1
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Okamoto HH, Cecon E, Nureki O, Rivara S, Jockers R. Melatonin receptor structure and signaling. J Pineal Res 2024; 76:e12952. [PMID: 38587234 DOI: 10.1111/jpi.12952] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Revised: 02/05/2024] [Accepted: 03/24/2024] [Indexed: 04/09/2024]
Abstract
Melatonin (5-methoxy-N-acetyltryptamine) binds with high affinity and specificity to membrane receptors. Several receptor subtypes exist in different species, of which the mammalian MT1 and MT2 receptors are the best-characterized. They are members of the G protein-coupled receptor superfamily, preferentially coupling to Gi/o proteins but also to other G proteins in a cell-context-depending manner. In this review, experts on melatonin receptors will summarize the current state of the field. We briefly report on the discovery and classification of melatonin receptors, then focus on the molecular structure of human MT1 and MT2 receptors and highlight the importance of molecular simulations to identify new ligands and to understand the structural dynamics of these receptors. We then describe the state-of-the-art of the intracellular signaling pathways activated by melatonin receptors and their complexes. Brief statements on the molecular toolbox available for melatonin receptor studies and future perspectives will round-up this review.
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Affiliation(s)
- Hiroyuki H Okamoto
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan
| | - Erika Cecon
- Université Paris Cité, Institut Cochin, INSERM, CNRS, Paris, France
| | - Osamu Nureki
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan
| | - Silvia Rivara
- Department of Food and Drug, University of Parma, Parma, Italy
| | - Ralf Jockers
- Université Paris Cité, Institut Cochin, INSERM, CNRS, Paris, France
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2
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Nikolaev G, Robeva R, Konakchieva R. Membrane Melatonin Receptors Activated Cell Signaling in Physiology and Disease. Int J Mol Sci 2021; 23:ijms23010471. [PMID: 35008896 PMCID: PMC8745360 DOI: 10.3390/ijms23010471] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 12/28/2021] [Accepted: 12/29/2021] [Indexed: 02/07/2023] Open
Abstract
The pineal hormone melatonin has attracted great scientific interest since its discovery in 1958. Despite the enormous number of basic and clinical studies the exact role of melatonin in respect to human physiology remains elusive. In humans, two high-affinity receptors for melatonin, MT1 and MT2, belonging to the family of G protein-coupled receptors (GPCRs) have been cloned and identified. The two receptor types activate Gi proteins and MT2 couples additionally to Gq proteins to modulate intracellular events. The individual effects of MT1 and MT2 receptor activation in a variety of cells are complemented by their ability to form homo- and heterodimers, the functional relevance of which is yet to be confirmed. Recently, several melatonin receptor genetic polymorphisms were discovered and implicated in pathology-for instance in type 2 diabetes, autoimmune disease, and cancer. The circadian patterns of melatonin secretion, its pleiotropic effects depending on cell type and condition, and the already demonstrated cross-talks of melatonin receptors with other signal transduction pathways further contribute to the perplexity of research on the role of the pineal hormone in humans. In this review we try to summarize the current knowledge on the membrane melatonin receptor activated cell signaling in physiology and pathology and their relevance to certain disease conditions including cancer.
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Affiliation(s)
- Georgi Nikolaev
- Faculty of Biology, Sofia University “St. Kliment Ohridski”, 1504 Sofia, Bulgaria;
- Correspondence:
| | - Ralitsa Robeva
- Department of Endocrinology, Faculty of Medicine, Medical University, 1431 Sofia, Bulgaria;
| | - Rossitza Konakchieva
- Faculty of Biology, Sofia University “St. Kliment Ohridski”, 1504 Sofia, Bulgaria;
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3
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Nakamura Y, Asama R, Tabata T, Morita K, Maruyama T, Kondo A, Ishii J. Comparative analyses of site-directed mutagenesis of human melatonin MTNR1A and MTNR1B receptors using a yeast fluorescent biosensor. Biotechnol Bioeng 2020; 118:863-876. [PMID: 33095446 DOI: 10.1002/bit.27609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 10/22/2020] [Accepted: 10/22/2020] [Indexed: 11/08/2022]
Abstract
Melatonin is an indoleamine neurohormone made by the pineal gland. Its receptors, MTNR1A and MTNR1B, are members of the G-protein-coupled receptor (GPCR) family and are involved in sleep, circadian rhythm, and mood disorders, and in the inhibition of cancer growth. These receptors, therefore, represent significant molecular targets for insomnia, circadian sleep disorders, and cancer. The yeast Saccharomyces cerevisiae is an attractive host for assaying agonistic activity for human GPCR. We previously constructed a GPCR-based biosensor employing a high-sensitivity yeast strain that incorporated both a chimeric yeast-human Gα protein and a bright fluorescent reporter gene (ZsGreen). Similar approaches have been used for simple and convenient measurements of various GPCR activities. In the current study, we constructed a fluorescence-based yeast biosensor for monitoring the signaling activation of human melatonin receptors. We used this system to analyze point mutations, including previously unreported mutations of the consensus sequences of MTNR1A and MTNR1B melatonin receptors and compared their effects. Most mutations in the consensus sequences significantly affected the signaling capacities of both receptors, but several mutations showed differences between these subtype receptors. Thus, this yeast biosensor holds promise for revealing the functions of melatonin receptors.
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Affiliation(s)
- Yasuyuki Nakamura
- Engineering Biology Research Center, Kobe University, Kobe, Japan.,Graduate School of Science, Technology and Innovation, Kobe University, Kobe, Japan
| | - Ririka Asama
- Graduate School of Science, Technology and Innovation, Kobe University, Kobe, Japan
| | - Takuya Tabata
- Graduate School of Science, Technology and Innovation, Kobe University, Kobe, Japan
| | - Kenta Morita
- Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, Kobe, Japan
| | - Tatsuo Maruyama
- Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, Kobe, Japan
| | - Akihiko Kondo
- Engineering Biology Research Center, Kobe University, Kobe, Japan.,Graduate School of Science, Technology and Innovation, Kobe University, Kobe, Japan.,Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, Kobe, Japan.,Center for Sustainable Resource Science, RIKEN, Yokohama, Japan
| | - Jun Ishii
- Engineering Biology Research Center, Kobe University, Kobe, Japan.,Graduate School of Science, Technology and Innovation, Kobe University, Kobe, Japan
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4
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Chan KH, Tse LH, Huang X, Wong YH. Molecular basis defining the selectivity of substituted isoquinolinones for the melatonin MT 2 receptor. Biochem Pharmacol 2020; 177:114020. [PMID: 32389636 DOI: 10.1016/j.bcp.2020.114020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Accepted: 05/04/2020] [Indexed: 10/24/2022]
Abstract
Melatonin MT1 and MT2 receptors represent attractive drug targets for the treatment of various disorders. However, the high conservation of the melatonin binding pocket has hindered the development of subtype-selective compounds. By leveraging on the recently resolved crystal structures of MT1 and MT2 receptors, this study aims to elucidate the structural basis of MT2-selectivity of a panel of isoquinolinone derivatives. Molecular modelling and ligand docking approaches were employed to predict residues involved in forming interactions with the MT2-selective isoquinolinones. Seven conserved residues (Asn175, His208, Trp264, Asn268, Gly271, Tyr294 and Tyr298) were selected as targets for site-directed mutagenesis. Ca2+ mobilization, cAMP inhibition, phosphorylation of extracellular signal-regulated kinase, and ligand binding assays were performed to functionally characterize the receptor mutants in transfected CHO cells. Unlike melatonin, isoquinolinones bearing a 3-methoxybenzyloxyl substituent were unaffected by alanine substitution at His208 of MT2. Although alanine substitutions at Tyr294 or Tyr298 reduced the potency of melatonin and some isoquinolinones on MT2, similar mutations on MT1 allowed five hitherto ineffective isoquinolinones to act as agonists. An isoquinolinone antagonist bearing a 4-methoxybenzyloxyl moiety turned into an agonist at MT2 mutants with alanine substitutions at His208, Tyr294 or Tyr298. A subset of residues is apparently involved in forming a hydrophobic binding cavity to confer selectivity upon the aromatic substituent of isoquinolinone compounds. Two conserved tyrosine residues on transmembrane helix 7 may confer ligand selectivity at MT1 and MT2 receptors, while a conserved histidine on transmembrane helix 5 is apparently involved in receptor activation.
