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Gimenez LE, Martin C, Yu J, Hollanders C, Hernandez CC, Wu Y, Yao D, Han GW, Dahir NS, Wu L, Van der Poorten O, Lamouroux A, Mannes M, Zhao S, Tourwé D, Stevens RC, Cone RD, Ballet S. Novel Cocrystal Structures of Peptide Antagonists Bound to the Human Melanocortin Receptor 4 Unveil Unexplored Grounds for Structure-Based Drug Design. J Med Chem 2024; 67:2690-2711. [PMID: 38345933 DOI: 10.1021/acs.jmedchem.3c01822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2024]
Abstract
Melanocortin 4 receptor (MC4-R) antagonists are actively sought for treating cancer cachexia. We determined the structures of complexes with PG-934 and SBL-MC-31. These peptides differ from SHU9119 by substituting His6 with Pro6 and inserting Gly10 or Arg10. The structures revealed two subpockets at the TM7-TM1-TM2 domains, separated by N2857.36. Two peptide series based on the complexed peptides led to an antagonist activity and selectivity SAR study. Most ligands retained the SHU9119 potency, but several SBL-MC-31-derived peptides significantly enhanced MC4-R selectivity over MC1-R by 60- to 132-fold. We also investigated MC4-R coupling to the K+ channel, Kir7.1. Some peptides activated the channel, whereas others induced channel closure independently of G protein coupling. In cell culture studies, channel activation correlated with increased feeding, while a peptide with Kir7.1 inhibitory activity reduced eating. These results highlight the potential for targeting the MC4-R:Kir7.1 complex for treating positive and restrictive eating disorders.
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Affiliation(s)
- Luis E Gimenez
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Charlotte Martin
- Research Group of Organic Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, Brussels B-1050, Belgium
| | - Jing Yu
- iHuman Institute, ShanghaiTech University, Ren Building, 393 Middle Huaxia Road, Pudong, Shanghai 201210, China
| | - Charlie Hollanders
- Research Group of Organic Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, Brussels B-1050, Belgium
| | - Ciria C Hernandez
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Yiran Wu
- iHuman Institute, ShanghaiTech University, Ren Building, 393 Middle Huaxia Road, Pudong, Shanghai 201210, China
| | - Deqiang Yao
- iHuman Institute, ShanghaiTech University, Ren Building, 393 Middle Huaxia Road, Pudong, Shanghai 201210, China
| | - Gye Won Han
- Departments of Biological Sciences and Chemistry, Bridge Institute, USC Michelson Center for Convergent Bioscience, University of Southern California, Los Angeles, California 90089, United States
| | - Naima S Dahir
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, United States
- Department of Molecular and Integrative Physiology, School of Medicine, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Lijie Wu
- iHuman Institute, ShanghaiTech University, Ren Building, 393 Middle Huaxia Road, Pudong, Shanghai 201210, China
| | - Olivier Van der Poorten
- Research Group of Organic Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, Brussels B-1050, Belgium
| | - Arthur Lamouroux
- Research Group of Organic Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, Brussels B-1050, Belgium
| | - Morgane Mannes
- Research Group of Organic Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, Brussels B-1050, Belgium
| | - Suwen Zhao
- iHuman Institute, ShanghaiTech University, Ren Building, 393 Middle Huaxia Road, Pudong, Shanghai 201210, China
| | - Dirk Tourwé
- Research Group of Organic Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, Brussels B-1050, Belgium
| | - Raymond C Stevens
- iHuman Institute, ShanghaiTech University, Ren Building, 393 Middle Huaxia Road, Pudong, Shanghai 201210, China
| | - Roger D Cone
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, United States
- Department of Molecular and Integrative Physiology, School of Medicine, University of Michigan, Ann Arbor, Michigan 48109, United States
- Department of Molecular, Cellular, and Developmental Biology, College of Literature, Science, and the Arts, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Steven Ballet
- Research Group of Organic Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, Brussels B-1050, Belgium
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2
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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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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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Melanocortin-5 Receptor: Pharmacology and Its Regulation of Energy Metabolism. Int J Mol Sci 2022; 23:ijms23158727. [PMID: 35955857 PMCID: PMC9369360 DOI: 10.3390/ijms23158727] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2022] [Revised: 07/29/2022] [Accepted: 08/03/2022] [Indexed: 12/12/2022] Open
Abstract
As the most recent melanocortin receptor (MCR) identified, melanocortin-5 receptor (MC5R) has unique tissue expression patterns, pharmacological properties, and physiological functions. Different from the other four MCR subtypes, MC5R is widely distributed in both the central nervous system and peripheral tissues and is associated with multiple functions. MC5R in sebaceous and preputial glands regulates lipid production and sexual behavior, respectively. MC5R expressed in immune cells is involved in immunomodulation. Among the five MCRs, MC5R is the predominant subtype expressed in skeletal muscle and white adipose tissue, tissues critical for energy metabolism. Activated MC5R triggers lipid mobilization in adipocytes and glucose uptake in skeletal muscle. Therefore, MC5R is a potential target for treating patients with obesity and diabetes mellitus. Melanocortin-2 receptor accessory proteins can modulate the cell surface expression, dimerization, and pharmacology of MC5R. This minireview summarizes the molecular and pharmacological properties of MC5R and highlights the progress made on MC5R in energy metabolism. We poInt. out knowledge gaps that need to be explored in the future.
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Yan Y, Chi S, Liu G, Huang Y, Pan D, Jiang X. The c.612A>G mutation of MC4R affects constitutive activity and signaling in domestic goats. Anim Genet 2022; 53:665-675. [PMID: 35727803 DOI: 10.1111/age.13214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Revised: 03/14/2022] [Accepted: 04/22/2022] [Indexed: 12/01/2022]
Abstract
As a key gene for balancing energy and regulating feeding behavior, MC4R is relevant to the growth of ruminants. In this presentation, a highly conserved c.612A>G site in the coding sequence (CDS) of MC4R has been selected during a selective sweep analysis of 35 Yiling goats and 20 other wild goats. This site mutation results in an amino acid change from Ile to Met. The genotyping analysis of the c.612A>G site revealed that the A allele was the dominant allele in the domestic goat populations, while the wild goat individuals only had the G allele. For a better understanding of the biological significance of this site, we examined the protein localization and signal detection to explain the function of the two MC4R receptors. The results showed that both the M204 and I204 receptors can normally localize on the membrane. When stimulating the M204 type without α-MSH, it was defective at the level of basal cAMP and decreased significantly against the I204 type. In contrast, the signaling capacity of the M204 receptor was also lower than that of I204 under the stimulation of α-MSH. In the ERK1/2 pathway, stimulating MC4R with NDP-α-MSH, both the M204 and I204 receptors had normal pERK1/2 levels. These results indicate that the p.I204M mutation may change the function by damaging the constitutive activity and signaling, and thus may regulate goats' appetite. This study has potential application for rearing domestic goats.
