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Fleming IR, Hannan JP, Swisher GH, Tesdahl CD, Martyr JG, Cordaro NJ, Erbse AH, Falke JJ. Binding of active Ras and its mutants to the Ras binding domain of PI-3-kinase: A quantitative approach to K D measurements. Anal Biochem 2023; 663:115019. [PMID: 36526022 PMCID: PMC9884175 DOI: 10.1016/j.ab.2022.115019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2022] [Revised: 12/07/2022] [Accepted: 12/08/2022] [Indexed: 12/14/2022]
Abstract
Ras family GTPases (H/K/N-Ras) modulate numerous effectors, including the lipid kinase PI3K (phosphatidylinositol-3-kinase) that generates growth signal lipid PIP3 (phosphatidylinositol-3,4,5-triphosphate). Active GTP-Ras binds PI3K with high affinity, thereby stimulating PIP3 production. We hypothesize the affinity of this binding interaction could be significantly increased or decreased by Ras mutations at PI3K contact positions, with clinical implications since some Ras mutations at PI3K contact positions are disease-linked. To enable tests of this hypothesis, we have developed an approach combining UV spectral deconvolution, HPLC, and microscale thermophoresis to quantify the KD for binding. The approach measures the total Ras concentration, the fraction of Ras in the active state, and the affinity of active Ras binding to its docking site on PI3K Ras binding domain (RBD) in solution. The approach is illustrated by KD measurements for the binding of active H-Ras and representative mutants, each loaded with GTP or GMPPNP, to PI3Kγ RBD. The findings demonstrate that quantitation of the Ras activation state increases the precision of KD measurements, while also revealing that Ras mutations can increase (Q25L), decrease (D38E, Y40C), or have no effect (G13R) on PI3K binding affinity. Significant Ras affinity changes are predicted to alter PI3K regulation and PIP3 growth signals.
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Affiliation(s)
- Ian R Fleming
- Molecular Biophysics Program and Department of Biochemistry, University of Colorado, Boulder, CO, 80309-0596, USA
| | - Jonathan P Hannan
- Molecular Biophysics Program and Department of Biochemistry, University of Colorado, Boulder, CO, 80309-0596, USA
| | - George Hayden Swisher
- Molecular Biophysics Program and Department of Biochemistry, University of Colorado, Boulder, CO, 80309-0596, USA
| | - Corey D Tesdahl
- Molecular Biophysics Program and Department of Biochemistry, University of Colorado, Boulder, CO, 80309-0596, USA
| | - Justin G Martyr
- Molecular Biophysics Program and Department of Biochemistry, University of Colorado, Boulder, CO, 80309-0596, USA
| | - Nicholas J Cordaro
- Molecular Biophysics Program and Department of Biochemistry, University of Colorado, Boulder, CO, 80309-0596, USA
| | - Annette H Erbse
- Molecular Biophysics Program and Department of Biochemistry, University of Colorado, Boulder, CO, 80309-0596, USA
| | - Joseph J Falke
- Molecular Biophysics Program and Department of Biochemistry, University of Colorado, Boulder, CO, 80309-0596, USA.
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2
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Renner B, Laskowski J, Poppelaars F, Ferreira VP, Blaine J, Antonioli AH, Hannan JP, Kovacs JM, van Kooten C, You Z, Pickering MC, Holers VM, Thurman JM. Factor H related proteins modulate complement activation on kidney cells. Kidney Int 2022; 102:1331-1344. [PMID: 36063874 PMCID: PMC9691546 DOI: 10.1016/j.kint.2022.07.035] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2021] [Revised: 07/04/2022] [Accepted: 07/27/2022] [Indexed: 01/13/2023]
Abstract
Complement activation at a particular location is determined by the balance of activating and inhibitory proteins. Factor H is a key regulator of the alternative pathway of complement, and genetic or acquired impairments in Factor H are associated with glomerular injury. The human Factor H-related proteins (FHRs) comprise a family of five proteins that are structurally related to Factor H. Variations in the genes or expression levels of the FHRs are also associated with glomerular disease, although the mechanisms of glomerular protection/injury are incompletely understood. To explore the role of the FHRs on complement regulation/dysregulation in the kidney, we expressed and purified recombinant murine FHRs (FHRs A, B, C and E). These four distinct FHRs contain binding regions with high amino acid sequence homology to binding regions within Factor H, but we observed different interactions of the FHRs with Factor H binding ligands, including heparin and C3d. There was differential binding of the FHRs to the resident kidney cell types (mesangial, glomerular endothelial, podocytes, and tubular epithelial). All four FHRs caused complement dysregulation on kidney cell surfaces in vitro, although the magnitude of the effect differed among the FHRs and also varied among the different kidney cells. However, only FHR E caused glomerular complement dysregulation when injected in vivo but did not exacerbate injury when injected into mice with ischemic acute kidney injury, an alternative pathway-mediated model. Thus, our experiments demonstrate that the FHRs have unique, and likely context-dependent, effects on the different cell types within the kidney.
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Affiliation(s)
- Brandon Renner
- Department of Medicine, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, Colorado, USA
| | - Jennifer Laskowski
- Department of Medicine, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, Colorado, USA
| | - Felix Poppelaars
- Department of Medicine, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, Colorado, USA
| | - Viviana P Ferreira
- Department of Medical Microbiology and Immunology, University of Toledo College of Medicine and Life Sciences, Toledo, Ohio, USA
| | - Judith Blaine
- Department of Medicine, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, Colorado, USA
| | | | - Jonathan P Hannan
- Molecular Biophysics Program and Department of Biochemistry, University of Colorado, Boulder, Colorado, USA
| | - James M Kovacs
- Department of Chemistry and Biochemistry, University of Colorado Springs, Colorado Springs, Colorado, USA
| | - Cees van Kooten
- Department of Nephrology, Leiden University Medical Center, Leiden, the Netherlands
| | - Zhiying You
- Department of Medicine, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, Colorado, USA
| | - Matthew C Pickering
- Centre for Inflammatory Disease, Department of Immunology and Inflammation, Imperial College London, London, UK
| | - V Michael Holers
- Department of Medicine, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, Colorado, USA
| | - Joshua M Thurman
- Department of Medicine, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, Colorado, USA.
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3
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Hannan JP, Swisher GH, Martyr JG, Cordaro NJ, Erbse AH, Falke JJ. HPLC method to resolve, identify and quantify guanine nucleotides bound to recombinant ras GTPase. Anal Biochem 2021; 631:114338. [PMID: 34433016 PMCID: PMC8511091 DOI: 10.1016/j.ab.2021.114338] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 08/06/2021] [Accepted: 08/11/2021] [Indexed: 12/31/2022]
Abstract
The Ras superfamily of small G proteins play central roles in diverse signaling pathways. Superfamily members act as molecular on-off switches defined by their occupancy with GTP or GDP, respectively. In vitro functional studies require loading with a hydrolysis-resistant GTP analogue to increase the on-state lifetime, as well as knowledge of fractional loading with activating and inactivating nucleotides. The present study describes a method combining elements of previous approaches with new, optimized features to analyze the bound nucleotide composition of a G protein loaded with activating (GMPPNP) or inactivating (GDP) nucleotide. After nucleotide loading, the complex is washed to remove unbound nucleotides then bound nucleotides are heat-extracted and subjected to ion-paired, reverse-phase HPLC-UV to resolve, identify and quantify the individual nucleotide components. These data enable back-calculation to the nucleotide composition and fractional activation of the original, washed G protein population prior to heat extraction. The method is highly reproducible. Application to multiple HRas preparations and mutants confirms its ability to fully extract and analyze bound nucleotides, and to resolve the fractional on- and off-state populations. Furthermore, the findings yield a novel hypothesis for the molecular disease mechanism of Ras mutations at the E63 and Y64 positions.
