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Nakadate K, Kawakami K. Immunohistochemical and Immunoelectron Microscopical Distribution of MEGF8 in the Mouse Central Nervous System. Cells 2023; 13:63. [PMID: 38201267 PMCID: PMC10778434 DOI: 10.3390/cells13010063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Revised: 12/20/2023] [Accepted: 12/25/2023] [Indexed: 01/12/2024] Open
Abstract
Mutations in multiple epidermal growth factor-like domain 8 (MEGF8), a multidomain transmembrane protein encoded by a gene conserved across species, cause Carpenter's syndrome, which is associated with learning disabilities, mental health issues, and left-right patterning abnormalities. MEGF8 interacts with MGRN1, a protein that functions as an E3 ubiquitin ligase and is involved in multiple physiological and pathological processes. However, the mechanism underlying the distribution of MEGF8 in the central nervous system (CNS) and its cellular and subcellular locations remain unknown. This study aimed to map MEGF8 in the mouse CNS using a new antibody. We discovered that MEGF8 was distributed in the majority of neuronal cell somata across most CNS regions. High levels of MEGF8 were expressed in the neuropils of the CNS gray matter. Immunoelectron microscopy showed that MEGF8 was present in the synapses and around the outer mitochondrial membrane. These findings show that MEGF8 is uniformly distributed throughout the mouse CNS, and its distribution indicates that it plays a substantial role in synaptic and mitochondrial functions. To the best of our knowledge, this is the first study to document MEGF8 distribution in the CNS.
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Affiliation(s)
- Kazuhiko Nakadate
- Department of Basic Science, Educational and Research Center for Pharmacy, Meiji Pharmaceutical University, 2-522-1 Noshio, Kiyose 204-8588, Tokyo, Japan;
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Li Y, Wang X, Lu L, Wang M, Zhai Y, Tai X, Dilimulati D, Lei X, Xu J, Zhang C, Fu Y, Qu S, Li Q, Zhang C. Identification of novel GPCR partners of the central melanocortin signaling. Mol Metab 2021; 53:101317. [PMID: 34400348 PMCID: PMC8458986 DOI: 10.1016/j.molmet.2021.101317] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Revised: 08/03/2021] [Accepted: 08/10/2021] [Indexed: 12/12/2022] Open
Abstract
OBJECTIVE Homo- or heterodimerization of G protein-coupled receptors (GPCRs) generally affects the normal functioning of these receptors and mediates the responses to a variety of physiological stimuli in vivo. It is well known that melanocortin-3 receptor (MC3R) and melanocortin-4 receptor (MC4R) are key regulators of appetite and energy homeostasis in the central nervous system. However, the GPCR partners of MC3R and MC4R are not well understood. Our objective is to analyze single cell RNA-seq datasets of the hypothalamus to explore and identify novel GPCR partners of MC3R and MC4R and examine the pharmacological effect on the downstream signal transduction and membrane translocation of melanocortin receptors. METHODS We conducted an integrative analysis of multiple single cell RNA-seq datasets to reveal the expression pattern and correlation of GPCR families in the mouse hypothalamus. The emerging GPCRs with important metabolic functions were selected for cloning and co-immunoprecipitation validation. The positive GPCR partners were then tested for the pharmacological activation, competitive binding assay and surface translocation ELISA experiments. RESULTS Based on the expression pattern of GPCRs and their function enrichment results, we narrowed down the range of potential GPCR interaction with MC3R and MC4R for further confirmation. Co-immunoprecipitation assay verified 23 and 32 novel GPCR partners that interacted with MC3R and MC4R in vitro. The presence of these GPCR partners exhibited different effects in the physiological regulation and signal transduction of MC3R and MC4R. CONCLUSIONS This work represented the first large-scale screen for the functional GPCR complex of central melanocortin receptors and defined a composite metabolic regulatory GPCR network of the hypothalamic nucleuses.
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Affiliation(s)
- Yunpeng Li
- Department of Endocrinology and Metabolism, National Metabolic Management Center, Shanghai Tenth People's Hospital, Shanghai Key Laboratory of Signaling and Disease Research, Frontier Science Center for Stem Cell Research, School of Life Sciences and Technology, Tongji University, Shanghai, China
| | - Xiaozhu Wang
- Shanghai Key Laboratory of Signaling and Disease Research, Translational Medical Center for Stem Cell Therapy and Institute for Regenerative Medicine, Frontier Science Center for Stem Cell Research, School of Life Sciences and Technology, Shanghai East Hospital, Tongji University, Shanghai, China.
| | - Liumei Lu
- Department of Endocrinology and Metabolism, National Metabolic Management Center, Shanghai Tenth People's Hospital, Shanghai Key Laboratory of Signaling and Disease Research, Frontier Science Center for Stem Cell Research, School of Life Sciences and Technology, Tongji University, Shanghai, China
| | - Meng Wang
- Department of Plastic and Reconstructive Surgery, Shanghai Institute of Precision Medicine, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yue Zhai
- Department of Endocrinology and Metabolism, National Metabolic Management Center, Shanghai Tenth People's Hospital, Shanghai Key Laboratory of Signaling and Disease Research, Frontier Science Center for Stem Cell Research, School of Life Sciences and Technology, Tongji University, Shanghai, China
| | - Xiaolu Tai
- Department of Endocrinology and Metabolism, National Metabolic Management Center, Shanghai Tenth People's Hospital, Shanghai Key Laboratory of Signaling and Disease Research, Frontier Science Center for Stem Cell Research, School of Life Sciences and Technology, Tongji University, Shanghai, China
| | - Diliqingna Dilimulati
- Department of Endocrinology and Metabolism, National Metabolic Management Center, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai, China
| | - Xiaowei Lei
- Department of Endocrinology and Metabolism, National Metabolic Management Center, Shanghai Tenth People's Hospital, Shanghai Key Laboratory of Signaling and Disease Research, Frontier Science Center for Stem Cell Research, School of Life Sciences and Technology, Tongji University, Shanghai, China
| | - Jing Xu
- Department of Endocrinology and Metabolism, National Metabolic Management Center, Shanghai Tenth People's Hospital, Shanghai Key Laboratory of Signaling and Disease Research, Frontier Science Center for Stem Cell Research, School of Life Sciences and Technology, Tongji University, Shanghai, China
| | - Cong Zhang
- Department of Plastic and Reconstructive Surgery, Shanghai Institute of Precision Medicine, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yanbin Fu
- Department of Plastic and Reconstructive Surgery, Shanghai Institute of Precision Medicine, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Shen Qu
- Department of Endocrinology and Metabolism, National Metabolic Management Center, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai, China.
