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Lešnik S, Bren U, Domratcheva T, Bondar AN. Fentanyl and the Fluorinated Fentanyl Derivative NFEPP Elicit Distinct Hydrogen-Bond Dynamics of the Opioid Receptor. J Chem Inf Model 2023; 63:4732-4748. [PMID: 37498626 DOI: 10.1021/acs.jcim.3c00197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/28/2023]
Abstract
The development of safe therapeutics to manage pain is of central interest for biomedical applications. The fluorinated fentanyl derivative N-(3-fluoro-1-phenethylpiperidin-4-yl)-N-phenylpropionamide (NFEPP) is potentially a safer alternative to fentanyl because unlike fentanyl─which binds to the μ-opioid receptor (MOR) at both physiological and acidic pH─NFEPP might bind to the MOR only at acidic pH typical of inflamed tissue. Knowledge of the protonation-coupled dynamics of the receptor-drug interactions is thus required to understand the molecular mechanism by which receptor activation initiates cell signaling to silence pain. To this end, here we have carried out extensive atomistic simulations of the MOR in different protonation states, in the absence of opioid drugs, and in the presence of fentanyl vs NFEPP. We used graph-based analyses to characterize internal hydrogen-bond networks that could contribute to the activation of the MOR. We find that fentanyl and NFEPP prefer distinct binding poses and that, in their binding poses, fentanyl and NFEPP partake in distinct internal hydrogen-bond networks, leading to the cytoplasmic G-protein-binding region. Moreover, the protonation state of functionally important aspartic and histidine side chains impacts hydrogen-bond networks that extend throughout the receptor, such that the ligand-bound MOR presents at its cytoplasmic G-protein-binding side, a hydrogen-bonding environment where dynamics depend on whether fentanyl or NFEPP is bound, and on the protonation state of specific MOR groups. The exquisite sensitivity of the internal protein-water hydrogen-bond network to the protonation state and to details of the drug binding could enable the MOR to elicit distinct pH- and opioid-dependent responses at its cytoplasmic G-protein-binding site.
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Affiliation(s)
- Samo Lešnik
- Faculty of Chemistry and Chemical Engineering, Laboratory of Physical Chemistry and Chemical Thermodynamics, University of Maribor, Smetanova ulica 17, SI-2000 Maribor, Slovenia
- Institute for Environmental Protection and Sensors, Beloruska ulica 7, 2000 Maribor, Slovenia
| | - Urban Bren
- Faculty of Chemistry and Chemical Engineering, Laboratory of Physical Chemistry and Chemical Thermodynamics, University of Maribor, Smetanova ulica 17, SI-2000 Maribor, Slovenia
- Institute for Environmental Protection and Sensors, Beloruska ulica 7, 2000 Maribor, Slovenia
- Faculty of Mathematics, Natural Sciences and Information Technologies, University of Primorska, SI-6000 Koper, Slovenia
| | - Tatiana Domratcheva
- Department of Chemistry, Lomonosov Moscow State University, 119991 Moscow, Russia
- Department of Biomolecular Mechanisms, Max-Plank-Institute fur Medizinische Forschung, D-69120 Heidelberg, Germany
| | - Ana-Nicoleta Bondar
- Faculty of Physics, University of Bucharest, Atomiştilor 405, 077125 Măgurele, Romania
- Institute of Computational Biomedicine, IAS-5/INM-9, Forschungszentrum Jülich, Wilhelm-Johnen Straße, 5428 Jülich, Germany
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2
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Sarkar A, Mitra A, Borics A. All-Atom Molecular Dynamics Simulations Indicated the Involvement of a Conserved Polar Signaling Channel in the Activation Mechanism of the Type I Cannabinoid Receptor. Int J Mol Sci 2023; 24:ijms24044232. [PMID: 36835641 PMCID: PMC9963961 DOI: 10.3390/ijms24044232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Revised: 02/12/2023] [Accepted: 02/15/2023] [Indexed: 02/23/2023] Open
Abstract
The type I cannabinoid G protein-coupled receptor (CB1, GPCR) is an intensely investigated pharmacological target, owing to its involvement in numerous physiological functions as well as pathological processes such as cancers, neurodegenerative diseases, metabolic disorders and neuropathic pain. In order to develop modern medications that exert their effects through binding to the CB1 receptor, it is essential to understand the structural mechanism of activation of this protein. The pool of atomic resolution experimental structures of GPCRs has been expanding rapidly in the past decade, providing invaluable information about the function of these receptors. According to the current state of the art, the activity of GPCRs involves structurally distinct, dynamically interconverting functional states and the activation is controlled by a cascade of interconnecting conformational switches in the transmembrane domain. A current challenge is to uncover how different functional states are activated and what specific ligand properties are responsible for the selectivity towards those different functional states. Our recent studies of the μ-opioid and β2-adrenergic receptors (MOP and β2AR, respectively) revealed that the orthosteric binding pockets and the intracellular surfaces of these receptors are connected through a channel of highly conserved polar amino acids whose dynamic motions are in high correlation in the agonist- and G protein-bound active states. This and independent literature data led us to hypothesize that, in addition to consecutive conformational transitions, a shift of macroscopic polarization takes place in the transmembrane domain, which is furnished by the rearrangement of polar species through their concerted movements. Here, we examined the CB1 receptor signaling complexes utilizing microsecond scale, all-atom molecular dynamics (MD) simulations in order to see if our previous assumptions could be applied to the CB1 receptor too. Apart from the identification of the previously proposed general features of the activation mechanism, several specific properties of the CB1 have been indicated that could possibly be associated with the signaling profile of this receptor.
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Affiliation(s)
- Arijit Sarkar
- Laboratory of Chemical Biology, Institute of Biochemistry, Biological Research Centre, 62 Temesvári krt., H-6726 Szeged, Hungary
- Theoretical Medicine Doctoral School, Faculty of Medicine, University of Szeged, 97 Tisza L. krt., H-6722 Szeged, Hungary
| | - Argha Mitra
- Laboratory of Chemical Biology, Institute of Biochemistry, Biological Research Centre, 62 Temesvári krt., H-6726 Szeged, Hungary
- Theoretical Medicine Doctoral School, Faculty of Medicine, University of Szeged, 97 Tisza L. krt., H-6722 Szeged, Hungary
| | - Attila Borics
- Laboratory of Chemical Biology, Institute of Biochemistry, Biological Research Centre, 62 Temesvári krt., H-6726 Szeged, Hungary
- Correspondence: ; Tel.: +36-62-599-600 (ext. 430)
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3
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Hernández-Alvarado RB, Madariaga-Mazón A, Cosme-Vela F, Marmolejo-Valencia AF, Nefzi A, Martinez-Mayorga K. Encoding mu-opioid receptor biased agonism with interaction fingerprints. J Comput Aided Mol Des 2021; 35:1081-1093. [PMID: 34713377 DOI: 10.1007/s10822-021-00422-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Accepted: 10/07/2021] [Indexed: 10/20/2022]
Abstract
Opioids are potent painkillers, however, their therapeutic use requires close medical monitoring to diminish the risk of severe adverse effects. The G-protein biased agonists of the μ-opioid receptor (MOR) have shown safer therapeutic profiles than non-biased ligands. In this work, we performed extensive all-atom molecular dynamics simulations of two markedly biased ligands and a balanced reference molecule. From those simulations, we identified a protein-ligand interaction fingerprint that characterizes biased ligands. Then, we built and virtually screened a database containing 68,740 ligands with proven or potential GPCR agonistic activity. Exemplary molecules that fulfill the interacting pattern for biased agonism are showcased, illustrating the usefulness of this work for the search of biased MOR ligands and how this contributes to the understanding of MOR biased signaling.
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Affiliation(s)
| | | | - Fernando Cosme-Vela
- Instituto de Química, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | | | - Adel Nefzi
- Center for Translational Science, Florida International University, Port St. Lucie, FL, USA.,Torrey Pines Institute for Molecular Studies, Port St. Lucie, FL, USA
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4
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Correlated Motions of Conserved Polar Motifs Lay out a Plausible Mechanism of G Protein-Coupled Receptor Activation. Biomolecules 2021; 11:biom11050670. [PMID: 33946214 PMCID: PMC8146931 DOI: 10.3390/biom11050670] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Revised: 04/17/2021] [Accepted: 04/28/2021] [Indexed: 02/01/2023] Open
Abstract
Recent advancements in the field of experimental structural biology have provided high-resolution structures of active and inactive state G protein-coupled receptors (GPCRs), a highly important pharmaceutical target family, but the process of transition between these states is poorly understood. According to the current theory, GPCRs exist in structurally distinct, dynamically interconverting functional states of which populations are shifted upon binding of ligands and intracellular signaling proteins. However, explanation of the activation mechanism, on an entirely structural basis, gets complicated when multiple activation pathways and active receptor states are considered. Our unbiased, atomistic molecular dynamics simulations of the μ opioid receptor (MOP) revealed that transmission of external stimulus to the intracellular surface of the receptor is accompanied by subtle, concerted movements of highly conserved polar amino acid side chains along the 7th transmembrane helix. This may entail the rearrangement of polar species and the shift of macroscopic polarization in the transmembrane domain, triggered by agonist binding. Based on our observations and numerous independent indications, we suggest amending the widely accepted theory that the initiation event of GPCR activation is the shift of macroscopic polarization between the ortho- and allosteric binding pockets and the intracellular G protein-binding interface.
