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Mukhaleva E, Ma N, van der Velden WJC, Gogoshin G, Branciamore S, Bhattacharya S, Rodin AS, Vaidehi N. Bayesian network models identify cooperative GPCR:G protein interactions that contribute to G protein coupling. J Biol Chem 2024; 300:107362. [PMID: 38735478 PMCID: PMC11176750 DOI: 10.1016/j.jbc.2024.107362] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Revised: 05/03/2024] [Accepted: 05/04/2024] [Indexed: 05/14/2024] Open
Abstract
Cooperative interactions in protein-protein interfaces demonstrate the interdependency or the linked network-like behavior and their effect on the coupling of proteins. Cooperative interactions also could cause ripple or allosteric effects at a distance in protein-protein interfaces. Although they are critically important in protein-protein interfaces, it is challenging to determine which amino acid pair interactions are cooperative. In this work, we have used Bayesian network modeling, an interpretable machine learning method, combined with molecular dynamics trajectories to identify the residue pairs that show high cooperativity and their allosteric effect in the interface of G protein-coupled receptor (GPCR) complexes with Gα subunits. Our results reveal six GPCR:Gα contacts that are common to the different Gα subtypes and show strong cooperativity in the formation of interface. Both the C terminus helix5 and the core of the G protein are codependent entities and play an important role in GPCR coupling. We show that a promiscuous GPCR coupling to different Gα subtypes, makes all the GPCR:Gα contacts that are specific to each Gα subtype (Gαs, Gαi, and Gαq). This work underscores the potential of data-driven Bayesian network modeling in elucidating the intricate dependencies and selectivity determinants in GPCR:G protein complexes, offering valuable insights into the dynamic nature of these essential cellular signaling components.
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Affiliation(s)
- Elizaveta Mukhaleva
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, California, USA; Irell and Manella Graduate School of Biological Sciences, Beckman Research Institute of the City of Hope, Duarte, California, USA
| | - Ning Ma
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, California, USA
| | - Wijnand J C van der Velden
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, California, USA
| | - Grigoriy Gogoshin
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, California, USA
| | - Sergio Branciamore
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, California, USA; Irell and Manella Graduate School of Biological Sciences, Beckman Research Institute of the City of Hope, Duarte, California, USA.
| | - Supriyo Bhattacharya
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, California, USA.
| | - Andrei S Rodin
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, California, USA; Irell and Manella Graduate School of Biological Sciences, Beckman Research Institute of the City of Hope, Duarte, California, USA.
| | - Nagarajan Vaidehi
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, California, USA; Irell and Manella Graduate School of Biological Sciences, Beckman Research Institute of the City of Hope, Duarte, California, USA.
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2
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Han J, Zhang J, Nazarova AL, Bernhard SM, Krumm BE, Zhao L, Lam JH, Rangari VA, Majumdar S, Nichols DE, Katritch V, Yuan P, Fay JF, Che T. Ligand and G-protein selectivity in the κ-opioid receptor. Nature 2023; 617:417-425. [PMID: 37138078 PMCID: PMC10172140 DOI: 10.1038/s41586-023-06030-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2022] [Accepted: 03/29/2023] [Indexed: 05/05/2023]
Abstract
The κ-opioid receptor (KOR) represents a highly desirable therapeutic target for treating not only pain but also addiction and affective disorders1. However, the development of KOR analgesics has been hindered by the associated hallucinogenic side effects2. The initiation of KOR signalling requires the Gi/o-family proteins including the conventional (Gi1, Gi2, Gi3, GoA and GoB) and nonconventional (Gz and Gg) subtypes. How hallucinogens exert their actions through KOR and how KOR determines G-protein subtype selectivity are not well understood. Here we determined the active-state structures of KOR in a complex with multiple G-protein heterotrimers-Gi1, GoA, Gz and Gg-using cryo-electron microscopy. The KOR-G-protein complexes are bound to hallucinogenic salvinorins or highly selective KOR agonists. Comparisons of these structures reveal molecular determinants critical for KOR-G-protein interactions as well as key elements governing Gi/o-family subtype selectivity and KOR ligand selectivity. Furthermore, the four G-protein subtypes display an intrinsically different binding affinity and allosteric activity on agonist binding at KOR. These results provide insights into the actions of opioids and G-protein-coupling specificity at KOR and establish a foundation to examine the therapeutic potential of pathway-selective agonists of KOR.
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Affiliation(s)
- Jianming Han
- Department of Anesthesiology, Washington University in St Louis, St Louis, MO, USA
- Center for Clinical Pharmacology, University of Health Sciences and Pharmacy in St Louis and Washington University School of Medicine, St Louis, MO, USA
| | - Jingying Zhang
- Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St Louis, MO, USA
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Antonina L Nazarova
- Department of Quantitative and Computational Biology, University of Southern California, Los Angeles, CA, USA
- Department of Chemistry, University of Southern California, Los Angeles, CA, USA
- Center for New Technologies in Drug Discovery and Development, Bridge Institute, Michelson Center for Convergent Biosciences, University of Southern California, Los Angeles, CA, USA
| | - Sarah M Bernhard
- Department of Anesthesiology, Washington University in St Louis, St Louis, MO, USA
- Center for Clinical Pharmacology, University of Health Sciences and Pharmacy in St Louis and Washington University School of Medicine, St Louis, MO, USA
| | - Brian E Krumm
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, NC, USA
| | - Lei Zhao
- Department of Anesthesiology, Washington University in St Louis, St Louis, MO, USA
| | - Jordy Homing Lam
- Department of Quantitative and Computational Biology, University of Southern California, Los Angeles, CA, USA
- Department of Chemistry, University of Southern California, Los Angeles, CA, USA
- Center for New Technologies in Drug Discovery and Development, Bridge Institute, Michelson Center for Convergent Biosciences, University of Southern California, Los Angeles, CA, USA
| | - Vipin A Rangari
- Center for Clinical Pharmacology, University of Health Sciences and Pharmacy in St Louis and Washington University School of Medicine, St Louis, MO, USA
| | - Susruta Majumdar
- Department of Anesthesiology, Washington University in St Louis, St Louis, MO, USA
- Center for Clinical Pharmacology, University of Health Sciences and Pharmacy in St Louis and Washington University School of Medicine, St Louis, MO, USA
- Washington University Pain Center, Washington University in St Louis, St Louis, MO, USA
| | - David E Nichols
- Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, NC, USA
| | - Vsevolod Katritch
- Department of Quantitative and Computational Biology, University of Southern California, Los Angeles, CA, USA
- Department of Chemistry, University of Southern California, Los Angeles, CA, USA
- Center for New Technologies in Drug Discovery and Development, Bridge Institute, Michelson Center for Convergent Biosciences, University of Southern California, Los Angeles, CA, USA
| | - Peng Yuan
- Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St Louis, MO, USA
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Jonathan F Fay
- Department of Biochemistry and Molecular Biology, University of Maryland Baltimore, Baltimore, MD, USA.
| | - Tao Che
- Department of Anesthesiology, Washington University in St Louis, St Louis, MO, USA.
- Center for Clinical Pharmacology, University of Health Sciences and Pharmacy in St Louis and Washington University School of Medicine, St Louis, MO, USA.
- Washington University Pain Center, Washington University in St Louis, St Louis, MO, USA.
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3
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Gaitonde SA, Bouvier M. Enhanced Bystander BRET (ebBRET) Biosensors as Biophysical Tools to Map the Signaling Profile of Neuropsychiatric Drugs Targeting GPCRs. Methods Mol Biol 2023; 2687:15-30. [PMID: 37464159 DOI: 10.1007/978-1-0716-3307-6_2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/20/2023]
Abstract
Bioluminescence resonance energy transfer (BRET) is a non-radiative energy transfer between a bioluminescent donor and a fluorescent acceptor with far-reaching applications in detecting physiologically relevant protein-protein interactions. The recently developed enhanced bystander BRET (ebBRET) biosensors have made it possible to rapidly determine the signaling profile of a series of ligands across a large number of GPCRs and their signaling repertoires, which has tremendous implications in the drug discovery process. Here we describe BRET and the ebBRET biosensors as investigational tools in establishing functional selectivity downstream of GPCRs.
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Affiliation(s)
- Supriya A Gaitonde
- Department of Biochemistry and Molecular Medicine, Institute for Research in Immunology and Cancer (IRIC), Université de Montréal, Montréal, QC, Canada.
| | - Michel Bouvier
- Department of Biochemistry and Molecular Medicine, Institute for Research in Immunology and Cancer (IRIC), Université de Montréal, Montréal, QC, Canada
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4
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Sandhu M, Cho A, Ma N, Mukhaleva E, Namkung Y, Lee S, Ghosh S, Lee JH, Gloriam DE, Laporte SA, Babu MM, Vaidehi N. Dynamic spatiotemporal determinants modulate GPCR:G protein coupling selectivity and promiscuity. Nat Commun 2022; 13:7428. [PMID: 36460632 PMCID: PMC9718833 DOI: 10.1038/s41467-022-34055-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Accepted: 10/11/2022] [Indexed: 12/03/2022] Open
Abstract
Recent studies have shown that G protein coupled receptors (GPCRs) show selective and promiscuous coupling to different Gα protein subfamilies and yet the mechanisms of the range of coupling preferences remain unclear. Here, we use Molecular Dynamics (MD) simulations on ten GPCR:G protein complexes and show that the location (spatial) and duration (temporal) of intermolecular contacts at the GPCR:Gα protein interface play a critical role in how GPCRs selectively interact with G proteins. We identify that some GPCR:G protein interface contacts are common across Gα subfamilies and others specific to Gα subfamilies. Using large scale data analysis techniques on the MD simulation snapshots we derive a spatio-temporal code for contacts that confer G protein selective coupling and validated these contacts using G protein activation BRET assays. Our results demonstrate that promiscuous GPCRs show persistent sampling of the common contacts more than G protein specific contacts. These findings suggest that GPCRs maintain contact with G proteins through a common central interface, while the selectivity comes from G protein specific contacts at the periphery of the interface.
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Affiliation(s)
- Manbir Sandhu
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, CA, 91010, USA.
- Department of Structural Biology, Center for Data Driven Discovery, St. Jude Children's Research Hospital, Memphis, TN, 38105, USA.
| | - Aaron Cho
- Department of Medicine, Research Institute of the McGill University Health Centre, Montreal, QC, H4A 3J1, Canada
| | - Ning Ma
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, CA, 91010, USA
| | - Elizaveta Mukhaleva
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, CA, 91010, USA
- Irell and Manella Graduate School of Biological Sciences, Beckman Research Institute of the City of Hope, Duarte, CA, 91010, USA
| | - Yoon Namkung
- Department of Medicine, Research Institute of the McGill University Health Centre, Montreal, QC, H4A 3J1, Canada
| | - Sangbae Lee
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, CA, 91010, USA
| | - Soumadwip Ghosh
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, CA, 91010, USA
| | - John H Lee
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, CA, 91010, USA
| | - David E Gloriam
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100, Copenhagen, Denmark
| | - Stéphane A Laporte
- Department of Medicine, Research Institute of the McGill University Health Centre, Montreal, QC, H4A 3J1, Canada
- Department of Pharmacology and Therapeutics, McGill University, Montréal, QC, H3G 1Y6, Canada
| | - M Madan Babu
- Department of Structural Biology, Center for Data Driven Discovery, St. Jude Children's Research Hospital, Memphis, TN, 38105, USA.
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH, UK.
| | - Nagarajan Vaidehi
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, CA, 91010, USA.
- Irell and Manella Graduate School of Biological Sciences, Beckman Research Institute of the City of Hope, Duarte, CA, 91010, USA.
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Distinct In Vitro Binding Profile of the Somatostatin Receptor Subtype 2 Antagonist [ 177Lu]Lu-OPS201 Compared to the Agonist [ 177Lu]Lu-DOTA-TATE. Pharmaceuticals (Basel) 2021; 14:ph14121265. [PMID: 34959665 PMCID: PMC8706879 DOI: 10.3390/ph14121265] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Revised: 12/01/2021] [Accepted: 12/02/2021] [Indexed: 01/14/2023] Open
Abstract
Treatment of neuroendocrine tumours with the radiolabelled somatostatin receptor subtype 2 (SST2) peptide agonist [177Lu]Lu-DOTA-TATE is effective and well-established. Recent studies suggest improved therapeutic efficacy using the SST2 peptide antagonist [177Lu]Lu-OPS201. However, little is known about the cellular mechanisms that lead to the observed differences. In the present in vitro study, we compared kinetic binding, saturation binding, competition binding, cellular uptake and release of [177Lu]Lu-OPS201 versus [177Lu]Lu-DOTA-TATE using HEK cells stably transfected with the human SST2. While [177Lu]Lu-OPS201 and [177Lu]Lu-DOTA-TATE exhibited comparable affinity (KD, 0.15 ± 0.003 and 0.08 ± 0.02 nM, respectively), [177Lu]Lu-OPS201 recognized four times more binding sites than [177Lu]Lu-DOTA-TATE. Competition assays demonstrated that a high concentration of the agonist displaced only 30% of [177Lu]Lu-OPS201 bound to HEK-SST2 cell membranes; an indication that the antagonist binds to additional sites that are not recognized by the agonist. [177Lu]Lu-OPS201 showed faster association and slower dissociation than [177Lu]Lu-DOTA-TATE. Whereas most of [177Lu]Lu-OPS201 remained at the cell surface, [177Lu]Lu-DOTA-TATE was almost completely internalised inside the cell. The present data identified distinct differences between [177Lu]Lu-OPS201 and [177Lu]Lu-DOTA-TATE regarding the recognition of receptor binding sites (higher for [177Lu]Lu-OPS201) and their kinetics (faster association and slower dissociation of [177Lu]Lu-OPS201) that explain, to a great extent, the improved therapeutic efficacy of [177Lu]Lu-OPS201 compared to [177Lu]Lu-DOTA-TATE.