| | - Qingfeng Li
- Department of Plastic and Reconstructive Surgery, Shanghai Institute of Precision Medicine, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
| | - Chao Zhang
- Department of Plastic and Reconstructive Surgery, Shanghai Institute of Precision Medicine, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
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Kong JH, Young CB, Pusapati GV, Patel CB, Ho S, Krishnan A, Lin JHI, Devine W, Moreau de Bellaing A, Athni TS, Aravind L, Gunn TM, Lo CW, Rohatgi R. A Membrane-Tethered Ubiquitination Pathway Regulates Hedgehog Signaling and Heart Development. Dev Cell 2020; 55:432-449.e12. [PMID: 32966817 PMCID: PMC7686252 DOI: 10.1016/j.devcel.2020.08.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Revised: 07/23/2020] [Accepted: 08/27/2020] [Indexed: 12/30/2022]
Abstract
The etiology of congenital heart defects (CHDs), which are among the most common human birth defects, is poorly understood because of its complex genetic architecture. Here, we show that two genes implicated in CHDs, Megf8 and Mgrn1, interact genetically and biochemically to regulate the strength of Hedgehog signaling in target cells. MEGF8, a transmembrane protein, and MGRN1, a RING superfamily E3 ligase, assemble to form a receptor-like ubiquitin ligase complex that catalyzes the ubiquitination and degradation of the Hedgehog pathway transducer Smoothened. Homozygous Megf8 and Mgrn1 mutations increased Smoothened abundance and elevated sensitivity to Hedgehog ligands. While mice heterozygous for loss-of-function Megf8 or Mgrn1 mutations were normal, double heterozygous embryos exhibited an incompletely penetrant syndrome of CHDs with heterotaxy. Thus, genetic interactions can arise from biochemical mechanisms that calibrate morphogen signaling strength, a conclusion broadly relevant for the many human diseases in which oligogenic inheritance is emerging as a mechanism for heritability.
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Affiliation(s)
- Jennifer H Kong
- Departments of Biochemistry and Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Cullen B Young
- Department of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15201, USA
| | - Ganesh V Pusapati
- Departments of Biochemistry and Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Chandni B Patel
- Departments of Biochemistry and Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Sebastian Ho
- Department of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15201, USA
| | - Arunkumar Krishnan
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
| | - Jiuann-Huey Ivy Lin
- Department of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15201, USA
| | - William Devine
- Department of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15201, USA
| | - Anne Moreau de Bellaing
- Department of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15201, USA; Department of Pediatric Cardiology, Necker-Sick Children Hospital and The University of Paris Descartes, Paris 75015, France
| | - Tejas S Athni
- Departments of Biochemistry and Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - L Aravind
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
| | - Teresa M Gunn
- McLaughlin Research Institute, Great Falls, MT 59405, USA.
| | - Cecilia W Lo
- Department of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15201, USA.
| | - Rajat Rohatgi
- Departments of Biochemistry and Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA.
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Saeed S, Arslan M, Manzoor J, Din SM, Janjua QM, Ayesha H, Ain QT, Inam L, Lobbens S, Vaillant E, Durand E, Derhourhi M, Amanzougarene S, Badreddine A, Berberian L, Gaget S, Khan WI, Butt TA, Bonnefond A, Froguel P. Genetic Causes of Severe Childhood Obesity: A Remarkably High Prevalence in an Inbred Population of Pakistan. Diabetes 2020; 69:1424-1438. [PMID: 32349990 DOI: 10.2337/db19-1238] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Accepted: 04/25/2020] [Indexed: 11/13/2022]
Abstract
Monogenic forms of obesity have been identified in ≤10% of severely obese European patients. However, the overall spectrum of deleterious variants (point mutations and structural variants) responsible for childhood severe obesity remains elusive. In this study, we genetically screened 225 severely obese children from consanguineous Pakistani families through a combination of techniques, including an in-house-developed augmented whole-exome sequencing method (CoDE-seq) that enables simultaneous detection of whole-exome copy number variations (CNVs) and point mutations in coding regions. We identified 110 (49%) probands carrying 55 different pathogenic point mutations and CNVs in 13 genes/loci responsible for nonsyndromic and syndromic monofactorial obesity. CoDE-seq also identified 28 rare or novel CNVs associated with intellectual disability in 22 additional obese subjects (10%). Additionally, we highlight variants in candidate genes for obesity warranting further investigation. Altogether, 59% of cases in the studied cohort are likely to have a discrete genetic cause, with 13% of these as a result of CNVs, demonstrating a remarkably higher prevalence of monofactorial obesity than hitherto reported and a plausible overlapping of obesity and intellectual disabilities in several cases. Finally, inbred populations with a high prevalence of obesity provide unique, genetically enriched material in the quest of new genes/variants influencing energy balance.
