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Haddad G, Lorenzen JM, Ma H, de Haan N, Seeger H, Zaghrini C, Brandt S, Kölling M, Wegmann U, Kiss B, Pál G, Gál P, Wüthrich RP, Wuhrer M, Beck LH, Salant DJ, Lambeau G, Kistler AD. Altered glycosylation of IgG4 promotes lectin complement pathway activation in anti-PLA2R1-associated membranous nephropathy. J Clin Invest 2021; 131:140453. [PMID: 33351779 DOI: 10.1172/jci140453] [Citation(s) in RCA: 83] [Impact Index Per Article: 27.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Accepted: 12/16/2020] [Indexed: 12/19/2022] Open
Abstract
Primary membranous nephropathy (pMN) is a leading cause of nephrotic syndrome in adults. In most cases, this autoimmune kidney disease is associated with autoantibodies against the M-type phospholipase A2 receptor (PLA2R1) expressed on kidney podocytes, but the mechanisms leading to glomerular damage remain elusive. Here, we developed a cell culture model using human podocytes and found that anti-PLA2R1-positive pMN patient sera or isolated IgG4, but not IgG4-depleted sera, induced proteolysis of the 2 essential podocyte proteins synaptopodin and NEPH1 in the presence of complement, resulting in perturbations of the podocyte cytoskeleton. Specific blockade of the lectin pathway prevented degradation of synaptopodin and NEPH1. Anti-PLA2R1 IgG4 directly bound mannose-binding lectin in a glycosylation-dependent manner. In a cohort of pMN patients, we identified increased levels of galactose-deficient IgG4, which correlated with anti-PLA2R1 titers and podocyte damage induced by patient sera. Assembly of the terminal C5b-9 complement complex and activation of the complement receptors C3aR1 or C5aR1 were required to induce proteolysis of synaptopodin and NEPH1 by 2 distinct proteolytic pathways mediated by cysteine and aspartic proteinases, respectively. Together, these results demonstrated a mechanism by which aberrantly glycosylated IgG4 activated the lectin pathway and induced podocyte injury in primary membranous nephropathy.
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Affiliation(s)
- George Haddad
- Institute of Physiology, University of Zurich, Switzerland.,Division of Nephrology, University Hospital of Zurich, Switzerland
| | - Johan M Lorenzen
- Institute of Physiology, University of Zurich, Switzerland.,Division of Nephrology, University Hospital of Zurich, Switzerland
| | - Hong Ma
- Department of Medicine, Boston University School of Medicine, Boston, Massachusetts, USA
| | - Noortje de Haan
- Center for Proteomics and Metabolomics, Leiden University Medical Center, Netherlands
| | - Harald Seeger
- Institute of Physiology, University of Zurich, Switzerland.,Division of Nephrology, University Hospital of Zurich, Switzerland
| | - Christelle Zaghrini
- Université Côte d'Azur, CNRS, Institut de Pharmacologie Moléculaire et Cellulaire, Valbonne Sophia Antipolis, France
| | - Simone Brandt
- Institute of Pathology, University Hospital of Zurich, Switzerland
| | - Malte Kölling
- Institute of Physiology, University of Zurich, Switzerland
| | - Urs Wegmann
- Institute of Physiology, University of Zurich, Switzerland
| | - Bence Kiss
- Department of Biochemistry, Eötvös Loránd University, Budapest, Hungary
| | - Gábor Pál
- Department of Biochemistry, Eötvös Loránd University, Budapest, Hungary
| | - Péter Gál
- Institute of Enzymology, Research Centre for Natural Sciences, Budapest, Hungary
| | - Rudolf P Wüthrich
- Institute of Physiology, University of Zurich, Switzerland.,Division of Nephrology, University Hospital of Zurich, Switzerland
| | - Manfred Wuhrer
- Center for Proteomics and Metabolomics, Leiden University Medical Center, Netherlands
| | - Laurence H Beck
- Department of Medicine, Boston University School of Medicine, Boston, Massachusetts, USA
| | - David J Salant
- Department of Medicine, Boston University School of Medicine, Boston, Massachusetts, USA
| | - Gérard Lambeau
- Université Côte d'Azur, CNRS, Institut de Pharmacologie Moléculaire et Cellulaire, Valbonne Sophia Antipolis, France
| | - Andreas D Kistler
- Institute of Physiology, University of Zurich, Switzerland.,Division of Nephrology, University Hospital of Zurich, Switzerland.,Department of Medicine, Cantonal Hospital Frauenfeld, Switzerland
