1
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Rodríguez FD, Sánchez ML, Coveñas R. Neurotensin and Alcohol Use Disorders: Towards a Pharmacological Treatment. Int J Mol Sci 2023; 24:ijms24108656. [PMID: 37240004 DOI: 10.3390/ijms24108656] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Revised: 05/06/2023] [Accepted: 05/10/2023] [Indexed: 05/28/2023] Open
Abstract
Harmful alcohol use is responsible for a group of disorders collectively named alcohol use disorders (AUDs), according to the DSM-5 classification. The damage induced by alcohol depends on the amount, time, and consumption patterns (continuous and heavy episodic drinking). It affects individual global well-being and social and familial environments with variable impact. Alcohol addiction manifests with different degrees of organ and mental health detriment for the individual, exhibiting two main traits: compulsive drinking and negative emotional states occurring at withdrawal, frequently causing relapse episodes. Numerous individual and living conditions, including the concomitant use of other psychoactive substances, lie in the complexity of AUD. Ethanol and its metabolites directly impact the tissues and may cause local damage or alter the homeostasis of brain neurotransmission, immunity scaffolding, or cell repair biochemical pathways. Brain modulator and neurotransmitter-assembled neurocircuitries govern reward, reinforcement, social interaction, and consumption of alcohol behaviors in an intertwined manner. Experimental evidence supports the participation of neurotensin (NT) in preclinical models of alcohol addiction. For example, NT neurons in the central nucleus of the amygdala projecting to the parabrachial nucleus strengthen alcohol consumption and preference. In addition, the levels of NT in the frontal cortex were found to be lower in rats bred to prefer alcohol to water in a free alcohol-water choice compared to wild-type animals. NT receptors 1 and 2 seem to be involved in alcohol consumption and alcohol effects in several models of knockout mice. This review aims to present an updated picture of the role of NT systems in alcohol addiction and the possible use of nonpeptide ligands modulating the activity of the NT system, applied to experimental animal models of harmful drinking behavior mimicking alcohol addiction leading to health ruin in humans.
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Affiliation(s)
- Francisco D Rodríguez
- Department of Biochemistry and Molecular Biology, Faculty of Chemical Sciences, University of Salamanca, 37008 Salamanca, Spain
- Group GIR-USAL: BMD (Bases Moleculares del Desarrollo), University of Salamanca, 37008 Salamanca, Spain
| | - Manuel Lisardo Sánchez
- Laboratory of Neuroanatomy of the Peptidergic Systems, Institute of Neurosciences of Castilla and León (INCYL), University of Salamanca, C/Pintor Fernando Gallego 1, 37007 Salamanca, Spain
| | - Rafael Coveñas
- Group GIR-USAL: BMD (Bases Moleculares del Desarrollo), University of Salamanca, 37008 Salamanca, Spain
- Laboratory of Neuroanatomy of the Peptidergic Systems, Institute of Neurosciences of Castilla and León (INCYL), University of Salamanca, C/Pintor Fernando Gallego 1, 37007 Salamanca, Spain
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2
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Krumm BE, DiBerto JF, Olsen RHJ, Kang HJ, Slocum ST, Zhang S, Strachan RT, Huang XP, Slosky LM, Pinkerton AB, Barak LS, Caron MG, Kenakin T, Fay JF, Roth BL. Neurotensin Receptor Allosterism Revealed in Complex with a Biased Allosteric Modulator. Biochemistry 2023; 62:1233-1248. [PMID: 36917754 DOI: 10.1021/acs.biochem.3c00029] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/16/2023]
Abstract
The NTSR1 neurotensin receptor (NTSR1) is a G protein-coupled receptor (GPCR) found in the brain and peripheral tissues with neurotensin (NTS) being its endogenous peptide ligand. In the brain, NTS modulates dopamine neuronal activity, induces opioid-independent analgesia, and regulates food intake. Recent studies indicate that biasing NTSR1 toward β-arrestin signaling can attenuate the actions of psychostimulants and other drugs of abuse. Here, we provide the cryoEM structures of NTSR1 ternary complexes with heterotrimeric Gq and GoA with and without the brain-penetrant small-molecule SBI-553. In functional studies, we discovered that SBI-553 displays complex allosteric actions exemplified by negative allosteric modulation for G proteins that are Gα subunit selective and positive allosteric modulation and agonism for β-arrestin translocation at NTSR1. Detailed structural analysis of the allosteric binding site illuminated the structural determinants for biased allosteric modulation of SBI-553 on NTSR1.
