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Laiho L, Murray JF. The Multifaceted Melanocortin Receptors. Endocrinology 2022; 163:6608375. [PMID: 35700124 PMCID: PMC9214563 DOI: 10.1210/endocr/bqac083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Indexed: 12/05/2022]
Abstract
The 5 known melanocortin receptors (MCs) have established physiological roles. With the exception of MC2, these receptors can behave unpredictably, and since they are more widely expressed than their established roles would suggest, it is likely that they have other poorly characterized functions. The aim of this review is to discuss some of the less well-explored aspects of the 4 enigmatic members of this receptor family (MC1,3-5) and describe how these are multifaceted G protein-coupled receptors (GPCRs). These receptors appear to be promiscuous in that they bind several endogenous agonists (products of the proopiomelanocortin [POMC] gene) and antagonists but with inconsistent relative affinities and effects. We propose that this is a result of posttranslational modifications that determine receptor localization within nanodomains. Within each nanodomain there will be a variety of proteins, including ion channels, modifying proteins, and other GPCRs, that can interact with the MCs to alter the availability of receptor at the cell surface as well as the intracellular signaling resulting from receptor activation. Different combinations of interacting proteins and MCs may therefore give rise to the complex and inconsistent functional profiles reported for the MCs. For further progress in understanding this family, improved characterization of tissue-specific functions is required. Current evidence for interactions of these receptors with a range of partners, resulting in modulation of cell signaling, suggests that each should be studied within the full context of their interacting partners. The role of physiological status in determining this context also remains to be characterized.
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Affiliation(s)
- Linda Laiho
- Centre for Discovery Brain Sciences, School of Biomedical Sciences, University of Edinburgh, Edinburgh, UK
| | - Joanne Fiona Murray
- Correspondence: J. F. Murray, PhD, Centre for Discovery Brain Sciences, School of Biomedical Sciences, University of Edinburgh, Hugh Robson Building, 15 George Square, Edinburgh EH8 9DX, UK.
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2
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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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3
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Ji RL, Tao YX. Melanocortin-1 receptor mutations and pigmentation: Insights from large animals. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2022; 189:179-213. [PMID: 35595349 DOI: 10.1016/bs.pmbts.2022.03.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The melanocortin-1 receptor (MC1R) is a G protein-coupled receptor expressed in cutaneous and hair follicle melanocytes, and plays a central role in coat color determination in vertebrates. Numerous MC1R variants have been identified in diverse species. Some of these variants have been associated with specific hair and skin color phenotypes in humans as well as coat color in animals. Gain-of-function mutations of the MC1R gene cause dominant or partially dominant black/dark coat color, and loss-of-function mutations of the MC1R gene cause recessive or partially recessive red/yellow/pale coat color phenotypes. These have been well documented in a large number of mammals, including human, dog, cattle, horse, sheep, pig, and fox. Higher similarities between large mammals and humans makes them better models to understand pathogenesis of human diseases caused by MC1R mutations. High identities in MC1Rs and similar variants identified in both humans and large mammals also provide an opportunity for receptor structure and function study. In this review, we aim to summarize the naturally occurring mutations of MC1R in humans and large animals.
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Affiliation(s)
- Ren-Lei Ji
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL, United States
| | - Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL, United States.
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4
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Cheng W, Ndoka E, Maung JN, Pan W, Rupp AC, Rhodes CJ, Olson DP, Myers MG. NTS Prlh overcomes orexigenic stimuli and ameliorates dietary and genetic forms of obesity. Nat Commun 2021; 12:5175. [PMID: 34462445 PMCID: PMC8405610 DOI: 10.1038/s41467-021-25525-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Accepted: 08/11/2021] [Indexed: 11/09/2022] Open
Abstract
Calcitonin receptor (Calcr)-expressing neurons of the nucleus tractus solitarius (NTS; CalcrNTS cells) contribute to the long-term control of food intake and body weight. Here, we show that Prlh-expressing NTS (PrlhNTS) neurons represent a subset of CalcrNTS cells and that Prlh expression in these cells restrains body weight gain in the face of high fat diet challenge in mice. To understand the relationship of PrlhNTS cells to hypothalamic feeding circuits, we determined the ability of PrlhNTS-mediated signals to overcome enforced activation of AgRP neurons. We found that PrlhNTS neuron activation and Prlh overexpression in PrlhNTS cells abrogates AgRP neuron-driven hyperphagia and ameliorates the obesity of mice deficient in melanocortin signaling or leptin. Thus, enhancing Prlh-mediated neurotransmission from the NTS dampens hypothalamically-driven hyperphagia and obesity, demonstrating that NTS-mediated signals can override the effects of orexigenic hypothalamic signals on long-term energy balance. Calcitonin receptor-expressing neurons of the nucleus tractus solitarius contribute to long-term control of food intake and body weight. The authors show that a subset of these cells expresses Prlh and that enhancing Prlh-mediated neurotransmission from the NTS dampens hypothalamically-driven hyperphagia and obesity in mice.
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Affiliation(s)
- Wenwen Cheng
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA.
| | - Ermelinda Ndoka
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Jessica N Maung
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Warren Pan
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Alan C Rupp
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Christopher J Rhodes
- Research and Early Development, Cardiovascular, Renal, and Metabolism, BioPharmaceuticals R&D, AstraZeneca, Gaithersburg, MD, USA
| | - David P Olson
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA.,Division of Endocrinology, Department of Pediatrics, University of Michigan, Ann Arbor, MI, USA
| | - Martin G Myers
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA. .,Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA.
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5
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Lebrun B, Barbot M, Tonon MC, Prévot V, Leprince J, Troadec JD. Glial endozepines and energy balance: Old peptides with new tricks. Glia 2020; 69:1079-1093. [PMID: 33105065 DOI: 10.1002/glia.23927] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 10/09/2020] [Accepted: 10/09/2020] [Indexed: 12/12/2022]
Abstract
The contribution of neuroglial interactions to the regulation of energy balance has gained increasing acceptance in recent years. In this context, endozepines, endogenous analogs of benzodiazepine derived from diazepam-binding inhibitor, are now emerging as major players. Produced by glial cells (astrocytes and tanycytes), endozepines have been known for two decades to exert potent anorexigenic effects by acting at the hypothalamic level. However, it is only recently that their modes of action, including the mechanisms by which they modulate energy metabolism, have begun to be elucidated. The data available today are abundant, significant, and sometimes contradictory, revealing a much more complex regulation than initially expected. Several mechanisms of action of endozepines seem to coexist at the central level, particularly in the hypothalamus. The brainstem has also recently emerged as a potential site of action for endozepines. In addition to their central anorexigenic effects, endozepines may also display peripheral effects promoting orexigenic actions, adding to their complexity and raising yet more questions. In this review, we attempt to provide an overview of our current knowledge in this rapidly evolving field and to pinpoint questions that remain unanswered.
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Affiliation(s)
- Bruno Lebrun
- CNRS 7291, Laboratoire de Neurosciences Cognitives, Aix Marseille University, Marseille, France
| | - Manon Barbot
- CNRS 7291, Laboratoire de Neurosciences Cognitives, Aix Marseille University, Marseille, France
| | - Marie-Christine Tonon
- INSERM U1239, Laboratoire de Différenciation et Communication Neuronale et Neuroendocrine, Normandie Université, Rouen, France
| | - Vincent Prévot
- University of Lille, INSERM, CHU Lille, Development and Plasticity of the Neuroendocrine Brain, Lille Neuroscience and Cognition, UMR-S 1172, European Genomic Institute of Diabetes (EGID), Lille, France
| | - Jérôme Leprince
- INSERM U1239, Laboratoire de Différenciation et Communication Neuronale et Neuroendocrine, Normandie Université, Rouen, France
| | - Jean-Denis Troadec
- CNRS 7291, Laboratoire de Neurosciences Cognitives, Aix Marseille University, Marseille, France
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Lerma-Cabrera JM, Carvajal F, Garbutt JC, Navarro M, Thiele TE. The melanocortin system as a potential target for treating alcohol use disorders: A review of pre-clinical data. Brain Res 2019; 1730:146628. [PMID: 31891691 DOI: 10.1016/j.brainres.2019.146628] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Revised: 12/02/2019] [Accepted: 12/26/2019] [Indexed: 12/17/2022]
Abstract
The melanocortin (MC) system consists of neuropeptides that are cleaved from the polypeptide precursor proopiomelanocortin (POMC). In the brain, MC neuropeptides signal primarily through the MC-3 and MC-4 receptors, which are widely expressed throughout the brain. While the MC system has been largely studied for its role in food intake and body weight regulation, converging evidence has emerged over approximately the last 20-years showing that alcohol (ethanol), and other drugs of abuse influence the central MC system, and that manipulating MC receptor signalling modulates ethanol intake. Although there is divergent evidence, the wealth of data appears to suggest that activating MC signalling, primarily through the MC-4 receptor, is protective against excessive ethanol consumption. In the present review, we first describe the MC system and then detail how ethanol exposure and consumption alters central MC and MC-receptor expression and levels. This is followed by a review of the data, from pharmacological and genetic studies, which show that manipulations of MC receptor activity alter ethanol intake. We then briefly highlight studies implicating a role for the MC system in modulating neurobiological responses and intake of other drugs of abuse, including amphetamine, cocaine and opioids. Finally, we introduce relatively new observations that the drug, bupropion (BUP), a drug that activates central MC activity, significantly reduces ethanol intake in rodent models when administered alone and in combination with the non-selective opioid receptor antagonist, naltrexone. Phase II clinical trials are currently underway to assess the efficacy of BUP as a treatment for alcohol use disorders.
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Affiliation(s)
| | | | - James C Garbutt
- Department of Psychiatry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Montserrat Navarro
- Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Psychology & Neuroscience, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Todd E Thiele
- Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Psychology & Neuroscience, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
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Ayukawa K, Suzuki C, Ogasawara H, Kinoshita T, Furuno M, Suzuki G. Development of a High-Throughput Screening-Compatible Assay for Discovery of GPR3 Inverse Agonists Using a cAMP Biosensor. SLAS DISCOVERY 2019; 25:287-298. [PMID: 31516076 DOI: 10.1177/2472555219875101] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
While G-protein-coupled receptors (GPCRs) represent the largest class of cell surface proteins, there are ≥100 orphan GPCRs whose endogenous ligands are unknown. Accordingly, these could prove to be potential therapeutic targets for the pharmaceutical intervention of various diseases. Constitutively active orphan GPCRs are activated without ligands; thus, inverse agonists may be very useful pharmacological tools for inhibiting constitutive activity. However, in general, inverse agonist screening is considered more difficult to perform with high quality than antagonist screening, particularly due to the narrow assay window. We developed a high-throughput screening (HTS)-compatible assay to identify inverse agonists of GPR3. GPR3 is expressed in the central nervous system (CNS) and is known to be related to Alzheimer's disease and other CNS diseases. The GPR3 inducible cell line was established using T-REx 293 cells that stably expressed the tetracycline repressor protein, and the cAMP biosensor, GloSensor, was stably co-expressed. After optimization of the induction level of GPR3 and assay conditions, the GloSensor assay showed an approximately 20-fold signal-to-background ratio and high sensitivity. Using the HTS method, we successfully screened a library of hundreds of thousands of compounds for the inhibition of constitutive activity with good quality and excellent reproducibility. Finally, 35 compounds were identified as GPR3 selective inverse agonists. This inverse agonist screening approach using GloSensor in combination with the inducible expression of orphan GPCR indicates universal applicability to the search for inverse agonists of constitutively active orphan GPCRs.
