1
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Zhang X, Guseinov AA, Jenkins L, Li K, Tikhonova IG, Milligan G, Zhang C. Structural basis for the ligand recognition and signaling of free fatty acid receptors. Sci Adv 2024; 10:eadj2384. [PMID: 38198545 PMCID: PMC10780892 DOI: 10.1126/sciadv.adj2384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Accepted: 12/05/2023] [Indexed: 01/12/2024]
Abstract
Free fatty acid receptors 1 to 4 (FFA1 to FFA4) are class A G protein-coupled receptors (GPCRs). FFA1 to FFA3 share substantial sequence similarity, whereas FFA4 is unrelated. However, FFA1 and FFA4 are activated by long-chain fatty acids, while FFA2 and FFA3 respond to short-chain fatty acids generated by intestinal microbiota. FFA1, FFA2, and FFA4 are potential drug targets for metabolic and inflammatory conditions. Here, we determined the active structures of FFA1 and FFA4 bound to docosahexaenoic acid, FFA4 bound to the synthetic agonist TUG-891, and butyrate-bound FFA2, each complexed with an engineered heterotrimeric Gq protein (miniGq), by cryo-electron microscopy. Together with computational simulations and mutagenesis studies, we elucidated the similarities and differences in the binding modes of fatty acid ligands to their respective GPCRs. Our findings unveiled distinct mechanisms of receptor activation and G protein coupling. We anticipate that these outcomes will facilitate structure-based drug development and underpin future research on this group of GPCRs.
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Affiliation(s)
- Xuan Zhang
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Abdul-Akim Guseinov
- School of Pharmacy, Medical Biology Centre, Queen’s University Belfast, Belfast BT9 7BL, Northern Ireland, UK
| | - Laura Jenkins
- Centre for Translational Pharmacology, School of Molecular Biosciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, UK
| | - Kunpeng Li
- Cryo-EM Core Facility, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Irina G. Tikhonova
- School of Pharmacy, Medical Biology Centre, Queen’s University Belfast, Belfast BT9 7BL, Northern Ireland, UK
| | - Graeme Milligan
- Centre for Translational Pharmacology, School of Molecular Biosciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, UK
| | - Cheng Zhang
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA
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2
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Daly C, Guseinov AA, Hahn H, Wright A, Tikhonova IG, Thomsen ARB, Plouffe B. β-Arrestin-dependent and -independent endosomal G protein activation by the vasopressin type 2 receptor. eLife 2023; 12:RP87754. [PMID: 37855711 PMCID: PMC10586804 DOI: 10.7554/elife.87754] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2023] Open
Abstract
The vasopressin type 2 receptor (V2R) is an essential G protein-coupled receptor (GPCR) in renal regulation of water homeostasis. Upon stimulation, the V2R activates Gαs and Gαq/11, which is followed by robust recruitment of β-arrestins and receptor internalization into endosomes. Unlike canonical GPCR signaling, the β-arrestin association with the V2R does not terminate Gαs activation, and thus, Gαs-mediated signaling is sustained while the receptor is internalized. Here, we demonstrate that this V2R ability to co-interact with G protein/β-arrestin and promote endosomal G protein signaling is not restricted to Gαs, but also involves Gαq/11. Furthermore, our data imply that β-arrestins potentiate Gαs/Gαq/11 activation at endosomes rather than terminating their signaling. Surprisingly, we found that the V2R internalizes and promote endosomal G protein activation independent of β-arrestins to a minor degree. These new observations challenge the current model of endosomal GPCR signaling and suggest that this event can occur in both β-arrestin-dependent and -independent manners.
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Affiliation(s)
- Carole Daly
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen’s University BelfastBelfastUnited Kingdom
| | | | - Hyunggu Hahn
- Department of Molecular Pathobiology, New York University College of DentistryNew YorkUnited States
- NYU Pain Research Center, New York University College of DentistryNew YorkUnited States
| | - Adam Wright
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen’s University BelfastBelfastUnited Kingdom
| | | | - Alex Rojas Bie Thomsen
- Department of Molecular Pathobiology, New York University College of DentistryNew YorkUnited States
- NYU Pain Research Center, New York University College of DentistryNew YorkUnited States
| | - Bianca Plouffe
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen’s University BelfastBelfastUnited Kingdom
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3
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Zhang X, Guseinov AA, Jenkins L, Li K, Tikhonova IG, Milligan G, Zhang C. Structural basis for the ligand recognition and signaling of free fatty acid receptors. bioRxiv 2023:2023.08.20.553924. [PMID: 37662198 PMCID: PMC10473637 DOI: 10.1101/2023.08.20.553924] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/05/2023]
Abstract
Free fatty acid receptors 1-4 (FFA1-4) are class A G protein-coupled receptors (GPCRs). FFA1-3 share substantial sequence similarity whereas FFA4 is unrelated. Despite this FFA1 and FFA4 are activated by the same range of long chain fatty acids (LCFAs) whilst FFA2 and FFA3 are instead activated by short chain fatty acids (SCFAs) generated by the intestinal microbiota. Each of FFA1, 2 and 4 are promising targets for novel drug development in metabolic and inflammatory conditions. To gain insights into the basis of ligand interactions with, and molecular mechanisms underlying activation of, FFAs by LCFAs and SCFAs, we determined the active structures of FFA1 and FFA4 bound to the polyunsaturated LCFA docosahexaenoic acid (DHA), FFA4 bound to the synthetic agonist TUG-891, as well as SCFA butyrate-bound FFA2, each complexed with an engineered heterotrimeric Gq protein (miniGq), by cryo-electron microscopy. Together with computational simulations and mutagenesis studies, we elucidated the similarities and differences in the binding modes of fatty acid ligands with varying chain lengths to their respective GPCRs. Our findings unveil distinct mechanisms of receptor activation and G protein coupling. We anticipate that these outcomes will facilitate structure-based drug development and underpin future research to understand allosteric modulation and biased signaling of this group of GPCRs.
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Affiliation(s)
- Xuan Zhang
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA15261, USA
| | - Abdul-Akim Guseinov
- School of Pharmacy, Medical Biology Centre, Queen’s University Belfast, Belfast BT9 7BL, Northern Ireland, United Kingdom
| | - Laura Jenkins
- Centre for Translational Pharmacology, School of Molecular Biosciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom
| | - Kunpeng Li
- Cryo-EM core facility, Case Western Reserve University, OH44106, USA
| | - Irina G. Tikhonova
- School of Pharmacy, Medical Biology Centre, Queen’s University Belfast, Belfast BT9 7BL, Northern Ireland, United Kingdom
| | - Graeme Milligan
- Centre for Translational Pharmacology, School of Molecular Biosciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom
| | - Cheng Zhang
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA15261, USA
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4
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Daly C, Guseinov AA, Hahn H, Wright A, Tikhonova IG, Thomsen ARB, Plouffe B. β-arrestin-dependent and -independent endosomal G protein activation by the vasopressin type 2 receptor. bioRxiv 2023:2023.04.01.535208. [PMID: 37034816 PMCID: PMC10081317 DOI: 10.1101/2023.04.01.535208] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
The vasopressin type 2 receptor (V2R) is an essential GPCR in renal regulation of water homeostasis. Upon stimulation, the V2R activates Gαs and Gαq/11, which is followed by robust recruitment of β-arrestins and receptor internalization into endosomes. Unlike canonical GPCR signaling, the β-arrestin association with the V2R does not terminate Gαs activation, and thus, Gαs-mediated signaling is sustained while the receptor is internalized. Here, we demonstrate that this V2R ability to co-interact with G protein/β-arrestin and promote endosomal G protein signaling is not restricted to Gαs, but also involves Gαq/11. Furthermore, our data implies that β-arrestins potentiate Gαs/Gαq/11 activation at endosomes rather than terminating their signaling. Surprisingly, we found that the V2R internalizes and promote endosomal G protein activation independent of β-arrestins to a minor degree. These new observations challenge the current model of endosomal GPCR signaling and suggest that this event can occur in both β-arrestin-dependent and -independent manners.
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Affiliation(s)
- Carole Daly
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, Belfast, UK
| | | | - Hyunggu Hahn
- Department of Molecular Pathobiology, New York University College of Dentistry, New York, USA
- NYU Pain Research Center, New York University College of Dentistry, New York, USA
| | - Adam Wright
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, Belfast, UK
| | | | - Alex Rojas Bie Thomsen
- Department of Molecular Pathobiology, New York University College of Dentistry, New York, USA
- NYU Pain Research Center, New York University College of Dentistry, New York, USA
| | - Bianca Plouffe
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, Belfast, UK
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5
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Karlov DS, Long SL, Zeng X, Xu F, Lal K, Cao L, Hayoun K, Lin J, Joyce SA, Tikhonova IG. Characterization of the mechanism of bile salt hydrolase substrate specificity by experimental and computational analyses. Structure 2023; 31:629-638.e5. [PMID: 36963397 DOI: 10.1016/j.str.2023.02.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 02/02/2023] [Accepted: 02/27/2023] [Indexed: 03/26/2023]
Abstract
Bile salt hydrolases (BSHs) are currently being investigated as target enzymes for metabolic regulators in humans and as growth promoters in farm animals. Understanding structural features underlying substrate specificity is necessary for inhibitor design. Here, we used a multidisciplinary workflow including mass spectrometry, mutagenesis, molecular dynamic simulations, machine learning, and crystallography to demonstrate substrate specificity in Lactobacillus salivarius BSH, the most abundant enzyme in human and farm animal intestines. We show the preference of substrates with a taurine head and a dehydroxylated sterol ring for hydrolysis. A regression model that correlates the relative rates of hydrolysis of various substrates in various enzyme mutants with the residue-substrate interaction energies guided the identification of structural determinants of substrate binding and specificity. In addition, we found T208 from another BSH protomer regulating the hydrolysis. The designed workflow can be used for fast and comprehensive characterization of enzymes with a broad range of substrates.
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Affiliation(s)
- Dmitry S Karlov
- School of Pharmacy, Medical Biology Centre, Queen's University Belfast, BT9 7BL Northern Ireland, UK
| | - Sarah L Long
- School of Biochemistry and Cell Biology, University College Cork, Cork T12 YT20, Ireland; APC Microbiome Ireland, University College Cork, Cork T12 YT20, Ireland
| | - Ximin Zeng
- Department of Animal Science, The University of Tennessee, Knoxville, TN 37996, USA
| | - Fuzhou Xu
- Department of Animal Science, The University of Tennessee, Knoxville, TN 37996, USA; Institute of Animal Husbandry and Veterinary Medicine, Beijing Academy of Agriculture and Forestry Sciences, Beijing 100097, China
| | - Kanhaya Lal
- School of Pharmacy, Medical Biology Centre, Queen's University Belfast, BT9 7BL Northern Ireland, UK
| | - Liu Cao
- Department of Animal Science, The University of Tennessee, Knoxville, TN 37996, USA
| | - Karim Hayoun
- School of Biochemistry and Cell Biology, University College Cork, Cork T12 YT20, Ireland; APC Microbiome Ireland, University College Cork, Cork T12 YT20, Ireland
| | - Jun Lin
- Department of Animal Science, The University of Tennessee, Knoxville, TN 37996, USA.
| | - Susan A Joyce
- School of Biochemistry and Cell Biology, University College Cork, Cork T12 YT20, Ireland; APC Microbiome Ireland, University College Cork, Cork T12 YT20, Ireland.
| | - Irina G Tikhonova
- School of Pharmacy, Medical Biology Centre, Queen's University Belfast, BT9 7BL Northern Ireland, UK.
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6
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Dudem S, Boon PX, Mullins N, McClafferty H, Shipston MJ, Wilkinson RDA, Lobb I, Sergeant GP, Thornbury KD, Tikhonova IG, Hollywood MA. Oxidation modulates LINGO2-induced inactivation of large conductance, Ca 2+-activated potassium channels. J Biol Chem 2023; 299:102975. [PMID: 36738787 PMCID: PMC10020666 DOI: 10.1016/j.jbc.2023.102975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Revised: 01/27/2023] [Accepted: 01/29/2023] [Indexed: 02/05/2023] Open
Abstract
Ca2+ and voltage-activated K+ (BK) channels are ubiquitous ion channels that can be modulated by accessory proteins, including β, γ, and LINGO1 BK subunits. In this study, we utilized a combination of site-directed mutagenesis, patch clamp electrophysiology, and molecular modeling to investigate if the biophysical properties of BK currents were affected by coexpression of LINGO2 and to examine how they are regulated by oxidation. We demonstrate that LINGO2 is a regulator of BK channels, since its coexpression with BK channels yields rapid inactivating currents, the activation of which is shifted ∼-30 mV compared to that of BKα currents. Furthermore, we show the oxidation of BK:LINGO2 currents (by exposure to epifluorescence illumination or chloramine-T) abolished inactivation. The effect of illumination depended on the presence of GFP, suggesting that it released free radicals which oxidized cysteine or methionine residues. In addition, the oxidation effects were resistant to treatment with the cysteine-specific reducing agent DTT, suggesting that methionine rather than cysteine residues may be involved. Our data with synthetic LINGO2 tail peptides further demonstrate that the rate of inactivation was slowed when residues M603 or M605 were oxidized, and practically abolished when both were oxidized. Taken together, these data demonstrate that both methionine residues in the LINGO2 tail mediate the effect of oxidation on BK:LINGO2 channels. Our molecular modeling suggests that methionine oxidation reduces the lipophilicity of the tail, thus preventing it from occluding the pore of the BK channel.