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Affiliation(s)
- King H Chan
- Division of Life Science and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Lap H Tse
- Division of Life Science and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Xuhui Huang
- Department of Chemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China; State Key Laboratory of Molecular Neuroscience, and the Molecular Neuroscience Center, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Yung H Wong
- Division of Life Science and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China; State Key Laboratory of Molecular Neuroscience, and the Molecular Neuroscience Center, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
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5
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Stauch B, Johansson LC, Cherezov V. Structural insights into melatonin receptors. FEBS J 2019; 287:1496-1510. [PMID: 31693784 DOI: 10.1111/febs.15128] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Revised: 10/16/2019] [Accepted: 11/05/2019] [Indexed: 12/22/2022]
Abstract
The long-anticipated high-resolution structures of the human melatonin G protein-coupled receptors MT1 and MT2 , involved in establishing and maintaining circadian rhythm, were obtained in complex with two melatonin analogs and two approved anti-insomnia and antidepression drugs using X-ray free-electron laser serial femtosecond crystallography. The structures shed light on the overall conformation and unusual structural features of melatonin receptors, as well as their ligand binding sites and the melatonergic pharmacophore, thereby providing insights into receptor subtype selectivity. The structures revealed an occluded orthosteric ligand binding site with a membrane-buried channel for ligand entry in both receptors, and an additional putative ligand entry path in MT2 from the extracellular side. This unexpected ligand entry mode contributes to facilitating the high specificity with which melatonin receptors bind their cognate ligand and exclude structurally similar molecules such as serotonin, the biosynthetic precursor of melatonin. Finally, the MT2 structure allowed accurate mapping of type 2 diabetes-related single-nucleotide polymorphisms, where a clustering of residues in helices I and II on the protein-membrane interface was observed which could potentially influence receptor oligomerization. The role of receptor oligomerization is further discussed in light of the differential interaction of MT1 and MT2 with GPR50, a regulatory melatonin coreceptor. The melatonin receptor structures will facilitate design of selective tool compounds to further dissect the specific physiological function of each receptor subtype as well as provide a structural basis for next-generation sleeping aids and other drugs targeting these receptors with higher specificity and fewer side effects.
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Affiliation(s)
- Benjamin Stauch
- Bridge Institute, USC Michelson Center for Convergent Biosciences, University of Southern California, Los Angeles, CA, USA.,Department of Chemistry, University of Southern California, Los Angeles, CA, USA
| | - Linda C Johansson
- Bridge Institute, USC Michelson Center for Convergent Biosciences, University of Southern California, Los Angeles, CA, USA.,Department of Chemistry, University of Southern California, Los Angeles, CA, USA
| | - Vadim Cherezov
- Bridge Institute, USC Michelson Center for Convergent Biosciences, University of Southern California, Los Angeles, CA, USA.,Department of Chemistry, University of Southern California, Los Angeles, CA, USA.,Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA
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6
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Alkozi HA, Sánchez Montero JM, Doadrio AL, Pintor J. Docking studies for melatonin receptors. Expert Opin Drug Discov 2017; 13:241-248. [PMID: 29271261 DOI: 10.1080/17460441.2018.1419184] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
INTRODUCTION Melatonin is a neurohormone that controls many relevant physiological processes beyond the control of circadian rhythms. Melatonin's actions are carried out by two main types of melatonin receptors; MT1 and MT2. These receptors are important, and not just because of the biological actions of its natural agonist; but also, because melatonin analogues can improve or antagonize their biological effect. Area covered: The following article describes the importance of melatonin as a biologically relevant molecule. It also defines the receptors for this substance, as well as the second messengers coupled to these receptors. Lastly, the article describes the amino acid residues involved in the docking process in both MT1 and MT2 melatonin receptors. Expert opinion: The biological actions of melatonin and their interpretations are becoming more relevant and therefore require the development of new pharmacological tools. Understanding the second messenger mechanisms involved in melatonin actions, as well as the characteristics of the docking of this molecule to MT1 and MT2 melatonin receptors, will permit the development of more selective agonists and antagonists which will help us to better understand this molecule as well to develop new therapeutic compounds.
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Affiliation(s)
- Hanan Awad Alkozi
- a Department of Biochemistry and Molecular Biology IV, Faculty of Optometry , Universidad Complutense de Madrid , Madrid , Spain
| | - José Maria Sánchez Montero
- b Department of Organic Chemistry and Pharmaceutical, Faculty of Pharmacy , Ciudad Universitaria , Madrid , Spain
| | - Antonio Luis Doadrio
- c Department of Inorganic Chemistry and Bioorganic, Faculty of Pharmacy , University Complutense of Madrid , Ciudad Universitaria, Madrid , Spain
| | - Jesus Pintor
- a Department of Biochemistry and Molecular Biology IV, Faculty of Optometry , Universidad Complutense de Madrid , Madrid , Spain
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7
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Jockers R, Delagrange P, Dubocovich ML, Markus RP, Renault N, Tosini G, Cecon E, Zlotos DP. Update on melatonin receptors: IUPHAR Review 20. Br J Pharmacol 2016; 173:2702-25. [PMID: 27314810 DOI: 10.1111/bph.13536] [Citation(s) in RCA: 272] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Revised: 05/15/2016] [Accepted: 05/19/2016] [Indexed: 02/06/2023] Open
Abstract
Melatonin receptors are seven transmembrane-spanning proteins belonging to the GPCR superfamily. In mammals, two melatonin receptor subtypes exist - MT1 and MT2 - encoded by the MTNR1A and MTNR1B genes respectively. The current review provides an update on melatonin receptors by the corresponding subcommittee of the International Union of Basic and Clinical Pharmacology. We will highlight recent developments of melatonin receptor ligands, including radioligands, and give an update on the latest phenotyping results of melatonin receptor knockout mice. The current status and perspectives of the structure of melatonin receptor will be summarized. The physiological importance of melatonin receptor dimers and biologically important and type 2 diabetes-associated genetic variants of melatonin receptors will be discussed. The role of melatonin receptors in physiology and disease will be further exemplified by their functions in the immune system and the CNS. Finally, antioxidant and free radical scavenger properties of melatonin and its relation to melatonin receptors will be critically addressed.