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Affiliation(s)
- Jonathan P Hannan
- Molecular Biophysics Program and Department of Biochemistry, University of Colorado, Boulder, CO, USA
| | - G Hayden Swisher
- Molecular Biophysics Program and Department of Biochemistry, University of Colorado, Boulder, CO, USA
| | - Justin G Martyr
- Molecular Biophysics Program and Department of Biochemistry, University of Colorado, Boulder, CO, USA
| | - Nicholas J Cordaro
- Molecular Biophysics Program and Department of Biochemistry, University of Colorado, Boulder, CO, USA
| | - Annette H Erbse
- Molecular Biophysics Program and Department of Biochemistry, University of Colorado, Boulder, CO, USA
| | - Joseph J Falke
- Molecular Biophysics Program and Department of Biochemistry, University of Colorado, Boulder, CO, USA.
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Swisher GH, Hannan JP, Cordaro NJ, Erbse AH, Falke JJ. Ras-guanine nucleotide complexes: A UV spectral deconvolution method to analyze protein concentration, nucleotide stoichiometry, and purity. Anal Biochem 2021; 618:114066. [PMID: 33485819 DOI: 10.1016/j.ab.2020.114066] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 12/09/2020] [Accepted: 12/11/2020] [Indexed: 12/31/2022]
Abstract
The many members of the Ras superfamily are small GTPases that serve as molecular switches. These proteins bind the guanine nucleotides GTP and GDP with picomolar affinities, thereby stabilizing on- and off-signaling states, respectively. Quantitative in vitro Ras studies require accurate determination of total protein, its fractional occupancy with guanine nucleotide, and spectroscopic purity. Yet the high nucleotide affinity of Ras and the overlapping UV spectra of the protein and bound nucleotide make such determinations challenging. Here we describe a generalizable UV spectral deconvolution method to analyze the total protein concentration, total nucleotide stoichiometry, and purity of Ras complexes.
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Affiliation(s)
- G Hayden Swisher
- Molecular Biophysics Program and Department of Biochemistry, University of Colorado, Boulder, CO, 80309-0596, United States
| | - Jonathan P Hannan
- Molecular Biophysics Program and Department of Biochemistry, University of Colorado, Boulder, CO, 80309-0596, United States
| | - Nicholas J Cordaro
- Molecular Biophysics Program and Department of Biochemistry, University of Colorado, Boulder, CO, 80309-0596, United States
| | - Annette H Erbse
- Molecular Biophysics Program and Department of Biochemistry, University of Colorado, Boulder, CO, 80309-0596, United States
| | - Joseph J Falke
- Molecular Biophysics Program and Department of Biochemistry, University of Colorado, Boulder, CO, 80309-0596, United States.
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5
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Antonioli AH, White J, Crawford F, Renner B, Marchbank KJ, Hannan JP, Thurman JM, Marrack P, Holers VM. Modulation of the Alternative Pathway of Complement by Murine Factor H-Related Proteins. J Immunol 2018; 200:316-326. [PMID: 29187587 PMCID: PMC5736413 DOI: 10.4049/jimmunol.1602017] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Accepted: 10/27/2017] [Indexed: 01/21/2023]
Abstract
Factor H (FH) is a key alternative pathway regulator that controls complement activation both in the fluid phase and on specific cell surfaces, thus allowing the innate immune response to discriminate between self and foreign pathogens. However, the interrelationships between FH and a group of closely related molecules, designated the FH-related (FHR) proteins, are currently not well understood. Whereas some studies have suggested that human FHR proteins possess complement regulatory abilities, recent studies have shown that FHR proteins are potent deregulators. Furthermore, the roles of the FHR proteins have not been explored in any in vivo models of inflammatory disease. In this study, we report the cloning and expression of recombinant mouse FH and three FHR proteins (FHR proteins A-C). Results from functional assays show that FHR-A and FHR-B proteins antagonize the protective function of FH in sheep erythrocyte hemolytic assays and increase cell-surface C3b deposition on a mouse kidney proximal tubular cell line (TEC) and a human retinal pigment epithelial cell line (ARPE-19). We also report apparent KD values for the binding interaction of mouse C3d with mouse FH (3.85 μM), FHR-A (136 nM), FHR-B (546 nM), and FHR-C (1.04 μM), which directly correlate with results from functional assays. Collectively, our work suggests that similar to their human counterparts, a subset of mouse FHR proteins have an important modulatory role in complement activation. Further work is warranted to define the in vivo context-dependent roles of these proteins and determine whether FHR proteins are suitable therapeutic targets for the treatment of complement-driven diseases.
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Affiliation(s)
| | - Janice White
- Howard Hughes Medical Institute, Denver, CO 80206
| | | | - Brandon Renner
- Department of Medicine, University of Colorado School of Medicine, Aurora, CO 80045
| | - Kevin J Marchbank
- Institute of Cellular Medicine, Newcastle University, Newcastle-upon-Tyne NE2 4HH, United Kingdom
| | - Jonathan P Hannan
- Department of Medicine, University of Colorado School of Medicine, Aurora, CO 80045
| | - Joshua M Thurman
- Department of Medicine, University of Colorado School of Medicine, Aurora, CO 80045
| | - Philippa Marrack
- Howard Hughes Medical Institute, Denver, CO 80206
- Department of Biomedical Research, National Jewish Health, Denver, CO 80206; and
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO 80045
| | - V Michael Holers
- Department of Medicine, University of Colorado School of Medicine, Aurora, CO 80045;
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Blaum BS, Hannan JP, Herbert AP, Kavanagh D, Uhrín D, Stehle T. Structural basis for sialic acid-mediated self-recognition by complement factor H. Nat Chem Biol 2014; 11:77-82. [PMID: 25402769 DOI: 10.1038/nchembio.1696] [Citation(s) in RCA: 204] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Accepted: 10/02/2014] [Indexed: 12/25/2022]
Abstract
The serum protein complement factor H (FH) ensures downregulation of the complement alternative pathway, a branch of innate immunity, upon interaction with specific glycans on host cell surfaces. Using ligand-based NMR, we screened a comprehensive set of sialylated glycans for binding to FH and solved the crystal structure of a ternary complex formed by the two C-terminal domains of FH, a sialylated trisaccharide and the complement C3b thioester-containing domain. Key residues in the sialic acid binding site are conserved from mice to men, and residues linked to atypical hemolytic uremic syndrome cluster within this binding site, suggesting a possible role for sialic acid as a host marker also in other mammals and a critical role in human renal complement homeostasis. Unexpectedly, the FH sialic acid binding site is structurally homologous to the binding sites of two evolutionarily unrelated proteins. The crystal structure also advances our understanding of bacterial immune evasion strategies.