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Affiliation(s)
- Brian E Krumm
- Department of Pharmacology, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina 27599-7365, United States
| | - Jeffrey F DiBerto
- Department of Pharmacology, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina 27599-7365, United States
| | - Reid H J Olsen
- Department of Pharmacology, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina 27599-7365, United States
| | - Hye Jin Kang
- Department of Pharmacology, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina 27599-7365, United States
- National Institute of Mental Health Psychoactive Drug Screening Program (NIMH PDSP), School of Medicine, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina 27599-7365, United States
| | - Samuel T Slocum
- Department of Pharmacology, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina 27599-7365, United States
- National Institute of Mental Health Psychoactive Drug Screening Program (NIMH PDSP), School of Medicine, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina 27599-7365, United States
| | - Shicheng Zhang
- Department of Pharmacology, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina 27599-7365, United States
| | - Ryan T Strachan
- Department of Pharmacology, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina 27599-7365, United States
| | - Xi-Ping Huang
- Department of Pharmacology, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina 27599-7365, United States
- National Institute of Mental Health Psychoactive Drug Screening Program (NIMH PDSP), School of Medicine, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina 27599-7365, United States
| | - Lauren M Slosky
- Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Anthony B Pinkerton
- Conrad Prebys Center for Chemical Genomics at Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California 92037, United States
| | - Lawrence S Barak
- Department of Cell Biology, Duke University, Durham, North Carolina 27710, United States
| | - Marc G Caron
- Department of Cell Biology, Duke University, Durham, North Carolina 27710, United States
- Departments of Medicine and Neurobiology, Duke University, Durham, North Carolina 27710, United States
| | - Terry Kenakin
- Department of Pharmacology, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina 27599-7365, United States
| | - Jonathan F Fay
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina 27599, United States
| | - Bryan L Roth
- Department of Pharmacology, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina 27599-7365, United States
- National Institute of Mental Health Psychoactive Drug Screening Program (NIMH PDSP), School of Medicine, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina 27599-7365, United States
- Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7360, United States
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3
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Ligands selectively tune the local and global motions of neurotensin receptor 1 (NTS 1). Cell Rep 2023; 42:112015. [PMID: 36680775 PMCID: PMC9930568 DOI: 10.1016/j.celrep.2023.112015] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Revised: 11/05/2022] [Accepted: 01/05/2023] [Indexed: 01/21/2023] Open
Abstract
Nuclear magnetic resonance (NMR) studies have revealed that fast methyl sidechain dynamics can report on entropically-driven allostery. Yet, NMR applications have been largely limited to the super-microsecond motional regimes of G protein-coupled receptors (GPCRs). We use 13Cε-methionine chemical shift-based global order parameters to test if ligands affect the fast dynamics of a thermostabilized GPCR, neurotensin receptor 1 (NTS1). We establish that the NTS1 solution ensemble includes substates with lifetimes on several, discrete timescales. The longest-lived states reflect those captured in agonist- and inverse agonist-bound crystal structures, separated by large energy barriers. We observe that the rapid fluctuations of individual methionine residues, superimposed on these long-lived states, respond collectively with the degree of fast, global dynamics correlating with ligand pharmacology. This approach lends confidence to interpreting spectra in terms of local structure and methyl dihedral angle geometry. The results suggest a role for sub-microsecond dynamics and conformational entropy in GPCR ligand discrimination.
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4
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Deluigi M, Klipp A, Klenk C, Merklinger L, Eberle SA, Morstein L, Heine P, Mittl PRE, Ernst P, Kamenecka TM, He Y, Vacca S, Egloff P, Honegger A, Plückthun A. Complexes of the neurotensin receptor 1 with small-molecule ligands reveal structural determinants of full, partial, and inverse agonism. SCIENCE ADVANCES 2021; 7:7/5/eabe5504. [PMID: 33571132 PMCID: PMC7840143 DOI: 10.1126/sciadv.abe5504] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2020] [Accepted: 12/09/2020] [Indexed: 05/15/2023]
Abstract
Neurotensin receptor 1 (NTSR1) and related G protein-coupled receptors of the ghrelin family are clinically unexploited, and several mechanistic aspects of their activation and inactivation have remained unclear. Enabled by a new crystallization design, we present five new structures: apo-state NTSR1 as well as complexes with nonpeptide inverse agonists SR48692 and SR142948A, partial agonist RTI-3a, and the novel full agonist SRI-9829, providing structural rationales on how ligands modulate NTSR1. The inverse agonists favor a large extracellular opening of helices VI and VII, undescribed so far for NTSR1, causing a constriction of the intracellular portion. In contrast, the full and partial agonists induce a binding site contraction, and their efficacy correlates with the ability to mimic the binding mode of the endogenous agonist neurotensin. Providing evidence of helical and side-chain rearrangements modulating receptor activation, our structural and functional data expand the mechanistic understanding of NTSR1 and potentially other peptidergic receptors.