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Affiliation(s)
- Srikanth Dudem
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Louth, Ireland
| | - Pei Xin Boon
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Louth, Ireland
| | - Nicholas Mullins
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Louth, Ireland
| | - Heather McClafferty
- Centre for Discovery Brain Sciences, University of Edinburgh, Scotland, United Kingdom
| | - Michael J Shipston
- Centre for Discovery Brain Sciences, University of Edinburgh, Scotland, United Kingdom
| | | | - Ian Lobb
- Almac Discovery Ltd, Health Sciences Building, Belfast, NIR, United Kingdom
| | - Gerard P Sergeant
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Louth, Ireland
| | - Keith D Thornbury
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Louth, Ireland
| | - Irina G Tikhonova
- School of Pharmacy, Queen's University of Belfast, NIR, United Kingdom
| | - Mark A Hollywood
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Louth, Ireland.
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7
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Ding T, Karlov DS, Pino-Angeles A, Tikhonova IG. Intermolecular Interactions in G Protein-Coupled Receptor Allosteric Sites at the Membrane Interface from Molecular Dynamics Simulations and Quantum Chemical Calculations. J Chem Inf Model 2022; 62:4736-4747. [PMID: 36178787 PMCID: PMC9554917 DOI: 10.1021/acs.jcim.2c00788] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Allosteric modulators are called promising candidates in G protein-coupled receptor (GPCR) drug development by displaying subtype selectivity and more specific receptor modulation. Among the allosteric sites known to date, cavities at the receptor-lipid interface represent an uncharacteristic binding location that raises many questions about the ligand interactions and stability, the binding site structure, and how all of these are affected by lipid molecules. In this work, we analyze interactions in the allosteric sites of the PAR2, C5aR1, and GCGR receptors in three lipid compositions using molecular dynamics simulations. In addition, we performed quantum chemical calculations involving the symmetry-adapted perturbation theory (SAPT) and the natural population analysis to quantify the strength of intermolecular interactions. We show that besides classical hydrogen bonds, weak polar interactions such as O-HC, O-Br, and long-range electrostatics with the backbone amides contribute to the stability of allosteric modulators at the receptor-lipid interface. The allosteric cavities are detectable in various membrane compositions. The availability of polar atoms for interactions in such cavities can be assessed by water molecules from simulations. Although ligand-lipid interactions are weak, lipid tails play a role in ligand binding pose stability and the size of allosteric cavities. We discuss physicochemical aspects of ligand binding at the receptor-lipid interface and suggest a compound library enriched by weak donor groups for ligand search in such sites.
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Affiliation(s)
- Tianyi Ding
- School of Pharmacy, Medical Biology Centre, Queen's University Belfast, Belfast, Northern IrelandBT9 7BL, U.K
| | - Dmitry S Karlov
- School of Pharmacy, Medical Biology Centre, Queen's University Belfast, Belfast, Northern IrelandBT9 7BL, U.K
| | - Almudena Pino-Angeles
- School of Pharmacy, Medical Biology Centre, Queen's University Belfast, Belfast, Northern IrelandBT9 7BL, U.K
| | - Irina G Tikhonova
- School of Pharmacy, Medical Biology Centre, Queen's University Belfast, Belfast, Northern IrelandBT9 7BL, U.K
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8
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Mahindra A, Jenkins L, Marsango S, Huggett M, Huggett M, Robinson L, Gillespie J, Rajamanickam M, Morrison A, McElroy S, Tikhonova IG, Milligan G, Jamieson AG. Investigating the Structure-Activity Relationship of 1,2,4-Triazine G-Protein-Coupled Receptor 84 (GPR84) Antagonists. J Med Chem 2022; 65:11270-11290. [PMID: 35948061 PMCID: PMC9421653 DOI: 10.1021/acs.jmedchem.2c00804] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
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G-protein-coupled receptor 84 (GPR84) is a proinflammatory
orphan
G-protein-coupled receptor implicated in several inflammatory and
fibrotic diseases. Several agonist and antagonist ligands have been
developed that target GPR84; however, a noncompetitive receptor blocker
that was progressed to phase II clinical trials failed to demonstrate
efficacy. New high-quality antagonists are required to investigate
the pathophysiological role of GPR84 and to validate GPR84 as a therapeutic
target. We previously reported the discovery of a novel triazine GPR84
competitive antagonist 1. Here, we describe an extensive
structure–activity relationship (SAR) of antagonist 1 and also present in silico docking with supporting mutagenesis studies
that reveals a potential binding pose for this type of orthosteric
antagonist. Lead compound 42 is a potent GPR84 antagonist
with a favorable pharmacokinetic (PK) profile suitable for further
drug development.
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Affiliation(s)
- Amit Mahindra
- School of Chemistry, University of Glasgow, Joseph Black Building, University Avenue, Glasgow G12 8QQ, U.K
| | - Laura Jenkins
- Centre for Translational Pharmacology, Institute of Molecular, Cell and Systems Biology, University of Glasgow, Davidson Building, Glasgow G12 8QQ, U.K
| | - Sara Marsango
- Centre for Translational Pharmacology, Institute of Molecular, Cell and Systems Biology, University of Glasgow, Davidson Building, Glasgow G12 8QQ, U.K
| | - Mark Huggett
- BioAscent Discovery Ltd., Newhouse, Lanarkshire ML1 5UH, U.K.,European Screening Centre, University of Dundee, Newhouse, Lanarkshire ML1 5UH, U.K
| | - Margaret Huggett
- BioAscent Discovery Ltd., Newhouse, Lanarkshire ML1 5UH, U.K.,European Screening Centre, University of Dundee, Newhouse, Lanarkshire ML1 5UH, U.K
| | - Lindsay Robinson
- BioAscent Discovery Ltd., Newhouse, Lanarkshire ML1 5UH, U.K.,European Screening Centre, University of Dundee, Newhouse, Lanarkshire ML1 5UH, U.K
| | - Jonathan Gillespie
- BioAscent Discovery Ltd., Newhouse, Lanarkshire ML1 5UH, U.K.,European Screening Centre, University of Dundee, Newhouse, Lanarkshire ML1 5UH, U.K
| | - Muralikrishnan Rajamanickam
- BioAscent Discovery Ltd., Newhouse, Lanarkshire ML1 5UH, U.K.,European Screening Centre, University of Dundee, Newhouse, Lanarkshire ML1 5UH, U.K
| | - Angus Morrison
- BioAscent Discovery Ltd., Newhouse, Lanarkshire ML1 5UH, U.K.,European Screening Centre, University of Dundee, Newhouse, Lanarkshire ML1 5UH, U.K
| | - Stuart McElroy
- BioAscent Discovery Ltd., Newhouse, Lanarkshire ML1 5UH, U.K.,European Screening Centre, University of Dundee, Newhouse, Lanarkshire ML1 5UH, U.K
| | - Irina G Tikhonova
- School of Pharmacy, Medical Biology Centre, Queen's University Belfast, Belfast BT9 7BL, U.K
| | - Graeme Milligan
- Centre for Translational Pharmacology, Institute of Molecular, Cell and Systems Biology, University of Glasgow, Davidson Building, Glasgow G12 8QQ, U.K
| | - Andrew G Jamieson
- School of Chemistry, University of Glasgow, Joseph Black Building, University Avenue, Glasgow G12 8QQ, U.K
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9
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Gbahou F, Levin S, Tikhonova IG, Somalo Barranco G, Izabelle C, Ohana RF, Jockers R. Luminogenic HiBiT Peptide-Based NanoBRET Ligand Binding Assays for Melatonin Receptors. ACS Pharmacol Transl Sci 2022; 5:668-678. [DOI: 10.1021/acsptsci.2c00096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2022] [Indexed: 11/28/2022]
Affiliation(s)
- Florence Gbahou
- Université Paris Cité, Institut Cochin, INSERM, CNRS, 75014 Paris, France
| | - Sergiy Levin
- Promega Corporation, Fitchburg, Wisconsin 53711, United States
| | - Irina G. Tikhonova
- School of Pharmacy, Medical Biology Centre, Queen’s University Belfast, Belfast BT9 7BL, United Kingdom
| | | | - Charlotte Izabelle
- Université Paris Cité, Institut Cochin, INSERM, CNRS, 75014 Paris, France
| | | | - Ralf Jockers
- Université Paris Cité, Institut Cochin, INSERM, CNRS, 75014 Paris, France
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10
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Marsango S, Ward RJ, Jenkins L, Butcher AJ, Al Mahmud Z, Dwomoh L, Nagel F, Schulz S, Tikhonova IG, Tobin AB, Milligan G. Selective phosphorylation of threonine residues defines GPR84-arrestin interactions of biased ligands. J Biol Chem 2022; 298:101932. [PMID: 35427647 PMCID: PMC9118924 DOI: 10.1016/j.jbc.2022.101932] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Revised: 04/04/2022] [Accepted: 04/05/2022] [Indexed: 11/13/2022] Open
Abstract
GPR84 is an immune cell-expressed, proinflammatory receptor currently being assessed as a therapeutic target in conditions including fibrosis and inflammatory bowel disease. Although it was previously shown that the orthosteric GPR84 activators 2-HTP and 6-OAU promoted its interactions with arrestin-3, a G protein-biased agonist DL-175 did not. Here, we show that replacement of all 21 serine and threonine residues within i-loop 3 of GPR84, but not the two serines in the C-terminal tail, eliminated the incorporation of [32P] and greatly reduced receptor-arrestin-3 interactions promoted by 2-HTP. GPR84 was phosphorylated constitutively on residues Ser221 and Ser224, while various other amino acids are phosphorylated in response to 2-HTP. Consistent with this, an antiserum able to identify pSer221/pSer224 recognized GPR84 from cells treated with and without activators, whereas an antiserum able to identify pThr263/pThr264 only recognized GPR84 after exposure to 2-HTP and not DL-175. Two distinct GPR84 antagonists as well as inhibition of G protein-coupled receptor kinase 2/3 prevented phosphorylation of pThr263/pThr264, but neither strategy affected constitutive phosphorylation of Ser221/Ser224. Furthermore, mutation of residues Thr263 and Thr264 to alanine generated a variant of GPR84 also limited in 2-HTP-induced interactions with arrestin-2 and -3. By contrast, this mutant was unaffected in its capacity to reduce cAMP levels. Taken together, these results define a key pair of threonine residues, regulated only by subsets of GPR84 small molecule activators and by GRK2/3 that define effective interactions with arrestins and provide novel tools to monitor the phosphorylation and functional status of GPR84.
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Affiliation(s)
- Sara Marsango
- The Centre for Translational Pharmacology, Institute of Molecular, Cellular and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Richard J Ward
- The Centre for Translational Pharmacology, Institute of Molecular, Cellular and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Laura Jenkins
- The Centre for Translational Pharmacology, Institute of Molecular, Cellular and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Adrian J Butcher
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom
| | - Zobaer Al Mahmud
- The Centre for Translational Pharmacology, Institute of Molecular, Cellular and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Louis Dwomoh
- The Centre for Translational Pharmacology, Institute of Molecular, Cellular and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | | | - Stefan Schulz
- 7TM Antibodies GmbH, Jena, Germany; Institute of Pharmacology and Toxicology, University Hospital Jena, Jena, Germany
| | - Irina G Tikhonova
- School of Pharmacy, Medical Biology Centre, Queen's University Belfast, Belfast, United Kingdom
| | - Andrew B Tobin
- The Centre for Translational Pharmacology, Institute of Molecular, Cellular and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Graeme Milligan
- The Centre for Translational Pharmacology, Institute of Molecular, Cellular and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom.
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11
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Yoval-Sánchez B, Ansari F, James J, Niatsetskaya Z, Sosunov S, Filipenko P, Tikhonova IG, Ten V, Wittig I, Rafikov R, Galkin A. Redox-dependent loss of flavin by mitochondria complex I is different in brain and heart. Redox Biol 2022; 51:102258. [PMID: 35189550 PMCID: PMC8861397 DOI: 10.1016/j.redox.2022.102258] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 01/26/2022] [Accepted: 01/31/2022] [Indexed: 12/14/2022] Open
Abstract
Pathologies associated with tissue ischemia/reperfusion (I/R) in highly metabolizing organs such as the brain and heart are leading causes of death and disability in humans. Molecular mechanisms underlying mitochondrial dysfunction during acute injury in I/R are tissue-specific, but their details are not completely understood. A metabolic shift and accumulation of substrates of reverse electron transfer (RET) such as succinate are observed in tissue ischemia, making mitochondrial complex I of the respiratory chain (NADH:ubiquinone oxidoreductase) the most vulnerable enzyme to the following reperfusion. It has been shown that brain complex I is predisposed to losing its flavin mononucleotide (FMN) cofactor when maintained in the reduced state in conditions of RET both in vitro and in vivo. Here we investigated the process of redox-dependent dissociation of FMN from mitochondrial complex I in brain and heart mitochondria. In contrast to the brain enzyme, cardiac complex I does not lose FMN when reduced in RET conditions. We proposed that the different kinetics of FMN loss during RET is due to the presence of brain-specific long 50 kDa isoform of the NDUFV3 subunit of complex I, which is absent in the heart where only the canonical 10 kDa short isoform is found. Our simulation studies suggest that the long NDUFV3 isoform can reach toward the FMN binding pocket and affect the nucleotide affinity to the apoenzyme. For the first time, we demonstrated a potential functional role of tissue-specific isoforms of complex I, providing the distinct molecular mechanism of I/R-induced mitochondrial impairment in cardiac and cerebral tissues. By combining functional studies of intact complex I and molecular structure simulations, we defined the critical difference between the brain and heart enzyme and suggested insights into the redox-dependent inactivation mechanisms of complex I during I/R injury in both tissues.
