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Santos-López J, de la Paz K, Fernández FJ, Vega MC. Structural biology of complement receptors. Front Immunol 2023; 14:1239146. [PMID: 37753090 PMCID: PMC10518620 DOI: 10.3389/fimmu.2023.1239146] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Accepted: 08/16/2023] [Indexed: 09/28/2023] Open
Abstract
The complement system plays crucial roles in a wide breadth of immune and inflammatory processes and is frequently cited as an etiological or aggravating factor in many human diseases, from asthma to cancer. Complement receptors encompass at least eight proteins from four structural classes, orchestrating complement-mediated humoral and cellular effector responses and coordinating the complex cross-talk between innate and adaptive immunity. The progressive increase in understanding of the structural features of the main complement factors, activated proteolytic fragments, and their assemblies have spurred a renewed interest in deciphering their receptor complexes. In this review, we describe what is currently known about the structural biology of the complement receptors and their complexes with natural agonists and pharmacological antagonists. We highlight the fundamental concepts and the gray areas where issues and problems have been identified, including current research gaps. We seek to offer guidance into the structural biology of the complement system as structural information underlies fundamental and therapeutic research endeavors. Finally, we also indicate what we believe are potential developments in the field.
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Affiliation(s)
- Jorge Santos-López
- Centro de Investigaciones Biológicas Margarita Salas, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | - Karla de la Paz
- Centro de Investigaciones Biológicas Margarita Salas, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
- Research & Development, Abvance Biotech SL, Madrid, Spain
| | | | - M. Cristina Vega
- Centro de Investigaciones Biológicas Margarita Salas, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
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Qu Z, Gao F, Li L, Zhang Y, Jiang Y, Yu L, Zhou Y, Zheng H, Tong W, Li G, Tong G. Label-Free Quantitative Proteomic Analysis of Differentially Expressed Membrane Proteins of Pulmonary Alveolar Macrophages Infected with Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus and Its Attenuated Strain. Proteomics 2017; 17. [PMID: 29052333 PMCID: PMC6084361 DOI: 10.1002/pmic.201700101] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Revised: 09/19/2017] [Indexed: 12/11/2022]
Abstract
Significant differences exist between the highly pathogenic (HP) porcine reproductive and respiratory syndrome virus (PRRSV) and its attenuated pathogenic (AP) strain in the ability to infect host cells. The mechanisms by which different virulent strains invade host cells remain relatively unknown. In this study, pulmonary alveolar macrophages (PAMs) are infected with HP‐PRRSV (HuN4) and AP‐PRRSV (HuN4‐F112) for 24 h, then harvested and subjected to label‐free quantitative MS. A total of 2849 proteins are identified, including 95 that are differentially expressed. Among them, 26 proteins are located on the membrane. The most differentially expressed proteins are involved in response to stimulus, metabolic process, and immune system process, which mainly have the function of binding and catalytic activity. Cluster of differentiation CD163, vimentin (VIM), and nmII as well as detected proteins are assessed together by string analysis, which elucidated a potentially different infection mechanism. According to the function annotations, PRRSV with different virulence may mainly differ in immunology, inflammation, immune evasion as well as cell apoptosis. This is the first attempt to explore the differential characteristics between HP‐PRRSV and its attenuated PRRSV infected PAMs focusing on membrane proteins which will be of great help to further understand the different infective mechanisms of HP‐PRRSV and AP‐PRRSV.
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Affiliation(s)
- Zehui Qu
- Department of Swine Infectious Diseases, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, P. R. China
| | - Fei Gao
- Department of Swine Infectious Diseases, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, P. R. China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, P. R. China
| | - Liwei Li
- Department of Swine Infectious Diseases, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, P. R. China
| | - Yujiao Zhang
- Department of Swine Infectious Diseases, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, P. R. China
| | - Yifeng Jiang
- Department of Swine Infectious Diseases, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, P. R. China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, P. R. China
| | - Lingxue Yu
- Department of Swine Infectious Diseases, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, P. R. China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, P. R. China
| | - Yanjun Zhou
- Department of Swine Infectious Diseases, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, P. R. China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, P. R. China
| | - Hao Zheng
- Department of Swine Infectious Diseases, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, P. R. China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, P. R. China
| | - Wu Tong
- Department of Swine Infectious Diseases, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, P. R. China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, P. R. China
| | - Guoxin Li
- Department of Swine Infectious Diseases, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, P. R. China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, P. R. China
| | - Guangzhi Tong
- Department of Swine Infectious Diseases, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, P. R. China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, P. R. China
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3
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Gärtner F, Seidel T, Schulz U, Gummert J, Milting H. Desensitization and internalization of endothelin receptor A: impact of G protein-coupled receptor kinase 2 (GRK2)-mediated phosphorylation. J Biol Chem 2013; 288:32138-32148. [PMID: 24064210 DOI: 10.1074/jbc.m113.461566] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Endothelin receptor A (ETA), a G protein-coupled receptor, mediates endothelin signaling, which is regulated by GRK2. Three Ser and seven Thr residues recently proven to be phosphoacceptor sites are located in the C-terminal extremity (CTE) of the receptor following its palmitoylation site. We created various phosphorylation-deficient ETA mutants. The phospholipase C activity of mutant receptors in HEK-293 cells was analyzed during continuous endothelin stimulation to investigate the impact of phosphorylation sites on ETA desensitization. Total deletion of phosphoacceptor sites in the CTE affected proper receptor regulation. However, proximal and distal phosphoacceptor sites both turned out to be sufficient to induce WT-like desensitization. Overexpression of the Gαq coupling-deficient mutant GRK2-D110A suppressed ETA-WT signaling but failed to decrease phospholipase C activity mediated by the phosphorylation-deficient mutant ETA-6PD. In contrast, GRK2-WT acted on both receptors, whereas the kinase-inactive mutant GRK2-D110A/K220R failed to inhibit signaling of ETA-WT and ETA-6PD. This demonstrates that ETA desensitization involves at least two autonomous GRK2-mediated components: 1) a phosphorylation-independent signal decrease mediated by blocking of Gαq and 2) a mechanism involving phosphorylation of Ser and Thr residues in the CTE of the receptor in a redundant fashion, able to incorporate either proximal or distal phosphoacceptor sites. High level transfection of GRK2 variants influenced signaling of ETA-WT and ETA-6PD and hints at an additional phosphorylation-independent regulatory mechanism. Furthermore, internalization of mRuby-tagged receptors was observed with ETA-WT and the phosphorylation-deficient mutant ETA-14PD (lacking 14 phosphoacceptor sites) and turned out to be based on a phosphorylation-independent mechanism.
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Affiliation(s)
- Florian Gärtner
- From the E. & H. Klessmann Institute for Cardiovascular Research & Development, Clinic of Thoracic and Cardiovascular Surgery, Heart and Diabetes Center NRW, Ruhr University Bochum, D-32545 Bad Oeynhausen
| | - Thorsten Seidel
- Dynamic Cell Imaging, Faculty of Biology, Bielefeld University, D-33501 Bielefeld, Germany
| | - Uwe Schulz
- From the E. & H. Klessmann Institute for Cardiovascular Research & Development, Clinic of Thoracic and Cardiovascular Surgery, Heart and Diabetes Center NRW, Ruhr University Bochum, D-32545 Bad Oeynhausen
| | - Jan Gummert
- From the E. & H. Klessmann Institute for Cardiovascular Research & Development, Clinic of Thoracic and Cardiovascular Surgery, Heart and Diabetes Center NRW, Ruhr University Bochum, D-32545 Bad Oeynhausen
| | - Hendrik Milting
- From the E. & H. Klessmann Institute for Cardiovascular Research & Development, Clinic of Thoracic and Cardiovascular Surgery, Heart and Diabetes Center NRW, Ruhr University Bochum, D-32545 Bad Oeynhausen.
