1
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Shpakov AO. Allosteric Regulation of G-Protein-Coupled Receptors: From Diversity of Molecular Mechanisms to Multiple Allosteric Sites and Their Ligands. Int J Mol Sci 2023; 24:6187. [PMID: 37047169 PMCID: PMC10094638 DOI: 10.3390/ijms24076187] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 03/21/2023] [Accepted: 03/23/2023] [Indexed: 03/29/2023] Open
Abstract
Allosteric regulation is critical for the functioning of G protein-coupled receptors (GPCRs) and their signaling pathways. Endogenous allosteric regulators of GPCRs are simple ions, various biomolecules, and protein components of GPCR signaling (G proteins and β-arrestins). The stability and functional activity of GPCR complexes is also due to multicenter allosteric interactions between protomers. The complexity of allosteric effects caused by numerous regulators differing in structure, availability, and mechanisms of action predetermines the multiplicity and different topology of allosteric sites in GPCRs. These sites can be localized in extracellular loops; inside the transmembrane tunnel and in its upper and lower vestibules; in cytoplasmic loops; and on the outer, membrane-contacting surface of the transmembrane domain. They are involved in the regulation of basal and orthosteric agonist-stimulated receptor activity, biased agonism, GPCR-complex formation, and endocytosis. They are targets for a large number of synthetic allosteric regulators and modulators, including those constructed using molecular docking. The review is devoted to the principles and mechanisms of GPCRs allosteric regulation, the multiplicity of allosteric sites and their topology, and the endogenous and synthetic allosteric regulators, including autoantibodies and pepducins. The allosteric regulation of chemokine receptors, proteinase-activated receptors, thyroid-stimulating and luteinizing hormone receptors, and beta-adrenergic receptors are described in more detail.
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Affiliation(s)
- Alexander O Shpakov
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, 194223 St. Petersburg, Russia
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2
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Leysen H, Walter D, Christiaenssen B, Vandoren R, Harputluoğlu İ, Van Loon N, Maudsley S. GPCRs Are Optimal Regulators of Complex Biological Systems and Orchestrate the Interface between Health and Disease. Int J Mol Sci 2021; 22:ijms222413387. [PMID: 34948182 PMCID: PMC8708147 DOI: 10.3390/ijms222413387] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Revised: 12/08/2021] [Accepted: 12/09/2021] [Indexed: 02/06/2023] Open
Abstract
GPCRs arguably represent the most effective current therapeutic targets for a plethora of diseases. GPCRs also possess a pivotal role in the regulation of the physiological balance between healthy and pathological conditions; thus, their importance in systems biology cannot be underestimated. The molecular diversity of GPCR signaling systems is likely to be closely associated with disease-associated changes in organismal tissue complexity and compartmentalization, thus enabling a nuanced GPCR-based capacity to interdict multiple disease pathomechanisms at a systemic level. GPCRs have been long considered as controllers of communication between tissues and cells. This communication involves the ligand-mediated control of cell surface receptors that then direct their stimuli to impact cell physiology. Given the tremendous success of GPCRs as therapeutic targets, considerable focus has been placed on the ability of these therapeutics to modulate diseases by acting at cell surface receptors. In the past decade, however, attention has focused upon how stable multiprotein GPCR superstructures, termed receptorsomes, both at the cell surface membrane and in the intracellular domain dictate and condition long-term GPCR activities associated with the regulation of protein expression patterns, cellular stress responses and DNA integrity management. The ability of these receptorsomes (often in the absence of typical cell surface ligands) to control complex cellular activities implicates them as key controllers of the functional balance between health and disease. A greater understanding of this function of GPCRs is likely to significantly augment our ability to further employ these proteins in a multitude of diseases.
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Affiliation(s)
- Hanne Leysen
- Receptor Biology Lab, University of Antwerp, 2610 Wilrijk, Belgium; (H.L.); (D.W.); (B.C.); (R.V.); (İ.H.); (N.V.L.)
| | - Deborah Walter
- Receptor Biology Lab, University of Antwerp, 2610 Wilrijk, Belgium; (H.L.); (D.W.); (B.C.); (R.V.); (İ.H.); (N.V.L.)
| | - Bregje Christiaenssen
- Receptor Biology Lab, University of Antwerp, 2610 Wilrijk, Belgium; (H.L.); (D.W.); (B.C.); (R.V.); (İ.H.); (N.V.L.)
| | - Romi Vandoren
- Receptor Biology Lab, University of Antwerp, 2610 Wilrijk, Belgium; (H.L.); (D.W.); (B.C.); (R.V.); (İ.H.); (N.V.L.)
| | - İrem Harputluoğlu
- Receptor Biology Lab, University of Antwerp, 2610 Wilrijk, Belgium; (H.L.); (D.W.); (B.C.); (R.V.); (İ.H.); (N.V.L.)
- Department of Chemistry, Middle East Technical University, Çankaya, Ankara 06800, Turkey
| | - Nore Van Loon
- Receptor Biology Lab, University of Antwerp, 2610 Wilrijk, Belgium; (H.L.); (D.W.); (B.C.); (R.V.); (İ.H.); (N.V.L.)
| | - Stuart Maudsley
- Receptor Biology Lab, University of Antwerp, 2610 Wilrijk, Belgium; (H.L.); (D.W.); (B.C.); (R.V.); (İ.H.); (N.V.L.)
- Correspondence:
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3
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Hilger D. The role of structural dynamics in GPCR‐mediated signaling. FEBS J 2021; 288:2461-2489. [DOI: 10.1111/febs.15841] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Revised: 03/19/2021] [Accepted: 03/24/2021] [Indexed: 12/18/2022]
Affiliation(s)
- Daniel Hilger
- Department of Pharmaceutical Chemistry Philipps‐University Marburg Germany
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4
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van Gastel J, Leysen H, Boddaert J, Vangenechten L, Luttrell LM, Martin B, Maudsley S. Aging-related modifications to G protein-coupled receptor signaling diversity. Pharmacol Ther 2020; 223:107793. [PMID: 33316288 DOI: 10.1016/j.pharmthera.2020.107793] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Accepted: 11/26/2020] [Indexed: 02/06/2023]
Abstract
Aging is a highly complex molecular process, affecting nearly all tissue systems in humans and is the highest risk factor in developing neurodegenerative disorders such as Alzheimer's and Parkinson's disease, cardiovascular disease and Type 2 diabetes mellitus. The intense complexity of the aging process creates an incentive to develop more specific drugs that attenuate or even reverse some of the features of premature aging. As our current pharmacopeia is dominated by therapeutics that target members of the G protein-coupled receptor (GPCR) superfamily it may be prudent to search for effective anti-aging therapeutics in this fertile domain. Since the first demonstration of GPCR-based β-arrestin signaling, it has become clear that an enhanced appreciation of GPCR signaling diversity may facilitate the creation of therapeutics with selective signaling activities. Such 'biased' ligand signaling profiles can be effectively investigated using both standard molecular biological techniques as well as high-dimensionality data analyses. Through a more nuanced appreciation of the quantitative nature across the multiple dimensions of signaling bias that drugs possess, researchers may be able to further refine the efficacy of GPCR modulators to impact the complex aberrations that constitute the aging process. Identifying novel effector profiles could expand the effective pharmacopeia and assist in the design of precision medicines. This review discusses potential non-G protein effectors, and specifically their potential therapeutic suitability in aging and age-related disorders.
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Affiliation(s)
- Jaana van Gastel
- Receptor Biology Lab, Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium; Faculty of Pharmacy, Biomedical and Veterinary Science, University of Antwerp, Antwerp, Belgium
| | - Hanne Leysen
- Receptor Biology Lab, Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium; Faculty of Pharmacy, Biomedical and Veterinary Science, University of Antwerp, Antwerp, Belgium
| | - Jan Boddaert
- Molecular Pathology Group, Faculty of Medicine and Health Sciences, Laboratory of Cell Biology and Histology, Antwerp, Belgium
| | - Laura Vangenechten
- Receptor Biology Lab, Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium
| | - Louis M Luttrell
- Division of Endocrinology, Diabetes & Medical Genetics, Medical University of South Carolina, USA
| | - Bronwen Martin
- Faculty of Pharmacy, Biomedical and Veterinary Science, University of Antwerp, Antwerp, Belgium
| | - Stuart Maudsley
- Receptor Biology Lab, Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium; Faculty of Pharmacy, Biomedical and Veterinary Science, University of Antwerp, Antwerp, Belgium.
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5
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Eddy MT, Martin BT, Wüthrich K. A 2A Adenosine Receptor Partial Agonism Related to Structural Rearrangements in an Activation Microswitch. Structure 2020; 29:170-176.e3. [PMID: 33238145 DOI: 10.1016/j.str.2020.11.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 09/13/2020] [Accepted: 11/03/2020] [Indexed: 12/15/2022]
Abstract
In drug design, G protein-coupled receptor (GPCR) partial agonists enable one to fine-tune receptor output between basal and maximal signaling levels. Here, we add to the structural basis for rationalizing and monitoring partial agonism. NMR spectroscopy of partial agonist complexes of the A2A adenosine receptor (A2AAR) revealed conformations of the P-I-F activation motif that are distinctly different from full agonist complexes. At the intracellular surface, different conformations of helix VI observed for partial and full agonist complexes manifest a correlation between the efficacy-related structural rearrangement of this activation motif and intracellular signaling to partner proteins. While comparisons of A2AAR in complexes with partial and full agonists with different methods showed close similarity of the global folds, this NMR study now reveals subtle but distinct local structural differences related to partial agonism.
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Affiliation(s)
- Matthew T Eddy
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA; Departments of Biological Sciences and Chemistry, Bridge Institute, The University of Southern California, Los Angeles, CA 90089, USA; Department of Chemistry, University of Florida, Gainesville, FL 32611-7200, USA.
| | - Bryan T Martin
- Departments of Biological Sciences and Chemistry, Bridge Institute, The University of Southern California, Los Angeles, CA 90089, USA
| | - Kurt Wüthrich
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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6
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Hilger D, Kumar KK, Hu H, Pedersen MF, O'Brien ES, Giehm L, Jennings C, Eskici G, Inoue A, Lerch M, Mathiesen JM, Skiniotis G, Kobilka BK. Structural insights into differences in G protein activation by family A and family B GPCRs. Science 2020; 369:369/6503/eaba3373. [PMID: 32732395 DOI: 10.1126/science.aba3373] [Citation(s) in RCA: 88] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Accepted: 06/17/2020] [Indexed: 01/06/2023]
Abstract
Family B heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptors (GPCRs) play important roles in carbohydrate metabolism. Recent structures of family B GPCR-Gs protein complexes reveal a disruption in the α-helix of transmembrane segment 6 (TM6) not observed in family A GPCRs. To investigate the functional impact of this structural difference, we compared the structure and function of the glucagon receptor (GCGR; family B) with the β2 adrenergic receptor (β2AR; family A). We determined the structure of the GCGR-Gs complex by means of cryo-electron microscopy at 3.1-angstrom resolution. This structure shows the distinct break in TM6. Guanosine triphosphate (GTP) turnover, guanosine diphosphate release, GTP binding, and G protein dissociation studies revealed much slower rates for G protein activation by the GCGR compared with the β2AR. Fluorescence and double electron-electron resonance studies suggest that this difference is due to the inability of agonist alone to induce a detectable outward movement of the cytoplasmic end of TM6.
