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Massoud TF, Paulmurugan R. Molecular Imaging of Protein–Protein Interactions and Protein Folding. Mol Imaging 2021. [DOI: 10.1016/b978-0-12-816386-3.00071-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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2
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Willard FS, Douros JD, Gabe MB, Showalter AD, Wainscott DB, Suter TM, Capozzi ME, van der Velden WJ, Stutsman C, Cardona GR, Urva S, Emmerson PJ, Holst JJ, D’Alessio DA, Coghlan MP, Rosenkilde MM, Campbell JE, Sloop KW. Tirzepatide is an imbalanced and biased dual GIP and GLP-1 receptor agonist. JCI Insight 2020; 5:140532. [PMID: 32730231 PMCID: PMC7526454 DOI: 10.1172/jci.insight.140532] [Citation(s) in RCA: 183] [Impact Index Per Article: 45.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 07/22/2020] [Indexed: 12/25/2022] Open
Abstract
Tirzepatide (LY3298176) is a dual GIP and GLP-1 receptor agonist under development for the treatment of type 2 diabetes mellitus (T2DM), obesity, and nonalcoholic steatohepatitis. Early phase trials in T2DM indicate that tirzepatide improves clinical outcomes beyond those achieved by a selective GLP-1 receptor agonist. Therefore, we hypothesized that the integrated potency and signaling properties of tirzepatide provide a unique pharmacological profile tailored for improving broad metabolic control. Here, we establish methodology for calculating occupancy of each receptor for clinically efficacious doses of the drug. This analysis reveals a greater degree of engagement of tirzepatide for the GIP receptor than the GLP-1 receptor, corroborating an imbalanced mechanism of action. Pharmacologically, signaling studies demonstrate that tirzepatide mimics the actions of native GIP at the GIP receptor but shows bias at the GLP-1 receptor to favor cAMP generation over β-arrestin recruitment, coincident with a weaker ability to drive GLP-1 receptor internalization compared with GLP-1. Experiments in primary islets reveal β-arrestin1 limits the insulin response to GLP-1, but not GIP or tirzepatide, suggesting that the biased agonism of tirzepatide enhances insulin secretion. Imbalance toward GIP receptor, combined with distinct signaling properties at the GLP-1 receptor, together may account for the promising efficacy of this investigational agent.
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Affiliation(s)
- Francis S. Willard
- Quantitative Biology, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | - Jonathan D. Douros
- Duke Molecular Physiology Institute, Duke University, Durham, North Carolina, USA
| | - Maria B.N. Gabe
- Department of Biomedical Sciences and NNF Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
| | | | - David B. Wainscott
- Quantitative Biology, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | | | - Megan E. Capozzi
- Duke Molecular Physiology Institute, Duke University, Durham, North Carolina, USA
| | - Wijnand J.C. van der Velden
- Department of Biomedical Sciences and NNF Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
| | | | - Guemalli R. Cardona
- Quantitative Biology, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | - Shweta Urva
- PK/PD & Pharmacometrics, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | | | - Jens J. Holst
- Department of Biomedical Sciences and NNF Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
| | - David A. D’Alessio
- Duke Molecular Physiology Institute, Duke University, Durham, North Carolina, USA
| | | | - Mette M. Rosenkilde
- Department of Biomedical Sciences and NNF Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
| | - Jonathan E. Campbell
- Duke Molecular Physiology Institute, Duke University, Durham, North Carolina, USA
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3
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Optical approaches for single-cell and subcellular analysis of GPCR-G protein signaling. Anal Bioanal Chem 2019; 411:4481-4508. [PMID: 30927013 DOI: 10.1007/s00216-019-01774-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2018] [Revised: 03/05/2019] [Accepted: 03/08/2019] [Indexed: 01/05/2023]
Abstract
G protein-coupled receptors (GPCRs), G proteins, and their signaling associates are major signal transducers that control the majority of cellular signaling and regulate key biological functions including immune, neurological, cardiovascular, and metabolic processes. These pathways are targeted by over one-third of drugs on the market; however, the current understanding of their function is limited and primarily derived from cell-destructive approaches providing an ensemble of static, multi-cell information about the status and composition of molecules. Spatiotemporal behavior of molecules involved is crucial to understanding in vivo cell behaviors both in health and disease, and the advent of genetically encoded fluorescence proteins and small fluorophore-based biosensors has facilitated the mapping of dynamic signaling in cells with subcellular acuity. Since we and others have developed optogenetic methods to regulate GPCR-G protein signaling in single cells and subcellular regions using dedicated wavelengths, the desire to develop and adopt optogenetically amenable assays to measure signaling has motivated us to take a broader look at the available optical tools and approaches compatible with measuring single-cell and subcellular GPCR-G protein signaling. Here we review such key optical approaches enabling the examination of GPCR, G protein, secondary messenger, and downstream molecules such as kinase and lipid signaling in living cells. The methods reviewed employ both fluorescence and bioluminescence detection. We not only further elaborate the underlying principles of these sensors but also discuss the experimental criteria and limitations to be considered during their use in single-cell and subcellular signal mapping.
