortin pathway in controlling mammalian food intake, with genetic disruption resulting in extreme obesity, and more subtle polymorphic variations influencing the population distribution of body weight. At the end of 2020, the U.S. Food and Drug Administration (FDA) approved setmelanotide, a melanocortin 4 receptor agonist, for use in individuals with severe obesity due to either pro-opiomelanocortin (POMC), proprotein convertase subtilisin/kexin type 1 (PCSK1), or leptin receptor (LEPR) deficiency. Scope of review Herein, we chart the melanocortin pathway's history, explore its pharmacology, genetics, and physiology, and describe how a neuropeptidergic circuit became an important druggable obesity target. Major conclusions Unravelling the genetics of the subset of severe obesity has revealed the importance of the melanocortin pathway in appetitive control; coupling this with studying the molecular pharmacology of compounds that bind melanocortin receptors has brought a new obesity drug to the market. This process provides a drug discovery template for complex disorders, which for setmelanotide took 25 years to transform from a single gene into an approved drug.
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Affiliation(s)
- Giles S H Yeo
- MRC Metabolic Diseases Unit, University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge, UK.
| | | | - Anna-Maria Siegert
- MRC Metabolic Diseases Unit, University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge, UK.
| | - Zoe M Koerperich
- Department of Medicinal Chemistry and Institute for Translational Neuroscience, University of Minnesota, Minneapolis, MN, USA 55455.
| | - Mark D Ericson
- Department of Medicinal Chemistry and Institute for Translational Neuroscience, University of Minnesota, Minneapolis, MN, USA 55455.
| | - Stephanie E Simonds
- Metabolism, Diabetes, and Obesity Programme, Monash Biomedicine Discovery Institute, and Department of Physiology, Monash University, Clayton, Victoria, Australia.
| | - Courtney M Larson
- Department of Medicinal Chemistry and Institute for Translational Neuroscience, University of Minnesota, Minneapolis, MN, USA 55455.
| | - Serge Luquet
- Université de Paris, BFA, UMR 8251, CNRS, Paris, France.
| | - Iain Clarke
- Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Parkville, VIC 3010, Australia.
| | | | - Karine Clément
- Assistance Publique Hôpitaux de Paris, Nutrition Department, Pitié-Salpêtrière Hospital, Paris, France, Sorbonne Université, INSERM, Nutrition and Obesity: Systemic Approaches (NutriOmics) Research Unit, Paris, France.
| | - Michael A Cowley
- Metabolism, Diabetes, and Obesity Programme, Monash Biomedicine Discovery Institute, and Department of Physiology, Monash University, Clayton, Victoria, Australia.
| | - Carrie Haskell-Luevano
- Department of Medicinal Chemistry and Institute for Translational Neuroscience, University of Minnesota, Minneapolis, MN, USA 55455.
| | | | - Roger A H Adan
- Department of Translational Neuroscience, UMCU Brain Centre, University Medical Centre Utrecht, Utrecht University, the Netherlands; Institute of Neuroscience and Physiology, Sahlgrenska Academy at the University of Gothenburg, Sweden.
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10
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Zhang HJ, Cui ZH, Liu M, Min TQ, Xiao X, Wang ZQ, Tao YX. Pharmacological characterization of three chicken melanocortin-3 receptor mutants. Domest Anim Endocrinol 2021; 74:106507. [PMID: 32841887 DOI: 10.1016/j.domaniend.2020.106507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Revised: 06/01/2020] [Accepted: 06/01/2020] [Indexed: 10/24/2022]
Abstract
The melanocortin-3 receptor (MC3R) is a G protein-coupled receptor and potentially important in production traits. Three naturally occurring mutations (M54L, G104S, and L151R) in chicken MC3R (cMC3R) were reported previously to be associated with production traits. Here, we inserted the full-length cMC3R coding sequence into pcDNA3.1(+) and generated the 3 mutations by site-directed mutagenesis. The total and cell surface expression of the receptors was measured by flow cytometry. We analyzed the pharmacological characteristics, including binding and cyclic adenosine monophosphate (cAMP) and mitogen-activated protein kinase (MAPK) signaling, using 6 ligands ([Nle4, D-Phe7]-α-melanocyte stimulating hormone (MSH), α-, β-, γ-, and D-Trp8-γ-MSHs, and agouti-related peptide). All mutants had similar total and cell surface expression as the wild-type (WT) cMC3R. M54L had similar pharmacological properties as the WT cMC3R. G104S did not exhibit any specific binding but had minimal response to α-, β-, γ-, and D-Trp8-γ-MSH, although it generated 24% WT response when stimulated by NDP-MSH. Although L151R had normal binding, the responses to agonists were reduced to approximately 25% of that of the WT. In MAPK signaling, all 3 mutants showed significantly increased agonist-stimulated phosphorylation of extracellular signal-regulated protein kinases 1/2, indicating the existence of biased signaling at G104S and L151R. In summary, our studies demonstrated that although all 3 mutations are significantly associated with production traits, only G104S and L151R had severe defects in receptor pharmacology. How M54L might cause production trait differences remains to be investigated.
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Affiliation(s)
- H-J Zhang
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu 225009, People's Republic of China; Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA
| | - Z-H Cui
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu 225009, People's Republic of China
| | - M Liu
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu 225009, People's Republic of China
| | - T-Q Min
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu 225009, People's Republic of China
| | - X Xiao
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu 225009, People's Republic of China
| | - Z-Q Wang
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu 225009, People's Republic of China.
| | - Y-X Tao
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA.
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11
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Yang LK, Hou ZS, Tao YX. Biased signaling in naturally occurring mutations of G protein-coupled receptors associated with diverse human diseases. Biochim Biophys Acta Mol Basis Dis 2021; 1867:165973. [PMID: 32949766 PMCID: PMC7722056 DOI: 10.1016/j.bbadis.2020.165973] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 09/07/2020] [Accepted: 09/14/2020] [Indexed: 12/15/2022]
Abstract
G protein-coupled receptors (GPCRs) play critical roles in transmitting a variety of extracellular signals into the cells and regulate diverse physiological functions. Naturally occurring mutations that result in dysfunctions of GPCRs have been known as the causes of numerous diseases. Significant progresses have been made in elucidating the pathophysiology of diseases caused by mutations. The multiple intracellular signaling pathways, such as G protein-dependent and β-arrestin-dependent signaling, in conjunction with recent advances on biased agonism, have broadened the view on the molecular mechanism of disease pathogenesis. This review aims to briefly discuss biased agonism of GPCRs (biased ligands and biased receptors), summarize the naturally occurring GPCR mutations that cause biased signaling, and propose the potential pathophysiological relevance of biased mutant GPCRs associated with various endocrine diseases.
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Affiliation(s)
- Li-Kun Yang
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, United States
| | - Zhi-Shuai Hou
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, United States
| | - Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, United States.
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12
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Yang LK, Tao YX. Alanine Scanning Mutagenesis of the DRYxxI Motif and Intracellular Loop 2 of Human Melanocortin-4 Receptor. Int J Mol Sci 2020; 21:ijms21207611. [PMID: 33076233 PMCID: PMC7589821 DOI: 10.3390/ijms21207611] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 10/10/2020] [Accepted: 10/11/2020] [Indexed: 12/15/2022] Open
Abstract
The melanocortin-4 receptor (MC4R) is a member of the G-protein-coupled receptor (GPCR) superfamily, which has been extensively studied in obesity pathogenesis due to its critical role in regulating energy homeostasis. Both the Gs-cAMP and ERK1/2 cascades are known as important intracellular signaling pathways initiated by the MC4R. The DRYxxI motif at the end of transmembrane domain 3 and the intracellular loop 2 (ICL2) are thought to be crucial for receptor function in several GPCRs. To study the functions of this domain in MC4R, we performed alanine-scanning mutagenesis on seventeen residues. We showed that one residue was critical for receptor cell surface expression. Eight residues were important for ligand binding. Mutations of three residues impaired Gs-cAMP signaling without changing the binding properties. Investigation on constitutive activities of all the mutants in the cAMP pathway revealed that six residues were involved in constraining the receptor in inactive states and five residues were important for receptor activation in the absence of an agonist. In addition, mutations of four residues impaired the ligand-stimulated ERK1/2 signaling pathway without affecting the binding properties. We also showed that some mutants were biased to the Gs-cAMP or ERK1/2 signaling pathway. In summary, we demonstrated that the DRYxxI motif and ICL2 were important for MC4R function.
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Yang Z, Liang XF, Li GL, Tao YX. Biased signaling in fish melanocortin-4 receptors (MC4Rs): Divergent pharmacology of four ligands on spotted scat (Scatophagus argus) and grass carp (Ctenopharyngodon idella) MC4Rs. Mol Cell Endocrinol 2020; 515:110929. [PMID: 32615281 DOI: 10.1016/j.mce.2020.110929] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 06/19/2020] [Accepted: 06/24/2020] [Indexed: 12/24/2022]
Abstract
The melanocortin-4 receptor (MC4R) plays a critical role in the regulation of energy homeostasis in both mammals and fish. Several fish MC4Rs recently characterized have high constitutive activities, potentially associated with food intake and growth rate. In the present study, we systematically investigated the effects of four human MC4R (hMC4R) antagonists, including agouti-related peptide (AgRP), Ipsen 5i, ML00253764, and MCL0020, on the cAMP and ERK1/2 signaling of two fish MC4Rs: spotted scat (Scatophagus argus) MC4R (saMC4R) and grass carp (Ctenopharyngodon idella) MC4R (ciMC4R), with hMC4R as a control. We showed that both saMC4R and ciMC4R were constitutively active with significantly increased basal cAMP levels. AgRP acted as an inverse agonist in cAMP signaling pathway in both fish MC4Rs whereas MCL0020 functioned as an inverse agonist for ciMC4R but a weak neutral antagonist for saMC4R. Ipsen 5i and MCL0020 behaved as neutral allosteric modulators in the cAMP signaling of fish MC4Rs. The saMC4R and ciMC4R had similar basal pERK1/2 levels as hMC4R and the pERK1/2 levels of the two fish MC4Rs were significantly increased upon stimulation with all four ligands. In summary, our studies demonstrated the existence of biased signaling in fish MC4R. We also showed dramatic pharmacological differences of human and fish MC4Rs with synthetic ligands. Our data provided novel insights and led to a better understanding of fish MC4R pharmacology.