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Affiliation(s)
- Ralf Jockers
- Inserm, U1016, Institut Cochin, Paris, France.,CNRS UMR 8104, Paris, France.,University Paris Descartes, Paris, France
| | | | - Margarita L Dubocovich
- Department Pharmacology and Toxicology, Jacobs School of Medicine and Biomedical Science, University at Buffalo (SUNY), Buffalo, USA
| | - Regina P Markus
- Institute of Biosciences, University of São Paulo, São Paulo, Brazil
| | | | - Gianluca Tosini
- Neuroscience Institute and Department of Pharmacology and Toxicology, Morehouse School of Medicine, Atlanta, GA, USA
| | - Erika Cecon
- Inserm, U1016, Institut Cochin, Paris, France.,CNRS UMR 8104, Paris, France.,University Paris Descartes, Paris, France
| | - Darius P Zlotos
- Department of Pharmaceutical Chemistry, The German University in Cairo, New Cairo City, Cairo, Egypt
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8
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Jamaluddin JL, Huri HZ, Vethakkan SR, Mustafa N. Pancreatic gene variants potentially associated with dipeptidyl peptidase-4 inhibitor treatment response in Type 2 diabetes. Pharmacogenomics 2015; 15:235-49. [PMID: 24444412 DOI: 10.2217/pgs.13.234] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
In the adult pancreas, the expression of the genes PAX4, KCNQ1, TCF7L2, KCNJ11, ABCC8, MTNR1B and WFS1 are mainly restricted to β cells to maintain glucose homeostasis. We have identified these genes as the main regulators of incretin-mediated actions, and therefore they may potentially influence the response of DPP-4 inhibitors. This review represents the first detailed exploration of pancreatic β-cell genes and their variant mechanisms, which could potentially affect the response of DPP-4 inhibitors in Type 2 diabetes. We have focused on the signaling pathways of these genes to understand their roles in gastrointestinal incretin-mediated effects; and finally, we sought to associate gene mechanisms with their Type 2 diabetes risk variants to predict the responses of DPP-4 inhibitors for this disease.
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Affiliation(s)
- Jazlina Liza Jamaluddin
- Department of Pharmacy, Faculty of Medicine, University of Malaya, 50603, Kuala Lumpur, Malaysia
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9
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Hu Y, Chan KH, He X, Ho MKC, Wong YH. Synthesis and functional characterization of substituted isoquinolinones as MT2-selective melatoninergic ligands. PLoS One 2014; 9:e113638. [PMID: 25479338 PMCID: PMC4257560 DOI: 10.1371/journal.pone.0113638] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Accepted: 10/27/2014] [Indexed: 12/15/2022] Open
Abstract
A series of substituted isoquinolinones were synthesized and their binding affinities and functional activities towards human melatonin MT1 and MT2 receptors were evaluated. Structure-activity relationship analysis revealed that substituted isoquinolinones bearing a 3-methoxybenzyloxyl group at C5, C6 or C7 position respectively (C5>C6>C7 in terms of their potency) conferred effective binding and selectivity toward the MT2 receptor, with 15b as the most potent compound. Most of the tested compounds were MT2-selective agonists as revealed in receptor-mediated cAMP inhibition, intracellular Ca2+ mobilization and phosphorylation of extracellular signal-regulated protein kinases. Intriguingly, compounds 7e and 7f bearing a 4-methoxybenzyloxyl group or 4-methylbenzyloxyl at C6 behaved as weak MT2-selective antagonists. These results suggest that substituted isoquinolinones represent a novel family of MT2-selective melatonin ligands. The position of the substituted benzyloxyl group, and the substituents on the benzyl ring appeared to dictate the functional characteristics of these compounds.
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MESH Headings
- Animals
- CHO Cells
- Cricetulus
- Drug Design
- Humans
- Isoquinolines/chemical synthesis
- Isoquinolines/chemistry
- Ligands
- Melatonin/chemistry
- Melatonin/metabolism
- Phosphorylation
- Protein Binding
- Receptor, Melatonin, MT1/antagonists & inhibitors
- Receptor, Melatonin, MT1/chemistry
- Receptor, Melatonin, MT1/metabolism
- Receptor, Melatonin, MT2/antagonists & inhibitors
- Receptor, Melatonin, MT2/chemistry
- Receptor, Melatonin, MT2/metabolism
- Structure-Activity Relationship
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Affiliation(s)
- Yueqing Hu
- Division of Life Science and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
| | - King H. Chan
- Division of Life Science and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
| | - Xixin He
- Division of Life Science and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
| | - Maurice K. C. Ho
- Division of Life Science and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
| | - Yung H. Wong
- Division of Life Science and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
- State Key Laboratory of Molecular Neuroscience, and the Molecular Neuroscience Center, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
- * E-mail:
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10
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Zlotos DP, Jockers R, Cecon E, Rivara S, Witt-Enderby PA. MT1 and MT2 Melatonin Receptors: Ligands, Models, Oligomers, and Therapeutic Potential. J Med Chem 2013; 57:3161-85. [DOI: 10.1021/jm401343c] [Citation(s) in RCA: 114] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Darius. P. Zlotos
- Department
of Pharmaceutical Chemistry, The German University in Cairo, New Cairo City, 11835 Cairo, Egypt
| | - Ralf Jockers
- Inserm, U1016,
Institut Cochin, Paris, France
- CNRS UMR
8104, Paris, France
- Univ. Paris Descartes, Sorbonne Paris Cite, Paris, France
| | - Erika Cecon
- Department
of Physiology, Institute of Bioscience, University of Sao Paulo, Sao Paulo 05508-090, Brazil
| | - Silvia Rivara
- Dipartimento
di Farmacia, Università degli Studi di Parma, Parco Area
delle Scienze 27/A, 43124 Parma, Italy
| | - Paula A. Witt-Enderby
- Division
of Pharmaceutical Sciences, School of Pharmacy, Duquesne University, 421 Mellon Hall, Pittsburgh, Pennsylvania 15282, United States
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11
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Chan KH, Wong YH. A molecular and chemical perspective in defining melatonin receptor subtype selectivity. Int J Mol Sci 2013; 14:18385-406. [PMID: 24018885 PMCID: PMC3794785 DOI: 10.3390/ijms140918385] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2013] [Revised: 07/16/2013] [Accepted: 08/26/2013] [Indexed: 12/15/2022] Open
Abstract
Melatonin is primarily synthesized and secreted by the pineal gland during darkness in a normal diurnal cycle. In addition to its intrinsic antioxidant property, the neurohormone has renowned regulatory roles in the control of circadian rhythm and exerts its physiological actions primarily by interacting with the G protein-coupled MT1 and MT2 transmembrane receptors. The two melatonin receptor subtypes display identical ligand binding characteristics and mediate a myriad of signaling pathways, including adenylyl cyclase inhibition, phospholipase C stimulation and the regulation of other effector molecules. Both MT1 and MT2 receptors are widely expressed in the central nervous system as well as many peripheral tissues, but each receptor subtype can be linked to specific functional responses at the target tissue. Given the broad therapeutic implications of melatonin receptors in chronobiology, immunomodulation, endocrine regulation, reproductive functions and cancer development, drug discovery and development programs have been directed at identifying chemical molecules that bind to the two melatonin receptor subtypes. However, all of the melatoninergics in the market act on both subtypes of melatonin receptors without significant selectivity. To facilitate the design and development of novel therapeutic agents, it is necessary to understand the intrinsic differences between MT1 and MT2 that determine ligand binding, functional efficacy, and signaling specificity. This review summarizes our current knowledge in differentiating MT1 and MT2 receptors and their signaling capacities. The use of homology modeling in the mapping of the ligand-binding pocket will be described. Identification of conserved and distinct residues will be tremendously useful in the design of highly selective ligands.