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6
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Fusion with Promiscuous Gα 16 Subunit Reveals Signaling Bias at Muscarinic Receptors. Int J Mol Sci 2021; 22:ijms221810089. [PMID: 34576254 PMCID: PMC8469978 DOI: 10.3390/ijms221810089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 09/06/2021] [Accepted: 09/14/2021] [Indexed: 11/25/2022] Open
Abstract
A complex evaluation of agonist bias at G-protein coupled receptors at the level of G-protein classes and isoforms including non-preferential ones is essential for advanced agonist screening and drug development. Molecular crosstalk in downstream signaling and a lack of sufficiently sensitive and selective methods to study direct coupling with G-protein of interest complicates this analysis. We performed binding and functional analysis of 11 structurally different agonists on prepared fusion proteins of individual subtypes of muscarinic receptors and non-canonical promiscuous α-subunit of G16 protein to study agonist bias. We have demonstrated that fusion of muscarinic receptors with Gα16 limits access of other competitive Gα subunits to the receptor, and thus enables us to study activation of Gα16 mediated pathway more specifically. Our data demonstrated agonist-specific activation of G16 pathway among individual subtypes of muscarinic receptors and revealed signaling bias of oxotremorine towards Gα16 pathway at the M2 receptor and at the same time impaired Gα16 signaling of iperoxo at M5 receptors. Our data have shown that fusion proteins of muscarinic receptors with α-subunit of G-proteins can serve as a suitable tool for studying agonist bias, especially at non-preferential pathways.
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7
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Rogliani P, Matera MG, Facciolo F, Page C, Cazzola M, Calzetta L. Beclomethasone dipropionate, formoterol fumarate and glycopyrronium bromide: Synergy of triple combination therapy on human airway smooth muscle ex vivo. Br J Pharmacol 2020; 177:1150-1163. [PMID: 31660611 DOI: 10.1111/bph.14909] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Revised: 10/11/2019] [Accepted: 10/12/2019] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND AND PURPOSE Combining inhaled corticosteroids (ICSs), long-acting β2 -adrenoceptor agonists (LABAs) and long-acting muscarinic antagonists (LAMAs) is recommended to treat severe forms of asthma and chronic obstructive pulmonary disease (COPD). Clinical benefits have been demonstrated for ICS/LABA/LAMA combinations. This study characterized the interaction between the ICS beclomethasone dipropionate, the LABA formoterol fumarate and the LAMA glycopyrronium bromide in human airways. EXPERIMENTAL APPROACH Human passively sensitized airways and bronchi from COPD donors were stimulated with histamine or carbachol. Tissues were incubated overnight with beclomethasone and then treated with formoterol and glycopyrronium, alone or in triple combination. The interaction was assessed by using Bliss Independence and Unified Theory theorems. KEY RESULTS Beclomethasone/formoterol/glycopyrronium combination synergistically relaxed medium bronchi and small airways. Beclomethasone/formoterol/glycopyrronium combination at 100:6:12.5 combination ratio was a balanced drug mixture leading to very strong synergistic effect on relaxation of medium bronchi (Combination Index: from 0.042 to 0.96) and middle to very strong synergy in small airways (Combination Index: from 0.018 to 0.310). The synergy was related with the activation of intracellular glucocorticoid receptors and Gsα subunit G-protein of β2 -adrenoceptors, leading to the modulation of cyclic AMP-dependent PKA pathway. CONCLUSION Triple beclomethasone/formoterol/glycopyrronium combination induces synergistic bronchorelaxant effect in medium and small human airways, at least in ex vivo experiments. Further research is needed to confirm these findings in clinical studies in patients with asthma or COPD.
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Affiliation(s)
- Paola Rogliani
- Unit of Respiratory Medicine, Department of Experimental Medicine, University of Rome "Tor Vergata", Rome, Italy
| | - Maria Gabriella Matera
- Unit of Pharmacology, Department of Experimental Medicine, University of Campania "Luigi Vanvitelli", Naples, Italy
| | - Francesco Facciolo
- Thoracic Surgery Unit, Regina Elena National Cancer Institute, Rome, Italy
| | - Clive Page
- Sackler Institute of Pulmonary Pharmacology, Institute of Pharmaceutical Science, King's College London, London, UK
| | - Mario Cazzola
- Unit of Respiratory Medicine, Department of Experimental Medicine, University of Rome "Tor Vergata", Rome, Italy
| | - Luigino Calzetta
- Unit of Respiratory Medicine, Department of Experimental Medicine, University of Rome "Tor Vergata", Rome, Italy
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8
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Crespo M, León‐Navarro DA, Ruíz MÁ, Martín M. Hyperthermia‐induced seizures produce long‐term effects on the functionality of adenosine A
1
receptor in rat cerebral cortex. Int J Dev Neurosci 2020; 80:1-12. [DOI: 10.1002/jdn.10000] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Accepted: 12/09/2019] [Indexed: 12/12/2022] Open
Affiliation(s)
- María Crespo
- Departamento de Química Inorgánica Orgánica y Bioquímica Facultad de Ciencias y Tecnologías Químicas Centro Regional de Investigaciones Biomédicas Universidad de Castilla‐La Mancha Ciudad Real Spain
| | - David Agustín León‐Navarro
- Departamento de Química Inorgánica Orgánica y Bioquímica Facultad de Ciencias y Tecnologías Químicas Centro Regional de Investigaciones Biomédicas Universidad de Castilla‐La Mancha Ciudad Real Spain
| | - María Ángeles Ruíz
- Departamento de Química Inorgánica Orgánica y Bioquímica Facultad de Ciencias y Tecnologías Químicas Centro Regional de Investigaciones Biomédicas Universidad de Castilla‐La Mancha Ciudad Real Spain
| | - Mairena Martín
- Departamento de Química Inorgánica Orgánica y Bioquímica Facultad de Ciencias y Tecnologías Químicas Facultad de Medicina de Ciudad Real Centro Regional de Investigaciones Biomédicas Universidad de Castilla‐La Mancha Ciudad Real Spain
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9
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Latif R, Morshed SA, Ma R, Tokat B, Mezei M, Davies TF. A Gq Biased Small Molecule Active at the TSH Receptor. Front Endocrinol (Lausanne) 2020; 11:372. [PMID: 32676053 PMCID: PMC7333667 DOI: 10.3389/fendo.2020.00372] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 05/11/2020] [Indexed: 11/13/2022] Open
Abstract
G protein coupled receptors (GPCRs) can lead to G protein and non-G protein initiated signals. By virtue of its structural property, the TSH receptor (TSHR) has a unique ability to engage different G proteins making it highly amenable to selective signaling. In this study, we describe the identification and characterization of a novel small molecule agonist to the TSHR which induces primary engagement with Gαq/11. To identify allosteric modulators inducing selective signaling of the TSHR we used a transcriptional-based luciferase assay system with CHO-TSHR cells stably expressing response elements (CRE, NFAT, SRF, or SRE) that were capable of measuring signals emanating from the coupling of Gαs , Gαq/11, Gβγ, and Gα12/13, respectively. Using this system, TSH activated Gαs , Gαq/11, and Gα12/13 but not Gβγ. On screening a library of 50K molecules at 0.1,1.0 and 10 μM, we identified a novel Gq/11 agonist (named MSq1) which activated Gq/11 mediated NFAT-luciferase >4 fold above baseline and had an EC50= 8.3 × 10-9 M with only minor induction of Gαs and cAMP. Furthermore, MSq1 is chemically and structurally distinct from any of the previously reported TSHR agonist molecules. Docking studies using a TSHR transmembrane domain (TMD) model indicated that MSq1 had contact points on helices H1, H2, H3, and H7 in the hydrophobic pocket of the TMD and also with the extracellular loops. On co-treatment with TSH, MSq1 suppressed TSH-induced proliferation of thyrocytes in a dose-dependent manner but lacked the intrinsic ability to influence basal thyrocyte proliferation. This unexpected inhibitory property of MSq1 could be blocked in the presence of a PKC inhibitor resulting in derepressing TSH induced protein kinase A (PKA) signals and resulting in the induction of proliferation. Thus, the inhibitory effect of MSq1 on proliferation resided in its capacity to overtly activate protein kinase C (PKC) which in turn suppressed the proliferative signal induced by activation of the predomiant cAMP-PKA pathway of the TSHR. Treatment of rat thyroid cells (FRTL5) with MSq1 did not show any upregulation of gene expression of the key thyroid specific markers such as thyroglobulin(Tg), thyroid peroxidase (Tpo), sodium iodide symporter (Nis), and the TSH receptor (Tshr) further suggesting lack of involvement of MSq1 and Gαq/11 activation with cellular differentation. In summary, we identified and characterized a novel Gαq/11 agonist molecule acting at the TSHR and which showed a marked anti-proliferative ability. Hence, Gq biased activation of the TSHR is capable of ameliorating the proliferative signals from its orthosteric ligand and may offer a therapeutic option for thyroid growth modulation.
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Affiliation(s)
- Rauf Latif
- Thyroid Research Unit, Icahn School of Medicine at Mount Sinai, New York, NY, United States
- James J. Peters VA Medical Center, New York, NY, United States
- *Correspondence: Rauf Latif
| | - Syed A. Morshed
- Thyroid Research Unit, Icahn School of Medicine at Mount Sinai, New York, NY, United States
- James J. Peters VA Medical Center, New York, NY, United States
| | - Risheng Ma
- Thyroid Research Unit, Icahn School of Medicine at Mount Sinai, New York, NY, United States
- James J. Peters VA Medical Center, New York, NY, United States
| | - Bengu Tokat
- Thyroid Research Unit, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Mihaly Mezei
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Terry F. Davies
- Thyroid Research Unit, Icahn School of Medicine at Mount Sinai, New York, NY, United States
- James J. Peters VA Medical Center, New York, NY, United States
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10
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Link R, Veiksina S, Tahk MJ, Laasfeld T, Paiste P, Kopanchuk S, Rinken A. The constitutive activity of melanocortin-4 receptors in cAMP pathway is allosterically modulated by zinc and copper ions. J Neurochem 2019; 153:346-361. [PMID: 31792980 DOI: 10.1111/jnc.14933] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2019] [Revised: 11/06/2019] [Accepted: 11/29/2019] [Indexed: 01/25/2023]
Abstract
Melanocortin-4 receptors (MC4 R) are unique among G-protein-coupled receptors (GPCRs) as they have endogenous ligands that can exhibit inverse agonistic properties in the case of elevated basal activity. It is known that the constitutive activity of GPCRs strongly affects the ligand-dependent physiological responses, but little is known about these regulatory mechanisms. Since several metal ions have been shown to be important modulators of the signal transduction of GPCRs, we hypothesized that metal ions regulate the basal activity of MC4 Rs. Implementation of a fluorescence anisotropy assay and novel redshifted fluorescent peptides enabled kinetic characterization of ligand binding to MC4 R expressed on budded baculoviruses. We show that Ca2+ is required for high-affinity ligand binding, but Zn2+ and Cu2+ in the presence of Ca2+ behave as negative allosteric modulators of ligand binding to MC4 R. FRET-based cAMP biosensor was used to measure the activation of MC4 R stably expressed in CHO-K1 cells. At low micromolar concentrations, Zn2+ caused MC4 R-dependent activation of the cAMP pathway, whereas Cu2+ reduced the activity of MC4 R even below the basal level. These findings indicate that at physiologically relevant concentrations can Zn2+ and Cu2+ function as MC4 R agonists or inverse agonists, respectively. This means that depending on the level of constitutive activity induced by Zn2+ ions, the pharmacological effect of orthosteric ligands of MC4 R can be switched from a partial to an inverse agonist. OPEN SCIENCE BADGES: This article has received a badge for *Open Materials* because it provided all relevant information to reproduce the study in the manuscript. More information about the Open Science badges can be found at https://cos.io/our-services/open-science-badges/.
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Affiliation(s)
- Reet Link
- Institute of Chemistry, University of Tartu, Tartu, Estonia
| | - Santa Veiksina
- Institute of Chemistry, University of Tartu, Tartu, Estonia
| | | | - Tõnis Laasfeld
- Institute of Chemistry, University of Tartu, Tartu, Estonia
| | - Päärn Paiste
- Department of Geology, University of Tartu, Tartu, Estonia
| | | | - Ago Rinken
- Institute of Chemistry, University of Tartu, Tartu, Estonia
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11
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Sandhu M, Touma AM, Dysthe M, Sadler F, Sivaramakrishnan S, Vaidehi N. Conformational plasticity of the intracellular cavity of GPCR-G-protein complexes leads to G-protein promiscuity and selectivity. Proc Natl Acad Sci U S A 2019; 116:11956-11965. [PMID: 31138704 PMCID: PMC6575595 DOI: 10.1073/pnas.1820944116] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
While the dynamics of the intracellular surface in agonist-stimulated GPCRs is well studied, the impact of GPCR dynamics on G-protein selectivity remains unclear. Here, we combine molecular dynamics simulations with live-cell FRET and secondary messenger measurements, for 21 GPCR-G-protein combinations, to advance a dynamic model of the GPCR-G-protein interface. Our data show C terminus peptides of Gαs, Gαi, and Gαq proteins assume a small ensemble of unique orientations when coupled to their cognate GPCRs, similar to the variations observed in 3D structures of GPCR-G-protein complexes. The noncognate G proteins interface with latent intracellular GPCR cavities but dissociate due to weak and unstable interactions. Three predicted mutations in β2-adrenergic receptor stabilize binding of noncognate Gαq protein in its latent cavity, allowing promiscuous signaling through both Gαs and Gαq in a dose-dependent manner. This demonstrates that latent GPCR cavities can be evolved, by design or nature, to tune G-protein selectivity, giving insights to pluridimensional GPCR signaling.
