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L-DOPA and Droxidopa: From Force Field Development to Molecular Docking into Human β2-Adrenergic Receptor. Life (Basel) 2022; 12:life12091393. [PMID: 36143429 PMCID: PMC9501711 DOI: 10.3390/life12091393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Revised: 08/10/2022] [Accepted: 09/01/2022] [Indexed: 11/30/2022] Open
Abstract
The increasing interest in the molecular mechanism of the binding of different agonists and antagonists to β2-adrenergic receptor (β2AR) inactive and active states has led us to investigate protein–ligand interactions using molecular docking calculations. To perform this study, the 3.2 Å X-ray crystal structure of the active conformation of human β2AR in the complex with the endogenous agonist adrenaline has been used as a template for investigating the binding of two exogenous catecholamines to this adrenergic receptor. Here, we show the derivation of L-DOPA and Droxidopa OPLS all atom (AA) force field (FF) parameters via quantum mechanical (QM) calculations, molecular dynamics (MD) simulations in aqueous solutions of the two catecholamines and the molecular docking of both ligands into rigid and flexible β2AR models. We observe that both ligands share with adrenaline similar experimentally observed binding anchor sites, which are constituted by Asp113/Asn312 and Ser203/Ser204/Ser207 side chains. Moreover, both L-DOPA and Droxidopa molecules exhibit binding affinities comparable to that predicted for adrenaline, which is in good agreement with previous experimental and computational results. L-DOPA and Droxidopa OPLS AA FFs have also been tested by performing MD simulations of these ligands docked into β2AR proteins embedded in lipid membranes. Both hydrogen bonds and hydrophobic interaction networks observed over the 1 μs MD simulation are comparable with those derived from molecular docking calculations and MD simulations performed with the CHARMM FF.
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Aydın B, Gören MZ, Kanlı Z, Cabadak H. Cross-Talk of Cholinergic and β-Adrenergic Receptor Signalling in Chronic Myeloid Leukemia K562 Cells. Clin Exp Pharmacol Physiol 2022; 49:515-524. [PMID: 35088452 DOI: 10.1111/1440-1681.13627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 11/26/2021] [Accepted: 12/02/2021] [Indexed: 11/29/2022]
Abstract
In many studies on breast, skin, and intestinal cancers, beta-adrenergic receptor antagonists have been shown to inhibit cell proliferation and angiogenesis and increase apoptosis in cancers. Carbachol inhibits chronic myeloid leukemia K562 cell proliferation. Beta-blockers are known to inhibit cell progression. The aim of this study, explain the mechanism of action of beta-adrenergic receptors agonists and antagonists on apoptosis in chronic myeloid leukemia cells. We tried to determine the effect of combined treatment of beta-adrenergic and cholinergic drugs on Adrenergic β1 and β2 gene expression, cell proliferation and apoptosis in chronic myeloid leukemia K562 cells. Cell proliferation was evaluated by the BrdU incorporation kit. Caspase 3, 8, 9 activities were measured by the caspase-assay kit. Protein expression level detected by western blotting. We found that exposure to propranolol either by combination with carbachol facilitates additive effects on inhibition of caspase 3 and 8 expression in chronic myeloid leukemia K562 cells. But caspase 9 expression level was increased by propranolol alone or with propranolol and Carbachol combination. The combined therapy of cholinergic and adrenergic receptor drugs will decrease cell proliferation in K562 cells. This decrease in cell proliferation may be mediated by the mitochondrial dependent intrinsic apoptosis pathway.
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Affiliation(s)
- Banu Aydın
- Department of Biophysics, Marmara University, School of Medicine, Basic Medical Sciences Building, Maltepe, Istanbul, 34854, Turkey
| | - Mehmet Zafer Gören
- Department of Medical Pharmacology, Marmara University, School of Medicine, Basic Medical Sciences Building, Maltepe, Istanbul, 34854, Turkey
| | - Zehra Kanlı
- Department of Biophysics, Marmara University, School of Medicine, Basic Medical Sciences Building, Maltepe, Istanbul, 34854, Turkey
| | - Hülya Cabadak
- Department of Biophysics, Marmara University, School of Medicine, Basic Medical Sciences Building, Maltepe, Istanbul, 34854, Turkey
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Biswas AD, Catte A, Mancini G, Barone V. Analysis of L-DOPA and droxidopa binding to human β 2-adrenergic receptor. Biophys J 2021; 120:5631-5643. [PMID: 34767786 PMCID: PMC8715240 DOI: 10.1016/j.bpj.2021.11.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 10/28/2021] [Accepted: 11/03/2021] [Indexed: 12/29/2022] Open
Abstract
Over the last two decades, an increasing number of studies has been devoted to a deeper understanding of the molecular process involved in the binding of various agonists and antagonists to active and inactive conformations of β2-adrenergic receptor (β2AR). The 3.2 Å x-ray crystal structure of human β2AR active state in combination with the endogenous low affinity agonist adrenaline offers an ideal starting structure for studying the binding of various catecholamines to adrenergic receptors. We show that molecular docking of levodopa (L-DOPA) and droxidopa into rigid and flexible β2AR models leads for both ligands to binding anchor sites comparable to those experimentally reported for adrenaline, namely D113/N312 and S203/S204/S207 side chains. Both ligands have a hydrogen bond network that is extremely similar to those of noradrenaline and dopamine. Interestingly, redocking neutral and protonated versions of adrenaline to rigid and flexible β2AR models results in binding poses that are more energetically stable and distinct from the x-ray crystal structure. Similarly, lowest energy conformations of noradrenaline and dopamine generated by docking into flexible β2AR models had binding free energies lower than those of best poses in rigid receptor models. Furthermore, our findings show that L-DOPA and droxidopa molecules have binding affinities comparable to those predicted for adrenaline, noradrenaline, and dopamine, which are consistent with previous experimental and computational findings and supported by the molecular dynamics simulations of β2AR-ligand complexes performed here.
