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Ahmed SS, Youssef AO, Mohamed EH, Attia MS. A highly selective optical sensor Eu-BINAM for assessment of high sensitivity cardiac troponin tumor marker in serum of cancer patients. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2023; 300:122887. [PMID: 37224630 DOI: 10.1016/j.saa.2023.122887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Revised: 05/12/2023] [Accepted: 05/13/2023] [Indexed: 05/26/2023]
Abstract
A novel, easy, touchy and selective spectrofluorimetric technique has been successfully applied for sensitive determination of High Sensitivity Cardiac Troponin (TNHS I) in the serum samples of patients suffering malignant tumors through the usage of optical sensor Eu3+-BINAM complex. The technique is primarily based on quenching of the Eu3+-BINAM complex's luminescence intensity upon introducing various concentrations of High Sensitivity Cardiac Troponin (TNHS I). The synthesis and characterization of the optical sensor was performed via absorption and emission. The sensor was also adapted to offer excitation at 394 nm in acetonitrile at pH 7.5. Concentration of High Sensitivity Cardiac Troponin (TNHS I) in serum samples was found to be proportional to the luminescence intensity quenching of the Eu3+-BINAM complex, most prominently at λem = 618 nm. The limit of the dynamic range is 4.26 × 10-4 to 2 ng/mL. The limit of detection and quantitation were calculated to be 1.35 and 4.10 ng/mL, respectively. The suggested analytical approach proved its applicability, simplicity and comparatively interference- free. The technique was effectively recruited to quantify High Sensitivity Cardiac Troponin (TNHS I) in human serum samples. The proposed technique could be further extended to evaluate some biomarkers associated with malignancy related diseases in human.
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Affiliation(s)
- Shahenda S Ahmed
- Analytical Chemistry Department, Faculty of Science, Ain Shams University, Cairo, Egypt
| | - Ahmed O Youssef
- Analytical Chemistry Department, Faculty of Science, Ain Shams University, Cairo, Egypt
| | - Ekram H Mohamed
- Pharmaceutical Chemistry Department, Faculty of Pharmacy, British University, Cairo, Egypt
| | - Mohamed S Attia
- Analytical Chemistry Department, Faculty of Science, Ain Shams University, Cairo, Egypt
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2
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Scharf MM, Zimmermann M, Wilhelm F, Stroe R, Waldhoer M, Kolb P. A Focus on Unusual ECL2 Interactions Yields β 2 -Adrenergic Receptor Antagonists with Unprecedented Scaffolds. ChemMedChem 2020; 15:882-890. [PMID: 32301583 PMCID: PMC7318225 DOI: 10.1002/cmdc.201900715] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 03/11/2020] [Indexed: 11/15/2022]
Abstract
The binding pockets of aminergic G protein-coupled receptors are often targeted by drugs and virtual screening campaigns. In order to find ligands with unprecedented scaffolds for one of the best-investigated receptors of this subfamily, the β2 -adrenergic receptor, we conducted a docking-based screen insisting that molecules would address previously untargeted residues in extracellular loop 2. We here report the discovery of ligands with a previously undescribed coumaran-based scaffold. Furthermore, we provide an analysis of the added value that X-ray structures in different conformations deliver for such docking screens.
