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de Jorge EG, Yebenes H, Serna M, Tortajada A, Llorca O, de Córdoba SR. How novel structures inform understanding of complement function. Semin Immunopathol 2017; 40:3-14. [PMID: 28808775 DOI: 10.1007/s00281-017-0643-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Accepted: 08/03/2017] [Indexed: 11/30/2022]
Abstract
During the last decade, the complement field has experienced outstanding advancements in the mechanistic understanding of how complement activators are recognized, what C3 activation means, how protein complexes like the C3 convertases and the membrane attack complex are assembled, and how positive and negative complement regulators perform their function. All of this has been made possible mostly because of the contributions of structural biology to the study of the complement components. The wealth of novel structural data has frequently provided support to previously held knowledge, but often has added alternative and unexpected insights into complement function. Here, we will review some of these findings focusing in the alternative and terminal complement pathways.
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Affiliation(s)
- Elena Goicoechea de Jorge
- Department of Microbiology I (Immunology), Complutense University School of Medicine and 12 de Octubre Health Research Institute (imas12), Madrid, Spain
| | - Hugo Yebenes
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Ramiro de Maeztu 9, 28040, Madrid, Spain
| | - Marina Serna
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Ramiro de Maeztu 9, 28040, Madrid, Spain
| | - Agustín Tortajada
- Department of Microbiology I (Immunology), Complutense University School of Medicine and 12 de Octubre Health Research Institute (imas12), Madrid, Spain
| | - Oscar Llorca
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Ramiro de Maeztu 9, 28040, Madrid, Spain.,Structural Biology Programme, CNIO, C/ Melchor Fernández Almagro 3, 28029, Madrid, Spain
| | - Santiago Rodríguez de Córdoba
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Ramiro de Maeztu 9, 28040, Madrid, Spain. .,Ciber de Enfermedades Raras, Madrid, Spain.
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Morgan BP, Walters D, Serna M, Bubeck D. Terminal complexes of the complement system: new structural insights and their relevance to function. Immunol Rev 2016; 274:141-151. [PMID: 27782334 DOI: 10.1111/imr.12461] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Complement is a key component of innate immunity in health and a powerful driver of inflammation and tissue injury in disease. The biological and pathological effects of complement activation are mediated by activation products. These come in two flavors: (i) proteolytic fragments of complement proteins (C3, C4, C5) generated during activation that bind specific receptors on target cells to mediate effects; (ii) the multimolecular membrane attack complex generated from the five terminal complement proteins that directly binds to and penetrates target cell membranes. Several recent publications have described structural insights that have changed perceptions of the nature of this membrane attack complex. This review will describe these recent advances in understanding of the structure of the membrane attack complex and its by-product the fluid-phase terminal complement complex and relate these new structural insights to functional consequences and cell responses to complement membrane attack.
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Affiliation(s)
- Bryan Paul Morgan
- Systems Immunity Research Institute, Division of Infection and Immunity, School of Medicine, Cardiff University, Cardiff, UK.
| | - David Walters
- Systems Immunity Research Institute, Division of Infection and Immunity, School of Medicine, Cardiff University, Cardiff, UK
| | - Marina Serna
- Faculty of Natural Sciences, Department of Life Sciences, Imperial College, London, UK
| | - Doryen Bubeck
- Faculty of Natural Sciences, Department of Life Sciences, Imperial College, London, UK
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Dudkina NV, Spicer BA, Reboul CF, Conroy PJ, Lukoyanova N, Elmlund H, Law RHP, Ekkel SM, Kondos SC, Goode RJA, Ramm G, Whisstock JC, Saibil HR, Dunstone MA. Structure of the poly-C9 component of the complement membrane attack complex. Nat Commun 2016; 7:10588. [PMID: 26841934 PMCID: PMC4742998 DOI: 10.1038/ncomms10588] [Citation(s) in RCA: 90] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Accepted: 12/31/2015] [Indexed: 12/11/2022] Open
Abstract
The membrane attack complex (MAC)/perforin-like protein complement component 9 (C9) is the major component of the MAC, a multi-protein complex that forms pores in the membrane of target pathogens. In contrast to homologous proteins such as perforin and the cholesterol-dependent cytolysins (CDCs), all of which require the membrane for oligomerisation, C9 assembles directly onto the nascent MAC from solution. However, the molecular mechanism of MAC assembly remains to be understood. Here we present the 8 Å cryo-EM structure of a soluble form of the poly-C9 component of the MAC. These data reveal a 22-fold symmetrical arrangement of C9 molecules that yield an 88-strand pore-forming β-barrel. The N-terminal thrombospondin-1 (TSP1) domain forms an unexpectedly extensive part of the oligomerisation interface, thus likely facilitating solution-based assembly. These TSP1 interactions may also explain how additional C9 subunits can be recruited to the growing MAC subsequent to membrane insertion.