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Affiliation(s)
- Mattia Deluigi
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Alexander Klipp
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Christoph Klenk
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Lisa Merklinger
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Stefanie A Eberle
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Lena Morstein
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Philipp Heine
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Peer R E Mittl
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Patrick Ernst
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Theodore M Kamenecka
- Department of Molecular Medicine, The Scripps Research Institute, Scripps Florida, 130 Scripps Way #A2A, Jupiter, FL 33458, USA
| | - Yuanjun He
- Department of Molecular Medicine, The Scripps Research Institute, Scripps Florida, 130 Scripps Way #A2A, Jupiter, FL 33458, USA
| | - Santiago Vacca
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Pascal Egloff
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Annemarie Honegger
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Andreas Plückthun
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
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5
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Nagarajan S, Alkayed NJ, Kaul S, Barnes AP. Effect of thermostable mutations on the neurotensin receptor 1 (NTSR1) activation state. J Biomol Struct Dyn 2019; 38:340-353. [DOI: 10.1080/07391102.2019.1573705] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Shanthi Nagarajan
- The Knight Cardiovascular Institute, Oregon Health Science University, Portland, OR, USA
- Medicinal Chemistry Core, Oregon Health Science University, Portland, OR, USA
| | - Nabil J. Alkayed
- The Knight Cardiovascular Institute, Oregon Health Science University, Portland, OR, USA
- Department of Anesthesiology & Perioperative Medicine, Oregon Health Science University Portland, Portland, OR, USA
| | - Sanjiv Kaul
- The Knight Cardiovascular Institute, Oregon Health Science University, Portland, OR, USA
| | - Anthony P. Barnes
- The Knight Cardiovascular Institute, Oregon Health Science University, Portland, OR, USA
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6
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Dynamic tuneable G protein-coupled receptor monomer-dimer populations. Nat Commun 2018; 9:1710. [PMID: 29703992 PMCID: PMC5923235 DOI: 10.1038/s41467-018-03727-6] [Citation(s) in RCA: 74] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 03/06/2018] [Indexed: 01/07/2023] Open
Abstract
G protein-coupled receptors (GPCRs) are the largest class of membrane receptors, playing a key role in the regulation of processes as varied as neurotransmission and immune response. Evidence for GPCR oligomerisation has been accumulating that challenges the idea that GPCRs function solely as monomeric receptors; however, GPCR oligomerisation remains controversial primarily due to the difficulties in comparing evidence from very different types of structural and dynamic data. Using a combination of single-molecule and ensemble FRET, double electron–electron resonance spectroscopy, and simulations, we show that dimerisation of the GPCR neurotensin receptor 1 is regulated by receptor density and is dynamically tuneable over the physiological range. We propose a “rolling dimer” interface model in which multiple dimer conformations co-exist and interconvert. These findings unite previous seemingly conflicting observations, provide a compelling mechanism for regulating receptor signalling, and act as a guide for future physiological studies. Evidence suggests oligomerisation of G protein-coupled receptors in membranes, but this is controversial. Here, authors use single-molecule and ensemble FRET, and spectroscopy to show that the neurotensin receptor 1 forms multiple dimer conformations that interconvert - “rolling” interfaces.
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7
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Krumm BE, Lee S, Bhattacharya S, Botos I, White CF, Du H, Vaidehi N, Grisshammer R. Structure and dynamics of a constitutively active neurotensin receptor. Sci Rep 2016; 6:38564. [PMID: 27924846 PMCID: PMC5141500 DOI: 10.1038/srep38564] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Accepted: 11/03/2016] [Indexed: 11/09/2022] Open
Abstract
Many G protein-coupled receptors show constitutive activity, resulting in the production of a second messenger in the absence of an agonist; and naturally occurring constitutively active mutations in receptors have been implicated in diseases. To gain insight into mechanistic aspects of constitutive activity, we report here the 3.3 Å crystal structure of a constitutively active, agonist-bound neurotensin receptor (NTSR1) and molecular dynamics simulations of agonist-occupied and ligand-free receptor. Comparison with the structure of a NTSR1 variant that has little constitutive activity reveals uncoupling of the ligand-binding domain from conserved connector residues, that effect conformational changes during GPCR activation. Furthermore, molecular dynamics simulations show strong contacts between connector residue side chains and increased flexibility at the intracellular receptor face as features that coincide with robust signalling in cells. The loss of correlation between the binding pocket and conserved connector residues, combined with altered receptor dynamics, possibly explains the reduced neurotensin efficacy in the constitutively active NTSR1 and a facilitated initial engagement with G protein in the absence of agonist.
