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Boon K, Vanalken N, Szpakowska M, Chevigné A, Schols D, Van Loy T. Systematic assessment of chemokine ligand bias at the human chemokine receptor CXCR2 indicates G protein bias over β-arrestin recruitment and receptor internalization. Cell Commun Signal 2024; 22:43. [PMID: 38233929 PMCID: PMC10795402 DOI: 10.1186/s12964-023-01460-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2023] [Accepted: 12/26/2023] [Indexed: 01/19/2024] Open
Abstract
BACKGROUND The human CXC chemokine receptor 2 (CXCR2) is a G protein-coupled receptor (GPCR) interacting with multiple chemokines (i.e., CXC chemokine ligands CXCL1-3 and CXCL5-8). It is involved in inflammatory diseases as well as cancer. Consequently, much effort is put into the identification of CXCR2 targeting drugs. Fundamental research regarding CXCR2 signaling is mainly focused on CXCL8 (IL-8), which is the first and best described high-affinity ligand for CXCR2. Much less is known about CXCR2 activation induced by other chemokines and it remains to be determined to what extent potential ligand bias exists within this signaling system. This insight might be important to unlock new opportunities in therapeutic targeting of CXCR2. METHODS Ligand binding was determined in a competition binding assay using labeled CXCL8. Activation of the ELR + chemokine-induced CXCR2 signaling pathways, including G protein activation, β-arrestin1/2 recruitment, and receptor internalization, were quantified using NanoBRET-based techniques. Ligand bias within and between these pathways was subsequently investigated by ligand bias calculations, with CXCL8 as the reference CXCR2 ligand. Statistical significance was tested through a one-way ANOVA followed by Dunnett's multiple comparisons test. RESULTS All chemokines (CXCL1-3 and CXCL5-8) were able to displace CXCL8 from CXCR2 with high affinity and activated the same panel of G protein subtypes (Gαi1, Gαi2, Gαi3, GαoA, GαoB, and Gα15) without any statistically significant ligand bias towards any one type of G protein. Compared to CXCL8, all other chemokines were less potent in β-arrestin1 and -2 recruitment and receptor internalization while equivalently activating G proteins, indicating a G protein activation bias for CXCL1,-2,-3,-5,-6 and CXCL7. Lastly, with CXCL8 used as reference ligand, CXCL2 and CXCL6 showed ligand bias towards β-arrestin1/2 recruitment compared to receptor internalization. CONCLUSION This study presents an in-depth analysis of signaling bias upon CXCR2 stimulation by its chemokine ligands. Using CXCL8 as a reference ligand for bias index calculations, no ligand bias was observed between chemokines with respect to activation of separate G proteins subtypes or recruitment of β-arrestin1/2 subtypes, respectively. However, compared to β-arrestin recruitment and receptor internalization, CXCL1-3 and CXCL5-7 were biased towards G protein activation when CXCL8 was used as reference ligand.
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Affiliation(s)
- Katrijn Boon
- Department of Microbiology, Immunology and Transplantation, Rega Institute for Medical Research, Laboratory of Virology and Chemotherapy, KU Leuven, B-3000, Leuven, Belgium
| | - Nathan Vanalken
- Department of Microbiology, Immunology and Transplantation, Rega Institute for Medical Research, Laboratory of Virology and Chemotherapy, KU Leuven, B-3000, Leuven, Belgium
| | - Martyna Szpakowska
- Department of Infection and Immunity, Immuno-Pharmacology and Interactomics, Luxembourg Institute of Health (LIH), Esch-Sur-Alzette, Luxembourg
| | - Andy Chevigné
- Department of Infection and Immunity, Immuno-Pharmacology and Interactomics, Luxembourg Institute of Health (LIH), Esch-Sur-Alzette, Luxembourg
| | - Dominique Schols
- Department of Microbiology, Immunology and Transplantation, Rega Institute for Medical Research, Laboratory of Virology and Chemotherapy, KU Leuven, B-3000, Leuven, Belgium
| | - Tom Van Loy
- Department of Microbiology, Immunology and Transplantation, Rega Institute for Medical Research, Laboratory of Virology and Chemotherapy, KU Leuven, B-3000, Leuven, Belgium.