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Nikte SV, Sonar K, Tandale A, Joshi M, Sengupta D. Loss of a water-mediated network results in reduced agonist affinity in a β 2-adrenergic receptor clinical variant. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2021; 1869:140605. [PMID: 33453412 DOI: 10.1016/j.bbapap.2021.140605] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Revised: 12/19/2020] [Accepted: 01/07/2021] [Indexed: 11/26/2022]
Abstract
The β2-adrenergic receptor (β2AR) is a member of the G protein-coupled receptor (GPCR) family that is an important drug target for asthma and COPD. Clinical studies coupled with biochemical data have identified a critical receptor variant, Thr164Ile, to have a reduced response to agonist-based therapy, although the molecular mechanism underlying this seemingly "non-deleterious" substitution is not clear. Here, we couple molecular dynamics simulations with network analysis and free-energy calculations to identify the molecular determinants underlying the differential drug response. We are able to identify hydration sites in the transmembrane domain that are essential to maintain the integrity of the binding site but are absent in the variant. The loss of these hydration sites in the variant correlates with perturbations in the intra-protein interaction network and rearrangements in the orthosteric ligand binding site. In conjunction, we observe an altered binding and reduced free energy of a series of agonists, in line with experimental trends. Our work identifies a functional allosteric pathway connected by specific hydration sites in β2AR that has not been reported before and provides insight into water-mediated networks in GPCRs in general. Overall, the work is one of the first step towards developing variant-specific potent and selective agonists.
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Affiliation(s)
- Siddhanta V Nikte
- Physical Chemistry Division, National Chemical Laboratory, Pune 411 008, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201 002, India
| | - Krushna Sonar
- Physical Chemistry Division, National Chemical Laboratory, Pune 411 008, India
| | - Aditi Tandale
- Physical Chemistry Division, National Chemical Laboratory, Pune 411 008, India
| | - Manali Joshi
- Bioinformatics Centre, S. P. University, Pune 411 007, India.
| | - Durba Sengupta
- Physical Chemistry Division, National Chemical Laboratory, Pune 411 008, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201 002, India.
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5
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Tsvetanova NG, Trester-Zedlitz M, Newton BW, Riordan DP, Sundaram AB, Johnson JR, Krogan NJ, von Zastrow M. G Protein-Coupled Receptor Endocytosis Confers Uniformity in Responses to Chemically Distinct Ligands. Mol Pharmacol 2016; 91:145-156. [PMID: 27879340 DOI: 10.1124/mol.116.106369] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Accepted: 11/18/2016] [Indexed: 12/19/2022] Open
Abstract
The ability of chemically distinct ligands to produce different effects on the same G protein-coupled receptor (GPCR) has interesting therapeutic implications, but, if excessively propagated downstream, would introduce biologic noise compromising cognate ligand detection. We asked whether cells have the ability to limit the degree to which chemical diversity imposed at the ligand-GPCR interface is propagated to the downstream signal. We carried out an unbiased analysis of the integrated cellular response elicited by two chemically and pharmacodynamically diverse β-adrenoceptor agonists, isoproterenol and salmeterol. We show that both ligands generate an identical integrated response, and that this stereotyped output requires endocytosis. We further demonstrate that the endosomal β2-adrenergic receptor signal confers uniformity on the downstream response because it is highly sensitive and saturable. Based on these findings, we propose that GPCR signaling from endosomes functions as a biologic noise filter to enhance reliability of cognate ligand detection.
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Affiliation(s)
- Nikoleta G Tsvetanova
- Department of Psychiatry (N.G.T., M.T.-Z., M.Z.), Department of Cellular and Molecular Pharmacology (M.Z.), California Institute for Quantitative Biosciences (B.W.N., J.R.J., N.J.K.), and Lung Biology Center, Department of Medicine (A.B.S.), University of California, San Francisco, San Francisco, California; J. David Gladstone Institute, San Francisco, California (N.J.K.); and Department of Biochemistry, Stanford University, Stanford, California (D.P.R.)
| | - Michelle Trester-Zedlitz
- Department of Psychiatry (N.G.T., M.T.-Z., M.Z.), Department of Cellular and Molecular Pharmacology (M.Z.), California Institute for Quantitative Biosciences (B.W.N., J.R.J., N.J.K.), and Lung Biology Center, Department of Medicine (A.B.S.), University of California, San Francisco, San Francisco, California; J. David Gladstone Institute, San Francisco, California (N.J.K.); and Department of Biochemistry, Stanford University, Stanford, California (D.P.R.)
| | - Billy W Newton
- Department of Psychiatry (N.G.T., M.T.-Z., M.Z.), Department of Cellular and Molecular Pharmacology (M.Z.), California Institute for Quantitative Biosciences (B.W.N., J.R.J., N.J.K.), and Lung Biology Center, Department of Medicine (A.B.S.), University of California, San Francisco, San Francisco, California; J. David Gladstone Institute, San Francisco, California (N.J.K.); and Department of Biochemistry, Stanford University, Stanford, California (D.P.R.)
| | - Daniel P Riordan
- Department of Psychiatry (N.G.T., M.T.-Z., M.Z.), Department of Cellular and Molecular Pharmacology (M.Z.), California Institute for Quantitative Biosciences (B.W.N., J.R.J., N.J.K.), and Lung Biology Center, Department of Medicine (A.B.S.), University of California, San Francisco, San Francisco, California; J. David Gladstone Institute, San Francisco, California (N.J.K.); and Department of Biochemistry, Stanford University, Stanford, California (D.P.R.)
| | - Aparna B Sundaram
- Department of Psychiatry (N.G.T., M.T.-Z., M.Z.), Department of Cellular and Molecular Pharmacology (M.Z.), California Institute for Quantitative Biosciences (B.W.N., J.R.J., N.J.K.), and Lung Biology Center, Department of Medicine (A.B.S.), University of California, San Francisco, San Francisco, California; J. David Gladstone Institute, San Francisco, California (N.J.K.); and Department of Biochemistry, Stanford University, Stanford, California (D.P.R.)