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Wang Y, Zhang B, Lin C, Liu Y, Yang M, Peng Y, Wang X. Dissecting Role of Charged Residue from Transmembrane Domain 5 of Latent Membrane Protein 1 via In Silico Simulations and Wet-Lab Experiments. J Phys Chem B 2021; 125:2124-2133. [PMID: 33595309 DOI: 10.1021/acs.jpcb.0c10708] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Charged residues are frequently found in the transmembrane segments of membrane proteins, which reside in the hydrophobic bilayer environment. Charged residues are critical for the function of membrane protein. However, studies of their role in protein oligomerization are limited. By taking the fifth transmembrane domain (TMD5) of latent membrane protein 1 from the Epstein-Barr virus as a prototype model, in silico simulations and wet-lab experiments were performed to investigate how the charged states affect transmembrane domain oligomerization. Molecular dynamics (MD) simulations showed that the D150-protonated TMD5 trimer was stable, whereas unprotonated D150 created bends in the helices which distort the trimeric structure. D150 was mutated to asparagine to mimic the protonated D150 in TMD5, and the MD simulations of different D150N TMD5 trimers supported that the protonation state of D150 was critical for the trimerization of TMD5. In silico mutations found that D150N TMD5 preferred to interact with TMD5 to form the heterotrimer (1 D150N TMD5:2 protonated TMD5s) rather than the heterotrimer (2 D150N TMD5s:1 protonated TMD5). D150R TMD5 interacted with TMD5 to form the heterotrimer (1 D150R TMD5:2 protonated TMD5). These in silico results imply that D150N TMD5 and D150R TMD5 peptides may be probes for disrupting TMD5 trimerization, which was supported by the dominant-negative ToxR assay in bacterial membranes. In all, this study elucidates the role of charged residues at the membrane milieu in membrane protein oligomerization and provides insight into the development of oligomerization-regulating peptides for modulating transmembrane domain lateral interactions.
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Affiliation(s)
- Yibo Wang
- Laboratory of Chemical Biology, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin China, 130022
| | - Bo Zhang
- Laboratory of Chemical Biology, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin China, 130022.,Department of Applied Chemistry and Engineering, University of Science and Technology of China, Hefei, Anhui China, 230026
| | - Cong Lin
- Laboratory of Chemical Biology, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin China, 130022
| | - Ying Liu
- State Key Laboratory for Molecular Biology of Special Economic Animals, Institute of Special Animal and Plant Sciences, Chinese Academy of Agricultural Sciences, Changchun, Jilin China, 130112
| | - Min Yang
- State Key Laboratory for Molecular Biology of Special Economic Animals, Institute of Special Animal and Plant Sciences, Chinese Academy of Agricultural Sciences, Changchun, Jilin China, 130112
| | - Yinghua Peng
- State Key Laboratory for Molecular Biology of Special Economic Animals, Institute of Special Animal and Plant Sciences, Chinese Academy of Agricultural Sciences, Changchun, Jilin China, 130112
| | - Xiaohui Wang
- Laboratory of Chemical Biology, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin China, 130022.,Department of Applied Chemistry and Engineering, University of Science and Technology of China, Hefei, Anhui China, 230026
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6
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Zarzycka B, Zaidi SA, Roth BL, Katritch V. Harnessing Ion-Binding Sites for GPCR Pharmacology. Pharmacol Rev 2019; 71:571-595. [PMID: 31551350 PMCID: PMC6782022 DOI: 10.1124/pr.119.017863] [Citation(s) in RCA: 67] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Endogenous ions play important roles in the function and pharmacology of G-protein coupled receptors (GPCRs). Historically the evidence for ionic modulation of GPCR function dates to 1973 with studies of opioid receptors, where it was demonstrated that physiologic concentrations of sodium allosterically attenuated agonist binding. This Na+-selective effect was distinct from effects of other monovalent and divalent cations, with the latter usually counteracting sodium's negative allosteric modulation of binding. Since then, numerous studies documenting the effects of mono- and divalent ions on GPCR function have been published. While ions can act selectively and nonselectively at many sites in different receptors, the discovery of the conserved sodium ion site in class A GPCR structures in 2012 revealed the unique nature of Na+ site, which has emerged as a near-universal site for allosteric modulation of class A GPCR structure and function. In this review, we synthesize and highlight recent advances in the functional, biophysical, and structural characterization of ions bound to GPCRs. Taken together, these findings provide a molecular understanding of the unique roles of Na+ and other ions as GPCR allosteric modulators. We will also discuss how this knowledge can be applied to the redesign of receptors and ligand probes for desired functional and pharmacological profiles. SIGNIFICANCE STATEMENT: The function and pharmacology of GPCRs strongly depend on the presence of mono and divalent ions in experimental assays and in living organisms. Recent insights into the molecular mechanism of this ion-dependent allosterism from structural, biophysical, biochemical, and computational studies provide quantitative understandings of the pharmacological effects of drugs in vitro and in vivo and open new avenues for the rational design of chemical probes and drug candidates with improved properties.
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Affiliation(s)
- Barbara Zarzycka
- Departments of Biological Sciences (B.Z., S.A.Z., V.K.) and Chemistry (V.K.), Bridge Institute, Michelson Center for Convergent Bioscience, University of Southern California, Los Angeles, California; and Department of Pharmacology (B.L.R.) and Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy (B.L.R.), University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Saheem A Zaidi
- Departments of Biological Sciences (B.Z., S.A.Z., V.K.) and Chemistry (V.K.), Bridge Institute, Michelson Center for Convergent Bioscience, University of Southern California, Los Angeles, California; and Department of Pharmacology (B.L.R.) and Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy (B.L.R.), University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Bryan L Roth
- Departments of Biological Sciences (B.Z., S.A.Z., V.K.) and Chemistry (V.K.), Bridge Institute, Michelson Center for Convergent Bioscience, University of Southern California, Los Angeles, California; and Department of Pharmacology (B.L.R.) and Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy (B.L.R.), University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Vsevolod Katritch
- Departments of Biological Sciences (B.Z., S.A.Z., V.K.) and Chemistry (V.K.), Bridge Institute, Michelson Center for Convergent Bioscience, University of Southern California, Los Angeles, California; and Department of Pharmacology (B.L.R.) and Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy (B.L.R.), University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
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7
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Abstract
Membranes surrounding the biological cell and its internal compartments host proteins that catalyze chemical reactions essential for the functioning of the cell. Rather than being a passive structural matrix that holds membrane-embedded proteins in place, the membrane can largely shape the conformational energy landscape of membrane proteins and impact the energetics of their chemical reaction. Here, we highlight the challenges in understanding how lipids impact the conformational energy landscape of macromolecular membrane complexes whose functioning involves chemical reactions including proton transfer. We review here advances in our understanding of how chemical reactions occur at membrane interfaces gleaned with both theoretical and experimental advances using simple protein systems as guides. Our perspective is that of bridging experiments with theory to understand general physicochemical principles of membrane reactions, with a long term goal of furthering our understanding of the role of the lipids on the functioning of complex macromolecular assemblies at the membrane interface.
