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Kuźniewska A, Thiel M, Kowalska D, Felberg-Miętka A, Szynkowski P, Ołdziej S, Arjona E, Jongerius I, Rodriguez de Córdoba S, Okrój M, Urban A. Substitutions at position 263 within the von Willebrand factor type A domain determine the functionality of complement C2 protein. Front Immunol 2022; 13:1061696. [PMID: 36591303 PMCID: PMC9797810 DOI: 10.3389/fimmu.2022.1061696] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Accepted: 11/28/2022] [Indexed: 12/23/2022] Open
Abstract
The complement system is one of the first defense lines protecting from invading pathogens. However, it may turn offensive to the body's own cells and tissues when deregulated by the presence of rare genetic variants that impair physiological regulation and/or provoke abnormal activity of key enzymatic components. Factor B and complement C2 are examples of paralogs engaged in the alternative and classical/lectin complement pathway, respectively. Pathogenic mutations in the von Willebrand factor A domain (vWA) of FB have been known for years. Despite substantial homology between two proteins and the demonstration that certain substitutions in FB translated to C2 result in analogous phenotype, there was a limited number of reports on pathogenic C2 variants in patients. Recently, we studied a cohort of patients suffering from rare kidney diseases and confirmed the existence of two gain-of-function and three loss-of-function mutations within the C2 gene sequences coding for the vWA domain (amino acids 254-452) or nearly located unstructured region (243-253) of C2 protein. Herein, we report the functional consequences of amino acid substitution of glutamine at position 263. The p.Q263G variant resulted in the gain-of-function phenotype, similarly to a homologous mutation p.D279G in FB. Conversely, the p.Q263P variant found in a patient with C3 glomerulopathy resulted in the loss of C2 function. Our results confirm that the N-terminal part of the vWA domain is a hot spot crucial for the complement C2 function.
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Affiliation(s)
- Alicja Kuźniewska
- Department of Cell Biology and Immunology, Intercollegiate Faculty of Biotechnology of University of Gdańsk and Medical University of Gdańsk, Gdańsk, Poland
| | - Marcel Thiel
- Department of Cell Biology and Immunology, Intercollegiate Faculty of Biotechnology of University of Gdańsk and Medical University of Gdańsk, Gdańsk, Poland
| | - Daria Kowalska
- Department of Cell Biology and Immunology, Intercollegiate Faculty of Biotechnology of University of Gdańsk and Medical University of Gdańsk, Gdańsk, Poland
| | - Anna Felberg-Miętka
- Department of Cell Biology and Immunology, Intercollegiate Faculty of Biotechnology of University of Gdańsk and Medical University of Gdańsk, Gdańsk, Poland
| | - Patryk Szynkowski
- Department of Cell Biology and Immunology, Intercollegiate Faculty of Biotechnology of University of Gdańsk and Medical University of Gdańsk, Gdańsk, Poland
| | - Stanisław Ołdziej
- Department of Cell Biology and Immunology, Intercollegiate Faculty of Biotechnology of University of Gdańsk and Medical University of Gdańsk, Gdańsk, Poland
| | - Emilia Arjona
- Department of Molecular Biomedicine, Centro de Investigaciones Biológicas and Centro de Investigación Biomédica en Enfermedades Raras, Madrid, Spain
| | - Ilse Jongerius
- Department of Pediatric Immunology, Rheumatology, and Infectious Diseases, Emma Children’s Hospital, Amsterdam University Medical Centre, Amsterdam, Netherlands,Department of Immunopathology, Sanquin Research, Landsteiner Laboratory, Amsterdam University Medical Centers (UMC), University of Amsterdam, Amsterdam, Netherlands
| | - Santiago Rodriguez de Córdoba
- Department of Molecular Biomedicine, Centro de Investigaciones Biológicas and Centro de Investigación Biomédica en Enfermedades Raras, Madrid, Spain
| | - Marcin Okrój
