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Hor L, Pan J, Pike RN, Wijeyewickrema LC. Molecular Interactions Required for Activation of Complement Component C2 Include Exosites Located on the Serine Protease Domain of C1s and Mannose-Binding Lectin Associated Protease-2. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2024; 212:1172-1177. [PMID: 38372634 DOI: 10.4049/jimmunol.2300042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Accepted: 01/12/2024] [Indexed: 02/20/2024]
Abstract
The activation of the CP/LP C3 proconvertase complex is a key event in complement activation and involves cleavage of C4 and C2 by the C1s protease (classical pathway) or the mannose-binding lectin-associated serine protease (MASP)-2 (lectin pathway). Efficient cleavage of C4 by C1s and MASP-2 involves exosites on the complement control protein and serine protease (SP) domains of the proteases. The complement control protein domain exosite is not involved in cleavage of C2 by the proteases, but the role of an anion-binding exosite (ABE) on the SP domains of the proteases has (to our knowledge) never been investigated. In this study, we have shown that the ABE on the SP of both C1s and MASP-2 is crucial for efficient cleavage of C2, with mutant forms of the proteases greatly impaired in their rate of cleavage of C2. We have additionally shown that the site of binding for the ABE of the proteases is very likely to be located on the von Willebrand factor domain of C2, with the precise area differing between the enzymes: whereas C1s requires two anionic clusters on the von Willebrand factor domain to enact efficient cleavage of C2, MASP-2 apparently only requires one. These data provide (to our knowledge) new information about the molecular determinants for efficient activation of C2 by C1s and MASP-2. The enhanced view of the molecular events underlying the early stages of complement activation provides further possible intervention points for control of this activation that is involved in a number of inflammatory diseases.
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Affiliation(s)
- Lilian Hor
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, School of Agriculture, Biomedicine and Environment, La Trobe University, Melbourne, Victoria, Australia
- Australian Research Council Centre of Excellence in Advanced Molecular Imaging, La Trobe University, Melbourne, Victoria, Australia
| | - Jing Pan
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, School of Agriculture, Biomedicine and Environment, La Trobe University, Melbourne, Victoria, Australia
| | - Robert N Pike
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, School of Agriculture, Biomedicine and Environment, La Trobe University, Melbourne, Victoria, Australia
- Australian Research Council Centre of Excellence in Advanced Molecular Imaging, La Trobe University, Melbourne, Victoria, Australia
| | - Lakshmi C Wijeyewickrema
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, School of Agriculture, Biomedicine and Environment, La Trobe University, Melbourne, Victoria, Australia
- Australian Research Council Centre of Excellence in Advanced Molecular Imaging, La Trobe University, Melbourne, Victoria, Australia
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Garrigues RJ, Thomas S, Leong JM, Garcia BL. Outer surface lipoproteins from the Lyme disease spirochete exploit the molecular switch mechanism of the complement protease C1s. J Biol Chem 2022; 298:102557. [PMID: 36183830 PMCID: PMC9637899 DOI: 10.1016/j.jbc.2022.102557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Revised: 09/23/2022] [Accepted: 09/26/2022] [Indexed: 10/14/2022] Open
Abstract
Proteolytic cascades comprise several important physiological systems, including a primary arm of innate immunity called the complement cascade. To safeguard against complement-mediated attack, the etiologic agent of Lyme disease, Borreliella burgdorferi, produces numerous outer surface-localized lipoproteins that contribute to successful complement evasion. Recently, we discovered a pair of B. burgdorferi surface lipoproteins of the OspEF-related protein family-termed ElpB and ElpQ-that inhibit antibody-mediated complement activation. In this study, we investigate the molecular mechanism of ElpB and ElpQ complement inhibition using an array of biochemical and biophysical approaches. In vitro assays of complement activation show that an independently folded homologous C-terminal domain of each Elp protein maintains full complement inhibitory activity and selectively inhibits the classical pathway. Using binding assays and complement component C1s enzyme assays, we show that binding of Elp proteins to activated C1s blocks complement component C4 cleavage by competing with C1s-C4 binding without occluding the active site. C1s-mediated C4 cleavage is dependent on activation-induced binding sites, termed exosites. To test whether these exosites are involved in Elp-C1s binding, we performed site-directed mutagenesis, which showed that ElpB and ElpQ binding require C1s residues in the anion-binding exosite located on the serine protease domain of C1s. Based on these results, we propose a model whereby ElpB and ElpQ exploit activation-induced conformational changes that are normally important for C1s-mediated C4 cleavage. Our study expands the known complement evasion mechanisms of microbial pathogens and reveals a novel molecular mechanism for selective C1s inhibition by Lyme disease spirochetes.
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Zhang H, Huang T, Ren X, Fang X, Chen X, Wei H, Sun W, Wang Y. Integrated pan-cancer analysis of CSMD2 as a potential prognostic, diagnostic, and immune biomarker. Front Genet 2022; 13:918486. [PMID: 36061177 PMCID: PMC9428318 DOI: 10.3389/fgene.2022.918486] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Accepted: 07/06/2022] [Indexed: 11/17/2022] Open
Abstract
The protein encoded by CUB and Sushi Multiple Domains 2 (CSMD2) is likely involved in regulating the complement cascade reaction of the immune system. However, current scientific evidence on the comprehensive roles of CSMD2 in pan-cancer is relatively scarce. Therefore, in this study, we explored the transcriptional level of CSMD2 in pan-caner using TCGA, GEO, and International Cancer Genome Consortium databases. Receiver operating characteristic curve analysis was used to investigate the diagnostic efficacy of CSMD2. The Kaplan-Meier Plotter and Oncolnc were used to investigate the correlation between CSMD2 expression and prognosis. Additionally, we analyzed the correlation between epigenetic methylation and CSMD2 expression in various cancers based on UALCAN, as well as, the correlation between CSMD2 and tumor mutational burden (TMB), microsatellite instability (MSI), and tumor neoantigen burden (TNB) in tumors. TIMER2.0 database was employed to investigate the correlation between CSMD2 and immune cells in the tumor microenvironment and immune checkpoints. Based on TISIDB, the correlation between CSMD2 and MHC molecules and immunostimulators was analyzed. Ultimately, we observed with a pan-cancer analysis that CSMD2 was upregulated in most tumors and had moderate to high diagnostic efficiency, and that high expression was closely associated with poor prognosis in patients with tumors. Moreover, hypermethylation of CSMD2 promoter and high levels of m6A methylation regulators were also observed in most cancers. CSMD2 expression was negatively correlated with TMB and MSI in stomach adenocarcinoma (STAD) and stomach and esophageal carcinoma (STES), as well as with tumor mutational burden, microsatellite instability, and TNB in head-neck squamous cell carcinoma (HNSC). In most cancers, CSMD2 might be associated with immune evasion or immunosuppression, as deficient anti-tumor immunity and upregulation of immune checkpoints were also observed in this study. In conclusion, CSMD2 could serve as a promising prognostic, diagnostic and immune biomarker in pan-cancer.
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Affiliation(s)
- Huiyun Zhang
- The First Clinical Medical College, Lanzhou University, Lanzhou, China
- Department of Gastroenterology, The First Hospital of Lanzhou University, Lanzhou, China
- Key Laboratory for Gastrointestinal Diseases of Gansu Province, The First Hospital of Lanzhou University, Lanzhou, China
| | - Taobi Huang
- The First Clinical Medical College, Lanzhou University, Lanzhou, China
- Department of Gastroenterology, The First Hospital of Lanzhou University, Lanzhou, China
- Key Laboratory for Gastrointestinal Diseases of Gansu Province, The First Hospital of Lanzhou University, Lanzhou, China
| | - Xiangqing Ren
- The First Clinical Medical College, Lanzhou University, Lanzhou, China
- Department of Gastroenterology, The First Hospital of Lanzhou University, Lanzhou, China
- Key Laboratory for Gastrointestinal Diseases of Gansu Province, The First Hospital of Lanzhou University, Lanzhou, China
| | - Xidong Fang
- The First Clinical Medical College, Lanzhou University, Lanzhou, China
- Department of Gastroenterology, The First Hospital of Lanzhou University, Lanzhou, China
- Key Laboratory for Gastrointestinal Diseases of Gansu Province, The First Hospital of Lanzhou University, Lanzhou, China
| | - Xia Chen
- The First Clinical Medical College, Lanzhou University, Lanzhou, China
- Department of Gastroenterology, The First Hospital of Lanzhou University, Lanzhou, China
- Key Laboratory for Gastrointestinal Diseases of Gansu Province, The First Hospital of Lanzhou University, Lanzhou, China
| | - Hui Wei
- The First Clinical Medical College, Lanzhou University, Lanzhou, China
- Department of Gastroenterology, The First Hospital of Lanzhou University, Lanzhou, China
- Key Laboratory for Gastrointestinal Diseases of Gansu Province, The First Hospital of Lanzhou University, Lanzhou, China
| | - Weiming Sun
- Department of Endocrinology, The First Hospital of Lanzhou University, Lanzhou, China
| | - Yuping Wang
- Department of Gastroenterology, The First Hospital of Lanzhou University, Lanzhou, China
- Key Laboratory for Gastrointestinal Diseases of Gansu Province, The First Hospital of Lanzhou University, Lanzhou, China
- *Correspondence: Yuping Wang,
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Thielens NM, Gout E, Lacroix M, Reiser JB, Gaboriaud C. Analysis of the Ligand Recognition Specificities of Human Ficolins Using Surface Plasmon Resonance. Methods Mol Biol 2021; 2227:205-226. [PMID: 33847944 DOI: 10.1007/978-1-0716-1016-9_19] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Ficolins are innate immune recognition proteins involved in activation of the lectin complement pathway. These oligomeric lectin-like proteins are assembled from subunits consisting of a collagen-like triple helix and a trimeric fibrinogen-like recognition domain. In humans, three ficolins coexist: they differ in their ligand binding specificities, but share the capacity to associate with proteases through their collagen-like stalks and trigger complement activation. We describe methods to decipher the recognition specificities of ficolins, based on surface plasmon resonance, an optical technique allowing real-time and label-free monitoring of biomolecular interactions. This technique was mainly used to characterize and compare binding of the three recombinant full-length ficolins and of their isolated recognition domains to various immobilized BSA-glycoconjugates, acetylated BSA or biotinylated heparin. The avidity phenomenon that enhances the apparent affinity of interactions between oligomeric lectin-like proteins and the multivalent ligands is also discussed.