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Affiliation(s)
- Daniel Hilger
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA 94305, USA
| | - Kaavya Krishna Kumar
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA 94305, USA
| | - Hongli Hu
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA 94305, USA.,Department of Structural Biology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA 94305, USA
| | | | - Evan S O'Brien
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA 94305, USA
| | - Lise Giehm
- Zealand Pharma A/S, Sydmarken 11, Søborg 2860, Denmark
| | - Christine Jennings
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Gözde Eskici
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA 94305, USA.,Department of Structural Biology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA 94305, USA
| | - Asuka Inoue
- Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan
| | - Michael Lerch
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | | | - Georgios Skiniotis
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA 94305, USA. .,Department of Structural Biology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA 94305, USA.,Department of Photon Science, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, USA
| | - Brian K Kobilka
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA 94305, USA.
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7
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Dahlgren C, Holdfeldt A, Lind S, Mårtensson J, Gabl M, Björkman L, Sundqvist M, Forsman H. Neutrophil Signaling That Challenges Dogmata of G Protein-Coupled Receptor Regulated Functions. ACS Pharmacol Transl Sci 2020; 3:203-220. [PMID: 32296763 DOI: 10.1021/acsptsci.0c00004] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Indexed: 12/24/2022]
Abstract
Activation as well as recruitment of neutrophils, the most abundant leukocyte in human blood, to sites of infection/inflammation largely rely on surface-exposed chemoattractant receptors. These receptors belong to the family of 7-transmembrane domain receptors also known as G protein-coupled receptors (GPCRs) due to the fact that part of the downstream signaling relies on an activation of heterotrimeric G proteins. The neutrophil GPCRs share significant sequence homologies but bind many structurally diverse activating (agonistic) and inhibiting (antagonistic) ligands, ranging from fatty acids to purines, peptides, and lipopeptides. Recent structural and functional studies of neutrophil receptors have generated important information on GPCR biology in general; this knowledge aids in the overall understanding of general pharmacological principles, governing regulation of neutrophil function and inflammatory processes, including novel leukocyte receptor activities related to ligand recognition, biased/functional selective signaling, allosteric modulation, desensitization mechanisms and reactivation, and communication (cross-talk) between GPCRs. This review summarizes the recent discoveries and pharmacological hallmarks with focus on neutrophil GPCRs. In addition, unmet challenges are dealt with, including recognition by the receptors of diverse ligands and how biased signaling mediates different biological effects.
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Affiliation(s)
- Claes Dahlgren
- Department of Rheumatology and Inflammation Research, University of Göteborg, Göteborg 405 30, Sweden
| | - André Holdfeldt
- Department of Rheumatology and Inflammation Research, University of Göteborg, Göteborg 405 30, Sweden
| | - Simon Lind
- Department of Rheumatology and Inflammation Research, University of Göteborg, Göteborg 405 30, Sweden
| | - Jonas Mårtensson
- Department of Rheumatology and Inflammation Research, University of Göteborg, Göteborg 405 30, Sweden
| | - Michael Gabl
- Department of Rheumatology and Inflammation Research, University of Göteborg, Göteborg 405 30, Sweden
| | - Lena Björkman
- Department of Rheumatology and Inflammation Research, University of Göteborg, Göteborg 405 30, Sweden
| | - Martina Sundqvist
- Department of Rheumatology and Inflammation Research, University of Göteborg, Göteborg 405 30, Sweden
| | - Huamei Forsman
- Department of Rheumatology and Inflammation Research, University of Göteborg, Göteborg 405 30, Sweden
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8
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Hilger D, Masureel M, Kobilka BK. Structure and dynamics of GPCR signaling complexes. Nat Struct Mol Biol 2018; 25:4-12. [PMID: 29323277 PMCID: PMC6535338 DOI: 10.1038/s41594-017-0011-7] [Citation(s) in RCA: 564] [Impact Index Per Article: 94.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Accepted: 11/21/2017] [Indexed: 12/16/2022]
Abstract
G-protein-coupled receptors (GPCRs) relay numerous extracellular signals by triggering intracellular signaling through coupling with G proteins and arrestins. Recent breakthroughs in the structural determination of GPCRs and GPCR-transducer complexes represent important steps toward deciphering GPCR signal transduction at a molecular level. A full understanding of the molecular basis of GPCR-mediated signaling requires elucidation of the dynamics of receptors and their transducer complexes as well as their energy landscapes and conformational transition rates. Here, we summarize current insights into the structural plasticity of GPCR-G-protein and GPCR-arrestin complexes that underlies the regulation of the receptor's intracellular signaling profile.
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Affiliation(s)
- Daniel Hilger
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Matthieu Masureel
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Brian K Kobilka
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA.
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9
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Grundmann M, Kostenis E. Temporal Bias: Time-Encoded Dynamic GPCR Signaling. Trends Pharmacol Sci 2017; 38:1110-1124. [PMID: 29074251 DOI: 10.1016/j.tips.2017.09.004] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Revised: 09/24/2017] [Accepted: 09/25/2017] [Indexed: 12/21/2022]
Abstract
Evidence suggests that cells can time-encode signals for secure transport and perception of information, and it appears that this dynamic signaling is a common principle of nature to code information in time. G-protein-coupled receptor (GPCR) signaling networks are no exception as their composition and signal transduction appear temporally flexible. In this review, we discuss the potential mechanisms by which GPCRs code biological information in time to create 'temporal bias.' We highlight dynamic signaling patterns from the second messenger to the receptor-ligand level and shed light on the dynamics of G-protein cycles, the kinetics of ligand-receptor interaction, and the occurrence of distinct signaling waves within the cell. A dynamic feature such as temporal bias adds to the complexity of GPCR signaling bias and gives rise to the question whether this trait could be exploited to gain control over time-encoded cell physiology.
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Affiliation(s)
- Manuel Grundmann
- Molecular-, Cellular- and Pharmacobiology Section, Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany; Kidney Disease Research, Bayer Pharma AG, Aprather Weg 18a, 42113 Wuppertal, Germany
| | - Evi Kostenis
- Molecular-, Cellular- and Pharmacobiology Section, Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany.
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10
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Ligand-Dependent Modulation of G Protein Conformation Alters Drug Efficacy. Cell 2016; 167:739-749.e11. [PMID: 27720449 DOI: 10.1016/j.cell.2016.09.021] [Citation(s) in RCA: 102] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Revised: 07/28/2016] [Accepted: 09/08/2016] [Indexed: 11/21/2022]
Abstract
G protein-coupled receptor (GPCR) signaling, mediated by hetero-trimeric G proteins, can be differentially controlled by agonists. At a molecular level, this is thought to occur principally via stabilization of distinct receptor conformations by individual ligands. These distinct conformations control subsequent recruitment of transducer and effector proteins. Here, we report that ligand efficacy at the calcitonin GPCR (CTR) is also correlated with ligand-dependent alterations to G protein conformation. We observe ligand-dependent differences in the sensitivity of the G protein ternary complex to disruption by GTP, due to conformational differences in the receptor-bound G protein hetero-trimer. This results in divergent agonist-dependent receptor-residency times for the hetero-trimeric G protein and different accumulation rates for downstream second messengers. This study demonstrates that factors influencing efficacy extend beyond receptor conformation(s) and expands understanding of the molecular basis for how G proteins control/influence efficacy. This has important implications for the mechanisms that underlie ligand-mediated biased agonism. VIDEO ABSTRACT.
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11
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Schmitz AL, Schrage R, Gaffal E, Charpentier TH, Wiest J, Hiltensperger G, Morschel J, Hennen S, Häußler D, Horn V, Wenzel D, Grundmann M, Büllesbach KM, Schröder R, Brewitz HH, Schmidt J, Gomeza J, Galés C, Fleischmann BK, Tüting T, Imhof D, Tietze D, Gütschow M, Holzgrabe U, Sondek J, Harden TK, Mohr K, Kostenis E. A cell-permeable inhibitor to trap Gαq proteins in the empty pocket conformation. ACTA ACUST UNITED AC 2015; 21:890-902. [PMID: 25036778 DOI: 10.1016/j.chembiol.2014.06.003] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2014] [Revised: 06/04/2014] [Accepted: 06/09/2014] [Indexed: 12/18/2022]
Abstract
In spite of the crucial role of heterotrimeric G proteins as molecular switches transmitting signals from G protein-coupled receptors, their selective manipulation with small molecule, cell-permeable inhibitors still remains an unmet challenge. Here, we report that the small molecule BIM-46187, previously classified as pan-G protein inhibitor, preferentially silences Gαq signaling in a cellular context-dependent manner. Investigations into its mode of action reveal that BIM traps Gαq in the empty pocket conformation by permitting GDP exit but interdicting GTP entry, a molecular mechanism not yet assigned to any other small molecule Gα inhibitor to date. Our data show that Gα proteins may be "frozen" pharmacologically in an intermediate conformation along their activation pathway and propose a pharmacological strategy to specifically silence Gα subclasses with cell-permeable inhibitors.