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Affiliation(s)
- Yinan Yan
- Laboratory of Small Ruminant Genetics, Breeding and Reproduction, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, China.,Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction of the Ministry of Education, Wuhan, China
| | - Shaxuan Chi
- Laboratory of Small Ruminant Genetics, Breeding and Reproduction, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, China.,Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction of the Ministry of Education, Wuhan, China
| | - Guiqiong Liu
- Laboratory of Small Ruminant Genetics, Breeding and Reproduction, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, China.,Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction of the Ministry of Education, Wuhan, China
| | - Yongjie Huang
- Laboratory of Small Ruminant Genetics, Breeding and Reproduction, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, China.,Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction of the Ministry of Education, Wuhan, China
| | - Dongmei Pan
- Laboratory of Small Ruminant Genetics, Breeding and Reproduction, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, China.,Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction of the Ministry of Education, Wuhan, China
| | - Xunping Jiang
- Laboratory of Small Ruminant Genetics, Breeding and Reproduction, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, China.,Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction of the Ministry of Education, Wuhan, China
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6
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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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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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Israeli H, Degtjarik O, Fierro F, Chunilal V, Gill AK, Roth NJ, Botta J, Prabahar V, Peleg Y, Chan LF, Ben-Zvi D, McCormick PJ, Niv MY, Shalev-Benami M. Structure reveals the activation mechanism of the MC4 receptor to initiate satiation signaling. Science 2021; 372:808-814. [PMID: 33858992 DOI: 10.1126/science.abf7958] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Accepted: 04/08/2021] [Indexed: 12/18/2022]
Abstract
Obesity is a global epidemic that causes morbidity and impaired quality of life. The melanocortin receptor 4 (MC4R) is at the crux of appetite, energy homeostasis, and body-weight control in the central nervous system and is a prime target for anti-obesity drugs. Here, we present the cryo-electron microscopy (cryo-EM) structure of the human MC4R-Gs signaling complex bound to the agonist setmelanotide, a cyclic peptide recently approved for the treatment of obesity. The work reveals the mechanism of MC4R activation, highlighting a molecular switch that initiates satiation signaling. In addition, our findings indicate that calcium (Ca2+) is required for agonist, but not antagonist, efficacy. These results fill a gap in the understanding of MC4R activation and could guide the design of future weight-management drugs.
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Affiliation(s)
- Hadar Israeli
- Department of Chemical and Structural Biology, Weizmann Institute of Science, Rehovot 7610001, Israel
- Department of Developmental Biology and Cancer Research, The Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Oksana Degtjarik
- Department of Chemical and Structural Biology, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Fabrizio Fierro
- The Faculty of Agriculture, Food and Environment, The Hebrew University, Rehovot, Israel
- The Fritz Haber Center for Molecular Dynamics, The Hebrew University, Jerusalem, Israel
| | - Vidicha Chunilal
- Centre for Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine, Queen Mary, University of London, Charterhouse Square, London, UK
| | - Amandeep Kaur Gill
- Centre for Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine, Queen Mary, University of London, Charterhouse Square, London, UK
| | - Nicolas J Roth
- Centre for Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine, Queen Mary, University of London, Charterhouse Square, London, UK
| | - Joaquin Botta
- Centre for Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine, Queen Mary, University of London, Charterhouse Square, London, UK
| | - Vadivel Prabahar
- Department of Chemical and Structural Biology, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Yoav Peleg
- Structural Proteomics Unit (SPU), Life Sciences Core Facilities (LSCF), Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Li F Chan
- Centre for Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine, Queen Mary, University of London, Charterhouse Square, London, UK
| | - Danny Ben-Zvi
- Department of Developmental Biology and Cancer Research, The Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem, Israel.
| | - Peter J McCormick
- Centre for Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine, Queen Mary, University of London, Charterhouse Square, London, UK.
| | - Masha Y Niv
- The Faculty of Agriculture, Food and Environment, The Hebrew University, Rehovot, Israel.
- The Fritz Haber Center for Molecular Dynamics, The Hebrew University, Jerusalem, Israel
| | - Moran Shalev-Benami
- Department of Chemical and Structural Biology, Weizmann Institute of Science, Rehovot 7610001, Israel.
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9
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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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10
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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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11
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Tao YX. Molecular chaperones and G protein-coupled receptor maturation and pharmacology. Mol Cell Endocrinol 2020; 511:110862. [PMID: 32389798 DOI: 10.1016/j.mce.2020.110862] [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: 09/15/2019] [Revised: 05/04/2020] [Accepted: 05/05/2020] [Indexed: 12/15/2022]
Abstract
G protein-coupled receptors (GPCRs) are highly conserved versatile signaling molecules located at the plasma membrane that respond to diverse extracellular signals. They regulate almost all physiological processes in the vertebrates. About 35% of current drugs target these receptors. Mutations in these genes have been identified as causes of numerous diseases. The seven transmembrane domain structure of GPCRs implies that the folding of these transmembrane proteins is extremely complicated and difficult. Indeed, many wild type GPCRs are not folded optimally. The most common defect in genetic diseases caused by GPCR mutations is misfolding and failure to reach the plasma membrane where it functions. General molecular chaperones aid the folding of all proteins, including GPCRs, by preventing aggregation, promoting folding and disaggregating small aggregates. Some GPCRs need additional receptor-specific chaperones to assist their folding. Many of these receptor-specific chaperones interact with additional receptors and alter receptor pharmacology, expanding the understanding of these chaperone proteins.
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Affiliation(s)
- Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL, 36849-5519, USA.
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12
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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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Liu M, Min T, Zhang H, Liu Y, Wang Z. Pharmacological Characteristics of Porcine Orexin 2 Receptor and Mutants. Front Endocrinol (Lausanne) 2020; 11:132. [PMID: 32296386 PMCID: PMC7136461 DOI: 10.3389/fendo.2020.00132] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Accepted: 02/27/2020] [Indexed: 11/13/2022] Open
Abstract
Orexin receptors (OXRs) play a critical regulatory role in central control of food intake, maintenance of sleeping states, energy metabolism, and neuroendocrine homeostasis. However, most previous studies have focused on the sleep-promoting functions of OXRs in human beings, while their potential value in enhancing food intake for livestock breeding has not been fully exploited. In this study, we successfully cloned porcine orexin 2 receptor (pOX2R) complementary DNA and constructed four pOX2R mutants (P10S, P11T, V308I, and T401I) by site-directed mutagenesis, and their functional expressions were further confirmed through Western blotting analysis. Pharmacological characteristics of pOX2R and their mutants were further investigated. These results showed that the P10S, P11T, and T401I mutants had decreased cAMP signaling with orexin A, whereas only the P11T mutant decreased under the stimulation of orexin B. Besides, only P10S displayed a decreased calcium release in response to both orexin ligands. Importantly, these mutants exhibited decreased phosphorylation levels of ERK1/2, p38, and CREB to some degree compared with wild-type pOX2R. Collectively, these findings highlight the critical role of these mutations in pOX2R signaling and expand our understanding of molecular and pharmacological characterization of pOX2R.