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Affiliation(s)
- Sadia Saeed
- Université de Lille, INSERM UMR1283, CNRS-UMR 8199-European Genomic Institute for Diabetes, and Lille University Hospital, Lille, France
- Department of Metabolism, Digestion and Reproduction, Imperial College London, London, U.K
| | - Muhammad Arslan
- School of Life Sciences, Forman Christian College (A Chartered University), Lahore, Pakistan
| | - Jaida Manzoor
- Department of Paediatric Endocrinology, Children's Hospital, Lahore, Pakistan
| | - Sadia M Din
- Institute of Molecular Biology and Biotechnology, University of Lahore, Lahore, Pakistan
| | - Qasim M Janjua
- Institute of Molecular Biology and Biotechnology, University of Lahore, Lahore, Pakistan
- Department of Physiology, University College of Medicine and Dentistry, University of Lahore, Lahore, Pakistan
| | - Hina Ayesha
- Department of Paediatrics, Punjab Medical College, Faisalabad, Pakistan
| | - Qura-Tul Ain
- Institute of Molecular Biology and Biotechnology, University of Lahore, Lahore, Pakistan
| | - Laraib Inam
- School of Life Sciences, Forman Christian College (A Chartered University), Lahore, Pakistan
| | - Stephane Lobbens
- Université de Lille, INSERM UMR1283, CNRS-UMR 8199-European Genomic Institute for Diabetes, and Lille University Hospital, Lille, France
| | - Emmanuel Vaillant
- Université de Lille, INSERM UMR1283, CNRS-UMR 8199-European Genomic Institute for Diabetes, and Lille University Hospital, Lille, France
| | - Emmanuelle Durand
- Université de Lille, INSERM UMR1283, CNRS-UMR 8199-European Genomic Institute for Diabetes, and Lille University Hospital, Lille, France
| | - Mehdi Derhourhi
- Université de Lille, INSERM UMR1283, CNRS-UMR 8199-European Genomic Institute for Diabetes, and Lille University Hospital, Lille, France
| | - Souhila Amanzougarene
- Université de Lille, INSERM UMR1283, CNRS-UMR 8199-European Genomic Institute for Diabetes, and Lille University Hospital, Lille, France
| | - Alaa Badreddine
- Université de Lille, INSERM UMR1283, CNRS-UMR 8199-European Genomic Institute for Diabetes, and Lille University Hospital, Lille, France
| | - Lionel Berberian
- Université de Lille, INSERM UMR1283, CNRS-UMR 8199-European Genomic Institute for Diabetes, and Lille University Hospital, Lille, France
| | - Stefan Gaget
- Université de Lille, INSERM UMR1283, CNRS-UMR 8199-European Genomic Institute for Diabetes, and Lille University Hospital, Lille, France
| | - Waqas I Khan
- The Children Hospital and the Institute of Child Health, Multan, Pakistan
| | - Taeed A Butt
- Department of Pediatrics, Fatima Memorial Hospital, Lahore, Pakistan
| | - Amélie Bonnefond
- Université de Lille, INSERM UMR1283, CNRS-UMR 8199-European Genomic Institute for Diabetes, and Lille University Hospital, Lille, France
- Department of Metabolism, Digestion and Reproduction, Imperial College London, London, U.K
| | - Philippe Froguel
- Université de Lille, INSERM UMR1283, CNRS-UMR 8199-European Genomic Institute for Diabetes, and Lille University Hospital, Lille, France
- Department of Metabolism, Digestion and Reproduction, Imperial College London, London, U.K
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Maass PG, Glažar P, Memczak S, Dittmar G, Hollfinger I, Schreyer L, Sauer AV, Toka O, Aiuti A, Luft FC, Rajewsky N. A map of human circular RNAs in clinically relevant tissues. J Mol Med (Berl) 2017; 95:1179-1189. [PMID: 28842720 PMCID: PMC5660143 DOI: 10.1007/s00109-017-1582-9] [Citation(s) in RCA: 250] [Impact Index Per Article: 35.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2017] [Revised: 08/03/2017] [Accepted: 08/18/2017] [Indexed: 01/09/2023]
Abstract
Abstract Cellular circular RNAs (circRNAs) are generated by head-to-tail splicing and are present in all multicellular organisms studied so far. Recently, circRNAs have emerged as a large class of RNA which can function as post-transcriptional regulators. It has also been shown that many circRNAs are tissue- and stage-specifically expressed. Moreover, the unusual stability and expression specificity make circRNAs important candidates for clinical biomarker research. Here, we present a circRNA expression resource of 20 human tissues highly relevant to disease-related research: vascular smooth muscle cells (VSMCs), human umbilical vein cells (HUVECs), artery endothelial cells (HUAECs), atrium, vena cava, neutrophils, platelets, cerebral cortex, placenta, and samples from mesenchymal stem cell differentiation. In eight different samples from a single donor, we found highly tissue-specific circRNA expression. Circular-to-linear RNA ratios revealed that many circRNAs were expressed higher than their linear host transcripts. Among the 71 validated circRNAs, we noticed potential biomarkers. In adenosine deaminase-deficient, severe combined immunodeficiency (ADA-SCID) patients and in Wiskott-Aldrich-Syndrome (WAS) patients’ samples, we found evidence for differential circRNA expression of genes that are involved in the molecular pathogenesis of both phenotypes. Our findings underscore the need to assess circRNAs in mechanisms of human disease. Key messages circRNA resource catalog of 20 clinically relevant tissues. circRNA expression is highly tissue-specific. circRNA transcripts are often more abundant than their linear host RNAs. circRNAs can be differentially expressed in disease-associated genes.
Electronic supplementary material The online version of this article (10.1007/s00109-017-1582-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Philipp G Maass
- Experimental and Clinical Research Center (ECRC), a joint cooperation between the Charité Medical Faculty and the Max Delbrück Center for Molecular Medicine (MDC), Lindenberger Weg 80, 13125, Berlin, Germany. .,Max Delbrück Center for Molecular Medicine (MDC), Robert-Rössle-Strasse 10, 13125, Berlin, Germany. .,Department of Stem Cell and Regenerative Biology, Harvard University, 7 Divinity Ave, Cambridge, MA, 02138, USA.