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Singh VV, Chauhan SK, Rai R, Kumar A, Singh SM, Rai G. Decreased pattern recognition receptor signaling, interferon-signature, and bactericidal/permeability-increasing protein gene expression in cord blood of term low birth weight human newborns. PLoS One 2013; 8:e62845. [PMID: 23626859 PMCID: PMC3633842 DOI: 10.1371/journal.pone.0062845] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2012] [Accepted: 03/28/2013] [Indexed: 12/20/2022] Open
Abstract
Background Morbidity and mortality rates of low birth weight (LBW) newborns at term are higher than rates in normal birth weight (NBW) newborns. LBW newborns are at greater risk to acquire recurrent bacterial and viral infections during their first few weeks of life possibly as an outcome of compromised innate immune functions. As adaptive immunity is in a naive state, increased risk of infection of LBW as compared to NBW newborns may reflect impairments in innate immunity. Methodology To characterize the increased susceptibility to infections in LBW newborns we used microarray technology to identify differences in gene expression in LBW newborns (n = 8) compared to NBW newborns (n = 4) using cord blood. The results obtained from the microarray study were validated on a larger number of samples using real time RT-PCR (LBW = 22, NBW = 18) and western blotting (LBW = 12, NBW = 12). The Interferome database was used to identify interferon (IFN) signature genes and ingenuity pathway analysis identified canonical pathways and biological functions associated with the differentially expressed genes in LBW newborns. ELISAs for IFNs and bactericidal/permeability-increasing protein were performed in both LBW and NBW newborns and in adults (LBW = 18, NBW = 18, Adults = 8). Principal Findings Upon microarray analysis, we identified 1,391 differentially expressed genes, of which, 1,065 genes were down-regulated and 326 genes were up-regulated in the LBW compared to NBW newborns. Of note, 70 IFN-signature genes were found to be significantly down-regulated in LBW compared to NBW newborns. Ingenuity pathway analysis revealed pattern recognition receptors signaling including Toll-Like Receptors (TLRs) -1, -5, and -8 genes and IFN signaling as the most significantly impacted pathways. Respiratory infectious diseases were the most significantly affected bio-functions in LBW newborns. Conclusion and Significance Diminished PRRs, IFN-signature, and BPI gene expression raises the possibility that impairments in these pathways contribute to the susceptibility of LBW term infants to infection.
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Affiliation(s)
- Vikas Vikram Singh
- Department of Molecular and Human Genetics, Faculty of Science, Banaras Hindu University, Varanasi, India
| | - Sudhir Kumar Chauhan
- Department of Molecular and Human Genetics, Faculty of Science, Banaras Hindu University, Varanasi, India
| | - Richa Rai
- Department of Molecular and Human Genetics, Faculty of Science, Banaras Hindu University, Varanasi, India
| | - Ashok Kumar
- Department of Pediatrics, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India
| | - Shiva M. Singh
- Department of Biology, The University of Western Ontario, London, Ontario, Canada
| | - Geeta Rai
- Department of Molecular and Human Genetics, Faculty of Science, Banaras Hindu University, Varanasi, India
- * E-mail:
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Rabiet MJ, Macari L, Dahlgren C, Boulay F. N-formyl peptide receptor 3 (FPR3) departs from the homologous FPR2/ALX receptor with regard to the major processes governing chemoattractant receptor regulation, expression at the cell surface, and phosphorylation. J Biol Chem 2011; 286:26718-31. [PMID: 21543323 DOI: 10.1074/jbc.m111.244590] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Among human N-formyl peptide chemoattractant receptors, FPR2/ALX and FPR3 share the highest degree of amino acid identity (83%), and trigger similar cell responses upon ligand binding. Although FPR2/ALX is a promiscuous receptor, FPR3 has only one specific high affinity ligand, F2L, and a more restricted tissue/cell distribution. In this study, we showed that FPR2/ALX behaved as the prototypical receptor FPR1. The agonist-dependent phosphorylation used a hierarchical mechanism with a prominent role of Ser(329), Thr(332), and Thr(335). Phosphorylation of FPR2/ALX was essential for its desensitization but the lack of phosphorylation did not result in enhanced or sustained responses. In contrast, resting FPR3 displayed a marked level of phosphorylation, which was only slightly increased upon agonist stimulation. Another noticeable difference between the two receptors was their subcellular distribution in unstimulated cells. Although FPR2/ALX was evenly distributed at the plasma membrane FPR3 was localized in small intracellular vesicles. By swapping domains between FPR2/ALX and FPR3, we uncovered the determinants involved in the basal phosphorylation of FPR3. Experiments aimed at monitoring receptor-bound antibody uptake showed that the intracellular distribution of FPR3 resulted from a constitutive internalization that was independent of C terminus phosphorylation. Unexpectedly, exchanging residues 1 to 53, which encompass the N-terminal extracellular region and the first transmembrane domain, between FPR2/ALX and FPR3 switched localization of the receptors from the plasma membrane to intracellular vesicles and vice versa. A clathrin-independent, possibly caveolae-dependent, mechanism was involved in FPR3 constitutive internalization. The peculiar behavior of FPR3 most probably serves distinct physiological functions that remain largely unknown.
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Subramanian H, Kashem SW, Collington SJ, Qu H, Lambris JD, Ali H. PMX-53 as a dual CD88 antagonist and an agonist for Mas-related gene 2 (MrgX2) in human mast cells. Mol Pharmacol 2011; 79:1005-13. [PMID: 21441599 DOI: 10.1124/mol.111.071472] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Human mast cells express the G protein coupled receptor (GPCR) for C5a (CD88). Previous studies indicated that C5a could cause mast cell degranulation, at least in part, via a mechanism similar to that proposed for basic neuropeptides such as substance P, possibly involving Mas-related gene 2 (MrgX2). We therefore sought to more clearly define the receptor specificity for C5a-induced mast cell degranulation. We found that LAD2, a human mast cell line, and CD34(+) cell-derived primary mast cells express functional MrgX1 and MrgX2 but the immature human mast cell line HMC-1 does not. A potent CD88 antagonist, PMX-53 (10 nM) inhibited C5a-induced Ca(2+) mobilization in HMC-1 cells, but at higher concentrations (≥30 nM) it caused degranulation in LAD2 mast cells, CD34(+) cell-derived mast cells, and RBL-2H3 cells stably expressing MrgX2. PMX-53 did not, however, activate RBL-2H3 cells expressing MrgX1. Although C5a induced degranulation in LAD2 and CD34(+) cell-derived mast cells, it did not activate RBL-2H3 cells expressing MrgX1 or MrgX2. Replacement of Trp with Ala and Arg with dArg abolished the ability of PMX-53 to inhibit C5a-induced Ca(2+) mobilization in HMC-1 cells and to cause degranulation in RBL-2H3 cells expressing MrgX2. These findings demonstrate that C5a does not use MrgX1 or MrgX2 for mast cell degranulation. Moreover, it reveals the novel finding that PMX-53 functions as a potent CD88 antagonist and a low-affinity agonist for MrgX2. Furthermore, Trp and Arg residues are required for the ability of PMX53 to act as both a CD88 antagonist and a MrgX2 agonist.
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Affiliation(s)
- Hariharan Subramanian
- Department of Pathology, University of Pennsylvania School of Dental Medicine, Philadelphia, PA 19104-6030, USA
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Michaud J, Im DS, Hla T. Inhibitory Role of Sphingosine 1-Phosphate Receptor 2 in Macrophage Recruitment during Inflammation. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2010; 184:1475-1483. [PMID: 20042570 PMCID: PMC3068864 DOI: 10.4049/jimmunol.0901586] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/11/2023]
Abstract
Macrophage recruitment to sites of inflammation is an essential step in host defense. However, the mechanisms preventing excessive accumulation of macrophages remain relatively unknown. The lysophospholipid sphingosine 1-phosphate (S1P) promotes T and B cell egress from lymphoid organs by acting on S1P receptor 1 (S1P1R). More recently, S1P5R was shown to regulate NK cell mobilization during inflammation, raising the possibility that S1P regulates the trafficking of other leukocyte lineages. In this study, we show that S1P2R inhibits macrophage migration in vitro and that S1P2R-deficient mice have enhanced macrophage recruitment during thioglycollate peritonitis. We identify the signaling mechanisms used by S1P2R in macrophages, involving the second messenger cAMP and inhibition of Akt phosphorylation. In addition, we show that the phosphoinositide phosphatase and tensin homolog deleted on chromosome 10, which has been suggested to mediate S1P2R effects in other cell types, does not mediate S1P2R inhibition in macrophages. Our results suggest that S1P serves as a negative regulator of macrophage recruitment by inhibiting migration in these cells and identify an additional facet to the regulation of leukocyte trafficking by S1P.