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Affiliation(s)
- Min Liu
- College of Veterinary Medicine, Yangzhou University, Yangzhou, China
| | - Tianqi Min
- College of Veterinary Medicine, Yangzhou University, Yangzhou, China
| | - Haijie Zhang
- College of Veterinary Medicine, Yangzhou University, Yangzhou, China
| | - Yuan Liu
- College of Veterinary Medicine, Yangzhou University, Yangzhou, China
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, China
- Institute of Comparative Medicine, Yangzhou University, Yangzhou, China
- *Correspondence: Yuan Liu
| | - Zhiqiang Wang
- College of Veterinary Medicine, Yangzhou University, Yangzhou, China
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, China
- Zhiqiang Wang
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14
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Min T, Liu M, Zhang H, Liu Y, Wang Z. Molecular and pharmacological characterization of poultry (Gallus gallus, Anas platyrhynchos, Anser cygnoides domesticus) and pig (Sus scrofa domestica) melanocortin-5 receptors and their mutants. Gen Comp Endocrinol 2019; 283:113233. [PMID: 31356812 DOI: 10.1016/j.ygcen.2019.113233] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2019] [Revised: 07/08/2019] [Accepted: 07/25/2019] [Indexed: 12/25/2022]
Abstract
The melanocortin-5 receptor (MC5R) is a member of the G protein-coupled receptor superfamily that plays a critical role in lipid production, skeletal muscle fatty acid oxidation, and adipocyte lipolysis. Although multiple functions and important value of MC5R in human beings have been fully demonstrated, however, the potential molecular cloning, pharmacological characteristics and key amino acids in poultry and pig were still not fully understood. Herein, we successfully cloned MC5R genes from chicken (Gallus gallus, cMC5R), duck (Anas platyrhynchos, dMC5R), goose (Anser cygnoides domesticus, gMC5R) and pig (Sus scrofa domestica, pMC5R), and compared their genetic and protein difference with hMC5R through phylogenetic analysis and homology models. Besides, we constructed three alanine-substitution mutants for each of MC5Rs through homologous reorganization, including c/d/gMC5R-D119A/F254A/H257A and pMC5R-D204A/F339A/H342A. Subsequently, we focused our investigation on the pharmacological characterization of four wide-type MC5Rs and their mutants in HEK293T cells, including the intracellular cAMP generation and phosphorylation level of ERK1/2. The results showed that these mutants had decreased cAMP levels under the stimulation of ligands, in spite of enhanced basal activity for c/d/gF254A and pH342A, indicating their important roles in the location and activation of receptors. Notably, these MC5Rs and mutants displayed significant species-specific phenotypes in the activation of pERK1/2 with ligands, which was not completely consistent with hMC5R. These findings demonstrated that presence of interspecies differences for MC5Rs, particularly for the pERK1/2 pathway. Taken together, our study expands current knowledge about the molecular and pharmacological characterization of c/d/g/pMC5Rs, providing preliminary data for MC5R-targeted drug screening or genetic breeding of economic animals in the future.
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Affiliation(s)
- Tianqi Min
- College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China
| | - Min Liu
- College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China
| | - Haijie Zhang
- College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China
| | - Yuan Liu
- College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China; Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, Jiangsu, China; Institute of Comparative Medicine, Yangzhou University, Yangzhou, Jiangsu, China.
| | - Zhiqiang Wang
- College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China; Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, Jiangsu, China.
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15
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Gillyard T, Fowler K, Williams SY, Cone RD. Obesity-associated mutant melanocortin-4 receptors with normal Gα s coupling frequently exhibit other discoverable pharmacological and biochemical defects. J Neuroendocrinol 2019; 31:e12795. [PMID: 31529534 DOI: 10.1111/jne.12795] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Revised: 08/11/2019] [Accepted: 09/10/2019] [Indexed: 01/04/2023]
Abstract
Mutations in the melanocortin-4 receptor (MC4R) are the most common cause of early syndromic obesity known. Most of these mutations result in a loss of protein expression, α-melanocyte-stimulating hormone binding, receptor trafficking or coupling to the stimulatory G-protein, Gαs . However, approximately 26% of the obesity-associated mutations characterised to date exhibit none of these pharmacological defects. In the present study, we investigated seven of these apparently normal mutant MC4R in more detail and found that the majority (five of the seven) exhibit marked defects including defective binding of another endogenous melanocortin ligand, defective glycosylation, and defective recruitment of β-arrestin. These data provide support for two hypotheses: (i) that the majority of these rare, obesity-associated mutations are likely defective and causative of obesity and (ii) that β-arrestin recruitment is a valuable marker of normal MC4R function. Recent work has demonstrated a statistical correlation between the efficacy of β-arrestin recruitment to the MC4R and body mass index; however, the data reported here demonstrate both decreased and increased β-arrestin signalling in obesity-associated MC4R mutations.
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Affiliation(s)
- Taneisha Gillyard
- Department of Neuroscience and Pharmacology, Meharry Medical College, Nashville, TN, USA
| | - Katelyn Fowler
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
| | | | - Roger D Cone
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
- Department of Molecular and Integrative Physiology, School of Medicine, University of Michigan, Ann Arbor, MI, USA
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16
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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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17
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Moore BS, Mirshahi T. Genetic variants help define the role of the MC4R C-terminus in signaling and cell surface stability. Sci Rep 2018; 8:10397. [PMID: 29991773 PMCID: PMC6039487 DOI: 10.1038/s41598-018-28758-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Accepted: 06/26/2018] [Indexed: 11/09/2022] Open
Abstract
Screening 92,445 subjects in the Geisinger-Regeneron DiscovEHR cohort, we identified 5 patients heterozygous for nonsense mutations causing early terminations at Glu307 or Leu328 on the C-terminus of melanocortin 4 receptor (MC4R). Two Q307Ter carriers are severely obese (BMI > 40), while one is overweight (BMI > 25). One L328Ter carrier is overweight and the other is lean. Pedigree analysis for two Q307Ter carriers shows segregation of the variant with higher BMI. Functionally, MC4R(Q307Ter) eliminated receptor surface expression and signaling, while MC4R(L328Ter) functioned like the wild-type receptor. MC4R(Q307Ter) is therefore a loss of function (LOF) variant and the region between the two truncation sites identified in our patients is critical to MC4R function. Truncating MC4R at various C-terminal positions between these two variant sites, we find that cysteine318 sits at a critical junction for receptor trafficking and function. We show that MC4R is lipid modified at cysteine318 and cysteine319. Therefore, truncation early in the MC4R C-terminus results in haploinsufficiency in humans while truncation after the first lipid-modification site is well tolerated. MC4R haploinsufficiency clearly segregates with higher BMI; however, severe obesity is not fully penetrant even in MC4R LOF carriers, suggesting critical roles for environmental and lifestyle factors in MC4R monogenic obesity.
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Affiliation(s)
- Bryn S Moore
- Molecular and Functional Genomics, Weis Center for Research Geisinger Clinic, Danville, PA, United States
| | - Tooraj Mirshahi
- Molecular and Functional Genomics, Weis Center for Research Geisinger Clinic, Danville, PA, United States. .,Geisinger Obesity Institute, Geisinger Clinic, Danville, PA, United States.