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Affiliation(s)
| | - Evelyne Gout
- Univ. Grenoble Alpes, CNRS, CEA, IBS, Grenoble, France
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Bally I, Dalonneau F, Chouquet A, Gröbner R, Amberger A, Kapferer-Seebacher I, Stoiber H, Zschocke J, Thielens NM, Rossi V, Gaboriaud C. Two Different Missense C1S Mutations, Associated to Periodontal Ehlers-Danlos Syndrome, Lead to Identical Molecular Outcomes. Front Immunol 2019; 10:2962. [PMID: 31921203 PMCID: PMC6930149 DOI: 10.3389/fimmu.2019.02962] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Accepted: 12/03/2019] [Indexed: 12/31/2022] Open
Abstract
Ehlers-Danlos syndromes (EDS) are clinically and genetically heterogeneous disorders characterized by soft connective tissue alteration like joint hypermobility and skin hyper-extensibility. We previously identified heterozygous missense mutations in the C1R and C1S genes, coding for the complement C1 proteases, in patients affected by periodontal EDS, a specific EDS subtype hallmarked by early severe periodontitis leading to premature loss of teeth and connective tissue alterations. Up to now, there is no clear molecular link relating the nominal role of the C1r and C1s proteases, which is to activate the classical complement pathway, to these heterogeneous symptoms of periodontal EDS syndrome. We aim therefore to elucidate the functional effect of these mutations, at the molecular and enzymatic levels. To explore the molecular consequences, a set of cell transfection experiments, recombinant protein purification, mass spectroscopy and N-terminal analyses have been performed. Focusing on the results obtained on two different C1S variants, namely p.Val316del and p.Cys294Arg, we show that HEK293-F cells stably transfected with the corresponding C1s variant plasmids, unexpectedly, do not secrete the full-length mutated C1s, but only a truncated Fg40 fragment of 40 kDa, produced at very low levels. Detailed analyses of the Fg40 fragments purified for the two C1s variants show that they are identical, which was also unexpected. This suggests that local misfolding of the CCP1 module containing the patient mutation exposes a novel cleavage site, between Lys353 and Cys354, which is not normally accessible. The mutation-induced Fg40 fragment contains the intact C-terminal serine protease domain but not the N-terminal domain mediating C1s interaction with the other C1 subunits, C1r, and C1q. Thus, Fg40 enzymatic activity escapes the normal physiological control of C1s activity within C1, potentially providing a loss-of-control. Comparative enzymatic analyses show that Fg40 retains the native esterolytic activity of C1s, as well as its cleavage efficiency toward the ancillary alarmin HMGB1 substrate, for example, whereas the nominal complement C4 activation cleavage is impaired. These new results open the way to further molecular explorations possibly involving subsidiary C1s targets.
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Affiliation(s)
- Isabelle Bally
- University Grenoble Alpes, CEA, CNRS, IBS, Grenoble, France
| | | | - Anne Chouquet
- University Grenoble Alpes, CEA, CNRS, IBS, Grenoble, France
| | - Rebekka Gröbner
- Division of Human Genetics, Institute of Human Genetics, Medical University Innsbruck, Innsbruck, Austria
| | - Albert Amberger
- Division of Human Genetics, Institute of Human Genetics, Medical University Innsbruck, Innsbruck, Austria
| | - Ines Kapferer-Seebacher
- Department for Operative and Restorative Dentistry, Medical University Innsbruck, Innsbruck, Austria
| | - Heribert Stoiber
- Institute of Virology, Medical University Innsbruck, Innsbruck, Austria
| | - Johannes Zschocke
- Division of Human Genetics, Institute of Human Genetics, Medical University Innsbruck, Innsbruck, Austria
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Wang Y, Sun M, Liu J, Liu Y, Jiang C, Zhu H, Wang W, Wang Y. FIBCD1 overexpression predicts poor prognosis in patients with hepatocellular carcinoma. Oncol Lett 2019; 19:795-804. [PMID: 31897196 PMCID: PMC6924150 DOI: 10.3892/ol.2019.11183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Accepted: 11/01/2019] [Indexed: 11/13/2022] Open
Abstract
Fibrinogen C domain-containing 1 (FIBCD1) is an acetyl-recognition receptor that affects the occurrence and development of certain tumors. However, the prognostic significance of FIBCD1 in hepatocellular carcinoma (HCC) remains unclear. This study aimed to explore FIBCD1 expression in HCC and to determine the prognostic value of FIBCD1 in patients with HCC. A total of 1,058 liver tissue samples with detailed and complete clinical information were collected, including 495 HCC samples. Tissue microarray immunohistochemistry analysis was used to evaluate FIBCD1 protein expression in the collected tissues. The Kaplan-Meier plotter online tool was used to investigate the association between FIBCD1 expression and prognosis of patients with HCC. Oncomine and the Gene Expression Profiling Interactive Analysis database were used for bioinformatics analysis of FIBCD1. Results showed that FIBCD1 expression was higher in HCC and was associated with tumor diameter (P=0.002), tumor number (P=0.001), tumor node metastasis stage (P<0.001), primary tumor (T; P<0.001), lymph node metastases (N; P=0.002), distant metastases (M; P=0.023), differentiation degree (P=0.003), vascular invasion (P<0.001) and liver cirrhosis (P=0.011). Patients with HCC and high FIBCD1 expression had worse overall survival than those with low FIBCD1 expression. High FIBCD1 expression (P<0.001), TNM stage (P=0.003), T (P<0.001), N (P=0.014), and vascular invasion (P<0.001) were independent prognostic factors in HCC. Hence, FIBCD1 may be a novel biomarker for prognosis evaluation of HCC.
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Affiliation(s)
- Yan Wang
- Department of Pathology, Affiliated Hospital of Nantong University, Nantong, Jiangsu 226001, P.R. China
| | - Mengjing Sun
- Department of Clinical Biobank, Affiliated Hospital of Nantong University, Nantong, Jiangsu 226001, P.R. China.,Department of Pathology, School of Medicine, Nantong University, Nantong, Jiangsu 226001, P.R. China
| | - Jibin Liu
- Department of Tumor Biobank, Nantong Tumor Hospital, Nantong, Jiangsu 226361, P.R. China
| | - Ying Liu
- Department of Pathology, Affiliated Hospital of Nantong University, Nantong, Jiangsu 226001, P.R. China
| | - Chunyi Jiang
- Department of Pathology, Affiliated Hospital of Nantong University, Nantong, Jiangsu 226001, P.R. China
| | - Huijun Zhu
- Department of Pathology, Affiliated Hospital of Nantong University, Nantong, Jiangsu 226001, P.R. China
| | - Wei Wang
- Department of Pathology, Affiliated Hospital of Nantong University, Nantong, Jiangsu 226001, P.R. China
| | - Yao Wang
- Department of General Surgery, Affiliated Hospital of Nantong University, Nantong, Jiangsu 226001, P.R. China
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Insights into IgM-mediated complement activation based on in situ structures of IgM-C1-C4b. Proc Natl Acad Sci U S A 2019; 116:11900-11905. [PMID: 31147461 PMCID: PMC6575175 DOI: 10.1073/pnas.1901841116] [Citation(s) in RCA: 90] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
IgM antibodies protect mammals against humoral microbial infection and mediate clearance of cellular debris. IgM activates the immune complement system only after binding to cell-surface antigens. Here we report the in situ 3D structures of surface-antigen–bound IgM antibodies in complex with both C1 and C4b complement components. The data indicate the structural arrangement of pentameric and hexameric IgM upon antigen binding, exposing the C1q-binding sites with both adopting hexagonal symmetry. The structures reveal the entire C1qr2s2 complex and elucidate several protein–protein interactions with C4b and IgM. Based on the structural data, we hypothesize a C1q-transmitted surface trigger that activates C1, leading to C4 cleavage and C4b deposition on membranes. Antigen binding by serum Ig-M (IgM) protects against microbial infections and helps to prevent autoimmunity, but causes life-threatening diseases when mistargeted. How antigen-bound IgM activates complement-immune responses remains unclear. We present cryoelectron tomography structures of IgM, C1, and C4b complexes formed on antigen-bearing lipid membranes by normal human serum at 4 °C. The IgM-C1-C4b complexes revealed C4b product release as the temperature-limiting step in complement activation. Both IgM hexamers and pentamers adopted hexagonal, dome-shaped structures with Fab pairs, dimerized by hinge domains, bound to surface antigens that support a platform of Fc regions. C1 binds IgM through widely spread C1q-collagen helices, with C1r proteases pointing outward and C1s bending downward and interacting with surface-attached C4b, which further interacts with the adjacent IgM-Fab2 and globular C1q-recognition unit. Based on these data, we present mechanistic models for antibody-mediated, C1q-transmitted activation of C1 and for C4b deposition, while further conformational rearrangements are required to form C3 convertases.
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Jiang C, Zhu J, Zhou P, Zhu H, Wang W, Jin Q, Li P. Overexpression of FIBCD1 Is Predictive of Poor Prognosis in Gastric Cancer. Am J Clin Pathol 2018; 149:474-483. [PMID: 29659669 DOI: 10.1093/ajcp/aqy013] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
OBJECTIVES Fibrinogen C domain containing 1 (FIBCD1) is a newly identified acetyl group recognition receptor. The aim of this study was to evaluate the prognostic significance of FIBCD1 in gastric cancer. METHODS This study included 706 samples, and the clinical data of all patients were recorded in detail. We studied messenger RNA (mRNA) and protein expression of FIBCD1 in cancerous and normal tissues by quantitative real-time polymerase chain reaction (n = 54) and tissue microarray immunohistochemistry analysis (n = 706), respectively. RESULTS mRNA and protein expression levels of FIBCD1 were significantly higher in gastric cancer than in normal tissues. High FIBCD1 protein level showed significant correlations with age (P = .011), TNM stage (P < .001), serum carcinoembryonic antigen (CEA) level (P = .002), and the expression of human epidermal growth factor receptor 2 (P < .001). Kaplan-Meier survival analysis revealed that patients with gastric cancer with high levels of FIBCD1 had a significantly shorter survival time than those with low expression levels. In univariate analysis, high FIBCD1 expression, older age, histologic type, differentiation, TNM stage, serum CEA, and serum CA19-9 level correlated with overall survival. Multivariate analysis suggested that FIBCD1 expression was an independent prognostic factor. CONCLUSIONS FIBCD1 may be a novel biomarker to evaluate the prognosis of gastric cancer.
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Affiliation(s)
- Chunyi Jiang
- Department of Pathology, Nantong, China
- Department of Clinical Bio-bank, Nantong, China
| | - Jinhong Zhu
- Department of Molecular Epidemiology Laboratory and Department of Laboratory Medicine, Harbin Medical University Cancer Hospital, Harbin, China
| | | | | | - Wei Wang
- Department of Pathology, Nantong, China
| | - Qin Jin
- Department of Pathology, Nantong, China
| | - Peng Li
- Department of General Surgery, Nantong University Affiliated Hospital, Nantong, China
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Moreau C, Bally I, Chouquet A, Bottazzi B, Ghebrehiwet B, Gaboriaud C, Thielens N. Structural and Functional Characterization of a Single-Chain Form of the Recognition Domain of Complement Protein C1q. Front Immunol 2016; 7:79. [PMID: 26973654 PMCID: PMC4774423 DOI: 10.3389/fimmu.2016.00079] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Accepted: 02/18/2016] [Indexed: 11/17/2022] Open
Abstract
Complement C1q is a soluble pattern recognition molecule comprising six heterotrimeric subunits assembled from three polypeptide chains (A–C). Each heterotrimer forms a collagen-like stem prolonged by a globular recognition domain. These recognition domains sense a wide variety of ligands, including pathogens and altered-self components. Ligand recognition is either direct or mediated by immunoglobulins or pentraxins. Multivalent binding of C1q to its targets triggers immune effector mechanisms mediated via its collagen-like stems. The induced immune response includes activation of the classical complement pathway and enhancement of the phagocytosis of the recognized target. We report here, the first production of a single-chain recombinant form of human C1q globular region (C1q-scGR). The three monomers have been linked in tandem to generate a single continuous polypeptide, based on a strategy previously used for adiponectin, a protein structurally related to C1q. The resulting C1q-scGR protein was produced at high yield in stably transfected 293-F mammalian cells. Recombinant C1q-scGR was correctly folded, as demonstrated by its X-ray crystal structure solved at a resolution of 1.35 Å. Its interaction properties were assessed by surface plasmon resonance analysis using the following physiological C1q ligands: the receptor for C1q globular heads, the long pentraxin PTX3, calreticulin, and heparin. The 3D structure and the binding properties of C1q-scGR were similar to those of the three-chain fragment generated by collagenase digestion of serum-derived C1q. Comparison of the interaction properties of the fragments with those of native C1q provided insights into the avidity component associated with the hexameric assembly of C1q. The interest of this functional recombinant form of the recognition domains of C1q in basic research and its potential biomedical applications are discussed.