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Affiliation(s)
- Brian E Krumm
- Membrane Protein Structure Function Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Department of Health and Human Services, Rockville, Maryland 20852, United States
| | - Sangbae Lee
- Department of Molecular Immunology, Beckman Research Institute of the City of Hope, 1500 E Duarte Road, Duarte, California 91010, United States
| | - Supriyo Bhattacharya
- Department of Molecular Immunology, Beckman Research Institute of the City of Hope, 1500 E Duarte Road, Duarte, California 91010, United States
| | - Istvan Botos
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland 20892, United States
| | - Courtney F White
- Membrane Protein Structure Function Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Department of Health and Human Services, Rockville, Maryland 20852, United States
| | - Haijuan Du
- Membrane Protein Structure Function Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Department of Health and Human Services, Rockville, Maryland 20852, United States
| | - Nagarajan Vaidehi
- Department of Molecular Immunology, Beckman Research Institute of the City of Hope, 1500 E Duarte Road, Duarte, California 91010, United States
| | - Reinhard Grisshammer
- Membrane Protein Structure Function Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Department of Health and Human Services, Rockville, Maryland 20852, United States
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8
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Dijkman PM, Watts A. Lipid modulation of early G protein-coupled receptor signalling events. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:2889-97. [DOI: 10.1016/j.bbamem.2015.08.004] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Revised: 07/20/2015] [Accepted: 08/10/2015] [Indexed: 11/29/2022]
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9
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Lückmann M, Holst B, Schwartz TW, Frimurer TM. In Silico Investigation of the Neurotensin Receptor 1 Binding Site: Overlapping Binding Modes for Small Molecule Antagonists and the Endogenous Peptide Agonist. Mol Inform 2015; 35:19-24. [PMID: 27491650 DOI: 10.1002/minf.201500080] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Accepted: 08/14/2015] [Indexed: 12/17/2022]
Abstract
The neurotensin receptor 1 (NTSR1) belongs to the family of 7TM, G protein-coupled receptors, and is activated by the 13-amino-acid peptide neurotensin (NTS) that has been shown to play important roles in neurological disorders and the promotion of cancer cells. Recently, a high-resolution x-ray crystal structure of NTSR1 in complex with NTS8-13 has been determined, providing novel insights into peptide ligand recognition by 7TM receptors. SR48692, a potent and selective small molecule antagonist has previously been used extensively as a tool compound to study NTSR1 receptor signaling properties. To investigate the binding mode of SR48692 and other small molecule compounds to NTSR1, we applied an Automated Ligand-guided Backbone Ensemble Receptor Optimization protocol (ALiBERO), taking receptor flexibility and ligand knowledge into account. Structurally overlapping binding poses for SR48692 and NTS8-13 were observed, despite their distinct chemical nature and inverse pharmacological profiles. The optimized models showed significantly improved ligand recognition in a large-scale virtual screening assessment compared to the crystal structure. Our models provide new insights into small molecule ligand binding to NTSR1 and could facilitate the structure-based design of non-peptide ligands for the evaluation of the pharmacological potential of NTSR1 in neurological disorders and cancer.
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Affiliation(s)
- Michael Lückmann
- M Lückmann, B Holst, TW Schwartz, TM Frimurer, Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen. Denmark
| | - Birgitte Holst
- M Lückmann, B Holst, TW Schwartz, TM Frimurer, Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen. Denmark
| | - Thue W Schwartz
- M Lückmann, B Holst, TW Schwartz, TM Frimurer, Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen. Denmark
| | - Thomas M Frimurer
- M Lückmann, B Holst, TW Schwartz, TM Frimurer, Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen. Denmark. .,TM Frimurer, Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen. Denmark.
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10
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Bhattacharya S, Lee S, Grisshammer R, Tate CG, Vaidehi N. Rapid Computational Prediction of Thermostabilizing Mutations for G Protein-Coupled Receptors. J Chem Theory Comput 2014; 10:5149-5160. [PMID: 25400524 PMCID: PMC4230369 DOI: 10.1021/ct500616v] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Indexed: 01/22/2023]
Abstract
![]()
G protein-coupled
receptors (GPCRs) are highly dynamic and often
denature when extracted in detergents. Deriving thermostable mutants
has been a successful strategy to stabilize GPCRs in detergents, but
this process is experimentally tedious. We have developed a computational
method to predict the position of the thermostabilizing mutations
for a given GPCR sequence. We have validated the method against experimentally
measured thermostability data for single mutants of the β1-adrenergic receptor (β1AR), adenosine A2A receptor (A2AR) and neurotensin receptor 1 (NTSR1).
