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Ho JH, Stahl EL, Schmid CL, Scarry SM, Aubé J, Bohn LM. G protein signaling-biased agonism at the κ-opioid receptor is maintained in striatal neurons. Sci Signal 2018; 11:11/542/eaar4309. [PMID: 30087177 DOI: 10.1126/scisignal.aar4309] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Biased agonists of G protein-coupled receptors may present a means to refine receptor signaling in a way that separates side effects from therapeutic properties. Several studies have shown that agonists that activate the κ-opioid receptor (KOR) in a manner that favors G protein coupling over β-arrestin2 recruitment in cell culture may represent a means to treat pain and itch while avoiding sedation and dysphoria. Although it is attractive to speculate that the bias between G protein signaling and β-arrestin2 recruitment is the reason for these divergent behaviors, little evidence has emerged to show that these signaling pathways diverge in the neuronal environment. We further explored the influence of cellular context on biased agonism at KOR ligand-directed signaling toward G protein pathways over β-arrestin-dependent pathways and found that this bias persists in striatal neurons. These findings advance our understanding of how a G protein-biased agonist signal differs between cell lines and primary neurons, demonstrate that measuring [35S]GTPγS binding and the regulation of adenylyl cyclase activity are not necessarily orthogonal assays in cell lines, and emphasize the contributions of the environment to assessing biased agonism.
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Affiliation(s)
- Jo-Hao Ho
- Departments of Molecular Medicine and Neuroscience, The Scripps Research Institute, Jupiter, FL 33458, USA
| | - Edward L Stahl
- Departments of Molecular Medicine and Neuroscience, The Scripps Research Institute, Jupiter, FL 33458, USA
| | - Cullen L Schmid
- Departments of Molecular Medicine and Neuroscience, The Scripps Research Institute, Jupiter, FL 33458, USA
| | - Sarah M Scarry
- UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Jeffrey Aubé
- UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Laura M Bohn
- Departments of Molecular Medicine and Neuroscience, The Scripps Research Institute, Jupiter, FL 33458, USA.
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Meier E, Schousboe A, Belhage B. Procedure for calculation of potency and efficacy for ligands acting on Gs- and Gi-coupled receptors. Neurochem Res 2012; 37:2767-75. [PMID: 23011203 DOI: 10.1007/s11064-012-0870-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Revised: 07/26/2012] [Accepted: 08/08/2012] [Indexed: 11/29/2022]
Abstract
Structure activity relationship (SAR) analyses of pharmacological data of compounds constitute an important part of the discovery process in the design of new drug candidates with improved pharmacological properties. In particular G-Protein Coupled Receptors (GPCRs) associated with the cAMP second messenger systems G(s) and G(i) have constituted one of the most widely used basis for pharmacological in vitro assays for assessing functional receptor effects. Such assays are based on Radio Immuno Assay (RIA) analysis to measure the cellular cAMP concentration as readout of receptor activation. It appears, however, to be a common practice to omit the use of cAMP standard curves to transform the measured signals (cpm or cps) into cAMP concentrations on which estimations of potencies (EC(50) values) and efficacies (E(MAX) values) in G(s) and G(i) coupled receptor stimulation are based. Such practice may lead to significant errors as compounds mediating their effects via G(s) coupled receptors may appear more potent and efficacious than they actually are. Contrary, compounds mediating their effects via G(i) coupled receptors may appear less potent and efficacious than they are in reality. Potency rank orders will therefore change considerably, when estimations are based on incorrect calculation of the original experimental results. Thus, the only correct way to calculate effect data on which to base E(MAX) and EC(50) estimations is to use cAMP concentrations derived from transformation of the measured signals (cpm or cps) using cAMP standard curves. The present work outlines the mathematical procedures by which such transformations are to be performed.
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Affiliation(s)
- Eddi Meier
- NordicScienceAdvice I/S, Bringebakken 88, 3500 Værløse, Denmark.
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Hill SJ, Williams C, May LT. Insights into GPCR pharmacology from the measurement of changes in intracellular cyclic AMP; advantages and pitfalls of differing methodologies. Br J Pharmacol 2011; 161:1266-75. [PMID: 21049583 DOI: 10.1111/j.1476-5381.2010.00779.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
It is clear that the G protein-coupled receptor family play a key role in the pharmaceutical industry, with a significant proportion of approved drugs targeting this protein class. While our growing understanding of the complexity of G protein-coupled receptor pharmacology is playing a key role in the future success of these endeavours, with allosteric mechanisms now well integrated into the industrial community and G protein-independent signalling mechanisms establishing themselves as novel phenomenon to be exploited, it is still possible to underestimate the complexity of G protein signal transduction mechanisms and the impact that inappropriate study of these mechanisms can have on data interpretation. In this manuscript we review different approaches to measuring the cAMP signal transduction pathway, with particular emphasis on key parameters influencing the data quality and biological relevance.
