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Wei JD, Kim JH. Two distinct forms of human BLT2: long-form and short-form BLT2. Front Cell Dev Biol 2023; 11:1288373. [PMID: 37954206 PMCID: PMC10637354 DOI: 10.3389/fcell.2023.1288373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Accepted: 10/11/2023] [Indexed: 11/14/2023] Open
Abstract
BLT2 is a low-affinity leukotriene B4 receptor that plays an essential role in the pathogenesis of various inflammatory diseases, including asthma and cancer. BLT2 is minimally expressed in a normal internal environment but is overexpressed in a stress-induced inflammatory environment. Recent research indicated that human BLT2 has two distinct forms. Although their functions are likely to be different, very few studies investigated these differences. Therefore, this paper will discuss about the two distinct forms of human BLT2; the short-form of BLT2 and the long-form of BLT2.
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Affiliation(s)
- Jun-Dong Wei
- Department of Basic Medical Science, Medical College, Taizhou University, Taizhou, China
| | - Jae-Hong Kim
- Division of Life Sciences, College of Life Sciences, Korea University, Seoul, Republic of Korea
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2
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Kline JM, Heusinkveld LE, Taranto E, Martin CB, Tomasi AG, Hsu IJ, Cho K, Khillan JS, Murphy PM, Pontejo SM. Structural and functional analysis of Ccr1l1, a Rodentia-restricted eosinophil-selective chemokine receptor homologue. J Biol Chem 2021; 296:100373. [PMID: 33548230 PMCID: PMC7949164 DOI: 10.1016/j.jbc.2021.100373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 01/26/2021] [Accepted: 02/01/2021] [Indexed: 11/25/2022] Open
Abstract
Mouse Ccr1l1 (Ccr1-like 1) encodes an orphan G-protein-coupled receptor (GPCR) with the highest homology to the inflammatory and highly promiscuous chemokine receptors Ccr1 and Ccr3 (70 and 50% amino acid identity, respectively). Ccr1l1 was first cloned in 1995, yet current knowledge of this putative chemokine receptor is limited to its gene organization and chromosomal localization. Here we report that Ccr1l1 is a Rodentia-specific gene selectively expressed in eosinophils. However, eosinophil phenotypes, development, and responsiveness to chemokines were all normal in naïve Ccr1l1 knockout mice. We demonstrate for the first time that recombinant Ccr1l1 is expressed on the plasma membrane of transfected cells and contains an extracellular N terminus and an intracellular C terminus, consistent with GPCR topology. Using receptor internalization, β-arrestin recruitment, calcium flux, and chemotaxis assays, we excluded all 37 available mouse chemokines, including Ccr1 ligands, and two viral chemokines as Ccr1l1 ligands, and demonstrated that mouse Ccr1, but not Ccr1l1, exhibits constitutive signaling activity. However, sequence analysis and structural modeling revealed that Ccr1l1 is well equipped to act as a classical signaling GPCR, with N-terminal sulfotyrosines as the only signaling and chemokine-binding determinant absent in Ccr1l1. Hereof, we show that a sulfatable N-terminal Ccr1 Y18 residue is essential for chemotaxis and calcium responses induced by Ccl3 and Ccl9/10, but substituting the corresponding Ccr1l1 F19 residue with tyrosine failed to confer responsiveness to Ccr1 ligands. Although Ccr1l1 remains an extreme outlier in the chemokine receptor family, our study supports that it might respond to unidentified mouse chemokine ligands in eosinophil-driven immune responses.
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Affiliation(s)
- Jaclyn M Kline
- Laboratory of Molecular Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Lauren E Heusinkveld
- Laboratory of Molecular Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Eleanor Taranto
- Laboratory of Molecular Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Clare B Martin
- Laboratory of Molecular Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Alessandra G Tomasi
- Laboratory of Molecular Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Isabel J Hsu
- Laboratory of Molecular Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Kyoungin Cho
- Comparative Medicine Branch, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Jaspal S Khillan
- Comparative Medicine Branch, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Philip M Murphy
- Laboratory of Molecular Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Sergio M Pontejo
- Laboratory of Molecular Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA.