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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: 8] [Impact Index Per Article: 8.0] [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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Ives A, Dunn HA, Afsari HS, Seckler HDS, Foroutan MJ, Chavez E, Melani RD, Fellers RT, LeDuc RD, Thomas PM, Martemyanov KA, Kelleher NL, Vafabakhsh R. Middle-Down Mass Spectrometry Reveals Activity-Modifying Phosphorylation Barcode in a Class C G Protein-Coupled Receptor. J Am Chem Soc 2022; 144:23104-23114. [PMID: 36475650 PMCID: PMC9785046 DOI: 10.1021/jacs.2c10697] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
G protein-coupled receptors (GPCRs) are the largest family of membrane receptors in humans. They mediate nearly all aspects of human physiology and thus are of high therapeutic interest. GPCR signaling is regulated in space and time by receptor phosphorylation. It is believed that different phosphorylation states are possible for a single receptor, and each encodes for unique signaling outcomes. Methods to determine the phosphorylation status of GPCRs are critical for understanding receptor physiology and signaling properties of GPCR ligands and therapeutics. However, common proteomic techniques have provided limited quantitative information regarding total receptor phosphorylation stoichiometry, relative abundances of isomeric modification states, and temporal dynamics of these parameters. Here, we report a novel middle-down proteomic strategy and parallel reaction monitoring (PRM) to quantify the phosphorylation states of the C-terminal tail of metabotropic glutamate receptor 2 (mGluR2). By this approach, we found that mGluR2 is subject to both basal and agonist-induced phosphorylation at up to four simultaneous sites with varying probability. Using a PRM tandem mass spectrometry methodology, we localized the positions and quantified the relative abundance of phosphorylations following treatment with an agonist. Our analysis showed that phosphorylation within specific regions of the C-terminal tail of mGluR2 is sensitive to receptor activation, and subsequent site-directed mutagenesis of these sites identified key regions which tune receptor sensitivity. This study demonstrates that middle-down purification followed by label-free quantification is a powerful, quantitative, and accessible tool for characterizing phosphorylation states of GPCRs and other challenging proteins.
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Affiliation(s)
- Ashley
N. Ives
- Department
of Chemistry, Northwestern University, Evanston, Illinois 60208 United States
| | - Henry A. Dunn
- Department
of Neuroscience, The Scripps Research Institute, Jupiter, Florida 33458, United States,Department
of Pharmacology and Therapeutics, University
of Manitoba, Winnipeg, Manitoba R3E 0T6, Canada,Division
of Neurodegenerative Disorders, St. Boniface Hospital Albrechtsen
Research Centre, Winnipeg, Manitoba R2H 2A6, Canada
| | - Hamid Samareh Afsari
- Department
of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208, United States
| | | | - Max J. Foroutan
- Department
of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208, United States
| | - Erica Chavez
- Department
of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208, United States
| | - Rafael D. Melani
- Department
of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208, United States,National
Resource for Translational and Developmental Proteomics, Northwestern University, Evanston, Illinois 60208, United States
| | - Ryan T. Fellers
- National
Resource for Translational and Developmental Proteomics, Northwestern University, Evanston, Illinois 60208, United States
| | - Richard D. LeDuc
- National
Resource for Translational and Developmental Proteomics, Northwestern University, Evanston, Illinois 60208, United States
| | - Paul M. Thomas
- Department
of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208, United States,National
Resource for Translational and Developmental Proteomics, Northwestern University, Evanston, Illinois 60208, United States
| | - Kirill A. Martemyanov
- Department
of Neuroscience, The Scripps Research Institute, Jupiter, Florida 33458, United States
| | - Neil L. Kelleher
- Department
of Chemistry, Northwestern University, Evanston, Illinois 60208 United States,Department
of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208, United States,National
Resource for Translational and Developmental Proteomics, Northwestern University, Evanston, Illinois 60208, United States
| | - Reza Vafabakhsh
- Department
of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208, United States,
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Abstract
The β-arrestin proteins are key regulators of G protein-coupled receptors, serving at least three distinct functions: inhibiting receptor signaling through G proteins, directing receptor trafficking from the cell surface after activation, and transmitting receptor-initiated signals directly. How the two β-arrestin proteins perform these many functions for hundreds of receptor types throughout the body, and specifically how β-arrestin-mediated signaling can be tuned to cellular conditions, remains an open question. Function-based evidence and recent structure-based evidence have suggested that patterns of receptor phosphorylation ("barcodes") may be a critical determinant of β-arrestin action. In this issue of EMBO Reports, Baidya and colleagues (Baidya et al, 2020a) report that specific receptor phosphorylation site clusters ("codes") determine whether β-arrestin 1 acts to promote or inhibit receptor activation of Erk mitogen-activated protein kinases. They provide direct evidence for a functional barcode system by transferring inhibitory and stimulatory codes between receptors, suggesting future work to understand just how code site location in a receptor and its phosphorylation status can lead to very different functions of bound β-arrestin proteins.
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Affiliation(s)
- Richard T Premont
- Harrington Discovery Institute, University Hospitals Cleveland Medical Center, Cleveland, OH, USA.,Institute for Transformative Molecular Medicine and Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH, USA
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