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Affiliation(s)
- Bärbel S Blaum
- Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen, Germany
| | - Jonathan P Hannan
- Department of Medicine, University of Colorado School of Medicine, Aurora, Colorado, USA
| | | | - David Kavanagh
- Institute of Genetic Medicine, International Centre for Life, Newcastle upon Tyne, UK
| | - Dušan Uhrín
- The School of Chemistry, University of Edinburgh, Scotland, UK
| | - Thilo Stehle
- 1] Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen, Germany. [2] Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
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Thurman JM, Kulik L, Orth H, Wong M, Renner B, Sargsyan SA, Mitchell LM, Hourcade DE, Hannan JP, Kovacs JM, Coughlin B, Woodell AS, Pickering MC, Rohrer B, Holers VM. Detection of complement activation using monoclonal antibodies against C3d. J Clin Invest 2013; 123:2218-30. [PMID: 23619360 DOI: 10.1172/jci65861] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2012] [Accepted: 02/21/2013] [Indexed: 12/21/2022] Open
Abstract
During complement activation the C3 protein is cleaved, and C3 activation fragments are covalently fixed to tissues. Tissue-bound C3 fragments are a durable biomarker of tissue inflammation, and these fragments have been exploited as addressable binding ligands for targeted therapeutics and diagnostic agents. We have generated cross-reactive murine monoclonal antibodies against human and mouse C3d, the final C3 degradation fragment generated during complement activation. We developed 3 monoclonal antibodies (3d8b, 3d9a, and 3d29) that preferentially bind to the iC3b, C3dg, and C3d fragments in solution, but do not bind to intact C3 or C3b. The same 3 clones also bind to tissue-bound C3 activation fragments when injected systemically. Using mouse models of renal and ocular disease, we confirmed that, following systemic injection, the antibodies accumulated at sites of C3 fragment deposition within the glomerulus, the renal tubulointerstitium, and the posterior pole of the eye. To detect antibodies bound within the eye, we used optical imaging and observed accumulation of the antibodies within retinal lesions in a model of choroidal neovascularization (CNV). Our results demonstrate that imaging methods that use these antibodies may provide a sensitive means of detecting and monitoring complement activation-associated tissue inflammation.
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Affiliation(s)
- Joshua M Thurman
- Department of Medicine, University of Colorado School of Medicine, Aurora, Colorado 80045, USA.
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8
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Thurman JM, Kulik L, Mitchell LM, Hourcade DE, Hannan JP, Coughlin B, Woodell AS, Pickering MC, Rohrer B, Holers M. Novel monoclonal antibodies to C3d that target and identify in living animals sites of complement activation. Immunobiology 2012. [DOI: 10.1016/j.imbio.2012.08.179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Kulik L, Thurman JM, Hannan JP, Tomlinson S, Holers MV. Novel mouse anti-mouse monoclonal antibodies that block either the ligand or receptor member of the CR2–C3d interaction pair impair antigen-specific humoral immune responses to model antigens. Immunobiology 2012. [DOI: 10.1016/j.imbio.2012.08.180] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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10
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Holers VM, Thurman JM, Hannan JP, Kulik L. Evaluating the B-cell C3d:CR2 innate-adaptive immune interaction as a therapeutic target in lupus. Arthritis Res Ther 2012. [PMCID: PMC3467515 DOI: 10.1186/ar3972] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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11
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Morgan HP, Mertens HDT, Guariento M, Schmidt CQ, Soares DC, Svergun DI, Herbert AP, Barlow PN, Hannan JP. Structural analysis of the C-terminal region (modules 18-20) of complement regulator factor H (FH). PLoS One 2012; 7:e32187. [PMID: 22389686 PMCID: PMC3289644 DOI: 10.1371/journal.pone.0032187] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2011] [Accepted: 01/23/2012] [Indexed: 11/19/2022] Open
Abstract
Factor H (FH) is a soluble regulator of the human complement system affording protection to host tissues. It selectively inhibits amplification of C3b, the activation-specific fragment of the abundant complement component C3, in fluid phase and on self-surfaces and accelerates the decay of the alternative pathway C3 convertase, C3bBb. We have determined the crystal structure of the three carboxyl-terminal complement control protein (CCP) modules of FH (FH18-20) that bind to C3b, and which additionally recognize polyanionic markers specific to self-surfaces. These CCPs harbour nearly 30 disease-linked missense mutations. We have also deployed small-angle X-ray scattering (SAXS) to investigate FH18-20 flexibility in solution using FH18-20 and FH19-20 constructs. In the crystal lattice FH18-20 adopts a "J"-shape: A ~122-degree tilt between the structurally highly similar modules 18 and 19 precedes an extended, linear arrangement of modules 19 and 20 as observed in previously determined structures of these two modules alone. However, under solution conditions FH18-20 adopts multiple conformations mediated by flexibility between CCPs 18 and 19. We also pinpoint the locations of disease-associated missense mutations on the module 18 surface and discuss our data in the context of the C3b:FH interaction.