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Affiliation(s)
- Manbir Sandhu
- Irell & Manella Graduate School of Biological Sciences, Beckman Research Institute of the City of Hope, Duarte, CA 91010
- Department of Computational & Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, CA 91010
| | - Anja M Touma
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Twin Cities, Minneapolis, MN 55455
| | - Matthew Dysthe
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Twin Cities, Minneapolis, MN 55455
| | - Fredrik Sadler
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Twin Cities, Minneapolis, MN 55455
| | - Sivaraj Sivaramakrishnan
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Twin Cities, Minneapolis, MN 55455
| | - Nagarajan Vaidehi
- Irell & Manella Graduate School of Biological Sciences, Beckman Research Institute of the City of Hope, Duarte, CA 91010;
- Department of Computational & Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, CA 91010
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12
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Seyedabadi M, Ghahremani MH, Albert PR. Biased signaling of G protein coupled receptors (GPCRs): Molecular determinants of GPCR/transducer selectivity and therapeutic potential. Pharmacol Ther 2019; 200:148-178. [PMID: 31075355 DOI: 10.1016/j.pharmthera.2019.05.006] [Citation(s) in RCA: 88] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Accepted: 04/26/2019] [Indexed: 02/07/2023]
Abstract
G protein coupled receptors (GPCRs) convey signals across membranes via interaction with G proteins. Originally, an individual GPCR was thought to signal through one G protein family, comprising cognate G proteins that mediate canonical receptor signaling. However, several deviations from canonical signaling pathways for GPCRs have been described. It is now clear that GPCRs can engage with multiple G proteins and the line between cognate and non-cognate signaling is increasingly blurred. Furthermore, GPCRs couple to non-G protein transducers, including β-arrestins or other scaffold proteins, to initiate additional signaling cascades. Receptor/transducer selectivity is dictated by agonist-induced receptor conformations as well as by collateral factors. In particular, ligands stabilize distinct receptor conformations to preferentially activate certain pathways, designated 'biased signaling'. In this regard, receptor sequence alignment and mutagenesis have helped to identify key receptor domains for receptor/transducer specificity. Furthermore, molecular structures of GPCRs bound to different ligands or transducers have provided detailed insights into mechanisms of coupling selectivity. However, receptor dimerization, compartmentalization, and trafficking, receptor-transducer-effector stoichiometry, and ligand residence and exposure times can each affect GPCR coupling. Extrinsic factors including cell type or assay conditions can also influence receptor signaling. Understanding these factors may lead to the development of improved biased ligands with the potential to enhance therapeutic benefit, while minimizing adverse effects. In this review, evidence for ligand-specific GPCR signaling toward different transducers or pathways is elaborated. Furthermore, molecular determinants of biased signaling toward these pathways and relevant examples of the potential clinical benefits and pitfalls of biased ligands are discussed.
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Affiliation(s)
- Mohammad Seyedabadi
- Department of Pharmacology, School of Medicine, Bushehr University of Medical Sciences, Iran; Education Development Center, Bushehr University of Medical Sciences, Iran
| | | | - Paul R Albert
- Ottawa Hospital Research Institute, Neuroscience, University of Ottawa, Canada.
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13
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Aiba I, Noebels JL. Adrenergic agonist induces rhythmic firing in quiescent cardiac preganglionic neurons in nucleus ambiguous via activation of intrinsic membrane excitability. J Neurophysiol 2019; 121:1266-1278. [PMID: 30699052 PMCID: PMC6485744 DOI: 10.1152/jn.00761.2018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Cholinergic vagal nerves projecting from neurons in the brain stem nucleus ambiguus (NAm) play a predominant role in cardiac parasympathetic pacemaking control. Central adrenergic signaling modulates the tone of this vagal output; however, the exact excitability mechanisms are not fully understood. We investigated responses of NAm neurons to adrenergic agonists using in vitro mouse brain stem slices. Preganglionic NAm neurons were identified by ChAT-tdTomato fluorescence in young adult transgenic mice, and their cardiac projection was confirmed by retrograde dye tracing. Juxtacellular recordings detected sparse or absent spontaneous action potentials (AP) in NAm neurons. However, bath application of epinephrine or norepinephrine strongly and reversibly activated most NAm neurons regardless of their basal firing rate. Epinephrine was more potent than norepinephrine, and this activation largely depends on α1-adrenoceptors. Interestingly, adrenergic activation of NAm neurons does not require an ionotropic synaptic mechanism, because postsynaptic excitatory or inhibitory receptor blockade did not occlude the excitatory effect, and bath-applied adrenergic agonists did not alter excitatory or inhibitory synaptic transmission. Instead, adrenergic agonists significantly elevated intrinsic membrane excitability to facilitate generation of recurrent action potentials. T-type calcium current and hyperpolarization-activated current are involved in this excitation pattern, although not required for spontaneous AP induction by epinephrine. In contrast, pharmacological blockade of persistent sodium current significantly inhibited the adrenergic effects. Our results demonstrate that central adrenergic signaling enhances the intrinsic excitability of NAm neurons and that persistent sodium current is required for this effect. This central balancing mechanism may counteract excessive peripheral cardiac excitation during increased sympathetic tone. NEW & NOTEWORTHY Cardiac preganglionic cholinergic neurons in the nucleus ambiguus (NAm) are responsible for slowing cardiac pacemaking. This study identified that adrenergic agonists can induce rhythmic action potentials in otherwise quiescent cholinergic NAm preganglionic neurons in brain stem slice preparation. The modulatory influence of adrenaline on central parasympathetic outflow may contribute to both physiological and deleterious cardiovascular regulation.
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Affiliation(s)
- Isamu Aiba
- Department of Neurology, Baylor College of Medicine , Houston, Texas
| | - Jeffrey L Noebels
- Department of Neurology, Baylor College of Medicine , Houston, Texas
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14
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Gao ZG, Inoue A, Jacobson KA. On the G protein-coupling selectivity of the native A 2B adenosine receptor. Biochem Pharmacol 2018; 151:201-213. [PMID: 29225130 PMCID: PMC5899946 DOI: 10.1016/j.bcp.2017.12.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Accepted: 12/05/2017] [Indexed: 12/14/2022]
Abstract
A2B adenosine receptor (A2BAR) activation induces Gs-dependent cyclic AMP accumulation. However, A2BAR G protein-coupling to other signaling events, e.g. ERK1/2 and calcium, is not well documented. We explored Gi, Gq/11 and Gs coupling in 1321 N1 astrocytoma, HEK293, and T24 bladder cancer cells endogenously expressing human A2BAR, using NECA or nonnucleoside BAY60-6583 as agonist, selective Gi, Gs and Gq/11 blockers, and CRISPR/Cas9-based Gq- and Gs-null HEK293 cells. In HEK293 cells, A2BAR-mediated ERK1/2 activity occurred via both Gi and Gs, but not Gq/11. However, HEK293 cell calcium mobilization was completely blocked by Gq/11 inhibitor UBO-QIC and by Gq/11 knockout. In T24 cells, Gi was solely responsible for A2BAR-mediated ERK1/2 stimulation, and Gs suppressed ERK1/2 activity. A2BAR-mediated intracellular calcium mobilization in T24 cells was mainly via Gi, although Gs may also play a role, but Gq/11 is not involved. In 1321 N1 astrocytoma cells A2BAR activation suppressed rather than stimulated ERK1/2 activity. The ERK1/2 activity decrease was reversed by Gs downregulation using cholera toxin, but potentiated by Gi inhibitor pertussis toxin, and UBO-QIC had no effect. EPACs played an important role in A2BAR-mediated ERK1/2 signaling in all three cells. Thus, A2BAR may: couple to the same downstream pathway via different G proteins in different cell types; activate different downstream events via different G proteins in the same cell type; activate Gi and Gs, which have opposing or synergistic roles in different cell types/signaling pathways. The findings, relevant to drug discovery, address some reported controversial roles of A2BAR and could apply to signaling mechanisms in other GPCRs.
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Affiliation(s)
- Zhan-Guo Gao
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, NIDDK, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD 20892, USA.
| | - Asuka Inoue
- Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan
| | - Kenneth A Jacobson
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, NIDDK, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD 20892, USA.
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15
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Berndt-Paetz M, Herbst L, Weimann A, Gonsior A, Stolzenburg JU, Neuhaus J. Highly specific detection of muscarinic M3 receptor, G protein interaction and intracellular trafficking in human detrusor using Proximity Ligation Assay (PLA). Acta Histochem 2018; 120:329-339. [PMID: 29551457 DOI: 10.1016/j.acthis.2018.03.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2017] [Revised: 02/08/2018] [Accepted: 03/09/2018] [Indexed: 01/06/2023]
Abstract
PURPOSE Muscarinic acetylcholine receptors (mAChRs) regulate a number of important physiological functions. Alteration of mAChR expression or function has been associated in the etiology of several pathologies including functional bladder disorders (e.g bladder pain syndrome/interstitial cystitis - BPS/IC). In a previous study we found specific mAChR expression patterns associated with BPS/IC, while correlation between protein and gene expression was lacking. Posttranslational regulatory mechanisms, e.g. altered intracellular receptor trafficking, could explain those differences. In addition, alternative G protein (GP) coupling could add to the pathophysiology via modulation of muscarinic signaling. In our proof-of-principle study, we addressed these questions in situ. We established PLA in combination with confocal laserscanning microscopy (CLSM) and 3D object reconstruction for highly specific detection and analysis of muscarinic 3 receptors (M3), G protein (GP) coupling and intracellular trafficking in human detrusor samples. MATERIAL AND METHODS Paraffin sections of formalin-fixed bladder tissue (FFPE) of BPS/IC patients receiving transurethral biopsy were examined by Cy3-PLA for M3 expression, coupling of M3 to GPs (Gαq/11, Gαs, Gαi) and interaction of M3 with endocytic regulator proteins. Membranes were labeled with wheat germ agglutinin-Alexa Fluor®488, nuclei were stained with DAPI. Object density and co-localization were analyzed in 3D-reconstruction of high resolution confocal z-stacks. RESULTS Confocal image stack processing resulted in well demarcated objects. Calculated receptor densities correlated significantly with existing confocal expression data, while significantly improved specificity of M3 detection by PLA was verified using bladder tissue samples from transgenic mice. 50-60% of the M3 receptor complexes were plasma membrane associated in human bladder detrusor. Application of PLA for M3 and GPs allowed visualization of M3-GP interactions and revealed individual GP-subtype coupling patterns. Detection of M3 interactions with endocytic trafficking proteins by PLA resulted in object sizes correlating with well-documented vesicle sizes of the endocytosis pathway. CONCLUSION PLA enabled highly specific detection of M3 receptor expression, demonstration of M3/GP differential coupling and intracellular M3 trafficking in human detrusor smooth muscle cells. This new approach minimized background fluorescence and antibody cross-reactions resulting from single antibody application, and enhanced specificity due to the use of two primary antibodies. Use of subcellular markers allowed visualization of subcellular receptor location. PLA/CLSM allows analyses of muscarinic "receptor - G protein - promiscuity" and intracellular trafficking even in bladder paraffin sections and may give new insights into the etiology and pathology of BPS/IC.
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16
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Michel MC, Charlton SJ. Biased Agonism in Drug Discovery-Is It Too Soon to Choose a Path? Mol Pharmacol 2018; 93:259-265. [PMID: 29326242 DOI: 10.1124/mol.117.110890] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Accepted: 01/01/2018] [Indexed: 12/13/2022] Open
Abstract
A single receptor can activate multiple signaling pathways that have distinct or even opposite effects on cell function. Biased agonists stabilize receptor conformations preferentially stimulating one of these pathways, and therefore allow a more targeted modulation of cell function and treatment of disease. Dedicated development of biased agonists has led to promising drug candidates in clinical development, such as the G protein-biased µ opioid receptor agonist oliceridine. However, leveraging the theoretical potential of biased agonism for drug discovery faces several challenges. Some of these challenges are technical, such as techniques for quantitative analysis of bias and development of suitable screening assays; others are more fundamental, such as the need to robustly identify in a very early phase which cell type harbors the cellular target of the drug candidate, which signaling pathway leads to the desired therapeutic effect, and how these pathways may be modulated in the disease to be treated. We conclude that biased agonism has potential mainly in the treatment of conditions with a well-understood pathophysiology; in contrast, it may increase effort and commercial risk under circumstances where the pathophysiology has been less well defined, as is the case with many highly innovative treatments.
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Affiliation(s)
- Martin C Michel
- Department of Pharmacology, Johannes Gutenberg University, Mainz, Germany (M.C.M.); Department of Life Sciences, University of Nottingham, Nottingham, United Kingdom (S.J.C.); and Excellerate Biosciences Ltd., MediCity, Nottingham, United Kingdom (S.J.C.)
| | - Steven J Charlton
- Department of Pharmacology, Johannes Gutenberg University, Mainz, Germany (M.C.M.); Department of Life Sciences, University of Nottingham, Nottingham, United Kingdom (S.J.C.); and Excellerate Biosciences Ltd., MediCity, Nottingham, United Kingdom (S.J.C.)