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Affiliation(s)
- Zhao Yang
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL, 36849, United States
| | - Xu-Fang Liang
- College of Fisheries, Key Lab of Freshwater Animal Breeding, Ministry of Agriculture, Huazhong Agricultural University, Hubei Collaborative Innovation Center for Freshwater Aquaculture, Wuhan, Hubei, 430070, China
| | - Guang-Li Li
- Fisheries College, Guangdong Ocean University, Zhanjiang, 524088, China
| | - Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL, 36849, United States.
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Structural Complexity and Plasticity of Signaling Regulation at the Melanocortin-4 Receptor. Int J Mol Sci 2020; 21:ijms21165728. [PMID: 32785054 PMCID: PMC7460885 DOI: 10.3390/ijms21165728] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2020] [Revised: 08/03/2020] [Accepted: 08/06/2020] [Indexed: 02/06/2023] Open
Abstract
The melanocortin-4 receptor (MC4R) is a class A G protein-coupled receptor (GPCR), essential for regulation of appetite and metabolism. Pathogenic inactivating MC4R mutations are the most frequent cause of monogenic obesity, a growing medical and socioeconomic problem worldwide. The MC4R mediates either ligand-independent or ligand-dependent signaling. Agonists such as α-melanocyte-stimulating hormone (α-MSH) induce anorexigenic effects, in contrast to the endogenous inverse agonist agouti-related peptide (AgRP), which causes orexigenic effects by suppressing high basal signaling activity. Agonist action triggers the binding of different subtypes of G proteins and arrestins, leading to concomitant induction of diverse intracellular signaling cascades. An increasing number of experimental studies have unraveled molecular properties and mechanisms of MC4R signal transduction related to physiological and pathophysiological aspects. In addition, the MC4R crystal structure was recently determined at 2.75 Å resolution in an inactive state bound with a peptide antagonist. Underpinned by structural homology models of MC4R complexes simulating a presumably active-state conformation compared to the structure of the inactive state, we here briefly summarize the current understanding and key players involved in the MC4R switching process between different activity states. Finally, these perspectives highlight the complexity and plasticity in MC4R signaling regulation and identify gaps in our current knowledge.
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Kühnen P, Wiegand S, Biebermann H. Pharmacological treatment strategies for patients with monogenic obesity. J Pediatr Endocrinol Metab 2020; 33:/j/jpem.ahead-of-print/jpem-2020-0129/jpem-2020-0129.xml. [PMID: 32619193 DOI: 10.1515/jpem-2020-0129] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Accepted: 04/04/2020] [Indexed: 12/29/2022]
Abstract
The leptin melanocortin signaling pathway is playing a pivotal role for body weight regulation. Genetic defects within this cascade are leading to severe hyperphagia and early onset obesity. In most cases, due to persistent hyperphagia the affected patients are not able to stabilize body weight for a longer period of time with conservative treatment strategies based on lifestyle interventions. Therefore, it is of importance to implement alternative treatment options for these patients. This review provides an overview about the published pharmacological treatment attempts in respect to monogenic forms of obesity and summarizes recent research progress about the role of MC4R signaling and POMC derivatives for body weight regulation.
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Affiliation(s)
- Peter Kühnen
- Institute for Experimental Pediatric Endocrinology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Berlin, Germany
- Berlin Institute of Health, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Susanna Wiegand
- Berlin Institute of Health, Augustenburger Platz 1, 13353 Berlin, Germany
- Center for Social-Pediatric Care, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Heike Biebermann
- Institute for Experimental Pediatric Endocrinology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Berlin, Germany
- Berlin Institute of Health, Augustenburger Platz 1, 13353 Berlin, Germany
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16
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Sharma S, Thibodeau S, Lytton J. Signal pathway analysis of selected obesity-associated melanocortin-4 receptor class V mutants. Biochim Biophys Acta Mol Basis Dis 2020; 1866:165835. [PMID: 32423884 DOI: 10.1016/j.bbadis.2020.165835] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 04/18/2020] [Accepted: 05/06/2020] [Indexed: 01/30/2023]
Abstract
Mutations in the melanocortin-4 receptor (MC4R) in humans are the single most common cause of rare monogenic 1severe obesity, and polymorphisms in this gene are also associated with obesity in the general population. The MC4R is a G-protein coupled receptor, and in vitro analysis suggests that MC4R can signal through several different G-protein subtypes. In vivo studies show complex outcomes, with different G-proteins in different cells responsible for different physiological responses linked to obesity. There is an emerging consensus that Gαq-linked signals in the paraventricular nucleus of the hypothalamus are essential for normal satiety and the control of feeding behavior. Many MC4R mutations have been analyzed for the molecular defect underlying their association with obesity, which has revealed a group - referred to as class V mutants - with no measurable change in receptor function. However, Gαq-linked signaling leading to Ca2+ release has only been examined for a few MC4R mutations. In this study, we have examined seven MC4R class V mutants, as well as two other well-characterized signal-defective mutants as controls, with respect to G-protein signaling coupled to cAMP production, mitogen-activated protein kinase (MAPK) activation, and Ca2+ release. These data confirm, with one exception (E308K), the expected pattern of cAMP and MAPK signaling for wild type and mutant MC4R. Our results also demonstrate normal MSH-induced Ca2+ signals for wild type as well as all the class V mutants, but not the signal-defective controls. Thus, the means by which class V MC4R mutations lead to obesity remains an open question.
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Affiliation(s)
- Sunita Sharma
- Department of Biochemistry & Molecular Biology, Libin Cardiovascular Institute and Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Canada
| | - Stephanie Thibodeau
- Department of Biochemistry & Molecular Biology, Libin Cardiovascular Institute and Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Canada
| | - Jonathan Lytton
- Department of Biochemistry & Molecular Biology, Libin Cardiovascular Institute and Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Canada.
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17
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Differential Signaling Profiles of MC4R Mutations with Three Different Ligands. Int J Mol Sci 2020; 21:ijms21041224. [PMID: 32059383 PMCID: PMC7072973 DOI: 10.3390/ijms21041224] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Revised: 02/06/2020] [Accepted: 02/06/2020] [Indexed: 12/21/2022] Open
Abstract
The melanocortin 4 receptor (MC4R) is a key player in hypothalamic weight regulation and energy expenditure as part of the leptin–melanocortin pathway. Mutations in this G protein coupled receptor (GPCR) are the most common cause for monogenetic obesity, which appears to be mediated by changes in the anorectic action of MC4R via GS-dependent cyclic adenosine-monophosphate (cAMP) signaling as well as other signaling pathways. To study potential bias in the effects of MC4R mutations between the different signaling pathways, we investigated three major MC4R mutations: a GS loss-of-function (S127L) and a GS gain-of-function mutant (H158R), as well as the most common European single nucleotide polymorphism (V103I). We tested signaling of all four major G protein families plus extracellular regulated kinase (ERK) phosphorylation and β-arrestin2 recruitment, using the two endogenous agonists, α- and β-melanocyte stimulating hormone (MSH), along with a synthetic peptide agonist (NDP-α-MSH). The S127L mutation led to a full loss-of-function in all investigated pathways, whereas V103I and H158R were clearly biased towards the Gq/11 pathway when challenged with the endogenous ligands. These results show that MC4R mutations can cause vastly different changes in the various MC4R signaling pathways and highlight the importance of a comprehensive characterization of receptor mutations.
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Rao YZ, Chen R, Zhang Y, Tao YX. Orange-spotted grouper melanocortin-4 receptor: Modulation of signaling by MRAP2. Gen Comp Endocrinol 2019; 284:113234. [PMID: 31398355 DOI: 10.1016/j.ygcen.2019.113234] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2019] [Revised: 07/02/2019] [Accepted: 07/28/2019] [Indexed: 02/06/2023]
Abstract
Melanocortin-4 receptor (MC4R) and melanocortin receptor accessory protein 2 (MRAP2) play important roles in the melanocortin system, and interaction of MC4R and MRAP2 is suggested to play pivotal role in energy balance of vertebrates. Orange-spotted grouper (Epinephelus coioides) is a widely cultured marine fish with high economic value in Asia. To explore potential interaction between grouper MC4R and MRAP2, herein we cloned grouper mc4r and mrap2. Grouper mc4r consisted of a 981 bp ORF encoding a putative protein of 327 amino acids, while the grouper mrap2 consisted of a 696 bp ORF encoding a putative protein of 232 amino acids. Sequence and phylogenetic analysis revealed that the grouper MC4R and MRAP2 were highly homologous at amino acid levels to several teleost MC4Rs and MRAP2s, respectively. qRT-PCR results showed that both mc4r and mrap2 were expressed primarily in the central nervous system. In the periphery, these genes were expressed more widely in male fish. The cloned grouper MC4R was functional, exhibiting high constitutive activity in cAMP pathway, capable of binding to three peptide agonists and increasing intracellular cAMP production dose-dependently. MRAP2 significantly decreased basal and agonist-stimulated cAMP signaling. MRAP2 also increased basal ERK1/2 activation but decreased ligand-induced stimulation when expressed at high levels. These data will facilitate future investigation of these molecules in regulating diverse physiological processes in orange-spotted grouper.