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18
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Yang Y, Harmon CM. Molecular signatures of human melanocortin receptors for ligand binding and signaling. Biochim Biophys Acta Mol Basis Dis 2017; 1863:2436-2447. [PMID: 28478228 DOI: 10.1016/j.bbadis.2017.04.025] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2016] [Revised: 04/10/2017] [Accepted: 04/29/2017] [Indexed: 12/29/2022]
Abstract
Human melanocortin receptors (hMCRs) belong to the seven-transmembrane (TM) domain proteins. There are five hMCR subtypes and each of these receptor subtypes has different patterns of tissue expression and physiological function. The endogenous agonists for hMCRs are α-, β-, and γ-MSH and ACTH and endogenous antagonists are Agouti and AGRP which are the only known naturally occurring antagonists for the receptors. These peptides have their own profiles regarding the relative potency for specific hMCR subtype. Extensive studies have been performed to examine the molecular basis of the hMCRs for different ligand binding affinity and potency. Studies indicate that natural ligand α-MSH utilizes conserved amino acid residues for MCR specific binding (orthosteric binding) while synthetic ligands utilize non-conserved amino acid residues for receptor subtype specific binding (allosteric binding). ACTH is the only endogenous agonist for hMC2R and more amino acid residues at hMC2R are required for ACTH binding and signaling. HMCR computer modeling provides the detailed information of ligand and MCR interaction. This review provides the latest understanding of the molecular basis of the hMCRs for ligand binding and signaling. This article is part of a Special Issue entitled: Melanocortin Receptors - edited by Ya-Xiong Tao.
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Affiliation(s)
- Yingkui Yang
- Department of Surgery, State University of New York at Buffalo, Buffalo, NY 14203, United States.
| | - Carroll M Harmon
- Department of Surgery, State University of New York at Buffalo, Buffalo, NY 14203, United States
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19
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Huang H, Wang W, Tao YX. Pharmacological chaperones for the misfolded melanocortin-4 receptor associated with human obesity. Biochim Biophys Acta Mol Basis Dis 2017; 1863:2496-2507. [PMID: 28284973 DOI: 10.1016/j.bbadis.2017.03.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Revised: 02/28/2017] [Accepted: 03/01/2017] [Indexed: 01/01/2023]
Abstract
The melanocortin-4 receptor (MC4R) plays a vital role in regulating energy homeostasis. Mutations in the MC4R cause early-onset severe obesity. The majority of loss of function MC4R mutants are retained intracellularly, many of which are not terminally misfolded and can be stabilized and targeted to the plasma membrane by different chaperones. Some of the mutants might be functional once coaxed to the cell surface. Molecular chaperones and chemical chaperones correct the misfolding of some mutant MC4Rs. However, their therapeutic application is very limited due to their non-specific mechanism of action and, for chemical chaperone, high dosage needed to be effective. Several pharmacological chaperones have been identified for the MC4R and Ipsen 5i and Ipsen 17 are the most potent and efficacious. Here we provide a comprehensive review on how different approaches have been applied to rescue misfolded MC4R mutants. This article is part of a Special Issue entitled: Melanocortin Receptors - edited by Ya-Xiong Tao.
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Affiliation(s)
- Hui Huang
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, United States
| | - Wei Wang
- 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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20
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Manco L, Muc M, Padez C. Association study between near-MC4R variants and obesity-related variables in Portuguese young adults. GENE REPORTS 2016. [DOI: 10.1016/j.genrep.2016.09.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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21
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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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22
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Mutations in Melanocortin-3 Receptor Gene and Human Obesity. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2016; 140:97-129. [DOI: 10.1016/bs.pmbts.2016.01.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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23
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Wang ZQ, Huang JS, Zhou JH, Shi L, Jiang XF, Tao YX. Pharmacologic analyses of four chicken melanocortin-4 receptor mutations. Domest Anim Endocrinol 2016; 54:68-75. [PMID: 26521202 DOI: 10.1016/j.domaniend.2015.06.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Revised: 05/12/2015] [Accepted: 06/24/2015] [Indexed: 10/23/2022]
Abstract
The melanocortin-4 receptor (MC4R) is a critical regulator of mammalian food intake and energy expenditure, with receptor activation resulting in decreased food intake and increased energy expenditure. Recently, studies on role of MC4R in regulation of food intake have been extended to other species, such as chicken. Functional study of mutant MC4Rs is important in proving the causal link between MC4R mutation and production traits. Herein, we cloned chicken MC4R (cMC4R) complementary DNA and generated 4 mutant cMC4Rs (Q18H, G21R, S76L, and L299P) by site-directed mutagenesis and measured their expression by flow cytometry. Pharmacologic characteristics were analyzed with binding and signaling assays using 3 agonists. We showed that G21R had decreased cell surface and total expression (P < 0.05), whereas the other 3 mutants had similar total and cell surface expression levels as wild-type cMC4R. The 4 mutants had either decreased (Q18H, G21R, S76L; P < 0.05) or no (L299P) binding to radiolabeled [Nle(4), D-Phe(7)]-α-melanocyte-stimulating hormone (MSH). In signaling assays, Q18H was constitutively active. Q18H, G21R, and S76L had decreased responses to α-MSH stimulation (P < 0.05). L299P had decreased basal and ligand-stimulated signaling (P < 0.01). Nle(4), D-Phe(7)-MSH was the most potent agonist for cMC4R and therefore would be better suited for further in vivo studies. We conclude that the cloned cMC4R was a functional receptor and provided detailed functional data for these mutations, contributing to a better understanding of cMC4R variants associated with production traits.
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Affiliation(s)
- Z-Q Wang
- College of Veterinary Medicine, Yangzhou University, Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, Jiangsu 225009, People's Republic of China; Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA.
| | - J-S Huang
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA
| | - J-H Zhou
- College of Veterinary Medicine, Yangzhou University, Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, Jiangsu 225009, People's Republic of China
| | - L Shi
- College of Veterinary Medicine, Yangzhou University, Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, Jiangsu 225009, People's Republic of China
| | - X-F Jiang
- College of Veterinary Medicine, Yangzhou University, Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, 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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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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25
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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: 39] [Impact Index Per Article: 3.9] [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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Delhanty PJD, Bouw E, Huisman M, Vervenne RML, Themmen APN, van der Lely AJ, van den Akker ELT. Functional characterization of a new human melanocortin-4 receptor homozygous mutation (N72K) that is associated with early-onset obesity. Mol Biol Rep 2014; 41:7967-72. [PMID: 25163632 DOI: 10.1007/s11033-014-3691-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Accepted: 08/21/2014] [Indexed: 01/31/2023]
Abstract
The melanocortin 4 receptor (MC4R) is expressed in the hypothalamus and is essential for regulation of appetite and energy expenditure. MC4R dysfunction in humans causes hyperphagia, impaired satiety and obesity. We have identified a novel c.216C>A (N72 K) homozygous mutation in MC4R in a girl with severe obesity. The patient presented with early-onset obesity and hyperphagia indicating an effect of the homozygous mutation on her phenotype. In silico analyses indicate a damaging effect on receptor function, and the mutation is unusual in occurring in the first intra-cellular loop of the receptor. Site-directed mutagenesis was used to generate plasmid constructs expressing wild-type and mutant MC4R. These were transfected into HEK293 cells and assessed for cAMP responsiveness to α-MSH. Cells expressing N-terminal HA and C-terminal GFP-tagged MC4R were assessed by immunofluorescence confocal microscopy and flow cytometry for correct cell-surface localization. The maximal response of the mutant MC4R to α-MSH was decreased to 20 ± 1 % of the wild type receptor response, and the EC50 was increased from 16.5 ± 5.4 nM to 37.0 ± 8.3 nM. Localization of N- and C-terminally tagged MC4R by confocal microscopy and flow cytometry showed aberrant retention of the mutant receptor in the cytoplasm. Our data describe a rare homozygous inactivating mutation in the first intra-cellular loop of MC4R that markedly impairs its function and is associated with early-onset obesity and hyperphagia.