To make these predictions we started from homology models of these
receptors of varying accuracies and generated an ensemble of conformations
by sampling the rigid body degrees of freedom of transmembrane helices.
Then, an all-atom force field function was used to calculate the enthalpy
gain, known as the “stability score” upon mutation of
every residue, in these receptor structures, to alanine. For all three
receptors, β1AR, A2AR, and NTSR1, we observed
that mutations of hydrophobic residues in the transmembrane domain
to alanine that have high stability scores correlate with high experimental
thermostability. The prediction using the stability score improves
when using an ensemble of receptor conformations compared to a single
structure, showing that receptor flexibility is important. We also
find that our previously developed LITiCon method for generating conformation
ensembles is similar in performance to predictions using ensembles
obtained from microseconds of molecular dynamics simulations (which
is computationally hundred times slower than LITiCon). We improved
the thermostability prediction by including other properties such
as residue-based stress and the extent of allosteric communication
by each residue in the stability score. Our method is the first step
toward a computational method for rapid prediction of thermostable
mutants of GPCRs.
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Affiliation(s)
- Supriyo Bhattacharya
- Division of Immunology, Beckman Research Institute of the City of Hope , 1500 East Duarte Rd, Duarte, California 91010, United States
| | - Sangbae Lee
- Division of Immunology, Beckman Research Institute of the City of Hope , 1500 East Duarte Rd, Duarte, California 91010, United States
| | - Reinhard Grisshammer
- Membrane Protein Structure Function Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health , Department of Health and Human Services, Rockville, Maryland 20852, United States
| | - Christopher G Tate
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus , Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
| | - Nagarajan Vaidehi
- Division of Immunology, Beckman Research Institute of the City of Hope , 1500 East Duarte Rd, Duarte, California 91010, United States
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11
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Scott DJ, Kummer L, Egloff P, Bathgate RAD, Plückthun A. Improving the apo-state detergent stability of NTS1 with CHESS for pharmacological and structural studies. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:2817-24. [PMID: 25064156 DOI: 10.1016/j.bbamem.2014.07.015] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Revised: 07/13/2014] [Accepted: 07/14/2014] [Indexed: 11/18/2022]
Abstract
The largest single class of drug targets is the G protein-coupled receptor (GPCR) family. Modern high-throughput methods for drug discovery require working with pure protein, but this has been a challenge for GPCRs, and thus the success of screening campaigns targeting soluble, catalytic protein domains has not yet been realized for GPCRs. Therefore, most GPCR drug screening has been cell-based, whereas the strategy of choice for drug discovery against soluble proteins is HTS using purified proteins coupled to structure-based drug design. While recent developments are increasing the chances of obtaining GPCR crystal structures, the feasibility of screening directly against purified GPCRs in the unbound state (apo-state) remains low. GPCRs exhibit low stability in detergent micelles, especially in the apo-state, over the time periods required for performing large screens. Recent methods for generating detergent-stable GPCRs, however, offer the potential for researchers to manipulate GPCRs almost like soluble enzymes, opening up new avenues for drug discovery. Here we apply cellular high-throughput encapsulation, solubilization and screening (CHESS) to the neurotensin receptor 1 (NTS1) to generate a variant that is stable in the apo-state when solubilized in detergents. This high stability facilitated the crystal structure determination of this receptor and also allowed us to probe the pharmacology of detergent-solubilized, apo-state NTS1 using robotic ligand binding assays. NTS1 is a target for the development of novel antipsychotics, and thus CHESS-stabilized receptors represent exciting tools for drug discovery.