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3
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Szpakowska M, Meyrath M, Reynders N, Counson M, Hanson J, Steyaert J, Chevigné A. Mutational analysis of the extracellular disulphide bridges of the atypical chemokine receptor ACKR3/CXCR7 uncovers multiple binding and activation modes for its chemokine and endogenous non-chemokine agonists. Biochem Pharmacol 2018. [DOI: 10.1016/j.bcp.2018.03.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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4
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Liu X, Kang L, Liu W, Lou B, Wu C, Jiang L. Molecular characterization and expression analysis of the large yellow croaker (Larimichthys crocea) chemokine receptors CXCR2, CXCR3, and CXCR4 after bacterial and poly I:C challenge. FISH & SHELLFISH IMMUNOLOGY 2017; 70:228-239. [PMID: 28870858 DOI: 10.1016/j.fsi.2017.08.029] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Revised: 08/19/2017] [Accepted: 08/27/2017] [Indexed: 06/07/2023]
Abstract
The large yellow croaker (Larimichthys crocea) has a well-developed innate immune system. We studied a component of this system, chemokine receptor CXCR family. In this study, we report the full-length open reading frames, as well as the identification and characterization of the chemokine receptor genes CXCR2 (LycCXCR2), CXCR3 (LycCXCR3), and CXCR4 (LycCXCR4) of large yellow croaker. We report that LycCXCR3 and LycCXCR4 are evolving neutrally according to PAML analyses. Quantitative real-time PCR analysis revealed that CXCR transcripts were expressed in all examined tissues. The expression of chemokine receptors LycCXCR2, LycCXCR3, and LycCXCR4 was elevated in the kidney, spleen, and particularly the liver of the large yellow croaker after challenge with Vibrio anguillarum and polyinosinic:polycytidylic acid (poly I:C). These results suggest that LycCXCR2, LycCXCR3, and LycCXCR4 may be important immune-related genes, playing crucial roles in immune defence against bacterial infection.
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MESH Headings
- Amino Acid Sequence
- Animals
- Base Sequence
- Fish Diseases/immunology
- Fish Proteins/chemistry
- Fish Proteins/genetics
- Fish Proteins/immunology
- Gene Expression Profiling/veterinary
- Gene Expression Regulation/immunology
- Immunity, Innate/genetics
- Perciformes/genetics
- Perciformes/immunology
- Phylogeny
- Poly I-C/pharmacology
- Receptors, CXCR3/chemistry
- Receptors, CXCR3/genetics
- Receptors, CXCR3/immunology
- Receptors, CXCR4/chemistry
- Receptors, CXCR4/genetics
- Receptors, CXCR4/immunology
- Receptors, Chemokine/chemistry
- Receptors, Chemokine/genetics
- Receptors, Chemokine/immunology
- Receptors, Interleukin-8B/chemistry
- Receptors, Interleukin-8B/genetics
- Receptors, Interleukin-8B/immunology
- Sequence Alignment/veterinary
- Vibrio/physiology
- Vibrio Infections/immunology
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Affiliation(s)
- Xiaoxu Liu
- National Engineering Research Center of Marine Facilities Aquaculture, College of Marine Science, Zhejiang Ocean University, No. 1 Haida South Road, Dinghai District, Zhoushan, Zhejiang Province, 316022, China
| | - Lisen Kang
- National Engineering Research Center of Marine Facilities Aquaculture, College of Marine Science, Zhejiang Ocean University, No. 1 Haida South Road, Dinghai District, Zhoushan, Zhejiang Province, 316022, China
| | - Wei Liu
- National Engineering Research Center of Marine Facilities Aquaculture, College of Marine Science, Zhejiang Ocean University, No. 1 Haida South Road, Dinghai District, Zhoushan, Zhejiang Province, 316022, China
| | - Bao Lou
- Marine Fishery Institute of Zhejiang Province, Key Laboratory of Mariculturre and Enhancement of Zhejiang Province, Zhoushan, Zhejiang Province, 316021, China
| | - Changwen Wu
- National Engineering Research Center of Marine Facilities Aquaculture, College of Marine Science, Zhejiang Ocean University, No. 1 Haida South Road, Dinghai District, Zhoushan, Zhejiang Province, 316022, China
| | - Lihua Jiang
- National Engineering Research Center of Marine Facilities Aquaculture, College of Marine Science, Zhejiang Ocean University, No. 1 Haida South Road, Dinghai District, Zhoushan, Zhejiang Province, 316022, China.