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17
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Malik RU, Dysthe M, Ritt M, Sunahara RK, Sivaramakrishnan S. ER/K linked GPCR-G protein fusions systematically modulate second messenger response in cells. Sci Rep 2017; 7:7749. [PMID: 28798477 PMCID: PMC5552854 DOI: 10.1038/s41598-017-08029-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Accepted: 07/05/2017] [Indexed: 12/20/2022] Open
Abstract
FRET and BRET approaches are well established for detecting ligand induced GPCR-G protein interactions in cells. Currently, FRET/BRET assays rely on co-expression of GPCR and G protein, and hence depend on the stoichiometry and expression levels of the donor and acceptor probes. On the other hand, GPCR-G protein fusions have been used extensively to understand the selectivity of GPCR signaling pathways. However, the signaling properties of fusion proteins are not consistent across GPCRs. In this study, we describe and characterize novel sensors based on the Systematic Protein Affinity Strength Modulation (SPASM) technique. Sensors consist of a GPCR and G protein tethered by an ER/K linker flanked by FRET probes. SPASM sensors are tested for the β2-, α1-, and α2- adrenergic receptors, and adenosine type 1 receptor (A1R), tethered to Gαs-XL, Gαi2, or Gαq subunits. Agonist stimulation of β2-AR and α2-AR increases FRET signal comparable to co-expressed FRET/BRET sensors. SPASM sensors also retain signaling through the endogenous G protein milieu. Importantly, ER/K linker length systematically tunes the GPCR-G protein interaction, with consequent modulation of second messenger signaling for cognate interactions. SPASM GPCR sensors serve the dual purpose of detecting agonist-induced changes in GPCR-G protein interactions, and linking these changes to downstream signaling.
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Affiliation(s)
- Rabia U Malik
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Matthew Dysthe
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Michael Ritt
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Roger K Sunahara
- Department of Pharmacology, University of California, San Diego, La Jolla, CA, 92093, USA
| | - Sivaraj Sivaramakrishnan
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN, 55455, USA.
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18
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Rozier K, Bondarenko VE. Distinct physiological effects of β1- and β2-adrenoceptors in mouse ventricular myocytes: insights from a compartmentalized mathematical model. Am J Physiol Cell Physiol 2017; 312:C595-C623. [DOI: 10.1152/ajpcell.00273.2016] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Revised: 01/03/2017] [Accepted: 01/18/2017] [Indexed: 01/08/2023]
Abstract
The β1- and β2-adrenergic signaling systems play different roles in the functioning of cardiac cells. Experimental data show that the activation of the β1-adrenergic signaling system produces significant inotropic, lusitropic, and chronotropic effects in the heart, whereas the effects of the β2-adrenergic signaling system is less apparent. In this paper, a comprehensive compartmentalized experimentally based mathematical model of the combined β1- and β2-adrenergic signaling systems in mouse ventricular myocytes is developed to simulate the experimental findings and make testable predictions of the behavior of the cardiac cells under different physiological conditions. Simulations describe the dynamics of major signaling molecules in different subcellular compartments; kinetics and magnitudes of phosphorylation of ion channels, transporters, and Ca2+ handling proteins; modifications of action potential shape and duration; and [Ca2+]i and [Na+]i dynamics upon stimulation of β1- and β2-adrenergic receptors (β1- and β2-ARs). The model reveals physiological conditions when β2-ARs do not produce significant physiological effects and when their effects can be measured experimentally. Simulations demonstrated that stimulation of β2-ARs with isoproterenol caused a marked increase in the magnitude of the L-type Ca2+ current, [Ca2+]i transient, and phosphorylation of phospholamban only upon additional application of pertussis toxin or inhibition of phosphodiesterases of type 3 and 4. The model also made testable predictions of the changes in magnitudes of [Ca2+]i and [Na+]i fluxes, the rate of decay of [Na+]i concentration upon both combined and separate stimulation of β1- and β2-ARs, and the contribution of phosphorylation of PKA targets to the changes in the action potential and [Ca2+]i transient.
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Affiliation(s)
- Kelvin Rozier
- Department of Mathematics and Statistics, Georgia State University, Atlanta, Georgia; and
| | - Vladimir E. Bondarenko
- Department of Mathematics and Statistics, Georgia State University, Atlanta, Georgia; and
- Neuroscience Institute, Georgia State University, Atlanta, Georgia
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19
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Galaz-Montoya M, Wright SJ, Rodriguez GJ, Lichtarge O, Wensel TG. β 2-Adrenergic receptor activation mobilizes intracellular calcium via a non-canonical cAMP-independent signaling pathway. J Biol Chem 2017; 292:9967-9974. [PMID: 28442571 DOI: 10.1074/jbc.m117.787119] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Revised: 04/24/2017] [Indexed: 11/06/2022] Open
Abstract
Beta adrenergic receptors (βARs) are G-protein-coupled receptors essential for physiological responses to the hormones/neurotransmitters epinephrine and norepinephrine which are found in the nervous system and throughout the body. They are the targets of numerous widely used drugs, especially in the case of the most extensively studied βAR, β2AR, whose ligands are used for asthma and cardiovascular disease. βARs signal through Gαs G-proteins and via activation of adenylyl cyclase and cAMP-dependent protein kinase, but some alternative downstream pathways have also been proposed that could be important for understanding normal physiological functioning of βAR signaling and its disruption in disease. Using fluorescence-based Ca2+ flux assays combined with pharmacology and gene knock-out methods, we discovered a previously unrecognized endogenous pathway in HEK-293 cells whereby β2AR activation leads to robust Ca2+ mobilization from intracellular stores via activation of phospholipase C and opening of inositol trisphosphate (InsP3) receptors. This pathway did not involve cAMP, Gαs, or Gαi or the participation of the other members of the canonical β2AR signaling cascade and, therefore, constitutes a novel signaling mechanism for this receptor. This newly uncovered mechanism for Ca2+ mobilization by β2AR has broad implications for adrenergic signaling, cross-talk with other signaling pathways, and the effects of βAR-directed drugs.
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Affiliation(s)
- Monica Galaz-Montoya
- From the Verna and Marrs McLean Department of Biochemistry and Molecular Biology and
| | - Sara J Wright
- From the Verna and Marrs McLean Department of Biochemistry and Molecular Biology and
| | - Gustavo J Rodriguez
- From the Verna and Marrs McLean Department of Biochemistry and Molecular Biology and
| | - Olivier Lichtarge
- From the Verna and Marrs McLean Department of Biochemistry and Molecular Biology and.,the Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030
| | - Theodore G Wensel
- From the Verna and Marrs McLean Department of Biochemistry and Molecular Biology and
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20
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Priming GPCR signaling through the synergistic effect of two G proteins. Proc Natl Acad Sci U S A 2017; 114:3756-3761. [PMID: 28325873 DOI: 10.1073/pnas.1617232114] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Although individual G-protein-coupled receptors (GPCRs) are known to activate one or more G proteins, the GPCR-G-protein interaction is viewed as a bimolecular event involving the formation of a ternary ligand-GPCR-G-protein complex. Here, we present evidence that individual GPCR-G-protein interactions can reinforce each other to enhance signaling through canonical downstream second messengers, a phenomenon we term "GPCR priming." Specifically, we find that the presence of noncognate Gq protein enhances cAMP stimulated by two Gs-coupled receptors, β2-adrenergic receptor (β2-AR) and D1 dopamine receptor (D1-R). Reciprocally, Gs enhances IP1 through vasopressin receptor (V1A-R) but not α1 adrenergic receptor (α1-AR), suggesting that GPCR priming is a receptor-specific phenomenon. The C terminus of either the Gαs or Gαq subunit is sufficient to enhance Gα subunit activation and cAMP levels. Interaction of Gαs or Gαq C termini with the GPCR increases signaling potency, suggesting an altered GPCR conformation as the underlying basis for GPCR priming. We propose three parallel mechanisms involving (i) sequential G-protein interactions at the cognate site, (ii) G-protein interactions at distinct allosteric and cognate sites on the GPCR, and (iii) asymmetric GPCR dimers. GPCR priming suggests another layer of regulation in the classic GPCR ternary-complex model, with broad implications for the multiplicity inherent in signaling networks.
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21
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Hattori Y, Seifert R. Pharmacological Characterization of Human Histamine Receptors and Histamine Receptor Mutants in the Sf9 Cell Expression System. Handb Exp Pharmacol 2017; 241:63-118. [PMID: 28233175 PMCID: PMC7120522 DOI: 10.1007/164_2016_124] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
A large problem of histamine receptor research is data heterogeneity. Various experimental approaches, the complex signaling pathways of mammalian cells, and the use of different species orthologues render it difficult to compare and interpret the published results. Thus, the four human histamine receptor subtypes were analyzed side-by-side in the Sf9 insect cell expression system, using radioligand binding assays as well as functional readouts proximal to the receptor activation event (steady-state GTPase assays and [35S]GTPγS assays). The human H1R was co-expressed with the regulators of G protein signaling RGS4 or GAIP, which unmasked a productive interaction between hH1R and insect cell Gαq. By contrast, functional expression of the hH2R required the generation of an hH2R-Gsα fusion protein to ensure close proximity of G protein and receptor. Fusion of hH2R to the long (GsαL) or short (GsαS) splice variant of Gαs resulted in comparable constitutive hH2R activity, although both G protein variants show different GDP affinities. Medicinal chemistry studies revealed profound species differences between hH1R/hH2R and their guinea pig orthologues gpH1R/gpH2R. The causes for these differences were analyzed by molecular modeling in combination with mutational studies. Co-expression of the hH3R with Gαi1, Gαi2, Gαi3, and Gαi/o in Sf9 cells revealed high constitutive activity and comparable interaction efficiency with all G protein isoforms. A comparison of various cations (Li+, Na+, K+) and anions (Cl-, Br-, I-) revealed that anions with large radii most efficiently stabilize the inactive hH3R state. Potential sodium binding sites in the hH3R protein were analyzed by expressing specific hH3R mutants in Sf9 cells. In contrast to the hH3R, the hH4R preferentially couples to co-expressed Gαi2 in Sf9 cells. Its high constitutive activity is resistant to NaCl or GTPγS. The hH4R shows structural instability and adopts a G protein-independent high-affinity state. A detailed characterization of affinity and activity of a series of hH4R antagonists/inverse agonists allowed first conclusions about structure/activity relationships for inverse agonists at hH4R. In summary, the Sf9 cell system permitted a successful side-by-side comparison of all four human histamine receptor subtypes. This chapter summarizes the results of pharmacological as well as medicinal chemistry/molecular modeling approaches and demonstrates that these data are not only important for a deeper understanding of HxR pharmacology, but also have significant implications for the molecular pharmacology of GPCRs in general.
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Affiliation(s)
- Yuichi Hattori
- Department of Molecular and Medical Pharmacology, Graduate School of Medical and Pharmaceutical Sciences, University of Toyama, Toyama, Japan
| | - Roland Seifert
- Institute of Pharmacology, Medical School of Hannover, Hannover, Germany
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22
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Masuho I, Ostrovskaya O, Kramer GM, Jones CD, Xie K, Martemyanov KA. Distinct profiles of functional discrimination among G proteins determine the actions of G protein-coupled receptors. Sci Signal 2015; 8:ra123. [PMID: 26628681 DOI: 10.1126/scisignal.aab4068] [Citation(s) in RCA: 175] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Members of the heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptor (GPCR) family play key roles in many physiological functions and are extensively exploited pharmacologically to treat diseases. Many of the diverse effects of individual GPCRs on cellular physiology are transduced by heterotrimeric G proteins, which are composed of α, β, and γ subunits. GPCRs interact with and stimulate the binding of guanosine triphosphate (GTP) to the α subunit to initiate signaling. Mammalian genomes encode 16 different G protein α subunits, each one of which has distinct properties. We developed a single-platform, optical strategy to monitor G protein activation in live cells. With this system, we profiled the coupling ability of individual GPCRs for different α subunits, simultaneously quantifying the magnitude of the signal and the rates at which the receptors activated the G proteins. We found that individual receptors engaged multiple G proteins with varying efficacy and kinetics, generating fingerprint-like profiles. Different classes of GPCR ligands, including full and partial agonists, allosteric modulators, and antagonists, distinctly affected these fingerprints to functionally bias GPCR signaling. Finally, we showed that intracellular signaling modulators further altered the G protein-coupling profiles of GPCRs, which suggests that their differential abundance may alter signaling outcomes in a cell-specific manner. These observations suggest that the diversity of the effects of GPCRs on cellular physiology may be determined by their differential engagement of multiple G proteins, coupling to which produces signals with varying signal magnitudes and activation kinetics, properties that may be exploited pharmacologically.
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Affiliation(s)
- Ikuo Masuho
- Department of Neuroscience, The Scripps Research Institute Florida, Jupiter, FL 33458, USA
| | - Olga Ostrovskaya
- Department of Neuroscience, The Scripps Research Institute Florida, Jupiter, FL 33458, USA
| | - Grant M Kramer
- Department of Neuroscience, The Scripps Research Institute Florida, Jupiter, FL 33458, USA. Harriet L. Wilkes Honors College, Florida Atlantic University, Jupiter, FL 33458, USA
| | - Christopher D Jones
- Department of Neuroscience, The Scripps Research Institute Florida, Jupiter, FL 33458, USA. Harriet L. Wilkes Honors College, Florida Atlantic University, Jupiter, FL 33458, USA
| | - Keqiang Xie
- Department of Neuroscience, The Scripps Research Institute Florida, Jupiter, FL 33458, USA
| | - Kirill A Martemyanov
- Department of Neuroscience, The Scripps Research Institute Florida, Jupiter, FL 33458, USA.