- Department of Cell Biology and Immunology, Intercollegiate Faculty of Biotechnology of University of Gdańsk and Medical University of Gdańsk, Gdańsk, Poland,*Correspondence: Marcin Okrój,
| | - Aleksandra Urban
- Department of Cell Biology and Immunology, Intercollegiate Faculty of Biotechnology of University of Gdańsk and Medical University of Gdańsk, Gdańsk, Poland,Institute for Cancer Research, Oslo University Hospital, Oslo, Norway
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In Silico Designed Gain-of-Function Variants of Complement C2 Support Cytocidal Activity of Anticancer Monoclonal Antibodies. Cancers (Basel) 2022; 14:cancers14051270. [PMID: 35267578 PMCID: PMC8909654 DOI: 10.3390/cancers14051270] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 02/23/2022] [Accepted: 02/24/2022] [Indexed: 02/06/2023] Open
Abstract
The molecular target for the classical complement pathway (CP) is defined by surface-bound immunoglobulins. Therefore, numerous anticancer monoclonal antibodies (mAbs) exploit the CP as their effector mechanism. Conversely, the alternative complement pathway (AP) is spontaneously induced on the host and microbial surfaces, but complement inhibitors on host cells prevent its downstream processing. Gain-of-function (GoF) mutations in the AP components that oppose physiological regulation directly predispose carriers to autoimmune/inflammatory diseases. Based on the homology between AP and CP components, we modified the CP component C2 so that it emulates the known pathogenic mutations in the AP component, factor B. By using tumor cell lines and patient-derived leukemic cells along with a set of clinically approved immunotherapeutics, we showed that the supplementation of serum with recombinant GoF C2 variants not only enhances the cytocidal effect of type I anti-CD20 mAbs rituximab and ofatumumab, but also lowers the threshold of mAbs necessary for the efficient lysis of tumor cells and efficiently exploits the leftovers of the drug accumulated in patients' sera after the previous infusion. Moreover, we demonstrate that GoF C2 acts in concert with other therapeutic mAbs, such as type II anti-CD20, anti-CD22, and anti-CD38 specimens, for overcoming cancer cells resistance to complement attack.
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Urban A, Kowalska D, Stasiłojć G, Kuźniewska A, Skrobińska A, Arjona E, Alonso EC, Fenollosa Segarra MÁ, Jongerius I, Spaapen R, Satchell S, Thiel M, Ołdziej S, Rodriguez de Córdoba S, Okrój M. Gain-of-Function Mutations R249C and S250C in Complement C2 Protein Increase C3 Deposition in the Presence of C-Reactive Protein. Front Immunol 2021; 12:724361. [PMID: 34899688 PMCID: PMC8654806 DOI: 10.3389/fimmu.2021.724361] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2021] [Accepted: 11/02/2021] [Indexed: 01/08/2023] Open
Abstract
The impairment of the alternative complement pathway contributes to rare kidney diseases such as atypical hemolytic uremic syndrome (aHUS) and C3 glomerulopathy (C3G). We recently described an aHUS patient carrying an exceptional gain-of-function (GoF) mutation (S250C) in the classical complement pathway component C2 leading to the formation of hyperactive classical convertases. We now report the identification of the same mutation and another C2 GoF mutation R249C in two other patients with a glomerulopathy of uncertain etiology. Both mutations stabilize the classical C3 convertases by a similar mechanism. The presence of R249C and S250C variants in serum increases complement-dependent cytotoxicity (CDC) in antibody-sensitized human cells and elevates deposition of C3 on ELISA plates coated with C-reactive protein (CRP), as well as on the surface of glomerular endothelial cells. Our data justify the inclusion of classical pathway genes in the genetic analysis of patients suspected of complement-driven renal disorders. Also, we point out CRP as a potential antibody-independent trigger capable of driving excessive complement activation in carriers of the GoF mutations in complement C2.