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Affiliation(s)
- Anna-Lena Schmitz
- Molecular, Cellular, and Pharmacobiology Section, Institute of Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany
| | - Ramona Schrage
- Pharmacology and Toxicology Section, Institute of Pharmacy, University of Bonn, Gerhard-Domagk-Straße 3, 53121 Bonn, Germany
| | - Evelyn Gaffal
- Department of Dermatology and Allergy, Laboratory of Experimental Dermatology, University of Bonn, Sigmund-Freud-Straße 25, 53105 Bonn, Germany
| | - Thomas H Charpentier
- Department of Pharmacology, School of Medicine, University of North Carolina, Chapel Hill, NC 27599-7365, USA
| | - Johannes Wiest
- Pharmaceutical and Medicinal Chemistry, Institute of Pharmacy and Food Chemistry, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Georg Hiltensperger
- Pharmaceutical and Medicinal Chemistry, Institute of Pharmacy and Food Chemistry, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Julia Morschel
- Molecular, Cellular, and Pharmacobiology Section, Institute of Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany
| | - Stephanie Hennen
- Molecular, Cellular, and Pharmacobiology Section, Institute of Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany
| | - Daniela Häußler
- Pharmaceutical Chemistry I, Institute of Pharmacy, University of Bonn, An der Immenburg 4, 53121 Bonn, Germany
| | - Velten Horn
- Eduard-Zintl-Institute of Inorganic and Physical Chemistry, Technische Universität Darmstadt, Alarich-Weiss-Straße 8, 64287 Darmstadt, Germany
| | - Daniela Wenzel
- Institute of Physiology I, Life and Brain Center, University of Bonn, Sigmund-Freud-Straße 25, 53105 Bonn, Germany
| | - Manuel Grundmann
- Molecular, Cellular, and Pharmacobiology Section, Institute of Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany
| | - Katrin M Büllesbach
- Molecular, Cellular, and Pharmacobiology Section, Institute of Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany
| | - Ralf Schröder
- Molecular, Cellular, and Pharmacobiology Section, Institute of Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany
| | - H Henning Brewitz
- Pharmaceutical Chemistry I, Institute of Pharmacy, University of Bonn, Brühler Straße 7, 53119 Bonn, Germany
| | - Johannes Schmidt
- Molecular, Cellular, and Pharmacobiology Section, Institute of Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany
| | - Jesús Gomeza
- Molecular, Cellular, and Pharmacobiology Section, Institute of Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany
| | - Céline Galés
- Institut des Maladies Métaboliques et Cardiovasculaires, Institut Nataional de la Santé et de la Recherche Médicale, Université Toulouse III Paul Sabatier, 31432 Toulouse, France
| | - Bernd K Fleischmann
- Institute of Physiology I, Life and Brain Center, University of Bonn, Sigmund-Freud-Straße 25, 53105 Bonn, Germany
| | - Thomas Tüting
- Department of Dermatology and Allergy, Laboratory of Experimental Dermatology, University of Bonn, Sigmund-Freud-Straße 25, 53105 Bonn, Germany
| | - Diana Imhof
- Pharmaceutical Chemistry I, Institute of Pharmacy, University of Bonn, Brühler Straße 7, 53119 Bonn, Germany
| | - Daniel Tietze
- Eduard-Zintl-Institute of Inorganic and Physical Chemistry, Technische Universität Darmstadt, Alarich-Weiss-Straße 8, 64287 Darmstadt, Germany
| | - Michael Gütschow
- Pharmaceutical Chemistry I, Institute of Pharmacy, University of Bonn, An der Immenburg 4, 53121 Bonn, Germany
| | - Ulrike Holzgrabe
- Pharmaceutical and Medicinal Chemistry, Institute of Pharmacy and Food Chemistry, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - John Sondek
- Department of Pharmacology and Department of Biochemistry and Biophysics and Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, NC 27599-7365, United States
| | - T Kendall Harden
- Department of Pharmacology, School of Medicine, University of North Carolina, Chapel Hill, NC 27599-7365, USA
| | - Klaus Mohr
- Pharmacology and Toxicology Section, Institute of Pharmacy, University of Bonn, Gerhard-Domagk-Straße 3, 53121 Bonn, Germany
| | - Evi Kostenis
- Molecular, Cellular, and Pharmacobiology Section, Institute of Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany.
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12
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Woo AYH, Song Y, Zhu W, Xiao RP. Advances in receptor conformation research: the quest for functionally selective conformations focusing on the β2-adrenoceptor. Br J Pharmacol 2015; 172:5477-88. [PMID: 25537131 DOI: 10.1111/bph.13049] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Accepted: 12/14/2014] [Indexed: 01/14/2023] Open
Abstract
Seven-transmembrane receptors, also called GPCRs, represent the largest class of drug targets. Upon ligand binding, a GPCR undergoes conformational rearrangement and thereby changes its interaction with effector proteins including the cognate G-proteins and the multifunctional adaptor proteins, β-arrestins. These proteins, by initiating distinct signal transduction mechanisms, mediate one or several functional responses. Recently, the concept of ligand-directed GPCR signalling, also called functional selectivity or biased agonism, has been proposed to explain the phenomenon that chemically diverse ligands exhibit different efficacies towards the different signalling pathways of a single GPCR, and thereby act as functionally selective or 'biased' ligands. Current concepts support the notion that ligand-specific GPCR conformations are the basis of ligand-directed signalling. Multiple studies using fluorescence spectroscopy, X-ray crystallography, mass spectroscopy, nuclear magnetic resonance spectroscopy, single-molecule force spectroscopy and other techniques have provided the evidence to support this notion. It is anticipated that these techniques will ultimately help elucidate the structural basis of ligand-directed GPCR signalling at a precision meaningful for structure-based drug design and how a specific ligand molecular structure induces a unique receptor conformation leading to biased signalling. In this review, we will summarize recent advances in experimental techniques applied in the study of functionally selective GPCR conformations and breakthrough data obtained in these studies particularly those of the β2-adrenoceptor.
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Affiliation(s)
- Anthony Yiu-Ho Woo
- Institute of Molecular Medicine, Centre for Life Sciences, Peking University, Beijing, China.,Key Laboratory of Chemical Genomics, School of Chemical Biology and Biotechnology, Peking University Shenzhen Graduate School, Shenzhen, China
| | - Ying Song
- Institute of Molecular Medicine, Centre for Life Sciences, Peking University, Beijing, China
| | - Weizhong Zhu
- Department of Pharmacology, Nantong University School of Pharmacy, Nantong, China
| | - Rui-Ping Xiao
- Institute of Molecular Medicine, Centre for Life Sciences, Peking University, Beijing, China.,Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Peking University, Beijing, China
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Interaction of fenoterol stereoisomers with β2-adrenoceptor-G sα fusion proteins: antagonist and agonist competition binding. Naunyn Schmiedebergs Arch Pharmacol 2015; 388:517-24. [PMID: 25637582 DOI: 10.1007/s00210-015-1086-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Accepted: 01/09/2015] [Indexed: 10/24/2022]
Abstract
The specific interaction between G-protein-coupled receptors and ligand is the starting point for downstream signaling. Fenoterol stereoisomers were successfully used to probe ligand-specific activation (functional selectivity) of the β2-adrenoceptor (β2AR) (Reinartz et al. 2015). In the present study, we extended the pharmacological profile of fenoterol stereoisomers using β2AR-Gsα fusion proteins in agonist and antagonist competition binding assays. Dissociations between binding affinities and effector potencies were found for (R,S')- and (S,S')-isomers of 4'-methoxy-1-naphthyl-fenoterol. Our data corroborate former studies on the importance of the aminoalkyl moiety of fenoterol derivatives for functional selectivity.
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Seifert R, Schneider EH, Bähre H. From canonical to non-canonical cyclic nucleotides as second messengers: pharmacological implications. Pharmacol Ther 2014; 148:154-84. [PMID: 25527911 DOI: 10.1016/j.pharmthera.2014.12.002] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Accepted: 12/11/2014] [Indexed: 02/07/2023]
Abstract
This review summarizes our knowledge on the non-canonical cyclic nucleotides cCMP, cUMP, cIMP, cXMP and cTMP. We place the field into a historic context and discuss unresolved questions and future directions of research. We discuss the implications of non-canonical cyclic nucleotides for experimental and clinical pharmacology, focusing on bacterial infections, cardiovascular and neuropsychiatric disorders and reproduction medicine. The canonical cyclic purine nucleotides cAMP and cGMP fulfill the criteria of second messengers. (i) cAMP and cGMP are synthesized by specific generators, i.e. adenylyl and guanylyl cyclases, respectively. (ii) cAMP and cGMP activate specific effector proteins, e.g. protein kinases. (iii) cAMP and cGMP exert specific biological effects. (iv) The biological effects of cAMP and cGMP are terminated by phosphodiesterases and export. The effects of cAMP and cGMP are mimicked by (v) membrane-permeable cyclic nucleotide analogs and (vi) bacterial toxins. For decades, the existence and relevance of cCMP and cUMP have been controversial. Modern mass-spectrometric methods have unequivocally demonstrated the existence of cCMP and cUMP in mammalian cells. For both, cCMP and cUMP, the criteria for second messenger molecules are now fulfilled as well. There are specific patterns by which nucleotidyl cyclases generate cNMPs and how they are degraded and exported, resulting in unique cNMP signatures in biological systems. cNMP signaling systems, specifically at the level of soluble guanylyl cyclase, soluble adenylyl cyclase and ExoY from Pseudomonas aeruginosa are more promiscuous than previously appreciated. cUMP and cCMP are evolutionary new molecules, probably reflecting an adaption to signaling requirements in higher organisms.
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Affiliation(s)
- Roland Seifert
- Institute of Pharmacology, Hannover Medical School, D-30625 Hannover, Germany.
| | - Erich H Schneider
- Institute of Pharmacology, Hannover Medical School, D-30625 Hannover, Germany
| | - Heike Bähre
- Institute of Pharmacology, Hannover Medical School, D-30625 Hannover, Germany
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Structure-bias relationships for fenoterol stereoisomers in six molecular and cellular assays at the β2-adrenoceptor. Naunyn Schmiedebergs Arch Pharmacol 2014; 388:51-65. [PMID: 25342094 DOI: 10.1007/s00210-014-1054-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Accepted: 10/02/2014] [Indexed: 01/14/2023]
Abstract
Functional selectivity is well established as an underlying concept of ligand-specific signaling via G protein-coupled receptors (GPCRs). Functionally, selective drugs could show greater therapeutic efficacy and fewer adverse effects. Dual coupling of the β2-adrenoceptor (β2AR) triggers a signal transduction via Gsα and Giα proteins. Here, we examined 12 fenoterol stereoisomers in six molecular and cellular assays. Using β2AR-Gsα and β2AR-Giα fusion proteins, (R,S')- and (S,S')-isomers of 4'-methoxy-1-naphthyl-fenoterol were identified as biased ligands with preference for Gs. G protein-independent signaling via β-arrestin-2 was disfavored by these ligands. Isolated human neutrophils constituted an ex vivo model of β2AR signaling and demonstrated functional selectivity through the dissociation of cAMP accumulation and the inhibition of formyl peptide-stimulated production of reactive oxygen species. Ligand bias was calculated using an operational model of agonism and revealed that the fenoterol scaffold constitutes a promising lead structure for the development of Gs-biased β2AR agonists.
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Plazinska A, Plazinski W, Jozwiak K. Fast, metadynamics-based method for prediction of the stereochemistry-dependent relative free energies of ligand-receptor interactions. J Comput Chem 2014; 35:876-82. [PMID: 24615679 DOI: 10.1002/jcc.23563] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Revised: 01/30/2014] [Accepted: 02/01/2014] [Indexed: 01/09/2023]
Abstract
The computational approach applicable for the molecular dynamics (MD)-based techniques is proposed to predict the ligand-protein binding affinities dependent on the ligand stereochemistry. All possible stereoconfigurations are expressed in terms of one set of force-field parameters [stereoconfiguration-independent potential (SIP)], which allows for calculating all relative free energies by only single simulation. SIP can be used for studying diverse, stereoconfiguration-dependent phenomena by means of various computational techniques of enhanced sampling. The method has been successfully tested on the β2-adrenergic receptor (β2-AR) binding the four fenoterol stereoisomers by both metadynamics simulations and replica-exchange MD. Both the methods gave very similar results, fully confirming the presence of stereoselective effects in the fenoterol-β2-AR interactions. However, the metadynamics-based approach offered much better efficiency of sampling which allows for significant reduction of the unphysical region in SIP.
