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Gin A, Nguyen PD, Melzer JE, Li C, Strzelinski H, Liggett SB, Su J. Label-free, real-time monitoring of membrane binding events at zeptomolar concentrations using frequency-locked optical microresonators. Nat Commun 2024; 15:7445. [PMID: 39198447 PMCID: PMC11358326 DOI: 10.1038/s41467-024-51320-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Accepted: 08/06/2024] [Indexed: 09/01/2024] Open
Abstract
G-protein coupled receptors help regulate cellular function and communication, and are targets of small molecule drug discovery efforts. Conventional techniques to probe these interactions require labels and large amounts of receptor to achieve satisfactory sensitivity. Here, we use frequency-locked optical microtoroids for label-free characterization of membrane interactions in vitro at zeptomolar concentrations for the kappa opioid receptor and its native agonist dynorphin A 1-13, as well as big dynorphin (dynorphin A and dynorphin B) using a supported biomimetic membrane. The measured affinity of the agonist dynorphin A 1-13 to the κ-opioid receptor was also measured and found to be 3.1 nM. Radioligand assays revealed a dissociation constant in agreement with this value (1.1 nM). The limit of detection for the κOR/DynA 1-13 was calculated as 180 zM. The binding of Cholera Toxin B-monosialotetrahexosyl ganglioside was also monitored in real-time and an equilibrium dissociation constant of 1.53 nM was found. Our biosensing platform provides a method for highly sensitive real-time characterization of membrane embedded protein binding kinetics that is rapid and label-free, for drug discovery and toxin screening among other applications.
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Affiliation(s)
- Adley Gin
- Wyant College of Optical Sciences, The University of Arizona, Tucson, AZ, 85721, USA
| | - Phuong-Diem Nguyen
- Department of Biomedical Engineering, The University of Arizona, Tucson, AZ, 85721, USA
| | - Jeffrey E Melzer
- Wyant College of Optical Sciences, The University of Arizona, Tucson, AZ, 85721, USA
| | - Cheng Li
- Wyant College of Optical Sciences, The University of Arizona, Tucson, AZ, 85721, USA
| | - Hannah Strzelinski
- Department of Medicine, University of South Florida Morsani College of Medicine, Tampa, FL, 33612, USA
| | - Stephen B Liggett
- Department of Medicine, University of South Florida Morsani College of Medicine, Tampa, FL, 33612, USA
| | - Judith Su
- Wyant College of Optical Sciences, The University of Arizona, Tucson, AZ, 85721, USA.
- Department of Biomedical Engineering, The University of Arizona, Tucson, AZ, 85721, USA.
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Servant G, Kenakin T. A Pharmacological perspective on the temporal properties of sweeteners. Pharmacol Res 2024; 204:107211. [PMID: 38744400 DOI: 10.1016/j.phrs.2024.107211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/20/2024] [Revised: 05/06/2024] [Accepted: 05/09/2024] [Indexed: 05/16/2024]
Abstract
Several non-caloric sweeteners exhibit a delay in sweetness onset and a sweetness linger after sampling. These temporal properties are thought to be the result of non-specific interactions with cell membranes and proteins in the oral cavity. Data and analysis presented in this report also support the potential involvement of receptor affinity and binding kinetics to this phenomenon. In general, affected sweeteners exhibit distinctly higher binding affinity compared to carbohydrate sweeteners, which do not have temporal issues. In addition, binding kinetic simulations illustrate much slower receptor binding association and dissociation kinetics for a set of non-caloric sweeteners presenting temporal issues, in comparison to carbohydrate sweeteners. So, the higher affinity of some non-caloric sweeteners, dictating lower use levels, and affecting binding kinetics, could contribute to their delay and linger in sweetness perception. Simple pharmacology principles could explain, at least in part, some of the temporal issues of sweeteners.