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Affiliation(s)
- Ying-Zhu Rao
- Institute of Applied Biotechnology, Life Science and Technology School, Lingnan Normal University, Zhanjiang 524048, Guangdong, China; Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, United States
| | - Rong Chen
- Institute of Applied Biotechnology, Life Science and Technology School, Lingnan Normal University, Zhanjiang 524048, Guangdong, China
| | - Yong Zhang
- Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266373, China
| | - Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, United States.
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19
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Baldini G, Phelan KD. The melanocortin pathway and control of appetite-progress and therapeutic implications. J Endocrinol 2019; 241:R1-R33. [PMID: 30812013 PMCID: PMC6500576 DOI: 10.1530/joe-18-0596] [Citation(s) in RCA: 123] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Accepted: 01/22/2019] [Indexed: 12/19/2022]
Abstract
The initial discovery that ob/ob mice become obese because of a recessive mutation of the leptin gene has been crucial to discover the melanocortin pathway to control appetite. In the melanocortin pathway, the fed state is signaled by abundance of circulating hormones such as leptin and insulin, which bind to receptors expressed at the surface of pro-opiomelanocortin (POMC) neurons to promote processing of POMC to the mature hormone α-melanocyte-stimulating hormone (α-MSH). The α-MSH released by POMC neurons then signals to decrease energy intake by binding to melanocortin-4 receptor (MC4R) expressed by MC4R neurons to the paraventricular nucleus (PVN). Conversely, in the 'starved state' activity of agouti-related neuropeptide (AgRP) and of neuropeptide Y (NPY)-expressing neurons is increased by decreased levels of circulating leptin and insulin and by the orexigenic hormone ghrelin to promote food intake. This initial understanding of the melanocortin pathway has recently been implemented by the description of the complex neuronal circuit that controls the activity of POMC, AgRP/NPY and MC4R neurons and downstream signaling by these neurons. This review summarizes the progress done on the melanocortin pathway and describes how obesity alters this pathway to disrupt energy homeostasis. We also describe progress on how leptin and insulin receptors signal in POMC neurons, how MC4R signals and how altered expression and traffic of MC4R change the acute signaling and desensitization properties of the receptor. We also describe how the discovery of the melanocortin pathway has led to the use of melanocortin agonists to treat obesity derived from genetic disorders.
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Affiliation(s)
- Giulia Baldini
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Kevin D. Phelan
- Department of Neurobiology & Developmental Sciences, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
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20
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Yuan XC, Tao YX. Fenoprofen-An Old Drug Rediscovered as a Biased Allosteric Enhancer for Melanocortin Receptors. ACS Chem Neurosci 2019; 10:1066-1074. [PMID: 30168706 DOI: 10.1021/acschemneuro.8b00347] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
It is time-consuming and costly to bring new drugs to market, making it necessary and urgent to exploit existing drugs for new uses. Recently, fenoprofen was demonstrated as an allosteric modulator at melanocortin receptors (MCRs), although the exact mode of action has not been clarified. MCRs regulate multiple functions, including pigmentation, adrenal steroidogenesis, inflammation, energy homeostasis, and exocrine gland secretion. In this study, we showed that fenoprofen failed to displace the orthosteric agonist Nle4-d-Phe7-α-melanocyte stimulating hormone from binding to MC3-5R while possessing positive allosteric modulator activities at these receptors. In addition, fenoprofen induced biased signaling at MC3-5R, as it selectively activated ERK1/2 cascade but not the canonical cAMP signaling. Notably, fenoprofen stimulated biased signaling at MC3-5R, but not at MC1R, hence acting selectively among this highly conserved family of receptors. Moreover, PAM activity and biased signaling induced by fenoprofen were observed not only at wild-type but also at naturally occurring mutant MC3Rs, suggesting that this biased allosteric enhancer action might constitute as novel therapeutic opportunity for obese patients harboring these mutations. Our study might guide novel therapeutic applications for repurposing current drugs or designing new drugs combining allosteric and biased properties.
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Affiliation(s)
- Xiao-Chen Yuan
- College of Animal Science and Technology, Anhui Agricultural University, Hefei, 230036 Anhui, China
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, Alabama 36849, United States
| | - Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, Alabama 36849, United States
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21
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Kühnen P, Krude H, Biebermann H. Melanocortin-4 Receptor Signalling: Importance for Weight Regulation and Obesity Treatment. Trends Mol Med 2019; 25:136-148. [PMID: 30642682 DOI: 10.1016/j.molmed.2018.12.002] [Citation(s) in RCA: 100] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Revised: 12/03/2018] [Accepted: 12/04/2018] [Indexed: 01/08/2023]
Abstract
The melanocortin-4 receptor (MC4R) - embedded in the leptin-melanocortin pathway - is activated by proopiomelanocortin (POMC)-derived neuropeptides such as α- and β-melanocyte-stimulating hormone (MSH) and plays an important role in hypothalamic body-weight regulation. Accordingly, MC4R is a potential drug target to combat obesity. Previous attempts to develop MC4R agonists failed due to ineffectiveness or severe adverse events. Recently, a new generation of MC4R ligands was developed. Specifically, setmelanotide was found to be effective by inducing biased signalling of the MC4R and thereby reducing feelings of hunger and leading to substantial weight loss in patients with POMC or leptin receptor deficiency. This new potential pharmacological treatment option could be beneficial for further groups of obese patients with defects in the leptin-melanocortin signalling pathway.
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Affiliation(s)
- Peter Kühnen
- Institute for Experimental Pediatric Endocrinology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Augustenburger Platz 1, 13353 Berlin, Germany.
| | - Heiko Krude
- Institute for Experimental Pediatric Endocrinology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Heike Biebermann
- Institute for Experimental Pediatric Endocrinology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Augustenburger Platz 1, 13353 Berlin, Germany
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22
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Anderson EJP, Ghamari-Langroudi M, Cakir I, Litt MJ, Chen V, Reggiardo RE, Millhauser GL, Cone RD. Late onset obesity in mice with targeted deletion of potassium inward rectifier Kir7.1 from cells expressing the melanocortin-4 receptor. J Neuroendocrinol 2019; 31:e12670. [PMID: 30561082 PMCID: PMC6533113 DOI: 10.1111/jne.12670] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Revised: 11/21/2018] [Accepted: 12/11/2018] [Indexed: 01/01/2023]
Abstract
Energy stores in fat tissue are determined in part by the activity of hypothalamic neurones expressing the melanocortin-4 receptor (MC4R). Even a partial reduction in MC4R expression levels in mice, rats or humans produces hyperphagia and morbid obesity. Thus, it is of great interest to understand the molecular basis of neuromodulation by the MC4R. The MC4R is a G protein-coupled receptor that signals efficiently through GαS , and this signalling pathway is essential for normal MC4R function in vivo. However, previous data from hypothalamic slice preparations indicated that activation of the MC4R depolarised neurones via G protein-independent regulation of the ion channel Kir7.1. In the present study, we show that deletion of Kcnj13 (ie, the gene encoding Kir7.1) specifically from MC4R neurones produced resistance to melanocortin peptide-induced depolarisation of MC4R paraventricular nucleus neurones in brain slices, resistance to the sustained anorexic effect of exogenously administered melanocortin peptides, late onset obesity, increased linear growth and glucose intolerance. Some MC4R-mediated phenotypes appeared intact, including Agouti-related peptide-induced stimulation of food intake and MC4R-mediated induction of peptide YY release from intestinal L cells. Thus, a subset of the consequences of MC4R signalling in vivo appears to be dependent on expression of the Kir7.1 channel in MC4R cells.
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Affiliation(s)
- E. J. P. Anderson
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee
| | - M. Ghamari-Langroudi
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee
| | - I. Cakir
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan
| | - M. J. Litt
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee
| | - Valerie Chen
- Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, California
| | - Roman E. Reggiardo
- Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, California
| | - Glenn L. Millhauser
- Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, California
| | - R. D. Cone
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan
- Department of Molecular and Integrative Pharmacology, School of Medicine, University of Michigan, Ann Arbor, Michigan
- Correspondence: Roger D. Cone, Life Sciences Institute, 210 Washtenaw Ave., Ann Arbor, MI 48109,
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Wang W, Guo DY, Lin YJ, Tao YX. Melanocortin Regulation of Inflammation. Front Endocrinol (Lausanne) 2019; 10:683. [PMID: 31649620 PMCID: PMC6794349 DOI: 10.3389/fendo.2019.00683] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Accepted: 09/19/2019] [Indexed: 12/18/2022] Open
Abstract
Adrenocorticotropic hormone (ACTH), and α-, β-, and γ-melanocyte-stimulating hormones (α-, β-, γ-MSH), collectively known as melanocortins, together with their receptors (melanocortin receptors), are components of an ancient modulatory system. The clinical use of ACTH in the treatment of rheumatoid arthritis started in 1949, originally thought that the anti-inflammatory action was through hypothalamus-pituitary-adrenal axis and glucocorticoid-dependent. Subsequent decades have witnessed extensive attempts in unraveling the physiology and pharmacology of the melanocortin system. It is now known that ACTH, together with α-, β-, and γ-MSHs, also possess glucocorticoid-independent anti-inflammatory and immunomodulatory effects by activating the melanocortin receptors expressed in the brain or peripheral immune cells. This review will briefly introduce the melanocortin system and highlight the action of melanocortins in the regulation of immune functions from in vitro, in vivo, preclinical, and clinical studies. The potential therapeutic use of melanocortins are also summarized.