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Affiliation(s)
- Kumiko Ayukawa
- Biological/Pharmacological Research Laboratories, Central Pharmaceutical Research Institute, Japan Tobacco Inc., Takatsuki, Osaka, Japan
| | - Chie Suzuki
- Biological/Pharmacological Research Laboratories, Central Pharmaceutical Research Institute, Japan Tobacco Inc., Takatsuki, Osaka, Japan
| | - Hiroyuki Ogasawara
- Pharmaceutical Frontier Research Laboratories, Central Pharmaceutical Research Institute, Japan Tobacco Inc., Kanazawa-ku, Yokohama, Kanagawa, Japan
| | - Tomomi Kinoshita
- Biological/Pharmacological Research Laboratories, Central Pharmaceutical Research Institute, Japan Tobacco Inc., Takatsuki, Osaka, Japan
| | - Masahiro Furuno
- Biological/Pharmacological Research Laboratories, Central Pharmaceutical Research Institute, Japan Tobacco Inc., Takatsuki, Osaka, Japan
| | - Gentaroh Suzuki
- Biological/Pharmacological Research Laboratories, Central Pharmaceutical Research Institute, Japan Tobacco Inc., Takatsuki, Osaka, Japan
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cAMP-mediated regulation of melanocyte genomic instability: A melanoma-preventive strategy. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2018; 115:247-295. [PMID: 30798934 DOI: 10.1016/bs.apcsb.2018.10.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Malignant melanoma of the skin is the leading cause of death from skin cancer and ranks fifth in cancer incidence among all cancers in the United States. While melanoma mortality has remained steady for the past several decades, melanoma incidence has been increasing, particularly among fair-skinned individuals. According to the American Cancer Society, nearly 10,000 people in the United States will die from melanoma this year. Individuals with dark skin complexion are protected damage generated by UV-light due to the high content of UV-blocking melanin pigment in their epidermis as well as better capacity for melanocytes to cope with UV damage. There is now ample evidence that suggests that the melanocortin 1 receptor (MC1R) is a major melanoma risk factor. Inherited loss-of-function mutations in MC1R are common in melanoma-prone persons, correlating with a less melanized skin complexion and poorer recovery from mutagenic photodamage. We and others are interested in the MC1R signaling pathway in melanocytes, its mechanisms of enhancing genomic stability and pharmacologic opportunities to reduce melanoma risk based on those insights. In this chapter, we review melanoma risk factors, the MC1R signaling pathway, and the relationship between MC1R signaling and DNA repair.
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Fleming KA, Ericson MD, Freeman KT, Adank DN, Lunzer MM, Wilber SL, Haskell-Luevano C. Structure-Activity Relationship Studies of a Macrocyclic AGRP-Mimetic Scaffold c[Pro-Arg-Phe-Phe-Asn-Ala-Phe-DPro] Yield Potent and Selective Melanocortin-4 Receptor Antagonists and Melanocortin-5 Receptor Inverse Agonists That Increase Food Intake in Mice. ACS Chem Neurosci 2018; 9:1141-1151. [PMID: 29363944 PMCID: PMC5955836 DOI: 10.1021/acschemneuro.7b00495] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The melanocortin system has five receptors, and antagonists of the central melanocortin receptors (MC3R, MC4R) are postulated to be viable therapeutics for disorders of negative energy balance such as anorexia, cachexia, and failure to thrive. Agouti-related protein (AGRP) is an antagonist of the MC3R and an antagonist/inverse agonist of the MC4R. Biophysical NMR-based structural studies have demonstrated that the active sequence of this hormone, Arg-Phe-Phe, is located on an exposed β-hairpin loop. It has previously been demonstrated that the macrocyclic octapeptide scaffold c[Pro1-Arg2-Phe3-Phe4-Asn5-Ala6-Phe7-DPro8] is 16-fold less potent than AGRP at the mouse MC4R (mMC4R). Herein it was hypothesized that the Phe7 position may be substituted to produce more potent and/or selective melanocortin receptor antagonist ligands based on this template. A 10-membered library was synthesized that substituted small (Gly), polar (Ser), acidic (Asp), basic (Lys), aliphatic (Leu, Nle, and Cha), and aromatic (Trp, Tyr, hPhe) amino acids to explore potential modifications at the Phe7 position. The most potent mMC4R antagonist contained a Nle7 substitution, was equipotent to the lead ligand 200-fold selective for the mMC4R over the mMC3R, and caused a significant increase in food intake when injected intrathecally into male mice. Three compounds possessed sigmoidal dose-response inverse agonist curves at the mMC5R, while the remaining seven decreased cAMP production from basal levels at a concentration of 100 μM. These findings will add to the knowledge base toward the development of potent and selective probes to study the role of the melanocortin system in diseases of negative energy balance and can be useful in the design of molecular probes to examine the physiological functions of the mMC5R.
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Affiliation(s)
- Katlyn A. Fleming
- University of Minnesota, Department of Medicinal Chemistry, Minneapolis, Minnesota 55455, United States
| | - Mark D. Ericson
- University of Minnesota, Department of Medicinal Chemistry, Minneapolis, Minnesota 55455, United States
| | - Katie T. Freeman
- University of Minnesota, Department of Medicinal Chemistry, Minneapolis, Minnesota 55455, United States
| | - Danielle N. Adank
- University of Minnesota, Department of Medicinal Chemistry, Minneapolis, Minnesota 55455, United States
| | - Mary M. Lunzer
- University of Minnesota, Department of Medicinal Chemistry, Minneapolis, Minnesota 55455, United States
| | - Stacey L. Wilber
- University of Minnesota, Department of Medicinal Chemistry, Minneapolis, Minnesota 55455, United States
| | - Carrie Haskell-Luevano
- University of Minnesota, Department of Medicinal Chemistry, Minneapolis, Minnesota 55455, United States
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10
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Li Z, Liu X, Zhang P, Han R, Sun G, Jiang R, Wang Y, Liu X, Li W, Kang X, Tian Y. Comparative transcriptome analysis of hypothalamus-regulated feed intake induced by exogenous visfatin in chicks. BMC Genomics 2018; 19:249. [PMID: 29642854 PMCID: PMC5896085 DOI: 10.1186/s12864-018-4644-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Accepted: 04/03/2018] [Indexed: 01/15/2023] Open
Abstract
Background The intracerebroventricular injection of visfatin increases feed intake. However, little is known about the molecular mechanism in chicks. This study was conducted to assess the effect of visfatin on the feeding behavior of chicks and the associated molecular mechanism. Results In response to the intraventricular injection of 40 ng and 400 ng visfatin, feed intake in chicks was significantly increased, and the concentrations of glucose, insulin, TG, HDL and LDL were significantly altered. Using RNA-seq, we identified DEGs in the chick hypothalamus at 60 min after injection with various doses of visfatin. In total, 325, 85 and 519 DEGs were identified in the treated chick hypothalamus in the LT vs C, HT vs C and LT vs HT comparisons, respectively. The changes in the expression profiles of DEGs, GO functional categories, KEGG pathways, and PPI networks by visfatin-mediated regulation of feed intake were analyzed. The DEGs were grouped into 8 clusters based on their expression patterns via K-mean clustering; there were 14 appetite-related DEGs enriched in the hormone activity GO term. The neuroactive ligand-receptor interaction pathway was the key pathway affected by visfatin. The PPI analysis of DEGs showed that POMC was a hub gene that interacted with the maximum number of nodes and ingestion-related pathways, including POMC, CRH, AgRP, NPY, TRH, VIP, NPYL, CGA and TSHB. Conclusion These common DEGs were enriched in the hormone activity GO term and the neuroactive ligand-receptor interaction pathway. Therefore, visfatin causes hyperphagia via the POMC/CRH and NPY/AgRP signaling pathways. These results provide valuable information about the molecular mechanisms of the regulation of food intake by visfatin. Electronic supplementary material The online version of this article (10.1186/s12864-018-4644-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Zhuanjian Li
- College of Animal Science and Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450002, China
| | - Xuelian Liu
- College of Animal Science and Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450002, China
| | - Panpan Zhang
- College of Animal Science and Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450002, China
| | - Ruili Han
- College of Animal Science and Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450002, China
| | - Guirong Sun
- College of Animal Science and Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450002, China
| | - Ruirui Jiang
- College of Animal Science and Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450002, China
| | - Yanbin Wang
- College of Animal Science and Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450002, China
| | - Xiaojun Liu
- College of Animal Science and Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450002, China
| | - Wenya Li
- College of Animal Science and Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450002, China
| | - Xiangtao Kang
- College of Animal Science and Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450002, China
| | - Yadong Tian
- College of Animal Science and Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450002, China.
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11
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Liu Y, Albrecht E, Schering L, Kuehn C, Yang R, Zhao Z, Maak S. Agouti Signaling Protein and Its Receptors as Potential Molecular Markers for Intramuscular and Body Fat Deposition in Cattle. Front Physiol 2018; 9:172. [PMID: 29559925 PMCID: PMC5845533 DOI: 10.3389/fphys.2018.00172] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Accepted: 02/20/2018] [Indexed: 11/13/2022] Open
Abstract
Transcriptome analyses of bovine muscle tissue differing in intramuscular fat (IMF) content identified agouti signaling protein (ASIP) as a promising candidate gene for fat deposition. The protein is secreted from adipocytes and may serve as a signaling molecule in cross-talk between adipocytes and muscle fibers or other cells. Known receptors for ASIP are the melanocortin receptors (e.g., MC4R) and attractin (ATRN). The present study was conducted to determine relationships between the expression of ASIP and its receptors in different bovine tissues with fat deposition. Adipose tissues, liver, and longissimus muscle tissue were collected from 246 F2-generation bulls (Charolais × Holstein cross) and gene expression was measured with RT-qPCR. During analysis of subcutaneous fat (SCF) of all bulls, 17 animals were identified with a transposon-derived transcript (Exon2C) inserted in the ASIP gene and dramatically increased ASIP mRNA levels. Significant correlations between normalized mRNA values of SCF and phenotypic traits related to fat deposition were found in bulls without Exon2C. Three retrospectively assigned groups [Exon2C, n = 17; high carcass fat (HCF), n = 20; low carcass fat (LCF), n = 20] were further analyzed to verify expression differences and elucidate molecular reasons. Expression of ASIP could be detected in isolated muscle fibers and adipocytes of Exon2C bulls in contrast to HCF and LCF bulls, indicating ectopic ASIP expression if the transposon is present. Among adipose tissues, highest ASIP mRNA levels were measured in SCF with significantly higher values in HCF compared to LCF bulls (1.6-fold, P < 0.05). However, the protein abundance was below the detection limit in all bulls. Potential ASIP receptors were detected in most investigated tissues. The expression of MC4R was higher and of ATRN was lower in several tissues of LCF compared to HCF bulls, whereas MC1R was not differentially expressed. Bulls of the Exon2C group had lower ATRN mRNA values than HCF and LCF bulls in perirenal fat (PF), but higher (P < 0.05) values in muscle. Receptors were also expressed in tissues where ASIP mRNA was not detected. Consequently, those tissues could be targets for ASIP if it circulates.