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Affiliation(s)
- Ana-Nicoleta Bondar
- Freie Universität Berlin , Department of Physics, Theoretical Molecular Biophysics Group , Arnimallee 14 , D-14195 Berlin , Germany
| | - M Joanne Lemieux
- University of Alberta , Department of Biochemistry, Membrane Protein Disease Research Group , Edmonton , Alberta T6G 2H7 , Canada
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8
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Eddy MT, Lee MY, Gao ZG, White KL, Didenko T, Horst R, Audet M, Stanczak P, McClary KM, Han GW, Jacobson KA, Stevens RC, Wüthrich K. Allosteric Coupling of Drug Binding and Intracellular Signaling in the A 2A Adenosine Receptor. Cell 2018; 172:68-80.e12. [PMID: 29290469 PMCID: PMC5766378 DOI: 10.1016/j.cell.2017.12.004] [Citation(s) in RCA: 100] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2017] [Revised: 09/05/2017] [Accepted: 11/30/2017] [Indexed: 10/18/2022]
Abstract
Signaling across cellular membranes, the 826 human G protein-coupled receptors (GPCRs) govern a wide range of vital physiological processes, making GPCRs prominent drug targets. X-ray crystallography provided GPCR molecular architectures, which also revealed the need for additional structural dynamics data to support drug development. Here, nuclear magnetic resonance (NMR) spectroscopy with the wild-type-like A2A adenosine receptor (A2AAR) in solution provides a comprehensive characterization of signaling-related structural dynamics. All six tryptophan indole and eight glycine backbone 15N-1H NMR signals in A2AAR were individually assigned. These NMR probes provided insight into the role of Asp522.50 as an allosteric link between the orthosteric drug binding site and the intracellular signaling surface, revealing strong interactions with the toggle switch Trp 2466.48, and delineated the structural response to variable efficacy of bound drugs across A2AAR. The present data support GPCR signaling based on dynamic interactions between two semi-independent subdomains connected by an allosteric switch at Asp522.50.
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Affiliation(s)
- Matthew T Eddy
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA; Departments of Biological Sciences and Chemistry, Bridge Institute, University of Southern California, Los Angeles, CA 90089, USA
| | - Ming-Yue Lee
- Departments of Biological Sciences and Chemistry, Bridge Institute, University of Southern California, Los Angeles, CA 90089, USA
| | - Zhan-Guo Gao
- Laboratory of Bioorganic Chemistry, NIDDK, National Institutes of Health, Bethesda, MD 20892, USA
| | - Kate L White
- Departments of Biological Sciences and Chemistry, Bridge Institute, University of Southern California, Los Angeles, CA 90089, USA
| | - Tatiana Didenko
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Reto Horst
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA; Pfizer Worldwide Research and Development, Eastern Point Road, Groton, CT 06340, USA
| | - Martin Audet
- Departments of Biological Sciences and Chemistry, Bridge Institute, University of Southern California, Los Angeles, CA 90089, USA
| | - Pawel Stanczak
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Kyle M McClary
- Departments of Biological Sciences and Chemistry, Bridge Institute, University of Southern California, Los Angeles, CA 90089, USA
| | - Gye Won Han
- Departments of Biological Sciences and Chemistry, Bridge Institute, University of Southern California, Los Angeles, CA 90089, USA
| | - Kenneth A Jacobson
- Laboratory of Bioorganic Chemistry, NIDDK, National Institutes of Health, Bethesda, MD 20892, USA
| | - Raymond C Stevens
- Departments of Biological Sciences and Chemistry, Bridge Institute, University of Southern California, Los Angeles, CA 90089, USA
| | - Kurt Wüthrich
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA; Skaggs Institute of Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
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9
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Katritch V, Fenalti G, Abola EE, Roth BL, Cherezov V, Stevens RC. Allosteric sodium in class A GPCR signaling. Trends Biochem Sci 2014; 39:233-44. [PMID: 24767681 DOI: 10.1016/j.tibs.2014.03.002] [Citation(s) in RCA: 359] [Impact Index Per Article: 35.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 03/11/2014] [Accepted: 03/12/2014] [Indexed: 01/16/2023]
Abstract
Despite their functional and structural diversity, G-protein-coupled receptors (GPCRs) share a common mechanism of signal transduction via conformational changes in the seven-transmembrane (7TM) helical domain. New major insights into this mechanism come from the recent crystallographic discoveries of a partially hydrated sodium ion that is specifically bound in the middle of the 7TM bundle of multiple class A GPCRs. This review discusses the remarkable structural conservation and distinct features of the Na(+) pocket in this most populous GPCR class, as well as the conformational collapse of the pocket upon receptor activation. New insights help to explain allosteric effects of sodium on GPCR agonist binding and activation, and sodium's role as a potential co-factor in class A GPCR function.
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Affiliation(s)
- Vsevolod Katritch
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
| | - Gustavo Fenalti
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Enrique E Abola
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Bryan L Roth
- National Institute of Mental Health Psychoactive Drug Screening Program, Department of Pharmacology and Division of Chemical Biology and Medicinal Chemistry, University of North Carolina Chapel Hill Medical School, Chapel Hill, NC 27599, USA
| | - Vadim Cherezov
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Raymond C Stevens
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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10
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Abstract
Opiates are among the oldest medications available to manage a number of medical problems. Although pain is the current focus, early use initially focused upon the treatment of dysentery. Opium contains high concentrations of both morphine and codeine, along with thebaine, which is used in the synthesis of a number of semisynthetic opioid analgesics. Thus, it is not surprising that new agents were initially based upon the morphine scaffold. The concept of multiple opioid receptors was first suggested almost 50 years ago (Martin, 1967), opening the possibility of new classes of drugs, but the morphine-like agents have remained the mainstay in the medical management of pain. Termed mu, our understanding of these morphine-like agents and their receptors has undergone an evolution in thinking over the past 35 years. Early pharmacological studies identified three major classes of receptors, helped by the discovery of endogenous opioid peptides and receptor subtypes-primarily through the synthesis of novel agents. These chemical biologic approaches were then eclipsed by the molecular biology revolution, which now reveals a complexity of the morphine-like agents and their receptors that had not been previously appreciated.
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Affiliation(s)
- Gavril W Pasternak
- Memorial Sloan-Kettering Cancer Center, 1275 York Ave, New York, NY 10065.
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11
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PKA and ERK1/2 are involved in dopamine D₁ receptor-induced heterologous desensitization of the δ opioid receptor. Life Sci 2013; 92:1101-9. [PMID: 23624231 DOI: 10.1016/j.lfs.2013.04.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Revised: 04/02/2013] [Accepted: 04/16/2013] [Indexed: 11/21/2022]
Abstract
AIMS Chronic administration of cocaine attenuates delta opioid receptor (DOPR) signaling in the striatum and the desensitization is mediated by the indirect actions of cocaine on dopamine D1 receptors (D1R). In addition, DOPR and D1R co-exist in some rat striatal neurons. In the present study, we examined the underlying mechanism of DOPR desensitization by D1R activation. MAIN METHODS NG 108-15 cells stably expressing HA-rat D1 receptor (HA-D1R) and Chinese hamster ovary (CHO) cells stably expressing both FLAG-mouse DOPR (FLAG-DOPR) and HA-D1R were used as the cell models. Receptor binding, [(35)S]GTPγS binding, receptor phosphorylation and western blot were conducted to examine DOPR affinity, expression, internalization, downregulation, desensitization, phosphorylation and phosphorylated ERK1/2. KEY FINDINGS Pretreatment with either the DOPR agonist DPDPE or the D1R agonist SKF-82958 for 30min attenuated DPDPE-stimulated [(35)S]GTPγS binding to G proteins, demonstrating homologous and heterologous desensitization of the DOPR, respectively. SKF-82958 pretreatment did not affect the level of DOPR or affinity of DOPR antagonist or agonists, nor did it induce phosphorylation, internalization or down-regulation of the DOPR in the CHO-FLAG-DOPR/HA-D1R cells. Pretreatment of cells with inhibitors of PKA, MEK1 and PI3K, but not PKC, attenuated SKF-82958-induced desensitization of the DOPR. The D1R agonist SKF-82958 enhanced phosphorylation of ERK1/2, and pretreatment with inhibitors of MEK1 and PI3K, but not PKA and PKC, reduced the effect. These results indicate that activation of ERK1/2 and/or PKA, but not PKC, is involved in D1 receptor-induced heterologous desensitization of the DOPR. SIGNIFICANCE This study provides possible mechanisms underlying D1R activation-induced DOPR desensitization.