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Affiliation(s)
- Magdalena M. Scharf
- Department of Pharmaceutical ChemistryPhilipps-University MarburgMarbacher Weg 635037MarburgGermany
| | | | - Florian Wilhelm
- InterAx BiotechPARK innovAARE5234VilligenSwitzerland
- Department of Biosystems Science and Engineering ETHETH ZürichMattenstrasse 264058BaselSwitzerland
| | - Raimond Stroe
- InterAx BiotechPARK innovAARE5234VilligenSwitzerland
- Department of Drug Design and PharmacologyUniversity of CopenhagenUniversitetsparken 22100CopenhagenDenmark
| | | | - Peter Kolb
- Department of Pharmaceutical ChemistryPhilipps-University MarburgMarbacher Weg 635037MarburgGermany
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3
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Boursier ME, Levin S, Zimmerman K, Machleidt T, Hurst R, Butler BL, Eggers CT, Kirkland TA, Wood KV, Friedman Ohana R. The luminescent HiBiT peptide enables selective quantitation of G protein-coupled receptor ligand engagement and internalization in living cells. J Biol Chem 2020; 295:5124-5135. [PMID: 32107310 DOI: 10.1074/jbc.ra119.011952] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 02/18/2020] [Indexed: 01/19/2023] Open
Abstract
G protein-coupled receptors (GPCRs) are prominent targets to new therapeutics for a range of diseases. Comprehensive assessments of their cellular interactions with bioactive compounds, particularly in a kinetic format, are imperative to the development of drugs with improved efficacy. Hence, we developed complementary cellular assays that enable equilibrium and real-time analyses of GPCR ligand engagement and consequent activation, measured as receptor internalization. These assays utilize GPCRs genetically fused to an N-terminal HiBiT peptide (1.3 kDa), which produces bright luminescence upon high-affinity complementation with LgBiT, an 18-kDa subunit derived from NanoLuc. The cell impermeability of LgBiT limits signal detection to the cell surface and enables measurements of ligand-induced internalization through changes in cell-surface receptor density. In addition, bioluminescent resonance energy transfer is used to quantify dynamic interactions between ligands and their cognate HiBiT-tagged GPCRs through competitive binding with fluorescent tracers. The sensitivity and dynamic range of these assays benefit from the specificity of bioluminescent resonance energy transfer and the high signal intensity of HiBiT/LgBiT without background luminescence from receptors present in intracellular compartments. These features allow analyses of challenging interactions having low selectivity or affinity and enable studies using endogenously tagged receptors. Using the β-adrenergic receptor family as a model, we demonstrate the versatility of these assays by utilizing the same HiBiT construct in analyses of multiple aspects of GPCR pharmacology. We anticipate that this combination of target engagement and proximal functional readout will prove useful to the study of other GPCR families and the development of new therapeutics.
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Affiliation(s)
| | - Sergiy Levin
- Promega Biosciences LLC, San Luis Obispo, California 93401
| | | | | | - Robin Hurst
- Promega Corporation, Fitchburg, Wisconsin 53711
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4
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Dantas de Araujo A, Wu C, Wu KC, Reid RC, Durek T, Lim J, Fairlie DP. Europium-Labeled Synthetic C3a Protein as a Novel Fluorescent Probe for Human Complement C3a Receptor. Bioconjug Chem 2017; 28:1669-1676. [DOI: 10.1021/acs.bioconjchem.7b00132] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Aline Dantas de Araujo
- Division of Chemistry and Structural Biology, Institute for Molecular
Bioscience, ‡Australian Research Council Centre of Excellence in Advanced Molecular
Imaging, Institute for Molecular Bioscience, and §Centre for Inflammation Disease Research, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Chongyang Wu
- Division of Chemistry and Structural Biology, Institute for Molecular
Bioscience, ‡Australian Research Council Centre of Excellence in Advanced Molecular
Imaging, Institute for Molecular Bioscience, and §Centre for Inflammation Disease Research, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Kai-Chen Wu
- Division of Chemistry and Structural Biology, Institute for Molecular
Bioscience, ‡Australian Research Council Centre of Excellence in Advanced Molecular
Imaging, Institute for Molecular Bioscience, and §Centre for Inflammation Disease Research, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Robert C. Reid
- Division of Chemistry and Structural Biology, Institute for Molecular
Bioscience, ‡Australian Research Council Centre of Excellence in Advanced Molecular
Imaging, Institute for Molecular Bioscience, and §Centre for Inflammation Disease Research, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Thomas Durek
- Division of Chemistry and Structural Biology, Institute for Molecular
Bioscience, ‡Australian Research Council Centre of Excellence in Advanced Molecular
Imaging, Institute for Molecular Bioscience, and §Centre for Inflammation Disease Research, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Junxian Lim
- Division of Chemistry and Structural Biology, Institute for Molecular
Bioscience, ‡Australian Research Council Centre of Excellence in Advanced Molecular
Imaging, Institute for Molecular Bioscience, and §Centre for Inflammation Disease Research, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - David P. Fairlie
- Division of Chemistry and Structural Biology, Institute for Molecular
Bioscience, ‡Australian Research Council Centre of Excellence in Advanced Molecular
Imaging, Institute for Molecular Bioscience, and §Centre for Inflammation Disease Research, The University of Queensland, Brisbane, Queensland 4072, Australia
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5
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Chaturvedi S, Kaul A, Hazari PP, Mishra AK. Mapping neuroreceptors with metal-labeled radiopharmaceuticals. MEDCHEMCOMM 2017; 8:855-870. [PMID: 30108802 PMCID: PMC6072260 DOI: 10.1039/c6md00610h] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Accepted: 02/07/2017] [Indexed: 01/27/2023]
Abstract
The growing epidemiological and economic burden of neurological diseases on society is tremendous. A correct and timely diagnosis can help in lowering the burden and improving the life quality of both the diseased person and the caretaker. Imaging of the brain (neuroimaging) using CT, MRI, and nuclear imaging methods can provide anatomical and functional information. Neuroreceptors are central to neurotransmission and neuromodulation in the CNS. In vivo imaging of receptors in the brain provides powerful tools for the functional study of the central nervous system (CNS) in normal or diseased states. Presently, PET imaging using non-metallic radiotracers dominates the imaging of neuroreceptors. Metal-based probes for SPECT and PET can be economical and logistically easier to use without compromising the information. This review focuses on the development of metallic radiotracers for (99mTc) SPECT and (68Ga) PET along with future directions based on the metallic probes developed for other imaging modalities namely MRI.