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Affiliation(s)
- Anita Plazinska
- Department of Chemistry, Faculty of Pharmacy, Laboratory of Medicinal Chemistry and Neuroengineering, Medical University of Lublin, W. Chodzki Street, 4a, 20-093, Lublin, Poland
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Ferrie AM, Sun H, Zaytseva N, Fang Y. Divergent label-free cell phenotypic pharmacology of ligands at the overexpressed β₂-adrenergic receptors. Sci Rep 2014; 4:3828. [PMID: 24451999 PMCID: PMC3899747 DOI: 10.1038/srep03828] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Accepted: 01/06/2014] [Indexed: 01/14/2023] Open
Abstract
We present subclone sensitive cell phenotypic pharmacology of ligands at the β2-adrenergic receptor (β2-AR) stably expressed in HEK-293 cells. The parental cell line was transfected with green fluorescent protein (GFP)-tagged β2-AR. Four stable subclones were established and used to profile a library of sixty-nine AR ligands. Dynamic mass redistribution (DMR) profiling resulted in a pharmacological activity map suggesting that HEK293 endogenously expresses functional Gi-coupled α2-AR and Gs-coupled β2-AR, and the label-free cell phenotypic activity of AR ligands are subclone dependent. Pathway deconvolution revealed that the DMR of epinephrine is originated mostly from the remodeling of actin microfilaments and adhesion complexes, to less extent from the microtubule networks and receptor trafficking, and certain agonists displayed different efficacy towards the cAMP-Epac pathway. We demonstrate that receptor signaling and ligand pharmacology is sensitive to the receptor expression level, and the organization of the receptor and its signaling circuitry.
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Affiliation(s)
- Ann M Ferrie
- 1] Biochemical Technologies, Science and Technology Division, Corning Incorporated, Corning, NY 14831, United States of America [2]
| | - Haiyan Sun
- 1] Biochemical Technologies, Science and Technology Division, Corning Incorporated, Corning, NY 14831, United States of America [2] [3]
| | - Natalya Zaytseva
- Biochemical Technologies, Science and Technology Division, Corning Incorporated, Corning, NY 14831, United States of America
| | - Ye Fang
- Biochemical Technologies, Science and Technology Division, Corning Incorporated, Corning, NY 14831, United States of America
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18
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Luttrell LM. Minireview: More than just a hammer: ligand "bias" and pharmaceutical discovery. Mol Endocrinol 2014; 28:281-94. [PMID: 24433041 DOI: 10.1210/me.2013-1314] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Conventional orthosteric drug development programs targeting G protein-coupled receptors (GPCRs) have focused on the concepts of agonism and antagonism, in which receptor structure determines the nature of the downstream signal and ligand efficacy determines its intensity. Over the past decade, the emerging paradigms of "pluridimensional efficacy" and "functional selectivity" have revealed that GPCR signaling is not monolithic, and that ligand structure can "bias" signal output by stabilizing active receptor states in different proportions than the native ligand. Biased ligands are novel pharmacologic entities that possess the unique ability to qualitatively change GPCR signaling, in effect creating "new receptors" with distinct efficacy profiles driven by ligand structure. The promise of biased agonism lies in this ability to engender "mixed" effects not attainable using conventional agonists or antagonists, promoting therapeutically beneficial signals while antagonizing deleterious ones. Indeed, arrestin pathway-selective agonists for the type 1 parathyroid hormone and angiotensin AT1 receptors, and G protein pathway-selective agonists for the GPR109A nicotinic acid and μ-opioid receptors, have demonstrated unique, and potentially therapeutic, efficacy in cell-based assays and preclinical animal models. Conversely, activating GPCRs in "unnatural" ways may lead to downstream biological consequences that cannot be predicted from prior knowledge of the actions of the native ligand, especially in the case of ligands that selectively activate as-yet poorly characterized G protein-independent signaling networks mediated via arrestins. Although much needs to be done to realize the clinical potential of functional selectivity, biased GPCR ligands nonetheless appear to be important new additions to the pharmacologic toolbox.
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Affiliation(s)
- Louis M Luttrell
- Department of Medicine and Department of Biochemistry & Molecular Biology, Medical University of South Carolina, Charleston, South Carolina 29425; and Ralph H. Johnson Veterans Affairs Medical Center, Charleston, South Carolina 29401
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Seifert R. Functional selectivity of G-protein-coupled receptors: from recombinant systems to native human cells. Biochem Pharmacol 2013; 86:853-61. [PMID: 23933388 DOI: 10.1016/j.bcp.2013.07.029] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2013] [Revised: 07/25/2013] [Accepted: 07/25/2013] [Indexed: 10/26/2022]
Abstract
In the mid 1990s, it was assumed that a two-state model, postulating an inactive (R) state and an active (R*) state provides the molecular basis for GPCR activation. However, it became clear that this model could not accommodate many experimental observations. Accordingly, the two-state model was superseded by a multi-state model according to which any given ligand stabilizes a unique receptor conformation with distinct capabilities of activating down-stream G-proteins and β-arrestin. Much of this research was conducted with the β2-adrenoceptor in recombinant systems. At the molecular level, there is now no doubt anymore that ligand-specific receptor conformations, also referred to as functional selectivity, exist. This concept holds great potential for drug discovery in terms of developing drugs with higher selectivity for specific cells and/or cell functions and fewer side effects. A major challenge is the analysis for functional selectivity in native cells. Here, I discuss our current knowledge on functional selectivity of three representative GPCRs, the β2-adrenoceptor and the histamine H2- and H4-receptors, in recombinant systems and native human cells. Studies with human neutrophils and eosinophils support the concept of functional selectivity. A major strategy for the analysis of functional selectivity in native cells is to generate complete concentration/response curves with a large set of structurally diverse ligands for multiple parameters. Next, correlations of potencies and efficacies are analyzed, and deviations of the correlations from linearity are indicative for functional selectivity. Additionally, pharmacological inhibitors are used to dissect cell functions from each other.
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Affiliation(s)
- Roland Seifert
- Institute of Pharmacology, Medical School of Hannover, Carl-Neuberg-Str. 1, D-30625 Hannover, Germany.
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Brunskole Hummel I, Reinartz MT, Kälble S, Burhenne H, Schwede F, Buschauer A, Seifert R. Dissociations in the effects of β2-adrenergic receptor agonists on cAMP formation and superoxide production in human neutrophils: support for the concept of functional selectivity. PLoS One 2013; 8:e64556. [PMID: 23741338 PMCID: PMC3669315 DOI: 10.1371/journal.pone.0064556] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2013] [Accepted: 04/15/2013] [Indexed: 12/02/2022] Open
Abstract
In neutrophils, activation of the β2-adrenergic receptor (β2AR), a Gs-coupled receptor, inhibits inflammatory responses, which could be therapeutically exploited. The aim of this study was to evaluate the effects of various β2AR ligands on adenosine-3',5'-cyclic monophosphate (cAMP) accumulation and N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP)-induced superoxide anion (O2(•-)) production in human neutrophils and to probe the concept of ligand-specific receptor conformations (also referred to as functional selectivity or biased signaling) in a native cell system. This is an important question because so far, evidence for functional selectivity has been predominantly obtained with recombinant systems, due to the inherent difficulties to genetically manipulate human native cells. cAMP concentration was determined by HPLC/tandem mass spectrometry, and O2(•-) formation was assessed by superoxide dismutase-inhibitable reduction of ferricytochrome c. β2AR agonists were generally more potent in inhibiting fMLP-induced O2(•-) production than in stimulating cAMP accumulation. (-)-Ephedrine and dichloroisoproterenol were devoid of any agonistic activity in the cAMP assay, but partially inhibited fMLP-induced O2(•-) production. Moreover, (-)-adrenaline was equi-efficacious in both assays whereas the efficacy of salbutamol was more than two-fold higher in the O2(•-) assay. Functional selectivity was visualized by deviations of ligand potencies and efficacies from linear correlations for various parameters. We obtained no evidence for involvement of protein kinase A in the inhibition of fMLP-induced O2(•-) production after β2AR-stimulation although cAMP-increasing substances inhibited O2(•-) production. Taken together, our data corroborate the concept of ligand-specific receptor conformations with unique signaling capabilities in native human cells and suggest that the β2AR inhibits O2(•-) production in a cAMP-independent manner.
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Affiliation(s)
- Irena Brunskole Hummel
- Institute of Pharmacology, Medical School of Hannover, Hannover, Germany
- Department of Pharmaceutical and Medicinal Chemistry II, University of Regensburg, Regensburg, Germany
| | | | - Solveig Kälble
- Institute of Pharmacology, Medical School of Hannover, Hannover, Germany
| | - Heike Burhenne
- Institute of Pharmacology, Medical School of Hannover, Hannover, Germany
| | | | - Armin Buschauer
- Department of Pharmaceutical and Medicinal Chemistry II, University of Regensburg, Regensburg, Germany
| | - Roland Seifert
- Institute of Pharmacology, Medical School of Hannover, Hannover, Germany
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Lefkowitz RJ. Arrestins Come of Age. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2013; 118:3-18. [DOI: 10.1016/b978-0-12-394440-5.00001-2] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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22
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Barandun LJ, Immekus F, Kohler PC, Tonazzi S, Wagner B, Wendelspiess S, Ritschel T, Heine A, Kansy M, Klebe G, Diederich F. From lin-benzoguanines to lin-benzohypoxanthines as ligands for Zymomonas mobilis tRNA-guanine transglycosylase: replacement of protein-ligand hydrogen bonding by importing water clusters. Chemistry 2012; 18:9246-57. [PMID: 22736391 DOI: 10.1002/chem.201200809] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2012] [Indexed: 11/12/2022]
Abstract
The foodborne illness shigellosis is caused by Shigella bacteria that secrete the highly cytotoxic Shiga toxin, which is also formed by the closely related enterohemorrhagic Escherichia coli (EHEC). It has been shown that tRNA-guanine transglycosylase (TGT) is essential for the pathogenicity of Shigella flexneri. Herein, the molecular recognition properties of a guanine binding pocket in Zymomonas mobilis TGT are investigated with a series of lin-benzohypoxanthine- and lin-benzoguanine-based inhibitors that bear substituents to occupy either the ribose-33 or the ribose-34 pocket. The three inhibitor scaffolds differ by the substituent at C(6) being H, NH(2), or NH-alkyl. These differences lead to major changes in the inhibition constants, pK(a) values, and binding modes. Compared to the lin-benzoguanines, with an exocyclic NH(2) at C(6), the lin-benzohypoxanthines without an exocyclic NH(2) group have a weaker affinity as several ionic protein-ligand hydrogen bonds are lost. X-ray cocrystal structure analysis reveals that a new water cluster is imported into the space vacated by the lacking NH(2) group and by a conformational shift of the side chain of catalytic Asp102. In the presence of an N-alkyl group at C(6) in lin-benzoguanine ligands, this water cluster is largely maintained but replacement of one of the water molecules in the cluster leads to a substantial loss in binding affinity. This study provides new insight into the role of water clusters at enzyme active sites and their challenging substitution by ligand parts, a topic of general interest in contemporary structure-based drug design.