| | - Jeffrey R Johnson
- Department of Psychiatry (N.G.T., M.T.-Z., M.Z.), Department of Cellular and Molecular Pharmacology (M.Z.), California Institute for Quantitative Biosciences (B.W.N., J.R.J., N.J.K.), and Lung Biology Center, Department of Medicine (A.B.S.), University of California, San Francisco, San Francisco, California; J. David Gladstone Institute, San Francisco, California (N.J.K.); and Department of Biochemistry, Stanford University, Stanford, California (D.P.R.)
| | - Nevan J Krogan
- Department of Psychiatry (N.G.T., M.T.-Z., M.Z.), Department of Cellular and Molecular Pharmacology (M.Z.), California Institute for Quantitative Biosciences (B.W.N., J.R.J., N.J.K.), and Lung Biology Center, Department of Medicine (A.B.S.), University of California, San Francisco, San Francisco, California; J. David Gladstone Institute, San Francisco, California (N.J.K.); and Department of Biochemistry, Stanford University, Stanford, California (D.P.R.)
| | - Mark von Zastrow
- Department of Psychiatry (N.G.T., M.T.-Z., M.Z.), Department of Cellular and Molecular Pharmacology (M.Z.), California Institute for Quantitative Biosciences (B.W.N., J.R.J., N.J.K.), and Lung Biology Center, Department of Medicine (A.B.S.), University of California, San Francisco, San Francisco, California; J. David Gladstone Institute, San Francisco, California (N.J.K.); and Department of Biochemistry, Stanford University, Stanford, California (D.P.R.)
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6
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Plazinska A, Plazinski W, Jozwiak K. Agonist binding by the β2-adrenergic receptor: an effect of receptor conformation on ligand association-dissociation characteristics. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2015; 44:149-63. [PMID: 25726162 PMCID: PMC4359354 DOI: 10.1007/s00249-015-1010-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Revised: 11/20/2014] [Accepted: 01/31/2015] [Indexed: 01/01/2023]
Abstract
The β2-adrenergic receptor (β2-AR), a G protein-coupled receptor (GPCR), is a physiologically important transmembrane protein that is a target for drugs used for treatment of asthma and cardiovascular diseases. Study of the first steps of ligand recognition and the molecular basis of ligand binding to the orthosteric site is essential for understanding the pharmacological properties of the receptor. In this work we investigated the characteristic features of the agonist association–dissociation process to and from the different conformational forms of β2-AR by use of advanced molecular modeling techniques. The investigation was focused on estimating the free energy profiles (FEPs) corresponding to the process of a full agonist ((R,R)-fenoterol) and an inverse agonist (carazolol) binding and unbinding to and from β2-AR. The two different conformational forms of β2-AR, i.e. active β2-AR–PDB: 3P0G and inactive β2-AR–PDB: 2RH1 were included in this stage of the study. We revealed several significant qualitative differences between FEPs characteristic of both conformational forms. Both FEPs suggest the existence of three transient binding sites in the extracellular domain of β2-AR. Comparison of the residues surrounding these transient binding sites in both β2-AR states revealed the importance of the aromatic residues F194, H932.64, H2966.58, and H178 (extracellular part of β2-AR) in the early stages of the binding process. In addition, slightly different exit and entry paths are preferred by the ligand molecule in the extracellular part of β2-AR, depending on the conformation of the receptor.
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Affiliation(s)
- Anita Plazinska
- Laboratory of Medicinal Chemistry and Neuroengineering, Department of Chemistry, Faculty of Pharmacy, Medical University of Lublin, W. Chodzki Str., 4a, 20-093, Lublin, Poland
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7
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Copik AJ, Baldys A, Nguyen K, Sahdeo S, Ho H, Kosaka A, Dietrich PJ, Fitch B, Raymond JR, Ford APDW, Button D, Milla ME. Isoproterenol acts as a biased agonist of the alpha-1A-adrenoceptor that selectively activates the MAPK/ERK pathway. PLoS One 2015; 10:e0115701. [PMID: 25606852 PMCID: PMC4301629 DOI: 10.1371/journal.pone.0115701] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2014] [Accepted: 11/26/2014] [Indexed: 11/24/2022] Open
Abstract
The α1A-AR is thought to couple predominantly to the Gαq/PLC pathway and lead to phosphoinositide hydrolysis and calcium mobilization, although certain agonists acting at this receptor have been reported to trigger activation of arachidonic acid formation and MAPK pathways. For several G protein-coupled receptors (GPCRs) agonists can manifest a bias for activation of particular effector signaling output, i.e. not all agonists of a given GPCR generate responses through utilization of the same signaling cascade(s). Previous work with Gαq coupling-defective variants of α1A-AR, as well as a combination of Ca2+ channel blockers, uncovered cross-talk between α1A-AR and β2-AR that leads to potentiation of a Gαq-independent signaling cascade in response to α1A-AR activation. We hypothesized that molecules exist that act as biased agonists to selectively activate this pathway. In this report, isoproterenol (Iso), typically viewed as β-AR-selective agonist, was examined with respect to activation of α1A-AR. α1A-AR selective antagonists were used to specifically block Iso evoked signaling in different cellular backgrounds and confirm its action at α1A-AR. Iso induced signaling at α1A-AR was further interrogated by probing steps along the Gαq /PLC, Gαs and MAPK/ERK pathways. In HEK-293/EBNA cells transiently transduced with α1A-AR, and CHO_α1A-AR stable cells, Iso evoked low potency ERK activity as well as Ca2+ mobilization that could be blocked by α1A-AR selective antagonists. The kinetics of Iso induced Ca2+ transients differed from typical Gαq- mediated Ca2+ mobilization, lacking both the fast IP3R mediated response and the sustained phase of Ca2+ re-entry. Moreover, no inositol phosphate (IP) accumulation could be detected in either cell line after stimulation with Iso, but activation was accompanied by receptor internalization. Data are presented that indicate that Iso represents a novel type of α1A-AR partial agonist with signaling bias toward MAPK/ERK signaling cascade that is likely independent of coupling to Gαq.
