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Matarrese P, Maccari S, Gambardella L, Vona R, Barbagallo F, Vezzi V, Stati T, Grò MC, Giovannetti A, Catalano L, Molinari P, Marano G, Ambrosio C. Benzodiazepine diazepam regulates cell surface β1-adrenergic receptor density in human monocytes. Eur J Pharmacol 2023; 948:175700. [PMID: 37001579 DOI: 10.1016/j.ejphar.2023.175700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 03/23/2023] [Accepted: 03/28/2023] [Indexed: 03/31/2023]
Abstract
Downregulation of cell surface β-adrenergic receptors (β-AR) is an important adaptive response that prevents deleterious effects of receptor overstimulation. Various factors including reactive oxygen species cause β-AR downregulation. In this study, we evaluated the effects of ligands of the peripheral benzodiazepine receptor (PBR), a key protein in regulating oxidative stress, on surface density of endogenous β1-and β2-ARs in highly differentiated cells such as human monocytes, which express both β-AR subtypes. β-AR expression in human monocytes was evaluated by flow cytometry, qPCR and western blotting. Monocyte treatment with β-AR agonist isoproterenol did not change surface β1-AR density while downregulating surface β2-AR density. This effect was antagonized by the β-blocker propranolol. An opposite response was observed with benzodiazepine diazepam that led to a time-dependent reduction in β1-AR density. In particular, while no significant downregulation was observed after 3 h of treatment, only 63% of β1-ARs were still present on the cell surface after 48 h of treatment with diazepam at 1 μM. Treatment with the PBR antagonist PK11195, but not with propranolol, antagonized the effects of diazepam. No change in β1-AR-mRNA or protein levels was observed at any time after diazepam treatment. We also found that diazepam did not affect Gs-protein or β-arrestin-2 recruitment for both β-ARs in engineered fibroblasts, further suggesting that diazepam activity on β1-AR density is mediated by PBR. Finally, no sex-related differences were found. Collectively, these results indicate that monocyte β1-ARs are resistant to catecholamine-mediated downregulation and suggest that PBR plays an important role in regulating β1-AR density.
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Venneri M, Vezzi V, Di Mise A, Ranieri M, Centrone M, Tamma G, Nejsum LN, Valenti G. Novel signalling pathways in nephrogenic syndrome of inappropriate antidiuresis: functional implication of site-specific AQP2 phosphorylation. J Physiol 2023. [PMID: 36823952 DOI: 10.1113/jp284039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Accepted: 02/10/2023] [Indexed: 02/25/2023] Open
Abstract
Nephrogenic syndrome of inappropriate antidiuresis (NSIAD) is a rare X-linked disease caused by gain-of-function mutations of arginine vasopressin receptor 2 (V2R). Patients with NSIAD are characterized by the inability to excrete a free water load and by inappropriately increased urinary osmolality despite very low levels of plasma vasopressin, resulting in euvolaemic hyponatraemia. To dissect the signalling downstream V2R constitutively active variants, Flp-In T-REx Madin-Darby canine kidney (FTM) cells, stably transfected with V2R mutants (R137L, R137C and F229V) and AQP2-wt or non-phosphorylatable AQP2-S269A/AQP2-S256A, were used as cellular models. All three activating V2R mutations presented constitutive plasma membrane expression of AQP2-wt and significantly higher basal water permeability. In addition, V2R-R137L/C showed significantly higher activity of Rho-associated kinase (ROCK), a serine/threonine kinase previously suggested to be involved in S269-AQP2 phosphorylation downstream of these V2R mutants. Interestingly, FTM cells expressing V2R-R137L/C mutants and AQP2-S269A showed a significant reduction in AQP2 membrane abundance and a significant reduction in ROCK activity, indicating the crucial importance of S269-AQP2 phosphorylation in the gain-of-function phenotype. Conversely, V2R-R137L/C mutants retained the gain-of-function phenotype when AQP2-S256A was co-expressed. In contrast, cells expressing the F229V mutant and the non-phosphorylatable AQP2-S256A had a significant reduction in AQP2 membrane abundance along with a significant reduction in basal osmotic water permeability, indicating a crucial role of Ser256 for this mutant. These data indicate that the constitutive AQP2 trafficking associated with the gain-of-function V2R-R137L/C mutants causing NSIAD is protein kinase A independent and requires an intact Ser269 in AQP2 under the control of ROCK phosphorylation. KEY POINTS: Nephrogenic syndrome of inappropriate antidiuresis is caused by two constitutively active variant phenotypes of AVPR2, one sensitive to vaptans (V2R-F229V) and the other vaptan resistant (V2R-R137C/L). In renal cells, all three activating arginine vasopressin receptor 2 (V2R) variants display constitutive AQP2 plasma membrane expression and high basal water permeability. In cells expressing V2R-R137L/C mutants, disruption of the AQP2-S269 phosphorylation site caused the loss of the gain-of-function phenotype, which, in contrast, was retained in V2R-F229V-expressing cells. Cells expressing the V2R-F229V mutant were instead sensitive to disruption of the AQP2-S256 phosphorylation site. The serine/threonine kinase Rho-associated kinase (ROCK) was found to be involved in AQP2-S269 phosphorylation downstream of the V2R-R137L/C mutants. These findings might have clinical relevance for patients with nephrogenic syndrome of inappropriate antidiuresis.