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Affiliation(s)
- Hugh P. Morgan
- Institute of Structural and Molecular Biology, School of Biological Sciences, King's Buildings, University of Edinburgh, Edinburgh, United Kingdom
| | | | - Mara Guariento
- Edinburgh Biomolecular NMR Unit, EaStCHEM, School of Chemistry, University of Edinburgh, Edinburgh, United Kingdom
| | - Christoph Q. Schmidt
- Edinburgh Biomolecular NMR Unit, EaStCHEM, School of Chemistry, University of Edinburgh, Edinburgh, United Kingdom
| | - Dinesh C. Soares
- Centre for Molecular Medicine, Institute of Genetics and Molecular Medicine, The University of Edinburgh, Western General Hospital, Edinburgh, United Kingdom
| | - Dmitri I. Svergun
- European Molecular Biology Laboratory, Hamburg Outstation, Hamburg, Germany
| | - Andrew P. Herbert
- Edinburgh Biomolecular NMR Unit, EaStCHEM, School of Chemistry, University of Edinburgh, Edinburgh, United Kingdom
| | - Paul N. Barlow
- Edinburgh Biomolecular NMR Unit, EaStCHEM, School of Chemistry, University of Edinburgh, Edinburgh, United Kingdom
| | - Jonathan P. Hannan
- Institute of Structural and Molecular Biology, School of Biological Sciences, King's Buildings, University of Edinburgh, Edinburgh, United Kingdom
- * E-mail:
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Herbert AP, Kavanagh D, Johansson C, Morgan HP, Blaum BS, Hannan JP, Barlow PN, Uhrín D. Structural and functional characterization of the product of disease-related factor H gene conversion. Biochemistry 2012; 51:1874-84. [PMID: 22320225 DOI: 10.1021/bi201689j] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Numerous complement factor H (FH) mutations predispose patients to atypical hemolytic uremic syndrome (aHUS) and other disorders arising from inadequately regulated complement activation. No unifying structural or mechanistic consequences have been ascribed to these mutants beyond impaired self-cell protection. The S1191L and V1197A mutations toward the C-terminus of FH, which occur in patients singly or together, arose from gene conversion between CFH encoding FH and CFHR1 encoding FH-related 1. We show that neither single nor double mutations structurally perturbed recombinant proteins consisting of the FH C-terminal modules, 19 and 20 (FH19-20), although all three FH19-20 mutants were poor, compared to wild-type FH19-20, at promoting hemolysis of C3b-coated erythrocytes through competition with full-length FH. Indeed, our new crystal structure of the S1191L mutant of FH19-20 complexed with an activation-specific complement fragment, C3d, was nearly identical to that of the wild-type FH19-20:C3d complex, consistent with mutants binding to C3b with wild-type-like affinity. The S1191L mutation enhanced thermal stability of module 20, whereas the V1197A mutation dramatically decreased it. Thus, although mutant proteins were folded at 37 °C, they differ in conformational rigidity. Neither single substitutions nor double substitutions increased measurably the extent of FH19-20 self-association, nor did these mutations significantly affect the affinity of FH19-20 for three glycosaminoglycans, despite critical roles of module 20 in recognizing polyanionic self-surface markers. Unexpectedly, FH19-20 mutants containing Leu1191 self-associated on a heparin-coated surface to a higher degree than on surfaces coated with dermatan or chondroitin sulfates. Thus, potentially disease-related functional distinctions between mutants, and between FH and FH-related 1, may manifest in the presence of specific glycosaminoglycans.
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Affiliation(s)
- Andrew P Herbert
- Edinburgh Biomolecular NMR Unit, EastChem School of Chemistry, University of Edinburgh, Edinburgh EH9 3JJ, UK
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13
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Morgan HP, Jiang J, Herbert AP, Kavanagh D, Uhrin D, Barlow PN, Hannan JP. Crystallographic determination of the disease-associated T1184R variant of complement regulator factor H. Acta Crystallogr D Biol Crystallogr 2011; 67:593-600. [PMID: 21697597 DOI: 10.1107/s0907444911015423] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2011] [Accepted: 04/24/2011] [Indexed: 11/10/2022]
Abstract
The soluble 155 kDa glycoprotein factor H (FH) protects host tissue from damage by the human complement system. It accelerates decay of the alternative-pathway C3 convertase, C3bBb, and is a cofactor for factor I-mediated cleavage of the opsonin C3b. Numerous mutations and single-nucleotide polymorphisms (SNPs) occur in the gene encoding FH and the resulting missense mutations and truncation products result in altered functionality that predisposes to the development of the serious renal condition atypical haemolytic uraemic syndrome (aHUS). Other polymorphisms are linked to membranoproliferative glomerulonephritis and macular degeneration. The two C-terminal modules of FH (FH19-20) harbour numerous aHUS-associated mutations that disrupt the ability of factor H to protect host cells from complement-mediated damage. In this work, the crystal structure of an aHUS-associated T1184R variant of FH19-20 at a resolution of 1.52 Å is described. It is shown that this mutation has negligible structural effects but causes a significant change in the electrostatic surface of these two domains. Mechanisms are discussed by which this mutation may alter FH-ligand interactions, particularly with regard to the extension of a region of this molecule within module 20 that has been associated with the binding of glycosaminoglycans (GAGs) or sialic acid residues.
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Affiliation(s)
- Hugh P Morgan
- Institute of Structural and Molecular Biology, School of Biological Sciences, University of Edinburgh, King's Buildings, Mayfield Road, Scotland
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Morgan HP, Schmidt CQ, Guariento M, Blaum BS, Gillespie D, Herbert AP, Kavanagh D, Mertens HDT, Svergun DI, Johansson CM, Uhrín D, Barlow PN, Hannan JP. Structural basis for engagement by complement factor H of C3b on a self surface. Nat Struct Mol Biol 2011; 18:463-70. [PMID: 21317894 PMCID: PMC3512577 DOI: 10.1038/nsmb.2018] [Citation(s) in RCA: 195] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2010] [Accepted: 01/14/2011] [Indexed: 12/15/2022]
Abstract
Complement factor H (FH) attenuates C3b molecules tethered via their thioester domains to self-surfaces and thereby protects host tissues. FH is a cofactor for initial C3b proteolysis that ultimately yields a surface-attached fragment (C3d), corresponding to the thioester domain. We used NMR and X-ray crystallography to study the C3d:FH19–20 complex in atomic detail. NMR further identified glycosaminoglycan-binding residues in FH module 20 of the C3d:FH19–20 complex. Mutagenesis justified the merging of the C3d:FH19–20 structure with an existing C3b:FH1–4 crystal structure. The merged structure was concatenated with the available FH6–8 crystal structure and new SAXS-derived FH1–4, FH8–15 and FH15–19 envelopes. The combined data suggests a bent-back FH molecule, binding via its termini to two sites on one C3b molecule and simultaneously to adjacent polyanionic host-surface markers.
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Affiliation(s)
- Hugh P Morgan
- Institute of Structural and Molecular Biology, School of Biological Sciences, King's Buildings, University of Edinburgh, Edinburgh, UK
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Shaw CD, Storek MJ, Young KA, Kovacs JM, Thurman JM, Holers VM, Hannan JP. Delineation of the complement receptor type 2-C3d complex by site-directed mutagenesis and molecular docking. J Mol Biol 2010; 404:697-710. [PMID: 20951140 DOI: 10.1016/j.jmb.2010.10.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2010] [Revised: 10/04/2010] [Accepted: 10/06/2010] [Indexed: 12/01/2022]
Abstract
The interactions between the complement receptor type 2 (CR2) and the C3 complement fragments C3d, C3dg, and iC3b are essential for the initiation of a normal immune response. A crystal-derived structure of the two N-terminal short consensus repeat (SCR1-2) domains of CR2 in complex with C3d has previously been elucidated. However, a number of biochemical and biophysical studies targeting both CR2 and C3d appear to be in conflict with these structural data. Previous mutagenesis and heteronuclear NMR spectroscopy studies directed toward the C3d-binding site on CR2 have indicated that the CR2-C3d cocrystal structure may represent an encounter/intermediate or nonphysiological complex. With regard to the CR2-binding site on C3d, mutagenesis studies by Isenman and coworkers [Isenman, D. E., Leung, E., Mackay, J. D., Bagby, S. & van den Elsen, J. M. H. (2010). Mutational analyses reveal that the staphylococcal immune evasion molecule Sbi and complement receptor 2 (CR2) share overlapping contact residues on C3d: Implications for the controversy regarding the CR2/C3d cocrystal structure. J. Immunol. 184, 1946-1955] have implicated an electronegative "concave" surface on C3d in the binding process. This surface is discrete from the CR2-C3d interface identified in the crystal structure. We generated a total of 18 mutations targeting the two (X-ray crystallographic- and mutagenesis-based) proposed CR2 SCR1-2 binding sites on C3d. Using ELISA analyses, we were able to assess binding of mutant forms of C3d to CR2. Mutations directed toward the concave surface of C3d result in substantially compromised CR2 binding. By contrast, targeting the CR2-C3d interface identified in the cocrystal structure and the surrounding area results in significantly lower levels of disruption in binding. Molecular modeling approaches used to investigate disparities between the biochemical data and the X-ray structure of the CR2-C3d cocrystal result in highest-scoring solutions in which CR2 SCR1-2 is docked within the concave surface of C3d.