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5
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Barington L, Rummel PC, Lückmann M, Pihl H, Larsen O, Daugvilaite V, Johnsen AH, Frimurer TM, Karlshøj S, Rosenkilde MM. Role of Conserved Disulfide Bridges and Aromatic Residues in Extracellular Loop 2 of Chemokine Receptor CCR8 for Chemokine and Small Molecule Binding. J Biol Chem 2016; 291:16208-20. [PMID: 27226537 DOI: 10.1074/jbc.m115.706747] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2015] [Indexed: 11/06/2022] Open
Abstract
Chemokine receptors play important roles in the immune system and are linked to several human diseases. The initial contact of chemokines with their receptors depends on highly specified extracellular receptor features. Here we investigate the importance of conserved extracellular disulfide bridges and aromatic residues in extracellular loop 2 (ECL-2) for ligand binding and activation in the chemokine receptor CCR8. We used inositol 1,4,5-trisphosphate accumulation and radioligand binding experiments to determine the impact of receptor mutagenesis on both chemokine and small molecule agonist and antagonist binding and action in CCR8. We find that the seven-transmembrane (TM) receptor conserved disulfide bridge (7TM bridge) linking transmembrane helix III (TMIII) and ECL-2 is crucial for chemokine and small molecule action, whereas the chemokine receptor conserved disulfide bridge between the N terminus and TMVII is needed only for chemokines. Furthermore, we find that two distinct aromatic residues in ECL-2, Tyr(184) (Cys + 1) and Tyr(187) (Cys + 4), are crucial for binding of the CC chemokines CCL1 (agonist) and MC148 (antagonist), respectively, but not for small molecule binding. Finally, using in silico modeling, we predict an aromatic cluster of interaction partners for Tyr(187) in TMIV (Phe(171)) and TMV (Trp(194)). We show in vitro that these residues are crucial for the binding and action of MC148, thus supporting their participation in an aromatic cluster with Tyr(187) This aromatic cluster appears to be present in a large number of CC chemokine receptors and thereby could play a more general role to be exploited in future drug development targeting these receptors.
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Affiliation(s)
| | - Pia C Rummel
- From the Department of Neuroscience and Pharmacology
| | - Michael Lückmann
- From the Department of Neuroscience and Pharmacology, the Novo Nordisk Foundation Center for Basic Metabolic Research, and
| | - Heidi Pihl
- From the Department of Neuroscience and Pharmacology
| | - Olav Larsen
- From the Department of Neuroscience and Pharmacology
| | | | - Anders H Johnsen
- the Department of Clinical Biochemistry, Rigshospitalet, DK-2100 Copenhagen, Denmark
| | - Thomas M Frimurer
- the Novo Nordisk Foundation Center for Basic Metabolic Research, and the Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, DK-2200 Copenhagen, Denmark and
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6
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Qi Z, Jiang Y, Holland JW, Nie P, Secombes CJ, Wang T. Identification and expression analysis of an atypical chemokine receptor-2 (ACKR2)/CC chemokine binding protein-2 (CCBP2) in rainbow trout (Oncorhynchus mykiss). FISH & SHELLFISH IMMUNOLOGY 2015; 44:389-98. [PMID: 25747793 DOI: 10.1016/j.fsi.2015.02.038] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Revised: 02/23/2015] [Accepted: 02/24/2015] [Indexed: 06/04/2023]
Abstract
Atypical chemokine receptors (ACKRs) have emerged as key components of the chemokine system, with an essential regulatory function in innate and adaptive immune responses and inflammation. In mammals ACKR2 is a 'scavenging' receptor for inflammatory CC chemokines and plays a central role in the resolution of in vivo inflammatory responses. An ACKR2 like gene has been identified and cloned in rainbow trout (Teleostei) in the present study, enabling the further identification of this molecule in another group of ray-finned teleost fish (Holostei), in a lobe-finned fish (Sarcopterygii-coelacanth), and in reptiles. The identity of these ACKR2 molecules is supported by their conserved structure, and by phylogenetic tree and synteny analysis. Trout ACKR2 is highly expressed in spleen and head kidney, suggesting a homeostatic role of this receptor in limiting the availability of its potential ligands. Trout ACKR2 expression can be modulated in vivo by bacterial and parasitic infections, and in vitro by PAMPs (poly I:C and peptidoglycan) and cytokines (IL-6, TNF-α, IFN-γ and IL-21) in a time dependent manner. These patterns of expression and modulation suggest that trout ACKR2 is regulated in a complex way and has an important role in control of the chemokine network in fish as in mammals.