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2
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Zarantonello A, Pedersen H, Laursen NS, Andersen GR. Nanobodies Provide Insight into the Molecular Mechanisms of the Complement Cascade and Offer New Therapeutic Strategies. Biomolecules 2021; 11:biom11020298. [PMID: 33671302 PMCID: PMC7922070 DOI: 10.3390/biom11020298] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Revised: 02/10/2021] [Accepted: 02/11/2021] [Indexed: 01/22/2023] Open
Abstract
The complement system is part of the innate immune response, where it provides immediate protection from infectious agents and plays a fundamental role in homeostasis. Complement dysregulation occurs in several diseases, where the tightly regulated proteolytic cascade turns offensive. Prominent examples are atypical hemolytic uremic syndrome, paroxysmal nocturnal hemoglobinuria and Alzheimer’s disease. Therapeutic intervention targeting complement activation may allow treatment of such debilitating diseases. In this review, we describe a panel of complement targeting nanobodies that allow modulation at different steps of the proteolytic cascade, from the activation of the C1 complex in the classical pathway to formation of the C5 convertase in the terminal pathway. Thorough structural and functional characterization has provided a deep mechanistic understanding of the mode of inhibition for each of the nanobodies. These complement specific nanobodies are novel powerful probes for basic research and offer new opportunities for in vivo complement modulation.
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Affiliation(s)
- Alessandra Zarantonello
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus, Denmark; (A.Z.); (H.P.)
| | - Henrik Pedersen
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus, Denmark; (A.Z.); (H.P.)
| | - Nick S. Laursen
- Department of Biomedicine, Aarhus University, 8000 Aarhus, Denmark;
| | - Gregers R. Andersen
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus, Denmark; (A.Z.); (H.P.)
- Correspondence: ; Tel.: +45-30256646
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3
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Cao HY, Li D, Wang YP, Lu HX, Sun J, Li HB. Clinical significance of reduced expression of lncRNA TUG1 in the peripheral blood of systemic lupus erythematosus patients. Int J Rheum Dis 2020; 23:428-434. [PMID: 31944629 DOI: 10.1111/1756-185x.13786] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Revised: 10/17/2019] [Accepted: 12/17/2019] [Indexed: 11/30/2022]
Abstract
OBJECTIVE To investigate the expression and clinical significance of long non-coding RNA taurine up-regulated gene 1 (lncRNA TUG1) in the peripheral blood of systemic lupus erythematosus (SLE) patients. METHODS With the peripheral blood mononuclear cells (PBMCs: T-cells, B-cells and monocytes) collected from SLE patients and healthy controls, TUG1 expression was determined to identify the correlation with the clinicopathological features of SLE patients. Thereby, the diagnostic value of TUG1 expression in diagnosis of SLE was evaluated by receiver operating characteristic (ROC) curve analysis. RESULTS As compared to healthy controls, SLE patients manifested a lower expression of TUG1 in PBMCs, which was further decreased in SLE patients with lupus nephritis (P < .05). The lowest level of TUG1 was found in monocytes, rather than T-cells or B-cells (P < .05). Negative correlations were identified between TUG1 levels and SLE Disease Activity Index score (r = -.904, P < .001), erythrocyte sedimentation rate (r = -.779, P < .001), disease duration (r = -.503, P < .001) and 24-hour urinary protein (r = -.807, P < .001). Complement C3 levels were positively associated with TUG1 expression (r = .817, P < .001). In addition, the area under the ROC curve of diagnostic efficiency for SLE based on TUG1 was 0.982, and 0.930 for SLE with lupus nephritis. CONCLUSIONS The levels of lncRNA TUG1 was markedly lower in the SLE patients, which was more obvious in SLE patients with lupus nephritis, and thus, it could be a promising clinical diagnostic tool for SLE patients or SLE patients with lupus nephritis.