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Heusler P, Tardif S, Cussac D. Agonist stimulation at human μ opioid receptors in a [(35)S]GTPγS incorporation assay: observation of "bell-shaped" concentration-response relationships under conditions of strong receptor G protein coupling. J Recept Signal Transduct Res 2015; 36:158-66. [PMID: 26466637 DOI: 10.3109/10799893.2015.1069845] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
CONTEXT The appearance of "bell"- (or "inverted U"-) shaped agonist concentration-response curves (CRCs) in in vitro pharmacological experiments is a frequently observed but poorly communicated phenomenon. In the context of G protein coupled receptor research, it is commonly attributed to the recruitment of secondary targets or to desensitization or feedback processes, but the concrete background of these observations often remains intriguing. OBJECTIVE Here, we addressed the subject of bell-shaped agonist CRCs at the µ opioid receptor (µOR) by testing the impact of experimental conditions favoring G protein coupling. METHODS G protein activation by recombinant human µORs heterologously expressed in CHO cells was assessed in [(35)S]GTPγS binding assays using the opioid ligands DAMGO, morphine, fentanyl and naloxone. Experimental conditions were varied by changing the NaCl (10-300 mM) and the GDP concentration (0.3-30 µM). RESULTS Both the sodium and the GDP concentration were inversely related to G protein coupling, as evident by an increase in basal [(35)S]GTPγS incorporation at low sodium and low GDP levels and by the concomitant appearance of the partial agonist activity of the µOR antagonist, naloxone. Bell-shaped CRCs were observed for the efficacious agonists DAMGO, fentanyl and morphine, and this phenomenon was promoted by low sodium as well as by low GDP concentrations. CONCLUSION µOR agonist CRCs show a non-monotonic behavior with a decline of maximal stimulation under conditions of strong receptor-G protein coupling, and this behavior is visible at the level of G protein activation itself.
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Affiliation(s)
- Peter Heusler
- a Department of Cellular and Molecular Biology , Pierre Fabre Research Center , Castres Cedex , France
| | - Stéphanie Tardif
- a Department of Cellular and Molecular Biology , Pierre Fabre Research Center , Castres Cedex , France
| | - Didier Cussac
- a Department of Cellular and Molecular Biology , Pierre Fabre Research Center , Castres Cedex , France
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Dinter J, Khajavi N, Mühlhaus J, Wienchol CL, Cöster M, Hermsdorf T, Stäubert C, Köhrle J, Schöneberg T, Kleinau G, Mergler S, Biebermann H. The Multitarget Ligand 3-Iodothyronamine Modulates β-Adrenergic Receptor 2 Signaling. Eur Thyroid J 2015; 4:21-9. [PMID: 26601070 PMCID: PMC4640289 DOI: 10.1159/000381801] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 03/19/2015] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND 3-Iodothyronamine (3-T1AM), a signaling molecule with structural similarities to thyroid hormones, induces numerous physiological responses including reversible body temperature decline. One target of 3-T1AM is the trace amine-associated receptor 1 (TAAR1), which is a member of the rhodopsin-like family of G protein-coupled receptors (GPCRs). Interestingly, the effects of 3-T1AM remain detectable in TAAR1 knockout mice, suggesting further targets for 3-T1AM such as adrenergic receptors. Therefore, we evaluated whether β-adrenergic receptor 1 (ADRB1) and 2 (ADRB2) signaling is affected by 3-T1AM in HEK293 cells and in human conjunctival epithelial cells (IOBA-NHC), where these receptors are highly expressed endogenously. METHODS A label-free EPIC system for prescreening the 3-T1AM-induced effects on ADRB1 and ADRB2 in transfected HEK293 cells was used. In addition, ADRB1 and ADRB2 activation was analyzed using a cyclic AMP assay and a MAPK reporter gene assay. Finally, fluorescence Ca(2+) imaging was utilized to delineate 3-T1AM-induced Ca(2+) signaling. RESULTS 3-T1AM (10(-5)-10(-10)M) enhanced isoprenaline-induced ADRB2-mediated Gs signaling but not that of ADRB1-mediated signaling. MAPK signaling remained unaffected for both receptors. In IOBA-NHC cells, norepinephrine-induced Ca(2+) influxes were blocked by the nonselective ADRB blocker timolol (10 µM), indicating that ADRBs are most likely linked with Ca(2+) channels. Notably, timolol was also found to block 3-T1AM (10(-5)M)-induced Ca(2+) influx. CONCLUSIONS The presented data support that 3-T1AM directly modulates β-adrenergic receptor signaling. The relationship between 3-T1AM and β-adrenergic signaling also reveals a potential therapeutic value for suppressing Ca(2+) channel-mediated inflammation processes, occurring in eye diseases such as conjunctivitis.
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Affiliation(s)
- Juliane Dinter
- Institut für Experimentelle Pädiatrische Endokrinologie, Berlin, Germany
| | - Noushafarin Khajavi
- Department of Ophthalmology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Jessica Mühlhaus
- Institut für Experimentelle Pädiatrische Endokrinologie, Berlin, Germany
| | | | - Maxi Cöster
- Institut für Biochemie, Molekulare Biochemie, Medizinische Fakultät, University of Leipzig, Leipzig, Germany
| | - Thomas Hermsdorf
- Institut für Biochemie, Molekulare Biochemie, Medizinische Fakultät, University of Leipzig, Leipzig, Germany
| | - Claudia Stäubert
- Institut für Biochemie, Molekulare Biochemie, Medizinische Fakultät, University of Leipzig, Leipzig, Germany
| | - Josef Köhrle
- Institut für Experimentelle Endokrinologie, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Torsten Schöneberg
- Institut für Biochemie, Molekulare Biochemie, Medizinische Fakultät, University of Leipzig, Leipzig, Germany
| | - Gunnar Kleinau
- Institut für Experimentelle Pädiatrische Endokrinologie, Berlin, Germany
| | - Stefan Mergler
- Department of Ophthalmology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Heike Biebermann
- Institut für Experimentelle Pädiatrische Endokrinologie, Berlin, Germany
- *Heike Biebermann, Institut für Experimentelle Pädiatrische Endokrinologie, Charité-Universitätsmedizin Berlin, Augustenburger Platz 1, DE-13353 Berlin (Germany), E-Mail , Stefan Mergler, Department of Ophthalmology, Charité-Universitätsmedizin Berlin, Augustenburger Platz 1, DE-13353 Berlin (Germany), E-Mail
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Littmann T, Göttle M, Reinartz MT, Kälble S, Wainer IW, Ozawa T, Seifert R. Recruitment of β-arrestin 1 and 2 to the β2-adrenoceptor: analysis of 65 ligands. J Pharmacol Exp Ther 2015; 355:183-90. [PMID: 26306764 DOI: 10.1124/jpet.115.227959] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Accepted: 08/21/2015] [Indexed: 12/20/2022] Open
Abstract
UNLABELLED Beyond canonical signaling via Gαs and cAMP, the concept of functional selectivity at β2-adrenoceptors (β2ARs) describes the ability of adrenergic drugs to stabilize ligand-specific receptor conformations to initiate further signaling cascades comprising additional G-protein classes or β-arrestins (βarr). A set of 65 adrenergic ligands including 40 agonists and 25 antagonists in either racemic or enantiopure forms was used for βarr recruitment experiments based on a split-luciferase assay in a cellular system expressing β2AR. Many agonists showed only (weak) partial agonism regarding βarr recruitment. Potencies and/or efficacies increased depending on the number of chirality centers in (R) configuration; no (S)-configured distomer was more effective at inducing βarr recruitment other than the eutomer. βarr2 was recruited more effectively than βarr1. The analysis of antagonists revealed no significant effects on βarr recruitment. Several agonists showed preference for activation of Gαs GTPase relative to βarr recruitment, and no βarr-biased ligand was identified. IN CONCLUSION 1) agonists show strong bias for Gαs activation relative to βarr recruitment; 2) agonists recruit βarr1 and βarr2 with subtle differences; and 3) there is no evidence for βarr recruitment by antagonists.
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Affiliation(s)
- Timo Littmann
- Institute of Pharmacology, Hannover Medical School, Hannover, Germany (T.L.; M.G.; M.T.R.; S.K., R.S.); Laboratory of Clinical Investigation, National Institute on Aging, Baltimore, Maryland (I.W.W.); and Department of Chemistry, School of Science, The University of Tokyo, Tokyo, Japan (T.O.)
| | - Martin Göttle
- Institute of Pharmacology, Hannover Medical School, Hannover, Germany (T.L.; M.G.; M.T.R.; S.K., R.S.); Laboratory of Clinical Investigation, National Institute on Aging, Baltimore, Maryland (I.W.W.); and Department of Chemistry, School of Science, The University of Tokyo, Tokyo, Japan (T.O.)
| | - Michael T Reinartz
- Institute of Pharmacology, Hannover Medical School, Hannover, Germany (T.L.; M.G.; M.T.R.; S.K., R.S.); Laboratory of Clinical Investigation, National Institute on Aging, Baltimore, Maryland (I.W.W.); and Department of Chemistry, School of Science, The University of Tokyo, Tokyo, Japan (T.O.)
| | - Solveig Kälble
- Institute of Pharmacology, Hannover Medical School, Hannover, Germany (T.L.; M.G.; M.T.R.; S.K., R.S.); Laboratory of Clinical Investigation, National Institute on Aging, Baltimore, Maryland (I.W.W.); and Department of Chemistry, School of Science, The University of Tokyo, Tokyo, Japan (T.O.)
| | - Irving W Wainer
- Institute of Pharmacology, Hannover Medical School, Hannover, Germany (T.L.; M.G.; M.T.R.; S.K., R.S.); Laboratory of Clinical Investigation, National Institute on Aging, Baltimore, Maryland (I.W.W.); and Department of Chemistry, School of Science, The University of Tokyo, Tokyo, Japan (T.O.)
| | - Takeaki Ozawa
- Institute of Pharmacology, Hannover Medical School, Hannover, Germany (T.L.; M.G.; M.T.R.; S.K., R.S.); Laboratory of Clinical Investigation, National Institute on Aging, Baltimore, Maryland (I.W.W.); and Department of Chemistry, School of Science, The University of Tokyo, Tokyo, Japan (T.O.)
| | - Roland Seifert
- Institute of Pharmacology, Hannover Medical School, Hannover, Germany (T.L.; M.G.; M.T.R.; S.K., R.S.); Laboratory of Clinical Investigation, National Institute on Aging, Baltimore, Maryland (I.W.W.); and Department of Chemistry, School of Science, The University of Tokyo, Tokyo, Japan (T.O.)
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Interaction of fenoterol stereoisomers with β2-adrenoceptor-G sα fusion proteins: antagonist and agonist competition binding. Naunyn Schmiedebergs Arch Pharmacol 2015; 388:517-24. [PMID: 25637582 DOI: 10.1007/s00210-015-1086-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Accepted: 01/09/2015] [Indexed: 10/24/2022]
Abstract
The specific interaction between G-protein-coupled receptors and ligand is the starting point for downstream signaling. Fenoterol stereoisomers were successfully used to probe ligand-specific activation (functional selectivity) of the β2-adrenoceptor (β2AR) (Reinartz et al. 2015). In the present study, we extended the pharmacological profile of fenoterol stereoisomers using β2AR-Gsα fusion proteins in agonist and antagonist competition binding assays. Dissociations between binding affinities and effector potencies were found for (R,S')- and (S,S')-isomers of 4'-methoxy-1-naphthyl-fenoterol. Our data corroborate former studies on the importance of the aminoalkyl moiety of fenoterol derivatives for functional selectivity.
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Michel MC, Seifert R. Selectivity of pharmacological tools: implications for use in cell physiology. A review in the theme: Cell signaling: proteins, pathways and mechanisms. Am J Physiol Cell Physiol 2015; 308:C505-20. [PMID: 25631871 DOI: 10.1152/ajpcell.00389.2014] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Accepted: 01/24/2015] [Indexed: 01/08/2023]
Abstract
Pharmacological inhibitors are frequently used to identify the receptors, receptor subtypes, and associated signaling pathways involved in physiological cell responses. Based on the effects of such inhibitors conclusions are drawn about the involvement of their assumed target or lack thereof. While such inhibitors can be useful tools for a better physiological understanding, their uncritical use can lead to incorrect conclusions. This article reviews the concept of inhibitor selectivity and its implication for cell physiology. Specifically, we discuss the implications of using inhibitor vs. activator approaches, issues of direct vs. indirect pathway modulation, implications of inverse agonism and biased signaling, and those of orthosteric vs. allosteric, competitive vs. noncompetitive, and reversible vs. irreversible inhibition. Additional problems can result from inconsistent estimates of inhibitor potency and differences in potency between cell-free systems and intact cells. These concepts are illustrated by several examples of inhibitors displaying affinity for related but distinct targets or even unrelated targets. Of note, many of the issues being addressed are also applicable to genetic inhibition strategies. The main practical conclusion following from these concepts is that investigators should be critical in the choice of inhibitor, its concentrations, and its mode of application. When this advice is adhered to, small-molecule pharmacological inhibitors can be important experimental tools in the hand of physiologists.
