201
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Mutations in complement C3 from aHUS patients. Blood 2015; 125:2316-8. [PMID: 25858888 DOI: 10.1182/blood-2015-02-625285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In this issue of Blood, Schramm et al demonstrate that the majority of mutations in complement C3 identified in atypical hemolytic uremic syndrome (aHUS) patients cause dysregulation in the alternative pathway of complement.
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202
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Merle NS, Church SE, Fremeaux-Bacchi V, Roumenina LT. Complement System Part I - Molecular Mechanisms of Activation and Regulation. Front Immunol 2015; 6:262. [PMID: 26082779 PMCID: PMC4451739 DOI: 10.3389/fimmu.2015.00262] [Citation(s) in RCA: 966] [Impact Index Per Article: 107.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 05/11/2015] [Indexed: 12/12/2022] Open
Abstract
Complement is a complex innate immune surveillance system, playing a key role in defense against pathogens and in host homeostasis. The complement system is initiated by conformational changes in recognition molecular complexes upon sensing danger signals. The subsequent cascade of enzymatic reactions is tightly regulated to assure that complement is activated only at specific locations requiring defense against pathogens, thus avoiding host tissue damage. Here, we discuss the recent advances describing the molecular and structural basis of activation and regulation of the complement pathways and their implication on physiology and pathology. This article will review the mechanisms of activation of alternative, classical, and lectin pathways, the formation of C3 and C5 convertases, the action of anaphylatoxins, and the membrane-attack-complex. We will also discuss the importance of structure-function relationships using the example of atypical hemolytic uremic syndrome. Lastly, we will discuss the development and benefits of therapies using complement inhibitors.
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Affiliation(s)
- Nicolas S Merle
- UMR_S 1138, Cordeliers Research Center, Complement and Diseases Team, INSERM , Paris , France ; UMR_S 1138, Centre de Recherche des Cordeliers, Sorbonne Paris Cité, Université Paris Descartes , Paris , France ; UMR_S 1138, Centre de Recherche des Cordeliers, Sorbonne Universités, Université Pierre et Marie Curie-Paris , Paris , France
| | - Sarah Elizabeth Church
- UMR_S 1138, Centre de Recherche des Cordeliers, Sorbonne Paris Cité, Université Paris Descartes , Paris , France ; UMR_S 1138, Centre de Recherche des Cordeliers, Sorbonne Universités, Université Pierre et Marie Curie-Paris , Paris , France ; UMR_S 1138, Cordeliers Research Center, Integrative Cancer Immunology Team, INSERM , Paris , France
| | - Veronique Fremeaux-Bacchi
- UMR_S 1138, Cordeliers Research Center, Complement and Diseases Team, INSERM , Paris , France ; UMR_S 1138, Centre de Recherche des Cordeliers, Sorbonne Paris Cité, Université Paris Descartes , Paris , France ; UMR_S 1138, Centre de Recherche des Cordeliers, Sorbonne Universités, Université Pierre et Marie Curie-Paris , Paris , France ; Service d'Immunologie Biologique, Assistance Publique-Hôpitaux de Paris, Hôpital Européen Georges-Pompidou , Paris , France
| | - Lubka T Roumenina
- UMR_S 1138, Cordeliers Research Center, Complement and Diseases Team, INSERM , Paris , France ; UMR_S 1138, Centre de Recherche des Cordeliers, Sorbonne Paris Cité, Université Paris Descartes , Paris , France ; UMR_S 1138, Centre de Recherche des Cordeliers, Sorbonne Universités, Université Pierre et Marie Curie-Paris , Paris , France
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203
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Józsi M, Tortajada A, Uzonyi B, Goicoechea de Jorge E, Rodríguez de Córdoba S. Factor H-related proteins determine complement-activating surfaces. Trends Immunol 2015; 36:374-84. [DOI: 10.1016/j.it.2015.04.008] [Citation(s) in RCA: 108] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Revised: 04/15/2015] [Accepted: 04/20/2015] [Indexed: 01/07/2023]
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204
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de Córdoba SR. Complement genetics and susceptibility to inflammatory disease. Lessons from genotype-phenotype correlations. Immunobiology 2015; 221:709-14. [PMID: 26004345 DOI: 10.1016/j.imbio.2015.05.015] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Accepted: 05/06/2015] [Indexed: 10/23/2022]
Abstract
Different genome-wide linkage and association studies performed during the last 15 years have associated mutations and polymorphisms in complement genes with different diseases characterized by tissue damage and inflammation. These are complex disorders in which genetically susceptible individuals usually develop the pathology as a consequence of environmental triggers. Although complement dysregulation is a common feature of these pathologies, how the disease phenotype is determined is only partly understood. One way to advance understanding is to focus the research in the analysis of the peculiar genotype-phenotype correlations that characterize some of these diseases. I will review here how understanding the functional consequences of these disease-associated complement genetic variants is providing us with novel insights into the underpinning complement biology and a better knowledge of the pathogenic mechanisms underlying each of these pathologies. These advances have important therapeutic and diagnostic implications.