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Affiliation(s)
- Zhitao Qi
- Scottish Fish Immunology Research Centre, Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK; Key Laboratory of Aquaculture and Ecology of Coastal Pool in Jiangsu Province, Department of Ocean Technology, Yancheng Institute of Technology, Yancheng, Jiangsu, 224051, China
| | - Yousheng Jiang
- Scottish Fish Immunology Research Centre, Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK; College of Fishery and Life Science, Shanghai Ocean University, Shanghai, 201306, China
| | - Jason W Holland
- Scottish Fish Immunology Research Centre, Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK
| | - Pin Nie
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, 430072, China
| | - Christopher J Secombes
- Scottish Fish Immunology Research Centre, Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK
| | - Tiehui Wang
- Scottish Fish Immunology Research Centre, Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK.
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7
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Xu Q, Li R, Monte MM, Jiang Y, Nie P, Holland JW, Secombes CJ, Wang T. Sequence and expression analysis of rainbow trout CXCR2, CXCR3a and CXCR3b aids interpretation of lineage-specific conversion, loss and expansion of these receptors during vertebrate evolution. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2014; 45:201-213. [PMID: 24613851 PMCID: PMC4052464 DOI: 10.1016/j.dci.2014.03.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Revised: 03/02/2014] [Accepted: 03/02/2014] [Indexed: 06/03/2023]
Abstract
The chemokine receptors CXCR1-3 bind to 11 chemokines (CXCL1-11) that are clustered on the same chromosome in mammals but are largely missing in ray-finned fish. A second CXCR1/2, and a CXCR3a and CXCR3b gene have been cloned in rainbow trout. Analysis of CXCR1-R3 genes in lobe-finned fish, ray-finned fish and tetrapod genomes revealed that the teleostomian ancestor likely possessed loci containing both CXCR1 and CXCR2, and CXCR3a and CXCR3b. Based on this synteny analysis the first trout CXCR1/2 gene was renamed CXCR1, and the new gene CXCR2. The CXCR1/R2 locus was shown to have further expanded in ray-finned fish. In relation to CXCR3, mammals appear to have lost CXCR3b and birds both CXCR3a and CXCR3b during evolution. Trout CXCR1-R3 have distinct tissue expression patterns and are differentially modulated by PAMPs, proinflammatory cytokines and infections. They are highly expressed in macrophages and neutrophils, with CXCR1 and CXCR2 also expressed in B-cells.
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Affiliation(s)
- Qiaoqing Xu
- Scottish Fish Immunology Research Centre, School of Biological Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK; School of Animal Science, Yangtze University, Jingzhou, Hubei Province 434020, China
| | - Ronggai Li
- Scottish Fish Immunology Research Centre, School of Biological Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK
| | - Milena M Monte
- Scottish Fish Immunology Research Centre, School of Biological Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK
| | - Yousheng Jiang
- Scottish Fish Immunology Research Centre, School of Biological Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK; College of Fishery and Life Science, Shanghai Ocean University, Shanghai 201306, China
| | - Pin Nie
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province 430072, China
| | - Jason W Holland
- Scottish Fish Immunology Research Centre, School of Biological Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK
| | - Chris J Secombes
- Scottish Fish Immunology Research Centre, School of Biological Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK.
| | - Tiehui Wang
- Scottish Fish Immunology Research Centre, School of Biological Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK.
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8
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Stephens B, Handel TM. Chemokine receptor oligomerization and allostery. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 115:375-420. [PMID: 23415099 DOI: 10.1016/b978-0-12-394587-7.00009-9] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Oligomerization of chemokine receptors has been reported to influence many aspects of receptor function through allosteric communication between receptor protomers. Allosteric interactions within chemokine receptor hetero-oligomers have been shown to cause negative cooperativity in the binding of chemokines and to inhibit receptor activation in the case of some receptor pairs. Other receptor pairs can cause enhanced signaling and even activate entirely new, hetero-oligomer-specific signaling complexes and responses downstream of receptor activation. Many mechanisms contribute to these effects including direct allosteric coupling between the receptors, G protein-mediated allostery, G protein stealing, ligand sequestration, and recruitment of new intracellular proteins by exposing unique binding interfaces on the oligomerized receptors. These effects present both challenges as well as exciting opportunities for drug discovery. One of the most difficult challenges will involve determining if and when hetero-oligomers versus homomeric receptors are involved in specific disease states.