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Affiliation(s)
- Stephen J Hill
- Institute of Cell Signalling, School of Biomedical Sciences, Medical School, Queen's Medical Centre, Nottingham, UK.
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A high-throughput screening system for G-protein-coupled receptors using β-lactamase enzyme complementation technology. Acta Pharmacol Sin 2010; 31:1618-24. [PMID: 21102483 PMCID: PMC4002942 DOI: 10.1038/aps.2010.154] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Aim: To establish a system for monitoring the activation of G-protein-coupled receptors (GPCRs) using β-lactamase enzyme fragment complementation (EFC) technology. Methods: Two inactive β-lactamase deletion fragments, bla(a) and bla(b), were fused to β-arrestin and GPCR, respectively. A stable cell line named HEK/293-β2a2, which expressed two fusion proteins, GPCR/bla(b) and β-arrestin2/bla(a), was generated under antibiotic selection. A natural compound library of high performance liquid chromatography (HPLC)-fractionated samples from the ethanol extracts of Chinese medicinal herbs was used for high-throughput screening (HTS) of β2-adrenoceptor (β2AR) agonists against the cell line HEK/293-β2a2. The interested hits were validated by the measurement of second-messenger cyclic adenosine monophosphate (cAMP) production. Results: The stable cell line HEK/293-β2a2 responded to β2AR agonist/antagonist in a dose-dependent manner. The EC50 value obtained for isoproterenol was 15.5 nmol/L, and the IC50 value obtained for propranolol was 51.9 nmol/L. Furthermore, HTS was performed to identify β2AR agonists from the natural compound library we established. The Z′ factor value was determined to be 0.68. Three hits were identified from primary screening and found to be as potent as isoproterenol in a cAMP assay. Conclusion: A cell-based high-throughput functional assay was established to directly monitor the activation of GPCRs based on the interaction between agonist-activated GPCR and β-arrestin using β-lactamase EFC technology, which can be used to search for leads in the natural compound library.
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Abstract
Modulators of G protein-coupled receptors (GPCRs) form a key area for the pharmaceutical industry, representing approximately 27% of all Food and Drug Administration (FDA)-approved drugs. Consequently, there are a wide variety of in vitro plate-based screening technologies that enable the measurement of compound affinity, potency, and efficacy for almost every type of GPCR. However, to maximize success it is prudent to ensure that (i) the most suitable assay formats are identified, (ii) they are configured optimally to detect the desired compound activity, and (iii) that they form a basis for predicting clinical effects. To achieve this, an understanding of the pathways and mechanisms of receptor activation relevant to the disease mechanism, as well as the benefits and/or limitations of the specific techniques, is key.
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Kool J, van Marle A, Hulscher S, Selman M, van Iperen DJ, van Altena K, Gillard M, Bakker RA, Irth H, Leurs R, Vermeulen NPE. A flow-through fluorescence polarization detection system for measuring GPCR-mediated modulation of cAMP production. ACTA ACUST UNITED AC 2008; 12:1074-83. [PMID: 18087072 DOI: 10.1177/1087057107308881] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
A flow-through fluorescence polarization (FP) detection system that makes use of a novel high-performance liquid chromatography (HPLC) fluorescence detector modified with polarization filters was developed. This flow-through FP detection system was evaluated by using a novel and very cost-effective bioassay for cyclic adenosine monophosphate (cAMP). The bioassay was first evaluated and optimized in an FP plate reader format and subsequently in a flow-through bioassay setup. The principle of the bioassay is based on the competition of cAMP and a fluorescent cAMP derivative for the cAMP binding domain of protein kinase A. cAMP could accurately be determined over a range of 0.8 to 30 pmol/well in the plate reader FP assay and over a range of 0.3 to 50 pmol/well in the flow-through FP assay setup. High Z' factors (i.e., 0.89 for the plate reader and 0.93 for the flow-through FP cAMP assay, respectively) indicated robust assays. Finally, functional cAMP signaling of the human histamine H(3) G-protein-coupled receptor (GPCR) in cell cultures was measured with both assay formats with good sensitivities and assay windows. The pEC(50) values obtained in both assay formats were in accordance with those obtained with standard methods. The flow-through FP detection system could thus be used as a cost-effective alternative to FP plate reader assays. Moreover, the novel flow-through FP detection system for cAMP constitutes a good analytical tool to be used in the GPCR research field as an alternative to the use of FP plate readers or radioactive laboratories nowadays used for cAMP measurements.