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Affiliation(s)
- Jason Michaud
- Department of Cell Biology, Center for Vascular Biology, University of Connecticut Health Center, Farmington, CT 06030
| | - Dong-Soon Im
- Department of Cell Biology, Center for Vascular Biology, University of Connecticut Health Center, Farmington, CT 06030
- Laboratory of Pharmacology, College of Pharmacy, Pusan National University, Busan, Republic of Korea
| | - Timothy Hla
- Department of Cell Biology, Center for Vascular Biology, University of Connecticut Health Center, Farmington, CT 06030
- Department of Pathology and Laboratory Medicine, Center for Vascular Biology, Weill Medical College of Cornell University, New York, NY 10065
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Ali H. Regulation of human mast cell and basophil function by anaphylatoxins C3a and C5a. Immunol Lett 2009; 128:36-45. [PMID: 19895849 DOI: 10.1016/j.imlet.2009.10.007] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2009] [Revised: 10/21/2009] [Accepted: 10/23/2009] [Indexed: 12/18/2022]
Abstract
Allergic diseases such as asthma result from inappropriate immunologic responses to common environmental allergens in genetically susceptible individuals. Following allergen exposure, interaction of dendritic cells (DC) with CD4(+) T cells leads to the production of Th2 cytokines, which induce B cells to synthesize IgE molecules (sensitization phase). These IgE molecules bind to their high affinity receptors (FcvarepsilonRI) on the surface of mast cells and basophils and their subsequent cross-linking by allergen results in the release of preformed and newly synthesized mediators, which cause bronchoconstriction, lung inflammation and airway hyperresponsiveness (AHR) in asthma (effector phase). The complement components C3a and C5a levels are increased in the lungs of patients with asthma and are likely generated via the actions of both allergen and mast cell proteases. In vivo studies with rodents have shown that while C3a facilitates allergen sensitization in some models C5a inhibits this response. Despite this difference, both anaphylatoxins promote lung inflammation and AHR in vivo indicating that cells other than DC and T cells likely mediate the functional effects of C3a and C5a in asthma. This review focuses on the contribution of C3a and C5a in the pathogenesis of asthma with a particular emphasis on mast cells and basophils. It discusses the mechanisms by which anaphylatoxins activate mast cells and basophils and the associated signaling pathways via which their receptors are regulated by priming and desensitization.
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Affiliation(s)
- Hydar Ali
- Department of Pathology, University of Pennsylvania School of Dental Medicine, 240 South 40th Street, Philadelphia, PA 19104-6030, USA.
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Rabiet MJ, Huet E, Boulay F. Complement component 5a receptor oligomerization and homologous receptor down-regulation. J Biol Chem 2008; 283:31038-46. [PMID: 18772131 DOI: 10.1074/jbc.m805260200] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Most G-protein-coupled receptors (GPCRs) form di(oligo)-meric structures that constitute signaling and trafficking units and might be essential for receptor functions. Cell responses to complement C5a receptor (C5aR) are tightly controlled by receptor desensitization and internalization. To examine the implication of dimerization in C5aR regulation, we generated an NH(2)-terminally modified C5aR mutant, unable to bind C5a, and a phosphorylation-deficient mutant. Neither an intact NH(2) terminus nor the presence of COOH-terminal phosphorylation sites appeared to be required for the formation of C5aR dimers. Upon C5a stimulation, mutant receptors did not internalize when individually expressed. C5a stimulation of cells that co-expressed wild type C5aR together with either unliganded or phosphorylation-deficient mutant resulted in co-internalization of mutant receptors with C5aR. Unliganded GPCRs can be cross-phosphorylated within a heterologous receptor dimer or by second messenger-activated kinases. C5a stimulation of (32)P-labeled cells that co-expressed the unliganded mutant with either C5aR or the phosphorylation-deficient mutant did not induce phosphorylation of the unliganded mutant. We can thus postulate that, in the case of C5aR, the stimulation and phosphorylation of one monomer is enough to lead to dimer internalization. The existence and functional implication of di(oligo)mer formation may be important for an accurate C5aR down-regulation in pathological conditions.
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Affiliation(s)
- Marie-Josèphe Rabiet
- Laboratoire Biochimie et Biophysique des Systèmes Intégrés, Grenoble F-38054, France.
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Jones BW, Hinkle PM. Arrestin binds to different phosphorylated regions of the thyrotropin-releasing hormone receptor with distinct functional consequences. Mol Pharmacol 2008; 74:195-202. [PMID: 18413662 DOI: 10.1124/mol.108.045948] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Arrestin binding to agonist-occupied phosphorylated G protein-coupled receptors typically increases the affinity of agonist binding, increases resistance of receptor-bound agonist to removal with high acid/salt buffer, and leads to receptor desensitization and internalization. We tested whether thyrotropin-releasing hormone (TRH) receptors lacking phosphosites in the C-terminal tail could form stable and functional complexes with arrestin. Fibroblasts from mice lacking arrestins 2 and 3 were used to distinguish between arrestin-dependent and -independent effects. Arrestin did not promote internalization or desensitization of a receptor that had key Ser/Thr phosphosites mutated to Ala (4Ala receptor). Nevertheless, arrestin greatly increased acid/salt resistance and the affinity of 4Ala receptor for TRH. Truncation of 4Ala receptor just distal to the key phosphosites (4AlaStop receptor) abolished arrestin-dependent acid/salt resistance but not the effect of arrestin on agonist affinity. Arrestin formed stable complexes with activated wild-type and 4Ala receptors but not with 4AlaStop receptor, as measured by translocation of arrestin-green fluorescent protein to the plasma membrane or chemical cross-linking. An arrestin mutant that does not interact with clathrin and AP2 did not internalize receptor but still promoted high affinity TRH binding, acid/salt resistance, and desensitization. A sterically restricted arrestin mutant did not cause receptor internalization or desensitization but did promote acid/salt resistance and high agonist affinity. The results demonstrate that arrestin binds to proximal or distal phosphosites in the receptor tail. Arrestin binding at either site causes increased agonist affinity and acid/salt resistance, but only the proximal phosphosites evoke the necessary conformational changes in arrestin for receptor desensitization and internalization.
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Affiliation(s)
- Brian W Jones
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY 14642, USA
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11
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Role of the carboxyl terminal di-leucine in phosphorylation and internalization of C5a receptor. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2008; 1783:1261-70. [PMID: 18346468 DOI: 10.1016/j.bbamcr.2008.02.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2007] [Revised: 01/13/2008] [Accepted: 02/04/2008] [Indexed: 01/15/2023]
Abstract
The carboxyl tail of G protein-coupled receptors contains motifs that regulate receptor interactions with intracellular partners. Activation of the human neutrophil complement fragment C5a receptor (C5aR) is terminated by phosphorylation of the carboxyl tail followed by receptor internalization. In this study, we demonstrated that bulky hydrophobic residues in the membrane-proximal region of the C5aR carboxyl tail play an important role in proper structure and function of the receptor: Substitution of leucine 319 with alanine (L319A) resulted in receptor retention in the endoplasmic reticulum, whereas a L318A substitution allowed receptor transport to the cell surface, but showed slow internalization upon activation, presumably due to a defect in phosphorylation by both PKC and GRK. Normal agonist-induced activation of ERK1/2 and intracellular calcium release suggested that the L318A mutation did not affect receptor signaling. Binding of GRK2 and PKCbetaII to intracellular loop 3 of C5aR in vitro indicated that mutagenesis of L318 did not affect kinase binding. Limited proteolysis with trypsin revealed a conformational difference between wild type and mutant receptor. Our studies support a model in which the L318/L319 stabilizes an amphipathic helix (Q305-R320) in the membrane-proximal region of C5aR.
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12
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Monk PN, Scola AM, Madala P, Fairlie DP. Function, structure and therapeutic potential of complement C5a receptors. Br J Pharmacol 2007; 152:429-48. [PMID: 17603557 PMCID: PMC2050825 DOI: 10.1038/sj.bjp.0707332] [Citation(s) in RCA: 296] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Complement fragment (C)5a is a 74 residue pro-inflammatory polypeptide produced during activation of the complement cascade of serum proteins in response to foreign surfaces such as microorganisms and tissue damaged by physical or chemical injury. C5a binds to at least two seven-transmembrane domain receptors, C5aR (C5R1, CD88) and C5L2 (gpr77), expressed ubiquitously on a wide variety of cells but particularly on the surface of immune cells like macrophages, neutrophils and T cells. C5aR is a classical G protein-coupled receptor that signals through G alpha i and G alpha 16, whereas C5L2 does not appear to couple to G proteins and has no known signalling activity. Although C5a was first described as an anaphylatoxin and later as a leukocyte chemoattractant, the widespread expression of C5aR suggested more general functionality. Our understanding of the physiology of C5a has improved significantly in recent years through exploitation of receptor knockout and knocking mice, C5 and C5a antibodies, soluble recombinant C5a and C5a analogues and newly developed receptor antagonists. C5a is now also implicated in non-immunological functions associated with developmental biology, CNS development and neurodegeneration, tissue regeneration, and haematopoiesis. Combined receptor mutagenesis, molecular modelling, structure-activity relationship studies and species dependence for ligand potency on C5aR have been helpful for identifying ligand binding sites on the receptor and for defining mechanisms of receptor activation and inactivation. This review will highlight major developments in C5a receptor research that support C5aR as an important therapeutic target. The intriguing possibilities raised by the existence of a non-signalling C5a receptor are also discussed.
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Affiliation(s)
- P N Monk
- Academic Neurology Unit, School of Medicine and Biomedical Science, University of Sheffield, Sheffield, UK.