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Affiliation(s)
- Luzi Jakob Barandun
- Laboratorium für Organische Chemie, ETH Zürich, Hönggerberg, HCI, 8093 Zurich, Switzerland
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Hübner M, Dixit A, Mou TC, Lushington GH, Pinto C, Gille A, Geduhn J, König B, Sprang SR, Seifert R. Structural basis for the high-affinity inhibition of mammalian membranous adenylyl cyclase by 2',3'-o-(N-methylanthraniloyl)-inosine 5'-triphosphate. Mol Pharmacol 2011; 80:87-96. [PMID: 21498658 DOI: 10.1124/mol.111.071894] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
2',3'-O-(N-Methylanthraniloyl)-ITP (MANT-ITP) is the most potent inhibitor of mammalian membranous adenylyl cyclase (mAC) 5 (AC5, K(i), 1 nM) yet discovered and surpasses the potency of MANT-GTP by 55-fold (J Pharmacol Exp Ther 329:1156-1165, 2009). AC5 inhibitors may be valuable drugs for treatment of heart failure. The aim of this study was to elucidate the structural basis for the high-affinity inhibition of mAC by MANT-ITP. MANT-ITP was a considerably more potent inhibitor of the purified catalytic domains VC1 and IIC2 of mAC than MANT-GTP (K(i), 0.7 versus 18 nM). Moreover, there was considerably more efficient fluorescence resonance energy transfer between Trp1020 of IIC2 and the MANT group of MANT-ITP compared with MANT-GTP, indicating optimal interaction of the MANT group of MANT-ITP with the hydrophobic pocket. The crystal structure of MANT-ITP in complex with the G(s)α- and forskolin-activated catalytic domains VC1:IIC2 compared with the existing MANT-GTP crystal structure revealed only subtle differences in binding mode. The higher affinity of MANT-ITP to mAC compared with MANT-GTP is probably due to fewer stereochemical constraints upon the nucleotide base in the purine binding pocket, allowing a stronger interaction with the hydrophobic regions of IIC2 domain, as assessed by fluorescence spectroscopy. Stronger interaction is also achieved in the phosphate-binding site. The triphosphate group of MANT-ITP exhibits better metal coordination than the triphosphate group of MANT-GTP, as confirmed by molecular dynamics simulations. Collectively, the subtle differences in ligand structure have profound effects on affinity for mAC.
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Affiliation(s)
- Melanie Hübner
- Department of Pharmacology and Toxicology, University of Regensburg, Regensburg, Germany
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Abstract
In many cases, the coexpression of GPCRs with G-proteins and/or regulators of G-protein signaling (RGS-proteins) allows a successful reconstitution of high-affinity agonist binding and functional responses. However, in some cases, coexpressed GPCRs and G-proteins interact inefficiently, resulting in weak [³⁵S]GTPγS- and steady-state GTPase assay signals. This may be, for example, caused by a rapid dissociation of the G-protein from the plasma membrane, as has been reported for Gα(s). Moreover, for a detailed characterization of GPCR/G-protein interactions, it may be required to work with a defined GPCR/G-protein stoichiometry and to avoid cross-interaction with endogenous G-proteins. Cross-talk to endogenous G-proteins has been shown to play a role in some mammalian expression systems. These problems can be addressed by the generation of GPCR-Gα fusion proteins and their expression in Sf9 insect cells. When the C-terminus of the receptor is fused to the N-terminus of the G-protein, a 1:1 stoichiometry of both proteins is achieved. In addition, the close proximity of GPCR and G-protein in fusion proteins leads to enhanced interaction efficiency, resulting in increased functional signals. This approach can also be extended to fusion proteins of GPCRs with RGS-proteins, specifically when steady-state GTP hydrolysis is used as read-out. GPCR-RGS fusion proteins optimize the interaction of RGS-proteins with coexpressed Gα subunits, since the location of the RGS-protein is close to the site of receptor-mediated G-protein activation. Moreover, in contrast to coexpression systems, GPCR-Gα and GPCR-RGS fusion proteins provide a possibility to imitate physiologically occurring interactions, for example, the precoupling of receptors and G-proteins or the formation of complexes between GPCRs, G-proteins and RGS-proteins (transducisomes). In this chapter, we describe the technique for the generation of fusion proteins and show the application of this approach for the characterization of constitutively active receptors.
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Vilardaga JP. Theme and variations on kinetics of GPCR activation/deactivation. J Recept Signal Transduct Res 2011; 30:304-12. [PMID: 20836728 DOI: 10.3109/10799893.2010.509728] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
G protein-coupled receptors (GPCRs) initiate intracellular signaling pathways in response to physiologically and medically important extracellular ligands such as peptide and large glycoprotein hormones, neurotransmitters, sensory stimuli (odorant and taste molecules, light), calcium, l-amino acids, and are the target of many clinical drugs. The conversion of these extracellular stimuli into intracellular signals involves sequential and reversible reactions that initially take place at the plasma membrane. These reactions are mediated not only by dynamic interactions between ligands, receptors and heterotrimeric G proteins, but also by conformational changes associated with the activation/deactivation process of each protein. This review discusses the kinetic characteristics and rate-limiting reactions engaged in signal propagation that are involved in systems as diverse as neurotransmitter and hormonal signaling, and that have been recorded in live cells by Förster resonance energy transfer (FRET) approaches.
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Affiliation(s)
- Jean-Pierre Vilardaga
- Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh, School of Medicine, Pittsburgh, PA 15261, USA.
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Abstract
Receptors on the surface of cells function as conduits for information flowing between the external environment and the cell interior. Since signal transduction is based on the physical interaction of receptors with both extracellular ligands and intracellular effectors, ligand binding must produce conformational changes in the receptor that can be transmitted to the intracellular domains accessible to G proteins and other effectors. Classical models of G protein-coupled receptor (GPCR) signaling envision receptor conformations as highly constrained, wherein receptors exist in equilibrium between single "off" and "on" states distinguished by their ability to activate effectors, and ligands act by perturbing this equilibrium. In such models, ligands can be classified based upon two simple parameters; affinity and efficacy, and ligand activity is independent of the assay used to detect the response. However, it is clear that GPCRs assume multiple conformations, any number of which may be capable of interacting with a discrete subset of possible effectors. Both orthosteric ligands, molecules that occupy the natural ligand-binding pocket, and allosteric modulators, small molecules or proteins that contact receptors distant from the site of ligand binding, have the ability to alter the conformational equilibrium of a receptor in ways that affect its signaling output both qualitatively and quantitatively. In this context, efficacy becomes pluridimensional and ligand classification becomes assay dependent. A more complete description of ligand-receptor interaction requires the use of multiplexed assays of receptor activation and screening assays may need to be tailored to detect specific efficacy profiles.
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Sf9 cells: a versatile model system to investigate the pharmacological properties of G protein-coupled receptors. Pharmacol Ther 2010; 128:387-418. [PMID: 20705094 DOI: 10.1016/j.pharmthera.2010.07.005] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2010] [Accepted: 07/12/2010] [Indexed: 11/23/2022]
Abstract
The Sf9 cell/baculovirus expression system is widely used for high-level protein expression, often with the purpose of purification. However, proteins may also be functionally expressed in the defined Sf9 cell environment. According to the literature, the pharmacology of G-protein-coupled receptors (GPCRs) functionally reconstituted in Sf9 cells is similar to the receptor properties in mammalian cells. Sf9 cells express both recombinant GPCRs and G-proteins at much higher levels than mammalian cells. Sf9 cells can be grown in suspension culture, providing an inexpensive way of obtaining large protein amounts. Co-infection with various baculoviruses allows free combination of GPCRs with different G-proteins. The absence of constitutively active receptors in Sf9 cells provides an excellent signal-to background ratio in functional assays, allowing the detection of agonist-independent receptor activity and of small ligand-induced signals including partial agonistic and inverse agonistic effects. Insect cell Gα(i)-like proteins mostly do not couple productively to mammalian GPCRs. Thus, unlike in mammalian cells, Sf9 cells do not require pertussis toxin treatment to obtain a Gα(i)-free environment. Co-expression of GPCRs with Gα(i1), Gα(i2), Gα(i3) or Gα(o) in Sf9 cells allows the generation of a selectivity profile for these Gα(i/o)-isoforms. Additionally, GPCR-G-protein combinations can be compared with defined 1:1 stoichiometry by expressing GPCR-Gα fusion proteins. Sf9 cells can also be employed for ligand screening in medicinal chemistry programs, using radioligand binding assays or functional assays, like the steady-state GTPase- or [(35)S]GTPγS binding assay. This review shows that Sf9 cells are a versatile model system to investigate the pharmacological properties of GPCRs.
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Geiger S, Nickl K, Schneider EH, Seifert R, Heilmann J. Establishment of recombinant cannabinoid receptor assays and characterization of several natural and synthetic ligands. Naunyn Schmiedebergs Arch Pharmacol 2010; 382:177-91. [PMID: 20617431 DOI: 10.1007/s00210-010-0534-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2009] [Accepted: 06/21/2010] [Indexed: 11/24/2022]
Abstract
Cannabinoid receptors (CBR) are important drug targets for the treatment of various inflammatory, metabolic and neurological diseases. Therefore, sensitive test systems for the assessment of ligands are needed. In this study, a steady-state GTPase assay for human CBR subtypes 1 and 2 was developed to characterize the pharmacological property of ligands at a very proximal point of the signal transduction cascade. Establishing these in vitro test sytems, we studied cell or tissue membranes heterogenously or endogenously expressing CBR, such as CBR-infected Human Embryonic Kidney (HEK) 293 cells, rat cerebellum and spleen cells. The lack of effects in the GTPase assay and in [(35)S]GTPgammaS binding experiments in these expression system, directed us to use Spodoptera frugiperda (Sf9) cells. Co-expressing CBR, different Galpha-subunits, Gbetagamma heterodimer, and RGS (Regulator of G-protein signaling)-proteins in Sf9 cell membranes greatly improved the sensitivity of the assay, with highest GTPase activation in the CBR + Galpha(i2) + Gbeta(1)gamma(2) + RGS4 system. We examined exogenous and endogenous standard ligands as well as secondary metabolites as Delta(9)-tetrahydrocannabinol (Delta(9)-THC), dodeca-2E,4E-dienoic acid isobutylamide, an alkylamide from Echinacea purpurea, and an E. purpurea hexane extract according their agonistic and antagonistic properties. The suitability of the assay for screening procedures was also proven by detecting the activity of Delta(9)-THC in a matrix of other less active compounds (Delta(9)-THC-free Cannabis sativa extract). In conclusion, we have developed highly sensitive test systems for the analysis of CBR ligands.