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Affiliation(s)
- Maria Venneri
- Department of Biosciences, Biotechnology and Environment, University of Bari Aldo Moro, Bari, Italy
| | - Vanessa Vezzi
- National Center for Drug Research and Evaluation, Istituto Superiore di Sanità, Rome, Italy
| | - Annarita Di Mise
- Department of Biosciences, Biotechnology and Environment, University of Bari Aldo Moro, Bari, Italy
| | - Marianna Ranieri
- Department of Biosciences, Biotechnology and Environment, University of Bari Aldo Moro, Bari, Italy
| | - Mariangela Centrone
- Department of Biosciences, Biotechnology and Environment, University of Bari Aldo Moro, Bari, Italy
| | - Grazia Tamma
- Department of Biosciences, Biotechnology and Environment, University of Bari Aldo Moro, Bari, Italy
| | - Lene N Nejsum
- Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Giovanna Valenti
- Department of Biosciences, Biotechnology and Environment, University of Bari Aldo Moro, Bari, Italy
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Maccari S, Pace V, Barbagallo F, Stati T, Ambrosio C, Grò MC, Molinari P, Vezzi V, Catalano L, Matarrese P, Patrizio M, Rizzi R, Marano G. Intermittent β-adrenergic blockade downregulates the gene expression of β-myosin heavy chain in the mouse heart. Eur J Pharmacol 2020; 882:173287. [PMID: 32585157 DOI: 10.1016/j.ejphar.2020.173287] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 06/11/2020] [Accepted: 06/15/2020] [Indexed: 01/14/2023]
Abstract
Expression of the β-myosin heavy chain (β-MHC), a major component of the cardiac contractile apparatus, is tightly regulated as even modest increases can be detrimental to heart under stress. In healthy hearts, continuous inhibition of β-adrenergic tone upregulates β-MHC expression. However, it is unknown whether the duration of the β-adrenergic inhibition and β-MHC expression are related. Here, we evaluated the effects of intermittent β-blockade on cardiac β-MHC expression. To this end, the β-blocker propranolol, at the dose of 15mg/kg, was administered once a day in mice for 14 days. This dosing schedule caused daily drug-free periods of at least 6 h as evidenced by propranolol plasma concentrations and cardiac β-adrenergic responsiveness. Under these conditions, β-MHC expression decreased by about 75% compared to controls. This effect was abolished in mice lacking β1- but not β2-adrenergic receptors (β-AR) indicating that β-MHC expression is regulated in a β1-AR-dependent manner. In β1-AR knockout mice, the baseline β-MHC expression was fourfold higher than in wild-type mice. Also, we evaluated the impact of intermittent β-blockade on β-MHC expression in mice with systolic dysfunction, in which an increased β-MHC expression occurs. At 3 weeks after myocardial infarction, mice showed systolic dysfunction and upregulation of β-MHC expression. Intermittent β-blockade decreased β-MHC expression while attenuating cardiac dysfunction. In vitro studies showed that propranolol does not affect β-MHC expression on its own but antagonizes catecholamine effects on β-MHC expression. In conclusion, a direct relationship occurs between the duration of the β-adrenergic inhibition and β-MHC expression through the β1-AR.