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Affiliation(s)
- Alicja. J. Copik
- Biochemical Pharmacology, Inflammation Discovery, Roche Palo Alto LLC, 3401 Hillview Drive, Palo Alto, CA 94304, United States of America
| | - Aleksander Baldys
- Nephrology Division, Department of Medicine, Medical University of South Carolina, and Medical and Research Services, Ralph H Johnson Veterans Affairs Medical Center, Charleston, South Carolina 29425, United States of America
| | - Khanh Nguyen
- Discovery Technologies, Roche Palo Alto LLC, 3401 Hillview Drive, Palo Alto, CA 94304, United States of America
| | - Sunil Sahdeo
- Biochemical Pharmacology, Inflammation Discovery, Roche Palo Alto LLC, 3401 Hillview Drive, Palo Alto, CA 94304, United States of America
| | - Hoangdung Ho
- Discovery Technologies, Roche Palo Alto LLC, 3401 Hillview Drive, Palo Alto, CA 94304, United States of America
| | - Alan Kosaka
- Discovery Technologies, Roche Palo Alto LLC, 3401 Hillview Drive, Palo Alto, CA 94304, United States of America
| | - Paul J. Dietrich
- Discovery Technologies, Roche Palo Alto LLC, 3401 Hillview Drive, Palo Alto, CA 94304, United States of America
| | - Bill Fitch
- Discovery Technologies, Roche Palo Alto LLC, 3401 Hillview Drive, Palo Alto, CA 94304, United States of America
| | - John R. Raymond
- Nephrology Division, Department of Medicine, Medical University of South Carolina, and Medical and Research Services, Ralph H Johnson Veterans Affairs Medical Center, Charleston, South Carolina 29425, United States of America
| | - Anthony P. D. W. Ford
- Biochemical Pharmacology, Inflammation Discovery, Roche Palo Alto LLC, 3401 Hillview Drive, Palo Alto, CA 94304, United States of America
| | - Donald Button
- Biochemical Pharmacology, Inflammation Discovery, Roche Palo Alto LLC, 3401 Hillview Drive, Palo Alto, CA 94304, United States of America
| | - Marcos E. Milla
- Biochemical Pharmacology, Inflammation Discovery, Roche Palo Alto LLC, 3401 Hillview Drive, Palo Alto, CA 94304, United States of America
- * E-mail:
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8
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van der Westhuizen ET, Breton B, Christopoulos A, Bouvier M. Quantification of ligand bias for clinically relevant β2-adrenergic receptor ligands: implications for drug taxonomy. Mol Pharmacol 2013; 85:492-509. [PMID: 24366668 DOI: 10.1124/mol.113.088880] [Citation(s) in RCA: 185] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The concepts of functional selectivity and ligand bias are becoming increasingly appreciated in modern drug discovery programs, necessitating more informed approaches to compound classification and, ultimately, therapeutic candidate selection. Using the β2-adrenergic receptor as a model, we present a proof of concept study that assessed the bias of 19 β-adrenergic ligands, including many clinically used compounds, across four pathways [cAMP production, extracellular signal-regulated kinase 1/2 (ERK1/2) activation, calcium mobilization, and receptor endocytosis] in the same cell background (human embryonic kidney 293S cells). Efficacy-based clustering placed the ligands into five distinct groups with respect to signaling signatures. In some cases, apparent functional selectivity originated from off-target effects on other endogenously expressed adrenergic receptors, highlighting the importance of thoroughly assessing selectivity of the responses before concluding receptor-specific ligand-biased signaling. Eliminating the nonselective compounds did not change the clustering of the 10 remaining compounds. Some ligands exhibited large differences in potency for the different pathways, suggesting that the nature of the receptor-effector complexes influences the relative affinity of the compounds for specific receptor conformations. Calculation of relative effectiveness (within pathway) and bias factors (between pathways) for each of the compounds, using an operational model of agonism, revealed a global signaling signature for all of the compounds relative to isoproterenol. Most compounds were biased toward ERK1/2 activation over the other pathways, consistent with the notion that many proximal effectors converge on this pathway. Overall, we demonstrate a higher level of ligand texture than previously anticipated, opening perspectives for the establishment of pluridimensional correlations between signaling profiles, drug classification, therapeutic efficacy, and safety.
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Affiliation(s)
- Emma T van der Westhuizen
- Department of Biochemistry and Institute for Research in Immunology and Cancer, University of Montreal, Montreal, Quebec, Canada (E.T.v.d.W., B.B., M.B.); and Drug Discovery Biology and Department of Pharmacology, Monash Institute for Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (E.T.v.d.W., A.C.)
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9
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Rajagopal S, Ahn S, Rominger DH, Gowen-MacDonald W, Lam CM, Dewire SM, Violin JD, Lefkowitz RJ. Quantifying ligand bias at seven-transmembrane receptors. Mol Pharmacol 2011; 80:367-77. [PMID: 21610196 DOI: 10.1124/mol.111.072801] [Citation(s) in RCA: 298] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Seven transmembrane receptors (7TMRs), commonly referred to as G protein-coupled receptors, form a large part of the "druggable" genome. 7TMRs can signal through parallel pathways simultaneously, such as through heterotrimeric G proteins from different families, or, as more recently appreciated, through the multifunctional adapters, β-arrestins. Biased agonists, which signal with different efficacies to a receptor's multiple downstream pathways, are useful tools for deconvoluting this signaling complexity. These compounds may also be of therapeutic use because they have distinct functional and therapeutic profiles from "balanced agonists." Although some methods have been proposed to identify biased ligands, no comparison of these methods applied to the same set of data has been performed. Therefore, at this time, there are no generally accepted methods to quantify the relative bias of different ligands, making studies of biased signaling difficult. Here, we use complementary computational approaches for the quantification of ligand bias and demonstrate their application to two well known drug targets, the β2 adrenergic and angiotensin II type 1A receptors. The strategy outlined here allows a quantification of ligand bias and the identification of weakly biased compounds. This general method should aid in deciphering complex signaling pathways and may be useful for the development of novel biased therapeutic ligands as drugs.