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Affiliation(s)
- Wei Wang
- Department of Clinical Laboratory, Xiamen Huli Guoyu Clinic, Co., Ltd., Xiamen, China
| | - Dong-Yu Guo
- Department of Clinical Laboratory, Xiamen Huli Guoyu Clinic, Co., Ltd., Xiamen, China
- *Correspondence: Dong-Yu Guo
| | - Yue-Jun Lin
- Department of Clinical Laboratory, Xiamen Huli Guoyu Clinic, Co., Ltd., Xiamen, China
| | - Ya-Xiong Tao
- Department of Anatomy, Physiology, and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL, United States
- Ya-Xiong Tao
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24
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Yi TL, Yang LK, Ruan GL, Yang DQ, Tao YX. Melanocortin-4 receptor in swamp eel (Monopterus albus): Cloning, tissue distribution, and pharmacology. Gene 2018; 678:79-89. [PMID: 30075196 DOI: 10.1016/j.gene.2018.07.056] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Revised: 07/14/2018] [Accepted: 07/23/2018] [Indexed: 01/10/2023]
Abstract
Melanocortin-4 receptor (MC4R) plays critical roles in the regulation of various physiological processes, such as energy homeostasis, reproduction and sexual function, cardiovascular function, and other functions in mammals. Although the functions of the MC4R in fish have not been extensively studied, the importance of MC4R in regulation of piscine energy expenditure and sexual functions is emerging. Swamp eel (Monopterus albus) is an economically and evolutionarily important fish widely distributed in tropics and subtropics. We cloned swamp eel mc4r (mamc4r), consisting of a 981 bp open reading frame encoding a protein of 326 amino acids. The sequence of maMC4R was homologous to those of several teleost MC4Rs. Phylogenetic and chromosomal synteny analyses showed that maMC4R was closely related to piscine MC4Rs. qRT-PCR revealed that mc4r transcripts were highly expressed in brain and gonads of swamp eel. The maMC4R was further demonstrated to be a functional receptor by pharmacological studies. Four agonists, α-melanocyte stimulating hormone (α-MSH), β-MSH, [Nle4, D-Phe7]-α-MSH (NDP-MSH), and adrenocorticotropin, could bind to maMC4R and induce intracellular cAMP production dose-dependently. Small molecule agonist THIQ allosterically bound to maMC4R and exerted its effect. Similar to other fish MC4Rs, maMC4R also exhibited significantly increased basal activity compared with that of human MC4R. The high basal activity of maMC4R could be decreased by inverse agonist ML00253764, suggesting that maMC4R was indeed constitutively active. The availability of maMC4R and its pharmacological characteristics will facilitate the investigation of its function in regulating diverse physiological processes in swamp eel.
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Affiliation(s)
- Ti-Lin Yi
- School of Animal Science, Yangtze University, Jingzhou 434020, Hubei, China
| | - Li-Kun Yang
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, United States
| | - Guo-Liang Ruan
- School of Animal Science, Yangtze University, Jingzhou 434020, Hubei, China
| | - Dai-Qin Yang
- School of Animal Science, Yangtze University, Jingzhou 434020, Hubei, China
| | - Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, United States.
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25
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Liu S, Marcelin G, Blouet C, Jeong JH, Jo YH, Schwartz GJ, Chua S. A gut-brain axis regulating glucose metabolism mediated by bile acids and competitive fibroblast growth factor actions at the hypothalamus. Mol Metab 2017; 8:37-50. [PMID: 29290621 PMCID: PMC5985052 DOI: 10.1016/j.molmet.2017.12.003] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Revised: 11/27/2017] [Accepted: 12/05/2017] [Indexed: 12/17/2022] Open
Abstract
OBJECTIVE Bile acids have been implicated as important regulators of glucose metabolism via activation of FXR and GPBAR1. We have previously shown that FGF19 can modulate glucose handling by suppressing the activity of hypothalamic AGRP/NPY neurons. As bile acids stimulate the release of FGF19/FGF15 into the circulation, we pursued the potential of bile acids to improve glucose tolerance via a gut-brain axis involving FXR and FGF15/FGF19 within enterocytes and FGF receptors on hypothalamic AGRP/NPY neurons. METHODS A 5-day gavage of taurocholic acid, mirroring our previous protocol of a 5-day FGF19 treatment, was performed. Oral glucose tolerance tests in mice with genetic manipulations of FGF signaling and melanocortin signaling were used to define a gut-brain axis responsive to bile acids. RESULTS The taurocholic acid gavage led to increased serum concentrations of taurocholic acid as well as increases of FGF15 mRNA in the ileum and improved oral glucose tolerance in obese (ob/ob) mice. In contrast, lithocholic acid, an FXR antagonist but a potent agonist for GPBAR1, did not improve glucose tolerance. The positive response to taurocholic acid is dependent upon an intact melanocortinergic system as obese MC4R-null mice or ob/ob mice without AGRP did not show improvements in glucose tolerance after taurocholate gavage. We also tested the FGF receptor isoform necessary for the bile acid response, using AGRP:Fgfr1-/- and AGRP:Fgfr2-/- mice. While the absence of FGFR1 in AGRP/NPY neurons did not alter glucose tolerance after taurocholate gavage, manipulations of Fgfr2 caused bidirectional changes depending upon the experimental model. We hypothesized the existence of an endogenous hypothalamic FGF, most likely FGF17, that acted as a chronic activator of AGRP/NPY neurons. We developed two short peptides based on FGF8 and FGF17 that should antagonize FGF17 action. Both of these peptides improved glucose homeostasis after a 4-day course of central and peripheral injections. Significantly, daily average blood glucose from continuous glucose monitoring was reduced in all tested animals but glucose concentrations remained in the euglycemia range. CONCLUSIONS We have defined a gut-brain axis that regulates glucose metabolism mediated by antagonistic fibroblast growth factors. From the intestine, bile acids stimulate FGF15 secretion, leading to activation of the FGF receptors in hypothalamic AGRP/NPY neurons. FGF receptor intracellular signaling subsequently silences AGRP/NPY neurons, leading to improvements of glucose tolerance that are likely mediated by the autonomic nervous system. Finally, short peptides that antagonize homodimeric FGF receptor signaling within the hypothalamus have beneficial effects on glucose homeostasis without inducing hypoglycemia. These peptides could provide a new mode of regulating glucose metabolism.
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Affiliation(s)
- Shunmei Liu
- Department of Medicine, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
| | - Genevieve Marcelin
- INSERM UMR S 1166, ICAN Institute, Faculte de Medecine Pitie-Salpetriere, 91 Boulevard de l'Hopital, 75013 Paris, France
| | - Clemence Blouet
- MRC Metabolic Diseases Unit, Metabolic Research Laboratories, University of Cambridge, Cambridge, United Kingdom
| | - Jae Hoon Jeong
- Department of Medicine, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
| | - Young-Hwan Jo
- Department of Medicine, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
| | - Gary J Schwartz
- Department of Medicine, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
| | - Streamson Chua
- Department of Medicine, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
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26
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Doering SR, Freeman KT, Schnell SM, Haslach EM, Dirain M, Debevec G, Geer P, Santos RG, Giulianotti MA, Pinilla C, Appel JR, Speth RC, Houghten RA, Haskell-Luevano C. Discovery of Mixed Pharmacology Melanocortin-3 Agonists and Melanocortin-4 Receptor Tetrapeptide Antagonist Compounds (TACOs) Based on the Sequence Ac-Xaa 1-Arg-(pI)DPhe-Xaa 4-NH 2. J Med Chem 2017; 60:4342-4357. [PMID: 28453292 DOI: 10.1021/acs.jmedchem.7b00301] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The centrally expressed melanocortin-3 and -4 receptors (MC3R/MC4R) have been studied as possible targets for weight management therapies, with a preponderance of studies focusing on the MC4R. Herein, a novel tetrapeptide scaffold [Ac-Xaa1-Arg-(pI)DPhe-Xaa4-NH2] is reported. The scaffold was derived from results obtained from a MC3R mixture-based positional scanning campaign. From these results, a set of 48 tetrapeptides were designed and pharmacologically characterized at the mouse melanocortin-1, -3, -4, and -5 receptors. This resulted in the serendipitous discovery of nine compounds that were MC3R agonists (EC50 < 1000 nM) and MC4R antagonists (5.7 < pA2 < 7.8). The three most potent MC3R agonists, 18 [Ac-Arg-Arg-(pI)DPhe-Tic-NH2], 1 [Ac-His-Arg-(pI)DPhe-Tic-NH2], and 41 [Ac-Arg-Arg-(pI)DPhe-DNal(2')-NH2] were more potent (EC50 < 73 nM) than the melanocortin tetrapeptide Ac-His-DPhe-Arg-Trp-NH2. This template contains a sequentially reversed "Arg-(pI)DPhe" motif with respect to the classical "Phe-Arg" melanocortin signaling motif, which results in pharmacology that is first-in-class for the central melanocortin receptors.