| | - Petar Glažar
- Max Delbrück Center for Molecular Medicine (MDC), Robert-Rössle-Strasse 10, 13125, Berlin, Germany
| | - Sebastian Memczak
- Experimental and Clinical Research Center (ECRC), a joint cooperation between the Charité Medical Faculty and the Max Delbrück Center for Molecular Medicine (MDC), Lindenberger Weg 80, 13125, Berlin, Germany.,Max Delbrück Center for Molecular Medicine (MDC), Robert-Rössle-Strasse 10, 13125, Berlin, Germany
| | - Gunnar Dittmar
- Max Delbrück Center for Molecular Medicine (MDC), Robert-Rössle-Strasse 10, 13125, Berlin, Germany
| | - Irene Hollfinger
- Experimental and Clinical Research Center (ECRC), a joint cooperation between the Charité Medical Faculty and the Max Delbrück Center for Molecular Medicine (MDC), Lindenberger Weg 80, 13125, Berlin, Germany.,Max Delbrück Center for Molecular Medicine (MDC), Robert-Rössle-Strasse 10, 13125, Berlin, Germany
| | - Luisa Schreyer
- Max Delbrück Center for Molecular Medicine (MDC), Robert-Rössle-Strasse 10, 13125, Berlin, Germany
| | - Aisha V Sauer
- Scientific Institute HS Raffaele, San Raffaele Telethon Institute for Gene Therapy (SR-Tiget), 20132, Milan, Italy
| | - Okan Toka
- Department of Pediatric Cardiology, Children's Hospital, Friedrich-Alexander University Erlangen, Loschge Strasse 15, 91054, Erlangen, Germany.,The German Registry for Congenital Heart Defects, Augustenburger Platz 1, 13353, Berlin, Germany
| | - Alessandro Aiuti
- Scientific Institute HS Raffaele, San Raffaele Telethon Institute for Gene Therapy (SR-Tiget), 20132, Milan, Italy.,Vita Salute San Raffaele University, Milan, Italy
| | - Friedrich C Luft
- Experimental and Clinical Research Center (ECRC), a joint cooperation between the Charité Medical Faculty and the Max Delbrück Center for Molecular Medicine (MDC), Lindenberger Weg 80, 13125, Berlin, Germany.,Max Delbrück Center for Molecular Medicine (MDC), Robert-Rössle-Strasse 10, 13125, Berlin, Germany.,Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, 37235, USA
| | - Nikolaus Rajewsky
- Max Delbrück Center for Molecular Medicine (MDC), Robert-Rössle-Strasse 10, 13125, Berlin, Germany.
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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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Contribution of copy number variants (CNVs) to congenital, unexplained intellectual and developmental disabilities in Lebanese patients. Mol Cytogenet 2015; 8:26. [PMID: 25922617 PMCID: PMC4411788 DOI: 10.1186/s13039-015-0130-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 03/23/2015] [Indexed: 11/10/2022] Open
Abstract
Background Chromosomal microarray analysis (CMA) is currently the most widely adopted clinical test for patients with unexplained intellectual disability (ID), developmental delay (DD), and congenital anomalies. Its use has revealed the capacity to detect copy number variants (CNVs), as well as regions of homozygosity, that, based on their distribution on chromosomes, indicate uniparental disomy or parental consanguinity that is suggestive of an increased probability of recessive disease. Results We screened 149 Lebanese probands with ID/DD and 99 healthy controls using the Affymetrix Cyto 2.7 M and SNP6.0 arrays. We report all identified CNVs, which we divided into groups. Pathogenic CNVs were identified in 12.1% of the patients. We review the genotype/phenotype correlation in a patient with a 1q44 microdeletion and refine the minimal critical regions responsible for the 10q26 and 16q monosomy syndromes. Several likely causative CNVs were also detected, including new homozygous microdeletions (9p23p24.1, 10q25.2, and 8p23.1) in 3 patients born to consanguineous parents, involving potential candidate genes. However, the clinical interpretation of several other CNVs remains uncertain, including a microdeletion affecting ATRNL1. This CNV of unknown significance was inherited from the patient’s unaffected-mother; therefore, additional ethnically matched controls must be screened to obtain enough evidence for classification of this CNV. Conclusion This study has provided supporting evidence that whole-genome analysis is a powerful method for uncovering chromosomal imbalances, regardless of consanguinity in the parents of patients and despite the challenge presented by analyzing some CNVs. Electronic supplementary material The online version of this article (doi:10.1186/s13039-015-0130-y) contains supplementary material, which is available to authorized users.
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8
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Mul JD, Spruijt BM, Brakkee JH, Adan RAH. Melanocortin MC(4) receptor-mediated feeding and grooming in rodents. Eur J Pharmacol 2013; 719:192-201. [PMID: 23872405 DOI: 10.1016/j.ejphar.2013.04.060] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Revised: 03/27/2013] [Accepted: 04/03/2013] [Indexed: 02/04/2023]
Abstract
Decades ago it was recognized that the pharmacological profile of melanocortin ligands that stimulated grooming behavior in rats was strikingly similar to that of Xenopus laevis melanophore pigment dispersion. After cloning of the melanocortin MC1 receptor, expressed in melanocytes, and the melanocortin MC4 receptor, expressed mainly in brain, the pharmacological profiles of these receptors appeared to be very similar and it was demonstrated that these receptors mediate melanocortin-induced pigmentation and grooming respectively. Grooming is a low priority behavior that is concerned with care of body surface. Activation of central melanocortin MC4 receptors is also associated with meal termination, and continued postprandial stimulation of melanocortin MC4 receptors may stimulate natural postprandial grooming behavior as part of the behavioral satiety sequence. Indeed, melanocortins fail to suppress food intake or induce grooming behavior in melanocortin MC4 receptor-deficient rats. This review will focus on how melanocortins affect grooming behavior through the melanocortin MC4 receptor, and how melanocortin MC4 receptors mediate feeding behavior. This review also illustrates how melanocortins were the most likely candidates to mediate grooming and feeding based on the natural behaviors they induced.
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Affiliation(s)
- Joram D Mul
- Metabolic Diseases Institute, University of Cincinnati, 2170 East Galbraith Road, 45237 Cincinnati, Ohio, USA.
| | - Berry M Spruijt
- Department of Biology, Faculty of Beta Sciences, University of Utrecht, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Jan H Brakkee
- Rudolf Magnus Institute of Neuroscience, Department of Neuroscience and Pharmacology, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands
| | - Roger A H Adan
- Rudolf Magnus Institute of Neuroscience, Department of Neuroscience and Pharmacology, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands
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9
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Biebermann H, Kühnen P, Kleinau G, Krude H. The neuroendocrine circuitry controlled by POMC, MSH, and AGRP. Handb Exp Pharmacol 2012:47-75. [PMID: 22249810 DOI: 10.1007/978-3-642-24716-3_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Obesity is one of the most challenging health problems worldwide. Over the past few decades, our knowledge concerning mechanisms of weight regulation has increased tremendously leading to the identification of the leptin-melanocortin pathway. The filling level of energy stores is signaled to the brain, and the information is integrated by hypothalamic nuclei, resulting in a well-orchestrated response to food intake and energy expenditure to ensure constant body weight. One of the key players in this system is proopiomelanocortin (POMC), a precursor of a variety of neuropeptides. POMC-derived alpha- and beta-MSH play an important role in energy homeostasis by activating melanocortin receptors expressed in the arcuate nucleus (MC3R) and in the nucleus paraventricularis (MC4R). Activation of these two G protein-coupled receptors is antagonized by agouti-related peptide (AgRP). Naturally occurring mutations in this system were identified in patients suffering from common obesity as well as in patients demonstrating a phenotype of severe early-onset obesity, adrenal insufficiency, red hair, and pale skin. Detailed understanding of the complex system of POMC-AgRP-MC3R-MC4R and their interaction with other hypothalamic as well as peripheral signals is a prerequisite to combat the obesity epidemic.