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Affiliation(s)
- Hai-Yu Cao
- Department of Dermatology, The First Hospital of Shijiazhuang City, Shijiazhuang, China
| | - Dong Li
- Department of Dermatology, Affiliated Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yun-Peng Wang
- Department of General Medicine, The Third Affiliated Hospital of Hebei Medical University, Shijiazhuang, China
| | - Hui-Xiu Lu
- Department of Dermatology, The First Hospital of Shijiazhuang City, Shijiazhuang, China
| | - Jing Sun
- Department of Dermatology, The First Hospital of Shijiazhuang City, Shijiazhuang, China
| | - Hai-Bin Li
- Department of General Medicine, The Third Affiliated Hospital of Hebei Medical University, Shijiazhuang, China
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Nan R, Furze CM, Wright DW, Gor J, Wallis R, Perkins SJ. Flexibility in Mannan-Binding Lectin-Associated Serine Proteases-1 and -2 Provides Insight on Lectin Pathway Activation. Structure 2017; 25:364-375. [PMID: 28111019 PMCID: PMC5300068 DOI: 10.1016/j.str.2016.12.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Revised: 12/08/2016] [Accepted: 12/21/2016] [Indexed: 01/19/2023]
Abstract
The lectin pathway of complement is activated by complexes comprising a recognition component (mannose-binding lectin, serum ficolins, collectin-LK or collectin-K1) and a serine protease (MASP-1 or MASP-2). MASP-1 activates MASP-2, and MASP-2 cleaves C4 and C4b-bound C2. To clarify activation, new crystal structures of Ca2+-bound MASP dimers were determined, together with their solution structures from X-ray scattering, analytical ultracentrifugation, and atomistic modeling. Solution structures of the CUB1-EGF-CUB2 dimer of each MASP indicate that the two CUB2 domains were tilted by as much as 90° compared with the crystal structures, indicating considerable flexibility at the EGF-CUB2 junction. Solution structures of the full-length MASP dimers in their zymogen and activated forms revealed similar structures that were much more bent than anticipated from crystal structures. We conclude that MASP-1 and MASP-2 are flexible at multiple sites and that this flexibility may permit both intra- and inter-complex activation.
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Affiliation(s)
- Ruodan Nan
- Department of Structural and Molecular Biology, Division of Biosciences, University College London, Darwin Building, Gower Street, London WC1E 6BT, UK
| | - Christopher M Furze
- Departments of Infection, Immunity and Inflammation and Molecular Cell Biology, University of Leicester, University Road, Leicester, LE1 9HN, UK
| | - David W Wright
- Department of Structural and Molecular Biology, Division of Biosciences, University College London, Darwin Building, Gower Street, London WC1E 6BT, UK
| | - Jayesh Gor
- Department of Structural and Molecular Biology, Division of Biosciences, University College London, Darwin Building, Gower Street, London WC1E 6BT, UK
| | - Russell Wallis
- Departments of Infection, Immunity and Inflammation and Molecular Cell Biology, University of Leicester, University Road, Leicester, LE1 9HN, UK
| | - Stephen J Perkins
- Department of Structural and Molecular Biology, Division of Biosciences, University College London, Darwin Building, Gower Street, London WC1E 6BT, UK.
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5
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Jacobsen JN, Andersen AS, Sonnested MK, Laursen I, Jorgensen B, Krogfelt KA. Investigating the humoral immune response in chronic venous leg ulcer patients colonised with Pseudomonas aeruginosa. Int Wound J 2010; 8:33-43. [PMID: 21091636 DOI: 10.1111/j.1742-481x.2010.00741.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The ability to manage the bioburden in chronic wounds is most likely coupled to the humoral immune response of the patient. We analysed markers of systemic immune response in patients with chronic venous leg ulcers (CVLUs) colonised (no-systemic infection) with the opportunistic pathogen Pseudomonas aeruginosa. Sera from 44 clinically non infected patients with CVLUs were analysed for total IgM and IgG isotype 1-4, complement C3, mannose-binding lectin (MBL), interleukin (IL)-6, C-reactive protein (CRP) and specific anti-P. aeruginosa antibodies against exotoxin A, elastase and alkaline phosphatase. Concentrations of IL-6 versus CRP intercorrelated (β = 2.43 95% CI (1.34-4.34)), but were independent of P. aeruginosa colonisation. MBL deficiency (MBL < 500 ng/ml) correlated to high serum levels of IgG(1) (P = 0.038) consistent with a compensatory mechanism, but not related to presence of P. aeruginosa in the ulcers. Twenty-four patients (54.5%) were culture positive for P. aeruginosa, also conferring significantly high serum levels of complement C3 (P = 0.014), but only two of these had positive titres for antibodies against exotoxin A. All patient sera were negative for antibodies against elastase and alkaline phosphatase. Fluorescent in situ hybridization analysis on randomly selected culture-positive patients could not establish unambiguous presence of P. aeruginosa biofilms in the ulcers. A multiple regression model showed P. aeruginosa and systemic CRP as significant factors in deterioration of ulcer healing rate.