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12
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Provasi D, Bortolato A, Filizola M. Exploring molecular mechanisms of ligand recognition by opioid receptors with metadynamics. Biochemistry 2009; 48:10020-9. [PMID: 19785461 DOI: 10.1021/bi901494n] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Opioid receptors are G protein-coupled receptors (GPCRs) of utmost significance in the development of potent analgesic drugs for the treatment of severe pain. An accurate evaluation at the molecular level of the ligand binding pathways into these receptors may play a key role in the design of new molecules with more desirable properties and reduced side effects. The recent characterization of high-resolution X-ray crystal structures of non-rhodopsin GPCRs for diffusible hormones and neurotransmitters presents an unprecedented opportunity to build improved homology models of opioid receptors, and to study in more detail their molecular mechanisms of ligand recognition. In this study, possible pathways for entry of the nonselective antagonist naloxone (NLX) from the water environment into the well-accepted alkaloid binding pocket of a delta opioid receptor (DOR) molecular model based on the beta2-adrenergic receptor crystal structure are explored using microsecond-scale well-tempered metadynamics simulations. Using as collective variables distances that account for the position of NLX and of the receptor extracellular loop 2 in relation to the DOR binding pocket, we were able to distinguish between the different states visited by the ligand (i.e., docked, undocked, and metastable bound intermediates) and to predict a free energy of binding close to experimental values after correcting for possible drawbacks of the sampling approach. The strategy employed herein holds promise for its application to the docking of diverse ligands to the opioid receptors as well as to other GPCRs.
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Affiliation(s)
- Davide Provasi
- Department of Structural and Chemical Biology, Mount Sinai School of Medicine, New York, New York 10029, USA
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13
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Allosteric communication between protomers of dopamine class A GPCR dimers modulates activation. Nat Chem Biol 2009; 5:688-95. [PMID: 19648932 PMCID: PMC2817978 DOI: 10.1038/nchembio.199] [Citation(s) in RCA: 285] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2008] [Accepted: 04/28/2009] [Indexed: 01/09/2023]
Abstract
A major obstacle to understanding the functional importance of dimerization between Class A G protein-coupled receptors (GPCRs) has been the methodological limitation in achieving control of the identity of the components comprising the signaling unit. We have developed a functional complementation assay that enables such control and illustrate it for the human dopamine D2 receptor. The minimal signaling unit, two receptors and a single G protein, is maximally activated by agonist binding to a single protomer, which suggests an asymmetrical activated dimer. Inverse agonist binding to the second protomer enhances signaling, whereas agonist binding to the second protomer blunts signaling. Ligand-independent constitutive activation of the second protomer also inhibits signaling. Thus, GPCR dimer function can be modulated by the activity state of the second protomer, which for a heterodimer may be altered in pathological states. Our novel methodology also makes possible the characterization of signaling from a defined heterodimer unit.
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Brasel CM, Sawyer GW, Stevens CW. A pharmacological comparison of the cloned frog and human mu opioid receptors reveals differences in opioid affinity and function. Eur J Pharmacol 2008; 599:36-43. [PMID: 18930720 DOI: 10.1016/j.ejphar.2008.09.043] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2008] [Revised: 09/23/2008] [Accepted: 09/29/2008] [Indexed: 10/21/2022]
Abstract
This study presents a direct comparison of the ligand binding and signaling profiles of a mammalian and non-mammalian mu opioid receptor. Opioid ligand binding and agonist potencies were determined for an amphibian (Rana pipiens) mu opioid receptor (rpMOR) and the human mu opioid receptor (hMOR) in transfected, intact Chinese hamster ovary (CHO) cells. Identical conditions were employed such that statistically meaningful differences between the two receptors could be determined. Identifying these differences is an important first step in understanding how evolutionary changes affect ligand binding and signaling in vertebrate opioid receptors. As expected, the rank of opioid ligand affinity for rpMOR and hMOR was consistent with the ligands' previously characterized type-selectivity. However, most of the opioid ligands tested had significant differences in affinity for rpMOR and hMOR. For example, the mu-selective agonist, DAMGO ([d-Ala(2), N-Me-Phe(4), Gly(5)-ol]-enkephalin), had a 10.9-fold greater affinity (K(i)) for hMOR (K(i)=268 nM) than rpMOR (K(i)=2914 nM). In addition, differences in signaling between these receptors were found by measuring inhibition of cAMP accumulation by morphine or DAMGO. DAMGO was significantly more potent (13.6-fold) in CHO cells expressing hMOR versus those expressing rpMOR. In addition, a significantly greater maximal inhibition was elicited by both opioid agonists in cells expressing hMOR. In summary, this study supports an ongoing effort to better understand how vertebrate evolution has shaped opioid receptor properties and function.
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Affiliation(s)
- Chris M Brasel
- Dept. of Pharmacology and Physiology, OSU-Center for Health Sciences, Tulsa, OK 74107-1898, USA
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15
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Kapur A, Samaniego P, Thakur GA, Makriyannis A, Abood ME. Mapping the structural requirements in the CB1 cannabinoid receptor transmembrane helix II for signal transduction. J Pharmacol Exp Ther 2008; 325:341-8. [PMID: 18174385 DOI: 10.1124/jpet.107.133256] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Amino acid residues in the transmembrane domains of the CB(1) receptor are important for ligand recognition and signal transduction. We used site-directed mutagenesis to identify the role of two novel and adjacent residues in the transmembrane helix II domain, Ile2.62 and Asp2.63. We investigated the role of the conserved, negatively charged aspartate at position 2.63 in cannabinoid receptor (CB(1)) function by substituting it with asparagine (D2.63N) and glutamate (D2.63E). In addition, the effect of the mutant I2.62T alone and in combination with D2.63N (double mutant) on the affinity and potency of structurally diverse ligands was investigated. Recombinant human CB(1) receptors, stably expressed in human embryonic kidney 293 cells, were assayed for ligand affinity and agonist-stimulated guanosine 5'-3-O-(thio)triphosphate (GTPgammaS) binding. The charge-conserved mutant D2.63E behaved similar to wild type. The charge-neutralization mutation D2.63N attenuated the potency of (-)-3-[2-hydroxyl-4-(1,1-dimethylheptyl)phenyl]-4-[3-hydroxylpropyl] cyclohexan-1-ol (CP,55940), (R)-(-)-[2,3-dihydro-5-methyl-3-[(4-morpholinyl)methyl]pyrrolo[1,2,3-de]-1,4-benzoxazin-6-yl](1-naphthalenyl)methanone (WIN55212-2), (-)-11beta-hydroxy-3-(1',1'-dimethylheptyl) hexahydrocannabinol (AM4056), and (-)-11-hydroxyldimethylheptyl-Delta(8)-tetrahydrocannabinol (HU210) for the stimulation of GTPgammaS binding, without affecting their binding affinities. Likewise, the I2.62T mutant selectively altered agonist potency without altering agonist affinity. It was surprising to note that the double mutant (I2.62T-D2.63N) displayed a drastic and synergistic increase (by approximately 50-fold) in the EC(50) for agonist-mediated activation. The profound loss of function in the I2.62T-D2.63N double mutant suggests that, although these residues are not obligatory for agonist recognition, they play a synergistic and crucial role in modulating signal transduction.
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Affiliation(s)
- Ankur Kapur
- California Pacific Medical Center Research Institute, San Francisco, California, USA
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16
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Bee MS, Hulme EC. Functional analysis of transmembrane domain 2 of the M1 muscarinic acetylcholine receptor. J Biol Chem 2007; 282:32471-9. [PMID: 17823120 DOI: 10.1074/jbc.m703909200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ala substitution scanning mutagenesis has been used to probe the functional role of amino acids in transmembrane (TM) domain 2 of the M1 muscarinic acetylcholine receptor, and of the highly conserved Asn43 in TM1. The mutation of Asn43, Asn61, and Leu64 caused an enhanced ACh affinity phenotype. Interpreted using a rhodopsin-based homology model, these results suggest the presence of a network of specific contacts between this group of residues and Pro415 and Tyr418 in the highly conserved NPXXY motif in TM7 that exhibit a similar mutagenic phenotype. These contacts may be rearranged or broken when ACh binds. D71A, like N414A, was devoid of signaling activity. We suggest that formation of a direct hydrogen bond between the highly conserved side chains of Asp71 and Asn414 may be a critical feature stabilizing the activated state of the M1 receptor. Mutation of Leu67, Ala70, and Ile74 also reduced the signaling efficacy of the ACh-receptor complex. The side chains of these residues are modeled as an extended surface that may help to orient and insulate the proposed hydrogen bond between Asp71 and Asn414. Mutation of Leu72, Gly75, and Met79 in the outer half of TM2 primarily reduced the expression of functional receptor binding sites. These residues may mediate contacts with TM1 and TM7 that are preserved throughout the receptor activation cycle. Thermal inactivation measurements confirmed that a reduction in structural stability followed the mutation of Met79 as well as Asp71.