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4
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Farb TB, Adeva M, Beauchamp TJ, Cabrera O, Coates DA, Meredith TD, Droz BA, Efanov A, Ficorilli JV, Gackenheimer SL, Martinez-Grau MA, Molero V, Ruano G, Statnick MA, Suter TM, Syed SK, Toledo MA, Willard FS, Zhou X, Bokvist KB, Barrett DG. Regulation of Endogenous (Male) Rodent GLP-1 Secretion and Human Islet Insulin Secretion by Antagonism of Somatostatin Receptor 5. Endocrinology 2017; 158:3859-3873. [PMID: 28938487 DOI: 10.1210/en.2017-00639] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 09/06/2017] [Indexed: 12/25/2022]
Abstract
Incretin and insulin responses to nutrient loads are suppressed in persons with diabetes, resulting in decreased glycemic control. Agents including sulfonylureas and dipeptidyl peptidase-4 inhibitors (DPP4i) partially reverse these effects and provide therapeutic benefit; however, their modes of action limit efficacy. Because somatostatin (SST) has been shown to suppress insulin and glucagonlike peptide-1 (GLP-1) secretion through the Gi-coupled SST receptor 5 (SSTR5) isoform in vitro, antagonism of SSTR5 may improve glycemic control via intervention in both pathways. Here, we show that a potent and selective SSTR5 antagonist reverses the blunting effects of SST on insulin secretion from isolated human islets, and demonstrate that SSTR5 antagonism affords increased levels of systemic GLP-1 in vivo. Knocking out Sstr5 in mice provided a similar increase in systemic GLP-1 levels, which were not increased further by treatment with the antagonist. Treatment of mice with the SSTR5 antagonist in combination with a DPP4i resulted in increases in systemic GLP-1 levels that were more than additive and resulted in greater glycemic control compared with either agent alone. In isolated human islets, the SSTR5 antagonist completely reversed the inhibitory effect of exogenous SST-14 on insulin secretion. Taken together, these data suggest that SSTR5 antagonism should increase circulating GLP-1 levels and stimulate insulin secretion (directly and via GLP-1) in humans, improving glycemic control in patients with diabetes.
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Affiliation(s)
- Thomas B Farb
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285
| | - Marta Adeva
- Centro de Investigacion Lilly, Eli Lilly and Company, 28108-Alcobendas, Madrid, Spain
| | - Thomas J Beauchamp
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285
| | - Over Cabrera
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285
| | - David A Coates
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285
| | | | - Brian A Droz
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285
| | - Alexander Efanov
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285
| | - James V Ficorilli
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285
| | | | - Maria A Martinez-Grau
- Centro de Investigacion Lilly, Eli Lilly and Company, 28108-Alcobendas, Madrid, Spain
| | - Victoriano Molero
- Centro de Investigacion Lilly, Eli Lilly and Company, 28108-Alcobendas, Madrid, Spain
| | - Gema Ruano
- Centro de Investigacion Lilly, Eli Lilly and Company, 28108-Alcobendas, Madrid, Spain
| | - Michael A Statnick
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285
| | - Todd M Suter
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285
| | - Samreen K Syed
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285
| | - Miguel A Toledo
- Centro de Investigacion Lilly, Eli Lilly and Company, 28108-Alcobendas, Madrid, Spain
| | - Francis S Willard
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285
| | - Xin Zhou
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285
| | - Krister B Bokvist
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285
| | - David G Barrett
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285
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5
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Kono M, Conlon EG, Lux SY, Yanagida K, Hla T, Proia RL. Bioluminescence imaging of G protein-coupled receptor activation in living mice. Nat Commun 2017; 8:1163. [PMID: 29079828 PMCID: PMC5660082 DOI: 10.1038/s41467-017-01340-7] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Accepted: 09/06/2017] [Indexed: 01/04/2023] Open
Abstract
G protein-coupled receptors (GPCRs), a superfamily of cell-surface receptors involved in virtually all physiological processes, are the major target class for approved drugs. Imaging GPCR activation in real time in living animals would provide a powerful way to study their role in biology and disease. Here, we describe a mouse model that enables the bioluminescent detection of GPCR activation in real time by utilizing the clinically important GPCR, sphingosine-1-phosphate receptor 1 (S1P1). A synthetic S1P1 signaling pathway, designed to report the interaction between S1P1 and β-arrestin2 via the firefly split luciferase fragment complementation system, is genetically encoded in these mice. Upon receptor activation and subsequent β-arrestin2 recruitment, an active luciferase enzyme complex is produced, which can be detected by in vivo bioluminescence imaging. This imaging strategy reveals the dynamics and spatial specificity of S1P1 activation in normal and pathophysiologic contexts in vivo and can be applied to other GPCRs. G protein-coupled receptors are involved in numerous physiological functions, thus, they represent potential pharmaceutical targets. Here Kono et al. describe a new mouse model to image GPCR activation in real-time by exploiting firefly split luciferase fragment complementation that can be detected by bioluminescence imaging.
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Affiliation(s)
- Mari Kono
- Genetics of Development and Disease Branch, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD, 20892, USA
| | - Elizabeth G Conlon
- Genetics of Development and Disease Branch, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD, 20892, USA
| | - Samantha Y Lux
- Genetics of Development and Disease Branch, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD, 20892, USA
| | - Keisuke Yanagida
- Vascular Biology Program, Boston Children's Hospital, Department of Surgery, Harvard Medical School, Boston, MA, 02115, USA
| | - Timothy Hla
- Vascular Biology Program, Boston Children's Hospital, Department of Surgery, Harvard Medical School, Boston, MA, 02115, USA
| | - Richard L Proia
- Genetics of Development and Disease Branch, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD, 20892, USA.