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Affiliation(s)
- Bryan Stephens
- Skaggs School of Pharmacy and Pharmaceutical Science, University of California, San Diego, La Jolla, California, USA
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9
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Rummel PC, Thiele S, Hansen LS, Petersen TP, Sparre-Ulrich AH, Ulven T, Rosenkilde MM. Extracellular Disulfide Bridges Serve Different Purposes in Two Homologous Chemokine Receptors, CCR1 and CCR5. Mol Pharmacol 2013; 84:335-45. [DOI: 10.1124/mol.113.086702] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
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10
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Szpakowska M, Fievez V, Arumugan K, van Nuland N, Schmit JC, Chevigné A. Function, diversity and therapeutic potential of the N-terminal domain of human chemokine receptors. Biochem Pharmacol 2012; 84:1366-80. [PMID: 22935450 DOI: 10.1016/j.bcp.2012.08.008] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2012] [Revised: 08/08/2012] [Accepted: 08/09/2012] [Indexed: 11/16/2022]
Abstract
Chemokines and their receptors play fundamental roles in many physiological and pathological processes such as leukocyte trafficking, inflammation, cancer and HIV-1 infection. Chemokine-receptor interactions are particularly intricate and therefore require precise orchestration. The flexible N-terminal domain of human chemokine receptors has regularly been demonstrated to hold a crucial role in the initial recognition and selective binding of the receptor ligands. The length and the amino acid sequences of the N-termini vary considerably among different receptors but they all show a high content of negatively charged residues and are subject to post-translational modifications such as O-sulfation and N- or O-glycosylation. In addition, a conserved cysteine that is most likely engaged in a receptor-stabilizing disulfide bond delimits two functionally distinct parts in the N-terminus, characterized by specific molecular signatures. Structural analyses have shown that the N-terminus of chemokine receptors recognizes a groove on the chemokine surface and that this interaction is stabilized by high-affinity binding to a conserved sulfotyrosine-binding pocket. Altogether, these data provide new insights on the chemokine-receptor molecular interplay and identify the receptor N-terminus-binding site as a new target for the development of therapeutic molecules. This review presents and discusses the diversity and function of human chemokine receptor N-terminal domains and provides a comprehensive annotated inventory of their sequences, laying special emphasis on the presence of post-translational modifications and functional features. Finally, it identifies new molecular signatures and proposes a computational model for the positioning and the conformation of the CXCR4 N-terminus grafted on the first chemokine receptor X-ray structure.
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Affiliation(s)
- Martyna Szpakowska
- Laboratory of Retrovirology, Public Research Center for Health, Luxembourg, Luxembourg.
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11
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Rana S, Baranski TJ. Third extracellular loop (EC3)-N terminus interaction is important for seven-transmembrane domain receptor function: implications for an activation microswitch region. J Biol Chem 2010; 285:31472-83. [PMID: 20663868 DOI: 10.1074/jbc.m110.129213] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The canonical heptahelical bundle architecture of seven-transmembrane domain (7TM) receptors is intertwined by three intra- and three extracellular loops, whose local conformations are important in receptor signaling. Many 7TM receptors contain a cysteine residue in the third extracellular loop (EC3) and a complementary cysteine residue on the N terminus. The functional role of such EC3-N terminus conserved cysteine pairs remains unclear. This study explores the role of the EC3-N terminus cysteine pairs on receptor conformation and G protein activation by disrupting them in the chemokine receptor CXCR4, while engineering a novel EC3-N terminus cysteine pair into the complement factor 5a receptor (C5aR), a chemo attractant receptor that lacks it. Mutated CXCR4 and C5aRs were expressed in engineered yeast. Mutation of the cysteine pair with the serine pair (C28S/C274S) in constitutively active mutant CXCR4 abrogated the receptor activation, whereas mutation with the aromatic pair (C28F-C274F) or the salt bridge pair (C28R/C274E), respectively, rescued or retained the receptor activation in response to CXCL12. In this context, the cysteine pair (Cys(30) and Cys(272)) engineered into the EC3-N terminus (Ser(30) and Ser(272)) of a novel constitutively active mutant of C5aR restrained the constitutive signaling without affecting the C5a-induced activation. Further mutational studies demonstrated a previously unappreciated role for Ser(272) on EC3 of C5aR and its interaction with the N terminus, thus defining a new microswitch region within the C5aR. Similar results were obtained with mutated CXCR4 and C5aRs expressed in COS-7 cells. These studies demonstrate a novel role of the EC3-N terminus cysteine pairs in G protein-coupled receptor activation and signaling.