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Affiliation(s)
- Mark S Bee
- Division of Physical Biochemistry, MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, United Kingdom
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17
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Xu W, Campillo M, Pardo L, de Riel JK, Liu-Chen LY. The seventh transmembrane domains of the delta and kappa opioid receptors have different accessibility patterns and interhelical interactions. Biochemistry 2006; 44:16014-25. [PMID: 16331961 PMCID: PMC2688720 DOI: 10.1021/bi050938a] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We applied the substituted cysteine accessibility method (SCAM) to map the residues of the transmembrane helices (TMs) 7 of delta and kappa opioid receptors (deltaOR and kappaOR) that are on the water-accessible surface of the binding-site crevices. A total of 25 consecutive residues (except C7.38) in the TMs 7 were mutated to Cys, one at a time, and each mutant was expressed in HEK 293 cells. Most mutants displayed similar binding affinity for [(3)H]diprenorphine, an antagonist, as the wild types. Pretreatment with (2-aminoethyl)methanethiosulfonate (MTSEA) inhibited [(3)H]diprenorphine binding to eight deltaOR and eight kappaOR mutants. All mutants except deltaOR L7.52(317)C were protected by naloxone from the MTSEA effect, indicating that the side chains of V7.31(296), A7.34(299), I7.39(304), L7.41(306), G7.42(307), P7.50(315), and Y7.53(318) of deltaOR and S7.34(311), F7.37(314), I7.39(316), A7.40(317), L7.41(318), G7.42(319), Y7.43(320), and N7.49(326) of kappaOR are on the water-accessible surface of the binding pockets. Combining the SCAM data with rhodopsin-based molecular models of the receptors led to the following conclusions. (i) The residues of the extracellular portion of TM7 predicted to face TM1 are sensitive to MTSEA in kappaOR but are not in deltaOR. Thus, TM1 may be closer to TM7 in deltaOR than in kappaOR. (ii) MTSEA-sensitive mutants start at position 7.31(296) in deltaOR and at 7.34(311) in kappaOR, suggesting that TM7 in deltaOR may have an additional helical turn (from 7.30 to 7.33). (iii) There is a conserved hydrogen-bond network linking D2.50 of the NLxxxD motif in TM2 with W6.48 of the CWxP motif in TM6. (iv) The NPxxY motif in TM7 interacts with TM2, TM6, and helix 8 to maintain receptors in inactive states. To the best of our knowledge, this represents the first such comparison of the structures of two highly homologous GPCRs.
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MESH Headings
- Amino Acid Sequence
- Animals
- Binding Sites
- Cattle
- Cell Line
- Cysteine/metabolism
- Humans
- Hydrogen Bonding
- Models, Molecular
- Molecular Sequence Data
- Protein Structure, Secondary
- Receptors, Opioid, delta/chemistry
- Receptors, Opioid, delta/genetics
- Receptors, Opioid, kappa/chemistry
- Receptors, Opioid, kappa/genetics
- Sequence Alignment
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Affiliation(s)
- Wei Xu
- Department of Pharmacology and Center for Substance Abuse Research, Temple University School of Medicine, Philadelphia, PA
| | - Mercedes Campillo
- Laboratori de Medicina Computacional, Unitat de Bioestadística and Institut de Neurociències, Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona), Spain
| | - Leonardo Pardo
- Laboratori de Medicina Computacional, Unitat de Bioestadística and Institut de Neurociències, Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona), Spain
| | - J. Kim de Riel
- Fels Institute for Molecular Biology and Cancer Research, Temple University School of Medicine, Philadelphia, PA
| | - Lee-Yuan Liu-Chen
- Department of Pharmacology and Center for Substance Abuse Research, Temple University School of Medicine, Philadelphia, PA
- Address correspondence to: Dr. Lee-Yuan Liu-Chen, Department of Pharmacology, Temple University School of Medicine, 3420 N. Broad St., Philadelphia, PA 19140, phone: (215) 707−4188; fax: (215) 707−7068; e-mail:
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Zhang Y, DeVries ME, Skolnick J. Structure modeling of all identified G protein-coupled receptors in the human genome. PLoS Comput Biol 2006; 2:e13. [PMID: 16485037 PMCID: PMC1364505 DOI: 10.1371/journal.pcbi.0020013] [Citation(s) in RCA: 151] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2005] [Accepted: 01/11/2005] [Indexed: 12/22/2022] Open
Abstract
G protein–coupled receptors (GPCRs), encoded by about 5% of human genes, comprise the largest family of integral membrane proteins and act as cell surface receptors responsible for the transduction of endogenous signal into a cellular response. Although tertiary structural information is crucial for function annotation and drug design, there are few experimentally determined GPCR structures. To address this issue, we employ the recently developed threading assembly refinement (TASSER) method to generate structure predictions for all 907 putative GPCRs in the human genome. Unlike traditional homology modeling approaches, TASSER modeling does not require solved homologous template structures; moreover, it often refines the structures closer to native. These features are essential for the comprehensive modeling of all human GPCRs when close homologous templates are absent. Based on a benchmarked confidence score, approximately 820 predicted models should have the correct folds. The majority of GPCR models share the characteristic seven-transmembrane helix topology, but 45 ORFs are predicted to have different structures. This is due to GPCR fragments that are predominantly from extracellular or intracellular domains as well as database annotation errors. Our preliminary validation includes the automated modeling of bovine rhodopsin, the only solved GPCR in the Protein Data Bank. With homologous templates excluded, the final model built by TASSER has a global Cα root-mean-squared deviation from native of 4.6 Å, with a root-mean-squared deviation in the transmembrane helix region of 2.1 Å. Models of several representative GPCRs are compared with mutagenesis and affinity labeling data, and consistent agreement is demonstrated. Structure clustering of the predicted models shows that GPCRs with similar structures tend to belong to a similar functional class even when their sequences are diverse. These results demonstrate the usefulness and robustness of the in silico models for GPCR functional analysis. All predicted GPCR models are freely available for noncommercial users on our Web site (http://www.bioinformatics.buffalo.edu/GPCR). G protein–coupled receptors (GPCRs) are a large superfamily of integral membrane proteins that transduce signals across the cell membrane. Because of the breadth and importance of the physiological roles undertaken by the GPCR family, many of its members are important pharmacological targets. Although the knowledge of a protein's native structure can provide important insight into understanding its function and for the design of new drugs, the experimental determination of the three-dimensional structure of GPCR membrane proteins has proved to be very difficult. This is demonstrated by the fact that there is only one solved GPCR structure (from bovine rhodopsin) deposited in the Protein Data Bank library. In contrast, there are no human GPCR structures in the Protein Data Bank. To address the need for the tertiary structures of human GPCRs, using just sequence information, the authors use a newly developed threading-assembly-refinement method to generate models for all 907 registered GPCRs in the human genome. About 820 GPCRs are anticipated to have correct topology and transmembrane helix arrangement. A subset of the resulting models is validated by comparison with mutagenesis experimental data, and consistent agreement is demonstrated.
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Affiliation(s)
- Yang Zhang
- Center of Excellence in Bioinformatics, University at Buffalo, Buffalo, New York, United States of America
| | - Mark E DeVries
- Center of Excellence in Bioinformatics, University at Buffalo, Buffalo, New York, United States of America
| | - Jeffrey Skolnick
- Center of Excellence in Bioinformatics, University at Buffalo, Buffalo, New York, United States of America
- * To whom correspondence should be addressed. E-mail:
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Weinstein H. Hallucinogen actions on 5-HT receptors reveal distinct mechanisms of activation and signaling by G protein-coupled receptors. AAPS JOURNAL 2006; 7:E871-84. [PMID: 16594640 PMCID: PMC2750957 DOI: 10.1208/aapsj070485] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
We review the effect of some key advances in the characterization of molecular mechanisms of signaling by G protein-coupled receptors (GPCRs) on our current understanding of mechanisms of drugs of abuse. These advances are illustrated by results from our ongoing work on the actions of hallucinogens on serotonin (5-HT) receptors. We show how a combined computational and experimental approach can reveal specific modes of receptor activation underlying the difference in properties of hallucinogens compared with nonhallucinogenic congeners. These modes of activation-that can produce distinct ligand-dependent receptor states-are identified in terms of structural motifs (SM) in molecular models of the receptors, which were shown to constitute conserved functional microdomains (FM). The role of several SM/FMs in the activation mechanism of the GPCRs is presented in detail to illustrate how this mechanism can lead to ligand-dependent modes of signaling by the receptors. Novel bioinformatics tools are described that were designed to support the quantitative mathematical modeling of ligand-specific signaling pathways activated by the 5-HT receptors targeted by hallucinogens. The approaches for mathematical modeling of signaling pathways activated by 5-HT receptors are described briefly in the context of ongoing work on detailed biochemical models of 5-HT2A, and combined 5-HT2A/5-HT1A, receptor-mediated activation of the MAPK 1,2 pathway. The continuing need for increasingly more realistic representation of signaling in dynamic compartments within the cell, endowed with spatio-temporal characteristics obtained from experiment, is emphasized. Such developments are essential for attaining a quantitative understanding of how the multiple functions of a cell are coordinated and regulated, and to evaluate the specifics of the perturbations caused by the drugs of abuse that target GPCRs.