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Affiliation(s)
- Aleksandra Urban
- Department of Cell Biology and Immunology, Intercollegiate Faculty of Biotechnology of University of Gdańsk and Medical University of Gdańsk, Gdańsk, Poland
| | - Daria Kowalska
- Department of Cell Biology and Immunology, Intercollegiate Faculty of Biotechnology of University of Gdańsk and Medical University of Gdańsk, Gdańsk, Poland
| | - Grzegorz Stasiłojć
- Department of Cell Biology and Immunology, Intercollegiate Faculty of Biotechnology of University of Gdańsk and Medical University of Gdańsk, Gdańsk, Poland
| | - Alicja Kuźniewska
- Department of Cell Biology and Immunology, Intercollegiate Faculty of Biotechnology of University of Gdańsk and Medical University of Gdańsk, Gdańsk, Poland
| | - Anna Skrobińska
- Department of Cell Biology and Immunology, Intercollegiate Faculty of Biotechnology of University of Gdańsk and Medical University of Gdańsk, Gdańsk, Poland
| | - Emilia Arjona
- Centro de Investigaciones Biológicas and Centro de Investigación Biomédica en Enfermedades Raras, Madrid, Spain
| | | | | | - Ilse Jongerius
- Department of Immunopathology, Sanquin Research, Amsterdam and Landsteiner Laboratory, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands.,Emma Children's Hospital, Department of Pediatric Immunology, Rheumatology and Infectious Diseases, Amsterdam University Medical Center, Amsterdam, Netherlands
| | - Robbert Spaapen
- Department of Immunopathology, Sanquin Research, Amsterdam and Landsteiner Laboratory, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
| | - Simon Satchell
- Bristol Renal, Bristol Medical School, University of Bristol, Bristol, United Kingdom
| | - Marcel Thiel
- Laboratory of Biopolymers Structure, Intercollegiate Faculty of Biotechnology of University of Gdańsk and Medical University of Gdańsk, Gdańsk, Poland
| | - Stanisław Ołdziej
- Laboratory of Biopolymers Structure, Intercollegiate Faculty of Biotechnology of University of Gdańsk and Medical University of Gdańsk, Gdańsk, Poland
| | | | - Marcin Okrój
- Department of Cell Biology and Immunology, Intercollegiate Faculty of Biotechnology of University of Gdańsk and Medical University of Gdańsk, Gdańsk, Poland
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Gain-of-function mutation in complement C2 protein identified in a patient with aHUS. J Allergy Clin Immunol 2020; 146:916-919.e11. [PMID: 32113979 DOI: 10.1016/j.jaci.2020.02.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 02/10/2020] [Accepted: 02/14/2020] [Indexed: 11/21/2022]
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Molecular engineering of an efficient four-domain DAF-MCP chimera reveals the presence of functional modularity in RCA proteins. Proc Natl Acad Sci U S A 2019; 116:9953-9958. [PMID: 31036650 DOI: 10.1073/pnas.1818573116] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The complement system is highly efficient in targeting pathogens, but lack of its apposite regulation results in host-cell damage, which is linked to diseases. Thus, complement activation is tightly regulated by a series of proteins, which primarily belong to the regulators of complement activation (RCA) family. Structurally, these proteins are composed of repeating complement control protein (CCP) domains where two to four successive domains contribute to the regulatory functions termed decay-accelerating activity (DAA) and cofactor activity (CFA). However, the precise constitution of the functional units and whether these units can be joined to form a larger composition with dual function have not been demonstrated. Herein, we have parsed the functional units for DAA and CFA by constructing chimeras of the decay-accelerating factor (DAF) that exhibits DAA and membrane cofactor protein (MCP) that exhibits CFA. We show that in a four-CCP framework, a functional unit for each of the regulatory activities is formed by only two successive CCPs wherein each participates in the function, albeit CCP2 has a bipartite function. Additionally, optimal activity requires C-terminal domains that enhance the avidity of the molecule for C3b/C4b. Furthermore, by composing a four-CCP DAF-MCP chimera with robust CFA (for C3b and C4b) and DAA (for classical and alternative pathway C3 convertases), named decay cofactor protein, we show that CCP functional units can be linked to design a dual-activity regulator. These data indicate that the regulatory determinants for these two biological processes are distinct and modular in nature.