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Affiliation(s)
- Skye R Doering
- Department of Medicinal Chemistry, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Katie T Freeman
- Department of Medicinal Chemistry, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Sathya M Schnell
- Department of Medicinal Chemistry, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Erica M Haslach
- Department of Pharmacodynamics, University of Florida , Gainesville, Florida 32610, United States
| | - Marvin Dirain
- Department of Pharmacodynamics, University of Florida , Gainesville, Florida 32610, United States
| | - Ginamarie Debevec
- Torrey Pines Institute for Molecular Studies , Port St. Lucie, Florida 34987, United States
| | - Phaedra Geer
- Torrey Pines Institute for Molecular Studies , Port St. Lucie, Florida 34987, United States
| | - Radleigh G Santos
- Torrey Pines Institute for Molecular Studies , Port St. Lucie, Florida 34987, United States
| | - Marc A Giulianotti
- Torrey Pines Institute for Molecular Studies , Port St. Lucie, Florida 34987, United States
| | - Clemencia Pinilla
- Torrey Pines Institute for Molecular Studies , San Diego, California 92121, United States
| | - Jon R Appel
- Torrey Pines Institute for Molecular Studies , San Diego, California 92121, United States
| | - Robert C Speth
- College of Pharmacy, Nova Southeastern University , Fort Lauderdale, Florida 33328, United States.,Department of Pharmacology and Physiology, Georgetown University , Washington, D.C. 20057, United States
| | - Richard A Houghten
- Torrey Pines Institute for Molecular Studies , Port St. Lucie, Florida 34987, United States.,Torrey Pines Institute for Molecular Studies , San Diego, California 92121, United States
| | - Carrie Haskell-Luevano
- Department of Medicinal Chemistry, University of Minnesota , Minneapolis, Minnesota 55455, United States.,Department of Pharmacodynamics, University of Florida , Gainesville, Florida 32610, United States
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27
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Yang LK, Tao YX. Biased signaling at neural melanocortin receptors in regulation of energy homeostasis. Biochim Biophys Acta Mol Basis Dis 2017; 1863:2486-2495. [PMID: 28433713 DOI: 10.1016/j.bbadis.2017.04.010] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Revised: 04/09/2017] [Accepted: 04/10/2017] [Indexed: 12/15/2022]
Abstract
The global prevalence of obesity highlights the importance of understanding on regulation of energy homeostasis. The central melanocortin system is an important intersection connecting the neural pathways controlling satiety and energy expenditure to regulate energy homeostasis by sensing and integrating the signals of external stimuli. In this system, neural melanocortin receptors (MCRs), melanocortin-3 and -4 receptors (MC3R and MC4R), play crucial roles in the regulation of energy homeostasis. Recently, multiple intracellular signaling pathways and biased signaling at neural MCRs have been discovered, providing new insights into neural MCR signaling. This review attempts to summarize biased signaling including biased receptor mutants (both naturally occurring and lab-generated) and biased ligands at neural MCRs, and to provide a better understanding of obesity pathogenesis and new therapeutic implications for obesity treatment.
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Affiliation(s)
- Li-Kun Yang
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, United States
| | - Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, United States.
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28
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Ericson MD, Freeman KT, Schnell SM, Haskell-Luevano C. A Macrocyclic Agouti-Related Protein/[Nle 4,DPhe 7]α-Melanocyte Stimulating Hormone Chimeric Scaffold Produces Subnanomolar Melanocortin Receptor Ligands. J Med Chem 2017; 60:805-813. [PMID: 28045525 DOI: 10.1021/acs.jmedchem.6b01707] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The melanocortin system consists of five receptor subtypes, endogenous agonists, and naturally occurring antagonists. These receptors and ligands have been implicated in numerous biological pathways including processes linked to obesity and food intake. Herein, a truncation structure-activity relationship study of chimeric agouti-related protein (AGRP)/[Nle4,DPhe7]α-melanocyte stimulating hormone (NDP-MSH) ligands is reported. The tetrapeptide His-DPhe-Arg-Trp or tripeptide DPhe-Arg-Trp replaced the Arg-Phe-Phe sequence in the AGRP active loop derivative c[Pro-Arg-Phe-Phe-Xxx-Ala-Phe-DPro], where Xxx was the native Asn of AGRP or a diaminopropionic (Dap) acid residue previously shown to increase antagonist potency at the mMC4R. The Phe, Ala, and Dap/Asn residues were successively removed to generate a 14-member library that was assayed for agonist activity at the mouse MC1R, MC3R, MC4R, and MC5R. Two compounds possessed nanomolar agonist potency at the mMC4R, c[Pro-His-DPhe-Arg-Trp-Asn-Ala-Phe-DPro] and c[Pro-His-DPhe-Arg-Trp-Dap-Ala-DPro], and may be further developed to generate novel melanocortin probes and ligands for understanding and treating obesity.
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Affiliation(s)
- Mark D Ericson
- Department of Medicinal Chemistry, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Katie T Freeman
- Department of Medicinal Chemistry, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Sathya M Schnell
- Department of Medicinal Chemistry, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Carrie Haskell-Luevano
- Department of Medicinal Chemistry, University of Minnesota , Minneapolis, Minnesota 55455, United States
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29
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Agosti F, Cordisco Gonzalez S, Martinez Damonte V, Tolosa MJ, Di Siervi N, Schioth HB, Davio C, Perello M, Raingo J. Melanocortin 4 receptor constitutive activity inhibits L-type voltage-gated calcium channels in neurons. Neuroscience 2017; 346:102-112. [PMID: 28093215 DOI: 10.1016/j.neuroscience.2017.01.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Revised: 12/16/2016] [Accepted: 01/05/2017] [Indexed: 11/19/2022]
Abstract
The melanocortin 4 receptor (MC4R) is a G protein-coupled receptor (GPCR) that is expressed in several brain nuclei playing a crucial role in the regulation of energy balance controlling the homeostasis of the organism. It displays both agonist-evoked and constitutive activity, and moreover, it can couple to different G proteins. Most of the research on MC4R has been focused on agonist-induced activity, while the molecular and cellular basis of MC4R constitutive activity remains scarcely studied. We have previously shown that neuronal N-type voltage-gated calcium channels (CaV2.2) are inhibited by MC4R agonist-dependent activation, while the CaV subtypes that carry L- and P/Q-type current are not. Here, we tested the hypothesis that MC4R constitutive activity can affect CaV, with focus on the channel subtypes that can control transcriptional activity coupled to depolarization (L-type, CaV1.2/1.3) and neurotransmitter release (N- and P/Q-type, CaV2.2 and CaV2.1). We found that MC4R constitutive activity inhibits specifically CaV1.2/1.3 and CaV2.1 subtypes of CaV. We also explored the signaling pathways mediating this inhibition, and thus propose that agonist-dependent and basal MC4R activation modes signal differentially through Gs and Gi/o pathways to impact on different CaV subtypes. In addition, we found that chronic incubation with MC4R endogenous inverse agonist, agouti and agouti-related peptide (AgRP), occludes CaV inhibition in a cell line and in amygdaloid complex cultured neurons as well. Thus, we define new mechanisms of control of the main mediators of depolarization-induced calcium entry into neurons by a GPCR that displays constitutive activity.
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Affiliation(s)
- F Agosti
- Electrophysiology Laboratory, Multidisciplinary Institute of Cell Biology (IMBICE) Universidad de La Plata-Consejo Nacional de Investigaciones Científicas y Técnicas, CONICET, and Comision de Investigaciones de la Provincia de buenos Aires (CIC), La Plata, Buenos Aires, Argentina
| | - S Cordisco Gonzalez
- Electrophysiology Laboratory, Multidisciplinary Institute of Cell Biology (IMBICE) Universidad de La Plata-Consejo Nacional de Investigaciones Científicas y Técnicas, CONICET, and Comision de Investigaciones de la Provincia de buenos Aires (CIC), La Plata, Buenos Aires, Argentina
| | - V Martinez Damonte
- Electrophysiology Laboratory, Multidisciplinary Institute of Cell Biology (IMBICE) Universidad de La Plata-Consejo Nacional de Investigaciones Científicas y Técnicas, CONICET, and Comision de Investigaciones de la Provincia de buenos Aires (CIC), La Plata, Buenos Aires, Argentina
| | - M J Tolosa
- Electrophysiology Laboratory, Multidisciplinary Institute of Cell Biology (IMBICE) Universidad de La Plata-Consejo Nacional de Investigaciones Científicas y Técnicas, CONICET, and Comision de Investigaciones de la Provincia de buenos Aires (CIC), La Plata, Buenos Aires, Argentina
| | - N Di Siervi
- Instituto de Investigaciones Farmacológicas, ININFA, Universidad de Buenos Aires-Consejo Nacional de Investigaciones Científicas y Técnicas, CONICET, Buenos Aires, Argentina
| | - H B Schioth
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Uppsala, Sweden
| | - C Davio
- Instituto de Investigaciones Farmacológicas, ININFA, Universidad de Buenos Aires-Consejo Nacional de Investigaciones Científicas y Técnicas, CONICET, Buenos Aires, Argentina
| | - M Perello
- Neurophysiology Laboratory, Multidisciplinary Institute of Cell Biology (IMBICE) Universidad de La Plata-Consejo Nacional de Investigaciones Científicas y Técnicas, CONICET, and Comision de Investigaciones de la Provincia de buenos Aires (CIC), La Plata, Buenos Aires, Argentina
| | - J Raingo
- Electrophysiology Laboratory, Multidisciplinary Institute of Cell Biology (IMBICE) Universidad de La Plata-Consejo Nacional de Investigaciones Científicas y Técnicas, CONICET, and Comision de Investigaciones de la Provincia de buenos Aires (CIC), La Plata, Buenos Aires, Argentina
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30
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Xiong Q, Chai J, Chen M, Tao YX. Identification and pharmacological analyses of eight naturally occurring caprine melanocortin-1 receptor mutations in three different goat breeds. Gen Comp Endocrinol 2016; 235:1-10. [PMID: 27229376 DOI: 10.1016/j.ygcen.2016.05.023] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Revised: 05/19/2016] [Accepted: 05/20/2016] [Indexed: 12/22/2022]
Abstract
The melanocortin-1 receptor (MC1R) belongs to the family of seven transmembrane G protein-coupled receptors and plays a central role in animal coat color. We have sequenced the full coding region of 954bp of the MC1R gene in 72 goats of three breeds with different coat colors and identified five missense mutations (K226E, F250V, G255D, V265I, and C267W) and one silent mutation (A61A), among which two haplotypes with complete linkage disequilibrium (A61A and F250V, G255D and V265I) were found. We performed detailed functional studies on the six single and two double mutations in transiently transfected HEK293T cells. We found that none of the mutants had decreased cell surface expression. However, all the mutants except A61A had decreased constitutive activities in the cAMP pathway. Five mutations (F250V, G255D, G267W, A61A/F250V, G255D/V265I) exhibited significant defects in ligand binding and consequent agonist-induced cAMP signaling and ERK1/2 activation. Additionally, K226E, with normal ligand binding affinity and cAMP signaling, showed a significant defect in ERK1/2 activation, exhibiting biased signaling. Co-expression studies showed that the five defective mutants did not affect wild-type MC1R signaling, hence they were not dominant negative. In summary, we provided detailed data of these goat MC1R mutations leading to a better understanding of the role of MC1R mutation and coat color in goats.