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13
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Maurya MR, Subramaniam S. A kinetic model for calcium dynamics in RAW 264.7 cells: 1. Mechanisms, parameters, and subpopulational variability. Biophys J 2007; 93:709-28. [PMID: 17483174 PMCID: PMC1913151 DOI: 10.1529/biophysj.106.097469] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Calcium (Ca(2+)) is an important second messenger and has been the subject of numerous experimental measurements and mechanistic studies in intracellular signaling. Calcium profile can also serve as a useful cellular phenotype. Kinetic models of calcium dynamics provide quantitative insights into the calcium signaling networks. We report here the development of a complex kinetic model for calcium dynamics in RAW 264.7 cells stimulated by the C5a ligand. The model is developed using the vast number of measurements of in vivo calcium dynamics carried out in the Alliance for Cellular Signaling (AfCS) Laboratories. Ligand binding, phospholipase C-beta (PLC-beta) activation, inositol 1,4,5-trisphosphate (IP(3)) receptor (IP(3)R) dynamics, and calcium exchange with mitochondria and extracellular matrix have all been incorporated into the model. The experimental data include data from both native and knockdown cell lines. Subpopulational variability in measurements is addressed by allowing nonkinetic parameters to vary across datasets. The model predicts temporal response of Ca(2+) concentration for various doses of C5a under different initial conditions. The optimized parameters for IP(3)R dynamics are in agreement with the legacy data. Further, the half-maximal effect concentration of C5a and the predicted dose response are comparable to those seen in AfCS measurements. Sensitivity analysis shows that the model is robust to parametric perturbations.
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Affiliation(s)
- Mano Ram Maurya
- Department of Bioengineering, University of California, San Diego, California 92093-0412, USA
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14
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Maurya MR, Subramaniam S. A kinetic model for calcium dynamics in RAW 264.7 cells: 2. Knockdown response and long-term response. Biophys J 2007; 93:729-40. [PMID: 17483189 PMCID: PMC1913159 DOI: 10.1529/biophysj.106.097501] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
This article addresses how quantitative models such as the one proposed in the companion article can be used to study cellular network perturbations such as knockdowns and pharmacological perturbations in a predictive manner. Using the kinetic model for cytosolic calcium dynamics in RAW 264.7 cells developed in the companion article, the calcium response to complement 5a (C5a) for the knockdown of seven proteins (C5a receptor; G-beta-2; G-alpha,i-2,3; regulator of G-protein signaling-10; G-protein coupled receptor kinase-2; phospholipase C beta-3; arrestin) is predicted and validated against the data from the Alliance for Cellular Signaling. The knockdown responses provide insights into how altered expressions of important proteins in disease states result in intermediate measurable phenotypes. Long-term response and long-term dose response have also been predicted, providing insights into how the receptor desensitization, internalization, and recycle result in tolerance. Sensitivity analysis of long-term response shows that the mechanisms and parameters in the receptor recycle path are important for long-term calcium dynamics.
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Affiliation(s)
- Mano Ram Maurya
- Department of Bioengineering, University of California, San Diego, La Jolla, California 92093, USA
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15
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Rabiet MJ, Huet E, Boulay F. The N-formyl peptide receptors and the anaphylatoxin C5a receptors: an overview. Biochimie 2007; 89:1089-106. [PMID: 17428601 PMCID: PMC7115771 DOI: 10.1016/j.biochi.2007.02.015] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2006] [Accepted: 02/23/2007] [Indexed: 12/31/2022]
Abstract
Leukocyte recruitment to sites of inflammation and infection is dependent on the presence of a gradient of locally produced chemotactic factors. This review is focused on current knowledge about the activation and regulation of chemoattractant receptors. Emphasis is placed on the members of the N-formyl peptide receptor family, namely FPR (N-formyl peptide receptor), FPRL1 (FPR like-1) and FPRL2 (FPR like-2), and the complement fragment C5a receptors (C5aR and C5L2). Upon chemoattractant binding, the receptors transduce an activation signal through a G protein-dependent pathway, leading to biochemical responses that contribute to physiological defense against bacterial infection and tissue damage. C5aR, and the members of the FPR family that were previously thought to be restricted to phagocytes proved to have a much broader spectrum of cell expression. In addition to N-formylated peptides, numerous unrelated ligands were recently found to interact with FPR and FPRL1. Novel agonists include both pathogen- and host-derived components, and synthetic peptides. Antagonistic molecules have been identified that exhibit limited receptor specificity. How distinct ligands can both induce different biological responses and produce different modes of receptor activation and unique sets of cellular responses are discussed. Cell responses to chemoattractants are tightly regulated at the level of the receptors. This review describes in detail the regulation of receptor signalling and the multi-step process of receptor inactivation. New concepts, such as receptor oligomerization and receptor clustering, are considered. Although FPR, FPRL1 and C5aR trigger similar biological functions and undergo a rapid chemoattractant-mediated phosphorylation, they appear to be differentially regulated and experience different intracellular fates.
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Affiliation(s)
| | | | - François Boulay
- Corresponding author. Tel.: +33 438 78 31 38; fax: +33 438 78 51 85.
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16
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Pollok-Kopp B, Hüttenrauch F, Rethorn S, Oppermann M. Dynamics of protein kinase C-mediated phosphorylation of the complement C5a receptor on serine 334. J Biol Chem 2006; 282:4345-4353. [PMID: 17145764 DOI: 10.1074/jbc.m601317200] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Upon agonist binding, the C5a anaphylatoxin receptor (C5aR) is rapidly phosphorylated on phosphorylation sites that are located within the C-terminal domain of the receptor. Previous studies suggested that C5aR phosphorylation proceeds in a hierarchical manner with serine 334 presenting a highly accessible priming site that controls subsequent phosphorylation at other positions. To better understand the dynamics of Ser-334 phosphorylation, we generated site-specific monoclonal antibodies that specifically react with phosphoserine 334. In differentiated U937 cells, which endogenously express C5aR, stimulation with low C5a concentrations resulted in a very rapid (t((1/2)) approximately 20 s), albeit transient, receptor phosphorylation. Whole cell phosphorylation assays with specific inhibitors as well as in vitro phosphorylation assays with recombinant enzymes and peptide substrates revealed that phosphorylation of Ser-334 is regulated by protein kinase C-beta and a calyculin A-sensitive protein phosphatase. Surprisingly, at high concentrations (>10 nM) of C5a, the protein kinase C-mediated phosphorylation of Ser-334 was essentially blocked. This could be attributed to the even faster (t((1/2)) < 5 s) binding of beta-arrestin to the receptor. Analysis of C5aR Ser/Ala mutants that possess a single intact serine residue either at position 334 or at neighboring positions 327, 332, or 338 revealed functional redundancy of C-terminal phosphorylation sites since all 4 serine residues could individually support C5aR internalization and desensitization. This study is among the first to analyze in a detailed manner, using a non-mutational approach, modifications of a defined phosphorylation site in a G protein-coupled receptor and to correlate these findings with functional parameters of receptor deactivation.
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Affiliation(s)
- Beatrix Pollok-Kopp
- Department of Cellular and Molecular Immunology, Georg-August-University, 37073 Göttingen, Germany
| | - Friederike Hüttenrauch
- Department of Cellular and Molecular Immunology, Georg-August-University, 37073 Göttingen, Germany
| | - Stephanie Rethorn
- Department of Cellular and Molecular Immunology, Georg-August-University, 37073 Göttingen, Germany
| | - Martin Oppermann
- Department of Cellular and Molecular Immunology, Georg-August-University, 37073 Göttingen, Germany.
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17
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Matsumoto ML, Narzinski K, Kiser PD, Nikiforovich GV, Baranski TJ. A comprehensive structure-function map of the intracellular surface of the human C5a receptor. I. Identification of critical residues. J Biol Chem 2006; 282:3105-21. [PMID: 17135254 DOI: 10.1074/jbc.m607679200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
G protein-coupled receptors are one of the largest protein families in nature; however, the mechanisms by which they activate G proteins are still poorly understood. To identify residues on the intracellular face of the human C5a receptor that are involved in G protein activation, we performed a genetic analysis of each of the three intracellular loops and the carboxyl-terminal tail of the receptor. Amino acid substitutions were randomly incorporated into each loop, and functional receptors were identified in yeast. The third intracellular loop contains the largest number of preserved residues (positions resistant to amino acid substitutions), followed by the second loop, the first loop, and lastly the carboxyl terminus. Surprisingly, complete removal of the carboxyl-terminal tail did not impair C5a receptor signaling. When mapped onto a three-dimensional structural model of the inactive state of the C5a receptor, the preserved residues reside on one half of the intracellular surface of the receptor, creating a potential activation face. Together these data provide one of the most comprehensive functional maps of the intracellular surface of any G protein-coupled receptor to date.