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Affiliation(s)
- Daniel J Scott
- Department of Biochemistry, The University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland; The Florey Institute of Neuroscience and Mental Health, and The Department of Biochemistry and Molecular Biology, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Lutz Kummer
- Department of Biochemistry, The University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Pascal Egloff
- Department of Biochemistry, The University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Ross A D Bathgate
- The Florey Institute of Neuroscience and Mental Health, and The Department of Biochemistry and Molecular Biology, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Andreas Plückthun
- Department of Biochemistry, The University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
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12
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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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13
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Shibata Y, Gvozdenovic-Jeremic J, Love J, Kloss B, White JF, Grisshammer R, Tate CG. Optimising the combination of thermostabilising mutations in the neurotensin receptor for structure determination. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:1293-301. [PMID: 23337476 DOI: 10.1016/j.bbamem.2013.01.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Revised: 01/07/2013] [Accepted: 01/09/2013] [Indexed: 10/27/2022]
Abstract
Conformational thermostabilisation of G protein-coupled receptors is a successful approach for their structure determination. We have recently determined the structure of a thermostabilised neurotensin receptor NTS1 in complex with its peptide agonist and here we describe the strategy for the identification and combination of the 6 thermostabilising mutations essential for crystallisation. First, thermostability assays were performed on a panel of 340 detergent-solubilised Ala/Leu NTS1 mutants and the best 16 thermostabilising mutations were identified. These mutations were combined pair-wise in nearly all combinations (119 out of a possible 120 combinations) and each mutant was expressed and its thermostability was experimentally determined. A theoretical stability score was calculated from the sum of the stabilities measured for each double mutant and applied to develop 24 triple mutants, which in turn led to the construction of 14 quadruple mutants. Use of the thermostability data for the double mutants to predict further mutant combinations resulted in a greater percentage of the triple and quadruple mutants showing improved thermostability than if only the thermostability data for the single mutations was considered. The best quadruple mutant (NTS1-Nag36k) was further improved by including an additional 2 mutations (resulting in NTS1-GW5) that were identified from a complete Ala/Leu scan of Nag36k by testing the thermostability of the mutants in situ in whole bacteria. NTS1-GW5 had excellent stability in short chain detergents and could be readily purified as a homogenous sample that ultimately allowed crystallisation and structure determination.
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Affiliation(s)
- Yoko Shibata
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK
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14
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White JF, Noinaj N, Shibata Y, Love J, Kloss B, Xu F, Gvozdenovic-Jeremic J, Shah P, Shiloach J, Tate CG, Grisshammer R. Structure of the agonist-bound neurotensin receptor. Nature 2012; 490:508-13. [PMID: 23051748 PMCID: PMC3482300 DOI: 10.1038/nature11558] [Citation(s) in RCA: 393] [Impact Index Per Article: 32.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Accepted: 09/11/2012] [Indexed: 12/11/2022]
Abstract
Neurotensin (NT) is a 13 amino acid peptide that functions as both a neurotransmitter and a hormone through activation of the neurotensin receptor NTS1, a G protein-coupled receptor (GPCR). In the brain, NT modulates activity of dopaminergic systems, opioid-independent analgesia, and the inhibition of food intake, and in the gut NT regulates a range of digestive processes. Here we present the structure at 2.8 Å resolution of NTS1 in an active-like state, bound to NT8-13, the C terminal portion of NT responsible for agonist-induced activation of the receptor. The peptide agonist binds to NTS1 in an extended conformation nearly perpendicular to the membrane plane with the C-terminus oriented towards the receptor core. Our findings provide the first insight into the binding mode of a peptide agonist to a GPCR and may support the development of non-peptide ligands that could be useful in the treatment of neurological disorders, cancer and obesity.
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Affiliation(s)
- Jim F White
- Membrane Protein Structure Function Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Department of Health and Human Services, Rockville, Maryland 20852, USA
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15
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Schlinkmann KM, Hillenbrand M, Rittner A, Künz M, Strohner R, Plückthun A. Maximizing detergent stability and functional expression of a GPCR by exhaustive recombination and evolution. J Mol Biol 2012; 422:414-28. [PMID: 22683350 DOI: 10.1016/j.jmb.2012.05.039] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Revised: 05/27/2012] [Accepted: 05/30/2012] [Indexed: 10/28/2022]
Abstract
To identify structural features in a G-protein-coupled receptor (GPCR) crucial for biosynthesis, stability in the membrane and stability in detergent micelles, we developed an evolutionary approach using expression in the inner membrane of Escherichia coli. From the analysis of 800,000 sequences of the rat neurotensin receptor 1, in which every amino acid had been varied to all 64 codons, we uncovered several "shift" positions, where the selected population focuses on a residue different from wild type. Here, we employed in vitro DNA recombination and a comprehensive synthetic binary library made by the Slonomics® technology, allowing us to uncover additive and synergistic effects in the structure that maximize both detergent stability and functional expression. We identified variants with >25,000 functional molecules per E. coli cell, a 50-fold increase over wild type, and observed strong coevolution of detergent stability. We arrived at receptor variants highly stable in short-chain detergents, much more so than those found by alanine scanning on the same receptor. These evolved GPCRs continue to be able to signal through the G-protein. We discuss the structural reasons for these improvements achieved through directed evolution.