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Affiliation(s)
- Martin C Michel
- Department of Pharmacology, Johannes Gutenberg University, Mainz, Germany; and
| | - Roland Seifert
- Department of Pharmacology, Hannover Medical School, Hannover, Germany
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Structure-bias relationships for fenoterol stereoisomers in six molecular and cellular assays at the β2-adrenoceptor. Naunyn Schmiedebergs Arch Pharmacol 2014; 388:51-65. [PMID: 25342094 DOI: 10.1007/s00210-014-1054-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Accepted: 10/02/2014] [Indexed: 01/14/2023]
Abstract
Functional selectivity is well established as an underlying concept of ligand-specific signaling via G protein-coupled receptors (GPCRs). Functionally, selective drugs could show greater therapeutic efficacy and fewer adverse effects. Dual coupling of the β2-adrenoceptor (β2AR) triggers a signal transduction via Gsα and Giα proteins. Here, we examined 12 fenoterol stereoisomers in six molecular and cellular assays. Using β2AR-Gsα and β2AR-Giα fusion proteins, (R,S')- and (S,S')-isomers of 4'-methoxy-1-naphthyl-fenoterol were identified as biased ligands with preference for Gs. G protein-independent signaling via β-arrestin-2 was disfavored by these ligands. Isolated human neutrophils constituted an ex vivo model of β2AR signaling and demonstrated functional selectivity through the dissociation of cAMP accumulation and the inhibition of formyl peptide-stimulated production of reactive oxygen species. Ligand bias was calculated using an operational model of agonism and revealed that the fenoterol scaffold constitutes a promising lead structure for the development of Gs-biased β2AR agonists.
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29
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Kodama D, Togari A. Signaling pathway and physiological role of the alpha-1 adrenergic receptor in human osteoblasts. J Oral Biosci 2014. [DOI: 10.1016/j.job.2014.03.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Nickolls SA, Humphreys S, Clark M, McMurray G. Co-expression of GRK2 reveals a novel conformational state of the µ-opioid receptor. PLoS One 2013; 8:e83691. [PMID: 24376730 PMCID: PMC3869807 DOI: 10.1371/journal.pone.0083691] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Accepted: 11/15/2013] [Indexed: 11/19/2022] Open
Abstract
Agonists at the µ-opioid receptor are known to produce potent analgesic responses in the clinical setting, therefore, an increased understanding of the molecular interactions of ligands at this receptor could lead to improved analgesics. As historically morphine has been shown to be a poor recruiter of β-arrestin in recombinant cell systems and this can be overcome by the co-expression of GRK2, we investigated the effects of GRK2 co-expression, in a recombinant µ-opioid receptor cell line, on ligand affinity and intrinsic activity in both β-arrestin recruitment and [(35)S]GTPγS binding assays. We also investigated the effect of receptor depletion in the β-arrestin assay. GRK2 co-expression increased both agonist Emax and potency in the β-arrestin assay. The increase in agonist potency could not be reversed using receptor depletion, supporting that the effects were due to a novel receptor conformation not system amplification. We also observed a small but significant effect on agonist KL values. Potency values in the [(35)S]GTPγS assay were unchanged; however, inverse agonist activity became evident with GRK2 co-expression. We conclude that this is direct evidence that the µ-opioid receptor is an allosteric protein and the co-expression of signalling molecules elicits changes in its conformation and thus ligand affinity. This has implications when describing how ligands interact with the receptor and how efficacy is determined.
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Affiliation(s)
- Sarah A. Nickolls
- Neusentis, A Pfizer Research Unit, Granta Park, Cambridge, United Kingdom
- * E-mail:
| | - Sian Humphreys
- Neusentis, A Pfizer Research Unit, Granta Park, Cambridge, United Kingdom
| | - Mellissa Clark
- Neusentis, A Pfizer Research Unit, Granta Park, Cambridge, United Kingdom
| | - Gordon McMurray
- Neusentis, A Pfizer Research Unit, Granta Park, Cambridge, United Kingdom
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31
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Kleinau G, Neumann S, Grüters A, Krude H, Biebermann H. Novel insights on thyroid-stimulating hormone receptor signal transduction. Endocr Rev 2013; 34:691-724. [PMID: 23645907 PMCID: PMC3785642 DOI: 10.1210/er.2012-1072] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The TSH receptor (TSHR) is a member of the glycoprotein hormone receptors, a subfamily of family A G protein-coupled receptors. The TSHR is of great importance for the growth and function of the thyroid gland. The TSHR and its endogenous ligand TSH are pivotal proteins with respect to a variety of physiological functions and malfunctions. The molecular events of TSHR regulation can be summarized as a process of signal transduction, including signal reception, conversion, and amplification. The steps during signal transduction from the extra- to the intracellular sites of the cell are not yet comprehensively understood. However, essential new insights have been achieved in recent years on the interrelated mechanisms at the extracellular region, the transmembrane domain, and intracellular components. This review contains a critical summary of available knowledge of the molecular mechanisms of signal transduction at the TSHR, for example, the key amino acids involved in hormone binding or in the structural conformational changes that lead to G protein activation or signaling regulation. Aspects of TSHR oligomerization, signaling promiscuity, signaling selectivity, phenotypes of genetic variations, and potential extrathyroidal receptor activity are also considered, because these are relevant to an understanding of the overall function of the TSHR, including physiological, pathophysiological, and pharmacological perspectives. Directions for future research are discussed.
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Affiliation(s)
- Gunnar Kleinau
- Institute of Experimental Pediatric Endocrinology, Charité-Universitätsmedizin Berlin, Ostring 3, Augustenburger Platz 1, 13353 Berlin, Germany.
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Kodama D, Togari A. Noradrenaline stimulates cell proliferation by suppressing potassium channels via G(i/o) -protein-coupled α(1B) -adrenoceptors in human osteoblasts. Br J Pharmacol 2013; 168:1230-9. [PMID: 23061915 DOI: 10.1111/bph.12000] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Revised: 09/20/2012] [Accepted: 09/24/2012] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND AND PURPOSE Recent studies demonstrated that the sympathetic nervous system regulates bone metabolism via β(2) -adrenoceptors. Although α-adrenoceptors are also expressed in osteogenic cells, their functions in bone metabolism have been less studied. We previously demonstrated that noradrenaline suppressed potassium currents via α(1B) -adrenoceptors in the human osteoblast SaM-1 cell line. The aim of this study was to investigate the signal transduction pathway and the physiological role of noradrenaline in human osteoblasts in more detail. EXPERIMENTAL APPROACH To investigate signal transduction through α(1B) -adrenoceptors, we used whole-cell patch clamp recording and Ca fluorescence imaging. Potassium channels regulate membrane potential and cell proliferation activity in non-excitable cells, so we evaluated cell proliferation activity by BrdU incorporation and WST assay. KEY RESULTS In SaM-1 cells, bath-applied noradrenaline elevated intracellular Ca(2+) concentration and this effect was abolished by both chloroethylclonidine, an α(1B) -adrenoceptor antagonist, and U73122, a PLC inhibitor. However, the inhibitory effect of noradrenaline on whole-cell current was unaffected by U73122. In contrast, in cells pretreated with either Pertussis toxin, a G(i/o) -protein-coupled receptor inhibitor, or gallein, a Gβγ-protein inhibitor, the inhibitory effect of noradrenaline on whole-cell current was significantly suppressed. Noradrenaline-induced enhancement of cell proliferation was inhibited by CsCl, a non-selective potassium channel blocker, gallein and H89, a PKA inhibitor, but not by U73122. CONCLUSIONS AND IMPLICATIONS Noradrenaline facilitated cell proliferation by regulation of potassium currents in human osteoblasts via G(i/o) -protein-coupled α(1B) -adrenoceptors, not via coupling to Gq-proteins.
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Affiliation(s)
- D Kodama
- Department of Pharmacology, School of Dentistry, Aichi-Gakuin University, Nagoya, Japan
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Seifert R. Functional selectivity of G-protein-coupled receptors: from recombinant systems to native human cells. Biochem Pharmacol 2013; 86:853-61. [PMID: 23933388 DOI: 10.1016/j.bcp.2013.07.029] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2013] [Revised: 07/25/2013] [Accepted: 07/25/2013] [Indexed: 10/26/2022]
Abstract
In the mid 1990s, it was assumed that a two-state model, postulating an inactive (R) state and an active (R*) state provides the molecular basis for GPCR activation. However, it became clear that this model could not accommodate many experimental observations. Accordingly, the two-state model was superseded by a multi-state model according to which any given ligand stabilizes a unique receptor conformation with distinct capabilities of activating down-stream G-proteins and β-arrestin. Much of this research was conducted with the β2-adrenoceptor in recombinant systems. At the molecular level, there is now no doubt anymore that ligand-specific receptor conformations, also referred to as functional selectivity, exist. This concept holds great potential for drug discovery in terms of developing drugs with higher selectivity for specific cells and/or cell functions and fewer side effects. A major challenge is the analysis for functional selectivity in native cells. Here, I discuss our current knowledge on functional selectivity of three representative GPCRs, the β2-adrenoceptor and the histamine H2- and H4-receptors, in recombinant systems and native human cells. Studies with human neutrophils and eosinophils support the concept of functional selectivity. A major strategy for the analysis of functional selectivity in native cells is to generate complete concentration/response curves with a large set of structurally diverse ligands for multiple parameters. Next, correlations of potencies and efficacies are analyzed, and deviations of the correlations from linearity are indicative for functional selectivity. Additionally, pharmacological inhibitors are used to dissect cell functions from each other.
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Affiliation(s)
- Roland Seifert
- Institute of Pharmacology, Medical School of Hannover, Carl-Neuberg-Str. 1, D-30625 Hannover, Germany.
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Brunskole Hummel I, Reinartz MT, Kälble S, Burhenne H, Schwede F, Buschauer A, Seifert R. Dissociations in the effects of β2-adrenergic receptor agonists on cAMP formation and superoxide production in human neutrophils: support for the concept of functional selectivity. PLoS One 2013; 8:e64556. [PMID: 23741338 PMCID: PMC3669315 DOI: 10.1371/journal.pone.0064556] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2013] [Accepted: 04/15/2013] [Indexed: 12/02/2022] Open
Abstract
In neutrophils, activation of the β2-adrenergic receptor (β2AR), a Gs-coupled receptor, inhibits inflammatory responses, which could be therapeutically exploited. The aim of this study was to evaluate the effects of various β2AR ligands on adenosine-3',5'-cyclic monophosphate (cAMP) accumulation and N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP)-induced superoxide anion (O2(•-)) production in human neutrophils and to probe the concept of ligand-specific receptor conformations (also referred to as functional selectivity or biased signaling) in a native cell system. This is an important question because so far, evidence for functional selectivity has been predominantly obtained with recombinant systems, due to the inherent difficulties to genetically manipulate human native cells. cAMP concentration was determined by HPLC/tandem mass spectrometry, and O2(•-) formation was assessed by superoxide dismutase-inhibitable reduction of ferricytochrome c. β2AR agonists were generally more potent in inhibiting fMLP-induced O2(•-) production than in stimulating cAMP accumulation. (-)-Ephedrine and dichloroisoproterenol were devoid of any agonistic activity in the cAMP assay, but partially inhibited fMLP-induced O2(•-) production. Moreover, (-)-adrenaline was equi-efficacious in both assays whereas the efficacy of salbutamol was more than two-fold higher in the O2(•-) assay. Functional selectivity was visualized by deviations of ligand potencies and efficacies from linear correlations for various parameters. We obtained no evidence for involvement of protein kinase A in the inhibition of fMLP-induced O2(•-) production after β2AR-stimulation although cAMP-increasing substances inhibited O2(•-) production. Taken together, our data corroborate the concept of ligand-specific receptor conformations with unique signaling capabilities in native human cells and suggest that the β2AR inhibits O2(•-) production in a cAMP-independent manner.
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Affiliation(s)
- Irena Brunskole Hummel
- Institute of Pharmacology, Medical School of Hannover, Hannover, Germany
- Department of Pharmaceutical and Medicinal Chemistry II, University of Regensburg, Regensburg, Germany
| | | | - Solveig Kälble
- Institute of Pharmacology, Medical School of Hannover, Hannover, Germany
| | - Heike Burhenne
- Institute of Pharmacology, Medical School of Hannover, Hannover, Germany
| | | | - Armin Buschauer
- Department of Pharmaceutical and Medicinal Chemistry II, University of Regensburg, Regensburg, Germany
| | - Roland Seifert
- Institute of Pharmacology, Medical School of Hannover, Hannover, Germany
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Näreoja K, Akerman KE, Näsman J. Enhanced early expression of membrane receptors with the Rous sarcoma virus promoter in baculovirus-infected insect cells. Biotechnol Appl Biochem 2013; 59:314-21. [PMID: 23586865 DOI: 10.1002/bab.1029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The effect of the Rous sarcoma virus (RSV) long terminal repeat enhancer/promoter on expression levels of complementary DNAs (cDNAs) encoding seven transmembrane receptors was studied using the baculovirus expression vector system. Expression of the human α(2B)-adrenoceptor (AR) cDNA under the control of the polyhedrin (POL) promoter produced up to 7.6 pmol/mg protein at 28 H post infection (p.i.) in Sf9 cells. The addition of the RSV promoter increased the expression to 11.6 pmol/mg protein. Dramatic increases in expression levels at early times were also obtained with the α(2A)-AR, the M₁ and M₄ muscarinic receptors, and the orexin OX₁ receptor. Analysis of the time-dependent expression revealed that expression driven by the RSV promoter reaches almost maximum 24 H p.i. and that this promoter is superior to the often used POL promoter at early times p.i. when functional studies need to be performed. Functional enhancement of signaling as a result of early expression is demonstrated with the α(2B)-AR and the OX₁ receptor. Finally, enhanced green fluorescent protein fluorescence in living cells was used to monitor expression by various viral promoters. The results verified the early transcriptional activity of the RSV promoter, whereas the cytomegalovirus promoter was found to be poorly active in Sf9 cells.