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Affiliation(s)
- Natalya V. Dudkina
- Department of Crystallography, Institute of Structural and Molecular Biology, Birkbeck College, London WC1E 7HX, UK
| | - Bradley A. Spicer
- ARC Centre of Excellence in Advanced Molecular Imaging, Clayton Campus, Monash University, Melbourne, Victoria 3800, Australia
- Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Clayton Campus, Monash University, Melbourne, Victoria 3800, Australia
| | - Cyril F. Reboul
- ARC Centre of Excellence in Advanced Molecular Imaging, Clayton Campus, Monash University, Melbourne, Victoria 3800, Australia
- Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Clayton Campus, Monash University, Melbourne, Victoria 3800, Australia
| | - Paul J. Conroy
- ARC Centre of Excellence in Advanced Molecular Imaging, Clayton Campus, Monash University, Melbourne, Victoria 3800, Australia
- Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Clayton Campus, Monash University, Melbourne, Victoria 3800, Australia
| | - Natalya Lukoyanova
- Department of Crystallography, Institute of Structural and Molecular Biology, Birkbeck College, London WC1E 7HX, UK
| | - Hans Elmlund
- ARC Centre of Excellence in Advanced Molecular Imaging, Clayton Campus, Monash University, Melbourne, Victoria 3800, Australia
- Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Clayton Campus, Monash University, Melbourne, Victoria 3800, Australia
| | - Ruby H. P. Law
- ARC Centre of Excellence in Advanced Molecular Imaging, Clayton Campus, Monash University, Melbourne, Victoria 3800, Australia
- Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Clayton Campus, Monash University, Melbourne, Victoria 3800, Australia
| | - Susan M. Ekkel
- ARC Centre of Excellence in Advanced Molecular Imaging, Clayton Campus, Monash University, Melbourne, Victoria 3800, Australia
- Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Clayton Campus, Monash University, Melbourne, Victoria 3800, Australia
| | - Stephanie C. Kondos
- Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Clayton Campus, Monash University, Melbourne, Victoria 3800, Australia
| | - Robert J. A. Goode
- Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Clayton Campus, Monash University, Melbourne, Victoria 3800, Australia
| | - Georg Ramm
- ARC Centre of Excellence in Advanced Molecular Imaging, Clayton Campus, Monash University, Melbourne, Victoria 3800, Australia
- Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Clayton Campus, Monash University, Melbourne, Victoria 3800, Australia
| | - James C. Whisstock
- ARC Centre of Excellence in Advanced Molecular Imaging, Clayton Campus, Monash University, Melbourne, Victoria 3800, Australia
- Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Clayton Campus, Monash University, Melbourne, Victoria 3800, Australia
| | - Helen R. Saibil
- Department of Crystallography, Institute of Structural and Molecular Biology, Birkbeck College, London WC1E 7HX, UK
| | - Michelle A. Dunstone
- ARC Centre of Excellence in Advanced Molecular Imaging, Clayton Campus, Monash University, Melbourne, Victoria 3800, Australia
- Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Clayton Campus, Monash University, Melbourne, Victoria 3800, Australia
- Department of Microbiology, Biomedicine Discovery Institute, Clayton Campus, Monash University, Melbourne, 3800 Victoria, Australia
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Serna M, Giles JL, Morgan BP, Bubeck D. Structural basis of complement membrane attack complex formation. Nat Commun 2016; 7:10587. [PMID: 26841837 PMCID: PMC4743022 DOI: 10.1038/ncomms10587] [Citation(s) in RCA: 164] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Accepted: 12/31/2015] [Indexed: 01/26/2023] Open
Abstract
In response to complement activation, the membrane attack complex (MAC) assembles from fluid-phase proteins to form pores in lipid bilayers. MAC directly lyses pathogens by a 'multi-hit' mechanism; however, sublytic MAC pores on host cells activate signalling pathways. Previous studies have described the structures of individual MAC components and subcomplexes; however, the molecular details of its assembly and mechanism of action remain unresolved. Here we report the electron cryo-microscopy structure of human MAC at subnanometre resolution. Structural analyses define the stoichiometry of the complete pore and identify a network of interaction interfaces that determine its assembly mechanism. MAC adopts a 'split-washer' configuration, in contrast to the predicted closed ring observed for perforin and cholesterol-dependent cytolysins. Assembly precursors partially penetrate the lipid bilayer, resulting in an irregular β-barrel pore. Our results demonstrate how differences in symmetric and asymmetric components of the MAC underpin a molecular basis for pore formation and suggest a mechanism of action that extends beyond membrane penetration.