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Affiliation(s)
- Christophe Moreau
- IBS, University of Grenoble Alpes, Grenoble, France; CNRS, IBS, Grenoble, France; IBS, CEA, Grenoble, France
| | - Isabelle Bally
- IBS, University of Grenoble Alpes, Grenoble, France; CNRS, IBS, Grenoble, France; IBS, CEA, Grenoble, France
| | - Anne Chouquet
- IBS, University of Grenoble Alpes, Grenoble, France; CNRS, IBS, Grenoble, France; IBS, CEA, Grenoble, France
| | - Barbara Bottazzi
- Immunopharmacology Laboratory, Humanitas Research Hospital , Rozzano , Italy
| | | | - Christine Gaboriaud
- IBS, University of Grenoble Alpes, Grenoble, France; CNRS, IBS, Grenoble, France; IBS, CEA, Grenoble, France
| | - Nicole Thielens
- IBS, University of Grenoble Alpes, Grenoble, France; CNRS, IBS, Grenoble, France; IBS, CEA, Grenoble, France
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10
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Gaboriaud C, Ling WL, Thielens NM, Bally I, Rossi V. Deciphering the fine details of c1 assembly and activation mechanisms: "mission impossible"? Front Immunol 2014; 5:565. [PMID: 25414705 PMCID: PMC4222235 DOI: 10.3389/fimmu.2014.00565] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Accepted: 10/22/2014] [Indexed: 01/05/2023] Open
Abstract
The classical complement pathway is initiated by the large (~800 kDa) and flexible multimeric C1 complex. Its catalytic function is triggered by the proteases hetero-tetramer C1r2s2, which is associated to the C1q sensing unit, a complex assembly of 18 chains built as a hexamer of heterotrimers. Initial pioneering studies gained insights into the main architectural principles of the C1 complex. A dissection strategy then provided the high-resolution structures of its main functional and/or structural building blocks, as well as structural details on some key protein–protein interactions. These past and current discoveries will be briefly summed up in order to address the question of what is still ill-defined. On a functional point of view, the main molecular determinants of C1 activation and its tight control will be delineated. The current perspective remains to decipher how C1 really works and is controlled in vivo, both in normal and pathological settings.
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Affiliation(s)
- Christine Gaboriaud
- Institut de Biologie Structurale, Université Grenoble Alpes , Grenoble , France ; CNRS, Institut de Biologie Structurale , Grenoble , France ; CEA, Institut de Biologie Structurale , Grenoble , France
| | - Wai Li Ling
- Institut de Biologie Structurale, Université Grenoble Alpes , Grenoble , France ; CNRS, Institut de Biologie Structurale , Grenoble , France ; CEA, Institut de Biologie Structurale , Grenoble , France
| | - Nicole M Thielens
- Institut de Biologie Structurale, Université Grenoble Alpes , Grenoble , France ; CNRS, Institut de Biologie Structurale , Grenoble , France ; CEA, Institut de Biologie Structurale , Grenoble , France
| | - Isabelle Bally
- Institut de Biologie Structurale, Université Grenoble Alpes , Grenoble , France ; CNRS, Institut de Biologie Structurale , Grenoble , France ; CEA, Institut de Biologie Structurale , Grenoble , France
| | - Véronique Rossi
- Institut de Biologie Structurale, Université Grenoble Alpes , Grenoble , France ; CNRS, Institut de Biologie Structurale , Grenoble , France ; CEA, Institut de Biologie Structurale , Grenoble , France
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Pike RN, Wijeyewickrema LC. The molecular switches controlling the interaction between complement proteases of the classical and lectin pathways and their substrates. Curr Opin Struct Biol 2013; 23:820-7. [DOI: 10.1016/j.sbi.2013.07.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Accepted: 07/24/2013] [Indexed: 11/29/2022]
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12
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Shrive AK, Moeller JB, Burns I, Paterson JM, Shaw AJ, Schlosser A, Sorensen GL, Greenhough TJ, Holmskov U. Crystal structure of the tetrameric fibrinogen-like recognition domain of fibrinogen C domain containing 1 (FIBCD1) protein. J Biol Chem 2013; 289:2880-7. [PMID: 24293368 PMCID: PMC3908420 DOI: 10.1074/jbc.m113.520577] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
The high resolution crystal structures of a recombinant fragment of the C-terminal fibrinogen-like recognition domain of FIBCD1, a vertebrate receptor that binds chitin, have been determined. The overall tetrameric structure shows similarity in structure and aggregation to the horseshoe crab innate immune protein tachylectin 5A. The high affinity ligand N-acetylmannosamine (ManNAc) binds in the S1 site, predominantly via the acetyl group with the oxygen and acetamide nitrogen hydrogen-bonded to the protein and the methyl group inserted into a hydrophobic pocket. The binding of the ManNAc pyranose ring differs markedly between the two independent subunits, but in all structures the binding of the N-acetyl group is conserved. In the native structure, a crystal contact results in one of the independent protomers binding the first GlcNAc of the Asn340N-linked glycan on the other independent protomer. In the ligand-bound structure this GlcNAc is replaced by the higher affinity ligand ManNAc. In addition, a sulfate ion has been modeled into the electron density at a location similar to the S3 binding site in L-ficolin, whereas in the native structure an acetate ion has been placed in the S1 N-acetyl binding site, and a sulfate ion has been placed adjacent to this site. These ion binding sites are ideally placed to receive the N-acetyl and sulfate groups of sulfated GalNAc residues of glycosaminoglycans such as chondroitin and dermatan sulfate. Together, these structures give insight into important determinants of ligand selectivity, demonstrating versatility in recognition and binding while maintaining conservation in N-acetyl and calcium binding.
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Affiliation(s)
- Annette K Shrive
- From the Research Institute of Science and Technology in Medicine, School of Life Sciences, Keele University, Staffordshire ST5 5BG, United Kingdom and
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The serine protease domain of MASP-3: enzymatic properties and crystal structure in complex with ecotin. PLoS One 2013; 8:e67962. [PMID: 23861840 PMCID: PMC3701661 DOI: 10.1371/journal.pone.0067962] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Accepted: 05/23/2013] [Indexed: 11/19/2022] Open
Abstract
Mannan-binding lectin (MBL), ficolins and collectin-11 are known to associate with three homologous modular proteases, the MBL-Associated Serine Proteases (MASPs). The crystal structures of the catalytic domains of MASP-1 and MASP-2 have been solved, but the structure of the corresponding domain of MASP-3 remains unknown. A link between mutations in the MASP1/3 gene and the rare autosomal recessive 3MC (Mingarelli, Malpuech, Michels and Carnevale,) syndrome, characterized by various developmental disorders, was discovered recently, revealing an unexpected important role of MASP-3 in early developmental processes. To gain a first insight into the enzymatic and structural properties of MASP-3, a recombinant form of its serine protease (SP) domain was produced and characterized. The amidolytic activity of this domain on fluorescent peptidyl-aminomethylcoumarin substrates was shown to be considerably lower than that of other members of the C1r/C1s/MASP family. The E. coli protease inhibitor ecotin bound to the SP domains of MASP-3 and MASP-2, whereas no significant interaction was detected with MASP-1, C1r and C1s. A tetrameric complex comprising an ecotin dimer and two MASP-3 SP domains was isolated and its crystal structure was solved and refined to 3.2 Å. Analysis of the ecotin/MASP-3 interfaces allows a better understanding of the differential reactivity of the C1r/C1s/MASP protease family members towards ecotin, and comparison of the MASP-3 SP domain structure with those of other trypsin-like proteases yields novel hypotheses accounting for its zymogen-like properties in vitro.
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14
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Perry AJ, Wijeyewickrema LC, Wilmann PG, Gunzburg MJ, D'Andrea L, Irving JA, Pang SS, Duncan RC, Wilce JA, Whisstock JC, Pike RN. A molecular switch governs the interaction between the human complement protease C1s and its substrate, complement C4. J Biol Chem 2013; 288:15821-9. [PMID: 23592783 DOI: 10.1074/jbc.m113.464545] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The complement system is an ancient innate immune defense pathway that plays a front line role in eliminating microbial pathogens. Recognition of foreign targets by antibodies drives sequential activation of two serine proteases, C1r and C1s, which reside within the complement Component 1 (C1) complex. Active C1s propagates the immune response through its ability to bind and cleave the effector molecule complement Component 4 (C4). Currently, the precise structural and biochemical basis for the control of the interaction between C1s and C4 is unclear. Here, using surface plasmon resonance, we show that the transition of the C1s zymogen to the active form is essential for C1s binding to C4. To understand this, we determined the crystal structure of a zymogen C1s construct (comprising two complement control protein (CCP) domains and the serine protease (SP) domain). These data reveal that two loops (492-499 and 573-580) in the zymogen serine protease domain adopt a conformation that would be predicted to sterically abrogate C4 binding. The transition from zymogen to active C1s repositions both loops such that they would be able to interact with sulfotyrosine residues on C4. The structure also shows the junction of the CCP1 and CCP2 domains of C1s for the first time, yielding valuable information about the exosite for C4 binding located at this position. Together, these data provide a structural explanation for the control of the interaction with C1s and C4 and, furthermore, point to alternative strategies for developing therapeutic approaches for controlling activation of the complement cascade.