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Affiliation(s)
- Katja Näreoja
- Department of Biosciences/Biochemistry, Åbo Akademi University, Turku, Finland
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Seifert R. Regulation of G protein subunit composition in cardiomyocytes: pharmacological implications. Naunyn Schmiedebergs Arch Pharmacol 2013; 386:455-7. [PMID: 23568551 DOI: 10.1007/s00210-013-0864-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Accepted: 03/31/2013] [Indexed: 10/27/2022]
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Denis C, Saulière A, Galandrin S, Sénard JM, Galés C. Probing heterotrimeric G protein activation: applications to biased ligands. Curr Pharm Des 2012; 18:128-44. [PMID: 22229559 DOI: 10.2174/138161212799040466] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2011] [Accepted: 11/09/2011] [Indexed: 12/17/2022]
Abstract
Cell surface G protein-coupled receptors (GPCRs) drive numerous signaling pathways involved in the regulation of a broad range of physiologic processes. Today, they represent the largest target for modern drugs development with potential application in all clinical fields. Recently, the concept of "ligand-directed trafficking" has led to a conceptual revolution in pharmacological theory, thus opening new avenues for drug discovery. Accordingly, GPCRs do not function as simple on-off switch but rather as filters capable of selecting the activation of specific signals and thus generating texture responses to ligands, a phenomenon often referred to as ligand-biased signaling. Also, one challenging task today remains optimization of pharmacological assays with increased sensitivity so to better appreciate the inherent texture of ligands. However, considering that a single receptor has pleiotropic signaling properties and that each signal can crosstalk at different levels, biased activity remains thus difficult to evaluate. One strategy to overcome these limitations would be examining the initial steps following receptor activation. Even, if some G protein independent functions have been recently described, heterotrimeric G protein activation remains a general hallmark for all GPCRs families and the first cellular event subsequent to agonist binding to the receptor. Herein, we review the different methodologies classically used or recently developed to monitor G protein activation and discussed them in the context of G protein biased-ligands.
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Affiliation(s)
- Colette Denis
- Institut des Maladies Métaboliques et Cardiovasculaires, Université Toulouse III Paul Sabatier, Centre Hospitalier Universitaire de Toulouse, France.
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Duarte T, Menezes-Rodrigues FS, Godinho RO. Contribution of the extracellular cAMP-adenosine pathway to dual coupling of β2-adrenoceptors to Gs and Gi proteins in mouse skeletal muscle. J Pharmacol Exp Ther 2012; 341:820-8. [PMID: 22438472 DOI: 10.1124/jpet.112.192997] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
β(2)-Adrenoceptor (β(2)-AR) agonists increase skeletal muscle contractile force via activation of G(s) protein/adenylyl cyclases (AC) and increased generation of cAMP. Herein, we evaluated the possible dual coupling of β(2)-AR to G(s) and G(i) proteins and the influence of the β(2)-AR/G(s)-G(i)/cAMP signaling cascade on skeletal muscle contraction. Assuming that the increment of intracellular cAMP is followed by cAMP efflux and extracellular generation of adenosine, the contribution of the extracellular cAMP-adenosine pathway on the β(2)-AR inotropic response was also addressed. The effects of clenbuterol/fenoterol (β(2)-AR agonists), forskolin (AC activator), cAMP/8-bromo-cAMP, and adenosine were evaluated on isometric contractility of mouse diaphragm muscle induced by supramaximal direct electrical stimulation (0.1 Hz, 2 ms duration). Clenbuterol/fenoterol (10-1000 μM), 1 μM forskolin, and 20 μM rolipram induced transient positive inotropic effects that peaked 30 min after stimulation onset, declining to 10 to 20% of peak levels in 30 min. The late descending phase of the β(2)-AR agonist inotropic effect was mimicked by either cAMP or adenosine and abolished by preincubation of diaphragm with pertussis toxin (PTX) (G(i) signaling inhibitor) or the organic anion transporter inhibitor probenecid, indicating a delayed coupling of β(2)-AR to G(i) protein which depends on cAMP efflux. Remarkably, the PTX-sensitive β(2)-AR inotropic effect was inhibited by the A(1) adenosine receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine and ecto-5'-phosphodiesterase inhibitor α,β-methyleneadenosine 5'-diphosphate sodium salt, indicating that β(2)-AR coupling to G(i) is indirect and dependent on A(1) receptor activation. The involvement of the extracellular cAMP-adenosine pathway in β(2)-AR signaling would provide a negative feedback loop that may limit stimulatory G protein-coupled receptor positive inotropism and potential deleterious effects of excessive contractile response.
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Affiliation(s)
- Thiago Duarte
- Division of Cellular Pharmacology, Department of Pharmacology, Escola Paulista de Medicina, Universidade Federal de São Paulo, Rua Três de Maio, 100 São Paulo, SP Brazil 04044-020
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Birnkammer T, Spickenreither A, Brunskole I, Lopuch M, Kagermeier N, Bernhardt G, Dove S, Seifert R, Elz S, Buschauer A. The Bivalent Ligand Approach Leads to Highly Potent and Selective Acylguanidine-Type Histamine H2 Receptor Agonists. J Med Chem 2012; 55:1147-60. [DOI: 10.1021/jm201128q] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- Tobias Birnkammer
- Department of Pharmaceutical/Medicinal
Chemistry, Faculty of Chemistry and Pharmacy, University of Regensburg, Universitätsstrasse 31, D-93053
Regensburg, Germany
| | - Anja Spickenreither
- Department of Pharmaceutical/Medicinal
Chemistry, Faculty of Chemistry and Pharmacy, University of Regensburg, Universitätsstrasse 31, D-93053
Regensburg, Germany
| | - Irena Brunskole
- Department of Pharmaceutical/Medicinal
Chemistry, Faculty of Chemistry and Pharmacy, University of Regensburg, Universitätsstrasse 31, D-93053
Regensburg, Germany
| | - Miroslaw Lopuch
- Department of Pharmaceutical/Medicinal
Chemistry, Faculty of Chemistry and Pharmacy, University of Regensburg, Universitätsstrasse 31, D-93053
Regensburg, Germany
| | - Nicole Kagermeier
- Department of Pharmaceutical/Medicinal
Chemistry, Faculty of Chemistry and Pharmacy, University of Regensburg, Universitätsstrasse 31, D-93053
Regensburg, Germany
| | - Günther Bernhardt
- Department of Pharmaceutical/Medicinal
Chemistry, Faculty of Chemistry and Pharmacy, University of Regensburg, Universitätsstrasse 31, D-93053
Regensburg, Germany
| | - Stefan Dove
- Department of Pharmaceutical/Medicinal
Chemistry, Faculty of Chemistry and Pharmacy, University of Regensburg, Universitätsstrasse 31, D-93053
Regensburg, Germany
| | - Roland Seifert
- Institute
of Pharmacology, Medical School of Hannover, D-30625 Hannover, Germany
| | - Sigurd Elz
- Department of Pharmaceutical/Medicinal
Chemistry, Faculty of Chemistry and Pharmacy, University of Regensburg, Universitätsstrasse 31, D-93053
Regensburg, Germany
| | - Armin Buschauer
- Department of Pharmaceutical/Medicinal
Chemistry, Faculty of Chemistry and Pharmacy, University of Regensburg, Universitätsstrasse 31, D-93053
Regensburg, Germany
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Cortez V, Santana M, Marques AP, Mota A, Rosmaninho-Salgado J, Cavadas C. Regulation of catecholamine release in human adrenal chromaffin cells by β-adrenoceptors. Neurochem Int 2012; 60:387-93. [PMID: 22261351 DOI: 10.1016/j.neuint.2011.12.018] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2011] [Revised: 12/26/2011] [Accepted: 12/28/2011] [Indexed: 11/30/2022]
Abstract
The adrenal gland plays a fundamental role in the response to a variety of stress situations. After a stress condition, adrenal medullary chromaffin cells release, by exocytosis, high quantities of catecholamine (epinephrine, EP; norepinephrine, NE), especially EP. Once in the blood stream, catecholamines reach different target organs, and induce their biological actions through the activation of different adrenoceptors. Adrenal gland cells may also be activated by catecholamines, through hormonal, paracrine and/or autocrine system. The presence of functional adrenoceptors on human adrenal medulla and their involvement on catecholamines secretion was not previously evaluated. In the present study we investigated the role of β(1)-, β(2)- and β(3)-adrenoceptors on catecholamine release from human adrenal chromaffin cells in culture. We observed that the β-adrenoceptor agonist (isoproterenol) and β(2)-adrenoceptor agonist (salbutamol) stimulated catecholamine (NE and EP) release from human adrenal chromaffin cells. Furthermore, the β(2)-adrenoceptor antagonist (ICI 118,551; 100 nM) and β(3)-adrenoceptor antagonist (SR 59230A; 100 nM) inhibited the catecholamine release stimulated by isoproterenol and nicotine in chromaffin cells. The β(1)-adrenoceptor antagonist (atenolol; 100 nM) did not change the isoproterenol- neither the nicotine-evoked catecholamine release from human adrenal chromaffin cells. Moreover, our results show that the protein kinase A (PKA), protein kinase C (PKC), mitogen-activated protein kinase (MAPK) and phospholipase C (PLC) are intracellular mechanisms involved in the catecholamine release evoked by salbutamol. In conclusion, our data suggest that the activation of β(2)- and β(3)-adrenoceptors modulate the basal and evoked catecholamine release, NE and EP, via an autocrine positive feedback loop in human adrenal chromaffin cells.
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Affiliation(s)
- Vera Cortez
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal
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Interactions of recombinant human histamine H1, H2, H3, and H4 receptors with 34 antidepressants and antipsychotics. Naunyn Schmiedebergs Arch Pharmacol 2011; 385:145-70. [DOI: 10.1007/s00210-011-0704-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2011] [Accepted: 10/12/2011] [Indexed: 11/26/2022]
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Propranolol modulates the collateral vascular responsiveness to vasopressin via a Gα-mediated pathway in portal hypertensive rats. Clin Sci (Lond) 2011; 121:545-54. [DOI: 10.1042/cs20100590] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Gastro-oesophageal variceal haemorrhage is one of the most dreadful complications of portal hypertension and can be controlled with vasoconstrictors. Nevertheless, sympathetic tone abnormality and vascular hyporesponsiveness in portal hypertension may impede the haemostatic effects of vasoconstrictors. Propranolol, a β-blocker binding the G-protein-coupled adrenoceptor, is a portal hypotensive agent. However, whether propranolol influences the collateral vasoresponse is unknown. Portal hypertension was induced by PVL (portal vein ligation) in Sprague–Dawley rats. In an acute study with an in situ perfusion model, the collateral responsiveness to AVP (arginine vasopressin) was evaluated with vehicle, propranolol (10 μmol/l), propranolol plus suramin (100 μmol/l, a Gα inhibitor) or suramin pre-incubation. Gα mRNA expression in the splenorenal shunt, the most prominent intra-abdominal collateral vessel, was measured. In the chronic study, rats received DW (distilled water) or propranolol (10 mg·kg−1 of body weight·day−1) for 9 days. Then the concentration–response relationship of AVP and Gα mRNA expression were assessed. Propranolol pre-incubation elevated the perfusion pressure changes of collaterals in response to AVP, which was inhibited by suramin. The splenorenal shunt Gαq and Gα11 mRNA expression were enhanced by propranolol. The group treated with propranolol plus suramin had a down-regulation of Gα11 as compared with the propranolol group. Chronic propranolol treatment reduced mean arterial pressure, PP (portal pressure) and the perfusion pressure changes of collaterals to AVP. Gαs expression was up-regulated. In conclusion, propranolol pre-incubation enhanced the portal-systemic collateral AVP responsiveness in portal hypertensive rats, which was related to Gαq and Gα11 up-regulation. In contrast, the attenuated AVP responsiveness by chronic propranolol treatment was related to Gαs up-regulation. The Gα signalling pathway may be a therapeutic target to control variceal bleeding and PP in portal hypertension.
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Wittmann HJ, Elz S, Seifert R, Straßer A. N α-Methylated phenylhistamines exhibit affinity to the hH4R—a pharmacological and molecular modelling study. Naunyn Schmiedebergs Arch Pharmacol 2011; 384:287-99. [DOI: 10.1007/s00210-011-0671-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2011] [Accepted: 07/08/2011] [Indexed: 01/08/2023]
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Kleinau G, Hoyer I, Kreuchwig A, Haas AK, Rutz C, Furkert J, Worth CL, Krause G, Schülein R. From molecular details of the interplay between transmembrane helices of the thyrotropin receptor to general aspects of signal transduction in family a G-protein-coupled receptors (GPCRs). J Biol Chem 2011; 286:25859-71. [PMID: 21586576 PMCID: PMC3138303 DOI: 10.1074/jbc.m110.196980] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2010] [Revised: 05/10/2011] [Indexed: 12/24/2022] Open
Abstract
Transmembrane helices (TMHs) 5 and 6 are known to be important for signal transduction by G-protein-coupled receptors (GPCRs). Our aim was to characterize the interface between TMH5 and TMH6 of the thyrotropin receptor (TSHR) to gain molecular insights into aspects of signal transduction and regulation. A proline at TMH5 position 5.50 is highly conserved in family A GPCRs and causes a twist in the helix structure. Mutation of the TSHR-specific alanine (Ala-593⁵·⁵⁰) at this position to proline resulted in a 20-fold reduction of cell surface expression. This indicates that TMH5 in the TSHR might have a conformation different from most other family A GPCRs by forming a regular α-helix. Furthermore, linking our own and previous data from directed mutagenesis with structural information led to suggestions of distinct pairs of interacting residues between TMH5 and TMH6 that are responsible for stabilizing either the basal or the active state. Our insights suggest that the inactive state conformation is constrained by a core set of polar interactions among TMHs 2, 3, 6, and 7 and in contrast that the active state conformation is stabilized mainly by non-polar interactions between TMHs 5 and 6. Our findings might be relevant for all family A GPCRs as supported by a statistical analysis of residue properties between the TMHs of a vast number of GPCR sequences.