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Affiliation(s)
- Craig D Shaw
- Institute of Structural and Molecular Biology, School of Biological Sciences, King's Buildings, Mayfield Road, University of Edinburgh, Edinburgh EH9 3JR, UK
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Kovacs JM, Hannan JP, Eisenmesser EZ, Holers VM. Biophysical investigations of complement receptor 2 (CD21 and CR2)-ligand interactions reveal amino acid contacts unique to each receptor-ligand pair. J Biol Chem 2010; 285:27251-27258. [PMID: 20558730 PMCID: PMC2930724 DOI: 10.1074/jbc.m110.106617] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2010] [Revised: 05/18/2010] [Indexed: 11/06/2022] Open
Abstract
Human complement receptor type 2 (CR2 and CD21) is a cell membrane receptor, with 15 or 16 extracellular short consensus repeats (SCRs), that promotes B lymphocyte responses and bridges innate and acquired immunity. The most distally located SCRs, SCR1-2, mediate the interaction of CR2 with its four known ligands (C3d, EBV gp350, IFNalpha, and CD23). To ascertain specific interacting residues on CR2, we utilized NMR studies wherein gp350 and IFNalpha were titrated into (15)N-labeled SCR1-2, and chemical shift changes indicative of specific inter-molecular interactions were identified. With backbone assignments made, the chemical shift changes were mapped onto the crystal structure of SCR1-2. With regard to gp350, the binding region of CR2 is primarily focused on SCR1 and the inter-SCR linker, specifically residues Asn(11), Arg(13), Ala(22), Arg(28), Ser(32), Arg(36), Lys(41), Lys(57), Tyr(64), Lys(67), Tyr(68), Arg(83), Gly(84), and Arg(89). With regard to IFNalpha, the binding is similar to the CR2-C3d interaction with specific residues being Arg(13), Tyr(16), Arg(28), Ser(42), Lys(48), Lys(50), Tyr(68), Arg(83), Gly(84), and Arg(89). We also report thermodynamic properties of each ligand-receptor pair determined using isothermal titration calorimetry. The CR2-C3d interaction was characterized as a two-mode binding interaction with K(d) values of 0.13 and 160 microm, whereas the CR2-gp350 and CR2-IFNalpha interactions were characterized as single site binding events with affinities of 0.014 and 0.035 microm, respectively. The compilation of chemical binding maps suggests specific residues on CR2 that are uniquely important in each of these three binding interactions.
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Affiliation(s)
- James M Kovacs
- Department of Medicine and Immunology, University of Colorado Denver School of Medicine, Aurora, Colorado 80045
| | - Jonathan P Hannan
- Institute of Structural and Molecular Biology, University of Edinburgh, Edinburgh EH9 3JR, Scotland, United Kingdom
| | - Elan Z Eisenmesser
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver School of Medicine, Aurora, Colorado 80045
| | - V Michael Holers
- Department of Medicine and Immunology, University of Colorado Denver School of Medicine, Aurora, Colorado 80045.
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Kovacs JM, Hannan JP, Eisenmesser EZ, Holers VM. Mapping of the C3d ligand binding site on complement receptor 2 (CR2/CD21) using nuclear magnetic resonance and chemical shift analysis. J Biol Chem 2009; 284:9513-20. [PMID: 19164292 PMCID: PMC2666603 DOI: 10.1074/jbc.m808404200] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2008] [Revised: 01/06/2009] [Indexed: 11/06/2022] Open
Abstract
Complement receptor 2 (CR2, CD21) is a cell membrane protein, with 15 or 16 extracellular short consensus repeats (SCRs), that promotes B lymphocyte responses and bridges innate and acquired immunity. The most distally located SCRs (SCR1-2) mediate the interaction of CR2 with its four known ligands (C3d, Epstein-Barr virus gp350, interferon-alpha, and CD23). Inhibitory monoclonal antibodies against SCR1-2 block binding of all ligands. To develop ligand-specific inhibitors that would also assist in identifying residues unique to each receptor-ligand interaction, phage were selected from randomly generated libraries by panning with recombinant SCR1-2, followed by specific ligand-driven elution. Derived peptides were tested by competition ELISA. One peptide, C3dp1 (APQHLSSQYSRT) exhibited ligand-specific inhibition at midmicromolar IC(50). C3d was titrated into (15)N-labeled SCR1-2, which revealed chemical shift changes indicative of specific intermolecular interactions. With backbone assignments made, the chemical shift changes were mapped onto the crystal structure of SCR1-2. With regard to C3d, the binding surface includes regions of SCR1, SCR2, and the inter-SCR linker, specifically residues Arg(13), Tyr(16), Arg(28), Tyr(29), Ser(32), Thr(34), Lys(48), Asp(56), Lys(57), Tyr(68), Arg(83), Gly(84), Asn(101), Asn(105), and Ser(109). SCR1 and SCR2 demonstrated distinct binding modes. The CR2 binding surface incorporating SCR1 is inconsistent with a previous x-ray CR2-C3d co-crystal analysis but consistent with mutagenesis, x-ray neutron scattering, and inhibitory monoclonal antibody epitope mapping. Titration with C3dp1 yielded chemical shift changes (Arg(13), Tyr(16), Thr(34), Lys(48), Asp(56), Lys(57), Tyr(68), Arg(83), Gly(84), Asn(105), and Ser(109)) overlapping with C3d, indicating that C3dp1 interacts at the same CR2 site as C3d.