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Affiliation(s)
- Guy Servant
- dsm-firmenich, 10636 Scripps Summit Court #201, San Diego, CA 92131, USA.
| | - Terry Kenakin
- Department of Pharmacology, University of North Carolina School of Medicine, 120 Mason Farm Rd., 4042 Genetic Medicine CB #7365, Chapel Hill, NC 27599, USA
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Power ME, Fernandez NR, Oni OP, Kalia A, Rourke JL. The non-nutritive sweetener sucralose increases β-arrestin signaling at the constitutively active orphan G protein-coupled receptor GPR52. Can J Physiol Pharmacol 2024; 102:116-127. [PMID: 37748201 DOI: 10.1139/cjpp-2023-0199] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/27/2023]
Abstract
Non-nutritive sweeteners are popular food additives owing to their low caloric density and powerful sweetness relative to natural sugars. Their lack of metabolism contributes to evidence proclaiming their safety, yet several studies contradict this, demonstrating that sweeteners activate sweet taste G protein-coupled receptors (GPCRs) and elicit deleterious metabolic functions through unknown mechanisms. We hypothesize that activation of GPCRs, particularly orphan receptors due to their abundance in metabolically active tissues, contributes to the biological activity of sweeteners. We quantified the response of 64 orphans to the sweeteners saccharin and sucralose using a high-throughput β-arrestin-2 recruitment assay (PRESTO-Tango). GPR52 was the sole receptor that significantly responded to a mixture of sucralose and saccharin. Subsequent experiments revealed sucralose as the activating sweetener. Activation of GPR52 was concentration-dependent, with an EC50 of 0.23 mmol/L and an Emax of 3.43 ± 0.24 fold change at 4 mmol/L. GPR52 constitutively activates CRE pathways; however, we show that sucralose-induced activation of GPR52 does not further activate this pathway. Identification of this novel sucralose-GPCR interaction supports the notion that sucralose elicits off-target signaling through the activation of GPR52, calling into question sucralose's assumed lack of bioactivity.
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Affiliation(s)
- Madeline E Power
- Department of Chemistry and Biochemistry, Mount Allison University, Sackville, NB, Canada
| | - Nicholas R Fernandez
- Department of Chemistry and Biochemistry, Mount Allison University, Sackville, NB, Canada
| | - Olaiya Peter Oni
- Department of Chemistry and Biochemistry, Mount Allison University, Sackville, NB, Canada
| | - Aditaya Kalia
- Department of Chemistry and Biochemistry, Mount Allison University, Sackville, NB, Canada
| | - Jillian L Rourke
- Department of Chemistry and Biochemistry, Mount Allison University, Sackville, NB, Canada
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Gin A, Nguyen PD, Melzer JE, Li C, Strzelinski H, Liggett SB, Su J. Label-free, real-time monitoring of membrane binding events at zeptomolar concentrations using frequency-locked optical microresonators. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.20.558657. [PMID: 37786702 PMCID: PMC10541581 DOI: 10.1101/2023.09.20.558657] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/04/2023]
Abstract
Binding events to elements of the cell membrane act as receptors which regulate cellular function and communication and are the targets of many small molecule drug discovery efforts for agonists and antagonists. Conventional techniques to probe these interactions generally require labels and large amounts of receptor to achieve satisfactory sensitivity. Whispering gallery mode microtoroid optical resonators have demonstrated sensitivity to detect single-molecule binding events. Here, we demonstrate the use of frequency-locked optical microtoroids for characterization of membrane interactions in vitro at zeptomolar concentrations using a supported biomimetic membrane. Arrays of microtoroids were produced using photolithography and subsequently modified with a biomimetic membrane, providing high quality (Q) factors (> 10 6 ) in aqueous environments. Fluorescent recovery after photobleaching (FRAP) experiments confirmed the retained fluidity of the microtoroid supported-lipid membrane with a diffusion coefficient of 3.38 ± 0.26 μm 2 ⋅ s - 1 . Utilizing this frequency-locked membrane-on-a-chip model combined with auto-balanced detection and non-linear post-processing techniques, we demonstrate zeptomolar detection levels The binding of Cholera Toxin B- monosialotetrahexosyl ganglioside (GM1) was monitored in real-time, with an apparent equilibrium dissociation constant k d = 1.53 nM . The measured affiny of the agonist dynorphin A 1-13 to the κ -opioid receptor revealed a k d = 3.1 nM using the same approach. Radioligand binding competition with dynorphin A 1-13 revealed a k d in agreement (1.1 nM) with the unlabeled method. The biosensing platform reported herein provides a highly sensitive real-time characterization of membrane embedded protein binding kinetics, that is rapid and label-free, for toxin screening and drug discovery, among other applications.