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Affiliation(s)
- S Chaturvedi
- Division of Cyclotron and Radiopharmaceutical Sciences , Institute of Nuclear Medicine and Allied Sciences , Brig. S.K. Mazumder Road , Delhi 110054 , India . ; ; ; Tel: +91 11 23095117
| | - A Kaul
- Division of Cyclotron and Radiopharmaceutical Sciences , Institute of Nuclear Medicine and Allied Sciences , Brig. S.K. Mazumder Road , Delhi 110054 , India . ; ; ; Tel: +91 11 23095117
| | - Puja P Hazari
- Division of Cyclotron and Radiopharmaceutical Sciences , Institute of Nuclear Medicine and Allied Sciences , Brig. S.K. Mazumder Road , Delhi 110054 , India . ; ; ; Tel: +91 11 23095117
| | - Anil K Mishra
- Division of Cyclotron and Radiopharmaceutical Sciences , Institute of Nuclear Medicine and Allied Sciences , Brig. S.K. Mazumder Road , Delhi 110054 , India . ; ; ; Tel: +91 11 23095117
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Abstract
Since their discovery, G protein-coupled receptors (GPCRs) constitute one of the most studied proteins leading to important discoveries and perspectives in terms of their biology and implication in physiology and pathophysiology. This is mostly linked to the remarkable advances in the development and application of the biophysical resonance energy transfer (RET)-based approaches, including bioluminescence and fluorescence resonance energy transfer (BRET and FRET, respectively). Indeed, BRET and FRET have been extensively applied to study different aspects of GPCR functioning such as their activation and regulation either statically or dynamically, in real-time and intact cells. Consequently, our view on GPCRs has considerably changed opening new challenges for the study of GPCRs in their native tissues in the aim to get more knowledge on how these receptors control the biological responses. Moreover, the technological aspect of this field of research promises further developments for robust and reliable new RET-based assays that may be compatible with high-throughput screening as well as drug discovery programs.
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Affiliation(s)
- Mohammed Akli Ayoub
- Biologie et Bioinformatique des Systèmes de Signalisation, Institut National de la Recherche Agronomique, UMR85, Unité Physiologie de la Reproduction et des Comportements; CNRS, UMR7247, Nouzilly, France; LE STUDIUM(®) Loire Valley Institute for Advanced Studies, Orléans, France.
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7
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Vernall AJ, Hill SJ, Kellam B. The evolving small-molecule fluorescent-conjugate toolbox for Class A GPCRs. Br J Pharmacol 2014; 171:1073-84. [PMID: 23734587 DOI: 10.1111/bph.12265] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Revised: 05/09/2013] [Accepted: 05/17/2013] [Indexed: 01/15/2023] Open
Abstract
The past decade has witnessed fluorescently tagged drug molecules gaining significant attraction in their use as pharmacological tools with which to visualize and interrogate receptor targets at the single-cell level. Additionally, one can generate detailed pharmacological information, such as affinity measurements, down to almost single-molecule detection limits. The now accepted utilization of fluorescence-based readouts in high-throughput/high-content screening provides further evidence that fluorescent molecules offer a safer and more adaptable substitute to radioligands in molecular pharmacology and drug discovery. One such drug-target family that has received considerable attention are the GPCRs; this review therefore summarizes the most recent developments in the area of fluorescent ligand design for this important drug target. We assess recently reported fluorescent conjugates by adopting a receptor-family-based approach, highlighting some of the strengths and weaknesses of the individual molecules and their subsequent use. This review adds further strength to the arguments that fluorescent ligand design and synthesis requires careful planning and execution; providing examples illustrating that selection of the correct fluorescent dye, linker length/composition and geographic attachment point to the drug scaffold can all influence the ultimate selectivity and potency of the final conjugate when compared with its unlabelled precursor. When optimized appropriately, the resultant fluorescent conjugates have been successfully employed in an array of assay formats, including flow cytometry, fluorescence microscopy, FRET and scanning confocal microscopy. It is clear that fluorescently labelled GPCR ligands remain a developing and dynamic research arena.