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Felberg A, Urban A, Borowska A, Stasiłojć G, Taszner M, Hellmann A, Blom AM, Okrój M. Mutations resulting in the formation of hyperactive complement convertases support cytocidal effect of anti-CD20 immunotherapeutics. Cancer Immunol Immunother 2019; 68:587-598. [PMID: 30725204 PMCID: PMC6447516 DOI: 10.1007/s00262-019-02304-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Accepted: 01/17/2019] [Indexed: 12/16/2022]
Abstract
Anti-CD20 monoclonal antibodies (mAbs) rituximab and ofatumumab are potent activators of the classical complement pathway, and have been approved for the treatment of B-cell malignancies. However, complement exhaustion and overexpression of complement inhibitors by cancer cells diminish their therapeutic potential. The strategies of targeting membrane complement inhibitors by function-blocking antibodies and the supplementation with fresh frozen plasma have been proposed to overcome tumour cell resistance. We present a novel approach, which utilizes gain-of-function variants of complement factor B (FB), a component of alternative C3/C5 convertases, which augment mAb-activated reactions through a positive feedback mechanism called an amplification loop. If complement concentration is limited, an addition of quadruple gain-of-function FB mutant p.D279G p.F286L p.K323E p.Y363A (or selected single mutants) results in significantly increased complement-mediated lysis of ofatumumab-resistant tumour cells, as well as the complete lysis of moderately sensitive cells. Importantly, this effect cannot be achieved by further increasing ofatumumab concentration. Potentiation of cytotoxic effect towards moderately sensitive cells was less apparent at physiological serum concentration. However, an addition of hyperactive FB could compensate the loss of cytotoxic potential of serum collected from the NHL and CLL patients after infusion of rituximab. Residual levels of rituximab in such sera, in combination with added FB, were able to efficiently lyse tumour cells. We suggest that the administration of gain-of-function variants of FB can restore cytotoxic potential of complement-exhausted serum and maximize the therapeutic effect of circulating anti-CD20 mAbs.
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Affiliation(s)
- Anna Felberg
- Department of Medical Biotechnology, Intercollegiate Faculty of Biotechnology, University of Gdańsk and Medical University of Gdańsk, Dębinki 1 Street, 80-211, Gdańsk, Poland
| | - Aleksandra Urban
- Department of Medical Biotechnology, Intercollegiate Faculty of Biotechnology, University of Gdańsk and Medical University of Gdańsk, Dębinki 1 Street, 80-211, Gdańsk, Poland
| | - Anna Borowska
- Department of Medical Biotechnology, Intercollegiate Faculty of Biotechnology, University of Gdańsk and Medical University of Gdańsk, Dębinki 1 Street, 80-211, Gdańsk, Poland
| | - Grzegorz Stasiłojć
- Department of Medical Biotechnology, Intercollegiate Faculty of Biotechnology, University of Gdańsk and Medical University of Gdańsk, Dębinki 1 Street, 80-211, Gdańsk, Poland
| | - Michał Taszner
- Department of Hematology and Transplantology, Medical University of Gdańsk, Gdańsk, Poland
| | - Andrzej Hellmann
- Department of Hematology and Transplantology, Medical University of Gdańsk, Gdańsk, Poland
| | - Anna Maria Blom
- Department of Translational Medicine, Lund University, Malmö, Sweden
| | - Marcin Okrój
- Department of Medical Biotechnology, Intercollegiate Faculty of Biotechnology, University of Gdańsk and Medical University of Gdańsk, Dębinki 1 Street, 80-211, Gdańsk, Poland.
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Li MF, Sun L. Characterization of a teleost membrane-associated protein that is involved in the regulation of complement activation and bacterial infection. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2018; 79:142-149. [PMID: 29066398 DOI: 10.1016/j.dci.2017.10.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Revised: 10/18/2017] [Accepted: 10/18/2017] [Indexed: 06/07/2023]
Abstract
In mammals, membrane-associated complement regulatory proteins (MCRP) can protect host cells from the damaging of the activated complement. In teleost, few studies on the function of MCRP have been documented. In the present report, we identified a MCRP (named CsMCRP) from the teleost fish tongue sole Cynoglossus semilaevis and examined its immune function. CsMCRP shares moderate sequence identities with fish DAF-like molecules. CsMCRP was predicted to be a transmembrane protein with three short consensus repeats located in the extracellular region. CsMCRP expression occurred in nine different tissues, especially blood, and in peripheral blood leukocytes (PBL). Recombinant CsMCRP inhibited complement activation and interacted with bacterial pathogen, the latter in a highly selective manner. Antibody blocking the CsMCRP on PBL significantly inhibited bacterial infection of PBL. These results indicate that teleost CsMCRP is both a regulator of complement activation and a cellular receptor involved in bacterial invasion.