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Affiliation(s)
- Jasper N Jacobsen
- Department of Microbiological Surveillance and Research, Statens Serum Institut, Copenhagen S, Denmark
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6
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Wallis R, Mitchell DA, Schmid R, Schwaeble WJ, Keeble AH. Paths reunited: Initiation of the classical and lectin pathways of complement activation. Immunobiology 2009; 215:1-11. [PMID: 19783065 PMCID: PMC2824237 DOI: 10.1016/j.imbio.2009.08.006] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2009] [Accepted: 08/22/2009] [Indexed: 12/16/2022]
Abstract
Understanding the structural organisation and mode of action of the initiating complex of the classical pathway of complement activation (C1) has been a central goal in complement biology since its isolation almost 50 years ago. Nevertheless, knowledge is still incomplete, especially with regard to the interactions between its subcomponents C1q, C1r and C1s that trigger activation upon binding to a microbial target. Recent studies have provided new insights into these interactions, and have revealed unexpected parallels with initiating complexes of the lectin pathway of complement: MBL-MASP and ficolin-MASP. Here, we develop and expand these concepts and delineate their implications towards the key aspects of complement activation via the classical and lectin pathways.
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Affiliation(s)
- Russell Wallis
- Department of Infection, Immunity and Inflammation, University of Leicester, UK.
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7
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Thiel S, Kolev M, Degn S, Steffensen R, Hansen AG, Ruseva M, Jensenius JC. Polymorphisms in mannan-binding lectin (MBL)-associated serine protease 2 affect stability, binding to MBL, and enzymatic activity. THE JOURNAL OF IMMUNOLOGY 2009; 182:2939-47. [PMID: 19234189 DOI: 10.4049/jimmunol.0802053] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Mannan-binding lectin-associated serine protease 2 (MASP-2) is an enzyme of the innate immune system. MASP-2 forms complexes with the pattern recognition molecules mannan-binding lectin (MBL), H-ficolin, L-ficolin, or M-ficolin, and is activated when one of these proteins recognizes microorganisms and subsequently cleaves complement factors C4 and C2, thus initiating the activation of the complement system. Missense polymorphisms of MASP-2 exist in different ethnic populations. To further characterize the nature of these, we have produced and characterized rMASP-2s representing the following naturally occurring polymorphisms: R99Q, D120G, P126L, H155R, 156_159dupCHNH (CHNHdup), V377A, and R439H. Only very low levels of CHNHdup were secreted from the cells, whereas quantities similar to wild-type MASP-2 were found intracellularly, indicating that this mutation results in a misfolded protein. We found that D120G and CHNHdup could not associate with MBL, whereas R99Q, P126L, H155R, V377A, R439H, and wild-type MASP-2 bound equally well to MBL. Accordingly, when D120G and CHNHdup were mixed with MBL, no activation of complement factor C4 was observed, whereas R99Q, P126L, and V377A cleaved C4 with an activity comparable to wild-type MASP-2 and H155R slightly better. In contrast, the R439H variant was deficient in this process despite its normal binding to MBL. This variant was also not able to autoactivate in the presence of MBL and mannan. We find the R439H variant is common in Sub-Saharan Africans with a gene frequency of 10%. Our results indicate that individuals with different types of MASP-2 defects may be identified through genotyping.
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Affiliation(s)
- Steffen Thiel
- Department of Medical Microbiology and Immunology, University of Aarhus, Aarhus, Denmark.
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8
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Rawal N, Rajagopalan R, Salvi VP. Activation of complement component C5: comparison of C5 convertases of the lectin pathway and the classical pathway of complement. J Biol Chem 2008; 283:7853-63. [PMID: 18204047 DOI: 10.1074/jbc.m707591200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Although the initiating complex of lectin pathway (called M1 in this study) generates C3/C5 convertases similar to those assembled by the initiating complex (C1) of the classical pathway, activation of complement component C5 via the lectin pathway has not been examined. In the present study kinetic analysis of lectin pathway C3/C5 convertases assembled on two surfaces (zymosan and sheep erythrocytes coated with mannan (E(Man))) revealed that the convertases (ZymM1,C4b,C2a and E(Man)M1,C4b,C2a) exhibited a similar but weak affinity for the substrate, C5 indicated by a high K(m) (2.73-6.88 microm). Very high affinity C5 convertases were generated when the low affinity C3/C5 convertases were allowed to deposit C3b by cleaving native C3. These C3b-containing convertases exhibited K(m) (0.0086-0.0075 microm) well below the normal concentration of C5 in blood (0.37 microm). Although kinetic parameters, K(m) and k(cat), of the lectin pathway C3/C5 convertases were similar to those reported for classical pathway C3/C5 convertases, studies on the ability of C4b to bind C2 indicated that every C4b deposited on zymosan or E(Man) was capable of forming a convertase. These findings differ from those reported for the classical pathway C3/C5 convertase, where only one of four C4b molecules deposited formed a convertase. The potential for four times more amplification via the lectin pathway than the classical pathway in the generation of C3/C5 convertases and production of pro-inflammatory products, such as C3a, C4a, and C5a, implies that activation of complement via the lectin pathway might be a more prominent contributor to the pathology of inflammatory reactions.