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Affiliation(s)
- Karola M Schlinkmann
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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16
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Diaz C, Leplatois P, Angelloz-Nicoud P, Lecomte M, Josse A, Delpech M, Pecceu F, Loison G, Shire D, Pascal M, Ferrara P, Ferran E. Differential Virtual Screening (DVS) with Active and Inactive Molecular Models for Finding and Profiling GPCR Modulators: Case of the CCK1 Receptor. Mol Inform 2011; 30:345-58. [DOI: 10.1002/minf.201000180] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2010] [Accepted: 02/23/2011] [Indexed: 11/10/2022]
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17
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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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18
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Thermostabilization of the neurotensin receptor NTS1. J Mol Biol 2009; 390:262-77. [PMID: 19422831 PMCID: PMC2696590 DOI: 10.1016/j.jmb.2009.04.068] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2009] [Revised: 04/27/2009] [Accepted: 04/29/2009] [Indexed: 11/20/2022]
Abstract
Structural studies on G protein-coupled receptors (GPCRs) have been
hampered for many years by their instability in detergent solution and by the
number of potential conformations that receptors can adopt. Recently, the
structures of the β1 and β2 adrenergic
receptors and the adenosine A2a receptor were determined with
antagonist bound, a receptor conformation that is thought to be more stable than
the agonist-bound state. In contrast to these receptors, the neurotensin
receptor NTS1 is much less stable in detergent solution. We have therefore used
a systematic mutational approach coupled to activity assays to identify receptor
mutants suitable for crystallisation, both alone and in complex with the peptide
agonist, neurotensin. The best receptor mutant, NTS1-7m, contained 4 point
mutations. It showed increased stability compared to the wild type receptor, in
the absence of ligand, after solubilisation with a variety of detergents. In
addition, NTS1-7m bound to neurotensin was more stable than unliganded NTS1-7m.
Of the four thermostabilising mutations, only one residue (A86L) is predicted to
be in the lipid environment. In contrast, I260A appears to be buried within the
transmembrane helix bundle, F342A may form a distant part of the putative ligand
binding site, whereas F358A is likely to be in a region important for receptor
activation. NTS1-7m binds neurotensin with a similar affinity to the wild-type
receptor. However, agonist dissociation was slower, and NTS1-7m activated G
proteins poorly. The affinity of NTS1-7m for the antagonist SR48692 was also
lower than that of the wild-type receptor. Thus we have successfully stabilised
NTS1 in an agonist-binding conformation that does not efficiently couple to G
proteins.
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19
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Directed evolution of a G protein-coupled receptor for expression, stability, and binding selectivity. Proc Natl Acad Sci U S A 2008; 105:14808-13. [PMID: 18812512 DOI: 10.1073/pnas.0803103105] [Citation(s) in RCA: 152] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We outline a powerful method for the directed evolution of integral membrane proteins in the inner membrane of Escherichia coli. For a mammalian G protein-coupled receptor, we arrived at a sequence with an order-of-magnitude increase in functional expression that still retains the biochemical properties of wild type. This mutant also shows enhanced heterologous expression in eukaryotes (12-fold in Pichia pastoris and 3-fold in HEK293T cells) and greater stability when solubilized and purified, indicating that the biophysical properties of the protein had been under the pressure of selection. These improvements arise from multiple small contributions, which would be difficult to assemble by rational design. In a second screen, we rapidly pinpointed a single amino acid substitution in wild type that abolishes antagonist binding while retaining agonist-binding affinity. These approaches may alleviate existing bottlenecks in structural studies of these targets by providing sufficient quantities of stable variants in defined conformational states.
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20
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Engineering G protein-coupled receptor expression in bacteria. Proc Natl Acad Sci U S A 2008; 105:14747-8. [PMID: 18812517 DOI: 10.1073/pnas.0807741105] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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21
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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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22
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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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Abstract
Three neurotensin (NT) receptors have been cloned to date, two of which, NTS1 and NTS2, belong to the family of seven transmembrane domain receptors coupled to G proteins (GPCRs). NTS1 and NTS2 may activate multiple signal transduction pathways, involving several G proteins. However, whereas NT acts as an agonist towards all NTS1-mediated pathways, this peptide may exert either agonist or antagonist activities, depending on the NTS2-mediated pathway in question. Studies on these receptors reinforce the concept of independence between multiple signals potentially mediated through a single GPCR, generating a wide diversity of functional responses depending on the host cell and the ligand.
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Affiliation(s)
- Didier Pelaprat
- INSERM, U.773, CRB3, EA 3512, Faculté de Médecine Xavier Bichat, 16 rue Henri Huchard, BP416, 75870 Paris Cedex 18, France.