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Affiliation(s)
- Harel Weinstein
- Department of Physiology and Biophysics, Institute for Computational Biomedicine, Weill Medical College of Cornell University, New York, NY 10021, USA.
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20
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Shacham S, Marantz Y, Bar-Haim S, Kalid O, Warshaviak D, Avisar N, Inbal B, Heifetz A, Fichman M, Topf M, Naor Z, Noiman S, Becker OM. PREDICT modeling and in-silico screening for G-protein coupled receptors. Proteins 2005; 57:51-86. [PMID: 15326594 DOI: 10.1002/prot.20195] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
G-protein coupled receptors (GPCRs) are a major group of drug targets for which only one x-ray structure is known (the nondrugable rhodopsin), limiting the application of structure-based drug discovery to GPCRs. In this paper we present the details of PREDICT, a new algorithmic approach for modeling the 3D structure of GPCRs without relying on homology to rhodopsin. PREDICT, which focuses on the transmembrane domain of GPCRs, starts from the primary sequence of the receptor, simultaneously optimizing multiple 'decoy' conformations of the protein in order to find its most stable structure, culminating in a virtual receptor-ligand complex. In this paper we present a comprehensive analysis of three PREDICT models for the dopamine D2, neurokinin NK1, and neuropeptide Y Y1 receptors. A shorter discussion of the CCR3 receptor model is also included. All models were found to be in good agreement with a large body of experimental data. The quality of the PREDICT models, at least for drug discovery purposes, was evaluated by their successful utilization in in-silico screening. Virtual screening using all three PREDICT models yielded enrichment factors 9-fold to 44-fold better than random screening. Namely, the PREDICT models can be used to identify active small-molecule ligands embedded in large compound libraries with an efficiency comparable to that obtained using crystal structures for non-GPCR targets.
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21
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Chen C, Li J, Bot G, Szabo I, Rogers TJ, Liu-Chen LY. Heterodimerization and cross-desensitization between the mu-opioid receptor and the chemokine CCR5 receptor. Eur J Pharmacol 2004; 483:175-86. [PMID: 14729105 DOI: 10.1016/j.ejphar.2003.10.033] [Citation(s) in RCA: 125] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Cross-desensitization between micro-opioid receptor agonists and CC chemokines was shown to occur in immune cells and in the central nervous system. However, these cells do not permit examination of potential mechanisms at cellular levels due to low levels and mixed populations of receptors. In this study, we investigated possible interactions and biochemical mechanisms of cross-desensitization between the mu-opioid and chemokine CCR5 receptors coexpressed in Chinese hamster ovary (CHO) cells. Hemagglutinin (HA)-tagged micro-opioid receptor coimmunoprecipitated with FLAG (Asp-Tyr-Lys-Asp-Asp-Asp-Asp-Lys)-tagged chemokine receptor CCR5 in cells expressing the two receptors, but not in a mixture of cells transfected with one of the two receptors, indicating that the two receptors form heterodimers. Treatment with the mu-opioid receptor agonist DAMGO ([D-Ala(2), N-Me-Phe(4), Gly(5)-ol]-enkephalin), the chemokine RANTES (Regulated on Activation, Normal T cell-Expressed and -Secreted) (CCL5), or both, did not affect the level of coimmunoprecipitation. DAMGO and RANTES (CCL5) induced chemotaxis in CHO cells coexpressing both receptors, and preincubation with either DAMGO or RANTES (CCL5) profoundly inhibited chemotaxis caused by the other. DAMGO pretreatment enhanced phosphorylation of the chemokine CCR5 receptor and reduced RANTES (CCL5)-promoted [35S]GTP gamma S binding. Conversely, RANTES (CCL5) preincubation slightly increased phosphorylation of the mu-opioid receptor and significantly reduced DAMGO-induced [35S]GTP gamma S binding. These results indicate that activation of either receptor affected G protein coupling of the other, likely due to enhanced phosphorylation of the receptor. Heterodimerization between the two receptors may contribute to the observed cross-desensitization.
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Affiliation(s)
- Chongguang Chen
- Department of Pharmacology and Center for Substance Abuse Research, Temple University School of Medicine, 3420 North Broad Street, Philadelphia, PA 19140, USA
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22
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Wang X, Douglas SD, Commons KG, Pleasure DE, Lai J, Ho C, Bannerman P, Williams M, Ho W. A non-peptide substance P antagonist (CP-96,345) inhibits morphine-induced NF-kappa B promoter activation in human NT2-N neurons. J Neurosci Res 2004; 75:544-53. [PMID: 14743438 DOI: 10.1002/jnr.10873] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Opioids and the neuropeptide substance P (SP) modulate the expression of inflammatory cytokines and chemokines, which are under the control of nuclear factor kappaB (NF-kappaB). We investigated whether the neurokinin-1 receptor (SP receptor) pathway is biologically involved in morphine-mediated modulation of NF-kappaB promoter activation in a human neuronal cell line (NT2-N) that expresses both the mu-opioid receptor (MOR) and the SP receptor. Morphine significantly enhanced NF-kappaB promoter-directed luciferase activity in NT2-N neurons. DAMGO, a selective mu-opioid receptor agonist, also induced NF-kappaB promoter activation. The induced activation of NF-kappaB promoter by morphine or DAMGO was abolished not only by naltrexone (a opioid receptor antagonist) and CTAP (a selective, competitive mu-opioid receptor antagonist), but also by CP-96,345, a non-peptide SP receptor antagonist. Investigation of the mechanism responsible for morphine-induced activation of NF-kappaB promoter in NT2-N neurons demonstrated that morphine activates the SP promoter and induces SP expression in these cells. We also observed that SP activated NF-kappaB promoter and that CP-96,345 downregulated the expression of endogenous SP. Furthermore, dual immunofluorescent labeling revealed that there is co-expression of NK-1R and MOR in the processes of NT-2N neurons. These results suggest that morphine, by activating MOR, engages a positive feedback loop between NK-1R and SP. Activation of NK-1R could then impact NF-kappaB expression and therefore may be an important participant in the effect of morphine on immune responses in the central nervous system.
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Affiliation(s)
- Xu Wang
- Division of Immunologic and Infectious Diseases, Joseph Stokes Jr. Research Institute of The Children's Hospital of Philadelphia, Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA
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Kakar SS, Malik MT, Winters SJ, Mazhawidza W. Gonadotropin-releasing hormone receptors: structure, expression, and signaling transduction. VITAMINS AND HORMONES 2004; 69:151-207. [PMID: 15196882 DOI: 10.1016/s0083-6729(04)69006-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Sham S Kakar
- Department of Medicine, University of Louisville, Louisville, Kentucky 40202, USA
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Pil J, Tytgat J. Serine 329 of the mu-opioid receptor interacts differently with agonists. J Pharmacol Exp Ther 2003; 304:924-30. [PMID: 12604666 DOI: 10.1124/jpet.102.040113] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To investigate the effect of the hydrophilic Ser amino acid in position 329 of the human mu-opioid receptor (hMORwt) on the potency of various agonists, we mutated this residue to Ala (hMORS329A). Taking advantage of the functional coupling of the opioid receptor with the heteromultimeric G-protein-coupled inwardly rectifying potassium channel (GIRK1/GIRK2), either the wild-type hMOR or the mutated receptor (hMORS329A) was functionally coexpressed with GIRK1 and GIRK2 channels together with a regulator of G-protein signaling (RGS4) in Xenopus laevis oocytes. The two-microelectrode voltage-clamp technique was used to measure the opioid receptor activated GIRK1/GIRK2 channel responses. The potency of the peptide agonist [D-Ala(2),N-MePhe(4),Gly(5)-ol]-enkephalin (DAMGO) decreased as measured via hMORS329A, whereas the potency of nonpeptide agonists like morphine, fentanyl, and beta-hydroxyfentanyl (R004333) increased via the mutated receptor. Our results are indicative for the existence of hydrophilic interactions between Ser(329) and DAMGO, thereby decreasing the potency of DAMGO via the mutated receptor, whereas hydrophobic interactions between the mutated receptor and the N-phenylethyl of morphine and fentanyl can explain the increased potency. We conclude that the hydroxyl group of Ser(329) is not involved in the formation of a hydrogen bond with the beta-hydroxy group of fentanyl and that mutation of this residue to alanine caused dual effects depending on the nature of the ligand.