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Affiliation(s)
- Mo-Fei Li
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China
| | - Li Sun
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China.
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Species Specificity of Vaccinia Virus Complement Control Protein for the Bovine Classical Pathway Is Governed Primarily by Direct Interaction of Its Acidic Residues with Factor I. J Virol 2017; 91:JVI.00668-17. [PMID: 28724763 DOI: 10.1128/jvi.00668-17] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Accepted: 07/13/2017] [Indexed: 01/23/2023] Open
Abstract
Poxviruses display species tropism-variola virus is a human-specific virus, while vaccinia virus causes repeated outbreaks in dairy cattle. Consistent with this, variola virus complement regulator SPICE (smallpox inhibitor of complement enzymes) exhibits selectivity in inhibiting the human alternative complement pathway and vaccinia virus complement regulator VCP (vaccinia virus complement control protein) displays selectivity in inhibiting the bovine alternative complement pathway. In the present study, we examined the species specificity of VCP and SPICE for the classical pathway (CP). We observed that VCP is ∼43-fold superior to SPICE in inhibiting bovine CP. Further, functional assays revealed that increased inhibitory activity of VCP for bovine CP is solely due to its enhanced cofactor activity, with no effect on decay of bovine CP C3-convertase. To probe the structural basis of this specificity, we utilized single- and multi-amino-acid substitution mutants wherein 1 or more of the 11 variant VCP residues were substituted in the SPICE template. Examination of these mutants for their ability to inhibit bovine CP revealed that E108, E120, and E144 are primarily responsible for imparting the specificity and contribute to the enhanced cofactor activity of VCP. Binding and functional assays suggested that these residues interact with bovine factor I but not with bovine C4(H2O) (a moiety conformationally similar to C4b). Mapping of these residues onto the modeled structure of bovine C4b-VCP-bovine factor I supported the mutagenesis data. Taken together, our data help explain why the vaccine strain of vaccinia virus was able to gain a foothold in domesticated animals.IMPORTANCE Vaccinia virus was used for smallpox vaccination. The vaccine-derived virus is now circulating and causing outbreaks in dairy cattle in India and Brazil. However, the reason for this tropism is unknown. It is well recognized that the virus is susceptible to neutralization by the complement classical pathway (CP). Because the virus encodes a soluble complement regulator, VCP, we examined whether this protein displays selectivity in targeting bovine CP. Our data show that it does exhibit selectivity in inhibiting the bovine CP and that this is primarily determined by its amino acids E108, E120, and E144, which interact with bovine serine protease factor I to inactivate bovine C4b-one of the two subunits of CP C3-convertase. Of note, the variola complement regulator SPICE contains positively charged residues at these positions. Thus, these variant residues in VCP help enhance its potency against the bovine CP and thereby the fitness of the virus in cattle.