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Affiliation(s)
- Qi Xiong
- Hubei Key Laboratory of Animal Embryo Engineering and Molecular Breeding, Institute of Animal Husbandry and Veterinary Medicine, Hubei Academy of Agricultural Sciences, Wuhan, Hubei 430070, China; Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849-5519, United States
| | - Jin Chai
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849-5519, United States; Ministry of Agriculture Key Laboratory of Swine Breeding and Genetics & Key Laboratory of Agricultural Animal Genetics, Breeding, and Reproduction of Ministry of Education, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Mingxin Chen
- Hubei Key Laboratory of Animal Embryo Engineering and Molecular Breeding, Institute of Animal Husbandry and Veterinary Medicine, Hubei Academy of Agricultural Sciences, Wuhan, Hubei 430070, China
| | - Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849-5519, United States.
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31
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Yang Z, Tao YX. Biased signaling initiated by agouti-related peptide through human melanocortin-3 and -4 receptors. Biochim Biophys Acta Mol Basis Dis 2016; 1862:1485-94. [PMID: 27208795 DOI: 10.1016/j.bbadis.2016.05.008] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2016] [Revised: 05/09/2016] [Accepted: 05/16/2016] [Indexed: 01/01/2023]
Abstract
The neural melanocortin receptors (MCRs), melanocortin-3 and -4 receptors (MC3R and MC4R), have been increasingly recognized as important regulators of energy homeostasis. The orexigenic agouti-related peptide (AgRP), initially identified as an endogenous antagonist for both neural MCRs, has been suggested to be a biased agonist of MC4R independent of its antagonizing effects. In the present study, we sought to determine the potential of AgRP to regulate the activation of intracellular kinases, including extracellular signal-regulated kinase 1 and 2 (ERK1/2), AKT and AMP-activated protein kinase (AMPK), through neural MCRs. We showed that AgRP acted as a biased agonist in human MC3R (hMC3R), decreasing cAMP activity of constitutively active mutant (F347A) hMC3R but stimulating ERK1/2 activation in both wide type and F347A hMC3Rs. AgRP-stimulated ERK1/2 phosphorylation through MC3R was abolished by protein kinase A (PKA) inhibitor H-89 but not Rp-cAMPS, whereas AgRP-initiated ERK1/2 activation through MC4R was inhibited by phosphatidylinositol 3-kinase (PI3K) inhibitors wortmannin and LY294002. Both NDP-MSH and AgRP treatment induced significant AKT phosphorylation in GT1-7 cells but not in MC3R- or MC4R-transfected HEK293T cells. The phosphorylated AMPK levels in both GT1-7 cells and HERK293T cells transfected with neural MCRs were significantly decreased upon stimulation with NDP-MSH but not with AgRP. In summary, we provided novel data for AgRP-initiated multiple intracellular signaling pathways, demonstrating biased agonism of AgRP in both neural MCRs, leading to a better understanding of neural MCR pharmacology.
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MESH Headings
- AMP-Activated Protein Kinases/metabolism
- Agouti-Related Protein/metabolism
- Amino Acid Substitution
- Central Nervous System/metabolism
- Cyclic AMP/metabolism
- HEK293 Cells
- Humans
- Kinetics
- Ligands
- MAP Kinase Signaling System
- Mutagenesis, Site-Directed
- Peptide Fragments/metabolism
- Proto-Oncogene Proteins c-akt/metabolism
- Receptor, Melanocortin, Type 3/agonists
- Receptor, Melanocortin, Type 3/genetics
- Receptor, Melanocortin, Type 3/metabolism
- Receptor, Melanocortin, Type 4/agonists
- Receptor, Melanocortin, Type 4/genetics
- Receptor, Melanocortin, Type 4/metabolism
- Recombinant Proteins/genetics
- Recombinant Proteins/metabolism
- Signal Transduction
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Affiliation(s)
- Zhao Yang
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, United States
| | - Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, United States.
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32
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Wang W, Tao YX. Ghrelin Receptor Mutations and Human Obesity. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2016; 140:131-50. [PMID: 27288828 DOI: 10.1016/bs.pmbts.2016.02.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Growth hormone secretagogue receptor (GHSR) was originally identified as an orphan receptor in porcine and rat anterior pituitary membranes. In 1999, GHSR was deorphanized and shown to be a receptor for ghrelin, a peptide hormone secreted from the stomach. Therefore, GHSR is also called ghrelin receptor. In addition to regulating growth hormone secretion, ghrelin receptor regulates various physiological processes, including food intake and energy expenditure, glucose metabolism, cardiovascular functions, gastric acid secretion and motility, and immune function. Several human genetic studies conducted in populations originated from Europe, Africa, South America, and East Asia identified rare mutations and single nucleotide polymorphisms that might be associated with human obesity and short stature. Functional analyses of mutant GHSRs reveal multiple defects, including cell surface expression, ligand binding, and basal and stimulated signaling. With growing understanding in the functionality of naturally occurring GHSR mutations, potential therapeutic strategies including pharmacological chaperones and novel ligands could be used to correct the GHSR mutants.
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Affiliation(s)
- W Wang
- Department of Anatomy, Physiology, and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, Alabama, USA
| | - Y-X Tao
- Department of Anatomy, Physiology, and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, Alabama, USA.
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33
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Jackson DS, Ramachandrappa S, Clark AJ, Chan LF. Melanocortin receptor accessory proteins in adrenal disease and obesity. Front Neurosci 2015; 9:213. [PMID: 26113808 PMCID: PMC4461818 DOI: 10.3389/fnins.2015.00213] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Accepted: 05/28/2015] [Indexed: 12/02/2022] Open
Abstract
Melanocortin receptor accessory proteins (MRAPs) are regulators of the melanocortin receptor family. MRAP is an essential accessory factor for the functional expression of the MC2R/ACTH receptor. The importance of MRAP in adrenal gland physiology is demonstrated by the clinical condition familial glucocorticoid deficiency type 2. The role of its paralog melanocortin-2-receptor accessory protein 2 (MRAP2), which is predominantly expressed in the hypothalamus including the paraventricular nucleus, has recently been linked to mammalian obesity. Whole body deletion and targeted brain specific deletion of the Mrap2 gene result in severe obesity in mice. Interestingly, Mrap2 complete knockout (KO) mice have increased body weight without detectable changes to food intake or energy expenditure. Rare heterozygous variants of MRAP2 have been found in humans with severe, early-onset obesity. In vitro data have shown that Mrap2 interaction with the melanocortin-4-receptor (Mc4r) affects receptor signaling. However, the mechanism by which Mrap2 regulates body weight in vivo is not fully understood and differences between the phenotypes of Mrap2 and Mc4r KO mice may point toward Mc4r independent mechanisms.