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Affiliation(s)
- Andrew J Perry
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Melbourne, Victoria 3800, Australia
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15
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Jacquet M, Lacroix M, Ancelet S, Gout E, Gaboriaud C, Thielens NM, Rossi V. Deciphering complement receptor type 1 interactions with recognition proteins of the lectin complement pathway. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2013; 190:3721-31. [PMID: 23460739 DOI: 10.4049/jimmunol.1202451] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Complement receptor type 1 (CR1) is a membrane receptor expressed on a wide range of cells. It is involved in immune complex clearance, phagocytosis, and complement regulation. Its ectodomain is composed of 30 complement control protein (CCP) modules, organized into four long homologous repeats (A-D). In addition to its main ligands C3b and C4b, CR1 was reported to interact with C1q and mannan-binding lectin (MBL) likely through its C-terminal region (CCP22-30). To decipher the interaction of human CR1 with the recognition proteins of the lectin complement pathway, a recombinant fragment encompassing CCP22-30 was expressed in eukaryotic cells, and its interaction with human MBL and ficolins was investigated using surface plasmon resonance spectroscopy. MBL and L-ficolin were shown to interact with immobilized soluble CR1 and CR1 CCP22-30 with apparent dissociation constants in the nanomolar range, indicative of high affinity. The binding site for CR1 was located at or near the MBL-associated serine protease (MASP) binding site in the collagen stalks of MBL and L-ficolin, as shown by competition experiments with MASP-3. Accordingly, the mutation of an MBL conserved lysine residue essential for MASP binding (K55) abolished binding to soluble CR1 and CCP22-30. The CR1 binding site for MBL/ficolins was mapped to CCP24-25 of long homologous repeat D using deletion mutants. In conclusion, we show that ficolins are new CR1 ligands and propose that MBL/L-ficolin binding involves major ionic interactions between conserved lysine residues of their collagen stalks and surface exposed acidic residues located in CR1 CCP24 and/or CCP25.
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Affiliation(s)
- Mickaël Jacquet
- Commissariat à l'Energie Atomique, Institut de Biologie Structurale Jean-Pierre Ebel, 38027 Grenoble Cedex 1, France
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16
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The emerging role of complement lectin pathway in trypanosomatids: molecular bases in activation, genetic deficiencies, susceptibility to infection, and complement system-based therapeutics. ScientificWorldJournal 2013; 2013:675898. [PMID: 23533355 PMCID: PMC3595680 DOI: 10.1155/2013/675898] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Accepted: 01/01/2013] [Indexed: 12/21/2022] Open
Abstract
The innate immune system is evolutionary and ancient and is the pivotal line of the host defense system to protect against invading pathogens and abnormal self-derived components. Cellular and molecular components are involved in recognition and effector mechanisms for a successful innate immune response. The complement lectin pathway (CLP) was discovered in 1990. These new components at the complement world are very efficient. Mannan-binding lectin (MBL) and ficolin not only recognize many molecular patterns of pathogens rapidly to activate complement but also display several strategies to evade innate immunity. Many studies have shown a relation between the deficit of complement factors and susceptibility to infection. The recently discovered CLP was shown to be important in host defense against protozoan microbes. Although the recognition of pathogen-associated molecular patterns by MBL and Ficolins reveal efficient complement activations, an increase in deficiency of complement factors and diversity of parasite strategies of immune evasion demonstrate the unsuccessful effort to control the infection. In the present paper, we will discuss basic aspects of complement activation, the structure of the lectin pathway components, genetic deficiency of complement factors, and new therapeutic opportunities to target the complement system to control infection.
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Carroll S, Georgiou G. Antibody-mediates inhibition of human C1s and the classical complement pathway. Immunobiology 2013; 218:1041-8. [PMID: 23434433 DOI: 10.1016/j.imbio.2013.01.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Revised: 01/02/2013] [Accepted: 01/02/2013] [Indexed: 01/19/2023]
Abstract
Disregulation of complement activation plays a critical role in numerous inflammatory diseases and therefore, inhibition of the complement pathway is of great therapeutic interest. In the classical complement pathway, immune complexes formed by IgM, IgG1, IgG2 and IgG3 antibodies result in the activation of the C1s protease that in turn cleaves C4 and then C4-bound-C2 yielding the proteolytic fragments C4b and C2a which associate to form a C3 convertase enzyme. We report here the engineering of a potent human antibody inhibitor of C1s protease activity. Phage panning of a very large synthetic (F(AB)) antibody fragment library using a truncated version of C1s, comprising the second CCP domain and serine protease domain (CCP₂-SP) and expressed in insect cells, resulted in the isolation of a F(AB) that inhibited the catalytic activity of C1s. An affinity matured variant of the F(AB) format antibody displaying subnanomolar K(D) for C1s was shown to exhibit >80% inhibition of C2 processing at a 5:1 antibody:C1s molar ratio. We show that this engineered antibody, D.35, displays potent inhibition of complement deposition and lysis of Ramos cells by the anti-CD20 therapeutic antibody rituximab relative to the approved, but less-specific, human plasma-derived C1-inhibitor (CINRYZE). C1s inhibitory antibodies should be useful for delineating the role of the classical pathway in disease models and may hold promise as therapeutic agents.
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Affiliation(s)
- Sean Carroll
- Department of Chemical Engineering, University of Texas at Austin, Austin, TX, USA
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18
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Gál P, Dobó J, Beinrohr L, Pál G, Závodszky P. Inhibition of the Serine Proteases of the Complement System. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 735:23-40. [DOI: 10.1007/978-1-4614-4118-2_2] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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19
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Structural basis for activation of the complement system by component C4 cleavage. Proc Natl Acad Sci U S A 2012; 109:15425-30. [PMID: 22949645 DOI: 10.1073/pnas.1208031109] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
An essential aspect of innate immunity is recognition of molecular patterns on the surface of pathogens or altered self through the lectin and classical pathways, two of the three well-established activation pathways of the complement system. This recognition causes activation of the MASP-2 or the C1s serine proteases followed by cleavage of the protein C4. Here we present the crystal structures of the 203-kDa human C4 and the 245-kDa C4·MASP-2 substrate·enzyme complex. When C4 binds to MASP-2, substantial conformational changes in C4 are induced, and its scissile bond region becomes ordered and inserted into the protease catalytic site in a manner canonical to serine proteases. In MASP-2, an exosite located within the CCP domains recognizes the C4 C345C domain 60 Å from the scissile bond. Mutations in C4 and MASP-2 residues at the C345C-CCP interface inhibit the intermolecular interaction and C4 cleavage. The possible assembly of the huge in vivo enzyme-substrate complex consisting of glycan-bound mannan-binding lectin, MASP-2, and C4 is discussed. Our own and prior functional data suggest that C1s in the classical pathway of complement activated by, e.g., antigen-antibody complexes, also recognizes the C4 C345C domain through a CCP exosite. Our results provide a unified structural framework for understanding the early and essential step of C4 cleavage in the elimination of pathogens and altered self through two major pathways of complement activation.
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20
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Duncan RC, Mohlin F, Taleski D, Coetzer TH, Huntington JA, Payne RJ, Blom AM, Pike RN, Wijeyewickrema LC. Identification of a catalytic exosite for complement component C4 on the serine protease domain of C1s. THE JOURNAL OF IMMUNOLOGY 2012; 189:2365-73. [PMID: 22855709 DOI: 10.4049/jimmunol.1201085] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The classical pathway of complement is crucial to the immune system, but it also contributes to inflammatory diseases when dysregulated. Binding of the C1 complex to ligands activates the pathway by inducing autoactivation of associated C1r, after which C1r activates C1s. C1s cleaves complement component C4 and then C2 to cause full activation of the system. The interaction between C1s and C4 involves active site and exosite-mediated events, but the molecular details are unknown. In this study, we identified four positively charged amino acids on the serine protease domain that appear to form a catalytic exosite that is required for efficient cleavage of C4. These residues are coincidentally involved in coordinating a sulfate ion in the crystal structure of the protease. Together with other evidence, this pointed to the involvement of sulfate ions in the interaction with the C4 substrate, and we showed that the protease interacts with a peptide from C4 containing three sulfotyrosine residues. We present a molecular model for the interaction between C1s and C4 that provides support for the above data and poses questions for future research into this aspect of complement activation.
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Affiliation(s)
- Renee C Duncan
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
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21
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Gjelstrup LC, Kaspersen JD, Behrens MA, Pedersen JS, Thiel S, Kingshott P, Oliveira CLP, Thielens NM, Vorup-Jensen T. The role of nanometer-scaled ligand patterns in polyvalent binding by large mannan-binding lectin oligomers. THE JOURNAL OF IMMUNOLOGY 2012; 188:1292-306. [PMID: 22219330 DOI: 10.4049/jimmunol.1103012] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Mannan-binding lectin (MBL) is an important protein of the innate immune system and protects the body against infection through opsonization and activation of the complement system on surfaces with an appropriate presentation of carbohydrate ligands. The quaternary structure of human MBL is built from oligomerization of structural units into polydisperse complexes typically with three to eight structural units, each containing three lectin domains. Insight into the connection between the structure and ligand-binding properties of these oligomers has been lacking. In this article, we present an analysis of the binding to neoglycoprotein-coated surfaces by size-fractionated human MBL oligomers studied with small-angle x-ray scattering and surface plasmon resonance spectroscopy. The MBL oligomers bound to these surfaces mainly in two modes, with dissociation constants in the micro to nanomolar order. The binding kinetics were markedly influenced by both the density of ligands and the number of ligand-binding domains in the oligomers. These findings demonstrated that the MBL-binding kinetics are critically dependent on structural characteristics on the nanometer scale, both with regard to the dimensions of the oligomer, as well as the ligand presentation on surfaces. Therefore, our work suggested that the surface binding of MBL involves recognition of patterns with dimensions on the order of 10-20 nm. The recent understanding that the surfaces of many microbes are organized with structural features on the nanometer scale suggests that these properties of MBL ligand recognition potentially constitute an important part of the pattern-recognition ability of these polyvalent oligomers.
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Affiliation(s)
- Louise C Gjelstrup
- Biophysical Immunology Laboratory, Aarhus University, DK-8000 Aarhus C, Denmark
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22
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Fould B, Garlatti V, Neumann E, Fenel D, Gaboriaud C, Arlaud GJ. Structural and functional characterization of the recombinant human mitochondrial trifunctional protein. Biochemistry 2010; 49:8608-17. [PMID: 20825197 DOI: 10.1021/bi100742w] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The α and β subunits of the human mitochondrial trifunctional protein (TFP), the multienzyme complex involved in fatty acid β-oxidation, were coexpressed in Escherichia coli and purified to homogeneity by nickel affinity chromatography. The resulting α/His-β construct was analyzed by gel filtration, sedimentation velocity, and electron microscopy, indicating a predominance of α(2)β(2) and α(4)β(4) complexes, with higher order oligomers. Electron microscopy indicated that the elementary species α(2)β(2) had overall structural similarity with its bacterial homologue. As shown by cosedimentation and surface plasmon resonance analyses, recombinant TFP interacted strongly with cardiolipin and phosphatidylcholine, suggesting that the natural complex associates with the inner mitochondrial membrane through direct interactions with phospholipids. Recombinant TFP displayed 2-enoyl-CoA hydratase (ECH), l-3-hydroxyacyl-CoA dehydrogenase (HACD), and 3-ketoacyl-CoA thiolase (KACT) activities, and ECH and HACD each reached equilibrium when the downstream enzymes (HACD and KACT, respectively) were made inactive, indicating feed-back inhibition. The KACT activity was optimal at pH 9.5, sensitive to ionic strength, and inhibited at concentrations of its substrate 3-ketohexadecanoyl-CoA >5 μM. Its kinetic constants (k(cat) = 169 s(-1), K(m) = 4 μM) were consistent with those determined previously on a purified porcine TFP preparation. Using different assays, trimetazidine, an efficient antiaginal agent, had no significant inhibitory effect on any of the three enzymatic activities of the recombinant TFP preparation, in contrast with other reports. This study provides the first detailed structural and functional characterization of a recombinant human TFP preparation and opens the way to in-depth analyses through site-directed mutagenesis.