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Affiliation(s)
- Marissa L Matsumoto
- Department of Medicine and Molecular Biology, Washington School of Medicine, Missouri 63110, USA
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18
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Hüttenrauch F, Pollok-Kopp B, Oppermann M. G protein-coupled receptor kinases promote phosphorylation and beta-arrestin-mediated internalization of CCR5 homo- and hetero-oligomers. J Biol Chem 2005; 280:37503-15. [PMID: 16144840 DOI: 10.1074/jbc.m500535200] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Expression levels of the chemokine receptor, CC chemokine receptor 5 (CCR5), at the cell surface determine cell susceptibility to HIV entry and infection. Cellular activation by CCR5 itself, but also by unrelated receptors leads to cross-phosphorylation and cross-internalization of CCR5. This study addresses the underlying molecular mechanisms of homologous and heterologous CCR5 regulation. As shown by bioluminescence resonance energy transfer experiments, CCR5 formed constitutive homo- as well as heterooligomeric complexes together with C5aR but not with the unrelated AT(1a)R in living cells. Stimulation with CCL5 of RBL cells, which co-expressed CCR5 together with an N-terminally truncated CCR5-DeltaNT mutant, resulted in both protein kinase C (PKC)- and G protein-coupled receptor (GPCR) kinase (GRK)-mediated cross-phosphorylation of the mutant unligated receptor, as determined by phosphosite-specific monoclonal antibody. Similarly, both PKC and GRK cross-phosphorylated CCR5 in a heterologous manner after C5a stimulation of RBL-CCR5/C5aR cells, whereas AT(1a)R stimulation resulted only in classical PKC-mediated CCR5 phosphorylation. Co-expression of CCR5-DeltaNT together with a phosphorylation-deficient CCR5 mutant that neither binds beta-arrestin nor undergoes internalization partially restored the CCL5-induced association of beta-arrestin with the homo-oligomeric receptor complex and augmented cellular uptake of (125)I-CCL5. Co-expression of C5aR, but not of AT(1a)R, promoted CCR5 co-internalization upon agonist stimulation by a mechanism independent of CCR5 phosphorylation. Co-internalization of phosphorylated CCR5 was also observed in C5a-stimulated macrophages. Finally, co-expression of a constitutively internalized C5aR-US28(CT) mutant led to intracellular accumulation of CCR5 in the absence of ligand stimulation. These results show that GRKs and beta-arrestin are involved in heterologous receptor regulation by cross-phosphorylating and co-internalizing unligated receptors within homo- or hetero-oligomeric protein complexes.
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Affiliation(s)
- Friederike Hüttenrauch
- Department of Cellular and Molecular Immunology, Georg-August-University, Göttingen, Germany
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19
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Auger GA, Smith BM, Pease JE, Barker MD. The use of membrane translocating peptides to identify sites of interaction between the C5a receptor and downstream effector proteins. Immunology 2004; 112:590-6. [PMID: 15270730 PMCID: PMC1782523 DOI: 10.1111/j.1365-2567.2004.01919.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The complement fragment C5a is a potent leucocyte chemoattractant and activator, mediating its effects through a G-protein-coupled receptor. Whilst the C-terminal domain of this receptor has been shown to be essential for receptor desensitization and internalization, it is not known which domains couple to the receptor's heterotrimeric G proteins. In this report we have used a membrane translocating sequence (MTS) to examine the effects of the four intracellular domains of the human C5a receptor (C5aR) on the receptor's signalling via G(alphai) family heterotrimeric G proteins in intact RBL-2H3 cells. The results indicate that all of the intracellular domains couple to downstream signalling, with the proximal region of the C terminus being a major binding site and intracellular loop 3 playing a role in G protein activation or receptor desensitization.
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Affiliation(s)
- Graham A Auger
- Division of Genomic Medicine, The University of Sheffield, Sheffield, UK
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20
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Fu H, Bylund J, Karlsson A, Pellmé S, Dahlgren C. The mechanism for activation of the neutrophil NADPH-oxidase by the peptides formyl-Met-Leu-Phe and Trp-Lys-Tyr-Met-Val-Met differs from that for interleukin-8. Immunology 2004; 112:201-10. [PMID: 15147563 PMCID: PMC1782485 DOI: 10.1111/j.1365-2567.2004.01884.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Neutrophil chemotaxis has been shown to be regulated by two different signalling pathways that allow strong chemoattractants, such as bacterial-derived formylated peptides, to dominate over endogenous attractants, such as interleukin-8 (IL-8). Here we show that triggering of the formyl peptide receptor (FPR) with f-Met-Leu-Phe (fMLF) substantially reduced the neutrophil superoxide production induced by activation of the CXC receptors with IL-8. When the order of agonists was reversed, the cells were primed in their response to fMLF, suggesting that the signalling hierarchy between strong, so-called end-type (i.e. fMLF) and weak or intermediate-type (i.e. IL-8) chemoattractants, is also operating during activation of the NADPH-oxidase. The same result was obtained when fMLF was replaced with the hexapeptide, WKYMVM, specific for the formyl peptide-like receptor 1 (FPRL1). There were additional differences between the agonist receptor pairs fMLF/FPR, WKYMVM/FPRL1 and IL-8/CXCR. In contrast to FPR and FPRL1, no reserve pool of CXCR was present in subcellular granules and it was impossible to prime the oxidative response transduced through CXCR by the addition of priming agents such as tumour necrosis factor-alpha and platelet-activating factor. Moreover, the cytoskeleton-disrupting substance, cytochalasin B, had no effect either on IL-8-triggered oxidase activation or on CXCR reactivation. A pertussis toxin-sensitive G-protein is involved in signalling mediated through both FPR and CXCR, and the signalling cascades include a transient intracellular calcium increase, as well as downstream p38 MAPK and phosphoinositide 3-kinase activation. The data presented in this study provide support for two different signalling pathways to the neutrophil NADPH-oxidase, used by ligand binding to FPR/FPRL1 or CXCR, respectively.
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Affiliation(s)
- Huamei Fu
- Department of Rheumatology and Inflammation Research, University of Göteborg, Göteborg, Sweden.
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21
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Bylund J, Björstad A, Granfeldt D, Karlsson A, Woschnagg C, Dahlgren C. Reactivation of formyl peptide receptors triggers the neutrophil NADPH-oxidase but not a transient rise in intracellular calcium. J Biol Chem 2003; 278:30578-86. [PMID: 12773548 DOI: 10.1074/jbc.m209202200] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
In neutrophils, coupling of chemoattractants to their cell surface receptor at low temperature (<or=15 degrees C) leads to receptor deactivation/desensitization without any triggering of the superoxide anion-generating NADPH-oxidase. We show that the deactivated formyl peptide receptors (FPRs) can be reactivated/resensitized by the cytoskeleton-disrupting drug cytochalasin B. Such cytoskeleton-dependent receptor reactivation occurs also with the closely related receptors FPR-like-1 and C5aR but not with the receptors for interleukin-8 and platelet-activating factor. The reactivation state was further characterized with FPR as a model. The signals generated by receptor reactivation induced superoxide production that was terminated in 5-8 min, after which the neutrophils entered a new state of homologous deactivation. FPR antagonists were potent inhibitors of the superoxide production induced by the reactivated receptors, suggesting that the occupied receptors turn into an actively signaling state when the cytoskeleton is disrupted. The signals generated by the reactivated receptor were pertussis toxin-sensitive, indicating involvement of a G-protein. However, no transient elevation of intracellular Ca2+ accompanies the NADPH-oxidase activation. This was not due to a general down-regulation of phospholipase C/Ca2+ signaling, and despite the fact that no intracellular Ca2+ transient was generated, protein kinase C still appeared to be involved in the response. Further, phosphatidylinositol 3-kinase, mitogen-activated protein kinase, and MEK all participated in the generation of second messengers from the reactivated receptors.