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Hovingh ES, van den Broek B, Jongerius I. Hijacking Complement Regulatory Proteins for Bacterial Immune Evasion. Front Microbiol 2016; 7:2004. [PMID: 28066340 PMCID: PMC5167704 DOI: 10.3389/fmicb.2016.02004] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Accepted: 11/30/2016] [Indexed: 12/11/2022] Open
Abstract
The human complement system plays an important role in the defense against invading pathogens, inflammation and homeostasis. Invading microbes, such as bacteria, directly activate the complement system resulting in the formation of chemoattractants and in effective labeling of the bacteria for phagocytosis. In addition, formation of the membrane attack complex is responsible for direct killing of Gram-negative bacteria. In turn, bacteria have evolved several ways to evade complement activation on their surface in order to be able to colonize and invade the human host. One important mechanism of bacterial escape is attraction of complement regulatory proteins to the microbial surface. These molecules are present in the human body for tight regulation of the complement system to prevent damage to host self-surfaces. Therefore, recruitment of complement regulatory proteins to the bacterial surface results in decreased complement activation on the microbial surface which favors bacterial survival. This review will discuss recent advances in understanding the binding of complement regulatory proteins to the bacterial surface at the molecular level. This includes, new insights that have become available concerning specific conserved motives on complement regulatory proteins that are favorable for microbial binding. Finally, complement evasion molecules are of high importance for vaccine development due to their dominant role in bacterial survival, high immunogenicity and homology as well as their presence on the bacterial surface. Here, the use of complement evasion molecules for vaccine development will be discussed.
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Affiliation(s)
- Elise S. Hovingh
- Department of Medical Microbiology, University Medical Center UtrechtUtrecht, Netherlands
- Centre for Infectious Disease Control, National Institute for Public Health and the EnvironmentBilthoven, Netherlands
| | - Bryan van den Broek
- Department of Medical Microbiology, University Medical Center UtrechtUtrecht, Netherlands
| | - Ilse Jongerius
- Department of Medical Microbiology, University Medical Center UtrechtUtrecht, Netherlands
- Centre for Infectious Disease Control, National Institute for Public Health and the EnvironmentBilthoven, Netherlands
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Forneris F, Wu J, Xue X, Ricklin D, Lin Z, Sfyroera G, Tzekou A, Volokhina E, Granneman JC, Hauhart R, Bertram P, Liszewski MK, Atkinson JP, Lambris JD, Gros P. Regulators of complement activity mediate inhibitory mechanisms through a common C3b-binding mode. EMBO J 2016; 35:1133-49. [PMID: 27013439 PMCID: PMC4868954 DOI: 10.15252/embj.201593673] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Accepted: 02/29/2016] [Indexed: 01/17/2023] Open
Abstract
Regulators of complement activation (RCA) inhibit complement‐induced immune responses on healthy host tissues. We present crystal structures of human RCA (MCP, DAF, and CR1) and a smallpox virus homolog (SPICE) bound to complement component C3b. Our structural data reveal that up to four consecutive homologous CCP domains (i–iv), responsible for inhibition, bind in the same orientation and extended arrangement at a shared binding platform on C3b. Large sequence variations in CCP domains explain the diverse C3b‐binding patterns, with limited or no contribution of some individual domains, while all regulators show extensive contacts with C3b for the domains at the third site. A variation of ~100° rotation around the longitudinal axis is observed for domains binding at the fourth site on C3b, without affecting the overall binding mode. The data suggest a common evolutionary origin for both inhibitory mechanisms, called decay acceleration and cofactor activity, with variable C3b binding through domains at sites ii, iii, and iv, and provide a framework for understanding RCA disease‐related mutations and immune evasion.