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Affiliation(s)
- Belem Yoval-Sánchez
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, 407 East 61st Street, New York, NY, 10065, USA
| | - Fariha Ansari
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, 407 East 61st Street, New York, NY, 10065, USA
| | - Joel James
- Division of Endocrinology, Department of Medicine, University of Arizona College of Medicine, Tucson, AZ, USA
| | - Zoya Niatsetskaya
- Department of Pediatrics, Rutgers-Robert Wood Johnson Medical School, New Brunswick, NJ, 08901, USA
| | - Sergey Sosunov
- Department of Pediatrics, Rutgers-Robert Wood Johnson Medical School, New Brunswick, NJ, 08901, USA
| | - Peter Filipenko
- Department of Biochemistry, Weill Cornell Medical College, Cornell University, New York, NY, 10021, USA
| | - Irina G. Tikhonova
- School of Pharmacy, Medical Biology, Centre, Queen's University Belfast, Belfast, BT9 7BL, United Kingdom
| | - Vadim Ten
- Department of Pediatrics, Rutgers-Robert Wood Johnson Medical School, New Brunswick, NJ, 08901, USA
| | - Ilka Wittig
- Functional Proteomics, Cardiovascular Physiology, Goethe University, 60590, Frankfurt am Main, Germany,German Center for Cardiovascular Research (DZHK), Partner site RheinMain, Frankfurt, Germany
| | - Ruslan Rafikov
- Division of Endocrinology, Department of Medicine, University of Arizona College of Medicine, Tucson, AZ, USA
| | - Alexander Galkin
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, 407 East 61st Street, New York, NY, 10065, USA,Corresponding author.
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12
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Ciancetta A, Gill AK, Ding T, Karlov DS, Chalhoub G, McCormick PJ, Tikhonova IG. Probe Confined Dynamic Mapping for G Protein-Coupled Receptor Allosteric Site Prediction. ACS Cent Sci 2021; 7:1847-1862. [PMID: 34841058 PMCID: PMC8614102 DOI: 10.1021/acscentsci.1c00802] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Indexed: 05/06/2023]
Abstract
Targeting G protein-coupled receptors (GPCRs) through allosteric sites offers advantages over orthosteric sites in identifying drugs with increased selectivity and potentially reduced side effects. In this study, we developed a probe confined dynamic mapping protocol that allows the prediction of allosteric sites at both the GPCR extracellular and intracellular sides, as well as at the receptor-lipid interface. The applied harmonic wall potential enhanced sampling of probe molecules in a selected area of a GPCR while preventing membrane distortion in molecular dynamics simulations. The specific probes derived from GPCR allosteric ligand structures performed better in allosteric site mapping compared to commonly used cosolvents. The M2 muscarinic, β2 adrenergic, and P2Y1 purinergic receptors were selected for the protocol's retrospective validation. The protocol was next validated prospectively to locate the binding site of [5-fluoro-4-(hydroxymethyl)-2-methoxyphenyl]-(4-fluoro-1H-indol-1-yl)methanone at the D2 dopamine receptor, and subsequent mutagenesis confirmed the prediction. The protocol provides fast and efficient prediction of key amino acid residues surrounding allosteric sites in membrane proteins and facilitates the structure-based design of allosteric modulators.
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Affiliation(s)
- Antonella Ciancetta
- School
of Pharmacy, Medical Biology Centre, Queen’s
University Belfast, Belfast, Northern Ireland BT9 7BL, U.K.
| | - Amandeep Kaur Gill
- Centre
for Endocrinology, William Harvey Research Institute, Bart’s
and the London School of Medicine and Dentistry, Queen
Mary, University of London, London, EC1M 6BQ, U.K.
| | - Tianyi Ding
- School
of Pharmacy, Medical Biology Centre, Queen’s
University Belfast, Belfast, Northern Ireland BT9 7BL, U.K.
| | - Dmitry S. Karlov
- School
of Pharmacy, Medical Biology Centre, Queen’s
University Belfast, Belfast, Northern Ireland BT9 7BL, U.K.
| | - George Chalhoub
- Centre
for Endocrinology, William Harvey Research Institute, Bart’s
and the London School of Medicine and Dentistry, Queen
Mary, University of London, London, EC1M 6BQ, U.K.
| | - Peter J. McCormick
- Centre
for Endocrinology, William Harvey Research Institute, Bart’s
and the London School of Medicine and Dentistry, Queen
Mary, University of London, London, EC1M 6BQ, U.K.
| | - Irina G. Tikhonova
- School
of Pharmacy, Medical Biology Centre, Queen’s
University Belfast, Belfast, Northern Ireland BT9 7BL, U.K.
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13
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Jenkins L, Marsango S, Mancini S, Mahmud ZA, Morrison A, McElroy SP, Bennett KA, Barnes M, Tobin AB, Tikhonova IG, Milligan G. Discovery and Characterization of Novel Antagonists of the Proinflammatory Orphan Receptor GPR84. ACS Pharmacol Transl Sci 2021; 4:1598-1613. [PMID: 34661077 PMCID: PMC8506611 DOI: 10.1021/acsptsci.1c00151] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Indexed: 01/30/2023]
Abstract
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GPR84 is a poorly
characterized, nominally orphan, proinflammatory
G protein-coupled receptor that can be activated by medium chain length
fatty acids. It is attracting considerable interest as a potential
therapeutic target for antagonist ligands in both inflammatory bowel
diseases and idiopathic pulmonary fibrosis. Successful screening of
more than 300 000 compounds from a small molecule library followed
by detailed analysis of some 50 drug-like hits identified 3-((5,6-bis(4-methoxyphenyl)-1,2,4-triazin-3-yl)methyl)-1H-indole as a high affinity and highly selective competitive
antagonist of human GPR84. Tritiation of a di-iodinated form of the
core structure produced [3H]3-((5,6-diphenyl-1,2,4-triazin-3-yl)methyl)-1H-indole, which allowed effective measurement of receptor
levels in both transfected cell lines and lipopolysaccharide-treated
THP-1 monocyte/macrophage cells. Although this compound series lacks
significant affinity at mouse GPR84, homology modeling and molecular
dynamics simulations provided a potential rationale for this difference,
and alteration of two residues in mouse GPR84 to the equivalent amino
acids in the human orthologue, predicted to open the antagonist binding
pocket, validated this model. Sequence alignment of other species
orthologues further predicted binding of the compounds as high affinity
antagonists at macaque, pig, and dog GPR84 but not at the rat orthologue,
and pharmacological experiments confirmed these predictions. These
studies provide a new class of GPR84 antagonists that display species
selectivity defined via receptor modeling and mutagenesis.
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Affiliation(s)
- Laura Jenkins
- The Centre for Translational Pharmacology, Institute of Molecular, Cellular and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - Sara Marsango
- The Centre for Translational Pharmacology, Institute of Molecular, Cellular and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - Sarah Mancini
- The Centre for Translational Pharmacology, Institute of Molecular, Cellular and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - Zobaer Al Mahmud
- The Centre for Translational Pharmacology, Institute of Molecular, Cellular and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - Angus Morrison
- BioAscent Discovery Ltd., Bo'Ness Road, Newhouse, Lanarkshire ML1 5UH, United Kingdom
| | - Stuart P McElroy
- BioAscent Discovery Ltd., Bo'Ness Road, Newhouse, Lanarkshire ML1 5UH, United Kingdom
| | - Kirstie A Bennett
- Sosei Heptares, Steinmetz Building, Granta Park, Great Abington, Cambridge CB21 6DG, United Kingdom
| | - Matt Barnes
- Sosei Heptares, Steinmetz Building, Granta Park, Great Abington, Cambridge CB21 6DG, United Kingdom
| | - Andrew B Tobin
- The Centre for Translational Pharmacology, Institute of Molecular, Cellular and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - Irina G Tikhonova
- School of Pharmacy, Medical Biology Centre, Queen's University Belfast, Belfast BT9 7BL, United Kingdom
| | - Graeme Milligan
- The Centre for Translational Pharmacology, Institute of Molecular, Cellular and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom
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14
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Olatunji S, Bowen K, Huang CY, Weichert D, Singh W, Tikhonova IG, Scanlan EM, Olieric V, Caffrey M. Structural basis of the membrane intramolecular transacylase reaction responsible for lyso-form lipoprotein synthesis. Nat Commun 2021; 12:4254. [PMID: 34253723 PMCID: PMC8275575 DOI: 10.1038/s41467-021-24475-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Accepted: 06/08/2021] [Indexed: 11/08/2022] Open
Abstract
Lipoproteins serve diverse functions in the bacterial cell and some are essential for survival. Some lipoproteins are adjuvants eliciting responses from the innate immune system of the host. The growing list of membrane enzymes responsible for lipoprotein synthesis includes the recently discovered lipoprotein intramolecular transacylase, Lit. Lit creates a lipoprotein that is less immunogenic, possibly enabling the bacteria to gain a foothold in the host by stealth. Here, we report the crystal structure of the Lit enzyme from Bacillus cereus and describe its mechanism of action. Lit consists of four transmembrane helices with an extracellular cap. Conserved residues map to the cap-membrane interface. They include two catalytic histidines that function to effect unimolecular transacylation. The reaction involves acyl transfer from the sn-2 position of the glyceryl moiety to the amino group on the N-terminal cysteine of the substrate via an 8-membered ring intermediate. Transacylation takes place in a confined aromatic residue-rich environment that likely evolved to bring distant moieties on the substrate into proximity and proper orientation for catalysis.
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Affiliation(s)
- Samir Olatunji
- Membrane Structural and Functional Biology Group, School of Medicine and School of Biochemistry and Immunology, Trinity College Dublin, Dublin, Ireland
| | - Katherine Bowen
- School of Chemistry, Trinity College Dublin, Dublin, Ireland
| | - Chia-Ying Huang
- Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland
| | - Dietmar Weichert
- Membrane Structural and Functional Biology Group, School of Medicine and School of Biochemistry and Immunology, Trinity College Dublin, Dublin, Ireland
| | - Warispreet Singh
- School of Pharmacy, Queen's University Belfast, Belfast, United Kingdom
- Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, United Kingdom
- Hub for Biotechnology in Build Environment, Newcastle upon Tyne, United Kingdom
| | - Irina G Tikhonova
- School of Pharmacy, Queen's University Belfast, Belfast, United Kingdom
| | - Eoin M Scanlan
- School of Chemistry, Trinity College Dublin, Dublin, Ireland
| | - Vincent Olieric
- Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland
| | - Martin Caffrey
- Membrane Structural and Functional Biology Group, School of Medicine and School of Biochemistry and Immunology, Trinity College Dublin, Dublin, Ireland.
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15
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Pritsch IC, Tikhonova IG, Jewhurst HL, Drysdale O, Cwiklinski K, Molento MB, Dalton JP, Verissimo CDM. Regulation of the Fasciola hepatica newly excysted juvenile cathepsin L3 (FhCL3) by its propeptide: a proposed 'clamp-like' mechanism of binding and inhibition. BMC Mol Cell Biol 2020; 21:90. [PMID: 33287692 PMCID: PMC7720491 DOI: 10.1186/s12860-020-00335-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 11/26/2020] [Indexed: 01/25/2023] Open
Abstract
BACKGROUND The zoonotic worm parasite Fasciola hepatica secretes an abundance of cathepsin L peptidases that are associated with virulence, invasiveness, feeding and migration. The peptidases are produced as inactive zymogens that activate at low pH by autocatalytic removal of their N-terminal pro-domain or propeptide. Propeptides bind to their cognate enzyme with high specificity. Little is known, however, about the mechanism by which the propeptide of FhCL3, a cathepsin L peptidase secreted by the infective newly excysted juveniles (NEJs), regulates the inhibition and activation of the mature enzyme before it is secreted into host tissues. RESULTS Immunolocalisation/immunoblotting studies show that the FhCL3 zymogen is produced and secreted by gastrodermal cells of the NEJs gut. A recombinant propeptide of FhCL3 (ppFhCL3) was shown to be a highly potent and selective inhibitor of native and recombinant F. hepatica FhCL3 peptidase, and other members of the cathepsin L family; inhibition constant (Ki) values obtained for FhCL1, FhCL2 and FhCL3 were 0.04 nM, 0.004 nM and < 0.002 nM, respectively. These values are at least 1000-fold lower than those Ki obtained for human cathepsin L (HsCL) and human cathepsin K (HsCK) demonstrating the selectivity of the ppFhCL3 for parasite cathepsins L. By exploiting 3-D structural data we identified key molecular interactions in the specific binding between the ppFhCL3 and FhCL3 mature domain. Using recombinant variants of ppFhCL3 we demonstrated the critical importance of a pair of propeptide residues (Tyr46Lys47) for the interaction with the propeptide binding loop (PBL) of the mature enzyme and other residues (Leu66 and Glu68) that allow the propeptide to block the active site. CONCLUSIONS The FhCL3 peptidase involved in host invasion by F. hepatica is produced as a zymogen in the NEJs gut. Regulation of its activation involves specific binding sites within the propeptide that are interdependent and act as a "clamp-like" mechanism of inhibition. These interactions are disrupted by the low pH of the NEJs gut to initiate autocatalytic activation. Our enzyme kinetics data demonstrates high potency and selectivity of the ppFhCL3 for its cognate FhCL3 enzyme, information that could be utilised to design inhibitors of parasite cathepsin L peptidases.