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MESH Headings
- Androstadienes/pharmacology
- Antigens, CD/chemistry
- Antigens, CD/metabolism
- Calcium/metabolism
- Cytochalasin B/pharmacology
- Cytoskeleton/drug effects
- Cytoskeleton/enzymology
- Enzyme Activation/drug effects
- Enzyme Activation/physiology
- Enzyme Inhibitors/pharmacology
- GTP-Binding Proteins/metabolism
- HL-60 Cells
- Humans
- NADPH Oxidases/metabolism
- Neutrophils/enzymology
- Platelet Membrane Glycoproteins/chemistry
- Platelet Membrane Glycoproteins/metabolism
- Protein Structure, Tertiary
- Receptor, Anaphylatoxin C5a
- Receptors, Cell Surface/chemistry
- Receptors, Cell Surface/metabolism
- Receptors, Complement/chemistry
- Receptors, Complement/metabolism
- Receptors, Formyl Peptide
- Receptors, G-Protein-Coupled
- Receptors, Immunologic/chemistry
- Receptors, Immunologic/metabolism
- Receptors, Interleukin-8A/chemistry
- Receptors, Interleukin-8A/metabolism
- Receptors, Interleukin-8B/chemistry
- Receptors, Interleukin-8B/metabolism
- Receptors, Peptide/chemistry
- Receptors, Peptide/metabolism
- Signal Transduction/drug effects
- Signal Transduction/physiology
- Wortmannin
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Affiliation(s)
- Johan Bylund
- Department of Rheumatology and Inflammation Research, University of Göteborg, Guldhedsgatan 10, S-413 46 Göteborg, Sweden
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22
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Tardif M, Brouchon L, Rabiet MJ, Boulay F. Direct binding of a fragment of the Wiskott-Aldrich syndrome protein to the C-terminal end of the anaphylatoxin C5a receptor. Biochem J 2003; 372:453-63. [PMID: 12600272 PMCID: PMC1223397 DOI: 10.1042/bj20021803] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2002] [Revised: 02/20/2003] [Accepted: 02/25/2003] [Indexed: 11/17/2022]
Abstract
Migration of myeloid cells towards a source of chemoattractant, such as the C5a anaphylatoxin, is triggered by the activation of a G-protein-coupled receptor. In the present study, we have used a yeast two-hybrid approach to find unknown partners of the C5a receptor (C5aR). Using the cytosolic C-terminal region of C5aR as bait to screen a human leucocyte cDNA library, we identified the Wiskott-Aldrich syndrome protein (WASP) as a potential partner of C5aR. WASP is known to have an essential function in regulating actin dynamics at the cell leading edge. The interaction was detected with both the fragment of WASP containing amino acids 1-321 (WASP.321) and WASP with its actin-nucleation-promoting domain [verprolin-like, central and acidic (VCA) domain] deleted. The interaction between C5aR and the WASP.321 was supported further by an in vitro binding assay between a radiolabelled WASP.321 fragment and a receptor C-terminus glutathione S-transferase (GST) fusion protein, as well as by GST pull-down, co-immunoprecipitation and immunofluorescence experiments. In the yeast two-hybrid assay, full-length WASP showed no ability to interact with the C-terminal domain of C5aR. This is most probably due to an auto-inhibited conformation imposed by the VCA domain. In HEK-293T cells co-transfected with full-length WASP and C5aR, only a small amount of WASP was co-precipitated with the receptor. However, in the presence of the active form of the GTPase Cdc42 (Cdc42V12), which is thought to switch WASP to an active 'open conformation', the amount of WASP associated with the receptor was markedly increased. We hypothesize that a transient interaction between C5aR and WASP occurs following the stimulation of C5aR and Cdc42 activation. This might be one mechanism by which WASP is targeted to the plasma membrane and by which actin assembly is spatially controlled in cells moving in a gradient of C5a.
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Affiliation(s)
- Marianne Tardif
- Laboratoire de Biochimie et Biophysique des Systèmes Intégrés, Commissariat à l'Energie Atomique (CEA)/Centre National de la Recherche Scientifique (CNRS)/Université Joseph Fourier, CEA-Grenoble, France.
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23
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Braun L, Christophe T, Boulay F. Phosphorylation of key serine residues is required for internalization of the complement 5a (C5a) anaphylatoxin receptor via a beta-arrestin, dynamin, and clathrin-dependent pathway. J Biol Chem 2003; 278:4277-85. [PMID: 12464600 DOI: 10.1074/jbc.m210120200] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The human complement 5a (C5a) anaphylatoxin receptor (CD88) is a G protein-coupled receptor involved in innate host defense and inflammation. Upon agonist binding, C5a receptor (C5aR) undergoes rapid phosphorylation on the six serine residues present in the C-terminal region followed by desensitization and internalization. Using confocal immunofluorescence microscopy and green fluorescent protein-tagged beta-arrestins (beta-arr 1- and beta-arr 2-EGFP) we show a persistent complex between C5aR and beta-arrestins to endosomal compartments. Serine residues in the C5aR C terminus were identified that control the intracellular trafficking of the C5aR-arrestin complex in response to C5a. Two phosphorylation mutants C5aR-A(314,317,327,332) and C5aR-A(314,317,332,334), which are phosphorylated only on Ser(334)/Ser(338) and Ser(327)/Ser(338), respectively, recruited beta-arr 1 and were internalized. In contrast, the phosphorylation-deficient receptors C5aR-A(334,338) and C5aR-A(332,334,338) were not internalized even though observations by confocal microscopy indicated that beta-arr 1-EGFP and/or beta-arr 2-EGFP could be recruited to the plasma membrane. Altogether the results indicate that C5aR activation is able to promote a loose association with beta-arrestins, but phosphorylation of either Ser(334)/Ser(338) or Ser(327)/Ser(338) is necessary and sufficient for the formation of a persistent complex. In addition, it was observed that C5aR endocytosis was inhibited by the expression of the dominant negative mutants of dynamin (K44E) and beta-arrestin 1 (beta-arr 1-(319-418)-EGFP). Thus, the results suggest that the C5aR is internalized via a pathway dependent on beta-arrestin, clathrin, and dynamin.
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Affiliation(s)
- Laurence Braun
- Département de Réponse et Dynamique Cellulaires/Biochimie et Biophysique des Systèmes Intégrés, (UMR 5092, Commissariat à l'Energie Atomique (CEA)/CNRS/Université Joseph Fourier), CEA/Grenoble, 17 rue des Martyrs, France
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24
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Svensson L, Dahlgren C, Wennerås C. The chemoattractant Trp‐Lys‐Tyr‐Met‐Val‐D‐Met activates eosinophils through the formyl peptide receptor and one of its homologues, formyl peptide receptor‐like 1. J Leukoc Biol 2002. [DOI: 10.1189/jlb.72.4.810] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- Lena Svensson
- Department of Clinical Bacteriology, Sahlgrenska University Hospital, Göteborg, Sweden; and
| | - Claes Dahlgren
- Department of Rheumatology and Inflammation Research, Göteborg University, Sweden
| | - Christine Wennerås
- Department of Clinical Bacteriology, Sahlgrenska University Hospital, Göteborg, Sweden; and
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25
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Huber-Lang MS, Younkin EM, Sarma JV, McGuire SR, Lu KT, Guo RF, Padgaonkar VA, Curnutte JT, Erickson R, Ward PA. Complement-induced impairment of innate immunity during sepsis. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2002; 169:3223-31. [PMID: 12218141 DOI: 10.4049/jimmunol.169.6.3223] [Citation(s) in RCA: 139] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
This study defines the molecular basis for defects in innate immunity involving neutrophils during cecal ligation/puncture (CLP)-induced sepsis in rats. Blood neutrophils from CLP rats demonstrated defective phagocytosis and defective assembly of NADPH oxidase, the latter being due to the inability of p47(phox) to translocate from the cytosol to the cell membrane of neutrophils after cell stimulation by phorbol ester (PMA). The appearance of these defects was prevented by in vivo blockade of C5a in CLP rats. In vitro exposure of neutrophils to C5a led to reduced surface expression of C5aR and defective assembly of NADPH oxidase, as defined by failure in phosphorylation of p47(phox) and its translocation to the cell membrane, together with failure in phosphorylation of p42/p44 mitogen-activated protein kinases. These data identify a molecular basis for defective innate immunity involving neutrophils during sepsis.
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Affiliation(s)
- Markus S Huber-Lang
- Department of Pathology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
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26
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Rabiet MJ, Tardif M, Braun L, Boulay F. Inhibitory effects of a dominant-interfering form of the Rho-GTPase Cdc42 in the chemoattractant-elicited signaling pathways leading to NADPH oxidase activation in differentiated HL-60 cells. Blood 2002; 100:1835-44. [PMID: 12176907 DOI: 10.1182/blood-2001-12-0193] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A tetracycline-controlled expression system was adapted to the human promyelocytic HL-60 cell line by placement of the transactivator (tTA-off) sequence under the control of the human EF-1alpha promoter region. Constitutively active and dominant-inhibitory forms of Cdc42 (Cdc42V12 and Cdc42N17, respectively) were conditionally expressed in this system. The expression of Cdc42V12 had no marked effect on chemoattractant-mediated superoxide production, corroborating previous results indicating that the guanosine 5'-triphosphate (GTP)-bound form of Cdc42 is ineffective in directly activating nicotinamide adenine dinucleotide phosphate (NADPH) oxidase in a cell-free system. However, the N17 mutant potently inhibited chemoattractant-induced superoxide production. The expression of Cdc42N17 interfered with the GTP-loading of Rac and Ras and with the activation of the MAP-kinase pathway. A drastic reduction of chemoattractant-induced inositol-1,4,5-trisphosphate formation and calcium mobilization was observed, corroborating previous in vitro study results identifying PLCbeta2 as a Rac/Cdc42 effector. Cdc42N17 was also found to inhibit the translocation of Ras-GRF2, a guanine nucleotide exchange factor for Ras and Rac but not for Cdc42. Thus, the dominant-inhibitory mutant Cdc42N17 was found to interfere at multiple levels in the signaling pathways. The pleiotropic inhibitory effects of Cdc42N17 illustrate the potential pitfalls of using dominant-inhibitory proteins to study the function of Ras-family GTPases. In this regard, a number of conclusions drawn from the use of dominant-inhibitory mutants in myeloid cells might have to be reconsidered.