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Affiliation(s)
- Yinuo Liu
- College of Animal Science, Jilin University, Changchun, China.,Institute of Muscle Biology and Growth, Leibniz Institute for Farm Animal Biology, Dummerstorf, Germany
| | - Elke Albrecht
- Institute of Muscle Biology and Growth, Leibniz Institute for Farm Animal Biology, Dummerstorf, Germany
| | - Lisa Schering
- Institute of Muscle Biology and Growth, Leibniz Institute for Farm Animal Biology, Dummerstorf, Germany
| | - Christa Kuehn
- Institute for Genome Biology, Leibniz Institute for Farm Animal Biology, Dummerstorf, Germany
| | - Runjun Yang
- College of Animal Science, Jilin University, Changchun, China
| | - Zhihui Zhao
- College of Animal Science, Jilin University, Changchun, China
| | - Steffen Maak
- Institute of Muscle Biology and Growth, Leibniz Institute for Farm Animal Biology, Dummerstorf, Germany
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12
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Yang LK, Tao YX. Biased signaling at neural melanocortin receptors in regulation of energy homeostasis. Biochim Biophys Acta Mol Basis Dis 2017; 1863:2486-2495. [PMID: 28433713 DOI: 10.1016/j.bbadis.2017.04.010] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Revised: 04/09/2017] [Accepted: 04/10/2017] [Indexed: 12/15/2022]
Abstract
The global prevalence of obesity highlights the importance of understanding on regulation of energy homeostasis. The central melanocortin system is an important intersection connecting the neural pathways controlling satiety and energy expenditure to regulate energy homeostasis by sensing and integrating the signals of external stimuli. In this system, neural melanocortin receptors (MCRs), melanocortin-3 and -4 receptors (MC3R and MC4R), play crucial roles in the regulation of energy homeostasis. Recently, multiple intracellular signaling pathways and biased signaling at neural MCRs have been discovered, providing new insights into neural MCR signaling. This review attempts to summarize biased signaling including biased receptor mutants (both naturally occurring and lab-generated) and biased ligands at neural MCRs, and to provide a better understanding of obesity pathogenesis and new therapeutic implications for obesity treatment.
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Affiliation(s)
- Li-Kun Yang
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, United States
| | - Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, United States.
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13
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Orellana JA, Cerpa W, Carvajal MF, Lerma-Cabrera JM, Karahanian E, Osorio-Fuentealba C, Quintanilla RA. New Implications for the Melanocortin System in Alcohol Drinking Behavior in Adolescents: The Glial Dysfunction Hypothesis. Front Cell Neurosci 2017; 11:90. [PMID: 28424592 PMCID: PMC5380733 DOI: 10.3389/fncel.2017.00090] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Accepted: 03/15/2017] [Indexed: 12/12/2022] Open
Abstract
Alcohol dependence causes physical, social, and moral harms and currently represents an important public health concern. According to the World Health Organization (WHO), alcoholism is the third leading cause of death worldwide, after tobacco consumption and hypertension. Recent epidemiologic studies have shown a growing trend in alcohol abuse among adolescents, characterized by the consumption of large doses of alcohol over a short time period. Since brain development is an ongoing process during adolescence, short- and long-term brain damage associated with drinking behavior could lead to serious consequences for health and wellbeing. Accumulating evidence indicates that alcohol impairs the function of different components of the melanocortin system, a major player involved in the consolidation of addictive behaviors during adolescence and adulthood. Here, we hypothesize the possible implications of melanocortins and glial cells in the onset and progression of alcohol addiction. In particular, we propose that alcohol-induced decrease in α-MSH levels may trigger a cascade of glial inflammatory pathways that culminate in altered gliotransmission in the ventral tegmental area and nucleus accumbens (NAc). The latter might potentiate dopaminergic drive in the NAc, contributing to increase the vulnerability to alcohol dependence and addiction in the adolescence and adulthood.
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Affiliation(s)
- Juan A Orellana
- Centro de Investigación y Estudio del Consumo de Alcohol en AdolescentesSantiago, Chile.,Laboratorio de Neurociencias, Departamento de Neurología, Escuela de Medicina, Facultad de Medicina, Pontificia Universidad Católica de ChileSantiago, Chile
| | - Waldo Cerpa
- Centro de Investigación y Estudio del Consumo de Alcohol en AdolescentesSantiago, Chile.,Laboratorio de Función y Patología Neuronal, Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de ChileSantiago, Chile
| | - Maria F Carvajal
- Centro de Investigación y Estudio del Consumo de Alcohol en AdolescentesSantiago, Chile.,Unidad de Neurociencia, Centro de Investigación Biomédica, Universidad Autónoma de ChileSantiago, Chile
| | - José M Lerma-Cabrera
- Centro de Investigación y Estudio del Consumo de Alcohol en AdolescentesSantiago, Chile.,Unidad de Neurociencia, Centro de Investigación Biomédica, Universidad Autónoma de ChileSantiago, Chile
| | - Eduardo Karahanian
- Centro de Investigación y Estudio del Consumo de Alcohol en AdolescentesSantiago, Chile.,Unidad de Neurociencia, Centro de Investigación Biomédica, Universidad Autónoma de ChileSantiago, Chile
| | - Cesar Osorio-Fuentealba
- Centro de Investigación y Estudio del Consumo de Alcohol en AdolescentesSantiago, Chile.,Facultad de Kinesiología, Artes y Educación Física, Universidad Metropolitana de Ciencias de la EducaciónSantiago, Chile
| | - Rodrigo A Quintanilla
- Centro de Investigación y Estudio del Consumo de Alcohol en AdolescentesSantiago, Chile.,Laboratory of Neurodegenerative Diseases, Universidad Autónoma de ChileSantiago, Chile
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14
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Palomino R, Lee HW, Millhauser GL. The agouti-related peptide binds heparan sulfate through segments critical for its orexigenic effects. J Biol Chem 2017; 292:7651-7661. [PMID: 28264929 DOI: 10.1074/jbc.m116.772822] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Revised: 03/03/2017] [Indexed: 12/20/2022] Open
Abstract
Syndecans potently modulate agouti-related peptide (AgRP) signaling in the central melanocortin system. Through heparan sulfate moieties, syndecans are thought to anchor AgRP near its receptor, enhancing its orexigenic effects. Original work proposed that the N-terminal domain of AgRP facilitates this interaction. However, this is not compatible with evidence that this domain is posttranslationally cleaved. Addressing this long-standing incongruity, we used calorimetry and magnetic resonance to probe interactions of AgRP peptides with glycosaminoglycans, including heparan sulfate. We show that mature, cleaved, C-terminal AgRP, not the N-terminal domain, binds heparan sulfate. NMR shows that the binding site consists of regions distinct from the melanocortin receptor-binding site. Using a library of designed AgRP variants, we find that the strength of the syndecan interaction perfectly tracks orexigenic action. Our data provide compelling evidence that AgRP is a heparan sulfate-binding protein and localizes critical regions in the AgRP structure required for this interaction.
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Affiliation(s)
- Rafael Palomino
- From the Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064
| | - Hsiau-Wei Lee
- From the Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064
| | - Glenn L Millhauser
- From the Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064
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15
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Agosti F, Cordisco Gonzalez S, Martinez Damonte V, Tolosa MJ, Di Siervi N, Schioth HB, Davio C, Perello M, Raingo J. Melanocortin 4 receptor constitutive activity inhibits L-type voltage-gated calcium channels in neurons. Neuroscience 2017; 346:102-112. [PMID: 28093215 DOI: 10.1016/j.neuroscience.2017.01.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Revised: 12/16/2016] [Accepted: 01/05/2017] [Indexed: 11/19/2022]
Abstract
The melanocortin 4 receptor (MC4R) is a G protein-coupled receptor (GPCR) that is expressed in several brain nuclei playing a crucial role in the regulation of energy balance controlling the homeostasis of the organism. It displays both agonist-evoked and constitutive activity, and moreover, it can couple to different G proteins. Most of the research on MC4R has been focused on agonist-induced activity, while the molecular and cellular basis of MC4R constitutive activity remains scarcely studied. We have previously shown that neuronal N-type voltage-gated calcium channels (CaV2.2) are inhibited by MC4R agonist-dependent activation, while the CaV subtypes that carry L- and P/Q-type current are not. Here, we tested the hypothesis that MC4R constitutive activity can affect CaV, with focus on the channel subtypes that can control transcriptional activity coupled to depolarization (L-type, CaV1.2/1.3) and neurotransmitter release (N- and P/Q-type, CaV2.2 and CaV2.1). We found that MC4R constitutive activity inhibits specifically CaV1.2/1.3 and CaV2.1 subtypes of CaV. We also explored the signaling pathways mediating this inhibition, and thus propose that agonist-dependent and basal MC4R activation modes signal differentially through Gs and Gi/o pathways to impact on different CaV subtypes. In addition, we found that chronic incubation with MC4R endogenous inverse agonist, agouti and agouti-related peptide (AgRP), occludes CaV inhibition in a cell line and in amygdaloid complex cultured neurons as well. Thus, we define new mechanisms of control of the main mediators of depolarization-induced calcium entry into neurons by a GPCR that displays constitutive activity.
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Affiliation(s)
- F Agosti
- Electrophysiology Laboratory, Multidisciplinary Institute of Cell Biology (IMBICE) Universidad de La Plata-Consejo Nacional de Investigaciones Científicas y Técnicas, CONICET, and Comision de Investigaciones de la Provincia de buenos Aires (CIC), La Plata, Buenos Aires, Argentina
| | - S Cordisco Gonzalez
- Electrophysiology Laboratory, Multidisciplinary Institute of Cell Biology (IMBICE) Universidad de La Plata-Consejo Nacional de Investigaciones Científicas y Técnicas, CONICET, and Comision de Investigaciones de la Provincia de buenos Aires (CIC), La Plata, Buenos Aires, Argentina
| | - V Martinez Damonte
- Electrophysiology Laboratory, Multidisciplinary Institute of Cell Biology (IMBICE) Universidad de La Plata-Consejo Nacional de Investigaciones Científicas y Técnicas, CONICET, and Comision de Investigaciones de la Provincia de buenos Aires (CIC), La Plata, Buenos Aires, Argentina
| | - M J Tolosa
- Electrophysiology Laboratory, Multidisciplinary Institute of Cell Biology (IMBICE) Universidad de La Plata-Consejo Nacional de Investigaciones Científicas y Técnicas, CONICET, and Comision de Investigaciones de la Provincia de buenos Aires (CIC), La Plata, Buenos Aires, Argentina
| | - N Di Siervi
- Instituto de Investigaciones Farmacológicas, ININFA, Universidad de Buenos Aires-Consejo Nacional de Investigaciones Científicas y Técnicas, CONICET, Buenos Aires, Argentina
| | - H B Schioth
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Uppsala, Sweden
| | - C Davio
- Instituto de Investigaciones Farmacológicas, ININFA, Universidad de Buenos Aires-Consejo Nacional de Investigaciones Científicas y Técnicas, CONICET, Buenos Aires, Argentina
| | - M Perello
- Neurophysiology Laboratory, Multidisciplinary Institute of Cell Biology (IMBICE) Universidad de La Plata-Consejo Nacional de Investigaciones Científicas y Técnicas, CONICET, and Comision de Investigaciones de la Provincia de buenos Aires (CIC), La Plata, Buenos Aires, Argentina
| | - J Raingo
- Electrophysiology Laboratory, Multidisciplinary Institute of Cell Biology (IMBICE) Universidad de La Plata-Consejo Nacional de Investigaciones Científicas y Técnicas, CONICET, and Comision de Investigaciones de la Provincia de buenos Aires (CIC), La Plata, Buenos Aires, Argentina
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16
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Rabaglino MB, Chang EI, Richards EM, James MO, Keller-Wood M, Wood CE. Genomic Effect of Triclosan on the Fetal Hypothalamus: Evidence for Altered Neuropeptide Regulation. Endocrinology 2016; 157:2686-97. [PMID: 27145008 PMCID: PMC4929550 DOI: 10.1210/en.2016-1080] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Triclosan (TCS), an antibacterial compound commonly added to personal care products, could be an endocrine disruptor at low doses. Although TCS has been shown to alter fetal physiology, its effects in the developing fetal brain are unknown. We hypothesize that exposure to TCS during fetal life could affect fetal hypothalamic gene expression. The objective of this study was to use transcriptomics and systems analysis to identify significantly altered biological processes in the late gestation ovine fetal hypothalamus after direct or indirect exposure to low doses of TCS. For direct TCS exposure, chronically catheterized late gestation fetal sheep were infused with vehicle (n = 4) or TCS (250 μg/d; n = 4) iv. For indirect TCS exposure, TCS (100 μg/kg · d; n = 3) or vehicle (n = 3) was infused into the maternal circulation. Fetal hypothalami were collected after 2 days of infusion, and gene expression was measured through microarray. Hierarchical clustering of all samples according to gene expression profiles showed that samples from the TCS-treated animals clustered apart from the controls. Gene set enrichment analysis revealed that fetal hypothalamic genes stimulated by maternal and fetal TCS infusion were significantly enriching for cell cycle, reproductive process, and feeding behavior, whereas the inhibited genes were significantly enriching for chromatin modification and metabolism of steroids, lipoproteins, fatty acids, and glucose (P < .05). In conclusion, short-term infusion of TCS induces vigorous changes in the fetal hypothalamic transcriptomics, which are mainly related to food intake pathways and metabolism. If these changes persist to postnatal life, they could result in adverse consequences in adulthood.