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Affiliation(s)
- Izanara C Pritsch
- Department of Basic Pathology, Federal University of Parana, Curitiba, 81531-970, Brazil.,School of Biological Sciences, Queen's University Belfast, Belfast, Northern Ireland, UK
| | - Irina G Tikhonova
- School of Pharmacy, Medical Biology Centre, Queen's University Belfast, Belfast, BT9 7BL, UK
| | - Heather L Jewhurst
- School of Biological Sciences, Queen's University Belfast, Belfast, Northern Ireland, UK.,Centre for One Health and Ryan Institute, School of Natural Sciences, National University of Ireland Galway, Galway, Ireland
| | - Orla Drysdale
- School of Biological Sciences, Queen's University Belfast, Belfast, Northern Ireland, UK
| | - Krystyna Cwiklinski
- School of Biological Sciences, Queen's University Belfast, Belfast, Northern Ireland, UK.,Centre for One Health and Ryan Institute, School of Natural Sciences, National University of Ireland Galway, Galway, Ireland
| | - Marcelo B Molento
- Department of Basic Pathology, Federal University of Parana, Curitiba, 81531-970, Brazil.,Department of Veterinary Medicine, Federal University of Parana, Curitiba, Paraná, Brazil
| | - John P Dalton
- School of Biological Sciences, Queen's University Belfast, Belfast, Northern Ireland, UK.,Centre for One Health and Ryan Institute, School of Natural Sciences, National University of Ireland Galway, Galway, Ireland
| | - Carolina De M Verissimo
- School of Biological Sciences, Queen's University Belfast, Belfast, Northern Ireland, UK. .,Centre for One Health and Ryan Institute, School of Natural Sciences, National University of Ireland Galway, Galway, Ireland.
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16
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De Marco Verissimo C, Jewhurst HL, Tikhonova IG, Urbanus RT, Maule AG, Dalton JP, Cwiklinski K. Fasciola hepatica serine protease inhibitor family (serpins): Purposely crafted for regulating host proteases. PLoS Negl Trop Dis 2020; 14:e0008510. [PMID: 32760059 PMCID: PMC7437470 DOI: 10.1371/journal.pntd.0008510] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Revised: 08/18/2020] [Accepted: 06/22/2020] [Indexed: 11/18/2022] Open
Abstract
Serine protease inhibitors (serpins) regulate proteolytic events within diverse biological processes, including digestion, coagulation, inflammation and immune responses. The presence of serpins in Fasciola hepatica excretory-secretory products indicates that the parasite exploits these to regulate proteases encountered during its development within vertebrate hosts. Interrogation of the F. hepatica genome identified a multi-gene serpin family of seven members that has expanded by gene duplication and divergence to create an array of inhibitors with distinct specificities. We investigated the molecular properties and functions of two representatives, FhSrp1 and FhSrp2, highly expressed in the invasive newly excysted juvenile (NEJ). Consistent with marked differences in the reactive centre loop (RCL) that executes inhibitor-protease complexing, the two recombinant F. hepatica serpins displayed distinct inhibitory profiles against an array of mammalian serine proteases. In particular, rFhSrp1 efficiently inhibited kallikrein (Ki = 40 nM) whilst rFhSrp2 was a highly potent inhibitor of chymotrypsin (Ki = 0.07 nM). FhSrp1 and FhSrp2 are both expressed on the NEJ surface, predominantly around the oral and ventral suckers, suggesting that these inhibitors protect the parasites from the harmful proteolytic effects of host proteases, such as chymotrypsin, during invasion. Furthermore, the unusual inhibition of kallikrein suggests that rFhSrp1 modulates host responses such as inflammation and vascular permeability by interfering with the kallikrein-kinin system. A vaccine combination of rFhSrp1 and rFhSrp2 formulated in the adjuvant Montanide ISA 206VG elicited modest but non-significant protection against a challenge infection in a rat model, but did induce some protection against liver pathogenesis when compared to a control group and a group vaccinated with two well-studied vaccine candidates, F. hepatica cathepsin L2 and L3. This work highlights the importance of F. hepatica serpins to regulate host responses that enables parasite survival during infection and, coupled with the vaccine data, encourages future vaccine trials in ruminants. Serpins are protease inhibitors that regulate various biological processes, including digestion, blood coagulation, inflammation and immune responses. The liver fluke, Fasciola hepatica, produces an array of inhibitors to regulate proteolytic enzymes they encounter during development within the mammalian host. In this study, we identified seven different serpins that have evolved to inhibit a range of host proteases. In particular, we characterized two representatives, FhSrp1 and FhSrp2, that we found highly expressed on the surface of the invasive newly excysted juvenile (NEJ), suggesting that they protect the parasites from harmful proteolytic effects during invasion. Contrasting inhibitory profiles were observed; while recombinant FhSrp1 inhibited kallikrein, recombinant FhSrp2 was a highly potent inhibitor of chymotrypsin. The unusual inhibition of kallikrein suggests that rFhSrp1 influences host responses such as inflammation and vascular permeability by interfering with the kallikrein-kinin system. Conversely, chymotrypsin is typically inhibited by trematode-specific serpins, implying a conserved mechanism to regulate digestive enzymes. The ability of the liver fluke serpin family to inhibit such an array of proteases highlights the importance of these inhibitors in parasite-host interactions and encourages future investigations of serpins as candidate anti-parasite vaccine targets for the control of fasciolosis in ruminants.
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Affiliation(s)
- Carolina De Marco Verissimo
- Centre for One Health and Ryan Institute, School of Natural Sciences, National University of Ireland Galway, Galway, Ireland
- * E-mail:
| | - Heather L. Jewhurst
- Centre for One Health and Ryan Institute, School of Natural Sciences, National University of Ireland Galway, Galway, Ireland
| | - Irina G. Tikhonova
- School of Pharmacy, Medical Biology Centre, Queen's University Belfast, Belfast, United Kingdom
| | - Rolf T. Urbanus
- Thrombosis and Hemostasis Laboratory, Department of Clinical Chemistry and Hematology, University Medical Center Utrecht, Utrecht, Netherlands
| | - Aaron G. Maule
- Microbe & Pathogen Biology, The Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, Belfast, United Kingdom
| | - John P. Dalton
- Centre for One Health and Ryan Institute, School of Natural Sciences, National University of Ireland Galway, Galway, Ireland
| | - Krystyna Cwiklinski
- Centre for One Health and Ryan Institute, School of Natural Sciences, National University of Ireland Galway, Galway, Ireland
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17
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Reubi JC, Fourmy D, Cordomi A, Tikhonova IG, Gigoux V. GIP receptor: Expression in neuroendocrine tumours, internalization, signalling from endosomes and structure-function relationship studies. Peptides 2020; 125:170229. [PMID: 31857104 DOI: 10.1016/j.peptides.2019.170229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Revised: 12/04/2019] [Accepted: 12/05/2019] [Indexed: 10/25/2022]
Abstract
GIP is well known as a peptide regulating metabolic functions. In this review paper, we summarize a series of data on GIP receptor (GIPR). First, expression study of GIPR in human neuroendocrine tumours showed a very high incidence (nearly 100%) and a high density in both functional and non functional pancreatic tumours, ileal tumours, bronchial tumours and medullary thyroid carcinomas. Then, data on internalization of GIPR following stimulation by GIP are reported. Rapid and abundant internalization of GIPR also found in tumor pancreatic endocrine cells opens the possibility of tumor imaging and eradication using radiolabeled GIP. Interestingly, internalized GIPR continues to signal in early endosomes stimulating production of cAMP and activation of PKA, thus, supporting the view that GIPR signals from both plasma membrane and vesicles of internalization. At last, we summarize data from studies using in synergy molecular modeling and site-directed mutagenesis, which identified crucial amino acids of transmembrane domains of GIPR involved in GIPR binding site of GIP and/or in its activation and coupling to Gs protein. All together, these last molecular data may help to better understand structure-activity relationship data on GIP and GIPR.
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Affiliation(s)
- Jean Claude Reubi
- Cell Biology and Experimental Cancer Research, Institute of Pathology, University of Berne, CH-3010 Berne, Switzerland.
| | - Daniel Fourmy
- LPCNO, ERL 1226 INSERM, Université De Toulouse, CNRS, INSA, UPS, 135 Avenue De RAngueil, 31077 Toulouse, France.
| | - Arnau Cordomi
- Laboratori De Medicina Computacional, Unitat De Bioestadística, Facultat De Medicina, Universitat Autònoma De Barcelona, Barcelona, Spain.
| | - Irina G Tikhonova
- School of Pharmacy, Medical Biology Centre, Queen's University Belfast, Belfast BT9 7BL, Northern Ireland, United Kingdom.
| | - Véronique Gigoux
- LPCNO, ERL 1226 INSERM, Université De Toulouse, CNRS, INSA, UPS, 135 Avenue De RAngueil, 31077 Toulouse, France.
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18
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Tikhonova IG, Gigoux V, Fourmy D. Understanding Peptide Binding in Class A G Protein-Coupled Receptors. Mol Pharmacol 2019; 96:550-561. [PMID: 31436539 DOI: 10.1124/mol.119.115915] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Accepted: 06/13/2019] [Indexed: 12/13/2022] Open
Abstract
Many physiologic processes are controlled through the activation of G protein-coupled receptors (GPCRs) by regulatory peptides, making peptide GPCRs particularly useful targets for major human diseases such as diabetes and cancer. Peptide GPCRs are also being evaluated as next-generation targets for the development of novel antiparasite agents and insecticides in veterinary medicine and agriculture. Resolution of crystal structures for several peptide GPCRs has advanced our understanding of peptide-receptor interactions and fueled interest in correlating peptide heterogeneity with receptor-binding properties. In this review, the knowledge of recently crystalized peptide-GPCR complexes, previously accumulated peptide structure-activity relationship studies, receptor mutagenesis, and sequence alignment are integrated to better understand peptide binding to the transmembrane cavity of class A GPCRs. Using SAR data, we show that peptide class A GPCRs can be divided into groups with distinct hydrophilic residues. These characteristic residues help explain the preference of a receptor to bind the C-terminal free carboxyl group, the C-terminal amidated group, or the N-terminal ammonium group of peptides.
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Affiliation(s)
- Irina G Tikhonova
- School of Pharmacy, Medical Biology Centre, Queen's University Belfast, Belfast, Northern Ireland, United Kingdom, (I.G.T.) and INSERM ERL1226-Receptology and Therapeutic Targeting of Cancers, Laboratoire de Physique et Chimie des Nano-Objets, CNRS UMR5215-INSA, Université de Toulouse III, Toulouse, France (V.G., D.F.)
| | - Veronique Gigoux
- School of Pharmacy, Medical Biology Centre, Queen's University Belfast, Belfast, Northern Ireland, United Kingdom, (I.G.T.) and INSERM ERL1226-Receptology and Therapeutic Targeting of Cancers, Laboratoire de Physique et Chimie des Nano-Objets, CNRS UMR5215-INSA, Université de Toulouse III, Toulouse, France (V.G., D.F.)
| | - Daniel Fourmy
- School of Pharmacy, Medical Biology Centre, Queen's University Belfast, Belfast, Northern Ireland, United Kingdom, (I.G.T.) and INSERM ERL1226-Receptology and Therapeutic Targeting of Cancers, Laboratoire de Physique et Chimie des Nano-Objets, CNRS UMR5215-INSA, Université de Toulouse III, Toulouse, France (V.G., D.F.)