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Affiliation(s)
- Joost Pil
- Laboratory of Toxicology, Faculty of Pharmaceutical Sciences, University of Leuven, Leuven, Belgium
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25
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Shi L, Javitch JA. The binding site of aminergic G protein-coupled receptors: the transmembrane segments and second extracellular loop. Annu Rev Pharmacol Toxicol 2002; 42:437-67. [PMID: 11807179 DOI: 10.1146/annurev.pharmtox.42.091101.144224] [Citation(s) in RCA: 270] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In the current chapter, we review approaches to the identification of the residues forming the binding sites for agonists, antagonists, and allosteric modulators in the family of aminergic G protein-coupled receptors (GPCRs). We then review the structural bases for ligand binding and pharmacological specificity based on the application of these methods to muscarinic cholinergic, adrenergic, dopaminergic, serotonergic, and histaminergic receptors, using the high resolution rhodopsin structure as a template. Furthermore, we propose a critical role of the second extracellular loop in forming the binding site for small molecular weight aminergic ligands, much as this loop dives down into the binding-site crevice and contacts retinal in rhodopsin.
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Affiliation(s)
- Lei Shi
- Center for Molecular Recognition and Department of Pharmacology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA.
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26
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Meini S, Cucchi P, Zappitelli S, Rotondaro L, Quartara L, Giolitti A, Maggi CA. Preliminary mutational analysis of the human kinin B2 receptor for nonpeptide antagonist ligands recognition. Can J Physiol Pharmacol 2002; 80:303-9. [PMID: 12025965 DOI: 10.1139/y02-027] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
FR173657, LF16,0335, and LF16,0687 are nonpeptide antagonists, endowed with high affinity and selectivity for the human kinin B2 receptor. The kinin B2 receptor belongs to the family of G-protein-coupled receptors with seven transmembrane (TM) helices. In the present study, we aimed, through computer-assisted modeling and mutagenesis, to identify residues in the human B2 receptor (hB2R) amino acid sequence that are involved in nonpeptide antagonist binding in order to build up experimental data as a first step towards a molecular model of nonpeptide ligands binding site. Fourteen amino acid residues within the TM segments were mutated to alanine. The wild type and mutant receptors were stably expressed in Chinese hamster ovary (dhfr-) cells and tested for their ability to bind agonist ([3H]bradykinin) and peptide antagonist ([3H]MENI 1270) radioligands. The affinity of nonpeptide ligands was determined by heterologous competition experiments using the above radioligands. We found that some mutations in TM2 (W86A) and TM7 (Y295A, N297A) impair the binding affinity of the three nonpeptide antagonists. On the other hand, some mutated residues in TM3 (S1 17A) and TM6 (W256A) reduce the affinity of LF16,0335 and LF16,0687 only. Results are discussed in order to build up a hypothesis for the likely different interactions of various nonpeptide ligands with the B2 receptor.
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Affiliation(s)
- Stefania Meini
- Department of Pharmacology, Menarini Ricerche, Florence, Italy.
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27
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Abstract
The sequencing of the human genome is only the first step. The next step is to determine the function of these genes and in particular, how alterations in specific genes lead to major human disorders. Many laboratories are now focusing on identifying and characterizing single nucleotide polymorphisms (SNPs), to determine which correlate in frequency with certain population groups who may be particularly susceptible to certain diseases. The mu opioid receptor (MOR), which mediates the clinically important analgesic effects of drugs like morphine as well as the euphoria sought by heroin abusers, exhibits several dozen polymorphisms. Several of these are associated with altered receptor function and individuals at risk for drug abuse.
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Affiliation(s)
- Nancy M Lee
- California Pacific Medical Center Research Institute, 2330 Clay Street, Stern Bldg., San Francisco, CA 94115, USA.
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28
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Structural domains of the CB1 cannabinoid receptor that contribute to constitutive activity and G-protein sequestration. J Neurosci 2001. [PMID: 11698587 DOI: 10.1523/jneurosci.21-22-08758.2001] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The CB1 cannabinoid receptor is a constitutively active receptor that can sequester G(i/o)-proteins and prevent other G(i/o)-coupled receptors from signaling (Bouaboula et al., 1997; Pan et al., 1998; Vasquez and Lewis, 1999). G-protein sequestration occurs because the population of CB1 cannabinoid receptors exists in both an inactive G-protein-precoupled RG(GDP) state and a constitutively active R*G(GTP) state. We tested the hypothesis that the distal C-terminal tail acts to prevent G-protein activation. We found that truncation of the distal C-terminal tail of the CB1 receptor (CB1-417) enhanced both the constitutive activity and the ability of the receptor to sequester G-proteins. In addition, we tested the hypothesis that the conserved aspartate (D2.50) in the second transmembrane domain of the CB1 cannabinoid receptor is crucial for constitutive activity and G-protein sequestration. We found that the mutation of aspartate to asparagine (CB1-D164N) abolished G-protein sequestration and constitutive receptor activity without disrupting agonist-stimulated activity. We conclude that the CB1-D164N mutation and the C-terminal truncation shift the population of receptors in opposite directions. The CB1-D164N mutation shifts the receptor into an inactive R state upcoupled from G-proteins, whereas the C-terminal truncation (CB1-417) shifts the receptor into the active R*G(GTP) state. Thus the distal C-terminal tail acts to constrain the receptor from activating G-proteins, whereas the aspartate (D2.50) in the second transmembrane domain stabilizes the receptor in both the inactive RG(GDP) state and the active R*G(GTP) state.
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29
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Pil J, Tytgat J. The role of the hydrophilic Asn230 residue of the mu-opioid receptor in the potency of various opioid agonists. Br J Pharmacol 2001; 134:496-506. [PMID: 11588103 PMCID: PMC1572970 DOI: 10.1038/sj.bjp.0704263] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. To investigate the effect of the hydrophilic Asn amino acid at position 230 of the human mu-opioid receptor (hMOR230) on the potency of various agonists, we mutated this residue to Thr and Leu (hMORN230T and hMORN230L respectively). 2. Taking advantage of the functional coupling of the opioid receptor with the heteromultimeric G-protein-coupled inwardly rectifying K(+) (GIRK1/GIRK2) channel, either the wild type hMOR or one of the mutated receptors (hMORN230L or hMORN230T) were functionally coexpressed with GIRK1/GIRK2 channels and a regulator of G-protein signalling (RGS4) in Xenopus laevis oocytes. 3. The two-microelectrode voltage clamp technique was used to measure the opioid receptor-activated GIRK1/GIRK2 channel responses. The potency of [D-Ala(2),N-MePhe(4),Gly(5)-ol]-enkephalin (DAMGO), remained unaffected as measured via hMORN230T and hMORN230L, while the potency of fentanyl and morphine significantly increased via these mutated receptors. 4. Our results are indicative for the existence of hydrophobic interactions between a methyl-group of the side chain of Thr or Leu on the one hand and the piperidine-ring of fentanyl and the hexene-ring of morphine on the other. The mutations also had no influence on the potency of morphine-6-glucuronide (M6G) and morphine-3-glucuronide (M3G). 5. We conclude that the hydrophilic side chain of Asn in position 230 is not involved in the formation of a H-bond with the aliphatic alcohol of morphine and that an enhancement of the potency of morphine and fentanyl can be explained by mutating this residue towards more hydrophobic amino acids.
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MESH Headings
- Analgesics, Opioid/pharmacology
- Animals
- Asparagine/agonists
- Asparagine/biosynthesis
- Asparagine/genetics
- Asparagine/physiology
- Binding Sites/physiology
- Dose-Response Relationship, Drug
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-/pharmacology
- Female
- G Protein-Coupled Inwardly-Rectifying Potassium Channels
- Humans
- Membrane Potentials/drug effects
- Membrane Potentials/physiology
- Mice
- Mutation/physiology
- Potassium Channels/biosynthesis
- Potassium Channels, Inwardly Rectifying
- RGS Proteins/biosynthesis
- Rats
- Receptors, Opioid, mu/agonists
- Receptors, Opioid, mu/biosynthesis
- Receptors, Opioid, mu/physiology
- Xenopus
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Affiliation(s)
- Joost Pil
- Laboratory of Toxicology, Faculty of Pharmaceutical Sciences, University of Leuven, Van Evenstraat 4, B-3000 Leuven, Belgium
| | - Jan Tytgat
- Laboratory of Toxicology, Faculty of Pharmaceutical Sciences, University of Leuven, Van Evenstraat 4, B-3000 Leuven, Belgium
- Author for correspondence:
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30
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Chavkin C, McLaughlin JP, Celver JP. Regulation of opioid receptor function by chronic agonist exposure: constitutive activity and desensitization. Mol Pharmacol 2001; 60:20-5. [PMID: 11408596 DOI: 10.1124/mol.60.1.20] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- C Chavkin
- Department of Pharmacology, University of Washington, Seattle, Washington 98195-7280, USA.