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Affiliation(s)
- Jeroen Kool
- LACDR-Division of Molecular Toxicology, Department of Chemistry and Pharmaceutical Sciences, Vrije Universiteit Amsterdam, The Netherlands
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Strachan RT, Ferrara G, Roth BL. Screening the receptorome: an efficient approach for drug discovery and target validation. Drug Discov Today 2006; 11:708-16. [PMID: 16846798 DOI: 10.1016/j.drudis.2006.06.012] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2006] [Revised: 06/02/2006] [Accepted: 06/16/2006] [Indexed: 11/18/2022]
Abstract
The receptorome, comprising at least 5% of the human genome, encodes receptors that mediate the physiological, pathological and therapeutic responses to a vast number of exogenous and endogenous ligands. Not surprisingly, the majority of approved medications target members of the receptorome. Several in silico and physical screening approaches have been devised to mine the receptorome efficiently for the discovery and validation of molecular targets for therapeutic drug discovery. Receptorome screening has also been used to discover, and thereby avoid, the molecular targets responsible for serious and unforeseen drug side effects.
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Affiliation(s)
- Ryan T Strachan
- Department of Biochemistry, Comprehensive Cancer Center and NIMH Psychoactive Drug Screening Program, Case Western Reserve University Medical School, Cleveland, OH 44106, USA
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Nicholson JR, Kohler G, Schaerer F, Senn C, Weyermann P, Hofbauer KG. Peripheral administration of a melanocortin 4-receptor inverse agonist prevents loss of lean body mass in tumor-bearing mice. J Pharmacol Exp Ther 2006; 317:771-7. [PMID: 16436498 DOI: 10.1124/jpet.105.097725] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cachexia affects many different chronically ill patient populations, including those with cancer. It results in loss of body weight, particularly of lean body mass (LBM), and is estimated to be responsible for over 20% of all cancer-related deaths. Currently, available drugs are ineffective, and new therapies are urgently needed. Melanocortin 4-receptor (MC4-R) blockade has been shown recently to be effective in preventing cancer cachexia in rodent models. In the present study, we have tested a MC4-R blocker, ML00253764 [2-{2-[2-(5-bromo-2-methoxyphenyl)-ethyl]-3-fluorophenyl}-4,5-dihydro-1H-imidazolium hydrochloride] (Vos et al., 2004), in vitro and in vivo. In membranes of human embryonic kidney 293 cells expressing human MC4-R, ML00253764 displaced [Nle(4), d-Phe(7)]-alpha-melanocyte-stimulating hormone binding with an IC(50) of 0.32 microM. At concentrations above 1 microM, ML00253764 decreased cAMP accumulation (maximal reduction of -20%) indicative of inverse agonist activity. ML00253764 was administered twice daily (15 mg/kg s.c.) for 13 days to C57BL6 mice bearing s.c. Lewis lung carcinoma tumors. Food intake and body weight were measured, and body composition was assessed using magnetic resonance relaxometry. ML00253764 stimulated light-phase food intake relative to vehicle-treated controls (p < 0.05), although no effect was observed on 24-h food intake. During the 21 days of the experiment, the LBM of tumor vehicle-treated mice decreased (p < 0.05). In contrast, the tumor-bearing mice treated with ML00253764 maintained their LBM. These data support the view that MC4-R blockade may be a suitable approach for the treatment of cancer cachexia and that MC4-R inverse agonists may have potential as drug candidates.
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Affiliation(s)
- Janet R Nicholson
- Applied Pharmacology, Biozentrum, University of Basel, Klingelbergstrasse 50, CH-4056 Basel, Switzerland
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Abstract
The number of technologies that enable high-throughput functional screening of G-protein-coupled receptors has expanded markedly over the past 5 years. Consequently, choosing the most appropriate technology can be a daunting task, particularly for Gi- or Gs-coupled receptors. The most common systems for cyclic AMP detection are reviewed, highlighting the practical and theoretical aspects that are important in their application to high-throughput screening. Current technologies can do the job, but it is likely that the future may require development of technologies that provide even greater biological information.
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Affiliation(s)
- Christine Williams
- Hit Discovery Group, Pfizer Global Research and Development, Ramsgate Road, Sandwich, Kent CT13 9NJ, UK.
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