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Affiliation(s)
- Maria Belen Rabaglino
- Centro de Excelencia en Procesos y Productos de Córdoba (M.B.R.), National Scientific and Technical Research Council, Córdoba, Argentina X5164; Department of Physiology and Functional Genomics (E.I.C., C.E.W.), College of Medicine, University of Florida, Gainesville, Florida 32610; and Departments of Medicinal Chemistry (M.O.J.) and Pharmacodynamics (E.M.R., M.K.-W.), College of Pharmacy, University of Florida, Gainesville, Florida 32610
| | - Eileen I Chang
- Centro de Excelencia en Procesos y Productos de Córdoba (M.B.R.), National Scientific and Technical Research Council, Córdoba, Argentina X5164; Department of Physiology and Functional Genomics (E.I.C., C.E.W.), College of Medicine, University of Florida, Gainesville, Florida 32610; and Departments of Medicinal Chemistry (M.O.J.) and Pharmacodynamics (E.M.R., M.K.-W.), College of Pharmacy, University of Florida, Gainesville, Florida 32610
| | - Elaine M Richards
- Centro de Excelencia en Procesos y Productos de Córdoba (M.B.R.), National Scientific and Technical Research Council, Córdoba, Argentina X5164; Department of Physiology and Functional Genomics (E.I.C., C.E.W.), College of Medicine, University of Florida, Gainesville, Florida 32610; and Departments of Medicinal Chemistry (M.O.J.) and Pharmacodynamics (E.M.R., M.K.-W.), College of Pharmacy, University of Florida, Gainesville, Florida 32610
| | - Margaret O James
- Centro de Excelencia en Procesos y Productos de Córdoba (M.B.R.), National Scientific and Technical Research Council, Córdoba, Argentina X5164; Department of Physiology and Functional Genomics (E.I.C., C.E.W.), College of Medicine, University of Florida, Gainesville, Florida 32610; and Departments of Medicinal Chemistry (M.O.J.) and Pharmacodynamics (E.M.R., M.K.-W.), College of Pharmacy, University of Florida, Gainesville, Florida 32610
| | - Maureen Keller-Wood
- Centro de Excelencia en Procesos y Productos de Córdoba (M.B.R.), National Scientific and Technical Research Council, Córdoba, Argentina X5164; Department of Physiology and Functional Genomics (E.I.C., C.E.W.), College of Medicine, University of Florida, Gainesville, Florida 32610; and Departments of Medicinal Chemistry (M.O.J.) and Pharmacodynamics (E.M.R., M.K.-W.), College of Pharmacy, University of Florida, Gainesville, Florida 32610
| | - Charles E Wood
- Centro de Excelencia en Procesos y Productos de Córdoba (M.B.R.), National Scientific and Technical Research Council, Córdoba, Argentina X5164; Department of Physiology and Functional Genomics (E.I.C., C.E.W.), College of Medicine, University of Florida, Gainesville, Florida 32610; and Departments of Medicinal Chemistry (M.O.J.) and Pharmacodynamics (E.M.R., M.K.-W.), College of Pharmacy, University of Florida, Gainesville, Florida 32610
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17
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Anderson EJP, Çakir I, Carrington SJ, Cone RD, Ghamari-Langroudi M, Gillyard T, Gimenez LE, Litt MJ. 60 YEARS OF POMC: Regulation of feeding and energy homeostasis by α-MSH. J Mol Endocrinol 2016; 56:T157-74. [PMID: 26939593 PMCID: PMC5027135 DOI: 10.1530/jme-16-0014] [Citation(s) in RCA: 94] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Accepted: 03/01/2016] [Indexed: 12/20/2022]
Abstract
The melanocortin peptides derived from pro-opiomelanocortin (POMC) were originally understood in terms of the biological actions of α-melanocyte-stimulating hormone (α-MSH) on pigmentation and adrenocorticotrophic hormone on adrenocortical glucocorticoid production. However, the discovery of POMC mRNA and melanocortin peptides in the CNS generated activities directed at understanding the direct biological actions of melanocortins in the brain. Ultimately, discovery of unique melanocortin receptors expressed in the CNS, the melanocortin-3 (MC3R) and melanocortin-4 (MC4R) receptors, led to the development of pharmacological tools and genetic models leading to the demonstration that the central melanocortin system plays a critical role in the regulation of energy homeostasis. Indeed, mutations in MC4R are now known to be the most common cause of early onset syndromic obesity, accounting for 2-5% of all cases. This review discusses the history of these discoveries, as well as the latest work attempting to understand the molecular and cellular basis of regulation of feeding and energy homeostasis by the predominant melanocortin peptide in the CNS, α-MSH.
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Affiliation(s)
- Erica J P Anderson
- Department of Molecular Physiology and BiophysicsVanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Isin Çakir
- Department of Molecular Physiology and BiophysicsVanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Sheridan J Carrington
- Department of Molecular Physiology and BiophysicsVanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Roger D Cone
- Department of Molecular Physiology and BiophysicsVanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Masoud Ghamari-Langroudi
- Department of Molecular Physiology and BiophysicsVanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Taneisha Gillyard
- Department of Molecular Physiology and BiophysicsVanderbilt University School of Medicine, Nashville, Tennessee, USA Meharry Medical CollegeDepartment of Neuroscience and Pharmacology, Nashville, Tennessee, USA
| | - Luis E Gimenez
- Department of Molecular Physiology and BiophysicsVanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Michael J Litt
- Department of Molecular Physiology and BiophysicsVanderbilt University School of Medicine, Nashville, Tennessee, USA
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18
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Lanfray D, Caron A, Roy MC, Laplante M, Morin F, Leprince J, Tonon MC, Richard D. Involvement of the Acyl-CoA binding domain containing 7 in the control of food intake and energy expenditure in mice. eLife 2016; 5. [PMID: 26880548 PMCID: PMC4821795 DOI: 10.7554/elife.11742] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2015] [Accepted: 02/14/2016] [Indexed: 11/28/2022] Open
Abstract
Acyl-CoA binding domain-containing 7 (Acbd7) is a paralog gene of the diazepam-binding inhibitor/Acyl-CoA binding protein in which single nucleotide polymorphism has recently been associated with obesity in humans. In this report, we provide converging evidence indicating that a splice variant isoform of the Acbd7 mRNA is expressed and translated by some POMC and GABAergic-neurons in the hypothalamic arcuate nucleus (ARC). We have demonstrated that the ARC ACBD7 isoform was produced and processed into a bioactive peptide referred to as nonadecaneuropeptide (NDN) in response to catabolic signals. We have characterized NDN as a potent anorexigenic signal acting through an uncharacterized endozepine G protein-coupled receptor and subsequently via the melanocortin system. Our results suggest that ACBD7-producing neurons participate in the hypothalamic leptin signalling pathway. Taken together, these data suggest that ACBD7-producing neurons are involved in the hypothalamic control exerted on food intake and energy expenditure by the leptin-melanocortin pathway. DOI:http://dx.doi.org/10.7554/eLife.11742.001 Obesity is an increasingly common problem worldwide. To treat it effectively, we must understand how the body controls how much food a person consumes and how much energy they expend. The hypothalamus is one region of the brain that plays a critical role in regulating this energy balance. Some of the neurons in the hypothalamus can change their activity when they detect satiety hormones including the leptin, which is produced by fat cells and suppresses appetite. However, it is not clear exactly how the neurons respond to leptin and other energy-related signals. Recent studies have linked the gene that encodes a protein called ACBD7 with obesity, and showed that it is one of the genes that is overexpressed in neurons that are sensitive to leptin. Now, Lanfray et al. have discovered a population of neurons that produce a new variant of the protein in the hypothalamus of mice. When this protein variant matures, it can be cut down to form a small protein-like molecule called NDN. Further experiments showed that leptin stimulates the production of both the new ABCD7 variant and NDN. Lanfray et al. then injected mice that had been denied food for a several hours with NDN. The injected mice ate less than untreated mice, and burn more energy. NDN appears to form part of the signaling pathway through which leptin signals to the hypothalamus to control appetite. In the future, creating mice in which the activity of the gene that encodes ACBD7 can be easily disrupted could help to reveal more about how the hypothalamus helps to control energy balance. DOI:http://dx.doi.org/10.7554/eLife.11742.002
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Affiliation(s)
- Damien Lanfray
- Centre de Recherche de l'Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec, Canada
| | - Alexandre Caron
- Centre de Recherche de l'Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec, Canada
| | - Marie-Claude Roy
- Centre de Recherche de l'Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec, Canada
| | - Mathieu Laplante
- Centre de Recherche de l'Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec, Canada
| | - Fabrice Morin
- Laboratory of Neuronal and Neuroendocrine Differentiation and Communication, Institut National de la Santé et de la Recherche Médicale, Mont-Saint-Aignan, France.,Institute for Research and Innovation in Biomedicine, Normandy University, Mont-Saint-Aignan, France
| | - Jérôme Leprince
- Laboratory of Neuronal and Neuroendocrine Differentiation and Communication, Institut National de la Santé et de la Recherche Médicale, Mont-Saint-Aignan, France.,Institute for Research and Innovation in Biomedicine, Normandy University, Mont-Saint-Aignan, France
| | - Marie-Christine Tonon
- Laboratory of Neuronal and Neuroendocrine Differentiation and Communication, Institut National de la Santé et de la Recherche Médicale, Mont-Saint-Aignan, France.,Institute for Research and Innovation in Biomedicine, Normandy University, Mont-Saint-Aignan, France
| | - Denis Richard
- Centre de Recherche de l'Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec, Canada
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19
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Jackson DS, Ramachandrappa S, Clark AJ, Chan LF. Melanocortin receptor accessory proteins in adrenal disease and obesity. Front Neurosci 2015; 9:213. [PMID: 26113808 PMCID: PMC4461818 DOI: 10.3389/fnins.2015.00213] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Accepted: 05/28/2015] [Indexed: 12/02/2022] Open
Abstract
Melanocortin receptor accessory proteins (MRAPs) are regulators of the melanocortin receptor family. MRAP is an essential accessory factor for the functional expression of the MC2R/ACTH receptor. The importance of MRAP in adrenal gland physiology is demonstrated by the clinical condition familial glucocorticoid deficiency type 2. The role of its paralog melanocortin-2-receptor accessory protein 2 (MRAP2), which is predominantly expressed in the hypothalamus including the paraventricular nucleus, has recently been linked to mammalian obesity. Whole body deletion and targeted brain specific deletion of the Mrap2 gene result in severe obesity in mice. Interestingly, Mrap2 complete knockout (KO) mice have increased body weight without detectable changes to food intake or energy expenditure. Rare heterozygous variants of MRAP2 have been found in humans with severe, early-onset obesity. In vitro data have shown that Mrap2 interaction with the melanocortin-4-receptor (Mc4r) affects receptor signaling. However, the mechanism by which Mrap2 regulates body weight in vivo is not fully understood and differences between the phenotypes of Mrap2 and Mc4r KO mice may point toward Mc4r independent mechanisms.