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Affiliation(s)
- Sarah Geiger
- Department of Pharmaceutical Biology, Institute of Pharmacy, University of Regensburg, 93053, Regensburg, Germany
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29
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Kenakin T. Allosteric theory: taking therapeutic advantage of the malleable nature of GPCRs. Curr Neuropharmacol 2010; 5:149-56. [PMID: 19305797 PMCID: PMC2656818 DOI: 10.2174/157015907781695973] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2006] [Accepted: 04/05/2007] [Indexed: 12/02/2022] Open
Abstract
The description of the allosteric modification of receptors to affect changes in their function requires a model that considers the effects of the modulator on both agonist affinity and efficacy. A model is presented which describes changes in affinity in terms of the constant α (ratio of affinity in the presence vs the absence of modulator) and also the constant ξ (ratio of intrinsic efficacy of the agonist in the presence vs absence of modulator). This allows independent effects of both affinity and efficacy and allows the modeling of any change in the dose-response curve to an agonist after treatment with modulator. Examples are given where this type of model can predict effects of modulators that reduce efficacy but actually increase affinity of agonist (i.e. ifenprodil) and also of modulators that block the action of some agonists (the CXCR4 agonist SDF-1α by the antagonist AMD3100) but not others for the same receptor (SDF-1α peptide fragments RSVM and ASLW). ‘All models are wrong…but some are useful…’ anonymous environmental scientist
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Affiliation(s)
- Terry Kenakin
- Dept. of Biological Reagents and Assay Develpoment, GlaxoSmithKline Research and Development, 5 Moore Drive, Research Triangle Park, NC 27709, USA.
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Schneider EH, Strasser A, Thurmond RL, Seifert R. Structural Requirements for Inverse Agonism and Neutral Antagonism of Indole-, Benzimidazole-, and Thienopyrrole-Derived Histamine H4 Receptor Ligands. J Pharmacol Exp Ther 2010; 334:513-21. [DOI: 10.1124/jpet.110.165977] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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31
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Kenakin T, Miller LJ. Seven transmembrane receptors as shapeshifting proteins: the impact of allosteric modulation and functional selectivity on new drug discovery. Pharmacol Rev 2010; 62:265-304. [PMID: 20392808 DOI: 10.1124/pr.108.000992] [Citation(s) in RCA: 458] [Impact Index Per Article: 32.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
It is useful to consider seven transmembrane receptors (7TMRs) as disordered proteins able to allosterically respond to a number of binding partners. Considering 7TMRs as allosteric systems, affinity and efficacy can be thought of in terms of energy flow between a modulator, conduit (the receptor protein), and a number of guests. These guests can be other molecules, receptors, membrane-bound proteins, or signaling proteins in the cytosol. These vectorial flows of energy can yield standard canonical guest allostery (allosteric modification of drug effect), effects along the plane of the cell membrane (receptor oligomerization), or effects directed into the cytosol (differential signaling as functional selectivity). This review discusses these apparently diverse pharmacological effects in terms of molecular dynamics and protein ensemble theory, which tends to unify 7TMR behavior toward cells. Special consideration will be given to functional selectivity (biased agonism and biased antagonism) in terms of mechanism of action and potential therapeutic application. The explosion of technology that has enabled observation of diverse 7TMR behavior has also shown how drugs can have multiple (pluridimensional) efficacies and how this can cause paradoxical drug classification and nomenclatures.
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Affiliation(s)
- Terry Kenakin
- GlaxoSmithKline, 5 Moore Drive, Mailtstop V-287, Research Triangle Park, NC 27709, USA.
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Schnell D, Burleigh K, Trick J, Seifert R. No Evidence for Functional Selectivity of Proxyfan at the Human Histamine H3 Receptor Coupled to Defined Gi/Go Protein Heterotrimers. J Pharmacol Exp Ther 2009; 332:996-1005. [DOI: 10.1124/jpet.109.162339] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Suryanarayana S, Göttle M, Hübner M, Gille A, Mou TC, Sprang SR, Richter M, Seifert R. Differential inhibition of various adenylyl cyclase isoforms and soluble guanylyl cyclase by 2',3'-O-(2,4,6-trinitrophenyl)-substituted nucleoside 5'-triphosphates. J Pharmacol Exp Ther 2009; 330:687-95. [PMID: 19494187 PMCID: PMC2729792 DOI: 10.1124/jpet.109.155432] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2009] [Accepted: 06/02/2009] [Indexed: 11/22/2022] Open
Abstract
Adenylyl cyclases (ACs) catalyze the conversion of ATP into the second messenger cAMP and play a key role in signal transduction. In a recent study (Mol Pharmacol 70:878-886, 2006), we reported that 2',3'-O-(2,4,6-trinitrophenyl)-substituted nucleoside 5'-triphosphates (TNP-NTPs) are potent inhibitors (K(i) values in the 10 nM range) of the purified catalytic subunits VC1 and IIC2 of membranous AC (mAC). The crystal structure of VC1:IIC2 in complex with TNP-ATP revealed that the nucleotide binds to the catalytic site with the TNP-group projecting into a hydrophobic pocket. The aims of this study were to analyze the interaction of TNP-nucleotides with VC1:IIC2 by fluorescence spectroscopy and to analyze inhibition of mAC isoforms, soluble AC (sAC), soluble guanylyl cyclase (sGC), and G-proteins by TNP-nucleotides. Interaction of VC1:IIC2 with TNP-NDPs and TNP-NTPs resulted in large fluorescence increases that were differentially reduced by a water-soluble forskolin analog. TNP-ATP turned out to be the most potent inhibitor for ACV (K(i), 3.7 nM) and sGC (K(i), 7.3 nM). TNP-UTP was identified as the most potent inhibitor for ACI (K(i), 7.1 nM) and ACII (K(i), 24 nM). TNP-NTPs inhibited sAC and GTP hydrolysis by G(s)- and G(i)-proteins only with low potencies. Molecular modeling revealed that TNP-GTP and TNP-ATP interact very similarly, but not identically, with VC1:IIC2. Collectively, our data show that TNP-nucleotides are useful fluorescent probes to monitor conformational changes in VC1:IIC2 and that TNP-NTPs are a promising starting point to develop isoform-selective AC and sGC inhibitors. TNP-ATP is the most potent sGC inhibitor known so far.
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Schneider EH, Schnell D, Papa D, Seifert R. High constitutive activity and a G-protein-independent high-affinity state of the human histamine H(4)-receptor. Biochemistry 2009; 48:1424-38. [PMID: 19166345 DOI: 10.1021/bi802050d] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The human histamine H(4)-receptor (hH(4)R) is expressed in mast cells and eosinophils and mediates histamine (HA)-induced chemotaxis via G(i)-proteins. For a detailed investigation of hH(4)R/G(i)-protein interaction, we coexpressed the hH(4)R with Galpha(i2) and Gbeta(1)gamma(2) as well as an hH(4)R-Galpha(i2) fusion protein with Gbeta(1)gamma(2) in Sf9 insect cells. The agonist radioligand [(3)H]HA showed a K(D) value of approximately 10 nM at hH(4)R and hH(4)R-Galpha(i2). The high-affinity states of hH(4)R and hH(4)R-Galpha(i2) were insensitive to guanosine 5'-[gamma-thio]triphosphate (GTPgammaS). The affinity of [(3)H]HA for hH(4)R was retained in the absence of mammalian G(i)-proteins. In steady-state GTPase- and [(35)S]GTPgammaS-binding assays, hH(4)R exhibited high constitutive activity and uncommon insensitivity to Na(+). Thioperamide (THIO) was only a partial inverse agonist. Addition of HA or THIO to baculovirus-infected (hH(4)R + Galpha(i2) + Gbeta(1)gamma(2)) Sf9 cells increased the B(max) in [(3)H]HA binding, but not in immunoblots, suggesting conformational instability and ligand-induced stabilization of membrane-integrated hH(4)R. No effect was observed on hH(4)R-Galpha(i2) expression, neither in [(3)H]HA binding nor in immunoblot. However, the expression level of hH(4)R-Galpha(i2) was consistently higher compared to hH(4)R, suggesting chaperone-like or stabilizing effects of Galpha(i2) on hH(4)R. In 37 degrees C stability assays, HA stabilized hH(4)R, and THIO even restored misfolded [(3)H]HA binding sites. Inhibition of hH(4)R glycosylation by tunicamycin reduced the [(3)H]HA binding B(max) value. In conclusion, (i) hH(4)R shows high constitutive activity and structural instability; (ii) hH(4)R shows a G-protein-independent high-affinity state; (iii) hH(4)R conformation is stabilized by agonists, inverse agonists and G-proteins; (iv) hH(4)R glycosylation is essential for cell-surface expression of intact hH(4)R.
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Affiliation(s)
- Erich H Schneider
- Department of Pharmacology and Toxicology, University of Regensburg, Universitatsstrasse 31, D-93040 Regensburg, Germany.
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Igel P, Schnell D, Bernhardt G, Seifert R, Buschauer A. Tritium-LabeledN1-[3-(1H-imidazol-4-yl)propyl]-N2-propionylguanidine ([3H]UR-PI294), a High-Affinity Histamine H3and H4Receptor Radioligand. ChemMedChem 2009; 4:225-31. [DOI: 10.1002/cmdc.200800349] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Hein P, Bünemann M. Coupling mode of receptors and G proteins. Naunyn Schmiedebergs Arch Pharmacol 2008; 379:435-43. [PMID: 19048232 DOI: 10.1007/s00210-008-0383-7] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2008] [Accepted: 11/16/2008] [Indexed: 10/21/2022]
Abstract
Signaling via G-protein-coupled receptors (GPCRs) is crucial to many physiological and pathophysiological processes in multicellular organisms, and GPCRs themselves are targets for important drugs. Classical cell supplementation experiments suggest a collision coupling model, in which receptors and G proteins diffuse randomly within the cell membrane and interact only if receptors are activated. This model is also backed by kinetic and live cell imaging data. According to the challenging theory, receptors and G proteins are precoupled--meaning they are forming stable complexes in the absence of agonist, which prevail during signaling. This model has been favored on the basis of copurification and coimmunoprecipitation of inactive receptors with G proteins and more recently by some approaches measuring energy transfer between labeled receptors and G proteins. This article reviews key findings regarding the receptor/G protein coupling mode, including most recent findings obtained by optical techniques.
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Affiliation(s)
- Peter Hein
- Department of Psychiatry, University of California at San Francisco, 600 16th St, UCSF MC 2140, Genentech Hall N216P, San Francisco, CA 94158-2517, USA.
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Seifert R, Dove S. Functional selectivity of GPCR ligand stereoisomers: new pharmacological opportunities. Mol Pharmacol 2008; 75:13-8. [PMID: 19001067 DOI: 10.1124/mol.108.052944] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
It is now well established that any given ligand for a G-protein-couple receptor (GPCR) does not simply possess a single defined efficacy. Rather, a ligand possesses multiple efficacies, depending on the specific down-stream signal transduction pathway analyzed. This diversity may be based on ligand-specific GPCR conformations and is often referred to as "functional selectivity." It has been known for a century that stereoisomers of catecholamines differ in their potency and, in some systems, also in their efficacy. However, the molecular basis for efficacy differences of GPCR ligand stereoisomers has remained poorly defined. In an elegant study published in this issue of Molecular Pharmacology, Woo et al. (p. 158) show that stereoisomers of the beta(2)-adrenoceptor selective agonist fenoterol differentially activates G(s)- and G(i)-proteins in native rat cardiomyocytes. This study is so important because it is the first report to show that even the subtle structural differences within a ligand stereoisomer pair are sufficient to discriminate between GPCR conformations with distinct G-protein coupling properties. The study highlights of how important it is to examine the "more active" (eutomer) and the "less active" (distomer) stereoisomer to understand the mechanisms of action and the cellular effects of GPCR ligands. The study by Woo et al. will ignite a renaissance of the analysis of ligand stereoisomers, using sensitive pharmacological and biophysical assays. The available literature supports the notion that meticulous analysis of ligand stereoisomers is a goldmine for understanding mechanisms of GPCR activation, analysis of signal transduction pathways, development of new therapies for important diseases, and drug safety.