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Affiliation(s)
- James M Kovacs
- Department of Medicine, University of Colorado Denver School of Medicine, Aurora, Colorado 80045, USA
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Kovacs JM, Hannan JP, Holers VM. Defining CD21‐ligand interactions using ligand specific inhibitory peptides. FASEB J 2008. [DOI: 10.1096/fasebj.22.1_supplement.1066.8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- James M Kovacs
- Medicine/ImmunologyUniversity of Colorado Denver SOMAuroraCO
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Young KA, Chen XS, Holers VM, Hannan JP. Isolating the Epstein-Barr virus gp350/220 binding site on complement receptor type 2 (CR2/CD21). J Biol Chem 2007; 282:36614-25. [PMID: 17925391 DOI: 10.1074/jbc.m706324200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Complement receptor type 2 (CR2/CD21) is essential for the attachment of Epstein-Barr virus (EBV) to the surface of B-lymphocytes in an interaction mediated by the viral envelope glycoprotein gp350. The heavily glycosylated structure of EBV gp350 has recently been elucidated by x-ray crystallography, and the CR2 binding site on this protein has been characterized. To identify the corresponding gp350 binding site on CR2, we have undertaken a site-directed mutagenesis study targeting regions of CR2 that have previously been implicated in the binding of CR2 to the C3d/C3dg fragments of complement component C3. Wild-type or mutant forms of CR2 were expressed on K562 cells, and the ability of these CR2-expressing cells to bind gp350 was measured using flow cytometry. Mutations directed toward the two N-terminal extracellular domains of CR2 (SCR1-2) reveal that a large contiguous surface of CR2 SCR1-2 is involved in gp350 binding, including a number of positively charged residues (Arg-13, (Arg-28, (Arg-36, Lys-41, Lys-57, Lys-67, and Arg-83). These data appear to complement the CR2 binding site on gp350, which is characterized by a preponderance of negative charge. In addition to identifying the importance of charge in the formation of a CR2-gp350 complex, we also provide evidence that both SCR1 and SCR2 make contact with gp350. Specifically, two anti-CR2 monoclonal antibodies, designated as monoclonal antibodies 171 and 1048 whose primary epitopes are located within SCR2, inhibit binding of wild-type CR2 to EBV gp350; with regard to SCR1, both K562 cells expressing an S15P mutation and recombinant S15P CR2 proteins exhibit diminished gp350 binding.
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Affiliation(s)
- Kendra A Young
- Department of Medicine and Immunology, University of Colorado at Denver and Health Sciences Center, Aurora, Colorado 80045, USA
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Hannan JP, Young KA, Herbert AP, Chen XS, Barlow PN, Holers VM. Characterizing the complement receptor type 2 (CR2)–Epstein-Barr virus interaction: A site-directed mutagenesis and molecular docking approach. Mol Immunol 2007. [DOI: 10.1016/j.molimm.2007.06.051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Hannan JP, Young KA, Szakonyi G, Klein M, Chen XS, Holers VM. Isolating the Epstein–Barr virus (EBV) gp350/220 binding site on complement receptor type 2 (CR2/CD21) using site-directed mutagenesis. Mol Immunol 2007. [DOI: 10.1016/j.molimm.2006.07.081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Szakonyi G, Klein MG, Hannan JP, Young KA, Ma RZ, Holers VM, Chen XS. Structure of the Epstein Barr virus major envelope glycoprotein and CR2 binding. Mol Immunol 2007. [DOI: 10.1016/j.molimm.2006.07.235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Szakonyi G, Klein MG, Hannan JP, Young KA, Ma RZ, Asokan R, Holers VM, Chen XS. Structure of the Epstein-Barr virus major envelope glycoprotein. Nat Struct Mol Biol 2006; 13:996-1001. [PMID: 17072314 DOI: 10.1038/nsmb1161] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2006] [Accepted: 09/28/2006] [Indexed: 11/08/2022]
Abstract
Epstein-Barr virus (EBV) infection of B cells is associated with lymphoma and other human cancers. EBV infection is initiated by the binding of the viral envelope glycoprotein (gp350) to the cell surface receptor CR2. We determined the X-ray structure of the highly glycosylated gp350 and defined the CR2 binding site on gp350. Polyglycans shield all but one surface of the gp350 polypeptide, and we demonstrate that this glycan-free surface is the receptor-binding site. Deglycosylated gp350 bound CR2 similarly to the glycosylated form, suggesting that glycosylation is not important for receptor binding. Structure-guided mutagenesis of the glycan-free surface disrupted receptor binding as well as binding by a gp350 monoclonal antibody, a known inhibitor of virus-receptor interactions. These results provide structural information for developing drugs and vaccines to prevent infection by EBV and related viruses.
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Affiliation(s)
- Gerda Szakonyi
- Department of Molecular and Computational Biology, University of Southern California, 1050 Childs Way, Los Angeles, California 90089, USA
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Asokan R, Hua J, Young KA, Gould HJ, Hannan JP, Kraus DM, Szakonyi G, Grundy GJ, Chen XS, Crow MK, Holers VM. Characterization of human complement receptor type 2 (CR2/CD21) as a receptor for IFN-alpha: a potential role in systemic lupus erythematosus. J Immunol 2006; 177:383-94. [PMID: 16785534 DOI: 10.4049/jimmunol.177.1.383] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Human complement receptor type 2 (CR2/CD21) is a B lymphocyte membrane glycoprotein that plays a central role in the immune responses to foreign Ags as well as the development of autoimmunity to nuclear Ags in systemic lupus erythematosus. In addition to these three well-characterized ligands, C3d/iC3b, EBV-gp350, and CD23, a previous study has identified CR2 as a potential receptor for IFN-alpha. IFN-alpha, a multifunctional cytokine important in the innate immune system, has recently been proposed to play a major pathogenic role in the development of systemic lupus erythematosus in humans and mice. In this study, we have shown using surface plasmon resonance and ELISA approaches that CR2 will bind IFN-alpha in the same affinity range as the other three well-characterized ligands studied in parallel. In addition, we show that IFN-alpha interacts with short consensus repeat domains 1 and 2 in a region that serves as the ligand binding site for C3d/iC3b, EBV-gp350, and CD23. Finally, we show that treatment of purified human peripheral blood B cells with the inhibitory anti-CR2 mAb 171 diminishes the induction of IFN-alpha-responsive genes. Thus, IFN-alpha represents a fourth class of extracellular ligands for CR2 and interacts with the same domain as the other three ligands. Defining the role of CR2 as compared with the well-characterized type 1 IFN-alpha receptor 1 and 2 in mediating innate immune and autoimmune roles of this cytokine should provide additional insights into the biologic roles of this interaction.