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Affiliation(s)
- David S Jackson
- Centre for Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London London, UK
| | - Shwetha Ramachandrappa
- Centre for Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London London, UK
| | - Adrian J Clark
- Centre for Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London London, UK
| | - Li F Chan
- Centre for Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London London, UK
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34
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Mountjoy KG. Pro-Opiomelanocortin (POMC) Neurones, POMC-Derived Peptides, Melanocortin Receptors and Obesity: How Understanding of this System has Changed Over the Last Decade. J Neuroendocrinol 2015; 27:406-18. [PMID: 25872650 DOI: 10.1111/jne.12285] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Revised: 04/04/2015] [Accepted: 04/07/2015] [Indexed: 12/19/2022]
Abstract
Following the cloning of the melanocortin receptor and agouti protein genes, a model was developed for the central melanocortin system with respect to the regulation of energy and glucose homeostasis. This model comprised leptin regulation of melanocortin peptides and agouti-related peptide (AgRP) produced from central pro-opiomelanocortin (POMC) and AgRP neurones, respectively, as well as AgRP competitive antagonism of melanocortin peptides activating melanocortin 4 receptor (MC4R) to Gαs and the cAMP signalling pathway. In the last decade, there have been paradigm shifts in our understanding of the central melanocortin system as a result of the application of advanced new technologies, including Cre-LoxP transgenic mouse technology, pharmacogenetics and optogenetics. During this period, our understanding of G protein coupled receptor signal transduction has also dramatically changed, such that these receptors are now known to exist in the plasma membrane oscillating between various inactive and active conformational states, and the active states signal through G protein-dependent and G protein-independent pathways. The present review focuses on evidence obtained over the past decade that has changed our understanding of POMC gene expression and regulation in the central nervous system, POMC and AgRP neuronal circuitry, neuroanatomical functions of melanocortin receptors, melanocortin 3 receptor (MC3R) and MC4R, and signal transduction through MC3R and MC4R.
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Affiliation(s)
- K G Mountjoy
- Departments of Physiology and Molecular Medicine and Pathology, School of Medical Sciences, Faculty of Medical and Health Sciences and Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Auckland, New Zealand
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35
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Ericson MD, Wilczynski A, Sorensen NB, Xiang Z, Haskell-Luevano C. Discovery of a β-Hairpin Octapeptide, c[Pro-Arg-Phe-Phe-Dap-Ala-Phe-DPro], Mimetic of Agouti-Related Protein(87-132) [AGRP(87-132)] with Equipotent Mouse Melanocortin-4 Receptor (mMC4R) Antagonist Pharmacology. J Med Chem 2015; 58:4638-47. [PMID: 25898270 DOI: 10.1021/acs.jmedchem.5b00184] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Agouti-related protein (AGRP) is a potent orexigenic peptide that antagonizes the melanocortin-3 and -4 receptors (MC3R and MC4R). While the C-terminal domain of AGRP, AGRP(87-132), is equipotent to the full-length peptide, further truncation decreases potency at the MC3R and MC4R. Herein, we report AGRP-derived peptides designed to mimic the active β-hairpin secondary structure that contains the hypothesized Arg-Phe-Phe pharmacophore. The most potent scaffold, c[Pro-Arg-Phe-Phe-Asn-Ala-Phe-DPro], comprised the hexa-peptide β-hairpin loop from AGRP cyclized through a DPro-Pro motif. A 20 compound library was synthesized from this scaffold for further structure-activity relationship studies. The most potent peptide from this library was an asparagine to diaminopropionic acid substitution that possessed sub-nanomolar antagonist activity at the mMC4R and was greater than 160-fold selective for the mMC4R versus the mMC3R. The reported ligands may serve as probes to characterize the melanocortin receptors in vivo and leads in the development of novel therapeutics.
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Affiliation(s)
- Mark D Ericson
- †Department of Medicinal Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Andrzej Wilczynski
- ‡Department of Medicinal Chemistry, University of Florida, Gainesville, Florida 32610, United States
| | - Nicholas B Sorensen
- ‡Department of Medicinal Chemistry, University of Florida, Gainesville, Florida 32610, United States
| | - Zhimin Xiang
- ‡Department of Medicinal Chemistry, University of Florida, Gainesville, Florida 32610, United States
| | - Carrie Haskell-Luevano
- †Department of Medicinal Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States.,‡Department of Medicinal Chemistry, University of Florida, Gainesville, Florida 32610, United States
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36
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Montero-Melendez T, Gobbetti T, Cooray SN, Jonassen TEN, Perretti M. Biased agonism as a novel strategy to harness the proresolving properties of melanocortin receptors without eliciting melanogenic effects. THE JOURNAL OF IMMUNOLOGY 2015; 194:3381-8. [PMID: 25725103 DOI: 10.4049/jimmunol.1402645] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
There is a need for novel approaches to control pathologies with overexuberant inflammatory reactions. Targeting melanocortin (MC) receptors represents a promising therapy for obesity and chronic inflammation, but lack of selectivity and safety concerns limit development. A new way to increase selectivity of biological effects entails the identification of biased agonists. In this study, we characterize the small molecule AP1189 as a biased agonist at receptors MC1 and MC3. Although not provoking canonical cAMP generation, AP1189 addition to MC1 or MC3, but not empty vector, transfected HEK293 cells caused ERK1/2 phosphorylation, a signaling responsible for the proefferocytic effect evoked in mouse primary macrophages. Added to macrophage cultures, AP1189 reduced cytokine release, an effect reliant on both MC1 and MC3 as evident from the use of Mc1r(-/-) and Mc3r(-/-) macrophages. No melanogenesis was induced by AP1189 in B16-F10 melanocytes. In vivo, oral AP1189 elicited anti-inflammatory actions in peritonitis and, upon administration at the peak of inflammation, accelerated the resolution phase by ∼3-fold. Finally, given the clinical efficacy of adrenocorticotropin in joint diseases, AP1189 was tested in experimental inflammatory arthritis, where this biased agonist afforded significant reduction of macroscopic and histological parameters of joint disruption. These proof-of-concept analyses with AP1189, an active oral anti-inflammatory and resolution-promoting compound, indicate that biased agonism at MC receptors is an innovative, viable approach to yield novel anti-inflammatory molecules endowed with a more favorable safety profile.
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Affiliation(s)
- Trinidad Montero-Melendez
- William Harvey Research Institute, Barts and The London School of Medicine, Queen Mary University of London, London EC1M 6BQ, United Kingdom; and
| | - Thomas Gobbetti
- William Harvey Research Institute, Barts and The London School of Medicine, Queen Mary University of London, London EC1M 6BQ, United Kingdom; and
| | - Sadani N Cooray
- William Harvey Research Institute, Barts and The London School of Medicine, Queen Mary University of London, London EC1M 6BQ, United Kingdom; and
| | - Thomas E N Jonassen
- Department of Biomedical Sciences, University of Copenhagen, DK-2200 Copenhagen, Denmark
| | - Mauro Perretti
- William Harvey Research Institute, Barts and The London School of Medicine, Queen Mary University of London, London EC1M 6BQ, United Kingdom; and
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Yang F, Huang H, Tao YX. Biased signaling in naturally occurring mutations in human melanocortin-3 receptor gene. Int J Biol Sci 2015; 11:423-33. [PMID: 25798062 PMCID: PMC4366641 DOI: 10.7150/ijbs.11032] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Accepted: 01/21/2015] [Indexed: 12/17/2022] Open
Abstract
The melanocortin-3 receptor (MC3R) is primarily expressed in the hypothalamus and plays an important role in the regulation of energy homeostasis. Recently, some studies demonstrated that MC3R also signals through mitogen-activated protein kinases (MAPKs), especially extracellular signal-regulated kinases 1 and 2 (ERK1/2). ERK1/2 signaling is known to alter gene expression, potentially contributing to the prolonged action of melanocortins on energy homeostasis regulation. In the present study, we performed detailed functional studies on 8 novel naturally occurring MC3R mutations recently reported, and the effects of endogenous MC3R agonist, α-melanocyte stimulating hormone (MSH), on ERK1/2 signaling on all 22 naturally occurring MC3R mutations reported to date. We found that mutants D158Y and L299V were potential pathogenic causes to obesity. Four residues, F82, D158, L249 and L299, played critical roles in different aspects of MC3R function. α-MSH exhibited balanced activity in Gs-cAMP and ERK1/2 signaling pathways in 15 of the 22 mutant MC3Rs. The other 7 mutant MC3Rs were biased to either one of the signaling pathways. In summary, we provided novel data about the structure-function relationship of MC3R, identifying residues important for receptor function. We also demonstrated that some mutations exhibited biased signaling, preferentially activating one intracellular signaling pathway, adding a new layer of complexity to MC3R pharmacology.
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Affiliation(s)
- Fan Yang
- 1. Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL, USA. ; 2. Current address: College of Life Sciences, Inner Mongolia Agricultural University, Hohhot, Inner Mongolia 010018, China
| | - Hui Huang
- 1. Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL, USA
| | - Ya-Xiong Tao
- 1. Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL, USA
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Tao YX. Constitutive activity in melanocortin-4 receptor: biased signaling of inverse agonists. ADVANCES IN PHARMACOLOGY 2015; 70:135-54. [PMID: 24931195 DOI: 10.1016/b978-0-12-417197-8.00005-5] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The melanocortin-4 receptor (MC4R) is a critical regulator of energy homeostasis, including both energy intake and energy expenditure. It mediates the actions of a number of hormones on energy balance. The endogenous ligands for MC4R include peptide agonists derived from processing of proopiomelanocortin and the antagonist Agouti-related peptide (AgRP). Wild-type MC4R has some basal (constitutive) activity. Naturally occurring and laboratory-generated mutations have been identified, which results in either increased or decreased basal activities. Impaired basal signaling has been suggested to be a cause of dysregulated energy homeostasis and early-onset obesity, although several constitutively active mutations have also been identified from obese patients. AgRP and several small-molecule antagonists have been shown to be inverse agonists in the Gs-cAMP pathway. However, in the extracellular signal-regulated kinase (ERK) 1/2 pathway, we showed that these inverse agonists are potent agonists, demonstrating convincingly that they are biased ligands. We also showed that some mutations that do not cause constitutive activation in the Gs-cAMP pathway cause constitutive activation in the ERK1/2 pathway, suggesting that they are biased receptors. The physiological and potential pathophysiological relevance of the biased constitutive signaling in MC4R and therapeutic potential remain to be investigated.