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Affiliation(s)
- Andrea J Vernall
- School of Pharmacy, Centre for Biomolecular Sciences, University of Nottingham, Nottingham, UK
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8
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Laurent S, Vander Elst L, Galaup C, Leygue N, Boutry S, Picard C, Muller RN. Bifunctional Gd(III) and Tb(III) chelates based on a pyridine-bis(iminodiacetate) platform, suitable optical probes and contrast agents for magnetic resonance imaging. CONTRAST MEDIA & MOLECULAR IMAGING 2014; 9:300-12. [DOI: 10.1002/cmmi.1576] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Revised: 09/20/2013] [Accepted: 09/29/2013] [Indexed: 11/12/2022]
Affiliation(s)
- Sophie Laurent
- NMR and Molecular Imaging Laboratory, Department of General, Organic and Biomedical Chemistry; Université de Mons; B-7000 Mons Belgium
| | - Luce Vander Elst
- NMR and Molecular Imaging Laboratory, Department of General, Organic and Biomedical Chemistry; Université de Mons; B-7000 Mons Belgium
| | - Chantal Galaup
- Université de Toulouse; UPS; Laboratoire de Synthèse et Physico-Chimie de Molécules d'Intérêt Biologique, SPCMIB; 118 route de Narbonne F-31062 Toulouse cedex 9 France
- CNRS; Laboratoire de Synthèse et Physico-Chimie de Molécules d'Intérêt Biologique, SPCMIB, UMR-5068; 118 Route de Narbonne F-31062 Toulouse cedex 9 France
| | - Nadine Leygue
- Université de Toulouse; UPS; Laboratoire de Synthèse et Physico-Chimie de Molécules d'Intérêt Biologique, SPCMIB; 118 route de Narbonne F-31062 Toulouse cedex 9 France
- CNRS; Laboratoire de Synthèse et Physico-Chimie de Molécules d'Intérêt Biologique, SPCMIB, UMR-5068; 118 Route de Narbonne F-31062 Toulouse cedex 9 France
| | - Sébastien Boutry
- NMR and Molecular Imaging Laboratory, Department of General, Organic and Biomedical Chemistry; Université de Mons; B-7000 Mons Belgium
- Center for Microscopy and Molecular Imaging (CMMI), Académie Wallonie-Bruxelles; B 6041 Gosselies Belgium
| | - Claude Picard
- Université de Toulouse; UPS; Laboratoire de Synthèse et Physico-Chimie de Molécules d'Intérêt Biologique, SPCMIB; 118 route de Narbonne F-31062 Toulouse cedex 9 France
- CNRS; Laboratoire de Synthèse et Physico-Chimie de Molécules d'Intérêt Biologique, SPCMIB, UMR-5068; 118 Route de Narbonne F-31062 Toulouse cedex 9 France
| | - Robert. N. Muller
- NMR and Molecular Imaging Laboratory, Department of General, Organic and Biomedical Chemistry; Université de Mons; B-7000 Mons Belgium
- Center for Microscopy and Molecular Imaging (CMMI), Académie Wallonie-Bruxelles; B 6041 Gosselies Belgium
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9
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Effects of a WLAN-based real time location system on outpatient contentment in a Level I trauma center. Int J Med Inform 2014; 83:19-26. [DOI: 10.1016/j.ijmedinf.2013.10.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Revised: 09/01/2013] [Accepted: 10/07/2013] [Indexed: 11/21/2022]
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10
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Kopra K, Kainulainen M, Mikkonen P, Rozwandowicz-Jansen A, Hänninen P, Härmä H. Multiparametric homogeneous method for identification of ligand binding to G protein-coupled receptors: receptor-ligand binding and β-arrestin assay. Anal Chem 2013; 85:2276-81. [PMID: 23330639 DOI: 10.1021/ac303215r] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Two homogeneous assay systems have been combined to provide a new cell-based functional assay. The assay can be used to identify ligand binding to β(2)-adrenergic receptors, but also the downstream response can be determined in the same assay. Both the quenching resonance energy transfer (QRET) and the DiscoveRx PathHunter assay formats allow the use of intact cells. The homogeneous QRET technique is a single-label approach based on nonspecific quenching of the time-resolved luminescence, enabling agonist and antagonist receptor binding measurements. The commercial PathHunter assay is in turn based on enzyme fragment complementation, which can be detected on the basis of chemiluminescence signal. In the PathHunter technology the enzyme complementation is recorded immediately downstream of agonist-induced receptor activation. The new multiparametric detection technology combines these two assay methods enabling the identification of agonist, and antagonist binding to the receptor, and the agonist-induced response. Using the QRET and the PathHunter methods a panel of β(2)-adrenergic receptor ligands (epinephrine, terbutaline, metaproterenol, salmeterol, propranolol, alprenolol, bisoprolol, ICI 118,551, and bucindolol) was tested to prove the assay performance. The signal-to-background ratio for tested ligands ranged from 5 to 11 and from 6 to 18 with QRET and PathHunter, respectively. Combined homogeneous assay technique can provide an informative method for screening purposes and an efficient way to monitor receptor-ligand interaction, thus separating agonist from antagonist.