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Affiliation(s)
- Roland Seifert
- Department of Pharmacology, Medical School of Hannover, Carl-Neuberg-Strasse 1, D-30625 Hannover, Germany.
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38
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Nickl K, Gardner EE, Geiger S, Heilmann J, Seifert R. Differential coupling of the human cannabinoid receptors hCB1R and hCB2R to the G-protein G(alpha)i2beta1gamma2. Neurosci Lett 2008; 447:68-72. [PMID: 18845226 DOI: 10.1016/j.neulet.2008.09.078] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2008] [Revised: 09/20/2008] [Accepted: 09/27/2008] [Indexed: 10/21/2022]
Abstract
Human cannabinoid receptors 1 (hCB(1)R) and 2 (hCB(2)R) are expressed in the CNS and couple to G(i)/G(o)-proteins. The aim of this study was to compare coupling of hCB(1)R and hCB(2)R to G(alpha)(i2)beta(1)gamma(2) in Sf9 insect cells. High-affinity agonist binding at hCB(1)R, but not at hCB(2)R, was resistant to guanine nucleotides. hCB(1)R activated G(alpha)(i2)beta(1)gamma(2) much more rapidly than hCB(2)R in the [(35)S]guanosine 5'-[gamma-thio]triphosphate ([(35)S]GTPgammaS) binding assay. Moreover, hCB(1)R exhibited a higher constitutive activity than hCB(2)R as assessed by the relative inhibitory effects of inverse agonists on [(35)S]GTPgammaS binding and steady-state high-affinity GTPase activity compared to the stimulatory effects of the hCB(1/2)R agonist CP 55,940 [(-)-cis-3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-trans-4-(3-hydroxypropyl)cyclohexanol]. G(alpha)(i2)beta(1)gamma(2) coupled to hCB(2)R exhibited higher GDP- and GTPgammaS-affinities than G(alpha)(i2)beta(1)gamma(2) coupled to hCB(1)R. NaCl effectively reduced constitutive activity of hCB(1)R but not of hCB(2)R. Collectively, hCB(1)R and hCB(2)R couple differentially to G(alpha)(i2)beta(1)gamma(2). Moreover, hCB(1)R exhibits higher constitutive activity than hCB(2)R. These differences point to distinct functions of hCB(1)R and hCB(2)R in the CNS.
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Affiliation(s)
- Kathrin Nickl
- Department of Pharmaceutical Biology, University of Regensburg, Regensburg, Germany
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Weitl N, Seifert R. Distinct interactions of human beta1- and beta2-adrenoceptors with isoproterenol, epinephrine, norepinephrine, and dopamine. J Pharmacol Exp Ther 2008; 327:760-9. [PMID: 18772317 DOI: 10.1124/jpet.108.143412] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Fluorescence studies with purified human beta(2)-adrenoceptor (beta(2)AR) revealed that the endogenous catecholamines, (-)-epinephrine (EPI), (-)-norepinephrine (NE), and dopamine (DOP), stabilize distinct active receptor conformations. However, the functional relevance of these ligand-specific conformations is as yet poorly understood. We addressed this question by studying fusion proteins of the beta(1)-adrenoceptor (beta(1)AR) and beta(2)AR with the short and long splice variants of G(s)alpha (G(s)alpha(S) and G(s)alpha(L)), respectively. Fusion proteins ensure efficient receptor/G-protein coupling and defined stoichiometry of the coupling partners. EPI, NE, DOP, and the prototypical synthetic betaAR agonist, (-)-isoproterenol (ISO), showed marked differences in their efficacies at stabilizing the high-affinity ternary complex at beta(1)AR-G(s)alpha and beta(2)AR-G(s)alpha fusion proteins. Ternary complex formation was more sensitive to disruption by GTP with the beta(2)AR than with the beta(1)AR. Generally, in steady-state GTPase assays, ISO, EPI, and NE were full agonists, and DOP was a partial agonist. Exceptionally, at beta(1)AR-G(s)alpha(L), NE was only a partial agonist. Generally, in adenylyl cyclase assays, ISO, EPI, and NE were full agonists, and DOP was a partial agonist. At beta(2)AR-G(s)alpha(L), NE was only a partial agonist. There was no correlation between efficacy at stabilizing the ternary complex and activating GTPase, and there were also dissociations between K(i) values for high-affinity agonist binding and EC(50) values for GTPase activation. In contrast to synthetic partial agonists, DOP did not exhibit increased efficacy at betaAR-G(s)alpha(L) versus betaAR-G(s)alpha(S) fusion proteins. In conclusion, our data with betaAR-G(s)alpha fusion proteins show that endogenous catecholamines and ISO stabilize distinct conformations in the beta(1)AR and beta(2)AR.
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Affiliation(s)
- Nina Weitl
- Department of Pharmacology and Toxicology, School of Pharmacy, University of Regensburg, Regensburg, Germany
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Gesty-Palmer D, Luttrell LM. Heptahelical terpsichory. Who calls the tune? J Recept Signal Transduct Res 2008; 28:39-58. [PMID: 18437629 DOI: 10.1080/10799890801941921] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The discovery that arrestins can function as ligand-regulated signaling scaffolds has revealed a previously unappreciated level of complexity in G protein-coupled receptor (GPCR) signal transduction. Because arrestin-bound GPCRs are uncoupled from G proteins, arrestin binding can be viewed as switching receptors between two temporally and spatially distinct signaling modes. Recent work has established two factors that underscore this duality of GPCR signaling and suggest it may ultimately have therapeutic significance. The first is that signaling by receptor-arrestin "signalsomes" does not require heterotrimeric G protein activation. The second is that arrestin-dependent signals can be initiated by pathway-specific "biased agonists," creating the potential for drugs that selectively modulate different aspects of GPCR function. Currently, however, little is known about the physiological relevance of G protein-independent signals at the cellular or whole animal levels, and additional work is needed to determine whether arrestin pathway-selective drugs will find clinical application.
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Affiliation(s)
- Diane Gesty-Palmer
- Department of Medicine Duke University Medical Center, Durham, North Carolina, USA
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Arch JRS. The discovery of drugs for obesity, the metabolic effects of leptin and variable receptor pharmacology: perspectives from beta3-adrenoceptor agonists. Naunyn Schmiedebergs Arch Pharmacol 2008; 378:225-40. [PMID: 18612674 DOI: 10.1007/s00210-008-0271-1] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2008] [Accepted: 02/05/2008] [Indexed: 12/12/2022]
Abstract
Although beta3-adrenoceptor (beta3AR) agonists have not become drugs for the treatment of obesity or diabetes, they offer perspectives on obesity drug discovery, the physiology of energy expenditure and receptor pharmacology. beta3AR agonists, some of which also stimulate other betaARs in humans, selectively stimulate fat oxidation in rodents and humans. This appears to be why they improve insulin sensitivity and reduce body fat whilst preserving lean body mass. Regulatory authorities ask that novel anti-obesity drugs improve insulin sensitivity and reduce mainly body fat. Drugs that act on different targets to stimulate fat oxidation may also offer these benefits. Stimulation of energy expenditure may be easy to detect only when the sympathetic nervous system is activated. Leptin resembles beta3AR agonists in that it increases fat oxidation, energy expenditure and insulin sensitivity. This is partly because it raises sympathetic activity, but it may also promote fat oxidation by directly stimulating muscle leptin receptors. The beta1AR and beta2AR can, like the beta3AR, display atypical pharmacologies. Moreover, the beta3AR can display variable pharmacologies of its own, depending on the radioligand used in binding studies or the functional response measured. Studies on the beta3AR demonstrate both the difficulties of predicting the in vivo effects of agonist drugs from in vitro data and that there may be opportunities for identifying drugs that act at a single receptor but have different profiles in vivo.
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Affiliation(s)
- Jonathan R S Arch
- Clore Laboratory, University of Buckingham, Buckingham, MK18 1EG, UK.
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Sheffler DJ, Conn PJ. Allosteric potentiators of metabotropic glutamate receptor subtype 1a differentially modulate independent signaling pathways in baby hamster kidney cells. Neuropharmacology 2008; 55:419-27. [PMID: 18625258 DOI: 10.1016/j.neuropharm.2008.06.047] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2008] [Revised: 06/24/2008] [Accepted: 06/24/2008] [Indexed: 10/21/2022]
Abstract
Recent studies suggest that subtype specific activators of metabotropic glutamate receptors (mGluRs) have exciting potential for the development of novel treatment strategies for numerous psychiatric and neurological disorders. A number of positive allosteric modulators (PAMs) have been identified that are highly selective for mGluR1, including the compounds Ro 01-6128, Ro 67-4853, and Ro 67-7476. These PAMs have been previously found to interact with a site distinct from that of negative allosteric modulators (NAMs), typified by R214127. These mGluR1 PAMs do not have an effect on baseline calcium levels but induce leftward shifts in the concentration-response of mGluR1 to agonists. However, their effects on a variety of signaling pathways and their mechanism of action have not been fully explored and are of critical importance for further development of mGluR1 allosteric modulators as novel drugs. In baby hamster kidney (BHK) cells, mGluR1 activates calcium mobilization, cAMP production, and extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation; signaling cascades which are distinct and differentially regulated. In contrast to their effects on calcium mobilization, these compounds were found to activate ERK1/2 phosphorylation in the absence of exogenously added agonist, an effect that was fully blocked by both orthosteric (LY341495) and allosteric (R214127) mGluR1 antagonists. The mGluR1 PAMs were also found to activate cAMP production in the absence of agonist. Thus, these mGluR1 PAMs have qualitatively different effects on a variety of mGluR1-mediated signal transduction cascades. Together, these data provide further evidence that allosteric compounds can differentially modulate the coupling of a single receptor to independent signaling pathways or act in a system-dependent manner.