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Affiliation(s)
- Sudarshan Rajagopal
- Department of Medicine, Duke University Medical Center, Durham, North Carolina, USA
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10
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Martikkala E, Rozwandowicz-Jansen A, Hänninen P, Petäjä-Repo U, Härmä H. A homogeneous single-label time-resolved fluorescence cAMP assay. ACTA ACUST UNITED AC 2011; 16:356-62. [PMID: 21343601 DOI: 10.1177/1087057110397356] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
G-protein-coupled receptors (GPCRs) are an important class of pharmaceutical drug targets. Functional high-throughput GPCR assays are needed to test an increasing number of synthesized novel drug compounds and their function in signal transduction processes. Measurement of changes in the cyclic adenosine monophosphate (cAMP) concentration is a widely used method to verify GPCR activation in the adenylyl cyclase pathway. Here, a single-label time-resolved fluorescence and high-throughput screening (HTS)-feasible method was developed to measure changes in cAMP levels in HEK293(i) cells overexpressing either β(2)-adrenergic or δ-opioid receptors. In the quenching resonance energy transfer (QRET) technique, soluble quenchers reduce the signal of unbound europium(III)-labeled cAMP in solution, whereas the antibody-bound fraction is fluorescent. The feasibility of this homogeneous competitive assay was proven by agonist-mediated stimulation of receptors coupled to either the stimulatory G(s) or inhibitory G(i) proteins. The reproducibility of the assays was excellent, and Z' values exceeded 0.7. The dynamic range, signal-to-background ratio, and detection limit were compared with a commercial time-resolved fluorescence resonance energy transfer (TR-FRET) assay. In both homogeneous assays, similar assay parameters were obtained when adenylyl cyclase was stimulated directly by forskolin or via agonist-mediated activation of the G(s)-coupled β(2)AR. The advantage of using the single-label approach relates to the cost-effectiveness of the QRET system compared with the two-label TR-FRET assay as there is no need for labeling of two binding partners leading to reduced requirements for assay optimization.
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Affiliation(s)
- Eija Martikkala
- Laboratory of Biophysics and Medicity, University of Turku, Turku, Finland.
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11
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Bhattacharya S, Vaidehi N. Computational mapping of the conformational transitions in agonist selective pathways of a G-protein coupled receptor. J Am Chem Soc 2010; 132:5205-14. [PMID: 20235532 DOI: 10.1021/ja910700y] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The active state conformation of a G-protein coupled receptor (GPCR) is influenced by the chemical structure and the efficacy of the bound ligand. Insight into the active state conformation as well as the activation pathway for ligands with different efficacies is critical in designing functionally specific drugs for GPCRs. Starting from the crystal structure of the beta2-adrenergic receptor, we have used coarse grain computational methods to understand the modulation of the potential energy landscape of the receptor by two full agonists, two partial agonists, and an inverse agonist. Our coarse grain method involves a systematic conformational spanning of the receptor transmembrane helices followed by an energy minimization and ligand redocking in each sampled conformation. We have derived the activation pathways for several agonists and partial agonists, using a Monte Carlo algorithm, and these are in agreement with fluorescence spectroscopy measurements. The calculated pathways for the full agonists start with an energy downhill step leading to a stable intermediate followed by a barrier crossing leading to the active state. We find that the barrier crossing involves breaking of an interhelical hydrogen bond between helix5 and helix6, and polarization of the binding site residues by water facilitates the barrier crossing. The uphill step in the partial agonist salbutamol induced activation is distinct from full agonist norepinephrine, and originates from steric hindrance with the aromatic residues on helix6. Virtual ligand screening with the salbutamol-stabilized conformation shows enrichment of noncatechol agonists over the norepinephrine-stabilized conformation. Our computational method provides an unprecedented opportunity to derive hypotheses for experiments and also understand activation mechanisms in GPCRs.
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Affiliation(s)
- Supriyo Bhattacharya
- Division of Immunology, Beckman Research Institute of the City of Hope, 1500, East Duarte Road, Duarte, California 91010, USA
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12
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Novoseletsky VN, Pyrkov TV, Efremov RG. Analysis of hydrophobic interactions of antagonists with the beta2-adrenergic receptor. SAR AND QSAR IN ENVIRONMENTAL RESEARCH 2010; 21:37-55. [PMID: 20373213 DOI: 10.1080/10629360903560637] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The adrenergic receptors mediate a wide variety of physiological responses, including vasodilatation and vasoconstriction, heart rate modulation, and others. Beta-adrenergic antagonists ('beta-blockers') thus constitute a widely used class of drugs in cardiovascular medicine as well as in management of anxiety, migraine, and glaucoma. The importance of the hydrophobic effect has been evidenced for a wide range of beta-blocker properties. To better understand the role of the hydrophobic effect in recognition of beta-blockers by their receptor, we carried out a molecular docking study combined with an original approach to estimate receptor-ligand hydrophobic interactions. The proposed method is based on automatic detection of molecular fragments in ligands and the analysis of their interactions with receptors separately. A series of beta-blockers, based on phenylethanolamines and phenoxypropanolamines, were docked to the beta2-adrenoceptor binding site in the crystal structure. Hydrophobic complementarity between the ligand and the receptor was calculated using the PLATINUM web-server (http://model.nmr.ru/platinum). Based on the analysis of the hydrophobic match for molecular fragments of beta-blockers, we have developed a new scoring function which efficiently predicts dissociation constant (pKd) with strong correlations (r(2) approximately 0.8) with experimental data.
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Affiliation(s)
- V N Novoseletsky
- MM Shemyakin & Yu A Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Ul Miklukho-Maklaya, Moscow V-437, Russia.