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Affiliation(s)
- David S Jackson
- Centre for Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London London, UK
| | - Shwetha Ramachandrappa
- Centre for Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London London, UK
| | - Adrian J Clark
- Centre for Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London London, UK
| | - Li F Chan
- Centre for Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London London, UK
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20
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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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21
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GPR17 gene disruption does not alter food intake or glucose homeostasis in mice. Proc Natl Acad Sci U S A 2015; 112:1845-9. [PMID: 25624481 DOI: 10.1073/pnas.1424968112] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
G protein-coupled receptor 17 (GPR17) was recently reported to be a Foxo1 target in agouti-related peptide (AGRP) neurons. Intracerebroventricular injection of GPR17 agonists induced food intake, whereas administration of an antagonist to the receptor reduced feeding. These data lead to the conclusion that pharmacological modulation of GPR17 has therapeutic potential to treat obesity. Here we report that mice deficient in Gpr17 (Gpr17(-/-)) have similar food intake and body weight compared with their wild-type littermates. Gpr17(-/-) mice have normal hypothalamic Agrp mRNA expression, AGRP plasma levels, and metabolic rate. GPR17 deficiency in mice did not affect glucose homeostasis or prevent fat-induced insulin resistance. These data do not support a role for GPR17 in the control of food intake, body weight, or glycemic control.
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22
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Yun JH, Kim K, Jung Y, Park JH, Cho HS, Lee W. Co-expression of human agouti-related protein enhances expression and stability of human melanocortin-4 receptor. Biochem Biophys Res Commun 2015; 456:116-21. [PMID: 25446108 DOI: 10.1016/j.bbrc.2014.11.044] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2014] [Accepted: 11/14/2014] [Indexed: 11/30/2022]
Abstract
G protein-coupled receptors (GPCRs) represent the largest family of transmembrane signaling proteins, and they are considered major targets of approximately half of all therapeutic agents. Human melanocortin-4 receptor (hMC4R) plays an important role in the control of energy homeostasis, and its mutants are directly related to severe human obesity. Here, we describe optimized protocols for the high-yield expression and purification of hMC4R that will accelerate structural study. Truncations of the N- and C-termini of hMC4R with T4 lysozyme (T4L) insertion increase the solubility as well as stability of the protein. Strikingly, co-expression of human mini-agouti-related protein (mini-AgRP) in Spodoptera frugiperda (Sf9) cells enables excellent stability of hMC4R. The protein yield in the human mini-AgRP co-expression system is increased by about 3-4 times compared to that of hMC4R alone. Data from analytical size exclusion chromatography (aSEC) and thermostability assay show that hMC4R becomes homogeneous and stable with a melting temperature of 58°C in the presence of human mini-AgRP.
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Affiliation(s)
- Ji-Hye Yun
- Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749, Republic of Korea
| | - Kuglae Kim
- Department of Systems Biology, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749, Republic of Korea
| | - Youngjin Jung
- Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749, Republic of Korea
| | - Jae-Hyun Park
- Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749, Republic of Korea
| | - Hyun-Soo Cho
- Department of Systems Biology, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749, Republic of Korea
| | - Weontae Lee
- Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749, Republic of Korea.
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23
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García-Borrón JC, Abdel-Malek Z, Jiménez-Cervantes C. MC1R, the cAMP pathway, and the response to solar UV: extending the horizon beyond pigmentation. Pigment Cell Melanoma Res 2014; 27:699-720. [PMID: 24807163 DOI: 10.1111/pcmr.12257] [Citation(s) in RCA: 128] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Accepted: 05/01/2014] [Indexed: 12/20/2022]
Abstract
The melanocortin 1 receptor (MC1R) is a G protein-coupled receptor crucial for the regulation of melanocyte proliferation and function. Upon binding melanocortins, MC1R activates several signaling cascades, notably the cAMP pathway leading to synthesis of photoprotective eumelanin. Polymorphisms in the MC1R gene are a major source of normal variation of human hair color and skin pigmentation, response to ultraviolet radiation (UVR), and skin cancer susceptibility. The identification of a surprisingly high number of MC1R natural variants strongly associated with pigmentary phenotypes and increased skin cancer risk has prompted research on the functional properties of the wild-type receptor and frequent mutant alleles. We summarize current knowledge on MC1R structural and functional properties, as well as on its intracellular trafficking and signaling. We also review the current knowledge about the function of MC1R as a skin cancer, particularly melanoma, susceptibility gene and how it modulates the response of melanocytes to UVR.
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Affiliation(s)
- Jose C García-Borrón
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Murcia, Murcia, Spain; Instituto Murciano de Investigación Biomédica (IMIB), El Palmar, Murcia, Spain
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24
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Agouti signalling protein is an inverse agonist to the wildtype and agonist to the melanic variant of the melanocortin-1 receptor in the grey squirrel (Sciurus carolinensis). FEBS Lett 2014; 588:2335-43. [PMID: 24879893 DOI: 10.1016/j.febslet.2014.05.032] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2014] [Revised: 04/17/2014] [Accepted: 05/15/2014] [Indexed: 01/26/2023]
Abstract
The melanocortin-1 receptor (MC1R) is a key regulator of mammalian pigmentation. Melanism in the grey squirrel is associated with an eight amino acid deletion in the mutant melanocortin-1 receptor with 24 base pair deletion (MC1RΔ24) variant. We demonstrate that the MC1RΔ24 exhibits a higher basal activity than the wildtype MC1R (MC1R-wt). We demonstrate that agouti signalling protein (ASIP) is an inverse agonist to the MC1R-wt but is an agonist to the MC1RΔ24. We conclude that the deletion in the MC1RΔ24 leads to a receptor with a high basal activity which is further activated by ASIP. This is the first report of ASIP acting as an agonist to MC1R.
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25
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Cerdá-Reverter JM, Agulleiro MJ, Cortés R, Sánchez E, Guillot R, Leal E, Fernández-Durán B, Puchol S, Eley M. Involvement of melanocortin receptor accessory proteins (MRAPs) in the function of melanocortin receptors. Gen Comp Endocrinol 2013; 188:133-6. [PMID: 23410915 DOI: 10.1016/j.ygcen.2013.01.017] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Revised: 01/21/2013] [Accepted: 01/27/2013] [Indexed: 12/30/2022]
Abstract
The melanocortin system integrates different agonists, competitive or inverse agonists, and receptors. Recent investigations have also discovered a specific system of melanocortin receptor accessory proteins (MRAPs) that are involved in the regulation of the functional expression of these receptors. MRAP1 mutations are responsible for type 2 familial glucocorticoid deficiency (FGD2), a rare autosomal disorder characterized by high plasma adrenocorticotropin hormone (ACTH) levels but severe cortisol deficiency. ACTH binds melanocortin 2 receptor (MC2R), a G protein-coupled receptor, in the adrenal gland to promote corticosteroid synthesis. In the absence of MRAP1, MC2R cannot translocate from the endoplasmic reticulum to the plasma membrane and ACTH-induced signaling is extinguished. A second MRAP protein, called MRAP2, also modulates MC2R activity. MRAPs also interact with the other melanocortin receptors, adjusting their pharmacological properties. In this paper, we briefly review the MRAP system and its interaction with melanocortin receptors.
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Affiliation(s)
- J M Cerdá-Reverter
- Department of Fish Physiology and Biotechnology, Instituto de Acuicultura de Torre de la Sal, Consejo Superior de Investigaciones Científicas (IATS-CSIC), 12595 Torre de la Sal, Ribera de Cabanes, Castellón, Spain.
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26
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Lerma-Cabrera JM, Carvajal F, Alcaraz-Iborra M, de la Fuente L, Navarro M, Thiele TE, Cubero I. Adolescent binge-like ethanol exposure reduces basal α-MSH expression in the hypothalamus and the amygdala of adult rats. Pharmacol Biochem Behav 2013; 110:66-74. [PMID: 23792540 DOI: 10.1016/j.pbb.2013.06.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2012] [Revised: 06/03/2013] [Accepted: 06/09/2013] [Indexed: 01/31/2023]
Abstract
Melanocortins (MC) are central peptides that have been implicated in the modulation of ethanol consumption. There is experimental evidence that chronic ethanol exposure reduces α-MSH expression in the limbic and hypothalamic brain regions and alters central pro-opiomelanocortin (POMC) mRNA activity in adult rats. Adolescence is a critical developmental period of high vulnerability in which ethanol exposure alters corticotropin releasing factor, neuropeptide Y, substance P and neurokinin neuropeptide activities, all of which have key roles in ethanol consumption. Given the involvement of MC and the endogenous inverse agonist AgRP in ethanol drinking, here we evaluate whether a binge-like pattern of ethanol treatment during adolescence has a relevant impact on basal and/or ethanol-stimulated α-MSH and AgRP activities during adulthood. To this end, adolescent Sprague-Dawley rats (beginning at PND25) were pre-treated with either saline (SP group) or binge-like ethanol exposure (BEP group; 3.0 g/kg given in intraperitoneal (i.p.) injections) of one injection per day over two consecutive days, followed by 2 days without injections, repeated for a total of 8 injections. Following 25 ethanol-free days, we evaluated α-MSH and AgRP immunoreactivity (IR) in the limbic and hypothalamic nuclei of adult rats (PND63) in response to ethanol (1.5 or 3.0 g/kgi.p.) and saline. We found that binge-like ethanol exposure during adolescence significantly reduced basal α-MSH IR in the central nucleus of the amygdala (CeA), the arcuate nucleus (Arc) and the paraventricular nucleus of the hypothalamus (PVN) during adulthood. Additionally, acute ethanol elicited AgRP IR in the Arc. Rats given the adolescent ethanol treatment required higher doses of ethanol than saline-treated rats to express AgRP. In light of previous evidence that endogenous MC and AgRP regulate ethanol intake through MC-receptor signaling, we speculate that the α-MSH and AgRP disturbances induced by binge-like ethanol exposure during adolescence may contribute to excessive ethanol consumption during adulthood.
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27
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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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28
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Effects of AgRP inhibition on energy balance and metabolism in rodent models. PLoS One 2013; 8:e65317. [PMID: 23762342 PMCID: PMC3675096 DOI: 10.1371/journal.pone.0065317] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2012] [Accepted: 04/28/2013] [Indexed: 12/15/2022] Open
Abstract
Activation of brain melanocortin-4 receptors (MC4-R) by α-melanocyte-stimulating hormone (MSH) or inhibition by agouti-related protein (AgRP) regulates food intake and energy expenditure and can modulate neuroendocrine responses to changes in energy balance. To examine the effects of AgRP inhibition on energy balance, a small molecule, non-peptide compound, TTP2515, developed by TransTech Pharma, Inc., was studied in vitro and in rodent models in vivo. TTP2515 prevented AgRP from antagonizing α-MSH-induced increases in cAMP in HEK 293 cells overexpressing the human MC4-R. When administered to rats by oral gavage TTP2515 blocked icv AgRP-induced increases in food intake, weight gain and adiposity and suppression of T4 levels. In both diet-induced obese (DIO) and leptin-deficient mice, TTP2515 decreased food intake, weight gain, adiposity and respiratory quotient. TTP2515 potently suppressed food intake and weight gain in lean mice immediately after initiation of a high fat diet (HFD) but had no effect on these parameters in lean chow-fed mice. However, when tested in AgRP KO mice, TTP2515 also suppressed food intake and weight gain during HFD feeding. In several studies TTP2515 increased T4 but not T3 levels, however this was also observed in AgRP KO mice. TTP2515 also attenuated refeeding and weight gain after fasting, an effect not evident in AgRP KO mice when administered at moderate doses. This study shows that TTP2515 exerts many effects consistent with AgRP inhibition however experiments in AgRP KO mice indicate some off-target effects of this drug. TTP2515 was particularly effective during fasting and in mice with leptin deficiency, conditions in which AgRP is elevated, as well as during acute and chronic HFD feeding. Thus the usefulness of this drug in treating obesity deserves further exploration, to define the AgRP dependent and independent mechanisms by which TTP2515 exerts its effects on energy balance.