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Affiliation(s)
- Patric J D Delhanty
- Departments of Internal Medicine and Pediatric Endocrinology, Erasmus MC, Rotterdam, The Netherlands,
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Tao YX, Conn PM. Chaperoning G protein-coupled receptors: from cell biology to therapeutics. Endocr Rev 2014; 35:602-47. [PMID: 24661201 PMCID: PMC4105357 DOI: 10.1210/er.2013-1121] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Accepted: 03/14/2014] [Indexed: 12/13/2022]
Abstract
G protein-coupled receptors (GPCRs) are membrane proteins that traverse the plasma membrane seven times (hence, are also called 7TM receptors). The polytopic structure of GPCRs makes the folding of GPCRs difficult and complex. Indeed, many wild-type GPCRs are not folded optimally, and defects in folding are the most common cause of genetic diseases due to GPCR mutations. Both general and receptor-specific molecular chaperones aid the folding of GPCRs. Chemical chaperones have been shown to be able to correct the misfolding in mutant GPCRs, proving to be important tools for studying the structure-function relationship of GPCRs. However, their potential therapeutic value is very limited. Pharmacological chaperones (pharmacoperones) are potentially important novel therapeutics for treating genetic diseases caused by mutations in GPCR genes that resulted in misfolded mutant proteins. Pharmacoperones also increase cell surface expression of wild-type GPCRs; therefore, they could be used to treat diseases that do not harbor mutations in GPCRs. Recent studies have shown that indeed pharmacoperones work in both experimental animals and patients. High-throughput assays have been developed to identify new pharmacoperones that could be used as therapeutics for a number of endocrine and other genetic diseases.
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Affiliation(s)
- Ya-Xiong Tao
- Department of Anatomy, Physiology, and Pharmacology (Y.-X.T.), College of Veterinary Medicine, Auburn University, Auburn, Alabama 36849-5519; and Departments of Internal Medicine and Cell Biology (P.M.C.), Texas Tech University Health Science Center, Lubbock, Texas 79430-6252
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Huang H, Tao YX. A small molecule agonist THIQ as a novel pharmacoperone for intracellularly retained melanocortin-4 receptor mutants. Int J Biol Sci 2014; 10:817-24. [PMID: 25076858 PMCID: PMC4115193 DOI: 10.7150/ijbs.9625] [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] [Subscribe] [Scholar Register] [Received: 05/11/2014] [Accepted: 07/01/2014] [Indexed: 01/04/2023] Open
Abstract
Although mutations in the melanocortin-4 receptor (MC4R) gene cause severe early-onset obesity, we still do not have effective approaches to correct the defects of these mutations. Several antagonists have been identified as pharmacoperones of the MC4R whereas no agonist of the MC4R has been reported. In the present study, we investigated the effect of a small molecule agonist of the MC4R, THIQ, on the cell surface expression and signaling of ten intracellularly retained MC4R mutants using different cell lines. We showed that THIQ increased the cell surface expression of three mutants (N62S, C84R, and C271Y) and two of them (N62S and C84R) had increased signaling in HEK293 cells. Interestingly, THIQ increased the signaling of two other mutants (P78L and P260Q) without increasing their cell surface expression in HEK293 cells. In neuronal cells, THIQ exhibited a more potent effect, correcting the cell surface expression and signaling of seven mutants (N62S, I69R, P78L, C84R, W174C, P260Q, and C271Y). Other mutants were not rescued by THIQ. We also showed that THIQ did not rescue MC4R mutants defective in ligand binding or signaling or one intracellularly retained mutant of the melanocortin-3 receptor. In summary, we demonstrated that a small molecule agonist acted as a pharmacoperone of the MC4R rescuing the cell surface expression and signaling of some intracellularly retained MC4R mutants.
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Affiliation(s)
- Hui Huang
- 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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Moore BS, Mirshahi UL, Yost EA, Stepanchick AN, Bedrin MD, Styer AM, Jackson KK, Still CD, Breitwieser GE, Gerhard GS, Carey DJ, Mirshahi T. Long-term weight-loss in gastric bypass patients carrying melanocortin 4 receptor variants. PLoS One 2014; 9:e93629. [PMID: 24705671 PMCID: PMC3976318 DOI: 10.1371/journal.pone.0093629] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Accepted: 02/06/2014] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The melanocortin 4 receptor (MC4R) critically regulates feeding and satiety. Rare variants in MC4R are predominantly found in obese individuals. Though some rare variants in MC4R discovered in patients have defects in localization, ligand binding and signaling to cAMP, many have no recognized defects. SUBJECTS/METHODS In our cohort of 1433 obese subjects that underwent Roux-en-Y Gastric Bypass (RYGB) surgery, we found fifteen variants of MC4R. We matched rare variant carriers to patients with the MC4R reference alleles for gender, age, starting BMI and T2D to determine the variant effect on weight-loss post-RYGB. In vitro, we determined expression of mutant receptors by ELISA and western blot, and cAMP production by microscopy. RESULTS While carrying a rare MC4R allele is associated with obesity, carriers of rare variants exhibited comparable weight-loss after RYGB to non-carriers. However, subjects carrying three of these variants, V95I, I137T or L250Q, lost less weight after surgery. In vitro, the R305Q mutation caused a defect in cell surface expression while only the I137T and C326R mutations showed impaired cAMP signaling. Despite these apparent differences, there was no correlation between in vitro signaling and pre- or post-surgery clinical phenotype. CONCLUSIONS These data suggest that subtle differences in receptor signaling conferred by rare MC4R variants combined with additional factors predispose carriers to obesity. In the absence of complete MC4R deficiency, these differences can be overcome by the powerful weight-reducing effects of bariatric surgery. In a complex disorder such as obesity, genetic variants that cause subtle defects that have cumulative effects can be overcome after appropriate clinical intervention.