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Affiliation(s)
- Sonia Maccari
- Center for Gender-Specific Medicine, National Institute of Health, Rome, Italy
| | - Valentina Pace
- Institute of Biochemistry and Cellular Biology, National Council of Research, Monterotondo (RM), Italy
| | | | - Tonino Stati
- Center for Gender-Specific Medicine, National Institute of Health, Rome, Italy
| | - Caterina Ambrosio
- National Center for Drug Research and Evaluation, National Institute of Health, Rome, Italy
| | - Maria Cristina Grò
- National Center for Drug Research and Evaluation, National Institute of Health, Rome, Italy
| | - Paola Molinari
- National Center for Drug Research and Evaluation, National Institute of Health, Rome, Italy
| | - Vanessa Vezzi
- National Center for Drug Research and Evaluation, National Institute of Health, Rome, Italy
| | | | - Paola Matarrese
- Center for Gender-Specific Medicine, National Institute of Health, Rome, Italy
| | - Mario Patrizio
- Center for Gender-Specific Medicine, National Institute of Health, Rome, Italy
| | - Roberto Rizzi
- Fondazione Istituto Nazionale di Genetica Molecolare "Romeo ed Enrica Invernizzi", Milan, Italy; Institute for Biomedical Technologies, National Council of Research, Milan, Italy
| | - Giuseppe Marano
- Center for Gender-Specific Medicine, National Institute of Health, Rome, Italy.
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Vezzi V, Ambrosio C, Grò MC, Molinari P, Süral G, Costa T, Onaran HO, Cotecchia S. Vasopressin receptor 2 mutations in the nephrogenic syndrome of inappropriate antidiuresis show different mechanisms of constitutive activation for G protein coupled receptors. Sci Rep 2020; 10:9111. [PMID: 32499611 PMCID: PMC7272623 DOI: 10.1038/s41598-020-65996-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Accepted: 05/13/2020] [Indexed: 01/14/2023] Open
Abstract
Vasopressin receptor 2 (V2R) mutations causing the nephrogenic syndrome of inappropriate antidiuresis (NSIAD) can generate two constitutively active receptor phenotypes. One type results from residue substitutions in several V2R domains and is sensitive to vaptan inverse agonists. The other is only caused by Arg 137 replacements and is vaptan resistant. We compared constitutive and agonist-driven interactions of the vaptan-sensitive F229V and vaptan-resistant R137C/L V2R mutations with β-arrestin 1, β-arrestin 2, and Gαs, using null fibroblasts reconstituted with individual versions of the ablated transduction protein genes. F229V displayed very high level of constitutive activation for Gs but not for β-arrestins, and enhanced or normal responsiveness to agonists and inverse agonists. In contrast, R137C/L mutants exhibited maximal levels of constitutive activation for βarrestin 2 and Gs, minimal levels for β-arrestin 1, but a sharp decline of ligands sensitivity at all transducer interactions. The enhanced constitutive activity and reduced ligand sensitivity of R137 mutants on cAMP signaling persisted in cells lacking β-arrestins, indicating that these are intrinsic molecular properties of the mutations, not the consequence of altered receptor trafficking. The results suggest that the two groups of NSIAD mutations represent two distinct molecular mechanisms of constitutive activation in GPCRs.
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Affiliation(s)
- Vanessa Vezzi
- Istituto Superiore di Sanitá, National Center for Drug Research and Evaluation, Rome, Italy
| | - Caterina Ambrosio
- Istituto Superiore di Sanitá, National Center for Drug Research and Evaluation, Rome, Italy
| | - Maria Cristina Grò
- Istituto Superiore di Sanitá, National Center for Drug Research and Evaluation, Rome, Italy
| | - Paola Molinari
- Istituto Superiore di Sanitá, National Center for Drug Research and Evaluation, Rome, Italy
| | - Gökçe Süral
- Ankara University, Faculty of Medicine, Department of Pharmacology, Molecular biology and Technology development unit, Sıhhiye, Ankara, Turkey
| | - Tommaso Costa
- Istituto Superiore di Sanitá, National Center for Drug Research and Evaluation, Rome, Italy
| | - H Ongun Onaran
- Ankara University, Faculty of Medicine, Department of Pharmacology, Molecular biology and Technology development unit, Sıhhiye, Ankara, Turkey
| | - Susanna Cotecchia
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, 70125, Bari, Italy.