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Katritch V, Reynolds KA, Cherezov V, Hanson MA, Roth CB, Yeager M, Abagyan R. Analysis of full and partial agonists binding to beta2-adrenergic receptor suggests a role of transmembrane helix V in agonist-specific conformational changes. J Mol Recognit 2009; 22:307-18. [PMID: 19353579 DOI: 10.1002/jmr.949] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The 2.4 A crystal structure of the beta(2)-adrenergic receptor (beta(2)AR) in complex with the high-affinity inverse agonist (-)-carazolol provides a detailed structural framework for the analysis of ligand recognition by adrenergic receptors. Insights into agonist binding and the corresponding conformational changes triggering G-protein coupled receptor (GPCR) activation mechanism are of special interest. Here we show that while the carazolol pocket captured in the beta(2)AR crystal structure accommodates (-)-isoproterenol and other agonists without steric clashes, a finite movement of the flexible extracellular part of TM-V helix (TM-Ve) obtained by receptor optimization in the presence of docked ligand can further improve the calculated binding affinities for agonist compounds. Tilting of TM-Ve towards the receptor axis provides a more complete description of polar receptor-ligand interactions for full and partial agonists, by enabling optimal engagement of agonists with two experimentally identified anchor sites, formed by Asp113/Asn312 and Ser203/Ser204/Ser207 side chains. Further, receptor models incorporating a flexible TM-V backbone allow reliable prediction of binding affinities for a set of diverse ligands, suggesting potential utility of this approach to design of effective and subtype-specific agonists for adrenergic receptors. Systematic differences in capacity of partial, full and inverse agonists to induce TM-V helix tilt in the beta(2)AR model suggest potential role of TM-V as a conformational "rheostat" involved in the whole spectrum of beta(2)AR responses to small molecule signals.
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Affiliation(s)
- Vsevolod Katritch
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
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Martikkala E, Lehmusto M, Lilja M, Rozwandowicz-Jansen A, Lunden J, Tomohiro T, Hänninen P, Petäjä-Repo U, Härmä H. Cell-based β2-adrenergic receptor–ligand binding assay using synthesized europium-labeled ligands and time-resolved fluorescence. Anal Biochem 2009; 392:103-9. [DOI: 10.1016/j.ab.2009.05.022] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2008] [Revised: 05/06/2009] [Accepted: 05/09/2009] [Indexed: 11/25/2022]
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Ambrosio C, Molinari P, Fanelli F, Chuman Y, Sbraccia M, Ugur O, Costa T. Different structural requirements for the constitutive and the agonist-induced activities of the beta2-adrenergic receptor. J Biol Chem 2005; 280:23464-74. [PMID: 15845544 DOI: 10.1074/jbc.m502901200] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We converted Ser-207, located in helix 5 of the beta2-adrenergic receptor, into all other natural amino acids. To quantify receptor activation as a receptor number-independent parameter and directly related to G(s) activation, we expressed the mutants in a G alpha(s)-tethered form. GTP exchange in such constructs is restricted to the fused alpha-subunit and is a linear function of the receptor concentration. Except S207R, all other mutants were expressed to a suitable level for investigation. All mutations reduced the binding affinities of the catechol agonists, epinephrine and isoproterenol, and the extent of reduction was unrelated to the residue ability to form hydrogen bonds. Instead, both enhancements and reductions of affinity were observed for the partial agonist halostachin and the antagonist pindolol. The mutations also enhanced and diminished ligand-induced receptor activation, but the effects were strictly ligand-specific. Polar residues such as Asp and His exalted the activation by full agonists but suppressed that induced by the partial agonists halostachin and dichloroisoproterenol. In contrast, hydrophobic residues such as Ile and Val augmented partial agonist activation. Only Ile and Lys produced a significant increase of constitutive activity. The effects on binding and activity were not correlated, nor did such parameters show any clear correlation with up to 78 descriptors of amino acid physicochemical properties. Our data question the idea that Ser-207 is exposed to the polar crevice in the unbound receptor. They also suggest that the active receptor form induced by a full agonist might be substantially different from that caused by constitutive activation.
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Affiliation(s)
- Caterina Ambrosio
- Department of Pharmacology, Istituto Superiore di Sanità, Viale Regina Elena 299, Rome 00161, Italy
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Krasel C, Bünemann M, Lorenz K, Lohse MJ. Beta-arrestin binding to the beta2-adrenergic receptor requires both receptor phosphorylation and receptor activation. J Biol Chem 2005; 280:9528-35. [PMID: 15634674 DOI: 10.1074/jbc.m413078200] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Homologous desensitization of beta2-adrenergic receptors has been shown to be mediated by phosphorylation of the agonist-stimulated receptor by G-protein-coupled receptor kinase 2 (GRK2) followed by binding of beta-arrestins to the phosphorylated receptor. Binding of beta-arrestin to the receptor is a prerequisite for subsequent receptor desensitization, internalization via clathrin-coated pits, and the initiation of alternative signaling pathways. In this study we have investigated the interactions between receptors and beta-arrestin2 in living cells using fluorescence resonance energy transfer. We show that (a) the initial kinetics of beta-arrestin2 binding to the receptor is limited by the kinetics of GRK2-mediated receptor phosphorylation; (b) repeated stimulation leads to the accumulation of GRK2-phosphorylated receptor, which can bind beta-arrestin2 very rapidly; and (c) the interaction of beta-arrestin2 with the receptor depends on the activation of the receptor by agonist because agonist withdrawal leads to swift dissociation of the receptor-beta-arrestin2 complex. This fast agonist-controlled association and dissociation of beta-arrestins from prephosphorylated receptors should permit rapid control of receptor sensitivity in repeatedly stimulated cells such as neurons.