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19
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Moore DS, Brines C, Jewhurst H, Dalton JP, Tikhonova IG. Steered molecular dynamics simulations reveal critical residues for (un)binding of substrates, inhibitors and a product to the malarial M1 aminopeptidase. PLoS Comput Biol 2018; 14:e1006525. [PMID: 30379805 PMCID: PMC6239339 DOI: 10.1371/journal.pcbi.1006525] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Revised: 11/16/2018] [Accepted: 09/21/2018] [Indexed: 12/26/2022] Open
Abstract
Malaria is a life-threatening disease spread by mosquitoes. Plasmodium falciparum M1 alanyl aminopeptidase (PfM1-AAP) is a promising target for the treatment of malaria. The recently solved crystal structures of PfM1-AAP revealed that the buried active site can be accessed through two channel openings: a short N-terminal channel with the length of 8 Å and a long C-terminal channel with the length of 30 Å. It is unclear, however, how substrates and inhibitors migrate to the active site and a product of cleavage leaves. Here, we study the molecular mechanism of substrate and inhibitor migration to the active site and the product release using steered molecular dynamics simulations. We identified a stepwise passage of substrates and inhibitors in the C-terminal channel of PfM1-AAP, involving (I) ligand recognition at the opening of the channel, (II) ionic translation to the 'water reservoir', (III) ligand reorientation in the 'water reservoir' and (IV) passage in a suitable conformation into the active site. Endorsed by enzymatic analysis of functional recombinant PfM1-AAP and mutagenesis studies, our novel ligand-residue binding network analysis has identified the functional residues controlling ligand migration within the C-terminal channel of PfM1-AAP. Furthermore, from unbinding simulations of the Arg product we propose a charge repulsion as the driving force to expel the product out from the N-terminal channel of PfM1-AAP. Our work paves the way towards the design of a novel class of PfM1-AAP inhibitors based on preventing substrate entry to the active site.
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Affiliation(s)
- Daniel S Moore
- School of Pharmacy, Medical Biology Centre, Queen's University Belfast, Belfast, Northern Ireland, United Kingdom
| | - Conor Brines
- School of Biological Sciences, Medical Biology Centre, Queen's University Belfast, Belfast, Northern Ireland, United Kingdom
| | - Heather Jewhurst
- School of Biological Sciences, Medical Biology Centre, Queen's University Belfast, Belfast, Northern Ireland, United Kingdom
| | - John P Dalton
- School of Biological Sciences, Medical Biology Centre, Queen's University Belfast, Belfast, Northern Ireland, United Kingdom
| | - Irina G Tikhonova
- School of Pharmacy, Medical Biology Centre, Queen's University Belfast, Belfast, Northern Ireland, United Kingdom
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Mahmud ZA, Jenkins L, Ulven T, Labéguère F, Gosmini R, De Vos S, Hudson BD, Tikhonova IG, Milligan G. Three classes of ligands each bind to distinct sites on the orphan G protein-coupled receptor GPR84. Sci Rep 2017; 7:17953. [PMID: 29263400 PMCID: PMC5738391 DOI: 10.1038/s41598-017-18159-3] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Accepted: 12/05/2017] [Indexed: 12/18/2022] Open
Abstract
Medium chain fatty acids can activate the pro-inflammatory receptor GPR84 but so also can molecules related to 3,3′-diindolylmethane. 3,3′-Diindolylmethane and decanoic acid acted as strong positive allosteric modulators of the function of each other and analysis showed the affinity of 3,3′-diindolylmethane to be at least 100 fold higher. Methyl decanoate was not an agonist at GPR84. This implies a key role in binding for the carboxylic acid of the fatty acid. Via homology modelling we predicted and confirmed an integral role of arginine172, located in the 2nd extracellular loop, in the action of decanoic acid but not of 3,3′-diindolylmethane. Exemplars from a patented series of GPR84 antagonists were able to block agonist actions of both decanoic acid and 3,3′-diindolylmethane at GPR84. However, although a radiolabelled form of a related antagonist, [3H]G9543, was able to bind with high affinity to GPR84, this was not competed for by increasing concentrations of either decanoic acid or 3,3′-diindolylmethane and was not affected adversely by mutation of arginine172. These studies identify three separable ligand binding sites within GPR84 and suggest that if medium chain fatty acids are true endogenous regulators then co-binding with a positive allosteric modulator would greatly enhance their function in physiological settings.
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Affiliation(s)
- Zobaer Al Mahmud
- Centre for Translational Pharmacology, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow Glasgow, G12 8QQ, Scotland, United Kingdom
| | - Laura Jenkins
- Centre for Translational Pharmacology, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow Glasgow, G12 8QQ, Scotland, United Kingdom
| | - Trond Ulven
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, DK-5230, Odense M, Denmark
| | - Frédéric Labéguère
- Galapagos SASU, 102 Avenue Gaston Roussel, 93230, Romainville, France.,Evotec, 195 Route d'Espagne, 31100, Toulouse, France
| | - Romain Gosmini
- Galapagos SASU, 102 Avenue Gaston Roussel, 93230, Romainville, France
| | - Steve De Vos
- Galapagos NV, Generaal De Wittelaan L11 A3, 2800, Mechelen, Belgium
| | - Brian D Hudson
- Centre for Translational Pharmacology, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow Glasgow, G12 8QQ, Scotland, United Kingdom
| | - Irina G Tikhonova
- School of Pharmacy, Medical Biology Centre, Queen's University Belfast, Belfast, BT9 7BL, United Kingdom
| | - Graeme Milligan
- Centre for Translational Pharmacology, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow Glasgow, G12 8QQ, Scotland, United Kingdom.
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Krasavin M, Lukin A, Bakholdina A, Zhurilo N, Onopchenko O, Borysko P, Zozulya S, Moore D, Tikhonova IG. Continued SAR exploration of 1,2,4-thiadiazole-containing scaffolds in the design of free fatty acid receptor 1 (GPR40) agonists. Eur J Med Chem 2017; 140:229-238. [DOI: 10.1016/j.ejmech.2017.09.019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Revised: 09/10/2017] [Accepted: 09/11/2017] [Indexed: 12/11/2022]
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Dib K, Tikhonova IG, Ivetic A, Schu P. The cytoplasmic tail of L-selectin interacts with the adaptor-protein complex AP-1 subunit μ1A via a novel basic binding motif. J Biol Chem 2017; 292:6703-6714. [PMID: 28235798 DOI: 10.1074/jbc.m116.768598] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Revised: 01/30/2017] [Indexed: 01/02/2023] Open
Abstract
L-selectin regulates leukocyte adhesion and rolling along the endothelium. Proteins binding to the cytoplasmic tail of L-selectin regulate L-selectin functions. We used L-selectin cytoplasmic tail peptide pulldown assays combined with high sensitivity liquid chromatography/mass spectrometry to identify novel L-selectin tail-binding proteins. Incubation of the L-selectin tail with cell extracts from phorbol 12-myristate 13-acetate-stimulated Raw 264.7 macrophages resulted in the binding of μ1A of the clathrin-coated vesicle AP-1 complex. Furthermore, full-length GST-μ1A and the GST-μ1A C-terminal domain, but not the GST-μ1A N-terminal domain, bind to L-selectin tail peptide, and the intracellular pool of L-selectin colocalizes with AP-1 at the trans-Golgi network. We identified a novel basic protein motif consisting of a cluster of three dibasic residues (356RR357, 359KK360, and 362KK363) in the membrane-proximal domain of the L-selectin tail as well as a doublet of aspartic acid residues (369DD370) in the membrane-distal end of the L-selectin tail involved in μ1A binding. Stimulation of Raw 264.7 macrophages with PMA augmented the amount of μ1A associated with anti-L-selectin immunoprecipitates. However, full-length GST-μ1A did not bind to the phospho-L-selectin tail or phospho-mimetic S364D L-selectin tail. Accordingly, we propose that phosphorylation of μ1A is required for interaction with the L-selectin tail and that L-selectin tail phosphorylation may regulate this interaction in vivo Molecular docking of the L-selectin tail to μ1A was used to identify the μ1A surface domain binding the L-selectin tail and to explain how phosphorylation of the L-selectin tail abrogates μ1A interaction. Our findings indicate that L-selectin is transported constitutively by the AP-1 complex, leading to the formation of a trans-Golgi network reserve pool and that phosphorylation of the L-selectin tail blocks AP-1-dependent retrograde transport of L-selectin.
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Affiliation(s)
- Karim Dib
- From the Max Planck Institute for Biochemistry, Department of Molecular Medicine, 82152 Martinsried, Germany, .,the Center for Experimental Medicine, Queen's University Belfast, Belfast BT9 7BL, Northern Ireland, United Kingdom
| | - Irina G Tikhonova
- the School of Pharmacy, Queen's University Belfast, Belfast BT9 7BL, Northern Ireland, United Kingdom
| | - Aleksandar Ivetic
- the BHF Center for Research Excellence, Cardiovascular Division, Faculty of Life Sciences and Medicine, King's College London, London SE5 9NU, United Kingdom, and
| | - Peter Schu
- University Medical Center Göttingen, Department of Cellular Biochemistry, Georg-August University Göttingen, D-37073 Göttingen, Germany
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Krasavin M, Lukin A, Bagnyukova D, Zhurilo N, Golovanov A, Zozulya S, Zahanich I, Moore D, Tikhonova IG. Polar aromatic periphery increases agonist potency of spirocyclic free fatty acid receptor (GPR40) agonists inspired by LY2881835. Eur J Med Chem 2017; 127:357-368. [DOI: 10.1016/j.ejmech.2017.01.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2016] [Revised: 12/04/2016] [Accepted: 01/03/2017] [Indexed: 10/20/2022]
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Moore DS, Dalton JP, Tikhonova IG. Steered Molecular Dynamic Simulations Reveal Critical Residues for (Un)Binding of Substrates, Inhibitors and a Product of the Malarial PF M1AAP. Biophys J 2017. [DOI: 10.1016/j.bpj.2016.11.1920] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Cordomí A, Fourmy D, Tikhonova IG. Gut hormone GPCRs: structure, function, drug discovery. Curr Opin Pharmacol 2016; 31:63-67. [DOI: 10.1016/j.coph.2016.09.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Revised: 08/24/2016] [Accepted: 09/01/2016] [Indexed: 01/08/2023]
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Krasavin M, Lukin A, Bagnyukova D, Zhurilo N, Zahanich I, Zozulya S, Ihalainen J, Forsberg MM, Lehtonen M, Rautio J, Moore D, Tikhonova IG. Free fatty acid receptor 1 (GPR40) agonists containing spirocyclic periphery inspired by LY2881835. Bioorg Med Chem 2016; 24:5481-5494. [DOI: 10.1016/j.bmc.2016.09.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 08/21/2016] [Accepted: 09/01/2016] [Indexed: 11/26/2022]
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Smith D, Tikhonova IG, Jewhurst HL, Drysdale OC, Dvořák J, Robinson MW, Cwiklinski K, Dalton JP. Unexpected Activity of a Novel Kunitz-type Inhibitor: INHIBITION OF CYSTEINE PROTEASES BUT NOT SERINE PROTEASES. J Biol Chem 2016; 291:19220-34. [PMID: 27422822 PMCID: PMC5016662 DOI: 10.1074/jbc.m116.724344] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Indexed: 12/15/2022] Open
Abstract
Kunitz-type (KT) protease inhibitors are low molecular weight proteins classically defined as serine protease inhibitors. We identified a novel secreted KT inhibitor associated with the gut and parenchymal tissues of the infective juvenile stage of Fasciola hepatica, a helminth parasite of medical and veterinary importance. Unexpectedly, recombinant KT inhibitor (rFhKT1) exhibited no inhibitory activity toward serine proteases but was a potent inhibitor of the major secreted cathepsin L cysteine proteases of F. hepatica, FhCL1 and FhCL2, and of human cathepsins L and K (Ki = 0.4-27 nm). FhKT1 prevented the auto-catalytic activation of FhCL1 and FhCL2 and formed stable complexes with the mature enzymes. Pulldown experiments from adult parasite culture medium showed that rFhKT1 interacts specifically with native secreted FhCL1, FhCL2, and FhCL5. Substitution of the unusual P1 Leu15 within the exposed reactive loop of FhKT1 for the more commonly found Arg (FhKT1Leu15/Arg15) had modest adverse effects on the cysteine protease inhibition but conferred potent activity against the serine protease trypsin (Ki = 1.5 nm). Computational docking and sequence analysis provided hypotheses for the exclusive binding of FhKT1 to cysteine proteases, the importance of the Leu15 in anchoring the inhibitor into the S2 active site pocket, and the inhibitor's selectivity toward FhCL1, FhCL2, and human cathepsins L and K. FhKT1 represents a novel evolutionary adaptation of KT protease inhibitors by F. hepatica, with its prime purpose likely in the regulation of the major parasite-secreted proteases and/or cathepsin L-like proteases of its host.
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Affiliation(s)
| | - Irina G Tikhonova
- School of Pharmacy, Medical Biology Centre, Queen's University Belfast, Belfast BT9 7BL, Northern Ireland, United Kingdom
| | | | | | - Jan Dvořák
- From the School of Biological Sciences and
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28
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Grundmann M, Tikhonova IG, Hudson BD, Smith NJ, Mohr K, Ulven T, Milligan G, Kenakin T, Kostenis E. A Molecular Mechanism for Sequential Activation of a G Protein-Coupled Receptor. Cell Chem Biol 2016; 23:392-403. [PMID: 26991104 DOI: 10.1016/j.chembiol.2016.02.014] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Revised: 02/11/2016] [Accepted: 02/22/2016] [Indexed: 01/05/2023]
Abstract
Ligands targeting G protein-coupled receptors (GPCRs) are currently classified as either orthosteric, allosteric, or dualsteric/bitopic. Here, we introduce a new pharmacological concept for GPCR functional modulation: sequential receptor activation. A hallmark feature of this is a stepwise ligand binding mode with transient activation of a first receptor site followed by sustained activation of a second topographically distinct site. We identify 4-CMTB (2-(4-chlorophenyl)-3-methyl-N-(thiazol-2-yl)butanamide), previously classified as a pure allosteric agonist of the free fatty acid receptor 2, as the first sequential activator and corroborate its two-step activation in living cells by tracking integrated responses with innovative label-free biosensors that visualize multiple signaling inputs in real time. We validate this unique pharmacology with traditional cellular readouts, including mutational and pharmacological perturbations along with computational methods, and propose a kinetic model applicable to the analysis of sequential receptor activation. We envision this form of dynamic agonism as a common principle of nature to spatiotemporally encode cellular information.