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6
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Yashima S, Shimazaki A, Mitoma J, Nakagawa T, Abe M, Yamada H, Higashi H. Close association of B2 bradykinin receptors with P2Y2 ATP receptors. J Biochem 2015; 158:155-63. [PMID: 25713410 DOI: 10.1093/jb/mvv022] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Accepted: 02/10/2015] [Indexed: 11/12/2022] Open
Abstract
Two G-protein-coupled receptors (GPCRs) that couple with Gαq/11, B2 bradykinin (BK) receptor (B2R) and ATP/UTP receptor P2Y2 (P2Y2R), are ubiquitously expressed and responsible for vascular tone, inflammation, and pain. We analysed the cellular signalling of P2Y2Rs in cells that express B2Rs. B2R desensitization induced by BK or B2R internalization-inducing glycans cross-desensitized the P2Y2R response to ATP/UTP. Fluorescence resonance energy transfer from P2Y2R-AcGFP to B2R-DsRed was detected in the cells and on the cell surfaces, showing the close association of these GPCRs. BK- and ATP-induced cross-internalization of P2Y2R and B2R, respectively, was shown in a β-galactosidase complementation assay using P2Y2R or B2R fused to the H31R substituted α donor peptide of a β-galactosidase reporter enzyme (P2Y2R-α or B2R-α) with coexpression of the FYVE domain of endofin, an early endosome protein, fused to the M15 acceptor deletion mutant of β-galactosidase (the ω peptide, FYVE-ω). Arrestin recruitment to the GPCRs by cross-activation was also shown with the similar way. Coimmunoprecipitation showed that B2R and P2Y2R were closely associated in the cotransfected cells. These results indicate that B2R couples with P2Y2R and that these GPCRs act together to fine-tune cellular responsiveness. The collaboration between these receptors may permit rapid onset and turning off of biological events.
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Affiliation(s)
- Sayo Yashima
- Division of Glyco-Signal Research, Institute of Molecular Biomembrane and Glycobiology, Tohoku Pharmaceutical University, Sendai, Miyagi 981-8558, Japan
| | - Ayaka Shimazaki
- Division of Glyco-Signal Research, Institute of Molecular Biomembrane and Glycobiology, Tohoku Pharmaceutical University, Sendai, Miyagi 981-8558, Japan
| | - Junya Mitoma
- Division of Glyco-Signal Research, Institute of Molecular Biomembrane and Glycobiology, Tohoku Pharmaceutical University, Sendai, Miyagi 981-8558, Japan
| | - Tetsuto Nakagawa
- Division of Glyco-Signal Research, Institute of Molecular Biomembrane and Glycobiology, Tohoku Pharmaceutical University, Sendai, Miyagi 981-8558, Japan
| | - Maya Abe
- Division of Glyco-Signal Research, Institute of Molecular Biomembrane and Glycobiology, Tohoku Pharmaceutical University, Sendai, Miyagi 981-8558, Japan
| | - Hiroyuki Yamada
- Division of Glyco-Signal Research, Institute of Molecular Biomembrane and Glycobiology, Tohoku Pharmaceutical University, Sendai, Miyagi 981-8558, Japan
| | - Hideyoshi Higashi
- Division of Glyco-Signal Research, Institute of Molecular Biomembrane and Glycobiology, Tohoku Pharmaceutical University, Sendai, Miyagi 981-8558, Japan
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7
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Hattori M, Ozawa T. Bioluminescent tools for the analysis of G-protein-coupled receptor and arrestin interactions. RSC Adv 2015. [DOI: 10.1039/c4ra14979c] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
New protein-based bioluminescent probes for monitoring GPCR interaction with β-arrestin are presented.
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Affiliation(s)
- Mitsuru Hattori
- Department of Chemistry
- School of Science
- The University of Tokyo
- Bunkyo-ku
- Japan
| | - Takeaki Ozawa
- Department of Chemistry
- School of Science
- The University of Tokyo
- Bunkyo-ku
- Japan
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8
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Graham KL, Zhang JV, Lewén S, Burke TM, Dang T, Zoudilova M, Sobel RA, Butcher EC, Zabel BA. A novel CMKLR1 small molecule antagonist suppresses CNS autoimmune inflammatory disease. PLoS One 2014; 9:e112925. [PMID: 25437209 PMCID: PMC4249827 DOI: 10.1371/journal.pone.0112925] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Accepted: 10/22/2014] [Indexed: 12/27/2022] Open
Abstract
Therapies that target leukocyte trafficking pathways can reduce disease activity and improve clinical outcomes in multiple sclerosis (MS). Experimental autoimmune encephalomyelitis (EAE) is a widely studied animal model that shares many clinical and histological features with MS. Chemokine-like receptor-1 (CMKLR1) is a chemoattractant receptor that is expressed by key effector cells in EAE and MS, including macrophages, subsets of dendritic cells, natural killer cells and microglia. We previously showed that CMKLR1-deficient (CMKLR1 KO) mice develop less severe clinical and histological EAE than wild-type mice. In this study, we sought to identify CMKLR1 inhibitors that would pharmaceutically recapitulate the CMKLR1 KO phenotype in EAE. We identified 2-(α-naphthoyl) ethyltrimethylammonium iodide (α-NETA) as a CMKLR1 small molecule antagonist that inhibits chemerin-stimulated β-arrestin2 association with CMKLR1, as well as chemerin-triggered CMKLR1+ cell migration. α-NETA significantly delayed the onset of EAE induced in C57BL/6 mice by both active immunization with myelin oligodendrocyte glycoprotein peptide 35-55 and by adoptive transfer of encephalitogenic T cells. In addition, α-NETA treatment significantly reduced mononuclear cell infiltrates within the CNS. This study provides additional proof-of-concept data that targeting CMKLR1:chemerin interactions may be beneficial in preventing or treating MS.