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Ranieri M, Tamma G, Pellegrino T, Vezzi V, Ambrosio C, Grò C, Di Mise A, Costa T, Valenti G, Cotecchia S. Gain-of-function mutations of the V2 vasopressin receptor in nephrogenic syndrome of inappropriate antidiuresis (NSIAD): a cell-based assay to assess constitutive water reabsorption. Pflugers Arch 2019; 471:1291-1304. [PMID: 31486901 DOI: 10.1007/s00424-019-02307-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 08/28/2019] [Accepted: 08/29/2019] [Indexed: 12/31/2022]
Abstract
Nephrogenic syndrome of inappropriate antidiuresis (NSIAD) is a recently identified chromosome X-linked disease associated with gain-of-function mutations of the V2 vasopressin receptor (V2R), a G-protein-coupled receptor. It is characterized by inability to excrete a free water load, hyponatremia, and undetectable vasopressin-circulating levels. Hyponatremia can be quite severe in affected male children. To gain a deeper insight into the functional properties of the V2R active mutants and how they might translate into the pathological outcome of NSIAD, in this study, we have expressed the wild-type V2R and three constitutively active V2R mutants associated with NSIAD (R137L, R137C, and the F229V) in MCD4 cells, a cell line derived from renal mouse collecting duct, stably expressing the vasopressin-sensitive water channel aquaporin-2 (AQP2). Our findings indicate that in cells expressing each active mutant, AQP2 was constitutively localized to the apical plasma membrane in the absence of vasopressin stimulation. In line with these observations, under basal conditions, osmotic water permeability in cells expressing the constitutively active mutants was significantly higher compared to that of cells expressing the wild-type V2R. Our findings demonstrate a direct link between activating mutations of the V2R and the perturbation of water balance in NSIAD. In addition, this study provides a useful cell-based assay system to assess the functional consequences of newly discovered activating mutations of the V2R on water permeability in kidney cells and to screen the effect of drugs on the mutated receptors.
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Affiliation(s)
- Marianna Ranieri
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, 70125, Bari, Italy
| | - Grazia Tamma
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, 70125, Bari, Italy.,Istituto Nazionale di Biostrutture e Biosistemi, 00136, Rome, Italy
| | - Tommaso Pellegrino
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, 70125, Bari, Italy
| | - Vanessa Vezzi
- Department of Pharmacology, Istituto Superiore di Sanità, 00161, Rome, Italy
| | - Caterina Ambrosio
- Department of Pharmacology, Istituto Superiore di Sanità, 00161, Rome, Italy
| | - Cristina Grò
- Department of Pharmacology, Istituto Superiore di Sanità, 00161, Rome, Italy
| | - Annarita Di Mise
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, 70125, Bari, Italy
| | - Tommaso Costa
- Department of Pharmacology, Istituto Superiore di Sanità, 00161, Rome, Italy
| | - Giovanna Valenti
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, 70125, Bari, Italy. .,Istituto Nazionale di Biostrutture e Biosistemi, 00136, Rome, Italy. .,Center of Excellence in Comparative Genomics (CEGBA), University of Bari, 70125, Bari, Italy.
| | - Susanna Cotecchia
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, 70125, Bari, Italy.