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MESH Headings
- Antibodies, Monoclonal/metabolism
- Binding, Competitive
- Cells, Cultured
- Complement C3d/metabolism
- Dose-Response Relationship, Immunologic
- GTP-Binding Proteins/antagonists & inhibitors
- GTP-Binding Proteins/genetics
- GTP-Binding Proteins/metabolism
- HSP40 Heat-Shock Proteins/antagonists & inhibitors
- HSP40 Heat-Shock Proteins/genetics
- HSP40 Heat-Shock Proteins/metabolism
- Humans
- Hydrogen-Ion Concentration
- Interferon-alpha/metabolism
- Ligands
- Lupus Erythematosus, Systemic/immunology
- Lupus Erythematosus, Systemic/metabolism
- Membrane Glycoproteins/metabolism
- Myxovirus Resistance Proteins
- Protein Binding
- Protein Interaction Mapping
- Receptors, Complement 3d/chemistry
- Receptors, Complement 3d/genetics
- Receptors, Complement 3d/metabolism
- Receptors, Complement 3d/physiology
- Receptors, IgE/metabolism
- Recombinant Proteins/biosynthesis
- Recombinant Proteins/chemistry
- Recombinant Proteins/metabolism
- Sodium Chloride/metabolism
- Surface Plasmon Resonance
- Viral Matrix Proteins/metabolism
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Affiliation(s)
- Rengasamy Asokan
- Department of Medicine and Department of Immunology, University of Colorado Health Sciences Center, 4200 East Ninth Avenue, Denver, CO 80262, USA
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Hibbert RG, Teriete P, Grundy GJ, Beavil RL, Reljic R, Holers VM, Hannan JP, Sutton BJ, Gould HJ, McDonnell JM. The structure of human CD23 and its interactions with IgE and CD21. ACTA ACUST UNITED AC 2005; 202:751-60. [PMID: 16172256 PMCID: PMC2212946 DOI: 10.1084/jem.20050811] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
The low-affinity immunoglobulin E (IgE) receptor, CD23 (FcepsilonRII), binds both IgE and CD21 and, through these interactions, regulates the synthesis of IgE, the antibody isotype that mediates the allergic response. We have determined the three-dimensional structure of the C-type lectin domain of CD23 in solution by nuclear magnetic resonance spectroscopy. An analysis of concentration-dependent chemical shift perturbations have allowed us to identify the residues engaged in self-association to the trimeric state, whereas ligand-induced changes have defined the binding sites for IgE and CD21. The results further reveal that CD23 can bind both ligands simultaneously. Despite the C-type lectin domain structure, none of the interactions require calcium. We also find that IgE and CD23 can interact to form high molecular mass multimeric complexes. The interactions that we have described provide a solution to the paradox that CD23 is involved in both up- and down-regulation of IgE and provide a structural basis for the development of inhibitors of allergic disease.
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Affiliation(s)
- Richard G Hibbert
- Laboratory of Molecular Biophysics, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, England, UK
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Gilbert HE, Eaton JT, Hannan JP, Holers VM, Perkins SJ. Solution structure of the complex between CR2 SCR 1-2 and C3d of human complement: an X-ray scattering and sedimentation modelling study. J Mol Biol 2005; 346:859-73. [PMID: 15713468 DOI: 10.1016/j.jmb.2004.12.006] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2004] [Revised: 10/11/2004] [Accepted: 12/03/2004] [Indexed: 10/26/2022]
Abstract
Complement receptor type 2 (CR2, CD21) forms a tight complex with C3d, a fragment of C3, the major complement component. Previous crystal structures of the C3d-CR2 SCR 1-2 complex and free CR2 SCR 1-2 showed that the two SCR domains of CR2 form contact with each other in a closed V-shaped structure. SCR 1 and SCR 2 are connected by an unusually long eight-residue linker peptide. Medium-resolution solution structures for CR2 SCR 1-2, C3d, and their complex were determined by X-ray scattering and analytical ultracentrifugation. CR2 SCR 1-2 is monomeric. For CR2 SCR 1-2, its radius of gyration R(G) of 2.12(+/-0.05) nm, its maximum length of 10nm and its sedimentation coefficient s20,w(o) of 1.40(+/-0.03) S do not agree with those calculated from the crystal structures, and instead suggest an open structure. Computer modelling of the CR2 SCR1-2 solution structure was based on the structural randomisation of the eight-residue linker peptide joining SCR 1 and SCR 2 to give 9950 trial models. Comparisons with the X-ray scattering curve indicated that the most favoured arrangements for the two SCR domains corresponded to an open V-shaped structure with no contacts between the SCR domains. For C3d, X-ray scattering and sedimentation velocity experiments showed that it exists as a monomer-dimer equilibrium with a dissociation constant of 40 microM. The X-ray scattering curve for monomeric C3d gave an R(G) value of 1.95 nm, and this together with its s20,w(o) value of 3.17 S gave good agreement with the monomeric C3d crystal structure. Modelling of the C3d dimer gave good agreements with its scattering and ultracentrifugation parameters. For the complex, scattering and ultracentrifugation experiments showed that there was no dimerisation, indicating that the C3d dimerisation site was located close to the CR2 SCR 1-2 binding site. The R(G) value of 2.44(+/-0.1) nm, its length of 9 nm and its s20,w(o) value of 3.45(+/-0.01) S showed that its structure was not much more elongated than that of C3d. Calculations with 9950 models of CR2 SCR 1-2 bound to C3d through SCR 2 showed that SCR 1 formed an open V-shaped structure with SCR 2 and was capable of interacting with the surface of C3d. We conclude that the open V-shaped structures formed by CR2 SCR 1-2, both when free and when bound to C3d, are optimal for the formation of a tight two-domain interaction with its ligand C3d.
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Affiliation(s)
- Hannah E Gilbert
- Department of Biochemistry and Molecular Biology, Darwin Building, University College London, Gower Street, London WC1E 6BT, UK
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Hannan JP, Young KA, Guthridge JM, Asokan R, Szakonyi G, Chen XS, Holers VM. Mutational analysis of the complement receptor type 2 (CR2/CD21)-C3d interaction reveals a putative charged SCR1 binding site for C3d. J Mol Biol 2005; 346:845-58. [PMID: 15713467 DOI: 10.1016/j.jmb.2004.12.007] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2004] [Revised: 12/02/2004] [Accepted: 12/03/2004] [Indexed: 11/23/2022]
Abstract
We have characterized the interaction between the first two short consensus repeats (SCR1-2) of complement receptor type 2 (CR2, CD21) and C3d in solution, by utilising the available crystal structures of free and C3d-bound forms of CR2 to create a series of informative mutations targeting specific areas of the CR2-C3d complex. Wild-type and mutant forms of CR2 were expressed on the surface of K562 erythroleukemia cells and their binding ability assessed using C3dg-biotin tetramers complexed to fluorochrome conjugated streptavidin and measured by flow cytometry. Mutations directed at the SCR2-C3d interface (R83A, R83E, G84Y) were found to strongly disrupt C3dg binding, supporting the conclusion that the SCR2 interface reflected in the crystal structure is correct. Previous epitope and peptide mapping studies have also indicated that the PILN11GR13IS sequence of the first inter-cysteine region of SCR1 is essential for the binding of iC3b. Mutations targeting residues within or in close spatial proximity to this area (N11A, N11E, R13A, R13E, Y16A, S32A, S32E), and a number of other positively charged residues located primarily on a contiguous face of SCR1 (R28A, R28E, R36A, R36E, K41A, K41E, K50A, K50E, K57A, K57E, K67A, K67E), have allowed us to reassess those regions on SCR1 that are essential for CR2-C3d binding. The nature of this interaction and the possibility of a direct SCR1-C3d association are discussed extensively. Finally, a D52N mutant was constructed introducing an N-glycosylation sequence at an area central to the CR2 dimer interface. This mutation was designed to disrupt the CR2-C3d interaction, either directly through steric inhibition, or indirectly through disruption of a physiological dimer. However, no difference in C3dg binding relative to wild-type CR2 could be observed for this mutant, suggesting that the dimer may only be found in the crystal form of CR2.