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Affiliation(s)
- Marie-Josèphe Rabiet
- Département Réponse et Dynamique Cellulaires/Biochimie et Biophysique des Systèmes Intégrés, Grenoble, France.
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27
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Huttenrauch F, Nitzki A, Lin FT, Höning S, Oppermann M. Beta-arrestin binding to CC chemokine receptor 5 requires multiple C-terminal receptor phosphorylation sites and involves a conserved Asp-Arg-Tyr sequence motif. J Biol Chem 2002; 277:30769-77. [PMID: 12065593 DOI: 10.1074/jbc.m204033200] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Agonist binding to the CC chemokine receptor 5 (CCR5) induces the phosphorylation of four distinct serine residues that are located in the CCR5 C terminus. We established a series of clonal RBL-2H3 cell lines expressing CCR5 with alanine mutations of Ser(336), Ser(337), Ser(342), and Ser(349) in various combinations and explored the significance of phosphorylation sites for the ability of the receptor to interact with beta-arrestins and to undergo desensitization and internalization upon ligand binding. Receptor mutants that lack any two phosphorylation sites retained their ability to recruit endogenous beta-arrestins to the cell membrane and were normally sequestered, whereas alanine mutation of any three C-terminal serine residues abolished both beta-arrestin binding and rapid agonist-induced internalization. In contrast, RANTES (regulated on activation normal T cell expressed and secreted) stimulation of a S336A/S349A mutant triggered a sustained calcium response and enhanced granular enzyme release. This mutational analysis implies that CCR5 internalization largely depends on a beta-arrestin-mediated mechanism that requires the presence of any two phosphorylation sites, whereas receptor desensitization is independently regulated by the phosphorylation of distinct serine residues. Surface plasmon resonance analysis further demonstrated that purified beta-arrestin 1 binds to phosphorylated and nonphosphorylated C-tail peptides with similar affinities, suggesting that beta-arrestins use additional receptor sites to discriminate between nonactivated and activated receptors. Surface plasmon resonance analysis revealed beta-arrestin 1 binding to the second intracellular loop of CCR5, which required an intact Asp-Arg-Tyr triplet. These results suggest that a conserved sequence motif within the second intracellular loop of CCR5 that is known to be involved in G protein activation plays a significant role in beta-arrestin binding to CCR5.
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Affiliation(s)
- Friederike Huttenrauch
- Department of Immunology, University of Göttingen, Kreuzbergring 57, 37075 Göttingen, Germany
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28
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Tawfeek HAW, Qian F, Abou-Samra AB. Phosphorylation of the receptor for PTH and PTHrP is required for internalization and regulates receptor signaling. Mol Endocrinol 2002; 16:1-13. [PMID: 11773434 DOI: 10.1210/mend.16.1.0760] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
We have previously shown that agonist-dependent phosphorylation of the PTH/PTHrP receptor occurs on its carboxyl-terminal tail. Using site-directed mutagenesis, phosphopeptide mapping, and direct sequencing of cyanogen bromide-cleaved fragments of phosphoreceptors, we report here that PTH-dependent phosphorylation occurs on the serine residues at positions 491, 492, 493, 495, 501, and 504, and that the serine residue at position 489 is required for phosphorylation. When these seven sites were mutated to alanine residues, the mutant receptor was no longer phosphorylated after PTH stimulation. The phosphorylation-deficient receptor, stably expressed in LLCPK-1 cells, was impaired in PTH-dependent internalization and showed an increased sensitivity to PTH stimulation; the EC(50) for PTH-stimulated cAMP accumulation was decreased by 7-fold. Furthermore, PTH stimulation of the phosphorylation-deficient PTH/PTHrP receptor caused a sustained elevation in intracellular cAMP levels. These data indicate that agonist-dependent phosphorylation of the PTH/PTHrP receptor plays an important role in receptor function.
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Affiliation(s)
- Hesham A W Tawfeek
- Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA
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29
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Bennett TA, Foutz TD, Gurevich VV, Sklar LA, Prossnitz ER. Partial phosphorylation of the N-formyl peptide receptor inhibits G protein association independent of arrestin binding. J Biol Chem 2001; 276:49195-203. [PMID: 11602585 DOI: 10.1074/jbc.m106414200] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
It is now well accepted that G protein-coupled receptors activated by agonist binding become targets for phosphorylation, leading to desensitization of the receptor. Using a series of phosphorylation deficient mutants of the N-formyl peptide receptor (FPR), we have explored the role of phosphorylation on the ability of the receptor to interact with G proteins and arrestins. Using a fluorometric assay in conjunction with solubilized receptors, we demonstrate that phosphorylation of the wild type FPR lowers its affinity for G protein, whereas mutant receptors lacking four potential phosphorylation sites retain their ability to couple to G protein. Phosphorylated mutant receptors lacking only two potential phosphorylation sites are again unable to couple to G protein. Furthermore, whereas stimulated wild type FPR in whole cells colocalizes with arrestin-2, and the solubilized, phosphorylated FPR binds arrestin-2, the stimulated receptors lacking four potential phosphorylation sites display no interaction with arrestin-2. However, the mutant receptors lacking only two potential phosphorylation sites are restored in their ability to bind and colocalize with arrestin-2. Thus, there is a submaximal threshold of FPR phosphorylation that simultaneously results in an inhibition of G protein binding and an induction of arrestin binding. These results are the first to demonstrate that less than maximal levels of receptor phosphorylation can block G protein binding, independent of arrestin binding. We therefore propose that phosphorylation alone may be sufficient to desensitize the FPR in vivo, raising the possibility that for certain G protein-coupled receptors, desensitization may not be the primary function of arrestin.
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MESH Headings
- Amino Acid Sequence
- Animals
- Arrestin/metabolism
- Cell Line
- Cell Membrane/chemistry
- Cell Membrane/metabolism
- GTP-Binding Proteins/metabolism
- Humans
- Microscopy, Fluorescence
- Models, Biological
- Molecular Sequence Data
- Phosphorylation
- Protein Binding
- Protein Structure, Tertiary
- Receptors, Formyl Peptide
- Receptors, Immunologic/chemistry
- Receptors, Immunologic/genetics
- Receptors, Immunologic/metabolism
- Receptors, Peptide/chemistry
- Receptors, Peptide/genetics
- Receptors, Peptide/metabolism
- Spectrometry, Fluorescence/methods
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Affiliation(s)
- T A Bennett
- Department of Cell Biology and Physiology, Cancer Research and Treatment Center, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131, USA
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30
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Kraft K, Olbrich H, Majoul I, Mack M, Proudfoot A, Oppermann M. Characterization of sequence determinants within the carboxyl-terminal domain of chemokine receptor CCR5 that regulate signaling and receptor internalization. J Biol Chem 2001; 276:34408-18. [PMID: 11448957 DOI: 10.1074/jbc.m102782200] [Citation(s) in RCA: 125] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The CC chemokine receptor CCR5 mediates chemotaxis of leukocytes and serves as a principal co-receptor for macrophage-tropic human immunodeficiency virus type 1. To identify determinants on the CCR5 carboxyl-terminal domain that regulate receptor signaling and internalization, we generated several CCR5 mutants, which were progressively shortened from the COOH terminus or had carboxyl-terminal serine, cysteine, or leucine residues substituted by alanine and expressed them in RBL-2H3 cells. Using fluorescence resonance energy transfer between beta-arrestin and CCR5 tagged with cyan and yellow variants of green fluorescent protein, we show that high affinity association of the two molecules in living cells requires intact carboxyl-terminal serine phosphorylation sites. Phosphorylation-deficient truncation or Ser/Ala replacement mutants of CCR5 mediated a sustained calcium response and enhanced granular enzyme release in RANTES-stimulated cells. Carboxyl-terminal serine residues are critically involved in CCR5 endocytosis and a dileucine motif, similar to that implicated in the regulation of CXCR2 and CXCR4, contributes to the internalization of CCR5 in a phosphorylation-independent manner. Despite their prominent role in receptor desensitization and internalization, beta-arrestins are dispensable for the CCR5-mediated stimulation of mitogen-activated protein kinase pathways in RBL-2H3 cells. We also show that CCR5 is palmitoylated on carboxyl-terminal cysteine residues. Inhibition of CCR5 palmitoylation by alanine mutagenesis of cysteines or treatment with a palmitate analogue inhibitor profoundly reduces phorbol 12-myristate 13-acetate- and RANTES-induced receptor phosphorylation, homologous desensitization, and internalization. Alanine mutagenesis of serine, cysteine, or leucine residues or the limited carboxyl-terminal truncation of CCR5 did not impair chemokine-stimulated migration of RBL-2H3 cells. Together these results indicate that post-translational modifications of carboxyl-terminal serine and cysteine residues have a significant impact on receptor deactivation and internalization.