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29
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Donovan MH, Tecott LH. Serotonin and the regulation of mammalian energy balance. Front Neurosci 2013; 7:36. [PMID: 23543912 PMCID: PMC3608917 DOI: 10.3389/fnins.2013.00036] [Citation(s) in RCA: 105] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2012] [Accepted: 03/03/2013] [Indexed: 01/17/2023] Open
Abstract
Maintenance of energy balance requires regulation of the amount and timing of food intake. Decades of experiments utilizing pharmacological and later genetic manipulations have demonstrated the importance of serotonin signaling in this regulation. Much progress has been made in recent years in understanding how central nervous system (CNS) serotonin systems acting through a diverse array of serotonin receptors impact feeding behavior and metabolism. Particular attention has been paid to mechanisms through which serotonin impacts energy balance pathways within the hypothalamus. How upstream factors relevant to energy balance regulate the release of hypothalamic serotonin is less clear, but work addressing this issue is underway. Generally, investigation into the central serotonergic regulation of energy balance has had a predominantly “hypothalamocentric” focus, yet non-hypothalamic structures that have been implicated in energy balance regulation also receive serotonergic innervation and express multiple subtypes of serotonin receptors. Moreover, there is a growing appreciation of the diverse mechanisms through which peripheral serotonin impacts energy balance regulation. Clearly, the serotonergic regulation of energy balance is a field characterized by both rapid advances and by an extensive and diverse set of central and peripheral mechanisms yet to be delineated.
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Affiliation(s)
- Michael H Donovan
- Department of Psychiatry, University of California San Francisco CA, USA
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30
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Suzuki H. Evolutionary and phylogeographic views on Mc1r and Asip variation in mammals. Genes Genet Syst 2013; 88:155-64. [DOI: 10.1266/ggs.88.155] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Affiliation(s)
- Hitoshi Suzuki
- Laboratory of Ecology and Genetics, Graduate School of Environmental Earth Science, Hokkaido University
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31
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Ersoy BA, Pardo L, Zhang S, Thompson DA, Millhauser G, Govaerts C, Vaisse C. Mechanism of N-terminal modulation of activity at the melanocortin-4 receptor GPCR. Nat Chem Biol 2012; 8:725-30. [PMID: 22729149 DOI: 10.1038/nchembio.1008] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2012] [Accepted: 05/14/2012] [Indexed: 01/29/2023]
Abstract
Most of our understanding of G protein-coupled receptor (GPCR) activation has been focused on the direct interaction between diffusible ligands and their seven-transmembrane domains. However, a number of these receptors depend on their extracellular N-terminal domain for ligand recognition and activation. To dissect the molecular interactions underlying both modes of activation at a single receptor, we used the unique properties of the melanocortin-4 receptor (MC4R), a GPCR that shows constitutive activity maintained by its N-terminal domain and is physiologically activated by the peptide α-melanocyte stimulating hormone (αMSH). We find that activation by the N-terminal domain and αMSH relies on different key residues in the transmembrane region. We also demonstrate that agouti-related protein, a physiological antagonist of MC4R, acts as an inverse agonist by inhibiting N terminus-mediated activation, leading to the speculation that a number of constitutively active orphan GPCRs could have physiological inverse agonists as sole regulators.
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Affiliation(s)
- Baran A Ersoy
- Department of Medicine, University of California-San Francisco, San Francisco, CA, USA
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32
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Madonna ME, Schurdak J, Yang YK, Benoit S, Millhauser GL. Agouti-related protein segments outside of the receptor binding core are required for enhanced short- and long-term feeding stimulation. ACS Chem Biol 2012; 7:395-402. [PMID: 22129136 DOI: 10.1021/cb2003412] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The agouti-related protein (AgRP) plays a central role in energy balance by reducing signaling through the hypothalamic melanocortin receptors (McRs) 3 and 4, in turn stimulating feeding and decreasing energy expenditure. Mature AgRP(83-132), produced by endoproteolytic processing, contains a central region that folds as an inhibitor cystine knot (ICK) stabilized by a network of disulfide bonds; this domain alone carries the molecular features for high affinity McR binding and inverse agonism. Outside of the ICK domain are two polypeptide segments, an N-terminal extension and a C-terminal loop, both completely conserved but of unknown function. Here we examine the physiological roles of these non-ICK segments by developing a panel of modified AgRPs that were administered to rats through intracerebroventricular (ICV) injection. Analysis of food consumption demonstrates that basic (positively charged) residues are essential for potent short- and long-term AgRP stimulated feeding. Moreover, we demonstrate an approximate linear relationship between protein charge density and 24 h food intake. Next, we developed artificial AgRP(83-132) analogues with increased positive charge and found that these species were substantially more potent than wild type. A single dose of one protein, designated AgRP-4K, results in enhanced feeding for well over a week and weight gain that is nearly double that of AgRP(83-132). These studies suggest new strategies for the development of potent orexigenic species and may serve as leads for the development of therapeutics for treating wasting conditions such as cachexia.
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Affiliation(s)
- Michael E. Madonna
- Department of Chemistry and
Biochemistry, University of California,
Santa Cruz, California 95064, United States
| | - Jennifer Schurdak
- Department of Psychiatry, University of Cincinnati, Cincinnati, Ohio 45237, United
States
| | - Ying-kui Yang
- Department of Surgery, University of Alabama at Birmingham, Birmingham, Alabama
35205, United States
| | - Stephen Benoit
- Department of Psychiatry, University of Cincinnati, Cincinnati, Ohio 45237, United
States
| | - Glenn L. Millhauser
- Department of Chemistry and
Biochemistry, University of California,
Santa Cruz, California 95064, United States
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33
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Sohn JW, Williams KW. Functional heterogeneity of arcuate nucleus pro-opiomelanocortin neurons: implications for diverging melanocortin pathways. Mol Neurobiol 2012; 45:225-33. [PMID: 22328135 DOI: 10.1007/s12035-012-8240-6] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2011] [Accepted: 01/26/2012] [Indexed: 01/04/2023]
Abstract
Arcuate nucleus (ARC) pro-opiomelanocortin (POMC) neurons are essential regulators of food intake, energy expenditure, and glucose homeostasis. POMC neurons integrate several key metabolic signals that include neurotransmitters and hormones. The change in activity of POMC neurons is relayed to melanocortin receptors in distinct regions of the central nervous system. This review will summarize the role of leptin and serotonin receptors in regulating the activity of POMC neurons and provide a model in which different melanocortin pathways regulate energy and glucose homeostasis.
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Affiliation(s)
- Jong-Woo Sohn
- Division of Hypothalamic Research, Department of Internal Medicine, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, TX 75390-9077, USA
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34
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Cerdá-Reverter JM, Agulleiro MJ, R RG, Sánchez E, Ceinos R, Rotllant J. Fish melanocortin system. Eur J Pharmacol 2011; 660:53-60. [DOI: 10.1016/j.ejphar.2010.10.108] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2010] [Revised: 09/30/2010] [Accepted: 10/12/2010] [Indexed: 12/26/2022]
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35
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Overton JD, Leibel RL. Mahoganoid and mahogany mutations rectify the obesity of the yellow mouse by effects on endosomal traffic of MC4R protein. J Biol Chem 2011; 286:18914-29. [PMID: 21460229 DOI: 10.1074/jbc.m111.224592] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The ubiquitous overexpression of agouti-signaling protein (ASP), a paracrine-signaling molecule that regulates pigment-type switching in the hair follicle of the mouse, is responsible for the obesity and yellow pelage of the Yellow mouse (A(y)). Mahogany (Attractin, Atrn/mg) and mahoganoid (Mahogunin Ring Finger-1, Mgrn1/md) are mutations epistatic to A(y). These mutations have been described as suppressors of ASP action, blocking its antagonizing effects on the melanocortin 1 and 4 receptors (MC1R and MC4R) in the skin and the brain, respectively, via unknown mechanisms. Here, we describe the molecular bases for the md- and mg-dependent rescue of the A(y) phenotype at the MC4R. We show that overexpression of ASP inhibits the rise in cAMP levels in response to α-melanocyte-stimulating hormone, an MC4R agonist, by blocking ligand binding and by directing MC4R trafficking to the lysosome. Loss-of-function of either attractin or MGRN1 blocks ASP-dependent MC4R degradation and promotes increased trafficking of internalized MC4R to the cell surface, but it does not restore α-melanocyte-stimulating hormone-dependent cAMP signaling. We propose that MGRN1 and attractin are components of an evolutionarily conserved receptor trafficking pathway and that the md and mg mutations rescue the A(y) phenotypes by a primarily cAMP-independent mechanism promoting trafficking of MC4R and likely MC1R away from the lysosome toward the cell surface.
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Affiliation(s)
- John D Overton
- Division of Molecular Genetics, Department of Pediatrics, Naomi Berrie Diabetes Center and the Institute of Human Nutrition, Columbia University, New York, New York 10032, USA.
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36
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Oguro-Okano M, Honda M, Yamazaki K, Okano K. Mutations in the melanocortin 1 receptor, β-defensin103 and agouti signaling protein genes, and their association with coat color phenotypes in Akita-inu dogs. J Vet Med Sci 2011; 73:853-8. [PMID: 21321476 DOI: 10.1292/jvms.10-0439] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To identify factors that control coat color in Akita-inu dogs, we sequenced all the exons of the melanocortin 1 receptor (MC1R), β-defensin103 (CBD103) and agouti signaling protein (ASIP) genes of dogs with four distinct coat colors, namely, brindle, sesame, red and white. Then we examined correlations among specific alleles and coat color. In the case of the MC1R gene, all white dogs were homozygous for a nonsense mutation, R306ter, while brindle, sesame, and red dogs had at least one R306 allele. In the case of the CBD103 gene, all brindle dogs were heterozygous for the G23del mutation (deletion of codon 23, encoding glycine), while all sesame and red dogs were homozygous for G23. In the case of the ASIP gene, all dogs, regardless of coat color, had at least one S82 H83 allele. A missense mutation in the ASIP gene, P87L, was identified for the first time in some Akita-inu dogs but was not associated with any specific coloration. Our results indicate that the 2 key mutations, R306ter in the MC1R gene and G23del in the CBD103 gene, are associated with the phenotypic discriminations among brindle, red/sesame, and white coats, while no mutation that might potentially be associated with the discrimination of a sesame coat from a red coat is present in the coding sequences of these three genes.
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Affiliation(s)
- Mieko Oguro-Okano
- Department of Animal Health Technology, Yamazaki Gakuen University, Tokyo, Japan.
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37
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Williams KW, Scott MM, Elmquist JK. Modulation of the central melanocortin system by leptin, insulin, and serotonin: co-ordinated actions in a dispersed neuronal network. Eur J Pharmacol 2011; 660:2-12. [PMID: 21211525 DOI: 10.1016/j.ejphar.2010.11.042] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Revised: 10/08/2010] [Accepted: 11/02/2010] [Indexed: 10/18/2022]
Abstract
Over the past century, prevalent models of energy and glucose homeostasis have been developed from a better understanding of the neural circuits underlying obesity and diabetes. From the early hypothalamic lesion reports to the more recent pharmacological and molecular/genetic studies, the hypothalamic melanocortin system has been shown to play a critical role in the regulation of metabolism. This review attempts to highlight contributions to our current understanding of how numerous neuromodulators (leptin, insulin, and serotonin) integrate with the central melanocortin system to coordinate alterations in energy and glucose balance.