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31
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Protein kinase C-mediated inhibition of mu-opioid receptor internalization and its involvement in the development of acute tolerance to peripheral mu-agonist analgesia. J Neurosci 2001. [PMID: 11312280 DOI: 10.1523/jneurosci.21-09-02967.2001] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We investigated the role of protein kinase C (PKC) in cell mu-opioid receptor (MOR) internalization and MOR-mediated acute tolerance in vivo. When Chinese hamster ovary cells expressing MOR were exposed to [D-Ala(2),MePhe(4),Gly-ol(5)]-enkephalin (DAMGO), receptor internalization was observed at 30 min. Incubation with morphine failed to induce receptor internalization. When calphostin C, a PKC inhibitor, was added, receptor internalization was observed as early as 10 min after morphine stimulation. The MOR internalization induced by DAMGO or morphine in the presence of calphostin C was dynamin dependent, because it was abolished 2 d after pretreatment with recombinant adenovirus to express a dominant interfering dynamin mutant (K44A/dynamin adenovirus). On the other hand, in a peripheral nociception test in mice, the nociceptive flexor response after intraplantar injection (i.pl.) of bradykinin was markedly inhibited by DAMGO (i.pl.). DAMGO analgesia was not affected by 2 hr prior injection (i.pl.) of DAMGO. Marked acute tolerance was observed after pretreatment with dynamin antisense oligodeoxynucleotide or K44A/dynamin adenovirus. The DAMGO-induced acute tolerance under such pretreatments was inhibited by calphostin C. Together, these findings suggest that PKC desensitizes MOR or has a role in the development of acute tolerance through MOR by inhibiting internalization mechanisms as a resensitization process.
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32
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Wilson MH, Highfield HA, Limbird LE. The role of a conserved inter-transmembrane domain interface in regulating alpha(2a)-adrenergic receptor conformational stability and cell-surface turnover. Mol Pharmacol 2001; 59:929-38. [PMID: 11259639 DOI: 10.1124/mol.59.4.929] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Functional and structural data from G protein-coupled receptors (GPCR) predict that transmembrane-domain (TM)2 is adjacent to TM7 within the GPCR structure, and that within this interface a conserved aspartate in TM2 and a conserved asparagine in TM7 exist in close proximity. Mutation at this D79(TM2)-N422(TM7) interface in the alpha(2A)-adrenergic receptor (alpha(2A)AR) affects not only receptor activation but also cell-surface residence time and conformational stability. Mutation at TM2(D79N) reduces allosteric modulation by Na(+) and receptor activation more dramatically than affecting cell-surface receptor turnover and conformational stability, whereas mutation at TM7(N422D) creates profound conformational instability and more rapid degradation of receptor from the surface of cells despite receptor activation and allosteric modulation properties that mirror a wild-type receptor. Double mutation of TM2 and 7(D79N/N422D) reveals phenotypes for receptor activation and conformational stability intermediate between the wild-type and singly mutated alpha(2A)AR. Additionally, the structural placement of a negative charge at this TM2/TM7 interface is necessary but not sufficient for receptor structural stability, because mislocalization of the negative charge in either the D79E alpha(2A)AR (which extends the charge out one methylene group) or the D79N/N422D alpha(2A)AR (placing the charge in TM7 instead of TM2) results in conformational lability in detergent solution and more rapid cell-surface receptor clearance. These studies suggest that this interface is important in regulating receptor cell-surface residence time and conformational stability in addition to its previously recognized role in receptor activation.
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Affiliation(s)
- M H Wilson
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
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33
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Abstract
The cloning of the opioid receptors allows the investigation of receptor domains involved in the peptidic and nonpeptidic ligand interaction and activation of the opioid receptors. Receptor chimera studies and mutational analysis of the primary sequences of the opioid receptors have provided insights into the structural domains required for the ligand recognition and receptor activation. In the current review, we examine the current reports on the possible involvement of extracellular domains and transmembrane domains in the high-affinity binding of peptidic and nonpeptidic ligands to the opioid receptor. The structural requirement for the receptors' selectivity toward different ligands is discussed. The receptor domains involved in the activation and subsequent cellular regulation of the receptors' activities as determined by mutational analysis will also be discussed. Finally, the validity of the conclusions based on single amino acid mutations is examined.
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Affiliation(s)
- P Y Law
- Department of Pharmacology, University of Minnesota, Minneapolis 55455-0217, USA.
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34
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Galés C, Kowalski-Chauvel A, Dufour MN, Seva C, Moroder L, Pradayrol L, Vaysse N, Fourmy D, Silvente-Poirot S. Mutation of Asn-391 within the conserved NPXXY motif of the cholecystokinin B receptor abolishes Gq protein activation without affecting its association with the receptor. J Biol Chem 2000; 275:17321-7. [PMID: 10748160 DOI: 10.1074/jbc.m909801199] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Among the most conserved regions in the G-protein-coupled receptors is the (N/D)PX(2-3)Y motif of the seventh transmembrane domain (X represents any amino acid). The mutation of the Asn/Asp residue of this motif in different G-protein-coupled receptors was shown to affect the activation of either adenylyl cyclase or phospholipase C. We have mutated the Asn residue (Asn-391) of the NPXXY motif in the CCKBR to Ala and determined the effects of the mutation on binding, signaling, and G-proteins coupling after expression of the mutated receptor in COS cells. The mutated receptor displayed similar expression levels and high affinity CCK binding compared with the wild type CCKBR. However, unlike the wild type CCKBR, the mutated receptor was completely unable to mediate activation of either phospholipase C and protein kinase C-dependent and -independent mitogen-activated protein kinase pathways, indicating an essential role of Asn-391 in CCKBR signaling. Coimmunoprecipitation experiments allowed us to show that the inactive mutant retains an intact capacity to form stable complexes with G(q)alpha subunits in response to CCK. These results indicate that the formation of high affinity CCK-receptor-G(q) protein complexes is not sufficient to activate G(q) and suggest that Asn-391 is specifically involved in G(q) proteins activation.
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Affiliation(s)
- C Galés
- INSERM U 531, Institut Louis Bugnard, CHU Rangueil, Bat L3, 31403 Toulouse Cedex, France
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35
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Flanagan CA, Zhou W, Chi L, Yuen T, Rodic V, Robertson D, Johnson M, Holland P, Millar RP, Weinstein H, Mitchell R, Sealfon SC. The functional microdomain in transmembrane helices 2 and 7 regulates expression, activation, and coupling pathways of the gonadotropin-releasing hormone receptor. J Biol Chem 1999; 274:28880-6. [PMID: 10506131 DOI: 10.1074/jbc.274.41.28880] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Structural microdomains of G protein-coupled receptors (GPCRs) consist of spatially related side chains that mediate discrete functions. The conserved helix 2/helix 7 microdomain was identified because the gonadotropin-releasing hormone (GnRH) receptor appears to have interchanged the Asp(2.50) and Asn(7.49) residues which are conserved in transmembrane helices 2 and 7 of rhodopsin-like GPCRs. We now demonstrate that different side chains of this microdomain contribute specifically to receptor expression, heterotrimeric G protein-, and small G protein-mediated signaling. An Asn residue is required in position 2.50(87) for expression of the GnRH receptor at the cell surface, most likely through an interaction with the conserved Asn(1.50(53)) residue, which we also find is required for receptor expression. Most GPCRs require an Asp side chain at either the helix 2 or helix 7 locus of the microdomain for coupling to heterotrimeric G proteins, but the GnRH receptor has transferred the requirement for an acidic residue from helix 2 to 7. However, the presence of Asp at the helix 7 locus precludes small G protein-dependent coupling to phospholipase D. These results implicate specific components of the helix 2/helix 7 microdomain in receptor expression and in determining the ability of the receptor to adopt distinct activated conformations that are optimal for interaction with heterotrimeric and small G proteins.
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Affiliation(s)
- C A Flanagan
- Department of Neurology, Mount Sinai School of Medicine, New York, New York 10029, USA
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