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Affiliation(s)
- Manuel Grundmann
- Molecular-, Cellular- and Pharmacobiology Section, Institute for Pharmaceutical Biology, University of Bonn, 53115 Bonn, Germany.
| | - Irina G Tikhonova
- Molecular Therapeutics, School of Pharmacy, Medical Biology Centre, Queen's University, Belfast BT7 1NN Northern Ireland
| | - Brian D Hudson
- Molecular Pharmacology Group, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ Scotland
| | - Nicola J Smith
- Molecular Pharmacology Group, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ Scotland; Molecular Cardiology Division, Victor Chang Cardiac Research Institute, Faculty of Medicine, University of New South Wales, Darlinghurst, NSW 2010, Australia
| | - Klaus Mohr
- Pharmacology and Toxicology, University of Bonn, 53347 Bonn, Germany
| | - Trond Ulven
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, 5230 Odense M, Denmark
| | - Graeme Milligan
- Molecular Pharmacology Group, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ Scotland
| | - Terry Kenakin
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
| | - Evi Kostenis
- Molecular-, Cellular- and Pharmacobiology Section, Institute for Pharmaceutical Biology, University of Bonn, 53115 Bonn, Germany.
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Abstract
Five G protein-coupled receptors (GPCRs) have been identified to be activated by free fatty acids (FFA). Among them, FFA1 (GPR40) and FFA4 (GPR120) bind long-chain fatty acids, FFA2 (GPR43) and FFA3 (GPR41) bind short-chain fatty acids and GPR84 binds medium-chain fatty acids. Free fatty acid receptors have now emerged as potential targets for the treatment of diabetes, obesity and immune diseases. The recent progress in crystallography of GPCRs has now enabled the elucidation of the structure of FFA1 and provided reliable templates for homology modelling of other FFA receptors. Analysis of the crystal structure and improved homology models, along with mutagenesis data and structure activity, highlighted an unusual arginine charge-pairing interaction in FFA1-3 for receptor modulation, distinct structural features for ligand binding to FFA1 and FFA4 and an arginine of the second extracellular loop as a possible anchoring point for FFA at GPR84. Structural data will be helpful for searching novel small-molecule modulators at the FFA receptors.
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Affiliation(s)
- Irina G Tikhonova
- Molecular Therapeutics, School of Pharmacy, Medical Biology Centre, Queen's University Belfast, BT9 7BL, Northern Ireland, UK.
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Ismail S, Dubois-Vedrenne I, Laval M, Tikhonova IG, D'Angelo R, Sanchez C, Clerc P, Gherardi MJ, Gigoux V, Magnan R, Fourmy D. Internalization and desensitization of the human glucose-dependent-insulinotropic receptor is affected by N-terminal acetylation of the agonist. Mol Cell Endocrinol 2015. [PMID: 26225752 DOI: 10.1016/j.mce.2015.07.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
How incretins regulate presence of their receptors at the cell surface and their activity is of paramount importance for the development of therapeutic strategies targeting these receptors. We have studied internalization of the human Glucose-Insulinotropic Polypeptide receptor (GIPR). GIP stimulated rapid robust internalization of the GIPR, the major part being directed to lysosomes. GIPR internalization involved mainly clathrin-coated pits, AP-2 and dynamin. However, neither GIPR C-terminal region nor β-arrestin1/2 was required. Finally, N-acetyl-GIP recognized as a dipeptidyl-IV resistant analogue, fully stimulated cAMP production with a ∼15-fold lower potency than GIP and weakly stimulated GIPR internalization and desensitization of cAMP response. Furthermore, docking N-acetyl-GIP in the binding site of modeled GIPR showed slighter interactions with residues of helices 6 and 7 of GIPR compared to GIP. Therefore, incomplete or partial activity of N-acetyl-GIP on signaling involved in GIPR desensitization and internalization contributes to the enhanced incretin activity of this peptide.
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Affiliation(s)
- Sadek Ismail
- Université de Toulouse 3, EA 4552, Inserm U1048/I2MC, Toulouse, France
| | | | - Marie Laval
- Université de Toulouse 3, EA 4552, Inserm U1048/I2MC, Toulouse, France
| | - Irina G Tikhonova
- Molecular Therapeutics, School of Pharmacy, Queen's University of Belfast, North Ireland, UK
| | - Romina D'Angelo
- Cellular Imaging Facility Rangueil, Inserm U1048/I2MC, Toulouse, France
| | - Claire Sanchez
- Université de Toulouse 3, EA 4552, Inserm U1048/I2MC, Toulouse, France
| | - Pascal Clerc
- Université de Toulouse 3, EA 4552, Inserm U1048/I2MC, Toulouse, France
| | | | - Véronique Gigoux
- Université de Toulouse 3, EA 4552, Inserm U1048/I2MC, Toulouse, France
| | - Remi Magnan
- Université de Toulouse 3, EA 4552, Inserm U1048/I2MC, Toulouse, France
| | - Daniel Fourmy
- Université de Toulouse 3, EA 4552, Inserm U1048/I2MC, Toulouse, France.
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Tikhonova IG, Poerio E. Free fatty acid receptors: structural models and elucidation of ligand binding interactions. BMC Struct Biol 2015; 15:16. [PMID: 26346819 PMCID: PMC4561419 DOI: 10.1186/s12900-015-0044-2] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 08/26/2015] [Indexed: 12/14/2022]
Abstract
Background The free fatty acid receptors (FFAs), including FFA1 (orphan name: GPR40), FFA2 (GPR43) and FFA3 (GPR41) are G protein-coupled receptors (GPCRs) involved in energy and metabolic homeostasis. Understanding the structural basis of ligand binding at FFAs is an essential step toward designing potent and selective small molecule modulators. Results We analyse earlier homology models of FFAs in light of the newly published FFA1 crystal structure co-crystallized with TAK-875, an ago-allosteric ligand, focusing on the architecture of the extracellular binding cavity and agonist-receptor interactions. The previous low-resolution homology models of FFAs were helpful in highlighting the location of the ligand binding site and the key residues for ligand anchoring. However, homology models were not accurate in establishing the nature of all ligand-receptor contacts and the precise ligand-binding mode. From analysis of structural models and mutagenesis, it appears that the position of helices 3, 4 and 5 is crucial in ligand docking. The FFA1-based homology models of FFA2 and FFA3 were constructed and used to compare the FFA subtypes. From docking studies we propose an alternative binding mode for orthosteric agonists at FFA1 and FFA2, involving the interhelical space between helices 4 and 5. This binding mode can explain mutagenesis results for residues at positions 4.56 and 5.42. The novel FFAs structural models highlight higher aromaticity of the FFA2 binding cavity and higher hydrophilicity of the FFA3 binding cavity. The role of the residues at the second extracellular loop used in mutagenesis is reanalysed. The third positively-charged residue in the binding cavity of FFAs, located in helix 2, is identified and predicted to coordinate allosteric modulators. Conclusions The novel structural models of FFAs provide information on specific modes of ligand binding at FFA subtypes and new suggestions for mutagenesis and ligand modification, guiding the development of novel orthosteric and allosteric chemical probes to validate the importance of FFAs in metabolic and inflammatory conditions. Using our FFA homology modelling experience, a strategy to model a GPCR, which is phylogenetically distant from GPCRs with the available crystal structures, is discussed. Electronic supplementary material The online version of this article (doi:10.1186/s12900-015-0044-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Irina G Tikhonova
- Molecular Therapeutics, School of Pharmacy, Medical Biology Centre, Queen's University Belfast, Belfast, BT9 7BL, Northern Ireland, UK.
| | - Elena Poerio
- Molecular Therapeutics, School of Pharmacy, Medical Biology Centre, Queen's University Belfast, Belfast, BT9 7BL, Northern Ireland, UK.
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Elsawy MA, Tikhonova IG, Martin SL, Walker B. Smac-derived Aza-peptide As an Aminopeptidase-resistant XIAP BIR3 Antagonist. Protein Pept Lett 2015:PPL-EPUB-68218. [PMID: 26095377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2014] [Revised: 06/12/2015] [Accepted: 05/29/2015] [Indexed: 06/04/2023]
Abstract
The peptidic nature of anti-IAPs N-terminus Smac-derived peptides precludes their utilization as potential therapeutic anticancer agents. Recent advances in the development of novel Smac-derived peptidomimetics and non-peptidic molecules with improved anti-IAPs activity and resistance to proteolytic cleavage have been reported and led to a number of candidates that are currently in clinical trials including LCL-161, SM-406/AT-406, GDC-0512/GDC-0917, and birinapant. As an attempt to improve the proteolytic stability of Smac peptides, we developed the Aza-peptide AzaAla-Val-Pro-Phe-Tyr-NH2 (2). Unlike unmodified peptide Ala-Val-Pro-Phe-Tyr-NH2 (1), analogue (2) exhibited resistance towards proteolytic cleavage by two aminopeptidases; LAP and DPP-IV, while retaining its IAP inhibitory activity. This was due to the altered planar geometry of the P1 residue side chain. Our findings showed that using aza-isosteres of bioactive peptide sequences imbue the residue with imperviousness to proteolysis; underscoring a potential approach for developing a new generation of Smac-derived Aza-peptidomimetics.
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Affiliation(s)
- Mohamed A Elsawy
- Manchester Institute of Biotechnology, University of Manchester, 131 Princess Street, Manchester M1 7DN, UK.
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33
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Elsawy MA, Tikhonova IG, Martin L, Walker B. Smac-Derived Aza-Peptide As an Aminopeptidase-Resistant XIAP BIR3 Antagonist. Protein Pept Lett 2015; 22:836-843. [PMID: 26282728] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2014] [Revised: 06/12/2015] [Accepted: 05/29/2015] [Indexed: 06/04/2023]
Abstract
The peptidic nature of anti-IAPs N-terminus Smac-derived peptides precludes their utilization as potential therapeutic anticancer agents. Recent advances in the development of novel Smacderived peptidomimetics and non-peptidic molecules with improved anti-IAPs activity and resistance to proteolytic cleavage have been reported and led to a number of candidates that are currently in clinical trials including LCL-161, SM-406/AT-406, GDC-0512/GDC-0917, and birinapant. As an attempt to improve the proteolytic stability of Smac peptides, we developed the Aza-peptide AzaAla- Val-Pro-Phe-Tyr-NH2 (2). Unlike unmodified peptide Ala-Val-Pro-Phe-Tyr-NH2 (1), analogue (2) exhibited resistance towards proteolytic cleavage by two aminopeptidases; LAP and DPP-IV, while retaining its IAP inhibitory activity. This was due to the altered planar geometry of the P1 residue side chain. Our findings showed that using aza-isosteres of bioactive peptide sequences imbue the residue with imperviousness to proteolysis; underscoring a potential approach for developing a new generation of Smac-derived Aza-peptidomimetics.
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Affiliation(s)
- Mohamed A Elsawy
- Manchester Institute of Biotechnology, University of Manchester, 131 Princess Street, Manchester M1 7DN, UK.
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De Majumdar S, Yu J, Spencer J, Tikhonova IG, Schneiders T. Molecular basis of non-mutational derepression of ramA in Klebsiella pneumoniae. J Antimicrob Chemother 2014; 69:2681-9. [PMID: 25140579 DOI: 10.1093/jac/dku203] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
OBJECTIVES The ram locus, consisting of the romA-ramA genes, is repressed by the tetracycline-type regulator RamR, where regulation is abolished due to loss-of-function mutations within the protein or ligand interactions. The aim of this study was to determine whether the phenothiazines (chlorpromazine and thioridazine) directly interact with RamR to derepress ramA expression. METHODS Quantitative real-time PCR analyses were performed to determine expression levels of the romA-ramA genes after exposure to the phenothiazines. Electrophoretic mobility shift assays (EMSAs) and in vitro transcription experiments were performed to show direct binding to and repression by RamR. Direct binding of the RamR protein to the phenothiazines was measured by fluorescence spectroscopy experiments and molecular docking models were generated using the RamR crystal structure. RESULTS Exposure to either chlorpromazine or thioridazine resulted in the up-regulation of the romA-ramA genes. EMSAs and in vitro transcription experiments demonstrated that both agents reduce/abolish binding and enhance transcription of the target PI promoter upstream of the ramR-romA genes in Klebsiella pneumoniae compared with RamR alone. Fluorescence spectroscopy measurements demonstrated that RamR directly binds both chlorpromazine and thioridazine with micromolar affinity. Molecular docking analyses using the RamR crystal structure demonstrated that the phenothiazines interact with RamR protein through contacts described for other ligands, in addition to forming unique strong polar interactions at positions D152 and K63. CONCLUSIONS These data demonstrate that phenothiazines can modulate loci linked to the microbe-drug response where RamR is an intracellular target for the phenothiazines, thus resulting in a transient non-mutational derepression of ramA concentrations.