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Affiliation(s)
- Heike Biebermann
- Institut für Experimentelle Pädiatrische Endokrinologie, Charité Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany.
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10
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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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11
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Cooray SN, Clark AJL. Melanocortin receptors and their accessory proteins. Mol Cell Endocrinol 2011; 331:215-21. [PMID: 20654690 DOI: 10.1016/j.mce.2010.07.015] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2010] [Revised: 05/11/2010] [Accepted: 07/13/2010] [Indexed: 01/09/2023]
Abstract
The melanocortin receptor family consists of 5 members which belong to the GPCR superfamily. Their specific ligands, the melanocortins are peptide hormones which are formed by the proteolytic cleavage of the proopiomelanocortin (POMC) protein. It is now recognised that certain GPCRs require accessory proteins for their function. Like these GPCRs the melanocortin receptor family is also known to be associated with accessory proteins that regulate their function. In this review we will summarise the accessory proteins involved in the function of the 5 melanocortin receptors and in particular focus on the melanocortin 2 receptor accessory protein (MRAP) which is crucial for the function of the MC2R.
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Affiliation(s)
- Sadani N Cooray
- Centre for Endocrinology, William Harvey Research Institute, Barts and the London, Queen Mary University of London, Charterhouse Square, London EC1 M 6BQ, UK
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12
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Stark Z, Bruno DL, Mountford H, Lockhart PJ, Amor DJ. De novo 325 kb microdeletion in chromosome band 10q25.3 including ATRNL1 in a boy with cognitive impairment, autism and dysmorphic features. Eur J Med Genet 2010; 53:337-9. [PMID: 20670697 DOI: 10.1016/j.ejmg.2010.07.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2010] [Accepted: 07/18/2010] [Indexed: 11/26/2022]
Abstract
We provide the first description of a patient with a heterozygous deletion of the Attractin-like (ATRNL1) gene. The patient presented with a novel and distinctive phenotype comprising dysmorphic facial appearance, ventricular septal defect, toe syndactyly, radioulnar synostosis, postnatal growth retardation, cognitive impairment with autistic features, and ataxia. A 325 kb de novo deletion in ATRNL1 was demonstrated using SNP microarray and confirmed by FISH analysis using BAC probes. Sequence analysis of the undeleted allele did not identify any alterations, suggesting that the phenotype was the result of haploinusfficiency. ATRNL1 and its paralog ATRN are highly conserved transmembrane proteins thought to be involved in cell adhesion and signalling events. The phenotype of mice with homozygous Atrn mutations overlaps considerably with the features observed in our patient. We therefore postulate that our patient's phenotype is caused by the deletion of ATRNL1, and provide further insight into the role of ATRNL1 in human development.
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13
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Walker WP, Gunn TM. Shades of meaning: the pigment-type switching system as a tool for discovery. Pigment Cell Melanoma Res 2010; 23:485-95. [PMID: 20465596 DOI: 10.1111/j.1755-148x.2010.00721.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The pigment-type switching system, which controls whether melanocytes produce black/brown eumelanin or yellow/red pheomelanin, is responsible for many familiar coat coloration patterns in both domestic and wild mammals. In conjunction with the accessory proteins attractin and mahogunin ring finger 1, endogenous agonists and antagonists modulate signaling by the melanocortin 1 receptor to determine pigment type. Mutations in pigment-type switching genes can cause a variety of pleiotropic phenotypes, and these are often similar between mutants at different loci because the proteins encoded by these genes act together as part of conserved molecular pathways that are deployed in multiple biological contexts. When this is the case, pigment-type switching provides a powerful model system for elucidating the shared molecular mechanisms underlying the pigmentary and non-pigmentary phenotypes. This review outlines the current understanding of the pigment-type switching pathway and discusses the opportunities that exist for exploring the molecular basis of pleiotropic phenotypes using this model system.
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Li J, Wang S, Huang S, Cheng D, Shen S, Xiong C. Attractin gene deficiency contributes to testis vacuolization and sperm dysfunction in male mice. ACTA ACUST UNITED AC 2009; 29:750-4. [DOI: 10.1007/s11596-009-0616-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2009] [Indexed: 02/03/2023]
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15
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Garfield AS, Lam DD, Marston OJ, Przydzial MJ, Heisler LK. Role of central melanocortin pathways in energy homeostasis. Trends Endocrinol Metab 2009; 20:203-15. [PMID: 19541496 DOI: 10.1016/j.tem.2009.02.002] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2008] [Revised: 02/06/2009] [Accepted: 02/06/2009] [Indexed: 02/07/2023]
Abstract
The rise in the global prevalence of human obesity has emphasized the need for a greater understanding of the physiological mechanisms that underlie energy homeostasis. Numerous circulating nutritional cues and central neuromodulatory signals are integrated within the brain to regulate both short- and long-term nutritional state. The central melanocortin system represents a crucial point of convergence for these signals and, thus, has a fundamental role in regulating body weight. The melanocortin ligands, synthesized in discrete neuronal populations within the hypothalamus and brainstem, modulate downstream homeostatic signalling via their action at central melanocortin-3 and -4 receptors. Intimately involved in both ingestive behaviour and energy expenditure, the melanocortin system has garnered much interest as a potential therapeutic target for human obesity.