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Affiliation(s)
- Bryn S. Moore
- Weis Center for Research, Geisinger Clinic, Danville, Pennsylvania, United States of America
| | - Uyenlinh L. Mirshahi
- Weis Center for Research, Geisinger Clinic, Danville, Pennsylvania, United States of America
| | - Evan A. Yost
- Weis Center for Research, Geisinger Clinic, Danville, Pennsylvania, United States of America
| | - Ann N. Stepanchick
- Weis Center for Research, Geisinger Clinic, Danville, Pennsylvania, United States of America
| | - Michael D. Bedrin
- Weis Center for Research, Geisinger Clinic, Danville, Pennsylvania, United States of America
| | - Amanda M. Styer
- Weis Center for Research, Geisinger Clinic, Danville, Pennsylvania, United States of America
| | - Kathryn K. Jackson
- Weis Center for Research, Geisinger Clinic, Danville, Pennsylvania, United States of America
| | - Christopher D. Still
- Geisinger Obesity Institute, Geisinger Clinic, Danville, Pennsylvania, United States of America
| | - Gerda E. Breitwieser
- Weis Center for Research, Geisinger Clinic, Danville, Pennsylvania, United States of America
| | - Glenn S. Gerhard
- Weis Center for Research, Geisinger Clinic, Danville, Pennsylvania, United States of America
| | - David J. Carey
- Weis Center for Research, Geisinger Clinic, Danville, Pennsylvania, United States of America
| | - Tooraj Mirshahi
- Weis Center for Research, Geisinger Clinic, Danville, Pennsylvania, United States of America
- Geisinger Obesity Institute, Geisinger Clinic, Danville, Pennsylvania, United States of America
- * E-mail:
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Albuquerque D, Estévez MN, Víbora PB, Giralt PS, Balsera AM, Cortés PG, López MJ, Luego LM, Gervasini G, Hernández SB, Arroyo-Díez J, Vacas MA, Nóbrega C, Manco L, Rodríguez-López R. Novel Variants in theMC4RandLEPRGenes among Severely Obese Children from the Iberian Population. Ann Hum Genet 2014; 78:195-207. [DOI: 10.1111/ahg.12058] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Accepted: 01/21/2014] [Indexed: 12/12/2022]
Affiliation(s)
- David Albuquerque
- Research Centre for Anthropology and Health (CIAS); Department of Life Sciences; University of Coimbra; Portugal
| | | | - Pilar Beato Víbora
- Department of Dietician; Endocrinologist Service; Infanta Cristina Hospital; Badajoz Spain
| | - Plácida Sánchez Giralt
- Department of Dietician; Endocrinologist Service; Infanta Cristina Hospital; Badajoz Spain
| | | | - Pedro Gil Cortés
- Department of Dietician; Endocrinologist Service; Infanta Cristina Hospital; Badajoz Spain
| | - Mercedes Jiménez López
- Department of Medical & Surgical Therapeutics; Medical School; University of Extremadura; Badajoz Spain
| | - Luis Miguel Luego
- Department of Dietician; Endocrinologist Service; Infanta Cristina Hospital; Badajoz Spain
| | - Guillermo Gervasini
- Department of Medical & Surgical Therapeutics; Medical School; University of Extremadura; Badajoz Spain
| | | | | | | | - Clévio Nóbrega
- Center for Neurosciences & Cell Biology; University of Coimbra; Portugal
| | - Licínio Manco
- Research Centre for Anthropology and Health (CIAS); Department of Life Sciences; University of Coimbra; Portugal
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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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Rodrigues AR, Sousa D, Almeida H, Gouveia AM. Structural determinants regulating cell surface targeting of melanocortin receptors. J Mol Endocrinol 2013; 51:R23-32. [PMID: 23907004 DOI: 10.1530/jme-13-0055] [Citation(s) in RCA: 6] [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] [Indexed: 11/08/2022]
Abstract
Melanocortin receptors (MCRs) belong to the G-protein-coupled receptor family of transmembrane proteins. They recognize specific ligands named melanocortins that are mainly produced in the pituitary and hypothalamus. Newly synthesized MCRs at the endoplasmic reticulum are subjected to quality control mechanisms that screen for the correct structure, folding or processing, essential for their proper cell surface expression. Some motifs, located at the N- or C-terminus or even on transmembrane and in loop regions, have been implicated in these biological processes. This article reviews these specific domains and the role of accessory proteins and post-translation modifications in MCRs' targeting to cell surface. Additionally, promising approaches involving pharmacological stabilization of misfolded and misrouted mutant MCRs, which improve their forward transport, are reported. Understanding the MCRs' structural determinants fundamental for their proper cell surface integration is essential for correcting abnormalities found in some diseases.
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Affiliation(s)
- A R Rodrigues
- Department of Experimental Biology, Faculty of Medicine, University of Porto, Alameda Prof. Hernâni Monteiro, 4200-319 Porto, Portugal Instituto de Biologia Molecular e Celular (IBMC), University of Porto, Porto, Portugal IPATIMUP, Institute of Molecular Pathology and Immunology Faculty of Nutrition and Food Sciences, University of Porto, Porto, Portugal
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Mo XL, Tao YX. Activation of MAPK by inverse agonists in six naturally occurring constitutively active mutant human melanocortin-4 receptors. Biochim Biophys Acta Mol Basis Dis 2013; 1832:1939-48. [PMID: 23791567 DOI: 10.1016/j.bbadis.2013.06.006] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Revised: 05/17/2013] [Accepted: 06/05/2013] [Indexed: 01/14/2023]
Abstract
The melanocortin-4 receptor (MC4R) is a G protein-coupled receptor that plays an essential role in regulating energy homeostasis. Defects in MC4R are the most common monogenic form of obesity, with about 170 distinct mutations identified in human. In addition to the conventional Gs-stimulated adenylyl cyclase pathway, it has been recently demonstrated that MC4R also activates mitogen-activated protein kinases, extracellular signal-regulated kinases 1 and 2 (ERK1/2). Herein, we investigated the potential of four MC4R ligands that are inverse agonists at the Gs-cAMP signaling pathway, including agouti-related peptide (AgRP), MCL0020, Ipsen 5i and ML00253764, to regulate ERK1/2 activation (pERK1/2) in wild type and six naturally occurring constitutively active mutant (CAM) MC4Rs. We showed that these four inverse agonists acted as agonists for the ERK1/2 signaling cascade in wild type and CAM MC4Rs. Three mutants (P230L, L250Q and F280L) had significantly increased pERK1/2 level upon stimulation with all four inverse agonists, with maximal induction ranging from 1.6 to 4.2-fold. D146N had significantly increased pERK1/2 level upon stimulation with AgRP, MCL0020 or ML00253764, but not Ipsen 5i. The pERK1/2 levels of H76R and S127L were significantly increased only upon stimulation with AgRP or MCL0020. In summary, our studies demonstrated for the first time that MC4R inverse agonists at the Gs-cAMP pathway could serve as agonists in the MAPK pathway. These results suggested that there were multiple activation states of MC4R with ligand-specific and/or mutant-specific conformations capable of differentially coupling the MC4R to distinct signaling pathways.
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Affiliation(s)
- Xiu-Lei Mo
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL, USA
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Melanocortin-4 Receptor in Energy Homeostasis and Obesity Pathogenesis. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2013; 114:147-91. [DOI: 10.1016/b978-0-12-386933-3.00005-4] [Citation(s) in RCA: 115] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Deliard S, Panossian S, Mentch FD, Kim CE, Hou C, Frackelton EC, Bradfield JP, Glessner JT, Zhang H, Wang K, Sleiman PM, Chiavacci RM, Berkowitz RI, Hakonarson H, Zhao J, Grant SF. The missense variation landscape of FTO, MC4R, and TMEM18 in obese children of African Ancestry. Obesity (Silver Spring) 2013; 21:159-63. [PMID: 23505181 PMCID: PMC3605748 DOI: 10.1002/oby.20147] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Accepted: 10/18/2012] [Indexed: 11/11/2022]
Abstract
OBJECTIVE Common variation at the loci harboring fat mass and obesity (FTO), melanocortin receptor 4 (MC4R), and transmembrane protein 18 (TMEM18) is consistently reported as being statistically most strongly associated with obesity. Investigations if these loci also harbor rarer missense variants that confer substantially higher risk of common childhood obesity in African American (AA) children were conducted. DESIGN AND METHODS The exons of FTO, MC4R, and TMEM18 in an initial subset of our cohort were sequenced, that is, 200 obese (BMI ≥ 95 th percentile) and 200 lean AA children (BMI ≤ 5 th percentile). Any missense exonic variants that were uncovered went on to be further genotyped in a further 768 obese and 768 lean (BMI≤50th percentile) children of the same ethnicity. RESULTS A number of exonic variants were observed from our sequencing effort: seven in FTO, of which four were non-synonymous (A163T, G182A, M400V, and A405V), thirteen in MC4R, of which six were non-synonymous (V103I, N123S, S136A, F202L, N240S, and I251L), and four in TMEM18, of which two were non-synonymous (P2S and V113L). Follow-up genotyping of these missense variants revealed only one significant difference in allele frequency between cases and controls, namely with N240S in MC4R (Fisher's exact P = 0.0001). CONCLUSION In summary, moderately rare missense variants within the FTO, MC4R, and TMEM18 genes observed in our study did not confer risk of common childhood obesity in African Americans except for a degree of evidence for one known loss-of-function variant in MC4R.