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MESH Headings
- Animals
- Humans
- Melatonin/metabolism
- Receptor, Melatonin, MT1/chemistry
- Receptor, Melatonin, MT1/metabolism
- Receptor, Melatonin, MT2/chemistry
- Receptor, Melatonin, MT2/metabolism
- Receptors, Melatonin/chemistry
- Receptors, Melatonin/metabolism
- Signal Transduction
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Affiliation(s)
- King Hang Chan
- Biotechnology Research Institute, State Key Laboratory of Molecular Neuroscience, Division of Life Science, The Hong Kong University of Science and Technology, Hong Kong.
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12
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Ouzir M, Bouhaddou N, Khalki H, Lakhdar-Ghazal N. Physiological and pharmacological properties of 5-methoxytryptophol. Expert Rev Endocrinol Metab 2013; 8:355-364. [PMID: 30736152 DOI: 10.1586/17446651.2013.811866] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
5-methoxytryptophol (5-ML) is a pineal indoleamine derived from serotonin shown to be biologically active in a number of species. This indolamine exhibits a circadian pattern synchronized with the day-night cycle with significant increases during daylight, already recognized in vertebrates. The multiplicity of physiological and endocrine functions of 5-ML is remarkable; it is involved in circadian rhythms, reproduction and sexual processes. Furthermore, a number of pharmacological benefits of 5-ML have been reported, including immunomodulatory, antitumor and antioxidative activities. However, the molecular mechanisms of these pharmacological effects remain unclear. The purpose of this article is to provide an overview on the general properties and physiological functions of 5-ML. An attempt has been made to fully document all studies performed using 5-ML. In addition, this article aims to gain insight into the current state of knowledge regarding pharmacological and therapeutic effects of this indoleamine.
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Affiliation(s)
- Mounir Ouzir
- a Faculty of Medicine and Pharmacy, University Hassan II, Casablanca, Morocco.
| | - Nezha Bouhaddou
- b Unit of Research on Biological Rhythms and Environment, Faculty of Sciences University Mohammed V, Rabat, Morocco
| | - Hanane Khalki
- c Department of Biology, Laboratory of Pharmacology, Neurobiology and Behavior, Faculty of Sciences Semlalia University Cady Ayyad, Marrakech, Morocco
| | - Nouria Lakhdar-Ghazal
- b Unit of Research on Biological Rhythms and Environment, Faculty of Sciences University Mohammed V, Rabat, Morocco
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13
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Homology models of melatonin receptors: challenges and recent advances. Int J Mol Sci 2013; 14:8093-121. [PMID: 23584026 PMCID: PMC3645733 DOI: 10.3390/ijms14048093] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Revised: 03/28/2013] [Accepted: 03/28/2013] [Indexed: 12/15/2022] Open
Abstract
Melatonin exerts many of its actions through the activation of two G protein-coupled receptors (GPCRs), named MT1 and MT2. So far, a number of different MT1 and MT2 receptor homology models, built either from the prototypic structure of rhodopsin or from recently solved X-ray structures of druggable GPCRs, have been proposed. These receptor models differ in the binding modes hypothesized for melatonin and melatonergic ligands, with distinct patterns of ligand-receptor interactions and putative bioactive conformations of ligands. The receptor models will be described, and they will be discussed in light of the available information from mutagenesis experiments and ligand-based pharmacophore models. The ability of these ligand-receptor complexes to rationalize structure-activity relationships of known series of melatonergic compounds will be commented upon.
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14
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Pala D, Beuming T, Sherman W, Lodola A, Rivara S, Mor M. Structure-based virtual screening of MT2 melatonin receptor: influence of template choice and structural refinement. J Chem Inf Model 2013; 53:821-35. [PMID: 23541165 DOI: 10.1021/ci4000147] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Developing GPCR homology models for structure-based virtual screening requires the choice of a suitable template and refinement of binding site residues. We explored this systematically for the MT2 melatonin receptor, with the aim to build a receptor homology model that is optimized for the enrichment of active melatoninergic ligands. A set of 12 MT2 melatonin receptor models was built using different GPCR X-ray structural templates and submitted to a virtual screening campaign on a set of compounds composed of 29 known melatonin receptor ligands and 2560 drug-like decoys. To evaluate the effect of including a priori information in receptor models, 12 representative melatonin receptor ligands were placed into the MT2 receptor models in poses consistent with known mutagenesis data and with assessed pharmacophore models. The receptor structures were then adapted to the ligands by induced-fit docking. Most of the 144 ligand-adapted MT2 receptor models showed significant improvements in screening enrichments compared to the unrefined homology models, with some template/refinement combinations giving excellent enrichment factors. The discriminating ability of the models was further tested on the 29 active ligands plus a set of 21 inactive or low-affinity compounds from the same chemical classes. Rotameric states of side chains for some residues, presumed to be involved in the binding process, were correlated with screening effectiveness, suggesting the existence of specific receptor conformations able to recognize active compounds. The top MT2 receptor model was able to identify 24 of 29 active ligands among the first 2% of the screened database. This work provides insights into the use of refined GPCR homology models for virtual screening.
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Affiliation(s)
- Daniele Pala
- Dipartimento di Farmacia, Università degli Studi di Parma, Parco Area delle Scienze 27/A, I-43124 Parma, Italy
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15
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Rivara S, Pala D, Lodola A, Mor M, Lucini V, Dugnani S, Scaglione F, Bedini A, Lucarini S, Tarzia G, Spadoni G. MT1-Selective Melatonin Receptor Ligands: Synthesis, Pharmacological Evaluation, and Molecular Dynamics Investigation ofN-{[(3-O-Substituted)anilino]alkyl}amides. ChemMedChem 2012; 7:1954-64. [DOI: 10.1002/cmdc.201200303] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2012] [Revised: 07/27/2012] [Indexed: 11/06/2022]
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16
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Zefirova ON, Baranova TY, Ivanova AA, Ivanov AA, Zefirov NS. Application of the bridgehead fragments for the design of conformationally restricted melatonin analogues. Bioorg Chem 2011; 39:67-72. [PMID: 21419469 DOI: 10.1016/j.bioorg.2011.02.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2011] [Accepted: 02/21/2011] [Indexed: 10/18/2022]
Abstract
Conformationally constrained analogues of the hormone melatonin with a side chain incorporated into the bicyclic bridgehead core were synthesized based on the homology modeling and molecular docking studies performed for the MT(2) melatonin receptor. The methoxy-indole derivative fused with exo-N-acetamino-substituted bicyclo[2.2.2]octane was found to possess nanomolar MT(2) receptor affinity.