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Affiliation(s)
- Benjamin Fould
- Institut de Biologie Structurale Jean-Pierre Ebel, 41 rue Jules Horowitz, 38027 Grenoble Cedex 1, France
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23
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Rossi V, Bally I, Ancelet S, Xu Y, Frémeaux-Bacchi V, Vivès RR, Sadir R, Thielens N, Arlaud GJ. Functional Characterization of the Recombinant Human C1 Inhibitor Serpin Domain: Insights into Heparin Binding. THE JOURNAL OF IMMUNOLOGY 2010; 184:4982-9. [DOI: 10.4049/jimmunol.0902016] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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24
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Rossi V, Wang Y, Esser AF. Topology of the membrane-bound form of complement protein C9 probed by glycosylation mapping, anti-peptide antibody binding, and disulfide modification. Mol Immunol 2010; 47:1553-60. [PMID: 20153530 DOI: 10.1016/j.molimm.2010.01.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2009] [Revised: 01/11/2010] [Accepted: 01/17/2010] [Indexed: 11/19/2022]
Abstract
The two N-linked oligosaccharides in native human C9 were deleted by site-specific mutagenesis. This aglycosyl-C9 did not differ from its native form in hemolytic and bactericidal activity. A new N-glycosylation site (K311N/E313T) was introduced into the turn of a helix-turn-helix [HTH] fold that had been postulated to form a transmembrane hairpin in membrane-bound C9. This glycosylated form of human C9 was as active as the native protein suggesting that the glycan chain remains on the external side of the membrane and that translocation of this hairpin is not required for membrane anchoring. Furthermore, flow cytometry provided evidence for the recognition of membrane-bound C9 on complement-lysed ghosts by an antibody specific for the HTH fold. A new N-glycosylation site (P26N) was also introduced close to the N-terminus of C9 to test whether this region was involved in C9 polymerization, which is thought to be required for cytolytic activity of C9. Again, this glycosylated C9 was as active as native C9 and could be induced to polymerize by heating or incubation with metal ions. The two C-terminal cystines within the MACPF domain could be eliminated partially or completely without affecting the hemolytic activity. Free sulfhydryl groups of unpaired cysteines in such C9 mutants are blocked since they could not be modified with SH-specific reagents. These results are discussed with respect to a recently proposed model that, on the basis of the MACPF structure in C8alpha, envisions membrane insertion of C9 to resemble the mechanism by which cholesterol-dependent cytolysins enter a membrane.
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Affiliation(s)
- Véronique Rossi
- Division of Cell Biology and Biophysics, School of Biological Sciences, University of Missouri-Kansas City, 5100 Rockhill Road, Kansas City, MO 64110, USA
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25
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Thomsen T, Moeller JB, Schlosser A, Sorensen GL, Moestrup SK, Palaniyar N, Wallis R, Mollenhauer J, Holmskov U. The recognition unit of FIBCD1 organizes into a noncovalently linked tetrameric structure and uses a hydrophobic funnel (S1) for acetyl group recognition. J Biol Chem 2009; 285:1229-38. [PMID: 19892701 DOI: 10.1074/jbc.m109.061523] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have recently identified FIBCD1 (Fibrinogen C domain containing 1) as a type II transmembrane endocytic receptor located primarily in the intestinal brush border. The ectodomain of FIBCD1 comprises a coiled coil, a polycationic region, and a C-terminal FReD (fibrinogen-related domain) that assembles into disulfide-linked homotetramers. The FIBCD1-FReD binds Ca(2+) dependently to acetylated structures like chitin, N-acetylated carbohydrates, and amino acids. FReDs are present in diverse innate immune pattern recognition proteins including the ficolins and horseshoe crab TL5A. Here, we use chemical cross-linking, combined with analytical ultracentrifugation and electron microscopy of the negatively stained recombinant FIBCD1-FReD to show that it assembles into noncovalent tetramers in the absence of the coiled coil. We use surface plasmon resonance, carbohydrate binding, and pulldown assays combined with site-directed mutagenesis to define the binding site involved in the interaction of FIBCD1 with acetylated structures. We show that mutations of central residues (A432V and H415G) in the hydrophobic funnel (S1) abolish the binding of FIBCD1 to acetylated bovine serum albumin and chitin. The double mutations (D393N/D395A) at the putative calcium-binding site reduce the ability of FIBCD1 to bind ligands. We conclude that the FReDs of FIBCD1 forms noncovalent tetramers and that the acetyl-binding site of FReDs of FIBCD1 is homologous to that of tachylectin 5A and M-ficolin but not to the FReD of L-ficolin. We suggest that the spatial organization of the FIBCD1-FReDs determine the molecular pattern recognition specificity and subsequent biological functions.
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Affiliation(s)
- Theresa Thomsen
- Medical Biotechnology Center, University of Southern Denmark, 5000 Odense, Denmark
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26
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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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27
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Schlosser A, Thomsen T, Moeller JB, Nielsen O, Tornøe I, Mollenhauer J, Moestrup SK, Holmskov U. Characterization of FIBCD1 as an acetyl group-binding receptor that binds chitin. THE JOURNAL OF IMMUNOLOGY 2009; 183:3800-9. [PMID: 19710473 DOI: 10.4049/jimmunol.0901526] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Chitin is a highly acetylated compound and the second most abundant biopolymer in the world next to cellulose. Vertebrates are exposed to chitin both through food ingestion and when infected with parasites, and fungi and chitin modulate the immune response in different directions. We have identified a novel homotetrameric 55-kDa type II transmembrane protein encoded by the FIBCD1 gene and highly expressed in the gastrointestinal tract. The ectodomain of FIBCD1 is characterized by a coiled-coil region, a polycationic region and C-terminal fibrinogen-related domain that by disulfide linkage assembles the protein into tetramers. Functional analysis showed a high-affinity and calcium-dependent binding of acetylated components to the fibrinogen domain, and a function in endocytosis was demonstrated. Screening for ligands revealed that the FIBCD1 is a high-affinity receptor for chitin and chitin fragments. FIBCD1 may play an important role in controlling the exposure of intestine to chitin and chitin fragments, which is of great relevance for the immune defense against parasites and fungi and for immune response modulation.
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Affiliation(s)
- Anders Schlosser
- Medical Biotechnology Center, Pathology, University of Southern Denmark, Odense, Denmark.
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28
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Gál P, Dobó J, Závodszky P, Sim RBM. Early complement proteases: C1r, C1s and MASPs. A structural insight into activation and functions. Mol Immunol 2009; 46:2745-52. [PMID: 19477526 DOI: 10.1016/j.molimm.2009.04.026] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2009] [Accepted: 04/28/2009] [Indexed: 10/20/2022]
Abstract
C1r, C1s and the mannose-binding lectin-associated serine proteases (MASPs) are responsible for the initiation of the classical- and lectin pathway activation of the complement system. These enzymes do not act alone, but form supramolecular complexes with pattern recognition molecules such as C1q, MBL, and ficolins. They share the same domain organization but have different substrate specificities and fulfill different physiological functions. In the recent years the rapid progress of structural biology facilitated the understanding of the molecular mechanism of complement activation at atomic level. In this review we summarize our current knowledge about the structure and function of the early complement proteases, delineate the latest models of the multimolecular complexes and present the functional consequences inferred from the structural studies. We also discuss some open questions and debated issues that need to be resolved in the future.
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Affiliation(s)
- Péter Gál
- Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, Budapest, Hungary.
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Beinrohr L, Dobó J, Závodszky P, Gál P. C1, MBL-MASPs and C1-inhibitor: novel approaches for targeting complement-mediated inflammation. Trends Mol Med 2008; 14:511-21. [PMID: 18977695 DOI: 10.1016/j.molmed.2008.09.009] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2008] [Revised: 09/26/2008] [Accepted: 09/26/2008] [Indexed: 10/21/2022]
Abstract
Complement activation is initiated by the pattern-recognition molecules complement component C1q, mannose-binding lectin (MBL) and ficolins (H-, L-, M-ficolin), which typically recognize antibody-antigen complexes or foreign polysaccharides. The associated proteases (C1r, C1s, MASP-1 and MASP-2) then activate the complement system. The serpin C1-inhibitor (C1-inh) blocks activity of all these complexes and has been successfully used in models of disease. Many structures of these components became available recently, including that of C1-inh, facilitating the structure-guided design of drugs targeting complement activation. Here, we propose an approach in which therapeutic proteins are made up of natural protein domains and C1-inh to allow targeting to the site of inflammation and more specific inhibition of complement activation. In particular, engineering a fast-acting C1-inh or fusing it to an 'aiming module' has been shown to be feasible and economical using a humanized yeast expression system. Complement-mediated inflammation has been linked to ischemia-reperfusion injury, organ graft rejection and even neurodegeneration, so targeting this process has direct clinical implications.
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Affiliation(s)
- László Beinrohr
- Institute of Enzymology, Karolina út 29, H-1113 Budapest, Hungary.
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Garlatti V, Martin L, Gout E, Reiser JB, Fujita T, Arlaud GJ, Thielens NM, Gaboriaud C. Structural basis for innate immune sensing by M-ficolin and its control by a pH-dependent conformational switch. J Biol Chem 2007; 282:35814-20. [PMID: 17897951 DOI: 10.1074/jbc.m705741200] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ficolins are soluble oligomeric proteins with lectin-like activity, assembled from collagen fibers prolonged by fibrinogen-like recognition domains. They act as innate immune sensors by recognizing conserved molecular markers exposed on microbial surfaces and thereby triggering effector mechanisms such as enhanced phagocytosis and inflammation. In humans, L- and H-ficolins have been characterized in plasma, whereas a third species, M-ficolin, is secreted by monocytes and macrophages. To decipher the molecular mechanisms underlying their recognition properties, we previously solved the structures of the recognition domains of L- and H-ficolins, in complex with various model ligands (Garlatti, V., Belloy, N., Martin, L., Lacroix, M., Matsushita, M., Endo, Y., Fujita, T., Fontecilla-Camps, J. C., Arlaud, G. J., Thielens, N. M., and Gaboriaud, C. (2007) EMBO J. 24, 623-633). We now report the ligand-bound crystal structures of the recognition domain of M-ficolin, determined at high resolution (1.75-1.8 A), which provides the first structural insights into its binding properties. Interaction with acetylated carbohydrates differs from the one previously described for L-ficolin. This study also reveals the structural determinants for binding to sialylated compounds, a property restricted to human M-ficolin and its mouse counterpart, ficolin B. Finally, comparison between the ligand-bound structures obtained at neutral pH and nonbinding conformations observed at pH 5.6 reveals how the ligand binding site is dislocated at acidic pH. This means that the binding function of M-ficolin is subject to a pH-sensitive conformational switch. Considering that the homologous ficolin B is found in the lysosomes of activated macrophages (Runza, V. L., Hehlgans, T., Echtenacher, B., Zahringer, U., Schwaeble, W. J., and Mannel, D. N. (2006) J. Endotoxin Res. 12, 120-126), we propose that this switch could play a physiological role in such acidic compartments.