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Affiliation(s)
- Gunnar Kleinau
- Leibniz-Institut für Molekulare Pharmakologie, 13125 Berlin, Germany.
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Sutor S, Heilmann J, Seifert R. Impact of fusion to Gα(i2) and co-expression with RGS proteins on pharmacological properties of human cannabinoid receptors CB₁R and CB₂R. ACTA ACUST UNITED AC 2011; 63:1043-55. [PMID: 21718288 DOI: 10.1111/j.2042-7158.2011.01307.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVES G protein coupled receptor (GPCR)-Gα fusion proteins are often employed to investigate receptor/G protein interaction. In this study, the impact of Gα fusion proteins on pharmacology of CBRs, both mediating signals through Gα(i) proteins, were investigated. Gα(i2) was fused to the C-terminus of the CBRs or co-expressed with non-fused Gα(i2) in Sf9 cells, always together with Gβ₁γ₂. Furthermore, the impact of RGS proteins on CBR signaling in combination with the CBR fusion approach was examined, using RGS4 and RGS19 as paradigms. METHODS CBR ligands were characterized in the steady-state GTPase assay and pharmacological properties of ligands in the different test systems were correlated. KEY FINDINGS Fusion of CBRs to Gα(i2) enhanced the maximal stimulatory effects of ligands compared to the co-expression system, especially for CB₂R. RGS4, but not RGS19, behaved as a GTPase-activating protein at CBRs in the Gα(i2) co-expression and fusion system. Fusion of GPCR, most prominently CB₂R, to Gα(i2) , and co-expression with RGS4 altered the pharmacological properties of ligands. CONCLUSIONS Our data suggest that fusion of CB₂R to Gα(i2) and co-expression with RGS4 impedes with conformational changes. Moreover, our results support the concept of ligand-specific receptor conformations. Finally, this paper describes the most sensitive CBR test system currently available.
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Affiliation(s)
- Sarah Sutor
- Department of Pharmaceutical Biology, Institute of Pharmacy, University of Regensburg, Regensburg Institute of Pharmacology, Medical School of Hannover, Hannover, Germany
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Baloglu E, Reingruber T, Bärtsch P, Mairbäurl H. β2-Adrenergics in hypoxia desensitize receptors but blunt inhibition of reabsorption in rat lungs. Am J Respir Cell Mol Biol 2011; 45:1059-68. [PMID: 21562317 DOI: 10.1165/rcmb.2010-0273oc] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Alveolar edema and decreased inspired Po(2) decrease the oxygen supply to alveolar epithelia, impairing β(2)-adrenergic receptor (β2AR) signaling and alveolar reabsorption. β2AR agonists potently stimulate alveolar reabsorption. Thus, hypoxia impairs a major defense mechanism that provides protection from alveolar edema. Because in vivo data on the combined effects of prolonged hypoxia and β2AR agonist treatment on β2AR signaling are sparse, we tested whether in vivo hypoxia augments the inactivation of β2AR during prolonged stimulation. Rats were exposed to normoxia (N) and hypoxia (8% O(2); H), and were also treated with terbutaline (T; 2.5 mg/kg, intraperitoneal, twice daily) or saline (S) for 4 days. β2AR signaling was studied in alveolar epithelial (ATII) cells and in whole-lung tissue from treated rats. The terbutaline-stimulated formation of cyclic adenosine monophosphate was decreased by approximately 40% in whole lung and in ATII cells of NT, HS, and HT. The effects were not additive. The β2AR number was increased in HS, but decreased in NT and HT. Treatment increased the G-protein-coupled receptor kinase 2 protein in the plasma membranes of ATII cells, but did not affect G proteins. In vivo hypoxia significantly decreased total and amiloride-sensitive alveolar fluid reabsorption, which was prevented by acute alveolar treatment and 4 days of systemic terbutaline treatment. The αENaC (subunit of epithelial Na channels) protein in plasma membranes was increased in HT, without effects on mRNA. These results indicate that prolonged alveolar hypoxia and treatment with terbutaline impaired β2AR signaling in alveolar epithelia and in whole lungs, and this signaling was not further impaired by hypoxia. Despite impaired β2AR signaling, treatment with terbutaline for 4 days prevented the inhibition of alveolar reabsorption caused by in vivo hypoxia.
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Affiliation(s)
- Emel Baloglu
- Medical Clinic VII, Sports Medicine, University Hospital Heidelberg, University of Heidelberg, Germany
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Shim JY. Understanding functional residues of the cannabinoid CB1. Curr Top Med Chem 2011; 10:779-98. [PMID: 20370713 DOI: 10.2174/156802610791164210] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2009] [Accepted: 10/27/2009] [Indexed: 02/07/2023]
Abstract
The brain cannabinoid (CB(1)) receptor that mediates numerous physiological processes in response to marijuana and other psychoactive compounds is a G protein coupled receptor (GPCR) and shares common structural features with many rhodopsin class GPCRs. For the rational development of therapeutic agents targeting the CB(1) receptor, understanding of the ligand-specific CB(1) receptor interactions responsible for unique G protein signals is crucial. For a more than a decade, a combination of mutagenesis and computational modeling approaches has been successfully employed to study the ligand-specific CB(1) receptor interactions. In this review, after a brief discussion about recent advances in understanding of some structural and functional features of GPCRs commonly applicable to the CB(1) receptor, the CB(1) receptor functional residues reported from mutational studies are divided into three different types, ligand binding (B), receptor stabilization (S) and receptor activation (A) residues, to delineate the nature of the binding pockets of anandamide, CP55940, WIN55212-2 and SR141716A and to describe the molecular events of the ligand-specific CB(1) receptor activation from ligand binding to G protein signaling. Taken these CB(1) receptor functional residues, some of which are unique to the CB(1) receptor, together with the biophysical knowledge accumulated for the GPCR active state, it is possible to propose the early stages of the CB(1) receptor activation process that not only provide some insights into understanding molecular mechanisms of receptor activation but also are applicable for identifying new therapeutic agents by applying the validated structure-based approaches, such as virtual high throughput screening (HTS) and fragment-based approach (FBA).
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Affiliation(s)
- Joong-Youn Shim
- J.L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, 700 George Street, Durham, NC 27707, USA.
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48
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Abstract
In many cases, the coexpression of GPCRs with G-proteins and/or regulators of G-protein signaling (RGS-proteins) allows a successful reconstitution of high-affinity agonist binding and functional responses. However, in some cases, coexpressed GPCRs and G-proteins interact inefficiently, resulting in weak [³⁵S]GTPγS- and steady-state GTPase assay signals. This may be, for example, caused by a rapid dissociation of the G-protein from the plasma membrane, as has been reported for Gα(s). Moreover, for a detailed characterization of GPCR/G-protein interactions, it may be required to work with a defined GPCR/G-protein stoichiometry and to avoid cross-interaction with endogenous G-proteins. Cross-talk to endogenous G-proteins has been shown to play a role in some mammalian expression systems. These problems can be addressed by the generation of GPCR-Gα fusion proteins and their expression in Sf9 insect cells. When the C-terminus of the receptor is fused to the N-terminus of the G-protein, a 1:1 stoichiometry of both proteins is achieved. In addition, the close proximity of GPCR and G-protein in fusion proteins leads to enhanced interaction efficiency, resulting in increased functional signals. This approach can also be extended to fusion proteins of GPCRs with RGS-proteins, specifically when steady-state GTP hydrolysis is used as read-out. GPCR-RGS fusion proteins optimize the interaction of RGS-proteins with coexpressed Gα subunits, since the location of the RGS-protein is close to the site of receptor-mediated G-protein activation. Moreover, in contrast to coexpression systems, GPCR-Gα and GPCR-RGS fusion proteins provide a possibility to imitate physiologically occurring interactions, for example, the precoupling of receptors and G-proteins or the formation of complexes between GPCRs, G-proteins and RGS-proteins (transducisomes). In this chapter, we describe the technique for the generation of fusion proteins and show the application of this approach for the characterization of constitutively active receptors.
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Jakubík J, Janíčková H, El-Fakahany EE, Doležal V. Negative cooperativity in binding of muscarinic receptor agonists and GDP as a measure of agonist efficacy. Br J Pharmacol 2011; 162:1029-44. [PMID: 20958290 PMCID: PMC3051377 DOI: 10.1111/j.1476-5381.2010.01081.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2010] [Revised: 08/23/2010] [Accepted: 09/22/2010] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSE Conventional determination of agonist efficacy at G-protein coupled receptors is measured by stimulation of guanosine-5'-γ-thiotriphosphate (GTPγS) binding. We analysed the role of guanosine diphosphate (GDP) in the process of activation of the M₂ muscarinic acetylcholine receptor and provide evidence that negative cooperativity between agonist and GDP binding is an alternative measure of agonist efficacy. EXPERIMENTAL APPROACH Filtration and scintillation proximity assays measured equilibrium binding as well as binding kinetics of [³⁵S]GTPγS and [³H]GDP to a mixture of G-proteins as well as individual classes of G-proteins upon binding of structurally different agonists to the M₂ muscarinic acetylcholine receptor. KEY RESULTS Agonists displayed biphasic competition curves with the antagonist [³H]-N-methylscopolamine. GTPγS (1 µM) changed the competition curves to monophasic with low affinity and 50 µM GDP produced a similar effect. Depletion of membrane-bound GDP increased the proportion of agonist high-affinity sites. Carbachol accelerated the dissociation of [³H]GDP from membranes. The inverse agonist N-methylscopolamine slowed GDP dissociation and GTPγS binding without changing affinity for GDP. Carbachol affected both GDP association with and dissociation from G(i/o) G-proteins but only its dissociation from G(s/olf) G-proteins. CONCLUSIONS AND IMPLICATIONS These findings suggest the existence of a low-affinity agonist-receptor conformation complexed with GDP-liganded G-protein. Also the negative cooperativity between GDP and agonist binding at the receptor/G-protein complex determines agonist efficacy. GDP binding reveals differences in action of agonists versus inverse agonists as well as differences in activation of G(i/o) versus G(s/olf) G-proteins that are not identified by conventional GTPγS binding.
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Affiliation(s)
- J Jakubík
- Institute of Physiology Academy of Sciences of the Czech Republic, Prague, Czech Republic.
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50
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Wichard JD, ter Laak A, Krause G, Heinrich N, Kühne R, Kleinau G. Chemogenomic analysis of G-protein coupled receptors and their ligands deciphers locks and keys governing diverse aspects of signalling. PLoS One 2011; 6:e16811. [PMID: 21326864 PMCID: PMC3033908 DOI: 10.1371/journal.pone.0016811] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Accepted: 01/12/2011] [Indexed: 11/28/2022] Open
Abstract
Understanding the molecular mechanism of signalling in the important super-family of G-protein-coupled receptors (GPCRs) is causally related to questions of how and where these receptors can be activated or inhibited. In this context, it is of great interest to unravel the common molecular features of GPCRs as well as those related to an active or inactive state or to subtype specific G-protein coupling. In our underlying chemogenomics study, we analyse for the first time the statistical link between the properties of G-protein-coupled receptors and GPCR ligands. The technique of mutual information (MI) is able to reveal statistical inter-dependence between variations in amino acid residues on the one hand and variations in ligand molecular descriptors on the other. Although this MI analysis uses novel information that differs from the results of known site-directed mutagenesis studies or published GPCR crystal structures, the method is capable of identifying the well-known common ligand binding region of GPCRs between the upper part of the seven transmembrane helices and the second extracellular loop. The analysis shows amino acid positions that are sensitive to either stimulating (agonistic) or inhibitory (antagonistic) ligand effects or both. It appears that amino acid positions for antagonistic and agonistic effects are both concentrated around the extracellular region, but selective agonistic effects are cumulated between transmembrane helices (TMHs) 2, 3, and ECL2, while selective residues for antagonistic effects are located at the top of helices 5 and 6. Above all, the MI analysis provides detailed indications about amino acids located in the transmembrane region of these receptors that determine G-protein signalling pathway preferences.
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Affiliation(s)
- Jörg D. Wichard
- Leibniz-Institut für Molekulare Pharmakologie, Berlin, Germany
- Bayer-Schering Pharma, Berlin, Germany
| | | | - Gerd Krause
- Leibniz-Institut für Molekulare Pharmakologie, Berlin, Germany
| | | | - Ronald Kühne
- Leibniz-Institut für Molekulare Pharmakologie, Berlin, Germany
- * E-mail:
| | - Gunnar Kleinau
- Leibniz-Institut für Molekulare Pharmakologie, Berlin, Germany
- Institute of Experimental Pediatric Endocrinology, Charité Universitätsmedizin Berlin, Berlin, Germany
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