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Affiliation(s)
- Kari Kopra
- Laboratory of Biophysics, Department of Cell Biology and Anatomy, Institute of Biomedicine, University of Turku, Turku, Finland.
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11
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Kopra K, Shweta, Martikkala E, Hänninen P, Petäjä-Repo U, Härmä H. A homogeneous single-label quenching resonance energy transfer assay for a δ-opioid receptor–ligand using intact cells. Analyst 2013; 138:4907-14. [DOI: 10.1039/c3an00736g] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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12
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Activation biosensor for G protein-coupled receptors: a FRET-based m1 muscarinic activation sensor that regulates G(q). PLoS One 2012; 7:e45651. [PMID: 23029161 PMCID: PMC3447775 DOI: 10.1371/journal.pone.0045651] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Accepted: 08/20/2012] [Indexed: 01/07/2023] Open
Abstract
We describe the design, construction and validation of a fluorescence sensor to measure activation by agonist of the m1 muscarinic cholinergic receptor, a prototypical class I Gq-coupled receptor. The sensor uses an established general design in which Förster resonance energy transfer (FRET) from a circularly permuted CFP mutant to FlAsH, a selectively reactive fluorescein, is decreased 15–20% upon binding of a full agonist. Notably, the sensor displays essentially wild-type capacity to catalyze activation of Gαq, and the purified and reconstituted sensor displays appropriate regulation of affinity for agonists by Gq. We describe the strategies used to increase the agonist-driven change in FRET while simultaneously maintaining regulatory interactions with Gαq, in the context of the known structures of Class I G protein-coupled receptors. The approach should be generally applicable to other Class I receptors which include numerous important drug targets.
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Baker JG, Adams LA, Salchow K, Mistry SN, Middleton RJ, Hill SJ, Kellam B. Synthesis and characterization of high-affinity 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene-labeled fluorescent ligands for human β-adrenoceptors. J Med Chem 2011; 54:6874-87. [PMID: 21870877 PMCID: PMC3188295 DOI: 10.1021/jm2008562] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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The growing practice of exploiting noninvasive fluorescence-based techniques to study G protein-coupled receptor pharmacology at the single cell and single molecule level demands the availability of high-quality fluorescent ligands. To this end, this study evaluated a new series of red-emitting ligands for the human β-adrenoceptor family. Upon the basis of the orthosteric ligands propranolol, alprenolol, and pindolol, the synthesized linker-modified congeners were coupled to the commercially available fluorophore BODIPY 630/650-X. This yielded high-affinity β-adrenoceptor fluorescent ligands for both the propranolol and alprenolol derivatives; however, the pindolol-based products displayed lower affinity. A fluorescent diethylene glycol linked propranolol derivative (18a) had the highest affinity (log KD of −9.53 and −8.46 as an antagonist of functional β2- and β1-mediated responses, respectively). Imaging studies with this compound further confirmed that it can be employed to selectively label the human β2-adrenoceptor in single living cells, with receptor-associated binding prevented by preincubation with the nonfluorescent β2-selective antagonist 3-(isopropylamino)-1-[(7-methyl-4-indanyl)oxy]butan-2-ol (ICI 118551) (J. Cardiovasc. Pharmacol.1983, 5, 430–437.)