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Affiliation(s)
- Olga N Zefirova
- Department of Chemistry, M.V. Lomonosov Moscow State University, Russian Federation.
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17
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Girardo M, Bettini N, Dema E, Cervellati S. The role of melatonin in the pathogenesis of adolescent idiopathic scoliosis (AIS). EUROPEAN SPINE JOURNAL : OFFICIAL PUBLICATION OF THE EUROPEAN SPINE SOCIETY, THE EUROPEAN SPINAL DEFORMITY SOCIETY, AND THE EUROPEAN SECTION OF THE CERVICAL SPINE RESEARCH SOCIETY 2011; 20 Suppl 1:S68-74. [PMID: 21416282 PMCID: PMC3087042 DOI: 10.1007/s00586-011-1750-5] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 03/02/2011] [Indexed: 12/15/2022]
Abstract
The cause of adolescent idiopathic scoliosis (AIS) in humans remains obscure and probably multifactorial. At present, there is no proven method or test available to identify children or adolescent at risk of developing AIS or identify which of the affected individuals are at risk of progression. Reported associations are linked in pathogenesis rather than etiologic factors. Melatonin may play a role in the pathogenesis of scoliosis (neuroendocrine hypothesis), but at present, the data available cannot clearly show the role of melatonin in producing scoliosis in humans. The data regarding human melatonin levels are mixed at best, and the melatonin deficiency as a causative factor in the etiology of scoliosis cannot be supported. It will be an important issue of future research to investigate the role of melatonin in human biology, the clinical efficacy, and safety of melatonin under different pathological situations. Research is needed to better define the role of all factors in AIS development.
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Affiliation(s)
- M Girardo
- Department of Spine Surgery, CTO/CRF/Maria Adelaide, Turin, Italy.
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Genetic variants in melatonin synthesis and signaling pathway are not associated with adolescent idiopathic scoliosis. Spine (Phila Pa 1976) 2011; 36:37-40. [PMID: 21192222 DOI: 10.1097/brs.0b013e3181e8755b] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN Genetic association study investigating the association of genetic markers of melatonin signaling and biosynthesis with adolescent idiopathic scoliosis (AIS). OBJECTIVE To determine whether gene polymorphisms related to the melatonin signaling or biosynthesis pathways are associated with AIS. SUMMARY OF BACKGROUND DATA Data have been published on the potential role of gene polymorphisms for melatonin receptor (MTNR) 1B in predicting AIS. Other genes in the melatonin pathways have been tested for association with AIS. METHODS The following genes involved in melatonin synthesis were evaluated herein: tryptophan 5-hyroxylase 1 (TPH1), serotonin N-acetyltransferase (SNAT), and hydroxyindoleo-methyltransferase (HIOMT). In addition, proteins involved in melatonin signaling were also included in this study: MTNR1A, MTNR1B, and protein kinase C delta (PKCd). High throughput microarray-based single nucleotide polymorphism (SNP) genotyping was performed for these seven genes using DNA samples from 589 AIS subjects and 1533 ethnically matched controls. Chi-square analyses of allele frequency between AIS cases and controls were performed and odds ratios were calculated for all SNP markers. RESULTS Three SNPs were tested for both MTNR1A and HIOMT, 4 for TPH1 and SNAT, 12 for PKCd, and 7 for MTNR1B. The minor allele frequencies were not significantly different between AIS cases and controls. No association was thus found between AIS and the investigated SNPs. CONCLUSIONS Genetic polymorphisms associated with either melatonin synthesis or its signaling pathway are unlikely to be commonly associated with AIS.
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Physiology and pharmacology of melatonin in relation to biological rhythms. Pharmacol Rep 2009; 61:383-410. [PMID: 19605939 DOI: 10.1016/s1734-1140(09)70081-7] [Citation(s) in RCA: 201] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2008] [Revised: 05/01/2009] [Indexed: 01/01/2023]
Abstract
Melatonin is an evolutionarily conserved molecule that serves a time-keeping function in various species. In vertebrates, melatonin is produced predominantly by the pineal gland with a marked circadian rhythm that is governed by the central circadian pacemaker (biological clock) in the suprachiasmatic nuclei of the hypothalamus. High levels of melatonin are normally found at night, and low levels are seen during daylight hours. As a consequence, melatonin has been called the "darkness hormone". This review surveys the current state of knowledge regarding the regulation of melatonin synthesis, receptor expression, and function. In particular, it addresses the physiological, pathological, and therapeutic aspects of melatonin in humans, with an emphasis on biological rhythms.
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20
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Cogé F, Guenin SP, Fery I, Migaud M, Devavry S, Slugocki C, Legros C, Ouvry C, Cohen W, Renault N, Nosjean O, Malpaux B, Delagrange P, Boutin JA. The end of a myth: cloning and characterization of the ovine melatonin MT(2) receptor. Br J Pharmacol 2009; 158:1248-62. [PMID: 19814723 DOI: 10.1111/j.1476-5381.2009.00453.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND AND PURPOSE For many years, it was suspected that sheep expressed only one melatonin receptor (closely resembling MT(1) from other mammal species). Here we report the cloning of another melatonin receptor, MT(2), from sheep. EXPERIMENTAL APPROACH Using a thermo-resistant reverse transcriptase and polymerase chain reaction primer set homologous to the bovine MT(2) mRNA sequence, we have cloned and characterized MT(2) receptors from sheep retina. KEY RESULTS The ovine MT(2) receptor presents 96%, 72% and 67% identity with cattle, human and rat respectively. This MT(2) receptor stably expressed in CHO-K1 cells showed high-affinity 2[(125)I]-iodomelatonin binding (K(D)= 0.04 nM). The rank order of inhibition of 2[(125)I]-iodomelatonin binding by melatonin, 4-phenyl-2-propionamidotetralin and luzindole was similar to that exhibited by MT(2) receptors of other species (melatonin > 4-phenyl-2-propionamidotetralin > luzindole). However, its pharmacological profile was closer to that of rat, rather than human MT(2) receptors. Functionally, the ovine MT(2) receptors were coupled to G(i) proteins leading to inhibition of adenylyl cyclase, as the other melatonin receptors. In sheep brain, MT(2) mRNA was expressed in pars tuberalis, choroid plexus and retina, and moderately in mammillary bodies. Real-time polymerase chain reaction showed that in sheep pars tuberalis, premammillary hypothalamus and mammillary bodies, the temporal pattern of expression of MT(1) and MT(2) mRNA was not parallel in the three tissues. CONCLUSION AND IMPLICATIONS Co-expression of MT(1) and MT(2) receptors in all analysed sheep brain tissues suggests that MT(2) receptors may participate in melatonin regulation of seasonal anovulatory activity in ewes by modulating MT(1) receptor action.