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Affiliation(s)
- Shyamasree De Majumdar
- Centre for Infection and Immunity, Health Sciences Building, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7AE, UK
| | - Jing Yu
- Centre for Infection and Immunity, Health Sciences Building, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7AE, UK
| | - James Spencer
- School of Cellular and Molecular Medicine, Medical Sciences Building, University of Bristol, University Walk, Bristol BS18 1TD, UK
| | - Irina G Tikhonova
- Molecular Therapeutics, School of Pharmacy, Medical Biology Centre, Queen's University Belfast, Belfast BT9 7BL, Northern Ireland, UK
| | - Thamarai Schneiders
- Centre for Infection and Immunity, Health Sciences Building, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7AE, UK
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Elsawy MA, Martin L, Tikhonova IG, Walker B. Solid phase synthesis of Smac/DIABLO-derived peptides using a ‘Safety-Catch’ resin: Identification of potent XIAP BIR3 antagonists. Bioorg Med Chem 2013; 21:5004-11. [DOI: 10.1016/j.bmc.2013.06.055] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2012] [Revised: 06/20/2013] [Accepted: 06/24/2013] [Indexed: 10/26/2022]
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Tikhonova IG, Selvam B, Ivetac A, Wereszczynski J, McCammon JA. Simulations of biased agonists in the β(2) adrenergic receptor with accelerated molecular dynamics. Biochemistry 2013; 52:5593-603. [PMID: 23879802 PMCID: PMC3763781 DOI: 10.1021/bi400499n] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The biased agonism of the G protein-coupled receptors (GPCRs), where in addition to a traditional G protein-signaling pathway a GPCR promotes intracellular signals though β-arrestin, is a novel paradigm in pharmacology. Biochemical and biophysical studies have suggested that a GPCR forms a distinct ensemble of conformations signaling through the G protein and β-arrestin. Here we report on the dynamics of the β2 adrenergic receptor bound to the β-arrestin and G protein-biased agonists and the empty receptor to further characterize the receptor conformational changes caused by biased agonists. We use conventional and accelerated molecular dynamics (aMD) simulations to explore the conformational transitions of the GPCR from the active state to the inactive state. We found that aMD simulations enable monitoring of the transition within the nanosecond time scale while capturing the known microscopic characteristics of the inactive states, such as the ionic lock, the inward position of F6.44, and water clusters. Distinct conformational states are shown to be stabilized by each biased agonist. In particular, in simulations of the receptor with the β-arrestin-biased agonist N-cyclopentylbutanepherine, we observe a different pattern of motions in helix 7 when compared to simulations with the G protein-biased agonist salbutamol that involves perturbations of the network of interactions within the NPxxY motif. Understanding the network of interactions induced by biased ligands and the subsequent receptor conformational shifts will lead to development of more efficient drugs.
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Affiliation(s)
- Irina G Tikhonova
- Molecular Therapeutics, School of Pharmacy, Medical Biology Centre, Queen's University, Belfast BT9 7BL, Northern Ireland, UK.
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Selvam B, Porter SL, Tikhonova IG. Addressing Selective Polypharmacology of Antipsychotic Drugs Targeting the Bioaminergic Receptors through Receptor Dynamic Conformational Ensembles. J Chem Inf Model 2013; 53:1761-74. [DOI: 10.1021/ci400282q] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Balaji Selvam
- Molecular Therapeutics,
School of Pharmacy, Medical
Biology Centre, 97 Lisburn Road, Queen’s University Belfast, BT9 7BL, Northern Ireland, United Kingdom
| | - Simon L. Porter
- Molecular Therapeutics,
School of Pharmacy, Medical
Biology Centre, 97 Lisburn Road, Queen’s University Belfast, BT9 7BL, Northern Ireland, United Kingdom
| | - Irina G. Tikhonova
- Molecular Therapeutics,
School of Pharmacy, Medical
Biology Centre, 97 Lisburn Road, Queen’s University Belfast, BT9 7BL, Northern Ireland, United Kingdom
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38
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Hudson BD, Due-Hansen ME, Christiansen E, Hansen AM, Mackenzie AE, Murdoch H, Pandey SK, Ward RJ, Marquez R, Tikhonova IG, Ulven T, Milligan G. Defining the molecular basis for the first potent and selective orthosteric agonists of the FFA2 free fatty acid receptor. J Biol Chem 2013; 288:17296-312. [PMID: 23589301 PMCID: PMC3682533 DOI: 10.1074/jbc.m113.455337] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
FFA2 is a G protein-coupled receptor that responds to short chain fatty acids and has generated interest as a therapeutic target for metabolic and inflammatory conditions. However, definition of its functions has been slowed by a dearth of selective ligands that can distinguish it from the closely related FFA3. At present, the only selective ligands described for FFA2 suffer from poor potency, altered signaling due to allosteric modes of action, or a lack of function at non-human orthologs of the receptor. To address the need for novel selective ligands, we synthesized two compounds potentially having FFA2 activity and examined the molecular basis of their function. These compounds were confirmed to be potent and selective orthosteric FFA2 agonists. A combination of ligand structure-activity relationship, pharmacological analysis, homology modeling, species ortholog comparisons, and mutagenesis studies were then employed to define the molecular basis of selectivity and function of these ligands. From this, we identified key residues within both extracellular loop 2 and the transmembrane domain regions of FFA2 critical for ligand function. One of these ligands was active with reasonable potency at rodent orthologs of FFA2 and demonstrated the role of FFA2 in inhibition of lipolysis and glucagon-like peptide-1 secretion in murine-derived 3T3-L1 and STC-1 cell lines, respectively. Together, these findings describe the first potent and selective FFA2 orthosteric agonists and demonstrate key aspects of ligand interaction within the binding site of FFA2 that will be invaluable in future ligand development at this receptor.
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Affiliation(s)
- Brian D Hudson
- Molecular Pharmacology Group, Institute of Molecular, Cell, and Systems Biology, College of Medical, Veterinary, and Life Sciences, Wolfson Link Building 253, University of Glasgow, Glasgow G12 8QQ, United Kingdom
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Magnan R, Escrieut C, Gigoux V, De K, Clerc P, Niu F, Azema J, Masri B, Cordomi A, Baltas M, Tikhonova IG, Fourmy D. Distinct CCK-2 receptor conformations associated with β-arrestin-2 recruitment or phospholipase-C activation revealed by a biased antagonist. J Am Chem Soc 2013; 135:2560-73. [PMID: 23323542 DOI: 10.1021/ja308784w] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Seven-transmembrane receptors (7TMRs), also termed G protein-coupled receptors (GPCRs), form the largest class of cell surface membrane receptors, involving several hundred members in the human genome. Nearly 30% of marketed pharmacological agents target 7TMRs. 7TMRs adopt multiple conformations upon agonist binding. Biased agonists, in contrast to non-biased agonists, are believed to stabilize conformations preferentially activating either G-protein- or β-arrestin-dependent signaling pathways. However, proof that cognate conformations of receptors display structural differences within their binding site where biased agonism initiates, are still lacking. Here, we show that a non-biased agonist, cholecystokinin (CCK) induces conformational states of the CCK2R activating Gq-protein-dependent pathway (CCK2R(G)) or recruiting β-arrestin2 (CCK2R(β)) that are pharmacologically and structurally distinct. Two structurally unrelated antagonists competitively inhibited both pathways. A third ligand (GV150013X) acted as a high affinity competitive antagonist on CCK2R(G) but was nearly inefficient as inhibitor of CCK2R(β). Several structural elements on both GV150013X and in CCK2R binding cavity, which hinder binding of GV150013X only to the CCK2R(β) were identified. At last, proximity between two conserved amino acids from transmembrane helices 3 and 7 interacting through sulfur-aromatic interaction was shown to be crucial for selective stabilization of the CCK2R(β) state. These data establish structural evidence for distinct conformations of a 7TMR associated with β-arrestin-2 recruitment or G-protein coupling and validate relevance of the design of biased ligands able to selectively target each functional conformation of 7TMRs.
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Affiliation(s)
- Rémi Magnan
- EA 4552, Université de Toulouse 3, 31432 Toulouse, France
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Andrews WJ, Panova T, Normand C, Gadal O, Tikhonova IG, Panov KI. Old drug, new target: ellipticines selectively inhibit RNA polymerase I transcription. J Biol Chem 2013; 288:4567-82. [PMID: 23293027 DOI: 10.1074/jbc.m112.411611] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Transcription by RNA polymerase I (Pol-I) is the main driving force behind ribosome biogenesis, a fundamental cellular process that requires the coordinated transcription of all three nuclear polymerases. Increased Pol-I transcription and the concurrent increase in ribosome biogenesis has been linked to the high rates of proliferation in cancers. The ellipticine family contains a number of potent anticancer therapeutic agents, some having progressed to stage I and II clinical trials; however, the mechanism by which many of the compounds work remains unclear. It has long been thought that inhibition of Top2 is the main reason behind the drugs antiproliferative effects. Here we report that a number of the ellipticines, including 9-hydroxyellipticine, are potent and specific inhibitors of Pol-I transcription, with IC(50) in vitro and in cells in the nanomolar range. Essentially, the drugs did not affect Pol-II and Pol-III transcription, demonstrating a high selectivity. We have shown that Pol-I inhibition occurs by a p53-, ATM/ATR-, and Top2-independent mechanism. We discovered that the drug influences the assembly and stability of preinitiation complexes by targeting the interaction between promoter recognition factor SL1 and the rRNA promoter. Our findings will have an impact on the design and development of novel therapeutic agents specifically targeting ribosome biogenesis.
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Affiliation(s)
- William J Andrews
- School of Biological Sciences, The Queen’s University Belfast, Belfast BT9 7BL, United Kingdom
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Hudson BD, Tikhonova IG, Pandey SK, Ulven T, Milligan G. Extracellular ionic locks determine variation in constitutive activity and ligand potency between species orthologs of the free fatty acid receptors FFA2 and FFA3. J Biol Chem 2012; 287:41195-209. [PMID: 23066016 PMCID: PMC3510819 DOI: 10.1074/jbc.m112.396259] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Free fatty acid receptors 2 and 3 (FFA2 and FFA3) are G protein-coupled receptors for short chain free fatty acids (SCFAs). They respond to the same set of endogenous ligands but with distinct rank-order of potency such that acetate (C2) has been described as FFA2-selective, whereas propionate (C3) is non-selective. Although C2 was confirmed to be selective for human FFA2 over FFA3, this ligand was not selective between the mouse orthologs. Moreover, although C3 was indeed not selective between the human orthologs, it displayed clear selectivity for mouse FFA3 over mouse FFA2. This altered selectivity to C2 and C3 resulted from broad differences in SCFAs potency at the mouse orthologs. In studies to define the molecular basis for these observations, marked variation in ligand-independent constitutive activity was identified using a [35S]GTPγS assay. The orthologs with higher potency for the SCFAs, human FFA2 and mouse FFA3, displayed high constitutive activity in this assay, whereas the orthologs with lower potency for the agonist ligands, mouse FFA2 and human FFA3, did not. Sequence alignments of the second extracellular loop identified single negatively charged residues in FFA2 and FFA3 not conserved between species and predicted to form ionic lock interactions with arginine residues within the FFA2 or FFA3 agonist binding pocket to regulate constitutive activity and SCFA potency. Reciprocal mutation of these residues between species orthologs resulted in the induction (or repression) of constitutive activity and in most cases also yielded corresponding changes in SCFA potency.
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Affiliation(s)
- Brian D Hudson
- Molecular Pharmacology Group, Institute of Molecular, Cell, and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom
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42
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Kowalski-Chauvel A, Najib S, Tikhonova IG, Huc L, Lopez F, Martinez LO, Cohen-Jonathan-Moyal E, Ferrand A, Seva C. Identification of the F1-ATPase at the cell surface of colonic epithelial cells: role in mediating cell proliferation. J Biol Chem 2012; 287:41458-68. [PMID: 23055519 DOI: 10.1074/jbc.m112.382465] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
F1 domain of F(1)F(o)-ATPase was initially believed to be strictly expressed in the mitochondrial membrane. Interestingly, recent reports have shown that the F1 complex can serve as a cell surface receptor for apparently unrelated ligands. Here we show for the first time the presence of the F(1)-ATPase at the cell surface of normal or cancerous colonic epithelial cells. Using surface plasmon resonance technology and mass spectrometry, we identified a peptide hormone product of the gastrin gene (glycine-extended gastrin (G-gly)) as a new ligand for the F(1)-ATPase. By molecular modeling, we identified the motif in the peptide sequence (E(E/D)XY), that directly interacts with the F(1)-ATPase and the amino acids in the F(1)-ATPase that bind this motif. Replacement of the Glu-9 residue by an alanine in the E(E/D)XY motif resulted in a strong decrease of G-gly binding to the F(1)-ATPase and the loss of its biological activity. In addition we demonstrated that F(1)-ATPase mediates the growth effects of the peptide. Indeed, blocking F(1)-ATPase activity decreases G-gly-induced cell growth. The mechanism likely involves ADP production by the membrane F(1)-ATPase, which is induced by G-gly. These results suggest an important contribution of cell surface F(1)-ATPase in the pro-proliferative action of this gastrointestinal peptide.