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205
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Pouw RB, Vredevoogd DW, Kuijpers TW, Wouters D. Of mice and men: The factor H protein family and complement regulation. Mol Immunol 2015; 67:12-20. [PMID: 25824240 DOI: 10.1016/j.molimm.2015.03.011] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Revised: 03/09/2015] [Accepted: 03/10/2015] [Indexed: 10/23/2022]
Abstract
For decades immunological research has relied, with variable success, on mouse models to investigate diseases and possible therapeutic interventions. With the approval of the first therapeutic antibody targeting complement, called eculizumab, as therapy in paroxysmal nocturnal hemoglobinuria (PNH) and more recently atypical hemolytic uremic syndrome (aHUS), the viability of targeting the complement system was demonstrated. The potent, endogenous complement regulators have become of increasing interest as templates for designing and developing new therapeutics. Recently, complement inhibitors based on (parts of) the human complement regulator factor H (FH) are being examined for therapeutic intervention in inflammatory conditions. The first step to evaluate the potency of a new drug is often testing it in a mouse model for the target disease. However, translating results to human conditions requires a good understanding of similarities and, more importantly, differences between the human and mouse complement system and particularly regulation. This review will provide a comprehensive overview of the complement regulator FH and its closely related proteins and current views on their role in mice and men.
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Affiliation(s)
- R B Pouw
- Department of Immunopathology, Sanquin Blood Supply, Division Research and Landsteiner laboratory of the Academic Medical Centre, University of Amsterdam, Amsterdam, the Netherlands; Department of Pediatric Hematology, Immunology & Infectious Diseases, Emma Children's Hospital, Academic Medical Centre, Amsterdam, the Netherlands.
| | - D W Vredevoogd
- Department of Immunopathology, Sanquin Blood Supply, Division Research and Landsteiner laboratory of the Academic Medical Centre, University of Amsterdam, Amsterdam, the Netherlands
| | - T W Kuijpers
- Department of Pediatric Hematology, Immunology & Infectious Diseases, Emma Children's Hospital, Academic Medical Centre, Amsterdam, the Netherlands; Department of Blood Cell Research, Sanquin Blood Supply, Division Research and Landsteiner laboratory of the Academic Medical Centre, University of Amsterdam, Amsterdam, the Netherlands
| | - D Wouters
- Department of Immunopathology, Sanquin Blood Supply, Division Research and Landsteiner laboratory of the Academic Medical Centre, University of Amsterdam, Amsterdam, the Netherlands
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206
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Schmidt CQ, Kennedy AT, Tham WH. More than just immune evasion: Hijacking complement by Plasmodium falciparum. Mol Immunol 2015; 67:71-84. [PMID: 25816986 DOI: 10.1016/j.molimm.2015.03.006] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2015] [Revised: 03/04/2015] [Accepted: 03/04/2015] [Indexed: 12/24/2022]
Abstract
Malaria remains one of the world's deadliest diseases. Plasmodium falciparum is responsible for the most severe and lethal form of human malaria. P. falciparum's life cycle involves two obligate hosts: human and mosquito. From initial entry into these hosts, malaria parasites face the onslaught of the first line of host defence, the complement system. In this review, we discuss the complex interaction between complement and malaria infection in terms of hosts immune responses, parasite survival and pathogenesis of severe forms of malaria. We will focus on the role of complement receptor 1 and its associated polymorphisms in malaria immune complex clearance, as a mediator of parasite rosetting and as an entry receptor for P. falciparum invasion. Complement evasion strategies of P. falciparum parasites will also be highlighted. The sexual forms of the malaria parasites recruit the soluble human complement regulator Factor H to evade complement-mediated killing within the mosquito host. A novel evasion strategy is the deployment of parasite organelles to divert complement attack from infective blood stage parasites. Finally we outline the future challenge to understand the implications of these exploitation mechanisms in the interplay between successful infection of the host and pathogenesis observed in severe malaria.
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Affiliation(s)
- Christoph Q Schmidt
- Institute of Pharmacology of Natural Products and Clinical Pharmacology, Ulm University, Helmholtzstraße 20, Ulm, Germany.
| | - Alexander T Kennedy
- Department of Medical Biology, University of Melbourne and Division of Infection and Immunity, The Walter and Eliza Hall Institute, Parkville, Victoria 3052, Australia
| | - Wai-Hong Tham
- Department of Medical Biology, University of Melbourne and Division of Infection and Immunity, The Walter and Eliza Hall Institute, Parkville, Victoria 3052, Australia.