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Affiliation(s)
- Soumendra Rana
- Division of Metabolism, Endocrinology, and Lipid Research, Department of Medicine, Washington University School of Medicine, St Louis, Missouri 63110, USA
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12
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Widdison S, Siddiqui N, Easton V, Lawrence F, Ashley G, Werling D, Watson M, Coffey TJ. The bovine chemokine receptors and their mRNA abundance in mononuclear phagocytes. BMC Genomics 2010; 11:439. [PMID: 20642824 PMCID: PMC3091636 DOI: 10.1186/1471-2164-11-439] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2010] [Accepted: 07/19/2010] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND The chemokine and chemokine receptor families play critical roles in both the healthy and diseased organism mediating the migration of cells. The chemokine system is complex in that multiple chemokines can bind to one chemokine receptor and vice versa. Although chemokine receptors have been well characterised in humans, the chemokine receptor repertoire of cattle is not well characterised and many sequences are yet to be experimentally validated. RESULTS We have identified and sequenced bovine homologs to all identified functional human chemokine receptors. The bovine chemokine receptors show high levels of similarity to their human counterparts and similar genome arrangements. We have also characterised an additional bovine chemokine receptor, not present in the available genome sequence of humans or the more closely related pigs or horses. This receptor shows the highest level of similarity to CCR1 but shows significant differences in regions of the protein that are likely to be involved in ligand binding and signalling. We have also examined the mRNA abundance levels of all identified bovine chemokine receptors in mononuclear phagocytic cells. Considerable differences were observed in the mRNA abundance levels of the receptors, and interestingly the identified novel chemokine receptor showed differing levels of mRNA abundance to its closest homolog CCR1. The chemokine receptor repertoire was shown to differ between monocytes, macrophages and dendritic cells. This may reflect the differing roles of these cells in the immune response and may have functional consequences for the trafficking of these cells in vivo. CONCLUSIONS In summary, we have provided the first characterisation of the complete bovine chemokine receptor gene repertoire including a gene that is potentially unique to cattle. Further study of this receptor and its ligands may reveal a specific role of this receptor in cattle. The availability of the bovine chemokine receptor sequences will allow further characterisation of the function of these genes and will confer wide-reaching benefits to the study of this important aspect of the bovine immune response.
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Affiliation(s)
| | - Nazneen Siddiqui
- Institute for Animal Health, Compton, Newbury, Berkshire, RG20 7NN, UK
| | - Victoria Easton
- Institute for Animal Health, Compton, Newbury, Berkshire, RG20 7NN, UK
| | - Freya Lawrence
- Institute for Animal Health, Compton, Newbury, Berkshire, RG20 7NN, UK
- The Royal Veterinary College, Hawkshead Lane, North Mymms, Hatfield, Hertfordshire, AL9 7TA, UK
| | - George Ashley
- Institute for Animal Health, Compton, Newbury, Berkshire, RG20 7NN, UK
| | - Dirk Werling
- The Royal Veterinary College, Hawkshead Lane, North Mymms, Hatfield, Hertfordshire, AL9 7TA, UK
| | - Michael Watson
- Institute for Animal Health, Compton, Newbury, Berkshire, RG20 7NN, UK
| | - Tracey J Coffey
- Institute for Animal Health, Compton, Newbury, Berkshire, RG20 7NN, UK
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Rajagopalan L, Rajarathnam K. Structural basis of chemokine receptor function--a model for binding affinity and ligand selectivity. Biosci Rep 2006; 26:325-39. [PMID: 17024562 PMCID: PMC2671010 DOI: 10.1007/s10540-006-9025-9] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
Chemokine receptors play fundamental roles in human physiology from embryogenesis to inflammatory response. The receptors belong to the G-protein coupled receptor class, and are activated by chemokine ligands with a range of specificities and affinities that result in a complicated network of interactions. The molecular basis for function is largely a black box, and can be directly attributed to the lack of structural information on the receptors. Studies to date indicate that function can be best described by a two-site model, that involves interactions between the receptor N-domain and ligand N-terminal loop residues (site-I), and between receptor extracellular loop and the ligand N-terminal residues (site-II). In this review, we describe how the two-site model could modulate binding affinity and ligand selectivity, and also highlight some of the unique chemokine receptor features, and their role in function.
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Affiliation(s)
- Lavanya Rajagopalan
- Department of Biochemistry and Molecular Biology and Sealy Center for Structural Biology, The University of Texas Medical Branch, Galveston, TX 77555-1055, USA, e-mail:
| | - Krishna Rajarathnam
- Department of Biochemistry and Molecular Biology and Sealy Center for Structural Biology, The University of Texas Medical Branch, Galveston, TX 77555-1055, USA, e-mail:
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