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Affiliation(s)
- F Cogé
- Pharmacologie Moléculaire et Cellulaire, Institut de Recherches SERVIER, Suresnes, France
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21
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Mazna P, Grycova L, Balik A, Zemkova H, Friedlova E, Obsilova V, Obsil T, Teisinger J. The role of proline residues in the structure and function of human MT2 melatonin receptor. J Pineal Res 2008; 45:361-72. [PMID: 18544139 DOI: 10.1111/j.1600-079x.2008.00598.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Melatonin functions as an essential regulator of various physiological processes in all vertebrate species. In mammals, two G protein-coupled melatonin receptors (GPCR) mediate some melatonin's actions: MT1 and MT2. Transmembrane domains (TM) of most GPCRs contain a set of highly conserved proline residues that presumably play important structural and functional roles. As TM segments of MT2 receptor display several interesting differences in expression of specific proline residues compared to other rhodopsin-like receptors (rGPCRs), we investigated the role of proline residues in the structure and function of this receptor. All prolines in TM segments of MT2 receptor were individually replaced with alanine and/or glycine. In addition, the unusual NAxxY motif located in TM7 was mutated to generate highly conserved NPxxY motif found in the majority of rGPCR proteins. Following transient expression in CHO-K1 cells, binding properties of the mutant receptors and their ability to transduce signals were analyzed using (125)I-mel- and [(35)S]GTPgammaS-binding assays, respectively. The impact of the performed mutations on the receptor structure was assessed by molecular dynamic simulations of MT2 receptors embedded in the fully hydrated phospholipid bilayer. Our results indicate that residues P174, P212 and P266 are important for the ligand binding and/or signaling of the human MT2 receptor. We also show that changes within the unusual NAxxY sequence in the TM7 (mutations A305P and A305V) produce defective MT2 receptors indicating an important role of this motif in the function of melatonin receptors.
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MESH Headings
- Amino Acid Motifs
- Amino Acid Substitution
- Animals
- CHO Cells
- Cloning, Molecular
- Computer Simulation
- Cricetinae
- Cricetulus
- Humans
- Immunohistochemistry
- Iodine Radioisotopes
- Melatonin/metabolism
- Membrane Proteins
- Microscopy, Confocal
- Models, Molecular
- Mutation
- Proline/physiology
- Protein Structure, Tertiary
- Receptor, Melatonin, MT2/chemistry
- Receptor, Melatonin, MT2/genetics
- Receptor, Melatonin, MT2/metabolism
- Sulfur Radioisotopes
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Affiliation(s)
- Petr Mazna
- Institute of Physiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic
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Sethi S, Adams W, Pollock J, Witt-Enderby PA. C-terminal domains within human MT1 and MT2 melatonin receptors are involved in internalization processes. J Pineal Res 2008; 45:212-8. [PMID: 18341518 DOI: 10.1111/j.1600-079x.2008.00579.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Melatonin, a molecule implicated in a variety of diseases, including cancer, often exerts its effects through G-protein-coupled melatonin receptors, MT(1) and MT(2). In this study, we sought to understand further the domains involved in the function and desensitization patterns of these receptors through site-directed mutagenesis. Two mutations were constructed in the cytoplasmic C-terminal tail of each receptor subtype: (i) a cysteine residue in the C-terminal tail was mutated to alanine, thus removing a putative palmitoylation site, and a site possibly required for normal receptor function (MT(1)C7.72A and MT(2)C7.77A) and (ii) the C-terminal tail in the MT(1) and MT(2) receptors was truncated, removing the putative phosphorylation and beta-arrestin binding sites (MT(1)Y7.64 and MT(2)Y7.64). These mutations did not alter the affinity of 2-[(125)I]-iodomelatonin binding to the MT(1) or MT(2) receptors. Using confocal microscopy, it was determined that the putative palmitoylation site (cysteine residue) did not play a role in receptor internalization; however, this residue was essential for receptor function, as determined by 3',5'-cyclic adenosine monophosphate (cAMP) accumulation assays. Truncation of the C-terminal tail of both receptors (MT(1)Y7.64 and MT(2)Y7.64) inhibited internalization as well as the cAMP response, suggesting the importance of the C-terminal tail in these receptor functions.
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MESH Headings
- Animals
- Arrestins/metabolism
- Binding Sites/genetics
- COS Cells
- Chlorocebus aethiops
- Cyclic AMP/metabolism
- Endocytosis/physiology
- Humans
- Melatonin/metabolism
- Microscopy, Confocal
- Models, Biological
- Mutation
- Receptor, Melatonin, MT1/genetics
- Receptor, Melatonin, MT1/physiology
- Receptor, Melatonin, MT2/genetics
- Receptor, Melatonin, MT2/physiology
- beta-Arrestins
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Affiliation(s)
- Shalini Sethi
- Division of Pharmaceutical Sciences, School of Pharmacy, Bayer School of Natural and Environmental Sciences, Duquesne University, Pittsburgh, PA 15282, USA
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Dufourny L, Levasseur A, Migaud M, Callebaut I, Pontarotti P, Malpaux B, Monget P. GPR50 is the mammalian ortholog of Mel1c: evidence of rapid evolution in mammals. BMC Evol Biol 2008; 8:105. [PMID: 18400093 PMCID: PMC2323367 DOI: 10.1186/1471-2148-8-105] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2007] [Accepted: 04/09/2008] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND The melatonin receptor subfamily contains three members Mel1a, Mel1b and Mel1c, found in all vertebrates except for Mel1c which is found only in fish, Xenopus species and the chicken. Another receptor, the melatonin related receptor known as GPR50, found exclusively in mammals and later identified as a member of the melatonin receptor subfamily because of its identity to the three melatonin receptors despite its absence of affinity for melatonin. The aim of this study was to describe the evolutionary relationships between GPR50 and the three other members of the melatonin receptor subfamily. RESULTS Using an in silico approach, we demonstrated that GPR50 is the ortholog of the high affinity Mel1c receptor. It was necessary to also study the synteny of this gene to reach this conclusion because classical mathematical models that estimate orthology and build phylogenetic trees were not sufficient. The receptor has been deeply remodelled through evolution by the mutation of numerous amino acids and by the addition of a long C-terminal tail. These alterations have modified its affinity for melatonin and probably affected its interactions with the other two known melatonin receptors MT1 and MT2 that are encoded by Mel1a and Mel1b genes respectively. Evolutionary studies provided evidence that the GPR50 group evolved under different selective pressure as compared to the orthologous groups Me11 a, b, and c. CONCLUSION This study demonstrated that there are only three members in the melatonin receptor subfamily with one of them (Me11c) undergoing rapid evolution from fishes and birds to mammals. Further studies are necessary to investigate the physiological roles of this receptor.
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Affiliation(s)
- Laurence Dufourny
- Physiologie de la Reproduction et des Comportements, UMR 6175 INRA-CNRS-Université François Rabelais de Tours-Haras Nationaux, 37380 Nouzilly, France.