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Affiliation(s)
- Alastair S Garfield
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, UK
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16
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Mouse models for the central melanocortin system. GENES AND NUTRITION 2009; 4:129-34. [PMID: 19266227 DOI: 10.1007/s12263-009-0117-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2009] [Accepted: 02/16/2009] [Indexed: 12/31/2022]
Abstract
Obesity is characterized by an excess storage of body fat and promotes the risk for complex disease traits such as diabetes mellitus and cardiovascular diseases. The obesity prevalence in Europe is rising and meanwhile ranges from 10 to 20% in men and 15-25% in women. Body fat accumulation occurs in states of positive energy balance and is favored by interactions among environmental, psychosocial and genetic factors. Energy balance is regulated by a complex neuronal network of anorexigenic and orexigenic neurons which integrates peripheral and central hormonal and neuronal signals relaying information on the metabolic status of organs and tissues in the body. A key component of this network is the central melanocortin pathway in the hypothalamus that elicits metabolic and behavioral adaptations for the maintenance of energy homeostasis. Genetic defects in this system cause obesity in mice and humans. In this review we emphasize mouse models with spontaneous natural mutations as well as targeted mutations that contributed to our understanding of the central melanocortin system function in the control of energy balance.
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17
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Tan K, Pogozheva ID, Yeo GSH, Hadaschik D, Keogh JM, Haskell-Leuvano C, O'Rahilly S, Mosberg HI, Farooqi IS. Functional characterization and structural modeling of obesity associated mutations in the melanocortin 4 receptor. Endocrinology 2009; 150:114-25. [PMID: 18801902 PMCID: PMC2732289 DOI: 10.1210/en.2008-0721] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Mutations in the melanocortin 4 receptor (MC4R) gene are the most common known cause of monogenic human obesity. The MC4R gene was sequenced in 2000 subjects with severe early-onset obesity. We detected seven different nonsense and 19 nonsynonymous mutations in a total of 94 probands, some of which have been reported previously by others. We functionally characterized the 11 novel obesity associated missense mutations. Seven of these mutants (L54P, E61K, I69T, S136P, M161T, T162I, and I269N) showed impaired cell surface trafficking, reduced level of maximal binding of the radioligand [125I]NDP-MSH, and reduced ability to generate cAMP in response to ligand. Four mutant MC4Rs (G55V, G55D, S136F, and A303T) displayed cell surface expression and agonist binding similar to the wild-type receptor but showed impaired cAMP production, suggesting that these residues are likely to be critical for conformational rearrangement essential for receptor activation. Homology modeling of these mutants using a model of MC4R based on the crystal structure of the beta2-adrenoreceptor was used to provide insights into the possible structural basis for receptor dysfunction. Transmembrane (TM) domains 1, 3, 6, 7, and peripheral helix 8 appear to participate in the agonist-induced conformational rearrangement necessary for coupling of ligand binding to signaling. We conclude that G55V, G55D, S136F, and A303T mutations are likely to strengthen helix-helix interactions between TM1 and TM2, TM3 and TM6, and TM7 and helix 8, respectively, preventing relative movement of these helices during receptor activation. The combination of functional studies and structural modeling of naturally occurring pathogenic mutations in MC4R can provide valuable information regarding the molecular mechanism of MC4R activation and its dysfunction in human disease.
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Affiliation(s)
- Karen Tan
- University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, Addenbrooke's Hospital, Box 289, Hills Road, Cambridge CB2 2QQ, United Kingdom
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18
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Vashlishan AB, Madison JM, Dybbs M, Bai J, Sieburth D, Ch'ng Q, Tavazoie M, Kaplan JM. An RNAi Screen Identifies Genes that Regulate GABA Synapses. Neuron 2008; 58:346-61. [DOI: 10.1016/j.neuron.2008.02.019] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2007] [Revised: 02/12/2008] [Accepted: 02/19/2008] [Indexed: 01/29/2023]
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19
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Walker WP, Aradhya S, Hu CL, Shen S, Zhang W, Azarani A, Lu X, Barsh GS, Gunn TM. Genetic analysis of attractin homologs. Genesis 2008; 45:744-56. [PMID: 18064672 DOI: 10.1002/dvg.20351] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Attractin (ATRN) and Attractin-like 1 (ATRNL1) are highly similar type I transmembrane proteins. Atrn null mutant mice have a pleiotropic phenotype including dark fur, juvenile-onset spongiform neurodegeneration, hypomyelination, tremor, and reduced body weight and adiposity, implicating ATRN in numerous biological processes. Bioinformatic analysis indicated that Atrn and Atrnl1 arose from a common ancestral gene early in vertebrate evolution. To investigate the genetics of the ATRN system and explore potential redundancy between Atrn and Atrnl1, we generated and characterized Atrnl1 loss- and gain-of-function mutations in mice. Atrnl1 mutant mice were grossly normal with no alterations of pigmentation, central nervous system pathology or body weight. Atrn null mutant mice carrying a beta-actin promoter-driven Atrnl1 transgene had normal, agouti-banded hairs and significantly delayed onset of spongiform neurodegeneration, indicating that over-expression of ATRNL1 compensates for loss of ATRN. Thus, the two genes are redundant from the perspective of gain-of-function but not loss-of-function mutations.
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Affiliation(s)
- Will P Walker
- Department of Biomedical Sciences, Cornell University, Ithaca, New York 14853, USA
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20
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Nakadate K, Sakakibara SI, Ueda S. Attractin/mahogany protein expression in the rodent central nervous system. J Comp Neurol 2008; 508:94-111. [DOI: 10.1002/cne.21662] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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21
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Azouz A, Gunn TM, Duke-Cohan JS. Juvenile-onset loss of lipid-raft domains in attractin-deficient mice. Exp Cell Res 2006; 313:761-71. [PMID: 17196964 DOI: 10.1016/j.yexcr.2006.11.018] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2006] [Revised: 11/09/2006] [Accepted: 11/27/2006] [Indexed: 11/29/2022]
Abstract
Mutations at the attractin (Atrn) locus in mice result in altered pigmentation on an agouti background, higher basal metabolic rate and juvenile-onset hypomyelination leading to neurodegeneration, while studies on human immune cells indicate a chemotaxis regulatory function. The underlying biochemical defect remains elusive. In this report we identify a role for attractin in plasma membrane maintenance. In attractin's absence there is a decline in plasma membrane glycolipid-enriched rafts from normal levels at 8 weeks to a complete absence by 24 weeks. The structural integrity of lipid rafts depends upon cholesterol and sphingomyelin, and can be identified by partitioning within of ganglioside GM(1). Despite a significant fall in cellular cholesterol with maturity, and a lesser fall in both membrane and total cellular GM(1), these parameters lag behind raft loss, and are normal when hypomyelination/neurodegeneration has already begun thus supporting consequence rather than cause. These findings can be recapitulated in Atrn-deficient cell lines propagated in vitro. Further, signal transduction through complex membrane receptor assemblies is not grossly disturbed despite the complete absence of lipid rafts. We find these results compatible with a role for attractin in plasma membrane maintenance and consistent with the proposal that the juvenile-onset hypomyelination and neurodegeneration represent a defect in attractin-mediated raft-dependent myelin biogenesis.