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MESH Headings
- Animals
- Arrestins/metabolism
- Brain/drug effects
- Brain/metabolism
- Cell Movement/drug effects
- Chemokines/metabolism
- Drug Evaluation, Preclinical
- Drug Stability
- Encephalomyelitis, Autoimmune, Experimental/drug therapy
- Encephalomyelitis, Autoimmune, Experimental/immunology
- Encephalomyelitis, Autoimmune, Experimental/metabolism
- Encephalomyelitis, Autoimmune, Experimental/pathology
- Female
- Humans
- Intercellular Signaling Peptides and Proteins/metabolism
- Leukocytes/drug effects
- Mice
- Mice, Inbred C57BL
- Naphthalenes/adverse effects
- Naphthalenes/chemistry
- Naphthalenes/pharmacology
- Naphthalenes/therapeutic use
- Quaternary Ammonium Compounds/adverse effects
- Quaternary Ammonium Compounds/chemistry
- Quaternary Ammonium Compounds/pharmacology
- Quaternary Ammonium Compounds/therapeutic use
- Receptors, Chemokine
- Receptors, G-Protein-Coupled/antagonists & inhibitors
- Safety
- Spinal Cord/drug effects
- Spinal Cord/metabolism
- Structure-Activity Relationship
- beta-Arrestins
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Affiliation(s)
- Kareem L Graham
- Palo Alto Veterans Institute for Research and Veterans Affairs Palo Alto Health Care System, Palo Alto, California, United States of America
| | - Jian V Zhang
- Palo Alto Veterans Institute for Research and Veterans Affairs Palo Alto Health Care System, Palo Alto, California, United States of America
| | - Susanna Lewén
- Palo Alto Veterans Institute for Research and Veterans Affairs Palo Alto Health Care System, Palo Alto, California, United States of America
| | - Thomas M Burke
- Palo Alto Veterans Institute for Research and Veterans Affairs Palo Alto Health Care System, Palo Alto, California, United States of America
| | - Ton Dang
- ChemoCentryx, Inc., Mountain View, California, United States of America
| | - Maria Zoudilova
- Department of Pathology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Raymond A Sobel
- Department of Pathology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Eugene C Butcher
- Department of Pathology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Brian A Zabel
- Palo Alto Veterans Institute for Research and Veterans Affairs Palo Alto Health Care System, Palo Alto, California, United States of America
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9
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Dressler H, Economides K, Favara S, Wu NN, Pang Z, Polites HG. The CRE luc bioluminescence transgenic mouse model for detecting ligand activation of GPCRs. ACTA ACUST UNITED AC 2013; 19:232-41. [PMID: 23896687 DOI: 10.1177/1087057113496465] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Numerous assays have been developed to investigate the interactions between G-protein-coupled receptors (GPCRs) and their ligands since GPCRs are key therapeutic targets. Reporter-based assays using the cAMP response element (CRE) coupled with bioluminescence from a luciferase reporter have been used extensively in vitro with high-throughput screens (HTS) of large chemical compound libraries. We have generated a transgenic mouse model (CRE luc) with a luciferase reporter under the control of a synthetic promoter that contains several CREs, which supports real-time bioimaging of GPCR ligand activity in whole animals, tissues, or primary cells. In the CRE luc model, GPCR signaling through the cAMP pathway can be detected from the target GPCR that is in a native cellular environment with a full complement of associated receptors and membrane constituents. Multiple independent lines have been produced by random integration of the transgene, resulting in tissue expression profiles covering the major organs. The goal of the CRE luc model is to accelerate the transition from HTS to profiling of GPCR small-molecule leads in preclinical animal disease models, as well as define the mechanism of action of GPCR drugs in three experimental formats: primary cells, tissue homogenates, and whole animals.
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10
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Diversity in genetic in vivo methods for protein-protein interaction studies: from the yeast two-hybrid system to the mammalian split-luciferase system. Microbiol Mol Biol Rev 2012; 76:331-82. [PMID: 22688816 DOI: 10.1128/mmbr.05021-11] [Citation(s) in RCA: 134] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The yeast two-hybrid system pioneered the field of in vivo protein-protein interaction methods and undisputedly gave rise to a palette of ingenious techniques that are constantly pushing further the limits of the original method. Sensitivity and selectivity have improved because of various technical tricks and experimental designs. Here we present an exhaustive overview of the genetic approaches available to study in vivo binary protein interactions, based on two-hybrid and protein fragment complementation assays. These methods have been engineered and employed successfully in microorganisms such as Saccharomyces cerevisiae and Escherichia coli, but also in higher eukaryotes. From single binary pairwise interactions to whole-genome interactome mapping, the self-reassembly concept has been employed widely. Innovative studies report the use of proteins such as ubiquitin, dihydrofolate reductase, and adenylate cyclase as reconstituted reporters. Protein fragment complementation assays have extended the possibilities in protein-protein interaction studies, with technologies that enable spatial and temporal analyses of protein complexes. In addition, one-hybrid and three-hybrid systems have broadened the types of interactions that can be studied and the findings that can be obtained. Applications of these technologies are discussed, together with the advantages and limitations of the available assays.
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11
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Takakura H, Hattori M, Takeuchi M, Ozawa T. Visualization and quantitative analysis of G protein-coupled receptor-β-arrestin interaction in single cells and specific organs of living mice using split luciferase complementation. ACS Chem Biol 2012; 7:901-10. [PMID: 22364396 DOI: 10.1021/cb200360z] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Methods used to assess the efficacy of potentially therapeutic reagents for G protein-coupled receptors (GPCRs) have been developed. Previously, we demonstrated sensitive detection of the interaction of GPCRs and β-arrestin2 (ARRB2) using 96-well microtiter plates and a bioluminescence microscope based on split click beetle luciferase complementation. Herein, using firefly luciferase emitting longer wavelength light, we demonstrate quantitative analysis of the interaction of β2-adrenergic receptor (ADRB2), a kind of GPCR, and ARRB2 in a 96-well plate assay with single-cell imaging. Additionally, we showed bioluminescence in vivo imaging of the ADRB2-ARRB2 interaction in two systems: cell implantation and hydrodynamic tail vein (HTV) methods. Specifically, in the HTV method, the luminescence signal from the liver upon stimulation of an agonist for ADRB2 was obtained in the intact systems of mice. The results demonstrate that this method enables noninvasive screening of the efficacy of chemicals at the specific organ in in vivo testing. This in vivo system can contribute to effective evaluation in pharmacokinetics and pharmacodynamics and expedite the development of new drugs for GPCRs.