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Affiliation(s)
- Virginie Garlatti
- Laboratoire de Cristallographie et Cristallogénèse des Protéines, Institut de Biologie Structurale Jean-Pierre Ebel, Commissariat à l'Energie Atomique-CNRS-Université Joseph Fourier, 38027 Grenoble, France
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Revisiting the mechanism of the autoactivation of the complement protease C1r in the C1 complex: structure of the active catalytic region of C1r. Mol Immunol 2007; 45:1752-60. [PMID: 17996945 DOI: 10.1016/j.molimm.2007.09.031] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2007] [Revised: 09/25/2007] [Accepted: 09/27/2007] [Indexed: 11/20/2022]
Abstract
C1r is a modular serine protease which is the autoactivating component of the C1 complex of the classical pathway of the complement system. We have determined the first crystal structure of the entire active catalytic region of human C1r. This fragment contains the C-terminal serine protease (SP) domain and the preceding two complement control protein (CCP) modules. The activated CCP1-CCP2-SP fragment makes up a dimer in a head-to-tail fashion similarly to the previously characterized zymogen. The present structure shows an increased number of stabilizing interactions. Moreover, in the crystal lattice there is an enzyme-product relationship between the C1r molecules of neighboring dimers. This enzyme-product complex exhibits the crucial S1-P1 salt bridge between Asp631 and Arg446 residues, and intermolecular interaction between the CCP2 module and the SP domain. Based on these novel structural information we propose a new split-and-reassembly model for the autoactivation of the C1r. This model is consistent with experimental results that have not been explained adequately by previous models. It allows autoactivation of C1r without large-scale, directed movement of C1q arms. The model is concordant with the stability of the C1 complex during activation of the next complement components.
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Gál P, Barna L, Kocsis A, Závodszky P. Serine proteases of the classical and lectin pathways: Similarities and differences. Immunobiology 2007; 212:267-77. [PMID: 17544812 DOI: 10.1016/j.imbio.2006.11.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2006] [Revised: 11/02/2006] [Accepted: 11/07/2006] [Indexed: 11/22/2022]
Abstract
C1r, C1s, MBL-associated serine protease (MASP)-1, MASP-2 and MASP-3 are mosaic serine proteases of the classical and lectin pathways of complement. They form a family of enzymes with identical domain organization and similar overall structure, but with different enzymatic properties. MASP-2 of the lectin pathway can autoactivate and cleave C4 and C2 components. In the classical pathway two enzymes mediate these functions: C1r autoactivates and activates C1s, while C1s cleaves C4 and C2. The substrate specificity and the biological function of MASP-1 and MASP-3 have not yet been completely resolved. MASP-1 can autoactivate and the activated MASP-1 has more relaxed substrate specificity than the other members of the family. It was demonstrated that MASP-1 can specifically cleave C2, C3 and fibrinogen, but the physiological relevance of these findings has to be proved. We do not know how MASP-3 becomes activated and its biological function is also not clear. In this review, we will summarize current knowledge about the structure and function of these proteases. Special emphasis will be laid on the specificity, autoactivation and evolution of these enzymes.
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Affiliation(s)
- Péter Gál
- Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, Karolina u. 29, Budapest H-1113, Hungary.
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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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Garlatti V, Belloy N, Martin L, Lacroix M, Matsushita M, Endo Y, Fujita T, Fontecilla-Camps JC, Arlaud GJ, Thielens NM, Gaboriaud C. Structural insights into the innate immune recognition specificities of L- and H-ficolins. EMBO J 2007; 26:623-33. [PMID: 17215869 PMCID: PMC1783469 DOI: 10.1038/sj.emboj.7601500] [Citation(s) in RCA: 148] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2006] [Accepted: 10/31/2006] [Indexed: 02/03/2023] Open
Abstract
Innate immunity relies critically upon the ability of a few pattern recognition molecules to sense molecular markers on pathogens, but little is known about these interactions at the atomic level. Human L- and H-ficolins are soluble oligomeric defence proteins with lectin-like activity, assembled from collagen fibers prolonged by fibrinogen-like recognition domains. The X-ray structures of their trimeric recognition domains, alone and in complex with various ligands, have been solved to resolutions up to 1.95 and 1.7 A, respectively. Both domains have three-lobed structures with clefts separating the distal parts of the protomers. Ca(2+) ions are found at sites homologous to those described for tachylectin 5A (TL5A), an invertebrate lectin. Outer binding sites (S1) homologous to the GlcNAc-binding pocket of TL5A are present in the ficolins but show different structures and specificities. In L-ficolin, three additional binding sites (S2-S4) surround the cleft. Together, they define an unpredicted continuous recognition surface able to sense various acetylated and neutral carbohydrate markers in the context of extended polysaccharides such as 1,3-beta-D-glucan, as found on microbial or apoptotic surfaces.
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Affiliation(s)
- Virginie Garlatti
- Laboratoire de Cristallographie et Cristallogénèse des Protéines, Grenoble, France
| | - Nicolas Belloy
- Laboratoire de Cristallographie et Cristallogénèse des Protéines, Grenoble, France
| | - Lydie Martin
- Laboratoire de Cristallographie et Cristallogénèse des Protéines, Grenoble, France
| | - Monique Lacroix
- Laboratoire d'Enzymologie Moléculaire, Institut de Biologie Structurale Jean-Pierre Ebel, CEA; CNRS; Université Joseph Fourier, Grenoble, France
| | - Misao Matsushita
- Department of Applied Biochemistry, Institute of Glycotechnology, Tokai University, Hiratsuka, Kanagawa, Japan
| | - Yuichi Endo
- Department of Biochemistry, Fukushima Medical University School of Medicine, Fukushima, Japan
| | - Teizo Fujita
- Department of Biochemistry, Fukushima Medical University School of Medicine, Fukushima, Japan
| | | | - Gérard J Arlaud
- Laboratoire d'Enzymologie Moléculaire, Institut de Biologie Structurale Jean-Pierre Ebel, CEA; CNRS; Université Joseph Fourier, Grenoble, France
| | - Nicole M Thielens
- Laboratoire d'Enzymologie Moléculaire, Institut de Biologie Structurale Jean-Pierre Ebel, CEA; CNRS; Université Joseph Fourier, Grenoble, France
| | - Christine Gaboriaud
- Laboratoire de Cristallographie et Cristallogénèse des Protéines, Grenoble, France
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Bíró A, Rovó Z, Papp D, Cervenak L, Varga L, Füst G, Thielens NM, Arlaud GJ, Prohászka Z. Studies on the interactions between C-reactive protein and complement proteins. Immunology 2007; 121:40-50. [PMID: 17244159 PMCID: PMC2265924 DOI: 10.1111/j.1365-2567.2007.02535.x] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Several studies have investigated the interactions between C-reactive protein (CRP) and various complement proteins but none of them took into consideration the different structural forms of CRP. The aim of our study was to investigate whether the different antigenic forms of CRP are able to bind C1q, to trigger activation of the C1 complex and to study the ability of the various CRP forms to bind complement factor H (FH) and C4b-binding protein (C4BP). Interactions between various CRP forms and complement proteins were analysed in enzyme-linked immunosorbent assay and surface plasmon resonance tests and activation of the C1 complex was followed in a reconstituted system using purified C1q, C1r and C1s in the presence of C1-INH. Native, ligand-unbound CRP activated the classical pathway weakly. After binding to phosphocholine, native CRP bound C1q and significantly activated C1. Native CRP complexed to phosphocholine did not bind the complement regulatory proteins FH and C4BP. After disruption of the pentameric structure of CRP, as achieved by urea-treatment or by site-directed mutagenesis, C1q binding and C1 activation further increased and the ability of CRP to bind complement regulatory proteins was revealed. C1q binds to CRP through its globular head domain. The binding sites on CRP for FH and C4BP seemed to be different from that of C1q. In conclusion, in parallel with the increase in the C1-activating ability of different CRP structural variants, the affinity for complement regulatory proteins also increased, providing the biological basis for limitation of excess complement activation.
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Affiliation(s)
- Adrienn Bíró
- 3rd Department of Medicine, Semmelweis University, Budapest, Hungary.
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36
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Fürnrohr BG, Sheriff A, Munoz L, von Briesen H, Urbonaviciute V, Neubert K, Kalden JR, Herrmann M, Voll RE. Signals, receptors, and cytokines involved in the immunomodulatory and anti-inflammatory properties of apoptotic cells. ACTA ACUST UNITED AC 2005. [DOI: 10.1002/sita.200500071] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Bally I, Rossi V, Thielens NM, Gaboriaud C, Arlaud GJ. Functional role of the linker between the complement control protein modules of complement protease C1s. THE JOURNAL OF IMMUNOLOGY 2005; 175:4536-42. [PMID: 16177097 DOI: 10.4049/jimmunol.175.7.4536] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
C1s is the modular serine protease responsible for cleavage of C4 and C2, the protein substrates of the first component of C (C1). Its catalytic domain comprises two complement control protein (CCP) modules connected by a four-residue linker Gln340-Pro-Val-Asp343 and a serine protease domain. To assess the functional role of the linker, a series of mutations were performed at positions 340-343 of human C1s, and the resulting mutants were produced using a baculovirus-mediated expression system and characterized functionally. All mutants were secreted in a proenzyme form and had a mass of 77,203-77,716 Da comparable to that of wild-type C1s, except Q340E, which had a mass of 82,008 Da, due to overglycosylation at Asn391. None of the mutations significantly altered C1s ability to assemble with C1r and C1q within C1. Whereas the other mutations had no effect on C1s activation, the Q340E mutant was totally resistant to C1r-mediated activation, both in the fluid phase and within the C1 complex. Once activated, all mutants cleaved C2 with an efficiency comparable to that of wild-type C1s. In contrast, most of the mutations resulted in a decreased C4-cleaving activity, with particularly pronounced inhibitory effects for point mutants Q340K, P341I, V342K, and D343N. Comparable effects were observed when the C4-cleaving activity of the mutants was measured inside C1. Thus, flexibility of the C1s CCP1-CCP2 linker plays no significant role in C1 assembly or C1s activation by C1r inside C1 but plays a critical role in C4 cleavage by adjusting positioning of this substrate for optimal cleavage by the C1s active site.
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Affiliation(s)
- Isabelle Bally
- Laboratoire d'Enzymologie Moléculaire, Institut de Biologie Structurale Jean-Pierre Ebel, Grenoble, France
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Sørensen R, Thiel S, Jensenius JC. Mannan-binding-lectin-associated serine proteases, characteristics and disease associations. SPRINGER SEMINARS IN IMMUNOPATHOLOGY 2005; 27:299-319. [PMID: 16189649 DOI: 10.1007/s00281-005-0006-z] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2005] [Accepted: 05/26/2005] [Indexed: 11/27/2022]
Abstract
Mannan-binding lectin (MBL)-associated serine proteases (MASPs) circulate in plasma as zymogens in complexes with MBL and with L- and H-ficolin. Upon binding of MBL or ficolin to pathogen-associated molecular patterns, the MASPs are activated. MASP-2 can now cleave C4 and C2 to generate the C3 convertase, C4bC2b. The functions of the other two MASPs, MASP-1 and MASP-3 have not been elucidated. MASP-1 can cleave C2, and with low efficiency also C3, and may serve a function through direct C3 activation. No natural substrate for MASP-3 has been identified. MBL deficiency, occurring at a frequency of about 10%, is the most common congenital immunodeficiency and is associated with susceptibility to infections and autoimmune disorders. Inherited MASP-2 deficiency has been described as the result of a mutation causing the exchange of aspartic acid with a glycine at position 105, a position in the first domain, CUB1, involved in calcium binding. This mutation abolishes the binding to MBL and ficolins, and deprives MASP-2 of functional activity. The index case suffered from recurrent severe infections and autoimmune reactions. The gene frequency of the mutation among Caucasians is 3.6%. It is not found in Chinese, who present a different mutation also associated with MASP-2 deficiency.