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Affiliation(s)
- Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, Alabama, USA.
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Abstract
The melanocortin 3 receptor (MC3R) regulates several physiological functions, including feed efficiency, nutrient partitioning, fasting response, natriuresis, and immune reactions. Naturally occurring mutations in the MC3R gene have been shown to be associated with increased adiposity and lung diseases such as tuberculosis and cystic fibrosis. The DRY motif at the cytoplasmic end of transmembrane domain 3 (TM3) and the second intracellular loop 2 (ICL2) are known to be important for receptor function in several G protein-coupled receptors (GPCRs). To gain a better understanding of the functions of this domain in MC3R, we performed alanine-scanning mutagenesis on 18 residues. We showed that alanine mutation of 11 residues reduced the maximal binding and maximal cAMP production stimulated by agonists. Mutation of two residues did not change maximal binding but resulted in impaired signaling in the Gs-cAMP pathway. Mutation of five residues impaired signaling in the ERK1/2 pathway. We have also shown that alanine mutants of seven residues that were defective in the cAMP pathway were not defective in the ERK1/2 pathway, demonstrating biased signaling. In summary, we demonstrated that the cytoplasmic end of TM3 and the ICL2 were critical for MC3R function. We also reported for the first time biased signaling in MC3R.
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Affiliation(s)
- Hui Huang
- Department of AnatomyPhysiology and Pharmacology, College of Veterinary Medicine, Auburn University, 212 Greene Hall, Auburn, Alabama 36849, USA
| | - Ya-Xiong Tao
- Department of AnatomyPhysiology and Pharmacology, College of Veterinary Medicine, Auburn University, 212 Greene Hall, Auburn, Alabama 36849, USA
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He S, Tao YX. Defect in MAPK signaling as a cause for monogenic obesity caused by inactivating mutations in the melanocortin-4 receptor gene. Int J Biol Sci 2014; 10:1128-37. [PMID: 25332687 PMCID: PMC4202029 DOI: 10.7150/ijbs.10359] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Accepted: 09/15/2014] [Indexed: 12/22/2022] Open
Abstract
The melanocortin-4 receptor (MC4R) is a Family A G protein-coupled receptor that plays an essential role in regulating energy homeostasis, including both energy intake and expenditure. Mutations leading to a reduced MC4R function confer a major gene effect for obesity. More than 170 distinct mutations have been identified in humans. In addition to the conventional Gs-stimulated cAMP pathway, the MC4R also activates MAPKs, especially ERK1/2. We also showed there is biased signaling in the two signaling pathways, with inverse agonists in the Gs-cAMP pathway acting as agonists for the ERK1/2 pathway. In the current study, we sought to determine whether defects in basal or agonist-induced ERK1/2 activation in MC4R mutants might potentially contribute to obesity pathogenesis in patients carrying these mutations. The constitutive and ligand-stimulated ERK1/2 activation were measured in wild type and 73 naturally occurring MC4R mutations. We showed that nineteen mutants had significantly decreased basal pERK1/2 level, and five Class V variants (where no functional defects have been identified previously), C40R, V50M, T112M, A154D and S295P, had impaired ligand-stimulated ERK1/2 activation. Our studies demonstrated for the first time that decreased basal or ligand-stimulated ERK1/2 signaling might contribute to obesity pathogenesis caused by mutations in the MC4R gene. We also observed biased signaling in 25 naturally occurring mutations in the Gs-cAMP and ERK1/2 pathways.
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Affiliation(s)
- Shan He
- 1. Department of Anatomy, Physiology, and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, Alabama 36849-5519, USA. ; 2. Key Laboratory of Freshwater Animal Breeding, Ministry of Agriculture, College of Fisheries, Huazhong Agricultural University, Hubei Collaborative Innovation Center for Freshwater Aquaculture, Wuhan, Hubei 430070, China
| | - Ya-Xiong Tao
- 1. Department of Anatomy, Physiology, and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, Alabama 36849-5519, USA
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Chakraborty R, Bhullar RP, Dakshinamurti S, Hwa J, Chelikani P. Inverse agonism of SQ 29,548 and Ramatroban on Thromboxane A2 receptor. PLoS One 2014; 9:e85937. [PMID: 24465800 PMCID: PMC3900440 DOI: 10.1371/journal.pone.0085937] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Accepted: 12/03/2013] [Indexed: 12/30/2022] Open
Abstract
G protein-coupled receptors (GPCRs) show some level of basal activity even in the absence of an agonist, a phenomenon referred to as constitutive activity. Such constitutive activity in GPCRs is known to have important pathophysiological roles in human disease. The thromboxane A2 receptor (TP) is a GPCR that promotes thrombosis in response to binding of the prostanoid, thromboxane A2. TP dysfunction is widely implicated in pathophysiological conditions such as bleeding disorders, hypertension and cardiovascular disease. Recently, we reported the characterization of a few constitutively active mutants (CAMs) in TP, including a genetic variant A160T. Using these CAMs as reporters, we now test the inverse agonist properties of known antagonists of TP, SQ 29,548, Ramatroban, L-670596 and Diclofenac, in HEK293T cells. Interestingly, SQ 29,548 reduced the basal activity of both, WT-TP and the CAMs while Ramatroban was able to reduce the basal activity of only the CAMs. Diclofenac and L-670596 showed no statistically significant reduction in basal activity of WT-TP or CAMs. To investigate the role of these compounds on human platelet function, we tested their effects on human megakaryocyte based system for platelet activation. Both SQ 29,548 and Ramatroban reduced the platelet hyperactivity of the A160T genetic variant. Taken together, our results suggest that SQ 29,548 and Ramatroban are inverse agonists for TP, whereas, L-670596 and Diclofenac are neutral antagonists. Our findings have important therapeutic applications in the treatment of TP mediated pathophysiological conditions.
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MESH Headings
- Amino Acid Substitution
- Blood Platelets/drug effects
- Blood Platelets/metabolism
- Bridged Bicyclo Compounds, Heterocyclic
- Calcium Signaling/drug effects
- Carbazoles/pharmacology
- Drug Evaluation, Preclinical
- Fatty Acids, Unsaturated
- HEK293 Cells
- Humans
- Hydrazines/pharmacology
- Inositol 1,4,5-Trisphosphate/metabolism
- Mutagenesis, Site-Directed
- Receptors, Thromboxane A2, Prostaglandin H2/agonists
- Receptors, Thromboxane A2, Prostaglandin H2/genetics
- Receptors, Thromboxane A2, Prostaglandin H2/metabolism
- Sulfonamides/pharmacology
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Affiliation(s)
- Raja Chakraborty
- Department of Oral Biology, University of Manitoba, Winnipeg, Manitoba, Canada
- Biology of Breathing Group- Manitoba Institute of Child Health, Winnipeg, Manitoba, Canada
| | - Rajinder P. Bhullar
- Department of Oral Biology, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Shyamala Dakshinamurti
- Departments of Pediatrics, Physiology, University of Manitoba, Winnipeg, Manitoba, Canada
- Biology of Breathing Group- Manitoba Institute of Child Health, Winnipeg, Manitoba, Canada
| | - John Hwa
- Department of Internal Medicine (Cardiology), Cardiovascular Research Center, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Prashen Chelikani
- Department of Oral Biology, University of Manitoba, Winnipeg, Manitoba, Canada
- Departments of Pediatrics, Physiology, University of Manitoba, Winnipeg, Manitoba, Canada
- Biology of Breathing Group- Manitoba Institute of Child Health, Winnipeg, Manitoba, Canada
- * E-mail:
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Tao YX, Huang H. Ipsen 5i is a Novel Potent Pharmacoperone for Intracellularly Retained Melanocortin-4 Receptor Mutants. Front Endocrinol (Lausanne) 2014; 5:131. [PMID: 25136332 PMCID: PMC4120685 DOI: 10.3389/fendo.2014.00131] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Accepted: 07/20/2014] [Indexed: 11/13/2022] Open
Abstract
Inactivating mutations of the melanocortin-4 receptor (MC4R) cause early-onset severe obesity in humans. Comprehensive functional studies show that most of the inactivating mutants of the MC4R are retained intracellularly. In the present study, we investigated whether a small molecule inverse agonist of the MC4R, Ipsen 5i, could act as a pharmacoperone and correct the cell surface expression and function of intracellularly retained mutant MC4Rs using multiple cell lines, including HEK293 and two neuronal cell lines. We showed that Ipsen 5i rescued the cell surface expression of all 11 intracellularly retained mutant MC4Rs studied herein in at least one cell line. Ipsen 5i functionally rescued seven mutants in all cell lines used. One mutant (Y157S) was functionally rescued in HEK293 cells but not in the two neuronal cell lines. Ipsen 5i increased cell surface expression of three mutants (S58C, G98R, and F261S) but did not affect signaling. Ipsen 5i had no effect on mutant MC4Rs with other defects (Δ88-92, D90N, I102S) or no defect (N274S). It also did not affect trafficking of a misrouted MC3R mutant (I335S). Cell impermeable peptide ligands of the MC4R or cell permeable small molecule ligand of δ opioid receptor could not rescue misrouted mutant MC4R. In summary, we demonstrated that Ipsen 5i was a novel potent pharmacoperone of the MC4R, correcting trafficking and signaling of a significant portion (73%) of intracellularly retained mutants. Additional studies are needed to demonstrate its in vivo efficacy.
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Affiliation(s)
- Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University , Auburn, AL , USA
| | - Hui Huang
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University , Auburn, AL , USA
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