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Bird MF, Cerlesi MC, Brown M, Malfacini D, Vezzi V, Molinari P, Micheli L, Mannelli LDC, Ghelardini C, Guerrini R, Calò G, Lambert DG. Characterisation of the Novel Mixed Mu-NOP Peptide Ligand Dermorphin-N/OFQ (DeNo). PLoS One 2016; 11:e0156897. [PMID: 27272042 PMCID: PMC4896453 DOI: 10.1371/journal.pone.0156897] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 05/20/2016] [Indexed: 11/18/2022] Open
Abstract
INTRODUCTION Opioid receptors are currently classified as Mu (μ), Delta (δ), Kappa (κ) plus the opioid related nociceptin/orphanin FQ (N/OFQ) peptide receptor (NOP). Despite compelling evidence for interactions and benefits of targeting more than one receptor type in producing analgesia, clinical ligands are Mu agonists. In this study we have designed a Mu-NOP agonist named DeNo. The Mu agonist component is provided by dermorphin, a peptide isolated from the skin of Phyllomedusa frogs and the NOP component by the endogenous agonist N/OFQ. METHODS We have assessed receptor binding profile of DeNo and compared with dermorphin and N/OFQ. In a series of functional screens we have assessed the ability to (i) increase Ca2+ in cells coexpressing recombinant receptors and a the chimeric protein Gαqi5, (ii) stimulate the binding of GTPγ[35S], (iii) inhibit cAMP formation, (iv) activate MAPKinase, (v) stimulate receptor-G protein and arrestin interaction using BRET, (vi) electrically stimulated guinea pig ileum (gpI) assay and (vii) ability to produce analgesia via the intrathecal route in rats. RESULTS DeNo bound to Mu (pKi; 9.55) and NOP (pKi; 10.22) and with reasonable selectivity. This translated to increased Ca2+ in Gαqi5 expressing cells (pEC50 Mu 7.17; NOP 9.69), increased binding of GTPγ[35S] (pEC50 Mu 7.70; NOP 9.50) and receptor-G protein interaction in BRET (pEC50 Mu 8.01; NOP 9.02). cAMP formation was inhibited and arrestin was activated (pEC50 Mu 6.36; NOP 8.19). For MAPK DeNo activated p38 and ERK1/2 at Mu but only ERK1/2 at NOP. In the gpI DeNO inhibited electrically-evoked contractions (pEC50 8.63) that was sensitive to both Mu and NOP antagonists. DeNo was antinociceptive in rats. CONCLUSION Collectively these data validate the strategy used to create a novel bivalent Mu-NOP peptide agonist by combining dermorphin (Mu) and N/OFQ (NOP). This molecule behaves essentially as the parent compounds in vitro. In the antonocicoeptive assays employed in this study DeNo displays only weak antinociceptive properties.
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MESH Headings
- Animals
- CHO Cells
- Calcium/metabolism
- Cricetulus
- Guinea Pigs
- HEK293 Cells
- Humans
- Male
- Opioid Peptides/chemistry
- Peptides/chemical synthesis
- Peptides/chemistry
- Peptides/pharmacology
- Rats
- Rats, Sprague-Dawley
- Receptors, Opioid/agonists
- Receptors, Opioid/chemistry
- Receptors, Opioid/metabolism
- Receptors, Opioid, mu/agonists
- Receptors, Opioid, mu/chemistry
- Receptors, Opioid, mu/metabolism
- Nociceptin Receptor
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Affiliation(s)
- Mark F. Bird
- Department of Cardiovascular Sciences, University of Leicester, Division of Anaesthesia, Critical Care and Pain Management, Leicester Royal Infirmary, Leicester, LE2 7LX, United Kingdom
| | - Maria Camilla Cerlesi
- Department of Medical Sciences, Section of Pharmacology and National Institute of Neuroscience, University of Ferrara, Ferrara, Italy
| | - Mark Brown
- Department of Cardiovascular Sciences, University of Leicester, Division of Anaesthesia, Critical Care and Pain Management, Leicester Royal Infirmary, Leicester, LE2 7LX, United Kingdom
| | - Davide Malfacini
- Department of Medical Sciences, Section of Pharmacology and National Institute of Neuroscience, University of Ferrara, Ferrara, Italy
| | - Vanessa Vezzi
- Department of Pharmacology, Istituto Superiore di Sanità, Rome, 00161, Italy
| | - Paola Molinari
- Department of Pharmacology, Istituto Superiore di Sanità, Rome, 00161, Italy
| | - Laura Micheli
- Department of Neuroscience, Psychology, Drug Research and Child Health—Neurofarba, Pharmacology and Toxicology Section, University of Florence, Florence, Italy
| | - Lorenzo Di Cesare Mannelli
- Department of Neuroscience, Psychology, Drug Research and Child Health—Neurofarba, Pharmacology and Toxicology Section, University of Florence, Florence, Italy
| | - Carla Ghelardini
- Department of Neuroscience, Psychology, Drug Research and Child Health—Neurofarba, Pharmacology and Toxicology Section, University of Florence, Florence, Italy
| | - Remo Guerrini