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Abstract
The subtype 1 neurotensin receptor (NTS1) belongs to the family of G protein coupled receptors with seven transmembrane domains and mediates most of the known effects of neurotensin. In the past years, mutagenesis studies have allowed to delineate functional regions of the receptor involved in agonist and antagonist binding, G protein coupling, sodium sensitivity of agonist binding, and agonist-induced receptor internalization. These data are reviewed and discussed in the present paper.
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Affiliation(s)
- Patrick Kitabgi
- INSERM, UMR S 732, Université Pierre et Marie Curie-Paris 6, Hopital St-Antoine, 184 rue du Faubourg St-Antoine, 75571 Paris Cedex 12, France.
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25
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Favre N, Fanelli F, Missotten M, Nichols A, Wilson J, di Tiani M, Rommel C, Scheer A. The DRY motif as a molecular switch of the human oxytocin receptor. Biochemistry 2005; 44:9990-10008. [PMID: 16042376 DOI: 10.1021/bi0509853] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The human oxytocin receptor is known to exhibit promiscuous activity by coupling to both Galpha(q) and Galpha(i) G proteins to activate distinct signaling pathways. A single-amino acid substitution within the highly conserved E/DRY motif at the cytosolic extension of helix 3 [i.e., D136(3.49)N] increased the rate of both basal and agonist-stimulated inositol phosphate (IP(3)) accumulation of the receptor. Furthermore, like for a typical constitutively active receptor, the partial agonist arginine vasopressin behaved as a full agonist for the D136(3.49)N mutant. Subsequently, both oxytocin and arginine vasopressin showed an increased potency in stimulating IP3 accumulation as compared to the wild-type receptor. Very interestingly, our experiments provide strong evidence that the D136(3.49)N mutant inhibits receptor signaling via Galpha(i)-mediated pathways while increasing the activity through the Galpha(q)-mediated pathways. Molecular simulations of the free and OT-bound forms of wild-type OTR and of the D136(3.49)N constitutively active mutant suggest that the receptor portions close to the E/DRY and NPxxY motifs are particularly susceptible to undergoing structural modification in response to activating mutations and agonist binding. Furthermore, computational modeling suggests that the OT-bound form of wild-type OTR is able to explore more states than the OT-bound form of the D136(3.49)N constitutively active mutant, consistent with its G protein promiscuity. Taken together, these observations emphasize the important role of the E/DRY motif not only in receptor activation but also in the promiscuity of G protein coupling. Knowledge of the mechanism of selective G protein coupling could aid drug discovery efforts to identify signaling specific therapies.
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Affiliation(s)
- Nicolas Favre
- Serono Pharmaceutical Research Institute, 14, Ch. des Aulx, 1228 Plan-les-Ouates, Geneva, Switzerland
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26
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Hermans E. Biochemical and pharmacological control of the multiplicity of coupling at G-protein-coupled receptors. Pharmacol Ther 2003; 99:25-44. [PMID: 12804697 DOI: 10.1016/s0163-7258(03)00051-2] [Citation(s) in RCA: 221] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
For decades, it has been generally proposed that a given receptor always interacts with a particular GTP-binding protein (G-protein) or with multiple G-proteins within one family. However, for several G-protein-coupled receptors (GPCR), it now becomes generally accepted that simultaneous functional coupling with distinct unrelated G-proteins can be observed, leading to the activation of multiple intracellular effectors with distinct efficacies and/or potencies. Multiplicity in G-protein coupling is frequently observed in artificial expression systems where high densities of receptors are obtained, raising the question of whether such complex signalling reveals artefactual promiscuous coupling or is a genuine property of GPCRs. Multiple biochemical and pharmacological evidence in favour of an intrinsic property of GPCRs were obtained in recent studies. Thus, there are now many examples showing that the coupling to multiple signalling pathways is dependent on the agonist used (agonist trafficking of receptor signals). In addition, the different couplings were demonstrated to involve distinct molecular determinants of the receptor and to show distinct desensitisation kinetics. Such multiplicity of signalling at the level of G-protein coupling leads to a further complexity in the functional response to agonist stimulation of one of the most elaborate cellular transmission systems. Indeed, the physiological relevance of such versatility in signalling associated with a single receptor requires the existence of critical mechanisms of dynamic regulation of the expression, the compartmentalisation, and the activity of the signalling partners. This review aims at summarising the different studies that support the concept of multiplicity of G-protein coupling. The physiological and pharmacological relevance of this coupling promiscuity will be discussed.
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Affiliation(s)
- Emmanuel Hermans
- Laboratoire de Pharmacologie Expérimentale, Université Catholique de Louvain, FARL 54.10, Avenue Hippocrate 54, B-1200 Brussels, Belgium.
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