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Affiliation(s)
- Cornelius Krasel
- Institute for Pharmacology and Toxicology, Versbacher Strasse 9, D-97078 Würzburg, Germany
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Rezmann-Vitti LA, Louis SNS, Nero TL, Jackman GP, Iakovidis D, Machida CA, Louis WJ. Agonist binding and activation of the rat beta(1)-adrenergic receptor: role of Trp(134(3.28)), Ser(190(4.57)) and Tyr(356(7.43)). Biochem Pharmacol 2004; 68:675-88. [PMID: 15276075 DOI: 10.1016/j.bcp.2004.04.021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2004] [Accepted: 04/27/2004] [Indexed: 11/21/2022]
Abstract
We investigated the role of Trp(134(3.28)), Ser(190(4.57)) and Tyr(356(7.43)) in agonist binding to, and activation of, the rat beta(1)-adrenergic receptor by comparing pK(i)s and functional responses of W134A, S190A and Y356F mutant receptors to wild type, all stably expressed in CHO cells. All three mutations significantly (P < 0.05) reduced adenylyl cyclase intrinsic activity (IA) compared to wild type in response to stimulation with both (-)-isoprenaline (53-88%) and (-)-RO363 (46-61%), and there was no significant correlation either between IA or pD(2) and pK(i) (P > 0.4), suggesting that changes in pK(i) were not sufficient to explain the fall in adenylyl cyclase activity. The most pronounced reduction in affinity (126-fold, P < 0.01) was displayed by xamoterol for the Y356F mutation, suggesting that xamoterol is able to directly interact with Tyr(356(7.43)). For the other agonists, the change in pK(i) values for the mutant receptors ranged from a 20-fold decrease to a 2-fold increase compared to the wild type. In a three-dimensional model of the rat beta(1)-adrenergic receptor, Trp(134(3.28)) and Tyr(356(7.43)) form part of a hydrophobic binding pocket involving residues in transmembrane helices 1, 2, 3 and 7. Our results suggest that Trp(134(3.28)) and Tyr(356(7.43)), together with Trp(353(7.40)), are able to interact via pi-pi interactions to stabilize the extracellular ends of transmembrane helices 3 and 7. Ser(190(4.57)) appears to be involved in a hydrogen bonding network, which maintains the spatial relationship between transmembrane helices 3 and 4. These interhelical interactions suggest that the three mutated residues stabilize the active receptor state by maintaining the proper packing of their respective transmembrane helix within the helix bundle, facilitating the appropriate movement and rotation of the transmembrane regions during the activation process.
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Affiliation(s)
- Linda A Rezmann-Vitti
- Department of Medicine, Clinical Pharmacology and Therapeutics Unit, The University of Melbourne, Austin Health, Heidelberg 3084, Vic., Australia
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Del Carmine R, Molinari P, Sbraccia M, Ambrosio C, Costa T. “Induced-Fit” Mechanism for Catecholamine Binding to the β2-Adrenergic Receptor. Mol Pharmacol 2004; 66:356-63. [PMID: 15266027 DOI: 10.1124/mol.66.2.356] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We engineered single and multiple mutations of serines 203, 204, and 207 in the fifth transmembrane domain of the beta(2)-adrenergic receptor, a region known to interact with hydroxyl groups of the catechol ring. Using such mutants, we measured the binding affinities of a panel of six catecholamine agonists differing only in the presence of substituents in the ethanolamine tail of the molecule. Although all ligands shared an intact catechol ring, they exhibited different losses of binding energy in response to the mutations. For all mutations, we found a clear relationship between the loss of binding caused by receptor mutation and that caused by the ligand modification. This indicates that the catechol ring and the ethanolamine tail synergistically influence their respective interactions when binding to the receptor. To verify this idea by a formal thermodynamic test, we used a double-mutant cycle analysis. We compared the effects of each receptor mutation with those induced by the modifications of the ligand's tail. Because such changes disrupt interactions occurring at different receptor domains, they should produce cumulative losses. In contrast, we found positive cooperativity between such effects. This means that the binding of each side of the catecholamine can enhance the binding of the other, through an effect that is probably propagated via a conformational change. We suggest that the agonist-binding pocket is not rigid but is dynamically formed as the ligand builds an increasing number of contacts with the receptor.
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Affiliation(s)
- Renata Del Carmine
- Department of Neuroscience, University of Rome, Tor Vergata, Rome, Italy
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Liapakis G, Chan WC, Papadokostaki M, Javitch JA. Synergistic contributions of the functional groups of epinephrine to its affinity and efficacy at the beta2 adrenergic receptor. Mol Pharmacol 2004; 65:1181-90. [PMID: 15102946 DOI: 10.1124/mol.65.5.1181] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The structural basis of ligand affinity can be approached by studying the interactions between a drug and receptor residues; the basis for efficacy is more complex and must involve activation-associated conformational changes. We have used wild-type (WT), a constitutively active mutant (CAM), and a "constitutively inactive" mutant beta2 adrenergic receptor (beta(2)AR) to investigate changes in the binding site that accompany binding and activation. The active state (R(*)) probably involves repositioning of at least some of the agonist-contact residues, thereby optimizing their interactions with agonist and resulting in a higher affinity for agonist. A comparison of the binding affinities of a series of phenethylamine derivatives for WT revealed a remarkable synergism between the various functional groups present in epinephrine. Binding affinity was essentially unchanged with addition of beta-OH, N-CH(3), or catechol OHs to phenethylamine. In contrast, when each of these same groups was added to the appropriate compound, already containing the other two groups, to make epinephrine, the increase in affinity was quite large (60- to 120-fold). An initial interaction between two or more contacts may stabilize an intermediate conformation of beta(2)AR, R', either by altering amino acid side chain rotamer conformations or by a more global conformational change involving the repositioning of transmembrane segments. The pattern of these effects was different in the CAM in that fewer interactions were required to observe the synergistic effect, consistent with the hypothesis that the CAM mutation enriches the proportion of receptors in R(*) or in R' from which R(*) is more readily assumed.