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Affiliation(s)
- Jonathan P Hannan
- Department of Medicine and Immunology, University of Colorado Health Sciences Center, 4200 East Ninth Ave., Denver, CO 80262, USA
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Hannan JP, Busch JL, Breton J, James R, Thomson AJ, Moore GR, Davy SL. Characterisation of oxidised 7Fe dicluster ferredoxins with NMR spectroscopy. J Biol Inorg Chem 2000; 5:432-47. [PMID: 10968614 DOI: 10.1007/pl00021445] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Dicluster ferredoxins (Fds) from Sulfolobus acidocaldarius and Desulfovibrio africanus (FdIII) have been studied using 1H NMR. Both wild-type proteins contain a [3Fe-4S]+/0 and a [4Fe-4S]2+/+ cluster as isolated. The [4Fe-4S]2+/+ cluster (cluster II) is bound by cysteine residues arranged in a classic ferredoxin motif: CysI-(Xaa)2-CysII-(Xaa)2-CysIII-(Xaa)n-CysIV-Pro , whilst the binding motif of the [3Fe-4S]+/0 cluster (cluster I) has a non-ligating aspartic acid (Asp14) at position II, i.e. CysI-(Xaa)2-Asp-(Xaa)2-CysIII. D. africanus FdIII undergoes facile cluster transformation from the 7Fe form to the 8Fe form, but S. acidocaldarius Fd does not. Many factors determine the propensity of a cluster to undergo interconversion, including the presence, and correct orientation, of a suitable ligand. We have investigated this using 1H NMR by introducing a potential fourth ligand into the binding motif of cluster I of D. africanus FdIII. Asp14 has been mutated to cysteine (D14C), glutamic acid (D14E) and histidine (D14H). Cluster incorporation was performed in vitro. The cluster types present were identified from the chemical shift patterns and temperature-dependent behaviour of the hyperfine-shifted resonances. Factors influencing cluster ligation and cluster interconversion, in vitro, are discussed. Furthermore, the data have established that the residue at position II in the cluster binding motif of cluster I is influential in determining the chemical shift pattern observed for a [3Fe-4S]+ cluster when a short/symmetric binding motif is present. Based on this, a series of rules for characterising the 1H NMR chemical shifts of mono- and di-cluster [3Fe-4S]+ cluster-containing ferredoxins is given.
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Affiliation(s)
- J P Hannan
- School of Chemical Sciences, University of East Anglia, Norwich Research Park, Norwich, UK
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Hannan JP, Whittaker SB, Hemmings AM, James R, Kleanthous C, Moore GR. NMR studies of metal ion binding to the Zn-finger-like HNH motif of colicin E9. J Inorg Biochem 2000; 79:365-70. [PMID: 10830890 DOI: 10.1016/s0162-0134(99)00235-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The 134 amino acid DNase domain of colicin E9 contains a zinc-finger-like HNH motif that binds divalent transition metal ions. We have used 1D 1H and 2D 1H-15N NMR methods to characterise the binding of Co2+, Ni2+ and Zn2+ to this protein. Data for the Co2+-substituted and Ni2+-substituted proteins show that the metal ion is coordinated by three histidine residues; and the NMR characteristics of the Ni2+-substituted protein show that two of the histidines are coordinated through their N(epsilon2) atoms and one via its N(delta1). Furthermore, the NMR spectrum of the Ni2+-substituted protein is perturbed by the presence of phosphate, consistent with an X-ray structure showing that phosphate is coordinated to bound Ni2+, and by a change in pH, consistent with an ionisable group at the metal centre with a pKa of 7.9. Binding of an inhibitor protein to the DNase does not perturb the resonances of the metal site, suggesting there is no substantial conformation change of the DNase HNH motif on inhibitor binding. 1H-15N NMR data for the Zn2+-substituted DNase show that this protein, like the metal-free DNase, exists as two conformers with different 1H-15N correlation NMR spectra, and that the binding of Zn2+ does not significantly perturb the spectra, and hence structures, of these conformers beyond the HNH motif region.
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Affiliation(s)
- J P Hannan
- School of Biological Sciences, University of East Anglia, Norwich, UK
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Hannan JP, Busch JL, James R, Thomson AJ, Moore GR, Davy SL. Slow formation of [3Fe-4S](1+) clusters in mutant forms of Desulfovibrio africanus ferredoxin III. FEBS Lett 2000; 468:161-5. [PMID: 10692579 DOI: 10.1016/s0014-5793(00)01210-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Desulfovibrio africanus ferredoxin III (Da FdIII) readily interconverts between a 7Fe and an 8Fe form with Asp-14 believed to provide a cluster ligand in the latter form. To investigate the factors important for cluster interconversion in Fe/S cluster-containing proteins we have studied two variants of Da FdIII produced by site-directed mutagenesis, Asp14Glu and Asp14His, with cluster incorporation performed in vitro. Characterisation of these proteins by UV/visible, EPR and (1)H NMR spectroscopies revealed that the formation of the stable 7Fe form of these proteins takes some time to occur. Evidence is presented which indicates the [4Fe-4S](2+) cluster is incorporated prior to the [3Fe-4S](1+) cluster.
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Affiliation(s)
- J P Hannan
- School of Chemical Sciences, University of East Anglia, Norwich Research Park, Norwich, UK
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Hannan JP, Whittaker SB, Davy SL, Kühlmann UC, Pommer AJ, Hemmings AM, James R, Kleanthous C, Moore GR. NMR study of Ni2+ binding to the H-N-H endonuclease domain of colicin E9. Protein Sci 1999; 8:1711-3. [PMID: 10452617 PMCID: PMC2144424 DOI: 10.1110/ps.8.8.1711] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Ni2+ affinity columns are widely used for protein purification, but they carry the risk that Ni2+ ions may bind to the protein, either adventitiously or at a physiologically important site. Dialysis against ethylenediaminetetraacetic acid (EDTA) is normally used to remove metal ions bound adventitiously to proteins; however, this approach does not always work. Here we report that a bacterial endonuclease, the DNase domain of colicin E9, binds Ni2+ acquired from Ni2+ affinity columns, and appears to bind [Ni(EDTA)(H2O)n]2- at low ionic strength. NMR was used to detect the presence of both Ni2+ coordinated to amino acid side chains and [Ni(EDTA)(H2O)N]2-. Dialysis against > or =0.2 M NaCl was required to remove the [Ni(EDTA)(H2O)n]2-. The NMR procedure we have used to characterize the presence of Ni2+ and [Ni(EDTA)(H2O)n]2- should be applicable to other proteins where there is the possibility of binding paramagnetic metal ions that are present to expedite protein purification. In the present case, the binding of Ni2+ seems likely to be physiologically relevant, and the NMR data complement recent X-ray crystallographic evidence concerning the number of histidine ligands to bound Ni2+.
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Affiliation(s)
- J P Hannan
- School of Chemical Sciences, University of East Anglia, Norwich, United Kingdom
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Hannan JP, Davy SL, Moore GR, Eady RR, Andrew CR. Effect of nickel(II) substitution on the resonance Raman and NMR spectra of Alcaligenes xylosoxidans azurin II: implications for axial-ligand bonding interactions in cupredoxin active sites. J Biol Inorg Chem 1998. [DOI: 10.1007/s007750050233] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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