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Affiliation(s)
- Nenoo Rawal
- Department of Biochemistry, University of Texas Health Science Center, Tyler, Texas 75708, USA.
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9
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Ng PML, Le Saux A, Lee CM, Tan NS, Lu J, Thiel S, Ho B, Ding JL. C-reactive protein collaborates with plasma lectins to boost immune response against bacteria. EMBO J 2007; 26:3431-40. [PMID: 17581635 PMCID: PMC1933394 DOI: 10.1038/sj.emboj.7601762] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2006] [Accepted: 05/24/2007] [Indexed: 01/15/2023] Open
Abstract
Although human C-reactive protein (CRP) becomes upregulated during septicemia, its role remains unclear, since purified CRP showed no binding to many common pathogens. Contrary to previous findings, we show that purified human CRP (hCRP) binds to Salmonella enterica, and that binding is enhanced in the presence of plasma factors. In the horseshoe crab, Carcinoscorpius rotundicauda, CRP is a major hemolymph protein. Incubation of hemolymph with a range of bacteria resulted in CRP binding to all the bacteria tested. Lipopolysaccharide-affinity chromatography of the hemolymph co-purified CRP, galactose-binding protein (GBP) and carcinolectin-5 (CL5). Yeast two-hybrid and pull-down assays suggested that these pattern recognition receptors (PRRs) form pathogen recognition complexes. We show the conservation of PRR crosstalk in humans, whereby hCRP interacts with ficolin (CL5 homologue). This interaction stabilizes CRP binding to bacteria and activates the lectin-mediated complement pathway. We propose that CRP does not act alone but collaborates with other plasma PRRs to form stable pathogen recognition complexes when targeting a wide range of bacteria for destruction.
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Affiliation(s)
- Patricia M L Ng
- Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore
| | - Agnès Le Saux
- Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore
| | - Chia M Lee
- Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore
| | - Nguan S Tan
- School of Biological Sciences, Nanyang Technological University, Singapore
| | - Jinhua Lu
- Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Steffen Thiel
- Department of Medical Microbiology and Immunology, Wilhelm Meyers Allé, Bartholin Building, University of Aarhus, Aarhus, Denmark
| | - Bow Ho
- Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- These authors contributed equally to this work
| | - Jeak L Ding
- Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore
- These authors contributed equally to this work
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10
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Wallis R, Dodds AW, Mitchell DA, Sim RB, Reid KBM, Schwaeble WJ. Molecular Interactions between MASP-2, C4, and C2 and Their Activation Fragments Leading to Complement Activation via the Lectin Pathway. J Biol Chem 2007; 282:7844-51. [PMID: 17204478 DOI: 10.1074/jbc.m606326200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Activation of component C3 is central to the pathways of complement and leads directly to neutralization of pathogens and stimulation of adaptive immune responses. The convertases that catalyze this reaction assemble from fragments of complement components via multistep reactions. In the lectin pathway, mannose-binding lectin (MBL) and ficolins bind to pathogens and activate MBL-associated serine protease-2 (MASP-2). MASP-2 cleaves C4 releasing C4a and generating C4b, which attaches covalently to the pathogen surface upon exposure of its reactive thioester. C2 binds to C4b and is also cleaved by MASP-2 to form the C3 convertase (C4b2a). To understand how this complex process is coordinated, we have analyzed the interactions between MASP-2, C4, C2, and their activation fragments and have compared MASP-2-catalyzed cleavage of C4b2 and C2. The data show that C2 binds tightly to C4b but not to C4, implying that C4 and C2 do not circulate as preformed complexes but that C2 is recruited only after prior activation of C4. Following cleavage of C4, C4b still binds to MASP-2 (KD approximately 0.6 microM) and dissociates relatively slowly (koff approximately 0.06 s-1) compared with the half-life of the thioester (<or=0.7 s) (Sepp, A., Dodds, A. W., Anderson, M. J., Campbell, R. D., Willis, A. C., and Law, S. K. (1993) Protein Sci. 2, 706-716). We propose that the C4b.MASP-2 interaction favors attachment of C4b near to the activating MBL.MASP complex on the bacterial surface so that, following recruitment of C2, the proximity of enzyme and substrate (C4b2) combined with more favorable reaction kinetics drive the formation of the C3 convertase, promoting complement activation.