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Affiliation(s)
- George Liapakis
- Department of Pharmacology, Faculty of Medicine, University of Crete, Heraklion, Greece
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Beinborn M, Ren Y, Bläker M, Chen C, Kopin AS. Ligand function at constitutively active receptor mutants is affected by two distinct yet interacting mechanisms. Mol Pharmacol 2004; 65:753-60. [PMID: 14978254 DOI: 10.1124/mol.65.3.753] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
It has been proposed that mutations that induce constitutive activity in G-protein-coupled receptors (GPCRs) concomitantly enhance the ability of partial agonists to trigger second-messenger signaling. Using the cholecystokinin type 2 receptor (CCK-2R) as a model system, we have explored whether this association applies to a diverse set of activating mutations. Consistent with established principles, constitutively active CCK-2Rs resulting from amino acid substitutions within the third intracellular loop each systematically increased partial agonist activities versus corresponding wild-type values. In contrast, activating mutations within transmembrane domain segments near the extracellular loops led to an increase in efficacy of only a subset of compounds but decreased or did not change the function of others. When transmembrane domain amino acid substitutions were introduced in combination with intracellular amplifying mutations, observed changes in ligand activity were defined by the product of two discernible factors 1) systematic amplification caused by an equilibrium shift from the inactive to the active receptor conformation and 2) ligand-specific alterations in signaling, which probably result from mutation-induced changes in the putative binding pocket. These findings illustrate functional heterogeneity among GPCR mutants with ligand-independent signaling. A subgroup of activating mutations facilitates receptor isomerization to the active state and in parallel perturbs ligand receptor interactions. These mutants do not adhere to the previously proposed "hallmark criteria" of constitutive activity.
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Affiliation(s)
- Martin Beinborn
- Molecular Pharmacology Research Center, Department of Medicine, Tufts-New England Medical Center, Boston, MA 02111, USA
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Hoffmann C, Leitz MR, Oberdorf-Maass S, Lohse MJ, Klotz KN. Comparative pharmacology of human beta-adrenergic receptor subtypes--characterization of stably transfected receptors in CHO cells. Naunyn Schmiedebergs Arch Pharmacol 2004; 369:151-9. [PMID: 14730417 DOI: 10.1007/s00210-003-0860-y] [Citation(s) in RCA: 248] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2003] [Accepted: 12/03/2003] [Indexed: 10/26/2022]
Abstract
Although many beta1-receptor antagonists and beta2-receptor agonists have been used in pharmacotherapy for many years their pharmacological properties at all three known subtypes of beta-adrenergic receptors are not always well characterized. The aim of this study was, therefore, to provide comparative binding characteristics of agonists (epinephrine, norepinephrine, isoproterenol, fenoterol, salbutamol, salmeterol, terbutalin, formoterol, broxaterol) and antagonists (propranolol, alprenolol, atenolol, metoprolol, bisoprolol, carvedilol, pindolol, BRL 37344, CGP 20712, SR 59230A, CGP 12177, ICI 118551) at all three subtypes of human beta-adrenergic receptors in an identical cellular background. We generated Chinese hamster ovary (CHO) cells stably expressing the three beta-adrenergic receptor subtypes at comparable levels. We characterized these receptor subtypes and analyzed the affinity of routinely used drugs as well as experimental compounds in competition binding studies, using the non-selective antagonist 125I-cyanopindolol as a radioligand. Furthermore, we analyzed the beta-receptor-mediated adenylyl cyclase activity in isolated membranes from these cell lines. The results from our experiments show that all compounds exhibit distinct patterns of selectivity and activity at the three beta-receptor subtypes. In particular, a number of beta2- or beta3-receptor agonists that are inverse agonists at the other subtypes were identified. In addition, beta1-receptor antagonists with agonistic activity at beta2- and beta3-receptors were found. These specific mixtures of agonism, antagonism, and inverse agonism at different subtypes may have important implications for the therapeutic use of the respective compounds.
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Affiliation(s)
- C Hoffmann
- Institut für Pharmakologie und Toxikologie, Universität Würzburg, Versbacher Strasse 9, 97078 Würzburg, Germany
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Alvarez Arias D, Navenot JM, Zhang WB, Broach J, Peiper SC. Constitutive activation of CCR5 and CCR2 induced by conformational changes in the conserved TXP motif in transmembrane helix 2. J Biol Chem 2003; 278:36513-21. [PMID: 12837756 DOI: 10.1074/jbc.m303739200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
CCR5 is a G protein-coupled receptor for RANTES, MIP-1alpha, MIP-1beta, and MCP-2 that functions as the front line coreceptor for human immunodeficiency virus type 1 infection. To elucidate the mechanism for CCR5 activation, this coreceptor was expressed in yeast coupled to the pheromone response pathway and a constitutively active mutant (CAM) was derived by random mutagenesis. Conversion of Thr-82 in the highly conserved TXP motif in transmembrane helix 2 to Pro, His, Tyr, Arg, or Lys conferred autonomous signaling activity in yeast and mammalian cells. This substitution also imparted constitutive signaling to CCR2 in yeast and mammalian cells, but not CCR1, CCR3, CCR4, CXCR2, or CXCR4. The CCR5-CAM, but not the CCR2-CAM had a reduction in ligand binding affinity. Whereas the amplitude of calcium mobilization induced by RANTES stimulation was lower in the CCR5-CAM than the wild-type (WT) receptor, MCP-1 induced a higher signal in the CCR2-CAM than in CCR2-WT. The chemotactic response of CCR5-CAM(T82P) to RANTES was similar to that of CCR5-WT, but CCR5-CAM(T82K) was dramatically decreased. The chemotactic response of CCR2-WT and CCR2-CAM(T94K) were similar. These findings extend insight into the role of the TXP motif in the mechanism for CCR5 signaling. CCR2, the receptor most closely genetically related to CCR5, shared a similar signaling mechanism, but other receptors containing the TXP motif did not. The expression of CCR5 and CCR2 in yeast and the availability of variants with autonomous signaling represent critical tools for characterizing receptor antagonists and developing approaches to block their role in human diseases.
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Affiliation(s)
- Diana Alvarez Arias
- Department of Pathology, Medical College of Georgia, Augusta, Georgia 30912, USA
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