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207
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Age-related macular degeneration and the role of the complement system. Mol Immunol 2015; 67:43-50. [PMID: 25804937 DOI: 10.1016/j.molimm.2015.02.032] [Citation(s) in RCA: 97] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Revised: 02/26/2015] [Accepted: 02/27/2015] [Indexed: 11/21/2022]
Abstract
Age-related macular degeneration (AMD) is a leading cause of visual impairment. It is characterised by damage to a tissue complex composed of the retinal pigment epithelium, Bruch's membrane and choriocapillaris. In early AMD extracellular debris including drusen accumulates in Bruch's membrane and then in late AMD geographic atrophy and/or neovascularisation develop. Variants in genes encoding components of the alternative pathway of the complement cascade have a major influence on AMD risk, especially at the RCA locus on chromosome 1, which contains CFH and the CFHR genes. Immunohistochemical studies have demonstrated complement components in unaffected and AMD macular tissue. Whilst other factors, including oxidative stress, play important roles in AMD pathogenesis, evidence for the central role played by complement dysregulation is discussed in this review.
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208
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Bhattacharjee A, Reuter S, Trojnár E, Kolodziejczyk R, Seeberger H, Hyvärinen S, Uzonyi B, Szilágyi Á, Prohászka Z, Goldman A, Józsi M, Jokiranta TS. The major autoantibody epitope on factor H in atypical hemolytic uremic syndrome is structurally different from its homologous site in factor H-related protein 1, supporting a novel model for induction of autoimmunity in this disease. J Biol Chem 2015; 290:9500-10. [PMID: 25659429 PMCID: PMC4392255 DOI: 10.1074/jbc.m114.630871] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2014] [Indexed: 01/26/2023] Open
Abstract
Atypical hemolytic uremic syndrome (aHUS) is characterized by complement attack against host cells due to mutations in complement proteins or autoantibodies against complement factor H (CFH). It is unknown why nearly all patients with autoimmune aHUS lack CFHR1 (CFH-related protein-1). These patients have autoantibodies against CFH domains 19 and 20 (CFH19–20), which are nearly identical to CFHR1 domains 4 and 5 (CFHR14–5). Here, binding site mapping of autoantibodies from 17 patients using mutant CFH19–20 constructs revealed an autoantibody epitope cluster within a loop on domain 20, next to the two buried residues that are different in CFH19–20 and CFHR14–5. The crystal structure of CFHR14–5 revealed a difference in conformation of the autoantigenic loop in the C-terminal domains of CFH and CFHR1, explaining the variation in binding of autoantibodies from some aHUS patients to CFH19–20 and CFHR14–5. The autoantigenic loop on CFH seems to be generally flexible, as its conformation in previously published structures of CFH19–20 bound to the microbial protein OspE and a sialic acid glycan is somewhat altered. Cumulatively, our data suggest that association of CFHR1 deficiency with autoimmune aHUS could be due to the structural difference between CFHR1 and the autoantigenic CFH epitope, suggesting a novel explanation for CFHR1 deficiency in the pathogenesis of autoimmune aHUS.