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Affiliation(s)
- Hideo Takakura
- Department of Chemistry, School of
Science, The University of Tokyo, 7-3-1
Hongo, Bunkyo-ku, Tokyo
113-0033, Japan
| | - Mitsuru Hattori
- Department of Chemistry, School of
Science, The University of Tokyo, 7-3-1
Hongo, Bunkyo-ku, Tokyo
113-0033, Japan
| | - Masaki Takeuchi
- Department of Chemistry, School of
Science, The University of Tokyo, 7-3-1
Hongo, Bunkyo-ku, Tokyo
113-0033, Japan
| | - Takeaki Ozawa
- Department of Chemistry, School of
Science, The University of Tokyo, 7-3-1
Hongo, Bunkyo-ku, Tokyo
113-0033, Japan
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12
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Bassoni DL, Raab WJ, Achacoso PL, Loh CY, Wehrman TS. Measurements of β-arrestin recruitment to activated seven transmembrane receptors using enzyme complementation. Methods Mol Biol 2012; 897:181-203. [PMID: 22674166 DOI: 10.1007/978-1-61779-909-9_9] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The recruitment of arrestins to activated 7TMRs results in the activation of alternative signaling pathways, quenching of G-protein activation, and coupling to clathrin-mediated endocytosis. The nearly ubiquitous involvement of arrestin in 7TMR signaling has spurred the development of several methods for monitoring this interaction in mammalian cells. Nonetheless, few maintain the reproducibility and precision necessary for drug discovery applications. Enzyme fragment complementation technology (EFC) is an emerging protein-protein interaction technology based on the forced complementation of a split enzyme that has proven to be highly effective in monitoring the formation of GPCR-arrestin complexes. In these systems, the target proteins are fused to two fragments of an enzyme that show little or no spontaneous complementation. Interaction of the two proteins forces the complementation of the enzyme, resulting in an enzymatic measure of the protein interaction. This chapter discusses the utility and methods involved in using the PathHunter β-galactosidase complementation system to monitor arrestin recruitment and the advantages of exploiting this pathway in the characterization of 7TMR function.
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13
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Luker GD, Luker KE. Luciferase protein complementation assays for bioluminescence imaging of cells and mice. Methods Mol Biol 2011; 680:29-43. [PMID: 21153371 DOI: 10.1007/978-1-60761-901-7_2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Protein fragment complementation assays (PCAs) with luciferase reporters currently are the preferred method for detecting and quantifying protein-protein interactions in living animals. At the most basic level, PCAs involve fusion of two proteins of interest to enzymatically inactive fragments of luciferase. Upon association of the proteins of interest, the luciferase fragments are capable of reconstituting enzymatic activity to generate luminescence in vivo. In addition to bi-molecular luciferase PCAs, unimolecular biosensors for hormones, kinases, and proteases also have been developed using target peptides inserted between inactive luciferase fragments. Luciferase PCAs offer unprecedented opportunities to quantify dynamics of protein-protein interactions in intact cells and living animals, but successful use of luciferase PCAs in cells and mice involves careful consideration of many technical factors. This chapter discusses the design of luciferase PCAs appropriate for animal imaging, including construction of reporters, incorporation of reporters into cells and mice, imaging techniques, and data analysis.
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Affiliation(s)
- Gary D Luker
- Department of Radiology, University of Michigan, Ann Arbor, MI 48109-2200, USA.
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14
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Kafi A, Hattori M, Misawa N, Ozawa T. Dual-Color Bioluminescence Analysis for Quantitatively Monitoring G-Protein-Coupled Receptor and β-Arrestin Interactions. Pharmaceuticals (Basel) 2011. [PMCID: PMC4053796 DOI: 10.3390/ph4030457] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
G protein-coupled receptors (GPCRs) are crucial elements in mammalian signal transduction, and are considered to represent potent drug targets. We have previously developed a GPCR assay system in cultured cells based on complementation of split fragments of click beetle (Pyrearinus termitilluminans) luciferase. The interaction of GPCRs with its target, β-arrestin, resulted in strong emission of bioluminescence upon stimulation with its specific ligand. In this study, we improved precision of the GPCR assay system by using railroad worm (Phrixothrix hirtus) luciferase as an internal control. We generated stable cell lines harboring the railroad worm luciferase and quantitatively evaluate the extent of GPCR-β-arrestin interactions. We showed concentration-dependent bioluminescence responses for four GPCRs: β2-adrenoceptor, endothelin receptor type A, α2-adrenoceptor and human μ-opioid receptor. We also demonstrated that the variation of responses was reduced significantly by normalizing the data with bioluminescence from railroad worm luciferase. This assay system represents a simple and reliable approach for screening drug candidates in a high throughput manner.