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24
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Azeddine B, Letellier K, Wang DS, Moldovan F, Moreau A. Molecular determinants of melatonin signaling dysfunction in adolescent idiopathic scoliosis. Clin Orthop Relat Res 2007; 462:45-52. [PMID: 17563702 DOI: 10.1097/blo.0b013e31811f39fa] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Presently, the genetic cause of adolescent idiopathic scoliosis (AIS), the most common form of scoliosis, remains unclear. Among many hypotheses, the neuroendocrine hypothesis involving a melatonin deficiency as the source for AIS generated the greatest interest and controversy since no decrease in circulating melatonin level has been observed in a majority of studies. Previously, we have reconciled the role of melatonin in AIS by demonstrating a melatonin signaling dysfunction occurring in osteoblasts derived from AIS patients, which contrasted with similar cells isolated from healthy subjects. We found that this difference is caused in AIS cells by increased phosphorylation of serine residues affecting the activity of G inhibitory proteins normally associated with melatonin cell surface receptors. Here we propose a preliminary molecular classification of patients with AIS based on the cellular response to the melatonin (cAMP) and distinct protein-protein interactions. These interactions include those between protein kinase C delta (PKCdelta) and MT2 melatonin receptors or PKCdelta and the receptor for activated protein C kinase 1. This finding could help in future molecular classification of patients with AIS.
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Affiliation(s)
- Bouziane Azeddine
- Research Centre, Sainte-Justine University Hospital, Montreal, Canada
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25
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Spadoni G, Bedini A, Guidi T, Tarzia G, Lucini V, Pannacci M, Fraschini F. Towards the Development of Mixed MT1-Agonist/MT2-Antagonist Melatonin Receptor Ligands. ChemMedChem 2006; 1:1099-105. [PMID: 16955531 DOI: 10.1002/cmdc.200600133] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Herein we report attempts to optimize the pharmacological properties of 5-(2-hydroxyethoxy)-N-acetyltryptamine (5-HEAT), a melatonin receptor ligand previously described by us. Several 5-substituted and 2,5-disubstituted N-acyltryptamines were synthesized and evaluated in vitro for the human cloned MT(1) and MT(2) receptors. From this series of N-acyltryptamines the 2-bromo derivative (5 c) retains the interesting efficacy profile of 5-HEAT and shows increased melatonin receptor affinities; it represents one of the first examples of a high-affinity MT(1) agonist/MT(2) antagonist. Some other full agonists for both melatonin receptors which exhibit similar or increased affinity relative to that of melatonin were obtained.
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Affiliation(s)
- Gilberto Spadoni
- Istituto di Chimica Farmaceutica e Tossicologica, Università degli Studi di Urbino Carlo Bo, Piazza Rinascimento 6, Urbino, Italy
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26
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Chugunov AO, Farce A, Chavatte P, Efremov RG. Differences in Binding Sites of Two Melatonin Receptors Help to Explain Their Selectivity to Some Melatonin Analogs: A Molecular Modeling Study. J Biomol Struct Dyn 2006; 24:91-107. [PMID: 16928133 DOI: 10.1080/07391102.2006.10507103] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Numerous diseases have been linked to the malfunction of G-protein coupled receptors (GPCRs). Their adequate treatment requires rational design of new high-affinity and high-selectivity drugs targeting these receptors. In this work, we report three-dimensional models of the human MT(1) and MT(2) melatonin receptors, members of the GPCR family. The models are based on the X-ray structure of bovine rhodopsin. The computational approach employs an original procedure for optimization of receptor-ligand structures. It includes rotation of one of the transmembrane alpha-helices around its axis with simultaneous assessment of quality of the resulting complexes according to a number of criteria we have developed for this purpose. The optimal geometry of the receptor-ligand binding is selected based on the analysis of complementarity of hydrophobic/hydrophilic properties between the ligand and its protein environment in the binding site. The elaborated "optimized" models are employed to explore the details of protein-ligand interactions for melatonin and a number of its analogs with known affinity to MT(1) and MT(2) receptors. The models permit rationalization of experimental data, including those that were not used in model building. The perspectives opened by the constructed models and by the optimization procedure in the design of new drugs are discussed.
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Affiliation(s)
- Anton O Chugunov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Ul. Miklukho-Maklaya 16/10, GSP Moscow, 117997, Russia.
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27
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Surgand JS, Rodrigo J, Kellenberger E, Rognan D. A chemogenomic analysis of the transmembrane binding cavity of human G-protein-coupled receptors. Proteins 2006; 62:509-38. [PMID: 16294340 DOI: 10.1002/prot.20768] [Citation(s) in RCA: 189] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The amino acid sequences of 369 human nonolfactory G-protein-coupled receptors (GPCRs) have been aligned at the seven transmembrane domain (TM) and used to extract the nature of 30 critical residues supposed--from the X-ray structure of bovine rhodopsin bound to retinal--to line the TM binding cavity of ground-state receptors. Interestingly, the clustering of human GPCRs from these 30 residues mirrors the recently described phylogenetic tree of full-sequence human GPCRs (Fredriksson et al., Mol Pharmacol 2003;63:1256-1272) with few exceptions. A TM cavity could be found for all investigated GPCRs with physicochemical properties matching that of their cognate ligands. The current approach allows a very fast comparison of most human GPCRs from the focused perspective of the predicted TM cavity and permits to easily detect key residues that drive ligand selectivity or promiscuity.
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28
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Zhang Y, DeVries ME, Skolnick J. Structure modeling of all identified G protein-coupled receptors in the human genome. PLoS Comput Biol 2006; 2:e13. [PMID: 16485037 PMCID: PMC1364505 DOI: 10.1371/journal.pcbi.0020013] [Citation(s) in RCA: 151] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2005] [Accepted: 01/11/2005] [Indexed: 12/22/2022] Open
Abstract
G protein–coupled receptors (GPCRs), encoded by about 5% of human genes, comprise the largest family of integral membrane proteins and act as cell surface receptors responsible for the transduction of endogenous signal into a cellular response. Although tertiary structural information is crucial for function annotation and drug design, there are few experimentally determined GPCR structures. To address this issue, we employ the recently developed threading assembly refinement (TASSER) method to generate structure predictions for all 907 putative GPCRs in the human genome. Unlike traditional homology modeling approaches, TASSER modeling does not require solved homologous template structures; moreover, it often refines the structures closer to native. These features are essential for the comprehensive modeling of all human GPCRs when close homologous templates are absent. Based on a benchmarked confidence score, approximately 820 predicted models should have the correct folds. The majority of GPCR models share the characteristic seven-transmembrane helix topology, but 45 ORFs are predicted to have different structures. This is due to GPCR fragments that are predominantly from extracellular or intracellular domains as well as database annotation errors. Our preliminary validation includes the automated modeling of bovine rhodopsin, the only solved GPCR in the Protein Data Bank. With homologous templates excluded, the final model built by TASSER has a global Cα root-mean-squared deviation from native of 4.6 Å, with a root-mean-squared deviation in the transmembrane helix region of 2.1 Å. Models of several representative GPCRs are compared with mutagenesis and affinity labeling data, and consistent agreement is demonstrated. Structure clustering of the predicted models shows that GPCRs with similar structures tend to belong to a similar functional class even when their sequences are diverse. These results demonstrate the usefulness and robustness of the in silico models for GPCR functional analysis. All predicted GPCR models are freely available for noncommercial users on our Web site (http://www.bioinformatics.buffalo.edu/GPCR). G protein–coupled receptors (GPCRs) are a large superfamily of integral membrane proteins that transduce signals across the cell membrane. Because of the breadth and importance of the physiological roles undertaken by the GPCR family, many of its members are important pharmacological targets. Although the knowledge of a protein's native structure can provide important insight into understanding its function and for the design of new drugs, the experimental determination of the three-dimensional structure of GPCR membrane proteins has proved to be very difficult. This is demonstrated by the fact that there is only one solved GPCR structure (from bovine rhodopsin) deposited in the Protein Data Bank library. In contrast, there are no human GPCR structures in the Protein Data Bank. To address the need for the tertiary structures of human GPCRs, using just sequence information, the authors use a newly developed threading-assembly-refinement method to generate models for all 907 registered GPCRs in the human genome. About 820 GPCRs are anticipated to have correct topology and transmembrane helix arrangement. A subset of the resulting models is validated by comparison with mutagenesis experimental data, and consistent agreement is demonstrated.