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Affiliation(s)
- Jillian G Baker
- School of Pharmacy, Centre for Biomolecular Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom
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14
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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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15
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Leyris JP, Roux T, Trinquet E, Verdié P, Fehrentz JA, Oueslati N, Douzon S, Bourrier E, Lamarque L, Gagne D, Galleyrand JC, M'kadmi C, Martinez J, Mary S, Banères JL, Marie J. Homogeneous time-resolved fluorescence-based assay to screen for ligands targeting the growth hormone secretagogue receptor type 1a. Anal Biochem 2010; 408:253-62. [PMID: 20937574 DOI: 10.1016/j.ab.2010.09.030] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2010] [Revised: 08/19/2010] [Accepted: 09/20/2010] [Indexed: 11/19/2022]
Abstract
The growth hormone secretagogue receptor type 1a (GHS-R1a) belongs to class A G-protein-coupled receptors (GPCR). This receptor mediates pleiotropic effects of ghrelin and represents a promising target for dysfunctions of growth hormone secretion and energy homeostasis including obesity. Identification of new compounds which bind GHS-R1a is traditionally achieved using radioactive binding assays. Here we propose a new fluorescence-based assay, called Tag-lite binding assay, based on a fluorescence resonance energy transfer (FRET) process between a terbium cryptate covalently attached to a SNAP-tag fused GHS-R1a (SNAP-GHS-R1a) and a high-affinity red fluorescent ghrelin ligand. The long fluorescence lifetime of the terbium cryptate allows a time-resolved detection of the FRET signal. The assay was made compatible with high-throughput screening by using prelabeled cells in suspension under a 384-well plate format. K(i) values for a panel of 14 compounds displaying agonist, antagonist, or inverse agonist properties were determined using both the radioactive and the Tag-lite binding assays performed on the same batches of GHS-R1a-expressing cells. Compound potencies obtained in the two assays were nicely correlated. This study is the first description of a sensitive and reliable nonradioactive binding assay for GHS-R1a in a format amenable to high-throughput screening.
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Affiliation(s)
- Jean-Philippe Leyris
- Institut des Biomolécules Max Mousseron (IBMM), CNRS UMR 5247, Universities of Montpellier 1 and Montpellier 2, Faculty of Pharmacy, 15 avenue Charles Flahaut, BP 14491, 34093 Montpellier cedex 5, France
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16
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Härmä H, Rozwandowicz-Jansen A, Martikkala E, Frang H, Hemmilä I, Sahlberg N, Fey V, Perälä M, Hänninen P. A new simple cell-based homogeneous time-resolved fluorescence QRET technique for receptor-ligand interaction screening. ACTA ACUST UNITED AC 2009; 14:936-43. [PMID: 19684287 DOI: 10.1177/1087057109341657] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In this article, a single-label separation-free fluorescence technique is presented as a potential screening method for cell-based receptor antagonists and agonists.The time-resolved fluorescence technique, quenching resonance energy transfer (QRET), relies on a single-labeled binding partner in combination with a soluble quencher. The quencher efficiently suppresses the luminescence of the unbound labeled ligand, whereas the luminescence of the bound fraction is not affected. This approach allows the development of cell-based screening assays in a simple and cost-effective manner. The authors have applied the technique to the screening of beta(2)-adrenoreceptor (beta(2)AR) antagonists and agonists in intact human embryonic kidney HEK293(i) cells overexpressing human beta(2)-adrenergic receptors. Two antagonists (propranolol, alprenolol) and 2 agonists (metaproterenol, terbutaline) for beta(2)AR were investigated in a displacement assay using europium(III)-labeled pindolol ligand. The assay Z' values ranged from 0.68 to 0.78, the coefficient of variation was less than 10%, and the K(i) values were 19 nM for propranolol and alprenolol and 14 and 5.9 microM for metaproterenol and terbutaline, respectively. The QRET technique with beta(2)AR was also applied to LOPAC compound library screening, yielding nearly error-free recognition of known binders. This simple and cost-effective technique can be readily adapted to laboratory and industrial-scale screening.
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Affiliation(s)
- Harri Härmä
- Laboratory of Biophysics, University of Turku, Turku, Finland.
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