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Affiliation(s)
- Rikke Sørensen
- Department of Medical Microbiology and Immunology, Wilhelm Meyers Allé, University of Aarhus, 8000 Aarhus, Denmark.
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Kerr FK, O'Brien G, Quinsey NS, Whisstock JC, Boyd S, de la Banda MG, Kaiserman D, Matthews AY, Bird PI, Pike RN. Elucidation of the Substrate Specificity of the C1s Protease of the Classical Complement Pathway. J Biol Chem 2005; 280:39510-4. [PMID: 16169853 DOI: 10.1074/jbc.m506131200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The complement system is a central component of host defense but can also contribute to the inflammation seen in pathological conditions. The C1s protease of the first complement component, the C1 complex, initiates the pathway. In this study we have elucidated the full specificity of the enzyme for the first time using a randomized phage display library. It was found that, aside from the crucial P(1) position, the S(3) and S(2) subsites (in that order) played the greatest role in determining specificity. C1s prefers Leu or Val at P(3) and Gly or Ala residues at P(2). Apart from the S(2)' position, which showed specificity for Leu, prime subsites did not greatly affect specificity. It was evident, however, that together they significantly contributed to the efficiency of cleavage of a peptide. A peptide substrate based on the top sequence obtained in the phage display validated these results and produced the best kinetics of any C1s substrate to date. The results allow an understanding of the active site specificity of the C1s protease for the first time and provide a basis for the development of specific inhibitors aimed at controlling inflammation associated with complement activation in adverse pathological situations.
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Affiliation(s)
- Felicity K Kerr
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
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40
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Rossi V, Teillet F, Thielens NM, Bally I, Arlaud GJ. Functional characterization of complement proteases C1s/mannan-binding lectin-associated serine protease-2 (MASP-2) chimeras reveals the higher C4 recognition efficacy of the MASP-2 complement control protein modules. J Biol Chem 2005; 280:41811-8. [PMID: 16227207 DOI: 10.1074/jbc.m503813200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
C1s and mannan-binding lectin-associated serine protease-2 (MASP-2) are the proteases that trigger the classical and lectin pathways of complement, respectively. They have identical modular architectures and cleave the same substrates, C2 and C4, but show markedly different efficiencies toward C4. Multisite-directed mutagenesis was used to engineer hybrid C1s/MASP-2 molecules where either the complement control protein (CCP) modules or the serine protease (SP) domain of C1s were swapped for their MASP-2 counterparts. The resulting chimeras (C1s(MASP-2 CCP1/2) and C1s(MASP-2 SP), respectively) were expressed and characterized chemically and functionally. Whereas C1s(MASP-2 SP) was recovered as an active enzyme, C1s(MASP-2 CCP1/2) was produced in a proenzyme form and was susceptible to activation by C1r, indicating that the activation properties of the chimeras were dictated by the nature of their SP domain. Similarly, each activated chimera had an esterolytic activity characteristic of its own SP domain and cleaved C2 with an efficiency comparable with that of their parent C1s and MASP-2 proteases. Both chimeras cleaved C4, but whereas C1s(MASP-2 SP) and C1s had Km values in the micromolar range, C1s(MASP-2 CCP1/2) and MASP-2 had Km values in the nanomolar range, resulting in 21-27-fold higher kcat/Km ratios. Thus, the higher C4 cleavage efficiency of MASP-2 arises from a higher substrate recognition efficacy of its CCP modules. Remarkably, C1s(MASP-2 CCP1/2) retained C1s ability to associate with C1r and C1q to form a pseudo-C1 complex and to undergo activation within this complex, indicating that the C1s-CCP modules have no direct implication in either function.
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Affiliation(s)
- Véronique Rossi
- Laboratoire d'Enzymologie Moléculaire, Institut de Biologie Structurale Jean-Pierre Ebel, 38027 Grenoble Cedex 1, France
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Gál P, Harmat V, Kocsis A, Bián T, Barna L, Ambrus G, Végh B, Balczer J, Sim RB, Náray-Szabó G, Závodszky P. A true autoactivating enzyme. Structural insight into mannose-binding lectin-associated serine protease-2 activations. J Biol Chem 2005; 280:33435-44. [PMID: 16040602 DOI: 10.1074/jbc.m506051200] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Few reports have described in detail a true autoactivation process, where no extrinsic cleavage factors are required to initiate the autoactivation of a zymogen. Herein, we provide structural and mechanistic insight into the autoactivation of a multidomain serine protease: mannose-binding lectin-associated serine protease-2 (MASP-2), the first enzymatic component in the lectin pathway of complement activation. We characterized the proenzyme form of a MASP-2 catalytic fragment encompassing its C-terminal three domains and solved its crystal structure at 2.4 A resolution. Surprisingly, zymogen MASP-2 is capable of cleaving its natural substrate C4, with an efficiency about 10% that of active MASP-2. Comparison of the zymogen and active structures of MASP-2 reveals that, in addition to the activation domain, other loops of the serine protease domain undergo significant conformational changes. This additional flexibility could play a key role in the transition of zymogen MASP-2 into a proteolytically active form. Based on the three-dimensional structures of proenzyme and active MASP-2 catalytic fragments, we present model for the active zymogen MASP-2 complex and propose a mechanism for the autoactivation process.
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Affiliation(s)
- Péter Gál
- Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, P.O. Box 7, Budapest H-1518, Hungary
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Stover CM, Lynch NJ, Hanson SJ, Windbichler M, Gregory SG, Schwaeble WJ. Organization of the MASP2 locus and its expression profile in mouse and rat. Mamm Genome 2005; 15:887-900. [PMID: 15672593 DOI: 10.1007/s00335-004-3006-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The mouse, rat, and human MASP2 loci are situated on syntenic chromosome regions and are highly conserved. They comprise the genes for MASP-2/ MAp19, TAR DNA binding protein of 43 kDa, FRAP kinase, CDT6, Polymyositis-Scleroderma 100-kDa autoantigen, spermidine synthase, and TERE which were analyzed by annotation of available gene transcript data and cross-species comparison of available genomic sequences. The human and rat genes for spermidine synthase have an additional intron compared to the mouse gene. The mouse and rat genes for Polymyositis-Scleroderma 100-kDa autoantigen have an additional exon compared to the human gene. We find support for the hypothesis that the MAp19-specific exon within the MASP2 gene may have originated in a transposable element. Blocks of highly conserved intronic sequences were found in the MASP2 gene and the TARDBP gene. The expression of all genes within the MASP2 locus was analyzed in mouse and rat. The restricted expression of MASP-2 and MAp19 mRNA in liver contrasts with the ubiquitous expression of all neighboring genes studied.
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Affiliation(s)
- Cordula M Stover
- Department of Infection, Immunity and Inflammation, University of Leicester, Leicester LE1 9HN, United Kingdom.
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Harmat V, Gál P, Kardos J, Szilágyi K, Ambrus G, Végh B, Náray-Szabó G, Závodszky P. The Structure of MBL-associated Serine Protease-2 Reveals that Identical Substrate Specificities of C1s and MASP-2 are Realized Through Different Sets of Enzyme–Substrate Interactions. J Mol Biol 2004; 342:1533-46. [PMID: 15364579 DOI: 10.1016/j.jmb.2004.07.014] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2004] [Revised: 07/05/2004] [Accepted: 07/12/2004] [Indexed: 12/01/2022]
Abstract
A family of serine proteases mediates the proteolytic cascades of several defense mechanisms in vertebrates, such as the complement system, blood coagulation and fibrinolysis. These proteases usually form large complexes with other glycoproteins. Their common features are their modular structures and restricted substrate specificities. The lectin pathway of complement, where mannose-binding lectin (MBL) recognizes the carbohydrate structures on pathogens, is activated by mannose-binding lectin-associated serine protease-2 (MASP-2). We present the 2.25A resolution structure of the catalytic fragment of MASP-2 encompassing the second complement control protein module (CCP2) and the serine protease (SP) domain. The CCP2 module stabilizes the structure of the SP domain as demonstrated by differential scanning calorimetry measurements. The asymmetric unit contains two molecules with different CCP-SP domain orientations, reflecting increased modular flexibility at the CCP2/SP joint. This flexibility may partly explain the ability of the MASP-2 dimer to perform all of its functions alone, whereas the same functions are mediated by the much larger C1r2-C1s2 tetramer in the C1 complex of the classical pathway. The main scaffold of the MASP-2 SP domain is chymotrypsin-like. Eight surface loops determine the S1 and other subsite specificities. Surprisingly, some surface loops of MASP-2, e.g. loop 1 and loop 2, which form the S1 pocket are similar to those of trypsin, and show significant differences if compared with those of C1s, indicating that the nearly identical substrate specificities of C1s and MASP-2 are realized through different sets of enzyme-substrate interactions.
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Affiliation(s)
- Veronika Harmat
- Protein Modeling Group, Hungarian Academy of Sciences, Eötvös Loránd University, Pázmány Péter sétány. 1A, H-1117 Budapest, Hungary
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Gaboriaud C, Thielens NM, Gregory LA, Rossi V, Fontecilla-Camps JC, Arlaud GJ. Structure and activation of the C1 complex of complement: unraveling the puzzle. Trends Immunol 2004; 25:368-73. [PMID: 15207504 DOI: 10.1016/j.it.2004.04.008] [Citation(s) in RCA: 180] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Christine Gaboriaud
- Laboratoire de Cristallographie et Cristallogénèse des Protéines, Institut de Biologie Structurale Jean Pierre Ebel, CEA-CNRS-Université Joseph Fourier, 41, rue Jules Horowitz, 38027 Grenoble Cedex 1, France
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Zundel S, Cseh S, Lacroix M, Dahl MR, Matsushita M, Andrieu JP, Schwaeble WJ, Jensenius JC, Fujita T, Arlaud GJ, Thielens NM. Characterization of recombinant mannan-binding lectin-associated serine protease (MASP)-3 suggests an activation mechanism different from that of MASP-1 and MASP-2. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2004; 172:4342-50. [PMID: 15034049 DOI: 10.4049/jimmunol.172.7.4342] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Mannan-binding lectin (MBL)-associated serine proteases (MASP-1, -2, and -3) are homologous modular proteases that each associate with MBL and L- and H-ficolins, which are oligomeric serum lectins involved in innate immunity. To investigate its physicochemical, interaction, and enzymatic properties, human MASP-3 was expressed in insect cells. Ultracentrifugation analysis indicated that rMASP-3 sedimented as a homodimer (s(20,w) = 6.2 +/- 0.1 S) in the presence of Ca(2+), and as a monomer (s(20,w) = 4.6 +/- 0.1 S) in EDTA. As shown by surface plasmon resonance spectroscopy, it associated with both MBL (K(D) = 2.6 nM) and L-ficolin (K(D) = 7.2 nM). The protease was produced in a single-chain, proenzyme form, but underwent slow activation upon prolonged storage at 4 degrees C, resulting from cleavage at the Arg(430)-Ile(431) activation site. Activation was prevented in the presence of protease inhibitors iodoacetamide and 1,10-phenanthroline but was not abolished upon substitution of Ala for the active site Ser(645) of MASP-3, indicating extrinsic proteolysis. In contrast, the corresponding mutations Ser(627)-->Ala in MASP-1 and Ser(618)-->Ala in MASP-2 stabilized the latter in their proenzyme form. Likewise, the MASP-1 and MASP-2 mutants were each activated by their active counterparts, but MASP-3 S645A was not. Activated MASP-3 did not react with C1 inhibitor; had no activity on complement proteins C2, C4, and C3; and only cleaved the N-carboxybenzyloxyglycine-L-arginine thiobenzyl ester substrate to a significant extent. Based on these observations, it is postulated that MASP-3 activation and control involve mechanisms that are different from those of MASP-1 and -2.