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Affiliation(s)
- Sandra Deliard
- Division of Human Genetics, Department of Child and Adolescent Psychiatry, The Children's Hospital of Philadelphia
| | - Saarene Panossian
- Center for Applied Genomics, Department of Child and Adolescent Psychiatry, The Children's Hospital of Philadelphia
| | - Frank D. Mentch
- Center for Applied Genomics, Department of Child and Adolescent Psychiatry, The Children's Hospital of Philadelphia
| | - Cecilia E. Kim
- Center for Applied Genomics, Department of Child and Adolescent Psychiatry, The Children's Hospital of Philadelphia
| | - Cuiping Hou
- Center for Applied Genomics, Department of Child and Adolescent Psychiatry, The Children's Hospital of Philadelphia
| | - Edward C. Frackelton
- Center for Applied Genomics, Department of Child and Adolescent Psychiatry, The Children's Hospital of Philadelphia
| | - Jonathan P. Bradfield
- Center for Applied Genomics, Department of Child and Adolescent Psychiatry, The Children's Hospital of Philadelphia
| | - Joseph T. Glessner
- Center for Applied Genomics, Department of Child and Adolescent Psychiatry, The Children's Hospital of Philadelphia
| | - Haitao Zhang
- Center for Applied Genomics, Department of Child and Adolescent Psychiatry, The Children's Hospital of Philadelphia
| | - Kai Wang
- Center for Applied Genomics, Department of Child and Adolescent Psychiatry, The Children's Hospital of Philadelphia
| | - Patrick M.A. Sleiman
- Center for Applied Genomics, Department of Child and Adolescent Psychiatry, The Children's Hospital of Philadelphia
| | - Rosetta M. Chiavacci
- Center for Applied Genomics, Department of Child and Adolescent Psychiatry, The Children's Hospital of Philadelphia
| | - Robert I. Berkowitz
- Behavioral Health Center and Department of Child and Adolescent Psychiatry, The Children's Hospital of Philadelphia
- Center for Weight and Eating Disorders, Department of Psychiatry, University of Pennsylvania
| | - Hakon Hakonarson
- Division of Human Genetics, Department of Child and Adolescent Psychiatry, The Children's Hospital of Philadelphia
- Center for Applied Genomics, Department of Child and Adolescent Psychiatry, The Children's Hospital of Philadelphia
- Department of Pediatrics, University of Pennsylvania School of Medicine
| | - Jianhua Zhao
- Division of Human Genetics, Department of Child and Adolescent Psychiatry, The Children's Hospital of Philadelphia
| | - Struan F.A. Grant
- Division of Human Genetics, Department of Child and Adolescent Psychiatry, The Children's Hospital of Philadelphia
- Center for Applied Genomics, Department of Child and Adolescent Psychiatry, The Children's Hospital of Philadelphia
- Department of Pediatrics, University of Pennsylvania School of Medicine
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Granell S, Serra-Juhé C, Martos-Moreno GÁ, Díaz F, Pérez-Jurado LA, Baldini G, Argente J. A novel melanocortin-4 receptor mutation MC4R-P272L associated with severe obesity has increased propensity to be ubiquitinated in the ER in the face of correct folding. PLoS One 2012; 7:e50894. [PMID: 23251400 PMCID: PMC3520997 DOI: 10.1371/journal.pone.0050894] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Accepted: 10/26/2012] [Indexed: 11/28/2022] Open
Abstract
Heterozygous mutations in the melanocortin-4 receptor (MC4R) gene represent the most frequent cause of monogenic obesity in humans. MC4R mutation analysis in a cohort of 77 children with morbid obesity identified previously unreported heterozygous mutations (P272L, N74I) in two patients inherited from their obese mothers. A rare polymorphism (I251L, allelic frequency: 1/100) reported to protect against obesity was found in another obese patient. When expressed in neuronal cells, the cell surface abundance of wild-type MC4R and of the N74I and I251L variants and the cAMP generated by these receptors in response to exposure to the agonist, α-MSH, were not different. Conversely, MC4R P272L was retained in the endoplasmic reticulum and had reduced cell surface expression and signaling (by ≈3-fold). The chemical chaperone PBA, which promotes protein folding of wild-type MC4R, had minimal effects on the distribution and signaling of the P272L variant. In contrast, incubation with UBE-41, a specific inhibitor of ubiquitin activating enzyme E1, inhibited ubiquitination of MC4R P272L and increased its cell surface expression and signaling to similar levels as wild-type MC4R. UBE41 had much less profound effects on MC4R I316S, another obesity-linked MC4R variant trapped in the ER. These data suggest that P272L is retained in the ER by a propensity to be ubiquitinated in the face of correct folding, which is only minimally shared by MC4R I316S. Thus, studies that combine clinical screening of obese patients and investigation of the functional defects of the obesity-linked MC4R variants can identify specific ways to correct these defects and are the first steps towards personalized medicine.
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Affiliation(s)
- Susana Granell
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States of America
| | - Clara Serra-Juhé
- Unitat de Genètica, Universitat Pompeu Fabra, and Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Instituto de Salud Carlos III, Barcelona, Spain
| | - Gabriel Á. Martos-Moreno
- Department of Pediatric Endocrinology, Hospital Infantil Universitario Niño Jesús, Instituto de Investigación La Princesa, Madrid, Spain
| | - Francisca Díaz
- Department of Pediatric Endocrinology, Hospital Infantil Universitario Niño Jesús, Instituto de Investigación La Princesa, Madrid, Spain
| | - Luis A. Pérez-Jurado
- Unitat de Genètica, Universitat Pompeu Fabra, and Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Instituto de Salud Carlos III, Barcelona, Spain
| | - Giulia Baldini
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States of America
- * E-mail: (GB); (JA)
| | - Jesús Argente
- Department of Pediatric Endocrinology, Hospital Infantil Universitario Niño Jesús, Instituto de Investigación La Princesa, Madrid, Spain
- Department of Pediatrics, Universidad Autónoma de Madrid and Centro de Investigación Biomédica en Red de fisiopatología de la obesidad y nutrición (CIBERobn), Instituto de Salud Carlos III, Madrid, Spain
- * E-mail: (GB); (JA)
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Abstract
The melanocortin-4 receptor (MC4R) is a G protein-coupled receptor critical for maintaining energy homeostasis. Transmembrane domain 3 (TM3) of MC4R contains residues that were suggested to be essential in ligand binding and signaling. Several MC4R mutations in TM3 are associated with human obesity. To gain a better understanding of the functions of TM3, we analyzed the functions of 26 residues in TM3 using alanine-scanning mutagenesis. We showed that all mutants had normal cell-surface expression. Four mutants were defective in ligand binding and signaling and six mutants had normal ligand binding but impaired cAMP production. L140A had increased basal cAMP level. To further characterize the function of L140, we generated 17 additional L140 mutants. Fifteen L140 mutants had significantly decreased cell-surface expression, with L140R and L140V expressed normally. Ten L140 mutants had increased basal cAMP activities. Four L140 mutants were defective in ligand-stimulated cAMP generation. Interestingly, with the ERK1/2 pathway, we showed that nine constitutively active mutants had similar levels of basal pERK1/2 as that of WT, and two signaling defective mutants had similar levels of pERK1/2 as that of WT upon agonist stimulation, different from their cAMP signaling properties, suggesting biased signaling in these mutant receptors. In summary, we identified 13 residues in TM3 that were essential for ligand binding and/or signaling. Moreover, L140 was critical for locking MC4R in inactive conformation and several mutants showed biased signaling in cAMP and ERK1/2 signaling pathways.