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Affiliation(s)
- Adley Gin
- Wyant College of Optical Sciences, The University of Arizona, Tucson, AZ 85721
| | - Phuong-Diem Nguyen
- Department of Biomedical Engineering, The University of Arizona, Tucson, AZ 85721
| | - Jeffrey E. Melzer
- Wyant College of Optical Sciences, The University of Arizona, Tucson, AZ 85721
| | - Cheng Li
- Wyant College of Optical Sciences, The University of Arizona, Tucson, AZ 85721
| | - Hannah Strzelinski
- Department of Medicine, University of South Florida Morsani College of Medicine, Tampa, FL 33612
| | - Stephen B. Liggett
- Department of Medicine, University of South Florida Morsani College of Medicine, Tampa, FL 33612
| | - Judith Su
- Wyant College of Optical Sciences, The University of Arizona, Tucson, AZ 85721
- Department of Biomedical Engineering, The University of Arizona, Tucson, AZ 85721
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Matt RA, Westhorpe FG, Romuar RF, Rana P, Gever JR, Ford AP. Fingerprinting heterocellular β-adrenoceptor functional expression in the brain using agonist activity profiles. Front Mol Biosci 2023; 10:1214102. [PMID: 37664183 PMCID: PMC10471193 DOI: 10.3389/fmolb.2023.1214102] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 07/05/2023] [Indexed: 09/05/2023] Open
Abstract
Noradrenergic projections from the brainstem locus coeruleus drive arousal, attentiveness, mood, and memory, but specific adrenoceptor (AR) function across the varied brain cell types has not been extensively characterized, especially with agonists. This study reports a pharmacological analysis of brain AR function, offering insights for innovative therapeutic interventions that might serve to compensate for locus coeruleus decline, known to develop in the earliest phases of neurodegenerative diseases. First, β-AR agonist activities were measured in recombinant cell systems and compared with those of isoprenaline to generate Δlog(Emax/EC50) values, system-independent metrics of agonist activity, that, in turn, provide receptor subtype fingerprints. These fingerprints were then used to assess receptor subtype expression across human brain cell systems and compared with Δlog(Emax/EC50) values arising from β-arrestin activation or measurements of cAMP response desensitization to assess the possibility of ligand bias among β-AR agonists. Agonist activity profiles were confirmed to be system-independent and, in particular, revealed β2-AR functional expression across several human brain cell types. Broad β2-AR function observed is consistent with noradrenergic tone arising from the locus coeruleus exerting heterocellular neuroexcitatory and homeostatic influence. Notably, Δlog(Emax/EC50) measurements suggest that tested β-AR agonists do not show ligand bias as it pertains to homologous receptor desensitization in the system examined. Δlog(Emax/EC50) agonist fingerprinting is a powerful means of assessing receptor subtype expression regardless of receptor expression levels or assay readout, and the method may be applicable to future use for novel ligands and tissues expressing any receptor with available reference agonists.