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Affiliation(s)
- Stéphanie Zundel
- Laboratoire d'Enzymologie Moléculaire, Institut de Biologie Structurale Jean-Pierre Ebel, Grenoble, France
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Blanchin S, Estienne V, Durand-Gorde JM, Carayon P, Ruf J. Complement activation by direct C4 binding to thyroperoxidase in Hashimoto's thyroiditis. Endocrinology 2003; 144:5422-9. [PMID: 12960013 DOI: 10.1210/en.2003-0918] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Biosynthesis of thyroid hormones is an oxidative process that generates reactive oxygen species (ROS) and involves thyroperoxidase (TPO) that is one of the main autoantigens involved in autoimmune thyroid diseases. The ectodomain of TPO consists of a large N-terminal myeloperoxidase-like module followed by a complement control protein (CCP)-like module and an epidermal growth factor-like module. The presence of these two additional gene modules suggests that they may play some crucial, hitherto unsuspected role associated with thyroid function. Because the CCP module is a constituent of the molecules involved in the activation of C4 complement component, we investigated the possibility that C4 may bind to TPO and activate the complement pathway in autoimmune conditions. We showed that TPO via its CCP module directly activated complement without any mediation by Ig. We suggested that this additional complement pathway requires the production of ROS and specially hydroxyl radicals that aggregate TPO and oxidize methionines of C4. Moreover, we found, in patients with Hashimoto's thyroiditis, that thyrocytes overexpress C4 and all the downstream components of the complement pathway. These results indicate that TPO has some as yet unknown function, which may contribute along with other mechanisms to the massive cell destruction observed in Hashimoto's thyroiditis. Investigating this complement pathway, therefore, would provide an excellent means of reaching a better understanding of the etiology of other degenerative diseases.
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Affiliation(s)
- Stephanie Blanchin
- Institut National de la Santé et de la Recherche Médicale, Unité 555, Faculté de Médicine Timone, Université de la Méditerranée, Morseille, France
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Abstract
CSMD1 is a putative suppressor of squamous cell carcinomas mapping to human chromosomal region 8p23. We have cloned two new members of this gene family, CSMD2 and CSMD3. The three CSMD proteins have very similar structures, each consisting of 14 CUB domains separated from one another by a sushi domain, an additional uninterrupted array of sushi domains, a single transmembrane domain, and a short cytoplasmic tail. CUB and sushi domains are thought to be sites of protein-protein or protein-ligand interactions, suggesting that CSMD proteins are either transmembrane receptors or adhesion proteins. The cytoplasmic tail sequences are highly conserved within the vertebrate lineage. CSMD2 maps to a chromosomal region that may contain a suppressor of oligodendrogliomas, yet its expression is elevated in some head and neck cancer cell lines. Functional overlap between the CSMD1 and the CSMD2 proteins may modify the phenotype resulting from the loss of either protein in tumors.
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Affiliation(s)
- Wei Ling Lau
- Department of Otolaryngology-Head and Neck Surgery, Washington University School of Medicine, Box 8115, 517 S. Euclid Avenue, St. Louis, MO 63110, USA
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Vella F, Thielens NM, Bersch B, Arlaud GJ, Frachet P. A recombinant chimeric epidermal growth factor-like module with high binding affinity for integrins. J Biol Chem 2003; 278:19834-43. [PMID: 12654911 DOI: 10.1074/jbc.m301470200] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Integrins are cell surface receptors involved in numerous pathological processes such as metastasis invasion and abnormal angiogenesis. To target these receptors, the epidermal growth factor (EGF)-like domain of human complement protease C1r was used as a natural scaffold to design chimeric modules containing the RGD motif. Here we report a high yield bacterial expression system and its application to the production of two such modules, EGF-RGD and V2, the latter variant mimicking the RGD-containing domain of disintegrins. These modules were characterized chemically, and their biological activity was investigated by cellular assays using various Chinese hamster ovary cell lines expressing beta1 and beta3 integrins and by surface plasmon resonance spectroscopy. Remarkably, the modifications leading to the V2 variant had differential effects on the interaction with beta3 and beta1 integrins. The disintegrin-like V2 module exhibited enhanced binding affinities compared with EGF-RGD, with KD values of 7.2 nm for alpha5beta1 (a 4-fold decrease) and 3.5 nm for alphavbeta3 (a 1.5-fold decrease), comparable with the values determined for natural integrin ligands. Analysis by NMR spectroscopy also revealed a differential dynamic behavior of the RGD motif in the EGF-RGD and V2 variants, providing insights into the structural basis of their relative binding efficiency. These novel RGD-containing EGF modules open the way to the design of improved variants with selective affinity for particular integrins and their use as carriers for other biologically active modules.
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Affiliation(s)
- Fanny Vella
- Laboratoire d'Enzymologie Moléculaire, Institut de Biologie Structurale Jean-Pierre Ebel, (Commissariat à l'Energie Atomique CNRS, Université Joseph Fourier), Grenoble 38027 Cedex 1, France
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Ambrus G, Gál P, Kojima M, Szilágyi K, Balczer J, Antal J, Gráf L, Laich A, Moffatt BE, Schwaeble W, Sim RB, Závodszky P. Natural substrates and inhibitors of mannan-binding lectin-associated serine protease-1 and -2: a study on recombinant catalytic fragments. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2003; 170:1374-82. [PMID: 12538697 DOI: 10.4049/jimmunol.170.3.1374] [Citation(s) in RCA: 164] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Mannan-binding lectin-associated serine protease (SP) (MASP)-1 and MASP-2 are modular SP and form complexes with mannan-binding lectin, the recognition molecule of the lectin pathway of the complement system. To characterize the enzymatic properties of these proteases we expressed their catalytic region, the C-terminal three domains, in Escherichia coli. Both enzymes autoactivated and cleaved synthetic oligopeptide substrates. In a competing oligopeptide substrate library assay, MASP-1 showed extreme Arg selectivity, whereas MASP-2 exhibited a less restricted, trypsin-like specificity. The enzymatic assays with complement components showed that cleavage of intact C3 by MASP-1 and MASP-2 was detectable, but was only approximately 0.1% of the previously reported efficiency of C3bBb, the alternative pathway C3-convertase. Both enzymes cleaved C3i 10- to 20-fold faster, but still at only approximately 1% of the efficiency of MASP-2 cleavage of C2. We believe that C3 is not the natural substrate of either enzyme. MASP-2 cleaved C2 and C4 at high rates. To determine the role of the individual domains in the catalytic region of MASP-2, the second complement control protein module together with the SP module and the SP module were also expressed and characterized. We demonstrated that the SP domain alone can autoactivate and cleave C2 as efficiently as the entire catalytic region, while the second complement control protein module is necessary for efficient C4 cleavage. This behavior strongly resembles C1s. Each MASP-1 and MASP-2 fragment reacted with C1-inhibitor, which completely blocked the enzymatic action of the enzymes. Nevertheless, relative rates of reaction with alpha-2-macroglobulin and C1-inhibitor suggest that alpha-2-macroglobulin may be a significant physiological inhibitor of MASP-1.
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Affiliation(s)
- Géza Ambrus
- Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, Budapest, Hungary.
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Cseh S, Vera L, Matsushita M, Fujita T, Arlaud GJ, Thielens NM. Characterization of the interaction between L-ficolin/p35 and mannan-binding lectin-associated serine proteases-1 and -2. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2002; 169:5735-43. [PMID: 12421953 DOI: 10.4049/jimmunol.169.10.5735] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Ficolins are oligomeric lectins comprising a collagen-like and a fibrinogen-like domain, with a binding specificity for N-acetylglucosamine. It has been reported recently that L-ficolin/P35 associates with mannan-binding lectin (MBL)-associated serine proteases (MASP-1 and -2) and MBL-associated protein 19 (MAp19) in serum and forms complexes able to activate complement. Using surface plasmon resonance spectroscopy we have shown that recombinant MASP-1 and -2, their N-terminal CUB1 (module originally found in complement proteins C1r/C1s, Uegf, and bone morphogenetic protein-1)-epidermal growth factor (EGF)-CUB2 and CUB1-EGF segments, and MAp19 bind to immobilized L-ficolin/P35 in the presence of Ca(2+) ions. Comparable K(d) values were obtained for the full-length proteases and their CUB1-EGF-CUB2 segments (9.2 and 10 nM for MASP-1 and 4.6 and 5.4 nM for MASP-2, respectively), whereas higher values were obtained for the CUB1-EGF segments (26.7, 15.6, and 14.3 nM for MASP-1, MASP-2, and MAp19). These values are in the same range as those determined for the interaction of these proteins with MBL. Binding was Ca(2+) dependent and was only partly sensitive to EDTA for MASP-1, MASP-2, and MASP-2 CUB1-EGF-CUB2. Half-maximal binding was obtained at comparable Ca(2+) concentrations for MASP-1 and MASP-2 (0.45 and 0.47 micro M, respectively), their CUB1-EGF-CUB2 segments (0.37 and 0.72 micro M), and their CUB1-EGF segments (0.31 and 0.79 micro M). These values are lower than those determined in the case of MBL, indicating a difference between MBL and L-ficolin/P35 with respect to the Ca(2+) dependence of their interaction with the MASPs. Preincubation of the MASPs with soluble MBL inhibited subsequent binding to immobilized L-ficolin/P35 and, conversely, suggesting that these lectins compete with each other for binding to the MASPs in vivo.
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Affiliation(s)
- Sandor Cseh
- Laboratoire d'Enzymologie Moléculaire, Institut de Biologie Structurale Jean-Pierre Ebel (Commissariat à l'Energie Atomique-Centre National de la Recherche Scientifique-Université Joseph Fourier), 41 rue Jules Horowitz, 38027 Grenoble Cedex 1, France
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