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Affiliation(s)
- Aline Kowalski-Chauvel
- INSERM UMR 1037, Cancer Research Centre of Toulouse, Université Paul Sabatier Toulouse III, 31052 Toulouse, France
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43
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Hudson BD, Christiansen E, Tikhonova IG, Grundmann M, Kostenis E, Adams DR, Ulven T, Milligan G. Chemically engineering ligand selectivity at the free fatty acid receptor 2 based on pharmacological variation between species orthologs. FASEB J 2012; 26:4951-65. [PMID: 22919070 PMCID: PMC3509056 DOI: 10.1096/fj.12-213314] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
When it is difficult to develop selective ligands within a family of related G-protein-coupled receptors (GPCRs), chemically engineered receptors activated solely by synthetic ligands (RASSLs) are useful alternatives for probing receptor function. In the present work, we explored whether a RASSL of the free fatty acid receptor 2 (FFA2) could be developed on the basis of pharmacological variation between species orthologs. For this, bovine FFA2 was characterized, revealing distinct ligand selectivity compared with human FFA2. Homology modeling and mutational analysis demonstrated a single mutation in human FFA2 of C4.57G resulted in a human FFA2 receptor with ligand selectivity similar to the bovine receptor. This was exploited to generate human FFA2-RASSL by the addition of a second mutation at a known orthosteric ligand interaction site, H6.55Q. The resulting FFA2-RASSL displayed a >100-fold loss of activity to endogenous ligands, while responding to the distinct ligand sorbic acid with pEC50 values for inhibition of cAMP, 5.83 ± 0.11; Ca2+ mobilization, 4.63 ± 0.05; ERK phosphorylation, 5.61 ± 0.06; and dynamic mass redistribution, 5.35 ± 0.06. This FFA2-RASSL will be useful in future studies on this receptor and demonstrates that exploitation of pharmacological variation between species orthologs is a powerful method to generate novel chemically engineered GPCRs.—Hudson, B. D., Christiansen, E., Tikhonova, I. G., Grundmann, M., Kostenis, E., Adams, D. R., Ulven, T., Milligan, G. Chemically engineering ligand selectivity at the free fatty acid receptor 2 based on pharmacological variation between species orthologs.
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Affiliation(s)
- Brian D Hudson
- Molecular Pharmacology Group, Institute of Molecular, Cell, and Systems Biology, College of Medical, Veterinary, and Life Sciences, University of Glasgow, Glasgow, UK
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Selvam B, Wereszczynski J, Tikhonova IG. Comparison of dynamics of extracellular accesses to the β(1) and β(2) adrenoceptors binding sites uncovers the potential of kinetic basis of antagonist selectivity. Chem Biol Drug Des 2012; 80:215-26. [PMID: 22530954 DOI: 10.1111/j.1747-0285.2012.01390.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
From the molecular mechanism of antagonist unbinding in the β(1) and β(2) adrenoceptors investigated by steered molecular dynamics, we attempt to provide further possibilities of ligand subtype and subspecies selectivity. We have simulated unbinding of β(1)-selective Esmolol and β(2)-selective ICI-118551 from both receptors to the extracellular environment and found distinct molecular features of unbinding. By calculating work profiles, we show different preference in antagonist unbinding pathways between the receptors, in particular, perpendicular to the membrane pathway is favourable in the β(1) adrenoceptor, whereas the lateral pathway involving helices 5, 6 and 7 is preferable in the β(2) adrenoceptor. The estimated free energy change of unbinding based on the preferable pathway correlates with the experimental ligand selectivity. We then show that the non-conserved K347 (6.58) appears to facilitate in guiding Esmolol to the extracellular surface via hydrogen bonds in the β(1) adrenoceptor. In contrast, hydrophobic and aromatic interactions dominate in driving ICI-118551 through the easiest pathway in the β(2) adrenoceptor. We show how our study can stimulate design of selective antagonists and discuss other possible molecular reasons of ligand selectivity, involving sequential binding of agonists and glycosylation of the receptor extracellular surface.
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Affiliation(s)
- Balaji Selvam
- Molecular Therapeutics, School of Pharmacy, Medical Biology Centre, Queen's University Belfast, Belfast BT9 7BL, UK
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Smith NJ, Ward RJ, Stoddart LA, Hudson BD, Kostenis E, Ulven T, Morris JC, Tränkle C, Tikhonova IG, Adams DR, Milligan G. Extracellular loop 2 of the free fatty acid receptor 2 mediates allosterism of a phenylacetamide ago-allosteric modulator. Mol Pharmacol 2011; 80:163-73. [PMID: 21498659 DOI: 10.1124/mol.110.070789] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Allosteric agonists are powerful tools for exploring the pharmacology of closely related G protein-coupled receptors that have nonselective endogenous ligands, such as the short chain fatty acids at free fatty acid receptors 2 and 3 (FFA2/GPR43 and FFA3/GPR41, respectively). We explored the molecular mechanisms mediating the activity of 4-chloro-α-(1-methylethyl)-N-2-thiazolylbenzeneacetamide (4-CMTB), a recently described phenylacetamide allosteric agonist and allosteric modulator of endogenous ligand function at human FFA2, by combining our previous knowledge of the orthosteric binding site with targeted examination of 4-CMTB structure-activity relationships and mutagenesis and chimeric receptor generation. Here we show that 4-CMTB is a selective agonist for FFA2 that binds to a site distinct from the orthosteric site of the receptor. Ligand structure-activity relationship studies indicated that the N-thiazolyl amide is likely to provide hydrogen bond donor/acceptor interactions with the receptor. Substitution at Leu(173) or the exchange of the entire extracellular loop 2 of FFA2 with that of FFA3 was sufficient to reduce or ablate, respectively, allosteric communication between the endogenous and allosteric agonists. Thus, we conclude that extracellular loop 2 of human FFA2 is required for transduction of cooperative signaling between the orthosteric and an as-yet-undefined allosteric binding site of the FFA2 receptor that is occupied by 4-CMTB.
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Affiliation(s)
- Nicola J Smith
- Molecular Pharmacology Group, Institute of Neuroscience and Psychology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, Scotland, United Kingdom
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Tikhonova IG, Smith NJ, Ward RJ, Stoddart LA, Hudson BD, Kostenis E, Ulven T, Morris JC, Adams D, Milligan G. Probing Allosteric Binding Site Mapping in the Free Fatty Acid 2 receptor. Biophys J 2011. [DOI: 10.1016/j.bpj.2010.12.483] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Schmidt J, Smith NJ, Christiansen E, Tikhonova IG, Grundmann M, Hudson BD, Ward RJ, Drewke C, Milligan G, Kostenis E, Ulven T. Selective orthosteric free fatty acid receptor 2 (FFA2) agonists: identification of the structural and chemical requirements for selective activation of FFA2 versus FFA3. J Biol Chem 2011; 286:10628-40. [PMID: 21220428 PMCID: PMC3060514 DOI: 10.1074/jbc.m110.210872] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Free fatty acid receptor 2 (FFA2; GPR43) is a G protein-coupled seven-transmembrane receptor for short-chain fatty acids (SCFAs) that is implicated in inflammatory and metabolic disorders. The SCFA propionate has close to optimal ligand efficiency for FFA2 and can hence be considered as highly potent given its size. Propionate, however, does not discriminate between FFA2 and the closely related receptor FFA3 (GPR41). To identify FFA2-selective ligands and understand the molecular basis for FFA2 selectivity, a targeted library of small carboxylic acids was examined using holistic, label-free dynamic mass redistribution technology for primary screening and the receptor-proximal G protein [35S]guanosine 5′-(3-O-thio)triphosphate activation, inositol phosphate, and cAMP accumulation assays for hit confirmation. Structure-activity relationship analysis allowed formulation of a general rule to predict selectivity for small carboxylic acids at the orthosteric binding site where ligands with substituted sp3-hybridized α-carbons preferentially activate FFA3, whereas ligands with sp2- or sp-hybridized α-carbons prefer FFA2. The orthosteric binding mode was verified by site-directed mutagenesis: replacement of orthosteric site arginine residues by alanine in FFA2 prevented ligand binding, and molecular modeling predicted the detailed mode of binding. Based on this, selective mutation of three residues to their non-conserved counterparts in FFA3 was sufficient to transfer FFA3 selectivity to FFA2. Thus, selective activation of FFA2 via the orthosteric site is achievable with rather small ligands, a finding with significant implications for the rational design of therapeutic compounds selectively targeting the SCFA receptors.
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Affiliation(s)
- Johannes Schmidt
- Molecular, Cellular, and Pharmacobiology Section, Institute of Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany
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Chen X, Tikhonova IG, Decker M. Probing the mid-gorge of cholinesterases with spacer-modified bivalent quinazolinimines leads to highly potent and selective butyrylcholinesterase inhibitors. Bioorg Med Chem 2010; 19:1222-35. [PMID: 21232964 DOI: 10.1016/j.bmc.2010.12.034] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2010] [Revised: 12/13/2010] [Accepted: 12/14/2010] [Indexed: 10/18/2022]
Abstract
The spacer structure of homobivalent quinazolinimes acting as potent acetyl-(AChE)- and butyrylcholinesterase (BChE) inhibitors was chemically modified introducing tertiary amine and acyl-amide moieties, and the activities at both ChEs were evaluated. Molecular docking was applied to explain the data and probe the capacity of the mid-gorge site of both ChEs. The novel spacer structures considerably alter the biological profile of bivalent quinazolinimines with regard to both inhibitory activity and selectivity. Mutual interaction of binding to the various sites of the enzymes was further investigated by applying also different spacer lengths and ring sizes of the alicycle of the tricyclic quinazolinimines. In order to achieve selectivity toward BChE and to improve inhibitory activities, the spacer structure was optimized and identified a highly potent and selective BChE inhibitor.
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Affiliation(s)
- Xinyu Chen
- School of Pharmacy, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, UK
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Abstract
G protein-coupled receptors (GPCRs) are a large superfamily of signaling proteins expressed on the plasma membrane. They are involved in a wide range of physiological processes and, therefore, are exploited as drug targets in a multitude of therapeutic areas. In this extent, knowledge of structural and functional properties of GPCRs may greatly facilitate rational design of modulator compounds. Solution and solid-state nuclear magnetic resonance (NMR) spectroscopy represents a powerful method to gather atomistic insights into protein structure and dynamics. In spite of the difficulties inherent the solution of the structure of membrane proteins through NMR, these methods have been successfully applied, sometimes in combination with molecular modeling, to the determination of the structure of GPCR fragments, the mapping of receptor-ligand interactions, and the study of the conformational changes associated with the activation of the receptors. In this review, we provide a summary of the NMR contributions to the study of the structure and function of GPCRs, also in light of the published crystal structures.
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Affiliation(s)
- Irina G Tikhonova
- Laboratory of Biological Modeling, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, DHHS, Bethesda, MD 20892, USA
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Yaqub T, Tikhonova IG, Lättig J, Magnan R, Laval M, Escrieut C, Boulègue C, Hewage C, Fourmy D. Identification of determinants of glucose-dependent insulinotropic polypeptide receptor that interact with N-terminal biologically active region of the natural ligand. Mol Pharmacol 2010; 77:547-58. [PMID: 20061446 DOI: 10.1124/mol.109.060111] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Glucose-dependent insulinotropic polypeptide receptor (GIPR), a member of family B of the G-protein coupled receptors, is a potential therapeutic target for which discovery of nonpeptide ligands is highly desirable. Structure-activity relationship studies indicated that the N-terminal part of glucose-dependent insulinotropic polypeptide (GIP) is crucial for biological activity. Here, we aimed at identification of residues in the GIPR involved in functional interaction with N-terminal moiety of GIP. A homology model of the transmembrane core of GIPR was constructed, whereas a three-dimensional model of the complex formed between GIP and the N-terminal extracellular domain of GIPR was taken from the crystal structure. The latter complex was docked to the transmembrane domains of GIPR, allowing in silico identification of putative residues of the agonist binding/activation site. All mutants were expressed at the surface of human embryonic kidney 293 cells as indicated by flow cytometry and confocal microscopy analysis of fluorescent GIP binding. Mutation of residues Arg183, Arg190, Arg300, and Phe357 caused shifts of 76-, 71-, 42-, and 16-fold in the potency to induce cAMP formation, respectively. Further characterization of these mutants, including tests with alanine-substituted GIP analogs, were in agreement with interaction of Glu3 in GIP with Arg183 in GIPR. Furthermore, they strongly supported a binding mode of GIP to GIPR in which the N-terminal moiety of GIP was sited within transmembrane helices (TMH) 2, 3, 5, and 6 with biologically crucial Tyr1 interacting with Gln224 (TMH3), Arg300 (TMH5), and Phe357 (TMH6). These data represent an important step toward understanding activation of GIPR by GIP, which should facilitate the rational design of therapeutic agents.
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Affiliation(s)
- Tahir Yaqub
- Institut National de la Santé et de la Recherche Médicale, U858, Université Paul Sabatier (Toulouse III), Toulouse Cedex 4, France
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