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Affiliation(s)
- Marina Serna
- Department of Life Sciences, Imperial College London, Sir Ernst Chain Building, South Kensington Campus, London SW7 2AZ, UK
| | - Joanna L. Giles
- Institute of Infection and Immunity, School of Medicine, Cardiff University, Heath Park, Cardiff CF14 4XN, UK
| | - B. Paul Morgan
- Institute of Infection and Immunity, School of Medicine, Cardiff University, Heath Park, Cardiff CF14 4XN, UK
| | - Doryen Bubeck
- Department of Life Sciences, Imperial College London, Sir Ernst Chain Building, South Kensington Campus, London SW7 2AZ, UK
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Abstract
The complement system is an intricate network of serum proteins that mediates humoral innate immunity through an amplification cascade that ultimately leads to recruitment of inflammatory cells or opsonisation or killing of pathogens. One effector arm of this network is the terminal pathway of complement, which leads to the formation of the membrane attack complex (MAC) composed of complement components C5b, C6, C7, C8 and C9. Upon formation of C5 convertases via the classical or alternative pathways of complement activation, C5b is generated from C5 by proteolytic cleavage, nucleating a series of association and polymerisation reactions of the MAC-constituting complement components that culminate in pore formation of pathogenic membranes. Recent structures of MAC components and homologous proteins significantly increased our understanding of oligomerisation, membrane association and integration, shedding light onto the molecular mechanism of this important branch of the innate immune system.
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Kondos SC, Hatfaludi T, Voskoboinik I, Trapani JA, Law RHP, Whisstock JC, Dunstone MA. The structure and function of mammalian membrane-attack complex/perforin-like proteins. ACTA ACUST UNITED AC 2010; 76:341-51. [PMID: 20860583 DOI: 10.1111/j.1399-0039.2010.01566.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The membrane-attack complex (MAC) of complement pathway and perforin (PF) are important tools deployed by the immune system to target pathogens. Both perforin and the C9 component of the MAC contain a common 'MACPF' domain and form pores in the cell membrane as part of their function. The MAC targets gram-negative bacteria and certain pathogenic parasites, while perforin, released by natural killer cells or cytotoxic T lymphocytes (CTLs), targets virus-infected and transformed host cells (1). Remarkably, recent structural studies show that the MACPF domain is homologous to the pore-forming portion of bacterial cholesterol-dependent cytolysins; these data have provided important insight into the mechanism of pore-forming MACPF proteins. In addition to their role in immunity, MACPF family members have been identified as animal venoms, factors required for pathogen migration across host cell membranes and factors that govern developmental processes such as embryonic patterning and neuronal guidance (2). While most MACPF proteins characterized to date either form pores or span lipid membranes, some do not (e.g. the C6 component of the MAC). A current challenge is thus to understand the role, pore forming or otherwise, of MACPF proteins in developmental biology. This review discusses structural and functional diversity of the mammalian MACPF proteins.
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Affiliation(s)
- S C Kondos
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia
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Gu X, Dankert JR. Isolation of the C9b fragment of human complement component C9 using urea in the absence of detergents. J Immunol Methods 1996; 189:37-45. [PMID: 8576578 DOI: 10.1016/0022-1759(95)00225-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The bactericidal activity of the C5b-9 complex of complement is dependent upon the terminal complement component C9. The precursor C5b-8 complex is not harmful to bacterial cells until C9 is added to complete the C5b-9 complex. The C9 molecule can be proteolytically cleaved by thrombin to yield an intact, nicked molecule that remains fully functional when added to either bacterial cells or erythrocytes bearing pre-formed C5b-8 complexes. In investigating the membranolytic function of C9 in the C5b-9 complex, the carboxyl-terminal portion of the nicked molecule (C9b) has been shown to be membranolytic when added to erythrocytes, liposomes, or bacterial inner membranes in the absence of any other complement components. The isolation of C9b from nicked C9 has been accomplished by preparative gel electrophoresis using detergents, however the study of the activity of C9b in membrane systems may be complicated by the possible presence of residual detergent. To address this concern, we have used 4 M urea in conjunction with hydroxyapatite chromatography and a phosphate elution procedure to separate the domains of nicked C9. The isolated C9b domain, free of detergents and in the absence of any other complement components, was found to be membranolytic. C9b isolated in this manner was capable of lysing erythrocytes and inhibiting the growth of bacterial spheroplasts.
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Affiliation(s)
- X Gu
- Department of Biology, University of Southwestern Louisiana, Lafayette 70504, USA
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