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Affiliation(s)
- Douglas J Sheffler
- Department of Pharmacology, Vanderbilt Program in Drug Discovery, Vanderbilt University Medical Center, Nashville, TN 37232, United States
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43
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Reviews in Molecular Biology and Biotechnology: Transmembrane Signaling by G Protein-Coupled Receptors. Mol Biotechnol 2008; 39:239-64. [DOI: 10.1007/s12033-008-9031-1] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2008] [Accepted: 01/07/2008] [Indexed: 01/14/2023]
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Geisbuhler TP. Compartmentalization of non-adenine nucleotides in anoxic cardiac myocytes. Basic Res Cardiol 2007; 103:31-40. [PMID: 17891521 DOI: 10.1007/s00395-007-0678-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2007] [Accepted: 08/29/2007] [Indexed: 11/29/2022]
Abstract
Loss of 5'-nucleotides from cardiac myocytes is a distinguishing feature of myocardial ischemia. Previous work has documented dislocations of metabolic processes mediated by both purine and pyrimidine nucleotides, especially the adenine nucleotides. This study was designed to establish the extent of anoxia-induced depletion of non-adenine nucleotides in the cytosolic compartment of heart muscle cells. Cardiac myocytes were incubated aerobically (O(2)) or anoxically (N(2)) for 30 or 60 min; anoxic cells at both time points were reoxygenated for 10 min. Roughly 85-90% of cytosine triphosphate (CTP) and uridine triphosphate (UTP) were cytosolic under aerobic conditions, compared with 62% of guanosine triphosphate (GTP) and 90% of adenosine triphosphate (ATP) under similar conditions. Similarly, the total cytidine and uridine nucleotide pool of aerobic myocytes was 70-90% cytosolic vs. 61% of total guanine nucleotides and 78% of total adenine nucleotides. After the onset of anoxia, cytosolic nucleotides (principally the triphosphate forms) were quickly degraded. Reoxygenation of anoxic myocytes for 10 min allowed some recovery of ATP, GTP, and CTP, but very little recovery of UTP. The recovered nucleotide appeared almost exclusively in the cytosol. These results support the concept that non-adenine nucleotides could reach critically low levels in anoxic or ischemic heart in advance of adenine nucleotides. The importance of the depletion of non-adenine nucleotides is discussed in terms of the energetic needs of the myocyte, and the need for the cell to drive G-protein-coupled reactions, lipid synthesis, and glycogenesis.
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Affiliation(s)
- Timothy P Geisbuhler
- Department of Physiology, A.T. Still University, 800 West Jefferson Street, Kirksville, MO 63501, USA.
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Russo O, Berthouze M, Giner M, Soulier JL, Rivail L, Sicsic S, Lezoualc'h F, Jockers R, Berque-Bestel I. Synthesis of specific bivalent probes that functionally interact with 5-HT(4) receptor dimers. J Med Chem 2007; 50:4482-92. [PMID: 17676726 DOI: 10.1021/jm070552t] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
G-protein-coupled receptor dimerization directs the design of new drugs that specifically bind to receptor dimers. Here, we generated a targeted series of homobivalent ligands for serotonin 5-HT(4) receptor (5-HT(4)R) dimers composed of two 5-HT(4)R-specific ML10302 units linked by a spacer. The design of spacers was assisted by molecular modeling using our previously described 5-HT(4)R dimer model. Their syntheses were based on Sonogashira-Linstrumelle coupling methods. All compounds retained high-affinity binding to 5-HT(4)R but lost the agonistic character of the monomeric ML10302 compound. Direct evidence for the functional interaction of both pharmacophores of bivalent ligands with the 5-HT(4)R was obtained using a bioluminescence resonance energy transfer (BRET) based assay that monitors conformational changes within 5-HT(4) dimers. Whereas the monovalent ML10302 was inactive in this assay, several bivalent derivatives dose-dependently increased the BRET signal, indicating that both pharmacophores functionally interact with the 5-HT(4) dimer. These bivalent ligands may serve as a new basis for the synthesis of potential drugs for 5-HT(4)-associated disorders.
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Affiliation(s)
- Olivier Russo
- Université Paris-Sud, Faculté de Pharmacie, IFR141, UMR-S769, Châtenay-Malabry, F-92296, Inserm, U567, France
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Suga H, Haga T. Ligand screening system using fusion proteins of G protein-coupled receptors with G protein alpha subunits. Neurochem Int 2007; 51:140-64. [PMID: 17659814 DOI: 10.1016/j.neuint.2007.06.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2007] [Revised: 06/07/2007] [Accepted: 06/08/2007] [Indexed: 01/04/2023]
Abstract
G protein-coupled receptors (GPCRs) constitute one of the largest families of genes in the human genome, and are the largest targets for drug development. Although a large number of GPCR genes have recently been identified, ligands have not yet been identified for many of them. Various assay systems have been employed to identify ligands for orphan GPCRs, but there is still no simple and general method to screen for ligands of such GPCRs, particularly of G(i)-coupled receptors. We have examined whether fusion proteins of GPCRs with G protein alpha subunit (Galpha) could be utilized for ligand screening and showed that the fusion proteins provide an effective method for the purpose. This article focuses on the followings: (1) characterization of GPCR genes and GPCRs, (2) identification of ligands for orphan GPCRs, (3) characterization of GPCR-Galpha fusion proteins, and (4) identification of ligands for orphan GPCRs using GPCR-Galpha fusion proteins.
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Affiliation(s)
- Hinako Suga
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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Kenakin T. Collateral efficacy as a pharmacological problem applied to new drug discovery. Expert Opin Drug Discov 2006; 1:635-52. [DOI: 10.1517/17460441.1.7.635] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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48
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Brown SL, Jala VR, Raghuwanshi SK, Nasser MW, Haribabu B, Richardson RM. Activation and regulation of platelet-activating factor receptor: role of G(i) and G(q) in receptor-mediated chemotactic, cytotoxic, and cross-regulatory signals. THE JOURNAL OF IMMUNOLOGY 2006; 177:3242-9. [PMID: 16920964 DOI: 10.4049/jimmunol.177.5.3242] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Platelet-activating factor (1-O-alkyl-2-acetyl-sn-glycerolphosphocholine; PAF) induces leukocyte accumulation and activation at sites of inflammation via the activation of a specific cell surface receptor (PAFR). PAFR couples to both pertussis toxin-sensitive and pertussis toxin-insensitive G proteins to activate leukocytes. To define the role(s) of G(i) and G(q) in PAF-induced leukocyte responses, two G-protein-linked receptors were generated by fusing G alpha(i3) (PAFR-G alpha(i3)) or G alpha(q) (PAFR-G alpha(q)) at the C terminus of PAFR. Rat basophilic leukemia cell line (RBL-2H3) stably expressing wild-type PAFR, PAFR-G alpha(i3), or PAFR-G alpha(q) was generated and characterized. All receptor variants bound PAF with similar affinities to mediate G-protein activation, intracellular Ca2+ mobilization, phosphoinositide (PI) hydrolysis, and secretion of beta-hexosaminidase. PAFR-G alpha(i3) and PAFR-G alpha(q) mediated greater GTPase activity in isolated membranes than PAFR but lower PI hydrolysis and secretion in whole cells. PAFR and PAFR-G alpha(i3), but not PAFR-G alpha(q), mediated chemotaxis to PAF. All three receptors underwent phosphorylation and desensitization upon exposure to PAF but only PAFR translocated beta arrestin to the cell membrane and internalized. In RBL-2H3 cells coexpressing the PAFRs along with CXCR1, IL-8 (CXCL8) cross-desensitized Ca2+ mobilization to PAF by all the receptors but only PAFR-G alpha(i3) activation cross-inhibited the response of CXCR1 to CXCL8. Altogether, the data indicate that G(i) exclusively mediates chemotactic and cross-regulatory signals of the PAFR, but both G(i) and G(q) activate PI hydrolysis and exocytosis by this receptor. Because chemotaxis and cross-desensitization are exclusively mediated by G(i), the data suggest that differential activation of both G(i) and G(q) by PAFR likely mediate specific as well as redundant signaling pathways.
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Affiliation(s)
- Stephan L Brown
- Department of Biochemistry, Meharry Medical College, Nashville, TN 37208, USA
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Nikolaev VO, Hoffmann C, Bünemann M, Lohse MJ, Vilardaga JP. Molecular basis of partial agonism at the neurotransmitter alpha2A-adrenergic receptor and Gi-protein heterotrimer. J Biol Chem 2006; 281:24506-11. [PMID: 16787921 DOI: 10.1074/jbc.m603266200] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
To characterize the mechanism by which heterotrimeric G-proteins interpret the signals coming from various neurotransmitters of diverse efficacies (agonists and partial agonists) acting on alpha(2A)-adrenergic receptors, we used a fluorescent resonance energy transfer-based approach to study the effects of these partial agonists on the activation process of both the alpha(2A)-adrenergic receptor and its cognate G(i)-protein. We show that ligands of different efficacies switch the receptor into distinct conformational states, which in turn set the speed and extent of the G(i)-protein signaling. Thus, in cells the efficacy by which a receptor responds to diverse ligands is caused by the ability of the G-protein to differentiate between distinct receptor conformations. The data provide a new key characteristic underlying the mechanism of partial agonism at G-protein-coupled receptors.
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Affiliation(s)
- Viacheslav O Nikolaev
- Institute of Pharmacology and Toxicology, University of Würzburg, D-97078, Würzburg, Germany
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Xie SX, Ghorai P, Ye QZ, Buschauer A, Seifert R. Probing Ligand-Specific Histamine H1- and H2-Receptor Conformations withNG-Acylated Imidazolylpropylguanidines. J Pharmacol Exp Ther 2006; 317:139-46. [PMID: 16394198 DOI: 10.1124/jpet.105.097923] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Impromidine (IMP) and arpromidine (ARP)-derived guanidines are more potent and efficacious guinea pig (gp) histamine H(2)-receptor (gpH(2)R) than human (h) H(2)R agonists and histamine H(1)-receptor (H(1)R) antagonists with preference for hH(1)R relative to gpH(1)R. We examined N(G)-acylated imidazolylpropylguanidines (AIPGs), which are less basic than guanidines, at hH(2)R, gpH(2)R, rat H(2)R (rH(2)R), hH(1)R, and gpH(1)R expressed in Sf9 cells as probes for ligand-specific receptor conformations. AIPGs were similarly potent H(2)R agonists as the corresponding guanidines IMP and ARP, respectively. Exchange of pyridyl in ARP against phenyl increased AIPG potency 10-fold, yielding the most potent agonists at the hH(2)R-G(salpha) fusion protein and gpH(2)R-G(salpha) identified so far. Some AIPGs were similarly potent and efficacious at hH(2)R-G(salpha) and gpH(2)R-G(salpha). AIPGs stabilized the ternary complex in hH(2)R-G(salpha) and gpH(2)R-G(salpha) differently than the corresponding guanidines. Guanidines, AIPGs, and small H(2)R agonists exhibited distinct agonist properties at hH(2)R, gpH(2)R, and rH(2)R measuring adenylyl cyclase activity. In contrast to ARP and IMP, AIPGs were partial H(1)R agonists exhibiting higher efficacies at hH(1)R than at gpH(1)R. This is remarkable because, so far, all bulky H(1)R agonists exhibited higher efficacies at gpH(1)R than at hH(1)R. Collectively, our data suggest that AIPGs stabilize different active conformations in hH(2)R, gpH(2)R, and rH(2)R than guanidines and that, in contrast to guanidines, AIPGs are capable of stabilizing a partially active state of hH(1)R.
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Affiliation(s)
- Sheng-Xue Xie
- High Throughput Screening Laboratory, The University of Kansas, Lawrence, USA
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