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Affiliation(s)
- Yang Zhang
- Center of Excellence in Bioinformatics, University at Buffalo, Buffalo, New York, United States of America
| | - Mark E DeVries
- Center of Excellence in Bioinformatics, University at Buffalo, Buffalo, New York, United States of America
| | - Jeffrey Skolnick
- Center of Excellence in Bioinformatics, University at Buffalo, Buffalo, New York, United States of America
- * To whom correspondence should be addressed. E-mail:
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Abstract
Melatonin, dubbed the hormone of darkness, is known to regulate a wide variety of physiological processes in mammals. This review describes well-defined functional responses mediated through activation of high-affinity MT1 and MT2 G protein-coupled receptors viewed as potential targets for drug discovery. MT1 melatonin receptors modulate neuronal firing, arterial vasocon-striction, cell proliferation in cancer cells, and reproductive and metabolic functions. Activation of MT2 melatonin receptors phase shift circadian rhythms of neuronal firing in the suprachiasmatic nucleus, inhibit dopamine release in retina, induce vasodilation and inhibition of leukocyte rolling in arterial beds, and enhance immune responses. The melatonin-mediated responses elicited by activation of MT1 and MT2 native melatonin receptors are dependent on circadian time, duration and mode of exposure to endogenous or exogenous melatonin, and functional receptor sensitivity. Together, these studies underscore the importance of carefully linking each melatonin receptor type to specific functional responses in target tissues to facilitate the design and development of novel therapeutic agent.
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Affiliation(s)
- Margarita L Dubocovich
- Department of Molecular Pharmacology & Biological Chemistry, Northwestern University Feinberg School of Medicine Center for Drug Discovery and Chemical Biology, Chicago, IL 60611, USA.
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Mazna P, Berka K, Jelinkova I, Balik A, Svoboda P, Obsilova V, Obsil T, Teisinger J. Ligand binding to the human MT2 melatonin receptor: the role of residues in transmembrane domains 3, 6, and 7. Biochem Biophys Res Commun 2005; 332:726-34. [PMID: 15913560 DOI: 10.1016/j.bbrc.2005.05.017] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2005] [Accepted: 05/03/2005] [Indexed: 12/15/2022]
Abstract
To better understand the mechanism of interactions between G-protein-coupled melatonin receptors and their ligands, our previously reported homology model of human MT2 receptor with docked 2-iodomelatonin was further refined and used to select residues within TM3, TM6, and TM7 potentially important for receptor-ligand interactions. Selected residues were mutated and radioligand-binding assay was used to test the binding affinities of hMT2 receptors transiently expressed in HEK293 cells. Our data demonstrate that residues N268 and A275 in TM6 as well as residues V291 and L295 in TM7 are essential for 2-iodomelatonin binding to the hMT2 receptor, while TM3 residues M120, G121, V124, and I125 may participate in binding of other receptor agonists and/or antagonists. Presented data also hint at possible specific interaction between the side-chain of Y188 in second extracellular loop and N-acetyl group of 2-iodomelatonin.
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Affiliation(s)
- Petr Mazna
- Institute of Physiology, Academy of Sciences of the Czech Republic, Videnska 1083, 142 20 Prague, Czech Republic
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Voronkov AE, Ivanov AA, Baskin II, Palyulin VA, Zefirov NS. Molecular Modeling Study of the Mechanism of Ligand Binding to Human Melatonin Receptors. DOKL BIOCHEM BIOPHYS 2005; 403:284-8. [PMID: 16229143 DOI: 10.1007/s10628-005-0093-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Affiliation(s)
- A E Voronkov
- Department of Chemistry, Moscow State University, Vorob'evy gory, Moscow, 119992 Russia
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Sugden D, Davidson K, Hough KA, Teh MT. Melatonin, melatonin receptors and melanophores: a moving story. ACTA ACUST UNITED AC 2005; 17:454-60. [PMID: 15357831 DOI: 10.1111/j.1600-0749.2004.00185.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Melatonin (5-methoxy N-acetyltryptamine) is a hormone synthesized and released from the pineal gland at night, which acts on specific high affinity G-protein coupled receptors to regulate various aspects of physiology and behaviour, including circadian and seasonal responses, and some retinal, cardiovascular and immunological functions. In amphibians, such as Xenopus laevis, another role of melatonin is in the control of skin coloration through an action on melanin-containing pigment granules (melanosomes) in melanophores. In these cells, very low concentrations of melatonin activate the Mel(1c) receptor subtype triggering movement of granules toward the cell centre thus lightening skin colour. Mel(1c) receptor activation reduces intracellular cAMP via a pertussis toxin-sensitive inhibitory G-protein (Gi), but how this and other intracellular signals regulate pigment movement is not yet fully understood. However, melanophores have proven an excellent model for the study of the molecular mechanisms which coordinate intracellular transport. Melanosome transport is reversible and involves both actin- (myosin V) and microtubule-dependent (kinesin II and dynein) motors. Melanosomes retain both kinesin and dynein during anterograde and retrograde transport, but the myosin V motor seems to be recruited to melanosomes during dispersion, where it assists kinesin II in dominating dynein thus driving net dispersion. Recent work suggests an important role for dynactin in coordinating the activity of the opposing microtubule motors. The melanophore pigment aggregation response has also played a vital role in the ongoing effort to devise specific melatonin receptor antagonists. Much of what has been learnt about the parts of the melatonin molecule required for receptor binding and activation has come from detailed structure-activity data using novel melatonin ligands. Work aiming to devise ligands specific for the distinct melatonin receptor subtypes stands poised to deliver selective agonists and antagonists which will be valuable tools in understanding the role of this enigmatic hormone in health and disease.
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Affiliation(s)
- David Sugden
- Division of Reproductive Health, Endocrinology and Development, School of Biomedical Sciences, New Hunts House, Kings College London, London Bridge, London SE1 1UL, UK.
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