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Affiliation(s)
- Abdallah Azouz
- Department of Medical Oncology, Dana-Farber Cancer Institute, and Department of Medicine, Harvard Medical School, Boston, MA 02115, USA
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22
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Abstract
The melanocortin system refers to a set of hormonal, neuropeptidergic, and paracrine signaling pathways that are defined by components that include the five G protein-coupled melanocortin receptors; peptide agonists derived from the proopiomelanocortin preprohormone precursor; and the endogenous antagonists, agouti and agouti-related protein. This signaling system regulates a remarkably diverse array of physiological functions including pigmentation, adrenocortical steroidogenesis, energy homeostasis, natriuresis, erectile responses, energy homeostasis, and exocrine gland secretion. There are many complex and unique aspects of melanocortin signaling, such as the existence of endogenous antagonists, the agouti proteins, that act at three of the five melanocortin receptors. However, there is an aspect of melanocortin signaling that has facilitated highly reductionist approaches aimed at understanding the physiological functions of each receptor and peptide: in contrast to many peptides, the melanocortin agonists and antagonists are expressed in a limited number of very discrete locations. Similarly, the melanocortin receptors are also expressed in a limited number of discrete locations where they tend to be involved in rather circumscribed physiological functions. This review examines my laboratory's participation in the cloning of the melanocortin receptors and characterization of their physiological roles.
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Affiliation(s)
- Roger D Cone
- Center for the Study of Weight Regulation and Associated Disorders, and Vollum Institute, Oregon Health and Science University, Portland, Oregon 97239-3098, USA.
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23
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Forslin Aronsson S, Spulber S, Popescu LM, Winblad B, Post C, Oprica M, Schultzberg M. alpha-Melanocyte-stimulating hormone is neuroprotective in rat global cerebral ischemia. Neuropeptides 2006; 40:65-75. [PMID: 16414116 DOI: 10.1016/j.npep.2005.10.006] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2005] [Revised: 10/17/2005] [Accepted: 10/19/2005] [Indexed: 02/04/2023]
Abstract
The aim of the study was to investigate the effects of alpha-melanocyte-stimulating hormone (alpha-MSH), a tridecapeptide derived from proopiomelanocortin (POMC), on the neurodegeneration following global cerebral ischemia and reperfusion in the rat. The biological activities of alpha-MSH include inhibition of inflammatory responses and anti-pyretic effects. Male Sprague-Dawley rats were subjected to four-vessel occlusion (4-VO) global cerebral ischemia followed by reperfusion, and treated with alpha-MSH (intraperitoneally, i.p.) at 30 min, and 24, 48, 72 and 96 h post-ischemia. Stereological quantification of the pyramidal cells in the CA1 area of the hippocampus showed that the number of viable neurons in ischemic rats was 96,945+/-18,610 (means+/-SD) as compared to 183,156+/-49,935 in sham-operated rats (P<0.05). The number of viable neurons after treatment of ischemic rats with alpha-MSH was 162,829+/-34,757, i.e. significantly different from the number of viable neurons in ischemic rats injected with saline (P<0.01). Astrocyte proliferation due to the ischemic insult was markedly reduced by the treatment with alpha-MSH, and the loss in body weight was reduced by alpha-MSH. In conclusion, post-ischemic administration of alpha-MSH was found to provide neuroprotection in the CA1 pyramidal cell layer in the hippocampus, concomitant with a reduction in glial activation, indicating that alpha-MSH or mimetics thereof may have a potential in the treatment of stroke or other neurodegenerative diseases. Further studies will be required to define the post-ischemic time window for administration of alpha-MSH.
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Affiliation(s)
- Sa Forslin Aronsson
- Division of Experimental Geriatrics, Neurotec Department, Karolinska Institutet, Karolinska University Hospital, Novum, KFC, Level 4, SE-141 86 Stockholm, Sweden.
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24
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Pogozheva ID, Chai BX, Lomize AL, Fong TM, Weinberg DH, Nargund RP, Mulholland MW, Gantz I, Mosberg HI. Interactions of human melanocortin 4 receptor with nonpeptide and peptide agonists. Biochemistry 2005; 44:11329-41. [PMID: 16114870 PMCID: PMC2532597 DOI: 10.1021/bi0501840] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Specific interactions of human melanocortin-4 receptor (hMC4R) with its nonpeptide and peptide agonists were studied using alanine-scanning mutagenesis. The binding affinities and potencies of two synthetic, small-molecule agonists (THIQ, MB243) were strongly affected by substitutions in transmembrane alpha-helices (TM) 2, 3, 6, and 7 (residues Glu(100), Asp(122), Asp(126), Phe(261), His(264), Leu(265), and Leu(288)). In addition, a I129A mutation primarily affected the binding and potency of THIQ, while F262A, W258A, Y268A mutations impaired interactions with MB243. By contrast, binding affinity and potency of the linear peptide agonist NDP-MSH were substantially reduced only in D126A and H264A mutants. Three-dimensional models of receptor-ligand complexes with their agonists were generated by distance-geometry using the experimental, homology-based, and other structural constraints, including interhelical H-bonds and two disulfide bridges (Cys(40)-Cys(279), Cys(271)-Cys(277)) of hMC4R. In the models, all pharmacophore elements of small-molecule agonists are spatially overlapped with the corresponding key residues (His(6), d-Phe(7), Arg(8), and Trp(9)) of the linear peptide: their charged amine groups interact with acidic residues from TM2 and TM3, similar to His(6) and Arg(6) of NDP-MSH; their substituted piperidines mimic Trp(9) of the peptide and interact with TM5 and TM6, while the d-Phe aromatic rings of all three agonists contact with Leu(133), Trp(258), and Phe(261) residues.