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Affiliation(s)
- Russell Wallis
- Department of Infection, Immunity, and Inflammation, University of Leicester, Leicester LE1 9HN, United Kingdom.
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11
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Abstract
Immunoglobulin A (IgA) is the most enigmatic of immunoglobulins. It is by far the most abundant of human Igs, being present in the blood plasma at concentrations approximating 2–3mg/mL, as well as the dominant isotype in most secretions where its output amounts to some 5–8g/day in adults. Furthermore, its evolutionary origins appear to precede the synapsid– diapsid divergence in tetrapod phylogeny (>300 million years ago) because it is present in both mammals and birds and therefore possibly also in reptiles (reviewed in Peppard et al., 2005); an IgA-like molecule has now been identified in a lizard (Deza et al., 2007).
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12
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Rooijakkers SHM, Ruyken M, Roos A, Daha MR, Presanis JS, Sim RB, van Wamel WJB, van Kessel KPM, van Strijp JAG. Immune evasion by a staphylococcal complement inhibitor that acts on C3 convertases. Nat Immunol 2005; 6:920-7. [PMID: 16086019 DOI: 10.1038/ni1235] [Citation(s) in RCA: 299] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2005] [Accepted: 06/23/2005] [Indexed: 01/13/2023]
Abstract
The complement system is pivotal in host defense but also contributes to tissue injury in several diseases. The assembly of C3 convertases (C4b2a and C3bBb) is a prerequisite for complement activation. The convertases catalyze C3b deposition on activator surfaces. Here we describe the identification of staphylococcal complement inhibitor, an excreted 9.8-kilodalton protein that blocks human complement by specific interaction with C4b2a and C3bBb. Staphylococcal complement inhibitor bound and stabilized C3 convertases, interfering with additional C3b deposition through the classical, lectin and alternative complement pathways. This led to a substantial decrease in phagocytosis and killing of Staphylococcus aureus by human neutrophils. As a highly active and small soluble protein that acts exclusively on surfaces, staphylococcal complement inhibitor may represent a promising anti-inflammatory molecule.
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Affiliation(s)
- Suzan H M Rooijakkers
- Eijkman Winkler Institute, University Medical Center Utrecht, G04.614, 3584 CX Utrecht, The Netherlands.
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Pellegrini-Masini A, Bentz AI, Johns IC, Parsons CS, Beech J, Whitlock RH, Flaminio MJBF. Common variable immunodeficiency in three horses with presumptive bacterial meningitis. J Am Vet Med Assoc 2005; 227:114-22, 87. [PMID: 16013546 DOI: 10.2460/javma.2005.227.114] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Three adult horses were evaluated for signs of musculoskeletal pain, dullness, ataxia, and seizures. A diagnosis of bacterial meningitis was made on the basis of results of CSF analysis. Because primary bacterial meningitis is so rare in adult horses without any history of generalized sepsis or trauma, immune function testing was pursued. Flow cytometric phenotyping of peripheral blood lymphocytes was performed, and proliferation of peripheral blood lymphocytes in response to concanavalin A, phytohemagglutinin, pokeweed mitogen, and lipopolysaccharide was determined. Serum IgA, IgM, and IgG concentrations were measured by means of radial immunodiffusion, and serum concentrations of IgG isotypes were assessed with a capture antibody ELISA. Serum tetanus antibody concentrations were measured before and 1 month after tetanus toxoid administration. Phagocytosis and oxidative burst activity of isolated peripheral blood phagocytes were evaluated by means of simultaneous flow cytometric analysis. Persistent B-cell lymphopenia, hypogammaglobulinemia, and abnormal in vitro responses to mitogens were detected in all 3 horses, and a diagnosis of common variable immunodeficiency was made.
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Affiliation(s)
- Alessandra Pellegrini-Masini
- Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA 19348, USA
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