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Affiliation(s)
- A.K.M. Kafi
- Department of Chemistry, School of Science, The University of Tokyo, Bunkyo-ku, Hongo, Tokyo 113, Japan
| | - Mitsuru Hattori
- Department of Chemistry, School of Science, The University of Tokyo, Bunkyo-ku, Hongo, Tokyo 113, Japan
| | - Naomi Misawa
- Department of Chemistry, School of Science, The University of Tokyo, Bunkyo-ku, Hongo, Tokyo 113, Japan
| | - Takeaki Ozawa
- Department of Chemistry, School of Science, The University of Tokyo, Bunkyo-ku, Hongo, Tokyo 113, Japan
- PRESTO, Japan Science and Technology Agency, Tokyo, Japan
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +81-3-5841-4351; Fax: +81-3-5802-2989
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15
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Villalobos V, Naik S, Bruinsma M, Dothager RS, Pan MH, Samrakandi M, Moss B, Elhammali A, Piwnica-Worms D. Dual-color click beetle luciferase heteroprotein fragment complementation assays. ACTA ACUST UNITED AC 2011; 17:1018-29. [PMID: 20851351 DOI: 10.1016/j.chembiol.2010.06.018] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2010] [Revised: 06/26/2010] [Accepted: 06/30/2010] [Indexed: 10/19/2022]
Abstract
Understanding the functional complexity of protein interactions requires mapping biomolecular complexes within the cellular environment over biologically relevant time scales. Herein, we describe a set of reversible multicolored heteroprotein complementation fragments based on various firefly and click beetle luciferases that utilize the same substrate, D-luciferin. Luciferase heteroprotein fragment complementation systems enabled dual-color quantification of two discrete pairs of interacting proteins simultaneously or two distinct proteins interacting with a third shared protein in live cells. Using real-time analysis of click beetle green and click beetle red luciferase heteroprotein fragment complementation applied to β-TrCP, an E3-ligase common to the regulation of both β-catenin and IκBα, GSK3β was identified as a candidate kinase regulating IκBα processing. These dual-color protein interaction switches may enable directed dynamic analysis of a variety of protein interactions in living cells.
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Affiliation(s)
- Victor Villalobos
- Molecular Imaging Center, Mallinckrodt Institute of Radiology, Department of Developmental Biology, Washington University, St. Louis, MO 63110, USA
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16
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Yan D, Stocco R, Sawyer N, Nesheim ME, Abramovitz M, Funk CD. Differential signaling of cysteinyl leukotrienes and a novel cysteinyl leukotriene receptor 2 (CysLT₂) agonist, N-methyl-leukotriene C₄, in calcium reporter and β arrestin assays. Mol Pharmacol 2010; 79:270-8. [PMID: 21078884 DOI: 10.1124/mol.110.069054] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The cysteinyl leukotrienes (cysLTs) LTC₄, LTD₄, and LTE₄ are lipid mediators with physiological and pathophysiological functions. They exert their effects through G protein-coupled receptors (GPCRs), most notably via CysLT₁ and CysLT₂ receptor. The roles of the CysLT₂ receptor are beginning to emerge. Both LTC₄ and LTD₄ are potent agonists for the CysLT₂ receptor; however, LTC₄ is rapidly converted to LTD₄, which is also the main endogenous ligand for the CysLT₁ receptor. A selective and potent agonist at the CysLT₂ receptor would facilitate studies to discern between receptor subtypes. We show here that N-methyl LTC₄ (NMLTC₄), a metabolically stable LTC₄ mimetic, is a potent and selective CysLT₂ receptor agonist. Two expression systems were used to evaluate the functional activity of NMLTC₄ at human and/or mouse CysLT₁ and CysLT₂ receptors. Through the aequorin cell-based assay for calcium-coupled GPCRs, NMLTC₄ was almost equipotent to LTC₄ at CysLT₂ receptors but was the least efficacious at CysLT₂ receptors. In a β-galactosidase-β-arrestin complementation assay, the human (h) CysLT₂ receptor can couple with β-arrestin-2, and NMLTC₄ is slightly more potent for eliciting β-arrestin-2 binding compared with cysLTs. Furthermore, LTE₄ is nearly inactive in this assay compared with its weak partial agonist activity in the aequorin system. In a vascular leakage assay, NMLTC₄ is potent and active in mice overexpressing hCysLT₂ receptor in endothelium, whereas the response is abrogated in CysLT₂ receptor knockout mice. Therefore, NMLTC₄ is a potent subtype selective agonist for the CysLT₂ receptor in vitro and in vivo, and it will be useful to elucidate its biological roles.
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Affiliation(s)
- Dong Yan
- Department of Biochemistry, Queen's University, 18 Stuart Street, 433 Botterell Hall, Kingston, ON K7L 3N6 Canada
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17
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Bohn LM, Schmid CL. Serotonin receptor signaling and regulation via β-arrestins. Crit Rev Biochem Mol Biol 2010; 45:555-66. [PMID: 20925600 DOI: 10.3109/10409238.2010.516741] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Serotonin receptors are the product of 15 distinct genes, 14 of which are G protein-coupled receptors. These receptors are expressed in a wide range of cell types, including distinct neuronal populations, and promote diverse functional responses in multiple organ systems. These receptors are important for mediating the in vivo effects of their cognate neurotransmitter, serotonin, as well as the endogenous tryptamines. In addition, the actions of many drugs are mediated, either directly or indirectly, through serotonin receptors, including antidepressants, antipsychotics, anxiolytics, sleep aids, migraine therapies, gastrointestinal therapeutics and hallucinogenic drugs. It is becoming increasingly evident that serotonin receptors can engage in differential signaling that is determined by the chemical nature of the ligand and that ligands that demonstrate a predilection for inducing a particular signaling cascade are considered to have "functional selectivity". The elucidation of the cellular signaling pathways that mediate the physiological responses to serotonin and other agonists is an active area of investigation and will be an onward-looking focal point for determining how to effectively and selectively promote beneficial serotonergic mimicry while avoiding unwanted clinical side effects. This review highlights the modulation of serotonin 2A, 2C, and four receptors by β-arrestins, which may represent a fulcrum for biasing receptor responsiveness in vivo.
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Affiliation(s)
- Laura M Bohn
- The Scripps Research Institute, Molecular Therapeutics & Neuroscience, Jupiter, FL, USA.