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Affiliation(s)
- Arnab Bhattacharjee
- From the Department of Bacteriology and Immunology, Medicum, and Immunobiology Research Program Unit, University of Helsinki and Helsinki University Hospital, 00014 University of Helsinki, Finland, the Institute of Biotechnology and
| | - Stefanie Reuter
- the Junior Research Group for Cellular Immunobiology, Leibniz Institute for Natural Product, Research and Infection Biology-Hans Knöll Institute, 07745 Jena, Germany
| | - Eszter Trojnár
- the Research Laboratory, 3rd Department of Internal Medicine, Semmelweis University, 1125 Budapest, Hungary, and
| | - Robert Kolodziejczyk
- the Institute of Biotechnology and Division of Biochemistry and Biotechnology, Department of Biosciences, University of Helsinki, 00014 University of Helsinki, Finland
| | - Harald Seeberger
- the Junior Research Group for Cellular Immunobiology, Leibniz Institute for Natural Product, Research and Infection Biology-Hans Knöll Institute, 07745 Jena, Germany
| | - Satu Hyvärinen
- From the Department of Bacteriology and Immunology, Medicum, and Immunobiology Research Program Unit, University of Helsinki and Helsinki University Hospital, 00014 University of Helsinki, Finland
| | | | - Ágnes Szilágyi
- the Research Laboratory, 3rd Department of Internal Medicine, Semmelweis University, 1125 Budapest, Hungary, and
| | - Zoltán Prohászka
- the Research Laboratory, 3rd Department of Internal Medicine, Semmelweis University, 1125 Budapest, Hungary, and
| | - Adrian Goldman
- the Institute of Biotechnology and Division of Biochemistry and Biotechnology, Department of Biosciences, University of Helsinki, 00014 University of Helsinki, Finland
| | - Mihály Józsi
- the Junior Research Group for Cellular Immunobiology, Leibniz Institute for Natural Product, Research and Infection Biology-Hans Knöll Institute, 07745 Jena, Germany, MTA-ELTE "Lendület" Complement Research Group, Department of Immunology, Eötvös Loránd University, 1117 Budapest, Hungary
| | - T Sakari Jokiranta
- From the Department of Bacteriology and Immunology, Medicum, and Immunobiology Research Program Unit, University of Helsinki and Helsinki University Hospital, 00014 University of Helsinki, Finland
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209
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Langford-Smith A, Day AJ, Bishop PN, Clark SJ. Complementing the Sugar Code: Role of GAGs and Sialic Acid in Complement Regulation. Front Immunol 2015; 6:25. [PMID: 25699044 PMCID: PMC4313701 DOI: 10.3389/fimmu.2015.00025] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Accepted: 01/12/2015] [Indexed: 01/15/2023] Open
Abstract
Sugar molecules play a vital role on both microbial and mammalian cells, where they are involved in cellular communication, govern microbial virulence, and modulate host immunity and inflammatory responses. The complement cascade, as part of a host's innate immune system, is a potent weapon against invading bacteria but has to be tightly regulated to prevent inappropriate attack and damage to host tissues. A number of complement regulators, such as factor H and properdin, interact with sugar molecules, such as glycosaminoglycans (GAGs) and sialic acid, on host and pathogen membranes and direct the appropriate complement response by either promoting the binding of complement activators or inhibitors. The binding of these complement regulators to sugar molecules can vary from location to location, due to their different specificities and because distinct structural and functional subpopulations of sugars are found in different human organs, such as the brain, kidney, and eye. This review will cover recent studies that have provided important new insights into the role of GAGs and sialic acid in complement regulation and how sugar recognition may be compromised in disease.
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Affiliation(s)
- Alex Langford-Smith
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester , Manchester , UK
| | - Anthony J Day
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester , Manchester , UK
| | - Paul N Bishop
- Centre for Hearing and Vision Research, Institute of Human Development, University of Manchester , Manchester , UK ; Centre for Advanced Discovery and Experimental Therapeutics, University of Manchester and Central Manchester University Hospitals NHS Foundation Trust , Manchester , UK ; Manchester Academic Health Science Centre, University of Manchester and Central Manchester University Hospitals NHS Foundation Trust , Manchester , UK ; Manchester Royal Eye Hospital, Central Manchester University Hospitals NHS Foundation Trust , Manchester , UK
| | - Simon J Clark
- Centre for Hearing and Vision Research, Institute of Human Development, University of Manchester , Manchester , UK ; Centre for Advanced Discovery and Experimental Therapeutics, University of Manchester and Central Manchester University Hospitals NHS Foundation Trust , Manchester , UK
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210
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Mapping interactions between complement C3 and regulators using mutations in atypical hemolytic uremic syndrome. Blood 2015; 125:2359-69. [PMID: 25608561 DOI: 10.1182/blood-2014-10-609073] [Citation(s) in RCA: 90] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Accepted: 01/07/2015] [Indexed: 01/22/2023] Open
Abstract
The pathogenesis of atypical hemolytic uremic syndrome (aHUS) is strongly linked to dysregulation of the alternative pathway of the complement system. Mutations in complement genes have been identified in about two-thirds of cases, with 5% to 15% being in C3. In this study, 23 aHUS-associated genetic changes in C3 were characterized relative to their interaction with the control proteins factor H (FH), membrane cofactor protein (MCP; CD46), and complement receptor 1 (CR1; CD35). In surface plasmon resonance experiments, 17 mutant recombinant proteins demonstrated a defect in binding to FH and/or MCP, whereas 2 demonstrated reduced binding to CR1. In the majority of cases, decreased binding affinity translated to a decrease in proteolytic inactivation (known as cofactor activity) of C3b via FH and MCP. These results were used to map the putative binding regions of C3b involved in the interaction with MCP and CR1 and interrogated relative to known FH binding sites. Seventy-six percent of patients with C3 mutations had low C3 levels that correlated with disease severity. This study expands our knowledge of the functional consequences of aHUS-associated C3 mutations relative to the interaction of C3 with complement regulatory proteins mediating cofactor activity.
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