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Affiliation(s)
- Kevin W Williams
- Division of Hypothalamic Research, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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38
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Lee CJ, Yun JH, Lim SK, Lee W. Solution structures and molecular interactions of selective melanocortin receptor antagonists. Mol Cells 2010; 30:551-6. [PMID: 21110130 DOI: 10.1007/s10059-010-0152-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2010] [Revised: 09/11/2010] [Accepted: 09/13/2010] [Indexed: 10/18/2022] Open
Abstract
The solution structures and inter-molecular interaction of the cyclic melanocortin antagonists SHU9119, JKC363, HS014, and HS024 with receptor molecules have been determined by NMR spectroscopy and molecular modeling. While SHU9119 is known as a nonselective antagonist, JKC363, HS014, and HS024 are selective for the melanocortin subtype-4 receptor (MC4R) involved in modulation of food intake. Data from NMR and molecular dynamics suggest that the conformation of the Trp9 sidechain in the three MC4R-selective antagonists is quite different from that of SHU9119. This result strongly supports the concept that the spatial orientation of the hydrophobic aromatic residue is more important for determining selectivity than the presence of a basic, "arginine-like" moiety responsible for biological activity. We propose that the conformation of hydrophobic residues of MCR antagonists is critical for receptor-specific selectivity.
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MESH Headings
- Amino Acid Sequence
- Binding Sites
- Drug Interactions
- Hydrophobic and Hydrophilic Interactions
- Magnetic Resonance Spectroscopy
- Melanocyte-Stimulating Hormones/chemical synthesis
- Melanocyte-Stimulating Hormones/chemistry
- Melanocyte-Stimulating Hormones/pharmacology
- Models, Molecular
- Molecular Sequence Data
- Peptides, Cyclic/chemical synthesis
- Peptides, Cyclic/chemistry
- Peptides, Cyclic/pharmacology
- Receptor, Melanocortin, Type 4/antagonists & inhibitors
- Receptor, Melanocortin, Type 4/drug effects
- Receptors, Melanocortin/antagonists & inhibitors
- Receptors, Melanocortin/drug effects
- Sensitivity and Specificity
- Solutions/chemistry
- Structure-Activity Relationship
- beta-MSH/chemical synthesis
- beta-MSH/chemistry
- beta-MSH/pharmacology
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Affiliation(s)
- Chul-Jin Lee
- Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749, Korea
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39
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Mayorov AV, Cai M, Palmer ES, Liu Z, Cain JP, Vagner J, Trivedi D, Hruby VJ. Solid-phase peptide head-to-side chain cyclodimerization: discovery of C(2)-symmetric cyclic lactam hybrid α-melanocyte-stimulating hormone (MSH)/agouti-signaling protein (ASIP) analogues with potent activities at the human melanocortin receptors. Peptides 2010; 31:1894-905. [PMID: 20688117 PMCID: PMC3041174 DOI: 10.1016/j.peptides.2010.06.026] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/21/2010] [Revised: 06/23/2010] [Accepted: 06/23/2010] [Indexed: 02/05/2023]
Abstract
A novel hybrid melanocortin pharmacophore was designed based on the pharmacophores of the agouti-signaling protein (ASIP), an endogenous melanocortin antagonist, and α-melanocyte-stimulating hormone (α-MSH), an endogenous melanocortin agonist. The designed hybrid ASIP/MSH pharmacophore was explored in monomeric cyclic, and cyclodimeric templates. The monomeric cyclic disulfide series yielded peptides with hMC3R-selective non-competitive binding affinities. The direct on-resin peptide lactam cyclodimerization yielded nanomolar range (25-120 nM) hMC1R-selective full and partial agonists in the cyclodimeric lactam series which demonstrates an improvement over the previous attempts at hybridization of MSH and agouti protein sequences. The secondary structure-oriented pharmacophore hybridization strategy will prove useful in development of unique allosteric and orthosteric melanocortin receptor modulators. This report also illustrates the utility of peptide cyclodimerization for the development of novel GPCR peptide ligands.
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Affiliation(s)
| | - Minying Cai
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, USA
| | - Erin S. Palmer
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, USA
| | - Zhihua Liu
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, USA
| | - James P. Cain
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, USA
| | - Josef Vagner
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, USA
| | - Dev Trivedi
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, USA
| | - Victor J. Hruby
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, USA
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Patel MP, Cribb Fabersunne CS, Yang YK, Kaelin CB, Barsh GS, Millhauser GL. Loop-swapped chimeras of the agouti-related protein and the agouti signaling protein identify contacts required for melanocortin 1 receptor selectivity and antagonism. J Mol Biol 2010; 404:45-55. [PMID: 20831872 DOI: 10.1016/j.jmb.2010.08.054] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2010] [Revised: 08/12/2010] [Accepted: 08/30/2010] [Indexed: 11/29/2022]
Abstract
Agouti-related protein (AgRP) and agouti signaling protein (ASIP) are homologs that play critical roles in energy balance and pigmentation, respectively, by functioning as antagonistic ligands at their cognate melanocortin receptors. Signaling specificity is mediated in part through receptor binding selectivity brought about by alterations in the cysteine-rich carboxy-terminal domains of the ligands. AgRP binds with high affinity to the melanocortin 3 receptor and the melanocortin 4 receptor, but not to the melanocortin 1 receptor (MC1R), whereas ASIP binds with high affinity to all three receptors. This work explores the structural basis for receptor selectivity by studying chimeric proteins developed by interchanging loops between the cysteine-rich domain of ASIP and the cysteine-rich domain of AgRP. Binding data demonstrate that melanocortin 4 receptor responds to all chimeras and is therefore highly tolerant of gross loop changes. By contrast, MC1R responds primarily to those chimeras with a sequence close to that of wild-type ASIP. Further analysis of binding and functional data suggests that the ASIP C-terminal loop (a six-amino-acid segment closed by the final disulfide bond) is essential for high-affinity MC1R binding and inverse agonism. Comparison with previously published molecular models suggests that this loop makes contact with the first extracellular loop of MC1R through a series of key hydrophobic interactions.
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Affiliation(s)
- Mira P Patel
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064, USA
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Abstract
The melanocortin-4 receptor (MC4R) was cloned in 1993 by degenerate PCR; however, its function was unknown. Subsequent studies suggest that the MC4R might be involved in regulating energy homeostasis. This hypothesis was confirmed in 1997 by a series of seminal studies in mice. In 1998, human genetic studies demonstrated that mutations in the MC4R gene can cause monogenic obesity. We now know that mutations in the MC4R are the most common monogenic form of obesity, with more than 150 distinct mutations reported thus far. This review will summarize the studies on the MC4R, from its cloning and tissue distribution to its physiological roles in regulating energy homeostasis, cachexia, cardiovascular function, glucose and lipid homeostasis, reproduction and sexual function, drug abuse, pain perception, brain inflammation, and anxiety. I will then review the studies on the pharmacology of the receptor, including ligand binding and receptor activation, signaling pathways, as well as its regulation. Finally, the pathophysiology of the MC4R in obesity pathogenesis will be reviewed. Functional studies of the mutant MC4Rs and the therapeutic implications, including small molecules in correcting binding and signaling defect, and their potential as pharmacological chaperones in rescuing intracellularly retained mutants, will be highlighted.
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Affiliation(s)
- Ya-Xiong Tao
- Department of Anatomy, Physiology, and Pharmacology, Auburn University, Alabama 36849-5519, USA.
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Lopaschuk GD, Ussher JR, Jaswal JS. Targeting intermediary metabolism in the hypothalamus as a mechanism to regulate appetite. Pharmacol Rev 2010; 62:237-64. [PMID: 20392806 DOI: 10.1124/pr.109.002428] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The central nervous system mediates energy balance (energy intake and energy expenditure) in the body; the hypothalamus has a key role in this process. Recent evidence has demonstrated an important role for hypothalamic malonyl CoA in mediating energy balance. Malonyl CoA is generated by the carboxylation of acetyl CoA by acetyl CoA carboxylase and is then either incorporated into long-chain fatty acids by fatty acid synthase, or converted back to acetyl-CoA by malonyl CoA decarboxylase. Increased hypothalamic malonyl CoA is an indicator of energy surplus, resulting in a decrease in food intake and an increase in energy expenditure. In contrast, a decrease in hypothalamic malonyl CoA signals an energy deficit, resulting in an increased appetite and a decrease in body energy expenditure. A number of hormonal and neural orexigenic and anorexigenic signaling pathways have now been shown to be associated with changes in malonyl CoA levels in the arcuate nucleus (ARC) of the hypothalamus. Despite compelling evidence that malonyl CoA is an important mediator in the hypothalamic ARC control of food intake and regulation of energy balance, the mechanism(s) by which this occurs has not been established. Malonyl CoA inhibits carnitine palmitoyltransferase-1 (CPT-1), and it has been proposed that the substrate of CPT-1, long-chain acyl CoA(s), may act as a mediator(s) of appetite and energy balance. However, recent evidence has challenged the role of long-chain acyl CoA(s) in this process, as well as the involvement of CPT-1 in hypothalamic malonyl CoA signaling. A better understanding of how malonyl CoA regulates energy balance should provide novel approaches to targeting intermediary metabolism in the hypothalamus as a mechanism to control appetite and body weight. Here, we review the data supporting an important role for malonyl CoA in mediating hypothalamic control of energy balance, and recent evidence suggesting that targeting malonyl CoA synthesis or degradation may be a novel approach to favorably modify appetite and weight gain.
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Affiliation(s)
- Gary D Lopaschuk
- 423 Heritage Medical Research Center, University of Alberta, Edmonton, Canada T6G2S2.
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Boghossian S, Park M, York DA. Melanocortin activity in the amygdala controls appetite for dietary fat. Am J Physiol Regul Integr Comp Physiol 2010; 298:R385-93. [DOI: 10.1152/ajpregu.00591.2009] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The amygdala is rich in melanocortin 4 receptors. Because the reduction in dietary fat intake after enterostatin is injected in the central nucleus of the amygdala (CeA) is blocked by a melanocortin 4 receptor antagonist, we investigated the role of melanocortin activity in the CeA in regulating food intake and macronutrient choice. Sprague-Dawley rats, fitted with CeA cannulas, were fed either chow, a high-fat (HF) diet, or adapted to a two-choice HF or low-fat (LF) diet. Injections of the MC4R agonist melanotan II (MTII) in the CeA had a dose-dependent inhibitory effect on food intake that lasted for at least 24 h. This response was greater in rats fed a HF diet. The inverse agonist agouti-related protein (AgRP) and antagonist SHU-9119 increased food intake in a dose-dependent manner, with the hyperphagia lasting for 60 h. In rats adapted to a two-choice HF/LF diet, MTII decreased HF consumption but had no effect on LF consumption, resulting in a long-lasting decrease in total calorie intake (−35.5% after 24 h, P < 0.05). Total calorie intake increased in both AgRP- and SHU-9119-treated rats (32 and 109% after 24 h, respectively) as the result of increased intake of HF diet. There was no modification of LF consumption with AgRP treatment and a transient nonsignificant decrease with SHU-9119 treatment. Amygdala brain-derived neurotrophic factor expression was increased by AgRP in fed rats. These results identify the amygdala as a site of action for the melanocortin system to control food intake and dietary preferences.
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Affiliation(s)
| | - MieJung Park
- Center for Advanced Nutrition, Utah State University, Logan, Utah
| | - David A. York
- Center for Advanced Nutrition, Utah State University, Logan, Utah
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Tao YX, Huang H, Wang ZQ, Yang F, Williams JN, Nikiforovich GV. Constitutive activity of neural melanocortin receptors. Methods Enzymol 2010; 484:267-79. [PMID: 21036237 DOI: 10.1016/b978-0-12-381298-8.00014-9] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
The two neural melanocortin receptors (MCRs), melanocortin-3 and -4 receptors (MC3R and MC4R), are G protein-coupled receptors expressed primarily in the brain that regulate different aspects of energy homeostasis. The MCRs are unique in having endogenous antagonists, agouti and agouti-related protein (AgRP). These antagonists were later shown to be inverse agonists. The MC3R has little or no constitutive activity, whereas the MC4R has significant constitutive activity that can easily be detected. We describe herein methods for detecting constitutive activities in these receptors and small molecule ligands as inverse agonists. AgRP is an inverse agonist for both MC3R and MC4R. We also provide models for the constitutively active MC4R mutants.