- Department of Chemical and Pharmaceutical Sciences and LTTA, University of Ferrara, Ferrara, Italy
| | - Girolamo Calò
- Department of Medical Sciences, Section of Pharmacology and National Institute of Neuroscience, University of Ferrara, Ferrara, Italy
| | - David G. Lambert
- Department of Cardiovascular Sciences, University of Leicester, Division of Anaesthesia, Critical Care and Pain Management, Leicester Royal Infirmary, Leicester, LE2 7LX, United Kingdom
- * E-mail:
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Vezzi V, Onaran HO, Molinari P, Guerrini R, Balboni G, Calò G, Costa T. Ligands raise the constraint that limits constitutive activation in G protein-coupled opioid receptors. J Biol Chem 2013; 288:23964-78. [PMID: 23836900 DOI: 10.1074/jbc.m113.474452] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Using a cell-free bioluminescence resonance energy transfer strategy we compared the levels of spontaneous and ligand-induced receptor-G protein coupling in δ (DOP) and μ (MOP) opioid receptors. In this assay GDP can suppress spontaneous coupling, thus allowing its quantification. The level of constitutive activity was 4-5 times greater at the DOP than at the MOP receptor. A series of opioid analogues with a common peptidomimetic scaffold displayed remarkable inversions of efficacy in the two receptors. Agonists that enhanced coupling above the low intrinsic level of the MOP receptor were inverse agonists in reducing the greater level of constitutive coupling of the DOP receptor. Yet the intrinsic activities of such ligands are identical when scaled over the GDP base line of both receptors. This pattern is in conflict with the predictions of the ternary complex model and the "two state" extensions. According to this theory, the order of spontaneous and ligand-induced coupling cannot be reversed if a shift of the equilibrium between active and inactive forms raises constitutive activation in one receptor type. We propose that constitutive activation results from a lessened intrinsic barrier that restrains spontaneous coupling. Any ligand, regardless of its efficacy, must enhance this constraint to stabilize the ligand-bound complexed form.
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Affiliation(s)
- Vanessa Vezzi
- Department of Pharmacology, Istituto Superiore di Sanità, 00161 Rome, Italy
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Molinari P, Vezzi V, Sbraccia M, Grò C, Riitano D, Ambrosio C, Casella I, Costa T. Morphine-like opiates selectively antagonize receptor-arrestin interactions. J Biol Chem 2010; 285:12522-35. [PMID: 20189994 DOI: 10.1074/jbc.m109.059410] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The addictive potential of opioids may be related to their differential ability to induce G protein signaling and endocytosis. We compared the ability of 20 ligands (sampled from the main chemical classes of opioids) to promote the association of mu and delta receptors with G protein or beta-arrestin 2. Receptor-arrestin binding was monitored by bioluminescence resonance energy transfer (BRET) in intact cells, where pertussis toxin experiments indicated that the interaction was minimally affected by receptor signaling. To assess receptor-G protein coupling without competition from arrestins, we employed a cell-free BRET assay using membranes isolated from cells expressing luminescent receptors and fluorescent Gbeta(1). In this system, the agonist-induced enhancement of BRET (indicating shortening of distance between the two proteins) was G alpha-mediated (as shown by sensitivity to pertussis toxin and guanine nucleotides) and yielded data consistent with the known pharmacology of the ligands. We found marked differences of efficacy for G protein and arrestin, with a pattern suggesting more restrictive structural requirements for arrestin efficacy. The analysis of such differences identified a subset of structures showing a marked discrepancy between efficacies for G protein and arrestin. Addictive opiates like morphine and oxymorphone exhibited large differences both at delta and mu receptors. Thus, they were effective agonists for G protein coupling but acted as competitive enkephalins antagonists (delta) or partial agonists (mu) for arrestin. This arrestin-selective antagonism resulted in inhibition of short and long term events mediated by arrestin, such as rapid receptor internalization and down-regulation.
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Affiliation(s)
- Paola Molinari
- Department of Pharmacology, Istituto Superiore di Sanità, Rome 00161, Italy
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