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18
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Misawa N, Kafi AKM, Hattori M, Miura K, Masuda K, Ozawa T. Rapid and High-Sensitivity Cell-Based Assays of Protein−Protein Interactions Using Split Click Beetle Luciferase Complementation: An Approach to the Study of G-Protein-Coupled Receptors. Anal Chem 2010; 82:2552-60. [DOI: 10.1021/ac100104q] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Naomi Misawa
- Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Bunkyo-ku, Hongo, Tokyo 113-0033, Japan, ProbeX Inc., 4-1-4 Bunkyo-ku, Hongo, Tokyo 113-0033, Japan, PRESTO, Japan Science and Technology Agency, 5-3 Chiyoda-ku Yonbanchou, Tokyo 102-8666, Japan, and Tsuruga Institute of Biotechnology, Toyobo Co., Ltd., 10-24, Toyo-cho, Tsuruga, Fukui, 914-0047, Japan
| | - A. K. M. Kafi
- Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Bunkyo-ku, Hongo, Tokyo 113-0033, Japan, ProbeX Inc., 4-1-4 Bunkyo-ku, Hongo, Tokyo 113-0033, Japan, PRESTO, Japan Science and Technology Agency, 5-3 Chiyoda-ku Yonbanchou, Tokyo 102-8666, Japan, and Tsuruga Institute of Biotechnology, Toyobo Co., Ltd., 10-24, Toyo-cho, Tsuruga, Fukui, 914-0047, Japan
| | - Mitsuru Hattori
- Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Bunkyo-ku, Hongo, Tokyo 113-0033, Japan, ProbeX Inc., 4-1-4 Bunkyo-ku, Hongo, Tokyo 113-0033, Japan, PRESTO, Japan Science and Technology Agency, 5-3 Chiyoda-ku Yonbanchou, Tokyo 102-8666, Japan, and Tsuruga Institute of Biotechnology, Toyobo Co., Ltd., 10-24, Toyo-cho, Tsuruga, Fukui, 914-0047, Japan
| | - Kenji Miura
- Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Bunkyo-ku, Hongo, Tokyo 113-0033, Japan, ProbeX Inc., 4-1-4 Bunkyo-ku, Hongo, Tokyo 113-0033, Japan, PRESTO, Japan Science and Technology Agency, 5-3 Chiyoda-ku Yonbanchou, Tokyo 102-8666, Japan, and Tsuruga Institute of Biotechnology, Toyobo Co., Ltd., 10-24, Toyo-cho, Tsuruga, Fukui, 914-0047, Japan
| | - Kenji Masuda
- Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Bunkyo-ku, Hongo, Tokyo 113-0033, Japan, ProbeX Inc., 4-1-4 Bunkyo-ku, Hongo, Tokyo 113-0033, Japan, PRESTO, Japan Science and Technology Agency, 5-3 Chiyoda-ku Yonbanchou, Tokyo 102-8666, Japan, and Tsuruga Institute of Biotechnology, Toyobo Co., Ltd., 10-24, Toyo-cho, Tsuruga, Fukui, 914-0047, Japan
| | - Takeaki Ozawa
- Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Bunkyo-ku, Hongo, Tokyo 113-0033, Japan, ProbeX Inc., 4-1-4 Bunkyo-ku, Hongo, Tokyo 113-0033, Japan, PRESTO, Japan Science and Technology Agency, 5-3 Chiyoda-ku Yonbanchou, Tokyo 102-8666, Japan, and Tsuruga Institute of Biotechnology, Toyobo Co., Ltd., 10-24, Toyo-cho, Tsuruga, Fukui, 914-0047, Japan
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Lievens S, Lemmens I, Tavernier J. Mammalian two-hybrids come of age. Trends Biochem Sci 2009; 34:579-88. [PMID: 19786350 DOI: 10.1016/j.tibs.2009.06.009] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2009] [Revised: 06/12/2009] [Accepted: 06/12/2009] [Indexed: 12/22/2022]
Abstract
A diverse series of mammalian two-hybrid technologies for the detection of protein-protein interactions have emerged in the past few years, complementing the established yeast two-hybrid approach. Given the mammalian background in which they operate, these assays open new avenues to study the dynamics of mammalian protein interaction networks, i.e. the temporal, spatial and functional modulation of protein-protein associations. In addition, novel assay formats are available that enable high-throughput mammalian two-hybrid applications, facilitating their use in large-scale interactome mapping projects. Finally, as they can be applied in drug discovery and development programs, these techniques also offer exciting new opportunities for biomedical research.
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Affiliation(s)
- Sam Lievens
- Department of Medical Protein Research, VIB, A. Baertsoenkaai 3, 9000 Ghent, Belgium
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20
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von Degenfeld G, Wehrman TS, Blau HM. Imaging beta-galactosidase activity in vivo using sequential reporter-enzyme luminescence. Methods Mol Biol 2009; 574:249-59. [PMID: 19685314 PMCID: PMC2902154 DOI: 10.1007/978-1-60327-321-3_20] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/15/2023]
Abstract
Bioluminescence using the reporter enzyme firefly luciferase (Fluc) and the substrate luciferin enables non-invasive optical imaging of living animals with extremely high sensitivity. This type of analysis enables studies of gene expression, tumor growth, and cell migration over time in live animals that were previously not possible. However, a major limitation of this system is that Fluc activity is restricted to the intracellular environment, which precludes important applications of in vivo imaging such as antibody labeling, or serum protein monitoring. In order to expand the application of bioluminescence imaging to other enzymes, we characterized a sequential reporter-enzyme luminescence (SRL) technology for the in vivo detection of beta-galactosidase (beta-gal) activity. The substrate is a "caged" D-luciferin conjugate that must first be cleaved by beta-gal before it can be catalyzed by Fluc in the final, light-emitting step. Hence, luminescence is dependent on and correlates with beta-gal activity. A variety of experiments were performed in order to validate the system and explore potential new applications. We were able to visualize non-invasively over time constitutive beta-gal activity in engineered cells, as well as inducible tissue-specific beta-gal expression in transgenic mice. Since beta-gal, unlike Fluc, retains full activity outside of cells, we were able to show that antibodies conjugated to the recombinant beta-gal enzyme could be used to detect and localize endogenous cells and extracellular antigens in vivo. In addition, we developed a low-affinity beta-gal complementation system that enables inducible, reversible protein interactions to be monitored in real time in vivo, for example, sequential responses to agonists and antagonists of G-protein-coupled receptors (GPCRs). Thus, using SRL, the exquisite luminescent properties of Fluc can be combined with the advantages of another enzyme. Other substrates have been described that extend the scope to endogenous enzymes, such as cytochromes or caspases, potentially enabling additional unprecedented applications.