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Affiliation(s)
- Xiu-Lei Mo
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, 212 Greene Hall, Auburn, Alabama 36849, USA
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Abstract
The melanocortin-4 receptor (MC4R) is a critical regulator of energy homeostasis and has emerged as a premier target for obesity treatment. Numerous mutations in transmembrane domain 6 (TM6) of MC4R resulting in functional alterations have been identified in obese patients. Several mutagenesis studies also provided some data suggesting the importance of this domain in receptor function. To gain a better understanding of the structure-function relationship of the receptor, we performed alanine-scanning mutagenesis in TM6 to determine the functions of side chains. Of the 31 residues, two were important for cell surface expression, five were indispensable for α-melanocyte-stimulating hormone (α-MSH) and β-MSH binding, and six were important for signaling in the Gs-cAMP-PKA pathway. H264A, targeted normally to the plasma membrane, was undetectable by competitive binding assay and severely defective in basal and stimulated cAMP production and ERK1/2 phosphorylation. Nine mutants had decreased basal cAMP signaling. Seven mutants were constitutively active in cAMP signaling and their basal activities could be inhibited by two MC4R inverse agonists, Ipsen 5i and ML00253764. Five mutants were also constitutively active in the MAPK pathway with enhanced basal ERK1/2 phosphorylation. In summary, our study provided comprehensive data on the structure-function relationship of the TM6 of MC4R. We identified residues that are important for cell surface expression, ligand binding, cAMP generation, and residues for maintaining the WT receptor in active conformation. We also reported constitutive activation of the MAPK pathway and biased signaling. These data will be useful for rationally designing MC4R agonists and antagonists for treatment of eating disorders.
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MESH Headings
- Blotting, Western
- Cell Line
- Cyclic AMP/metabolism
- Humans
- Imidazoles/pharmacology
- Immunohistochemistry
- Microscopy, Confocal
- Mutagenesis, Site-Directed
- Protein Binding/genetics
- Protein Binding/physiology
- Protein Structure, Tertiary/genetics
- Protein Structure, Tertiary/physiology
- Receptor, Melanocortin, Type 4/agonists
- Receptor, Melanocortin, Type 4/chemistry
- Receptor, Melanocortin, Type 4/genetics
- Receptor, Melanocortin, Type 4/metabolism
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Affiliation(s)
- Hui Huang
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, 212 Greene Hall, Auburn, Alabama 36849, USA
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41
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Valette M, Bellisle F, Carette C, Poitou C, Dubern B, Paradis G, Hercberg S, Muzard L, Clément K, Czernichow S. Eating behaviour in obese patients with melanocortin-4 receptor mutations: a literature review. Int J Obes (Lond) 2012; 37:1027-35. [PMID: 23147118 DOI: 10.1038/ijo.2012.169] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2012] [Revised: 09/07/2012] [Accepted: 09/09/2012] [Indexed: 11/09/2022]
Abstract
Melanocortin-4 receptor (MC4R) mutations are the most common known cause of monogenic obesity and an important contributor to polygenic obesity. MC4R mutations with partial or total loss of function, as well as the variant rs17782313 mapped near MC4R, are positively associated with obesity. MC4R is involved in the leptin-melanocortin signalling system, located in hypothalamic nuclei, that controls food intake via both anorexigenic or orexigenic signals. Impairment in this receptor might affect eating behaviours. Thus, in the case of MC4R mutation carriers, obesity could be related, at least partly, to inadequate control over eating behaviours. Many published studies address eating behaviours in MC4R mutation carriers. Most studies focus on binge eating disorder, whereas others examine various aspects of intake and motivation. Up to now, no evaluation of this literature has been performed. In this review, we examine the available literature on eating behaviours in carriers of MC4R mutations and variant rs17782313 near MC4R gene. We address binge eating disorder, bulimia nervosa, mealtime hyperphagia, snacking, psychological factors, satiety responsiveness and intake of energy and macro/micronutrient. In a small number of studies, MC4R mutations seem to impair eating behaviours or motivation, but no clear causal effects can be found in the balance of the evidence presented. Improvements in methodologies will be necessary to clarify the behavioural effects of MC4R mutations.
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Affiliation(s)
- M Valette
- Nutritional Epidemiology Research Unit-UMR U557 INSERM, Paris 13 University, CRNH-IdF, Bobigny, France
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Yang F, Tao YX. Functional characterization of nine novel naturally occurring human melanocortin-3 receptor mutations. Biochim Biophys Acta Mol Basis Dis 2012; 1822:1752-61. [PMID: 22884546 DOI: 10.1016/j.bbadis.2012.07.017] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2012] [Revised: 07/12/2012] [Accepted: 07/27/2012] [Indexed: 12/20/2022]
Abstract
The melanocortin-3 receptor (MC3R) is a member of family A rhodopsin-like G protein-coupled receptors. Mouse genetic studies suggested that MC3R and the related MC4R are non-redundant regulators of energy homeostasis. Lack of Mc3r leads to higher feed efficiency and fat mass. However, until now only a few MC3R mutations have been identified in humans and the role of MC3R in the pathogenesis of obesity was unclear. In the present study, we performed detailed functional studies on nine naturally occurring MC3R mutations recently reported. We found that all nine mutants had decreased cell surface expression. A260V, M275T, and L297V had decreased total expression whereas the other six mutants had normal total expression. Mutants S69C and T280S exhibited significant defects in ligand binding and signaling. The dramatic defects of T280S might be partially caused by decreased cell surface expression. In addition, we found mutants M134I and M275T had decreased maximal binding but displayed similar signaling properties as wild-type MC3R. All the other mutants had normal binding and signaling activities. Co-expression studies showed that all mutants except L297V did not affect wild-type MC3R signaling. Multiple mutations at T280 demonstrated the necessity of Thr for cell surface expression, ligand binding, and signaling. In summary, we provided detailed data of these novel human MC3R mutations leading to a better understanding of structure-function relationship of MC3R and the role of MC3R mutation in obesity.
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Affiliation(s)
- Fan Yang
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA
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