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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
Named originally for their effects on peripheral end organs, the melanocortin system controls a diverse set of physiological processes through a series of five G-protein-coupled receptors and several sets of small peptide ligands. The central melanocortin system plays an essential role in homeostatic regulation of body weight, in which two alternative ligands, alpha-melanocyte-stimulating hormone and agouti-related protein, stimulate and inhibit receptor signaling in several key brain regions that ultimately affect food intake and energy expenditure. Much of what we know about the relationship between central melanocortin signaling and body weight regulation stems from genetic studies. Comparative genomic studies indicate that melanocortin receptors used for controlling pigmentation and body weight regulation existed more than 500 million years ago in primitive vertebrates, but that fine-grained control of melanocortin receptors through neuropeptides and endogenous antagonists developed more recently. Recent studies based on dog coat-color genetics revealed a new class of melanocortin ligands, the beta-defensins, which reveal the potential for cross talk between the melanocortin and the immune systems.
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46
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Bromberg Y, Overton J, Vaisse C, Leibel RL, Rost B. In silico mutagenesis: a case study of the melanocortin 4 receptor. FASEB J 2009; 23:3059-69. [PMID: 19417090 PMCID: PMC2735358 DOI: 10.1096/fj.08-127530] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The melanocortin 4 receptor (MC4R) is a G-protein-coupled receptor (GPCR) and a key molecule in the regulation of energy homeostasis. At least 159 substitutions in the coding region of human MC4R (hMC4R) have been described experimentally; over 80 of those occur naturally, and many have been implicated in obesity. However, assessment of the presumably functionally essential residues remains incomplete. Here we have performed a complete in silico mutagenesis analysis to assess the functional essentiality of all possible nonnative point mutants in the entire hMC4R protein (332 residues). We applied SNAP, which is a method for quantifying functional consequences of single amino acid (AA) substitutions, to calculate the effects of all possible substitutions at each position in the hMC4R AA sequence. We compiled a mutability score that reflects the degree to which a particular residue is likely to be functionally important. We performed the same experiment for a paralogue human melanocortin receptor (hMC1R) and a mouse orthologue (mMC4R) in order to compare computational evaluations of highly related sequences. Three results are most salient: 1) our predictions largely agree with the available experimental annotations; 2) this analysis identified several AAs that are likely to be functionally critical, but have not yet been studied experimentally; and 3) the differential analysis of the receptors implicates a number of residues as specifically important to MC4Rs vs. other GPCRs, such as hMC1R.—Bromberg, Y., Overton, J., Vaisse, C., Leibel, R. L., Rost, B. In silico mutagenesis: a case study of the melanocortin 4 receptor.
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Affiliation(s)
- Yana Bromberg
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York, USA.
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47
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Sánchez E, Rubio VC, Thompson D, Metz J, Flik G, Millhauser GL, Cerdá-Reverter JM. Phosphodiesterase inhibitor-dependent inverse agonism of agouti-related protein on melanocortin 4 receptor in sea bass (Dicentrarchus labrax). Am J Physiol Regul Integr Comp Physiol 2009; 296:R1293-306. [PMID: 19225141 DOI: 10.1152/ajpregu.90948.2008] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The melanocortin 4 receptor (MC4R) is a G protein-coupled receptor mainly expressed in the central nervous system of vertebrates. Activation of the MC4R leads to a decrease in food intake, whereas inactivating mutations are a genetic cause of obesity. The binding of agouti-related protein (AGRP) reduces not only agonist-stimulated cAMP production (competitive antagonist) but also the basal activity of the receptor, as an inverse agonist. Transgenic zebrafish overexpressing AGRP display increased food intake and linear growth, indicative of a physiological role for the melanocortin system in the control of the energy balance in fish. We report on the cloning, pharmacological characterization, tissue distribution, and detailed brain mapping of a sea bass (Dicentrarchus labrax) MC4R ortholog. Sea bass MC4R is profusely expressed within food intake-controlling pathways of the fish brain. However, the activity of the melanocortin system during progressive fasting does not depend on the hypothalamic/pituitary proopiomelanocortin (POMC) and MC4R expression, which suggests that sea bass MC4R is constitutively activated and regulated by AGRP binding. We demonstrate that AGRP acts as competitive antagonist and reduces MTII-induced cAMP production. AGRP also decreases the basal activity of the receptor as an inverse agonist. This observation suggests that MC4R is constitutively active and supports the evolutionary conservation of the AGRP/MC4R interactions. The inverse agonism, but not the competitive antagonism, depends on the presence of a phosphodiesterase inhibitor (IBMX). This suggests that inverse agonism and competitive antagonism operate through different intracellular signaling pathways, a view that opens up new targets for the treatment of melanocortin-induced metabolic syndrome.
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Affiliation(s)
- Elisa Sánchez
- Dept. of Fish Reproductive Physiology, Instituto de Acuicultura de Torre de la Sal, Ribera de Cabanes, Castellón, Spain
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Park M, Oh H, York DA. Enterostatin affects cyclic AMP and ERK signaling pathways to regulate Agouti-related protein (AgRP) expression. Peptides 2009; 30:181-90. [PMID: 19059445 DOI: 10.1016/j.peptides.2008.11.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2008] [Revised: 11/06/2008] [Accepted: 11/07/2008] [Indexed: 10/25/2022]
Abstract
Enterostatin, a gut-brain peptide, inhibits dietary fat intake in rats. The purpose of this study was to identify the intracellular signaling pathways that are responsive to enterostatin and that modulate the effects of enterostatin on the expression of Agouti-related protein (AgRP). We used the hypothalamic GT1-7 neuronal cell line to identify the effects of enterostatin on cyclic AMP and ERK signaling using conventional immunoassays or Western blots to assay the activity of these pathways. Enterostatin enhanced the level of cyclic AMP, PKA(RIIbeta) and phospho-CREB and increased pERK levels in GT 1-7 cells. The effects on pERK were rapid (7.5 min) and dose-dependent. These signaling responses were blocked by an antibody to the enterostatin receptor (beta subunit of F1-ATPase), by the pERK inhibitor U0126 and by the P2Y receptor antagonist Suramin. Enterostatin showed a biphasic effect on AgRP mRNA, initially increasing but subsequently decreasing the levels. The cyclic AMP activator Sp-cAMP increased AgRP mRNA expression. Transfection of a wild type ERK construct reduced AgRP mRNA levels. Enterostatin inhibited expression of Krüppel-like factor 4 (KLF4), a transcriptional regulator of AgRP. KLF4 gene expression was increased by Sp-cAMP but decreased by wild-type ERK expression. U0126 blocked the effect of enterostatin on KLF4 expression. We conclude that enterostatin binding to its receptor activates the pERK pathway to inhibit AgRP gene expression but may enhance AgRP expression through activation of the cyclic AMP pathway. These pathways probably mediate the enterostatin inhibition of dietary fat intake.
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Affiliation(s)
- Miejung Park
- Center for Advanced Nutrition, Utah State University, 4715 Old Main Hill, Logan, UT 84322-4715, USA
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49
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Agouti-related peptide and MC3/4 receptor agonists both inhibit excitatory hypothalamic ventromedial nucleus neurons. J Neurosci 2008; 28:5433-49. [PMID: 18495877 DOI: 10.1523/jneurosci.0749-08.2008] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Anorexigenic melanocortins decrease food intake by activating MC3/MC4 receptors (MC3/4R); the prevailing view is that the orexigenic neuropeptide agouti-related peptide (AgRP) exerts the opposite action by acting as an antagonist at MC3/MC4 receptors. A total of 370 hypothalamic ventromedial nucleus (VMH) glutamatergic neurons was studied using whole-cell recording in hypothalamic slices from a novel mouse expressing green fluorescent protein (GFP) under control of the vesicular glutamate transporter 2 (vGluT2) promoter. Massive numbers of GFP-expressing VMH dendrites extended out of the core of the nucleus into the surrounding cell-poor shell. VMH dendrites received frequent appositions from AgRP-immunoreactive axons in the shell of the nucleus, but not the core, suggesting that AgRP may influence target VMH neurons. alpha-MSH, melanotan II (MTII), and selective MC3R or MC4R agonists were all inhibitory, reducing the spontaneous firing rate and hyperpolarizing vGluT2 neurons. The MC3/4R antagonist SHU9119 was excitatory. Unexpectedly, AgRP did not attenuate MTII actions on these neurons; instead, these two compounds showed an additive inhibitory effect. In the absence of synaptic activity, no hyperpolarization or change in input resistance was evoked by either MTII or AgRP, suggesting indirect actions. Consistent with this view, MTII increased the frequency of spontaneous and miniature IPSCs. In contrast, the mechanism of AgRP inhibition was dependent on presynaptic inhibition of EPSCs mediated by G(i)/G(o)-proteins, and was attenuated by pertussis toxin and NF023, inconsistent with mediation by G(s)-proteins associated with MC receptors. Together, our data suggest that the mechanism of AgRP actions on these excitatory VMH cells appears to be independent of the actions of melanocortins on MC receptors.
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50
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Tolle V, Low MJ. In vivo evidence for inverse agonism of Agouti-related peptide in the central nervous system of proopiomelanocortin-deficient mice. Diabetes 2008; 57:86-94. [PMID: 17909095 DOI: 10.2337/db07-0733] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Melanocyte-stimulating hormone (MSH) peptides processed from proopiomelanocortin (POMC) regulate energy homeostasis by activating neuronal melanocortin receptor (MC-R) signaling. Agouti-related peptide (AgRP) is a naturally occurring MC-R antagonist but also displays inverse agonism at constitutively active melanocortin-4 receptor (MC4-R) expressed on transfected cells. We investigated whether AgRP functions similarly in vivo using mouse models that lack all neuronal MSH, thereby precluding competitive antagonism of MC-R by AgRP. RESEARCH DESIGN AND METHODS Feeding and metabolic effects of the MC-R agonist melanotan II (MTII), AgRP, and ghrelin were investigated after intracerebroventricular injection in neural-specific POMC-deficient (Pomc(-/-)Tg/+) and global POMC-deficient (Pomc(-/-)) mice. Gene expression was quantified by RT-PCR. RESULTS Hyperphagic POMC-deficient mice were more sensitive than wild-type mice to the anorectic effects of MTII. Hypothalamic melanocortin-3 (MC3)/4-R mRNAs in POMC-deficient mice were unchanged, suggesting increased receptor sensitivity as a possible mechanism for the heightened anorexia. AgRP reversed MTII-induced anorexia in both mutant strains, demonstrating its ability to antagonize MSH agonists at central MC3/4-R, but did not produce an acute orexigenic response by itself. The action of ghrelin was attenuated in Pomc(-/-)Tg/+ mice, suggesting decreased sensitivity to additional orexigenic signals. However, AgRP induced delayed and long-lasting modifications of energy balance in Pomc(-/-)Tg/+, but not glucocorticoid-deficient Pomc(-/-) mice, by decreasing oxygen consumption, increasing the respiratory exchange ratio, and increasing food intake. CONCLUSIONS These data demonstrate that AgRP can modulate energy balance via a mechanism independent of MSH and MC3/4-R competitive antagonism, consistent with either inverse agonist activity at MC-R or interaction with a distinct receptor.
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Affiliation(s)
- Virginie Tolle
- Center for the Study of Weight Regulation and Associated Disorders, Oregon Health and Science University, Portland, Oregon, USA.
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