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Chen G, Obal D. Detecting and measuring of GPCR signaling - comparison of human induced pluripotent stem cells and immortal cell lines. Front Endocrinol (Lausanne) 2023; 14:1179600. [PMID: 37293485 PMCID: PMC10244570 DOI: 10.3389/fendo.2023.1179600] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2023] [Accepted: 04/12/2023] [Indexed: 06/10/2023] Open
Abstract
G protein-coupled receptors (GPCRs) are a large family of transmembrane proteins that play a major role in many physiological processes, and thus GPCR-targeted drug development has been widely promoted. Although research findings generated in immortal cell lines have contributed to the advancement of the GPCR field, the homogenous genetic backgrounds, and the overexpression of GPCRs in these cell lines make it difficult to correlate the results with clinical patients. Human induced pluripotent stem cells (hiPSCs) have the potential to overcome these limitations, because they contain patient specific genetic information and can differentiate into numerous cell types. To detect GPCRs in hiPSCs, highly selective labeling and sensitive imaging techniques are required. This review summarizes existing resonance energy transfer and protein complementation assay technologies, as well as existing and new labeling methods. The difficulties of extending existing detection methods to hiPSCs are discussed, as well as the potential of hiPSCs to expand GPCR research towards personalized medicine.
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Affiliation(s)
- Gaoxian Chen
- Department of Anesthesiology, Perioperative, and Pain Medicine, Stanford University, Stanford, CA, United States
- Stanford Cardiovascular Institute, Stanford University, Stanford, CA, United States
| | - Detlef Obal
- Department of Anesthesiology, Perioperative, and Pain Medicine, Stanford University, Stanford, CA, United States
- Stanford Cardiovascular Institute, Stanford University, Stanford, CA, United States
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Dubovski N, Fierro F, Margulis E, Ben Shoshan-Galeczki Y, Peri L, Niv MY. Taste GPCRs and their ligands. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2022; 193:177-193. [PMID: 36357077 DOI: 10.1016/bs.pmbts.2022.06.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Taste GPCRs are expressed in taste buds on the tongue and play a key role in food choice and consumption. They are also expressed extra-orally, with various physiological roles that are currently under study. Unraveling the roles of these receptors relies on the knowledge of their ligands. Combining sensory, cell-based and computational approaches enabled the discovery of numerous agonists and several antagonists. Here we provide a short overview of taste receptor families, main recent methods for ligands discovery, and current sources of information about known ligands. The future directions that are likely to impact the taste GPCR field include focus on ligand interactions with naturally occurring polymorphisms, as well as harnessing the power of CryoEM and of multiple signaling readout techniques.
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Affiliation(s)
- Nitzan Dubovski
- The Institute of Biochemistry, Food Science and Nutrition, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Fabrizio Fierro
- The Institute of Biochemistry, Food Science and Nutrition, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Eitan Margulis
- The Institute of Biochemistry, Food Science and Nutrition, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Yaron Ben Shoshan-Galeczki
- The Institute of Biochemistry, Food Science and Nutrition, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Lior Peri
- The Institute of Biochemistry, Food Science and Nutrition, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Masha Y Niv
- The Institute of Biochemistry, Food Science and Nutrition, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel.
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Investigating the ligand agonism and antagonism at the D 2long receptor by dynamic mass redistribution. Sci Rep 2022; 12:9637. [PMID: 35688965 PMCID: PMC9187652 DOI: 10.1038/s41598-022-14311-w] [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: 03/05/2022] [Accepted: 06/06/2022] [Indexed: 11/09/2022] Open
Abstract
The signalling of the D2 receptor (D2R), a G protein-coupled receptor (GPCR), is a complex process consisting of various components. For the screening of D2R ligands, methods quantifying distinct second messengers such as cAMP or the interaction of the receptor with β-arrestin, are commonly employed. In contrast, a label-free biosensor technology like dynamic mass redistribution (DMR), where it is mostly unknown how the individual signalling pathways contribute to the DMR signal, provides a holistic readout of the complex cellular response. In this study, we report the successful application of the DMR technology to CHO-K1 cells stably expressing the human dopamine D2long receptor. In real-time kinetic experiments, studies of D2R reference compounds yielded results for agonists and antagonists that were consistent with those obtained by conventional methods and also allowed a discrimination between partial and full agonists. Furthermore, investigations on the signalling pathway in CHO-K1 hD2longR cells identified the Gαi/o protein as the main proximal trigger of the observed DMR response. The present study has shown that the DMR technology is a valuable method for the characterisation of putative new ligands and, due to its label-free nature, suggests its use for deorphanisation studies of GPCRs.
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