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MESH Headings
- Amino Acid Sequence
- Binding Sites
- Cyclic AMP/pharmacology
- Humans
- Models, Molecular
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Peptides/pharmacology
- Piperazines/pharmacology
- Piperidines/pharmacology
- Protein Structure, Secondary
- Receptor, Melanocortin, Type 4/agonists
- Receptor, Melanocortin, Type 4/chemistry
- Receptor, Melanocortin, Type 4/drug effects
- Receptor, Melanocortin, Type 4/metabolism
- Recombinant Proteins/chemistry
- Recombinant Proteins/drug effects
- Recombinant Proteins/metabolism
- Rhodopsin/chemistry
- Sequence Alignment
- Sequence Homology, Amino Acid
- Transfection
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Affiliation(s)
- Irina D Pogozheva
- Department of Medicinal Chemistry, College of Pharmacy, University of Michigan, Ann Arbor, Michigan 48109, USA
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25
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Carroll L, Voisey J, van Daal A. Gene polymorphisms and their effects in the melanocortin system. Peptides 2005; 26:1871-85. [PMID: 15979205 DOI: 10.1016/j.peptides.2004.12.031] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2004] [Accepted: 12/08/2004] [Indexed: 12/22/2022]
Abstract
In addition to its role in human pigmentation, components of the melanocortin system regulate appetite, energy homeostasis and hormone production. Recent studies have suggested possible roles of this system in immunity, transmission of pain signals, and reproductive potential. A number of polymorphisms have been identified in genes of the melanocortin system and are associated with pigmentation in humans, as well as being causative of disorders of adrenal hormone production and obesity. This review gives an outline of these polymorphisms, their functional significance and possible application to or impact on diagnosis and pharmacotherapy based on melanocortin pathways.
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Affiliation(s)
- Levi Carroll
- CRC for Diagnostics, Level 5, Q Block, Queensland University of Technology, 2 George St, Brisbane 4000, Australia
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26
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Pritchard LE, White A. Agouti-related protein: more than a melanocortin-4 receptor antagonist? Peptides 2005; 26:1759-70. [PMID: 15996791 DOI: 10.1016/j.peptides.2004.11.036] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2004] [Accepted: 11/16/2004] [Indexed: 01/08/2023]
Abstract
It is well established that agouti-related protein (AGRP) can act as a competitive antagonist to proopiomelanocortin (POMC)-derived peptides at the melanocortin-4 receptor (MC4R), and that this homeostatic mechanism is important as a means of coordinating appetite with perceived metabolic requirement. However, there are clearly additional facets to the physiological role of AGRP, given that it is active in MC4R knockout mice and it has strikingly long-lasting effects on food intake, compared with MC4R agonists. In this review we focus on: (i) evidence that AGRP is more sensitive to perturbations in energy balance than POMC and is therefore the primary basis of melanocortinergic regulation. (ii) Evidence that the bioactive peptide AGRP83-132, acts by alternate mechanism(s) to elicit its long-term effects on food intake. (iii) Evidence that AGRP is post-translationally cleaved to generate AGRP83-132 and one or more N terminal peptides, which may have an important physiological role(s) that are independent of the melanocortin system. A clear understanding of how proAGRP processing is regulated, and the role of resultant peptides, may define additional therapeutic targets in the treatment of obesity.
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Affiliation(s)
- Lynn E Pritchard
- School of Biological Sciences, University of Manchester, Stopford Building, Oxford Road, Manchester M13 9PT, UK
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27
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Hoggard N, Johnstone AM, Faber P, Gibney ER, Elia M, Lobley G, Rayner V, Horgan G, Hunter L, Bashir S, Stubbs RJ. Plasma concentrations of alpha-MSH, AgRP and leptin in lean and obese men and their relationship to differing states of energy balance perturbation. Clin Endocrinol (Oxf) 2004; 61:31-9. [PMID: 15212642 DOI: 10.1111/j.1365-2265.2004.02056.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
OBJECTIVE A great deal of attention has focused on the central role of alpha melanocyte-stimulating hormone (alpha-MSH) and its antagonism at the melanocortin-4 receptor (MC4R) by agouti related protein (AgRP) in the regulation of energy balance. However, very little is known regarding the function of circulating AgRP and alpha-MSH in humans. We aimed to determine whether circulating alpha-MSH and AgRP are responsive to long-term perturbations in energy balance, in a manner consistent with their central putative functions. DESIGN AND MEASUREMENTS Circulating alpha-MSH, AgRP and leptin were measured in both lean (n = 11) and obese (n = 18) male volunteers, some of whom (lean n = 11, obese n = 12) were then allocated one of two weight-loss dietary strategies to achieve about 5% weight loss. This was achieved by either total starvation (for 4-6 days) for rapid weight loss or a very low calorie diet (VLCD, 2.6 MJ/day) (11-12 days) for less rapid weight loss, in both the lean and obese volunteers. RESULTS At baseline, prior to any weight loss both plasma alpha-MSH (15.8 +/- 1.2 vs. 5.8 +/- 1.0 pmol/l +/- SEM; P < 0.001) and AgRP (49.4 +/- 2.4 vs. 10.1 +/- 0.9 pg/ml +/- SEM; P < 0.001) were elevated in obese subjects compared with lean. In both cases this correlated closely with fat mass (P < 0.001), percentage body fat (P < 0.001) and leptin (P < 0.05). Plasma AgRP increased significantly during a 6-day fast in lean individuals (11.1 +/- 1.6 vs. 21.6 +/- 3.1 pg/ml +/- SEM; P < 0.05) but not in the VLCD subjects or in the obese, while alpha-MSH was not affected by any changes in energy balance in either the lean or the obese volunteers. CONCLUSION We show a difference in alpha-MSH and AgRP in lean and obese subjects that correlates closely with body fat at baseline. We demonstrate an increase in plasma AgRP during a 6-day fast in lean individuals that is coincident with a decrease in plasma leptin. This increase in AgRP was not due to weight loss per se as there was no change in AgRP as a result of the same weight loss in the VLCD intervention in lean individuals. The source of the increase in plasma AgRP and its physiological function in the periphery remains to be elucidated but we suggest that the dynamics of the change in plasma leptin may determine the elevation in fasting plasma AgRP in lean subjects.
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