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21
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Physiological and pharmacological implications of beta-arrestin regulation. Pharmacol Ther 2008; 121:285-93. [PMID: 19100766 DOI: 10.1016/j.pharmthera.2008.11.005] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2008] [Accepted: 11/18/2008] [Indexed: 02/08/2023]
Abstract
G protein-coupled receptor-targeted drug discovery as well as "compound reassessment" requires the utilization of diverse screens to determine agonist efficacies and potencies beyond the scope of ligand binding and G protein coupling. Such efforts have arisen from extensive studies, both in cellular and animal models, demonstrating that these seven transmembrane domain-spanning, G protein-coupled receptors may engage in more diverse functions than their name suggests and particular focus is drawn to their interactions with beta-arrestins (betaarrestins). As regulators, betaarrestins are involved in dampening G protein-coupling pathways. betaArrestins can also play pro-signaling roles in receptor mediated events and the coupling of receptors to betaarrestins may be as important as their potential to couple to G proteins in the physiological setting. In the last decade, the development of betaarrestin deficient mouse models has allowed for the assessment of the contribution of individual betaarrestins to receptor function in vivo. This review will discuss the current literature that implicates betaarrestins in receptor function in respect to physiological and behavioral responses observed in the live animal model.
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22
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Zhao X, Jones A, Olson KR, Peng K, Wehrman T, Park A, Mallari R, Nebalasca D, Young SW, Xiao SH. A homogeneous enzyme fragment complementation-based beta-arrestin translocation assay for high-throughput screening of G-protein-coupled receptors. ACTA ACUST UNITED AC 2008; 13:737-47. [PMID: 18660457 DOI: 10.1177/1087057108321531] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
G-protein-coupled receptors (GPCRs) represent one of the largest gene families in the human genome and have long been regarded as valuable targets for small-molecule drugs. The authors describe a new functional assay that directly monitors GPCR activation. It is based on the interaction between beta-arrestin and ligand-activated GPCRs and uses enzyme fragment complementation technology. In this format, a GPCR of interest is fused to a small (approximately 4 kDa), optimized alpha fragment peptide (termed ProLink) derived from beta-galactosidase, and beta-arrestin is fused to an N-terminal deletion mutant of beta-galactosidase (termed the enzyme acceptor [EA]). Upon activation of the receptor, the beta-arrestin-EA fusion protein binds the activated GPCR. This interaction drives enzyme fragment complementation, resulting in an active beta-galactosidase enzyme, and thus GPCR activation can be determined by quantifying beta-galactosidase activity. In this report, the authors demonstrate the utility of this technology to monitor GPCR activation and validate the approach using a Galphai-coupled GPCR, somatostatin receptor 2. Potential application to high-throughput screens in both agonist and antagonist screening modes is exemplified.
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Affiliation(s)
- Xiaoning Zhao
- Lead Discovery Department, Chemistry Research and Discovery, Amgen, Inc., South San Francisco, California 94080, USA.
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23
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Abstract
Chemokines and their cognate receptors have key functions in cell growth, survival, and tissue-specific homing of cells. While these functions first were identified in normal immune cells, cancer cells may co-opt chemokine receptor signaling to promote primary tumor growth and metastasis. Our knowledge of signaling by chemokines and chemokine receptors in cancer is lacking, particularly as this signaling occurs in vivo. New insights into chemokine receptor signaling in cancer are needed to understand molecular regulation of primary and metastatic disease and develop targeted therapies to improve patient survival. To meet this need, we have developed a molecular imaging reporter to investigate activation of CXCR4, a chemokine receptor that regulates tumor growth and metastasis in a variety of common cancers. The reporter system uses a firefly luciferase-based protein fragment complementation assay to detect interactions between CXCR4 and beta-arrestin molecules, a common early step in chemokine receptor signaling. In cell-based assays, incubation with the chemokine ligand CXCL12 (SDF-1) produced dose-dependent increases in bioluminescence with >7-fold induction above basal levels of association between these proteins. Reporter activation could be blocked with specific inhibitors of CXCR4 signaling. These reporters enabled in vivo imaging of CXCR4 activation and inhibition in living mice. Overall, this research establishes a new imaging reporter for probing CXCR4 signaling in cancer and other diseases regulated by this chemokine receptor.
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Affiliation(s)
- Kathryn E. Luker
- Center for Molecular Imaging, Department of Radiology, University of Michigan Medical School, Ann Arbor, Michigan 48109
| | - Mudit Gupta
- Center for Molecular Imaging, Department of Radiology, University of Michigan Medical School, Ann Arbor, Michigan 48109
| | - Gary D. Luker
- Center for Molecular Imaging, Department of Radiology, University of Michigan Medical School, Ann Arbor, Michigan 48109
- Center for Molecular Imaging, Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan 48109
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