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Affiliation(s)
- K Kraft
- Department of Immunology, University of Göttingen, 37075 Göttingen, Germany
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31
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Bylund J, Christophe T, Boulay F, Nyström T, Karlsson A, Dahlgren C. Proinflammatory activity of a cecropin-like antibacterial peptide from Helicobacter pylori. Antimicrob Agents Chemother 2001; 45:1700-4. [PMID: 11353614 PMCID: PMC90534 DOI: 10.1128/aac.45.6.1700-1704.2001] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Helicobacter pylori, the bacterial pathogen associated with gastritis and peptic ulcers, is highly successful in establishing infection in the human gastric mucosa, a process typically associated with massive infiltration of inflammatory cells. Colonization of the mucosa is suggested to be facilitated by H. pylori-produced cecropin-like peptides with antibacterial properties, giving the microbe a competitive advantage over other bacteria. We show that a cecropin-like antibacterial peptide from H. pylori, Hp(2-20), not only has a potent bactericidal effect but also induces proinflammatory activities in human neutrophils, e.g., upregulation of integrins (Mac-1), induction of chemotaxis, and activation of the oxygen radical producing NADPH-oxidase. Furthermore, we show that these effects are mediated through binding of Hp(2-20) to the promiscuous, G-protein-linked lipoxin A(4) receptor-formyl peptide-like receptor 1.
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Affiliation(s)
- J Bylund
- The Phagocyte Research Laboratory, Department of Medical Microbiology and Immunology, University of Göteborg, Göteborg, Sweden.
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32
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Christophe T, Karlsson A, Dugave C, Rabiet MJ, Boulay F, Dahlgren C. The synthetic peptide Trp-Lys-Tyr-Met-Val-Met-NH2 specifically activates neutrophils through FPRL1/lipoxin A4 receptors and is an agonist for the orphan monocyte-expressed chemoattractant receptor FPRL2. J Biol Chem 2001; 276:21585-93. [PMID: 11285256 DOI: 10.1074/jbc.m007769200] [Citation(s) in RCA: 162] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Neutrophils express the G protein-coupled N-formyl peptide receptor (FPR) and its homologue FPRL1, whereas monocytes express FPR, FPRL1, and FPRL2, an orphan receptor sharing 83% amino acid identity with FPRL1. FPRL1 is a promiscuous receptor activated by serum amyloid A and by different synthetic peptides, including the hexapeptide Trp-Lys-Tyr-Met-Val-d-Met-NH(2) (WKYMVm). By measuring calcium flux in HL-60 cells transfected with FPR, FPRL1, or FPRL2, we show that WKYMVm activated all three receptors, whereas the l-conformer WKYMVM activated exclusively FPRL1 and FPRL2. The functionality of FPRL2 was further assessed by the ability of HL-60-FPRL2 cells to migrate toward nanomolar concentrations of hexapeptides. The half-maximal effective concentrations of WKYMVM for calcium mobilization in HL-60-FPRL1 and HL-60-FPRL2 cells were 2 and 80 nm, respectively. Those of WKYMVm were 75 pm and 3 nm. The tritiated peptide WK[3,5-(3)H(2)]YMVM bound to FPRL1 (K(D) approximately 160 nm), but not to FPR. The two conformers similarly inhibited binding of (125)I-labeled WKYMVm to FPRL2-expressing cells (IC(50) approximately 2.5-3 micrometer). Metabolic labeling with orthophosphoric acid revealed that FPRL1 was differentially phosphorylated upon addition of the l- or d-conformer, indicating that it induced different conformational changes. In contrast to FPRL1, FPRL2 was already phosphorylated in the absence of agonist and not evenly distributed in the plasma membrane of unstimulated cells. However, both receptors were internalized upon addition of either of the two conformers. Taken together, the results indicate that neutrophils are activated by WKYMVM through FPRL1 and that FPRL2 is a chemotactic receptor transducing signals in myeloid cells.
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MESH Headings
- Animals
- Calcium/metabolism
- Calcium Signaling/drug effects
- Calcium Signaling/physiology
- Cell Line
- Chemotaxis/drug effects
- Chemotaxis/physiology
- Chemotaxis, Leukocyte/drug effects
- Chemotaxis, Leukocyte/physiology
- Endocytosis
- HL-60 Cells
- Humans
- Kinetics
- Monocyte Chemoattractant Proteins/pharmacology
- NADPH Oxidases/blood
- Neutrophils/drug effects
- Neutrophils/physiology
- Oligopeptides/pharmacokinetics
- Oligopeptides/pharmacology
- Receptors, Cell Surface/drug effects
- Receptors, Cell Surface/physiology
- Receptors, Formyl Peptide
- Receptors, Immunologic/agonists
- Receptors, Immunologic/genetics
- Receptors, Immunologic/physiology
- Receptors, Lipoxin
- Receptors, Peptide/agonists
- Receptors, Peptide/genetics
- Receptors, Peptide/physiology
- Recombinant Proteins/agonists
- Recombinant Proteins/metabolism
- Stereoisomerism
- Transfection
- Tritium
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Affiliation(s)
- T Christophe
- Phagocyte Research Laboratory, Department of Medical Microbiology and Immunology, University of Göteborg, S-40530 Göteborg, Sweden
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33
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Gilbert TL, Bennett TA, Maestas DC, Cimino DF, Prossnitz ER. Internalization of the human N-formyl peptide and C5a chemoattractant receptors occurs via clathrin-independent mechanisms. Biochemistry 2001; 40:3467-75. [PMID: 11297412 DOI: 10.1021/bi001320y] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
After stimulation by ligand, most G protein-coupled receptors (GPCRs) undergo rapid phosphorylation, followed by desensitization and internalization. In the case of the N-formyl peptide receptor (FPR), these latter two processing steps have been shown to be entirely dependent on phosphorylation of the receptor's carboxy terminus. We have previously demonstrated that FPR internalization can occur in the absence of receptor desensitization, indicating that FPR desensitization and internalization are regulated differentially. In this study, we have investigated whether human chemoattractant receptors internalize via clathrin-coated pits. Internalization of the FPR transiently expressed in HEK 293 cells was shown to be dependent upon receptor phosphorylation. Despite this, internalization of the FPR, as well as the C5a receptor, was demonstrated to be independent of the actions of arrestin, dynamin, and clathrin. In addition, we utilized fluorescence microscopy to visualize the FPR and beta(2)-adrenergic receptor as they internalized in the same cell, revealing distinct sites of internalization. Last, we found that a nonphosphorylatable mutant of the FPR, unable to internalize, was competent to activate p44/42 MAP kinase. Together, these results demonstrate not only that the FPR internalizes via an arrestin-, dynamin-, and clathrin-independent pathway but also that signal transduction to MAP kinases occurs in an internalization-independent manner.
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MESH Headings
- Antigens, CD/metabolism
- Arrestin/metabolism
- Cell Line
- Clathrin/genetics
- Clathrin/physiology
- Coated Pits, Cell-Membrane/metabolism
- Complement C5a/metabolism
- Cyclic AMP-Dependent Protein Kinases/metabolism
- Dose-Response Relationship, Drug
- Dynamins
- Enzyme Activation
- Flow Cytometry
- GTP Phosphohydrolases/metabolism
- HL-60 Cells
- Humans
- Ligands
- Mitogen-Activated Protein Kinase 1/metabolism
- Mitogen-Activated Protein Kinase 3
- Mitogen-Activated Protein Kinases/metabolism
- N-Formylmethionine Leucyl-Phenylalanine/metabolism
- Phosphorylation
- Protein Binding
- Receptor, Anaphylatoxin C5a
- Receptors, Adrenergic, beta-2/metabolism
- Receptors, Complement/metabolism
- Receptors, Formyl Peptide
- Receptors, Immunologic/biosynthesis
- Receptors, Immunologic/genetics
- Receptors, Immunologic/metabolism
- Receptors, Peptide/biosynthesis
- Receptors, Peptide/genetics
- Receptors, Peptide/metabolism
- Transfection
- beta-Adrenergic Receptor Kinases
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Affiliation(s)
- T L Gilbert
- Department of Cell Biology and Physiology, University of New Mexico Health Science Center, Albuquerque, New Mexico 87131, USA
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