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Affiliation(s)
- Federico Forneris
- Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science Utrecht University, Utrecht, The Netherlands
| | - Jin Wu
- Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science Utrecht University, Utrecht, The Netherlands
| | - Xiaoguang Xue
- Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science Utrecht University, Utrecht, The Netherlands
| | - Daniel Ricklin
- Department of Pathology & Laboratory Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Zhuoer Lin
- Department of Pathology & Laboratory Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Georgia Sfyroera
- Department of Pathology & Laboratory Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Apostolia Tzekou
- Department of Pathology & Laboratory Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Elena Volokhina
- Department of Pediatric Nephrology (830), Radboud University Medical Center, Nijmegen, The Netherlands
| | - Joke Cm Granneman
- Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science Utrecht University, Utrecht, The Netherlands
| | - Richard Hauhart
- Department of Medicine, Division of Rheumatology, Washington University School of Medicine, St. Louis, MO, USA
| | - Paula Bertram
- Department of Medicine, Division of Rheumatology, Washington University School of Medicine, St. Louis, MO, USA
| | - M Kathryn Liszewski
- Department of Medicine, Division of Rheumatology, Washington University School of Medicine, St. Louis, MO, USA
| | - John P Atkinson
- Department of Medicine, Division of Rheumatology, Washington University School of Medicine, St. Louis, MO, USA
| | - John D Lambris
- Department of Pathology & Laboratory Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Piet Gros
- Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science Utrecht University, Utrecht, The Netherlands
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11
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Cestari I, Evans-Osses I, Schlapbach LJ, de Messias-Reason I, Ramirez MI. Mechanisms of complement lectin pathway activation and resistance by trypanosomatid parasites. Mol Immunol 2013; 53:328-34. [PMID: 23063472 DOI: 10.1016/j.molimm.2012.08.015] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2012] [Accepted: 08/15/2012] [Indexed: 11/28/2022]
Abstract
Studies in the past decade have demonstrated a crucial role for the complement lectin pathway in host defence against protozoan microbes. Recognition of pathogen surface molecules by mannan-binding lectin and ficolins revealed new mechanisms of innate immune defence and a diversity of parasite strategies of immune evasion. In the present review, we will discuss the current knowledge of: (1) the molecular mechanism of lectin pathway activation by trypanosomes; (2) the mechanisms of complement evasion by trypanosomes; and (3) host genetic deficiencies of complement lectin pathway factors that contribute to infection susceptibility and disease progression. This review will focus on trypanosomatids, the parasites that cause Chagas disease, leishmaniasis and sleeping sickness (African trypanosomiasis).
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Affiliation(s)
- Igor Cestari
- Seattle Biomedical Research Institute, Seattle, WA 98109, USA
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12
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Dissection of functional sites in herpesvirus saimiri complement control protein homolog. J Virol 2012; 87:282-95. [PMID: 23077301 DOI: 10.1128/jvi.01867-12] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Herpesvirus saimiri is known to encode a homolog of human complement regulators named complement control protein homolog (CCPH). We have previously reported that this virally encoded inhibitor effectively inactivates complement by supporting factor I-mediated inactivation of complement proteins C3b and C4b (termed cofactor activity), as well as by accelerating the irreversible decay of the classical/lectin and alternative pathway C3 convertases (termed decay-accelerating activity). To fine map its functional sites, in the present study, we have generated a homology model of CCPH and performed substitution mutagenesis of its conserved residues. Functional analyses of 24 substitution mutants of CCPH indicated that (i) amino acids R118 and F144 play a critical role in imparting C3b and C4b cofactor activities, (ii) amino acids R35, K142, and K191 are required for efficient decay of the C3 convertases, (iii) positively charged amino acids of the linker regions, which are dubbed to be critical for functioning in other complement regulators, are not crucial for its function, and (iv) S100K and G110D mutations substantially enhance its decay-accelerating activities without affecting the cofactor activities. Overall, our data point out that ionic interactions form a major component of the binding interface between CCPH and its interacting partners.
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Yadav VN, Pyaram K, Ahmad M, Sahu A. Species selectivity in poxviral complement regulators is dictated by the charge reversal in the central complement control protein modules. THE JOURNAL OF IMMUNOLOGY 2012; 189:1431-9. [PMID: 22732591 DOI: 10.4049/jimmunol.1200946] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Variola and vaccinia viruses, the two most important members of the family Poxviridae, are known to encode homologs of the human complement regulators named smallpox inhibitor of complement enzymes (SPICE) and vaccinia virus complement control protein (VCP), respectively, to subvert the host complement system. Intriguingly, consistent with the host tropism of these viruses, SPICE has been shown to be more human complement-specific than VCP, and in this study we show that VCP is more bovine complement-specific than SPICE. Based on mutagenesis and mechanistic studies, we suggest that the major determinant for the switch in species selectivity of SPICE and VCP is the presence of oppositely charged residues in the central complement control modules, which help enhance their interaction with factor I and C3b, the proteolytically cleaved form of C3. Thus, our results provide a molecular basis for the species selectivity in poxviral complement regulators.
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Affiliation(s)
- Viveka Nand Yadav
- National Centre for Cell Science, Pune University, Ganeshkhind, Pune 411007, India
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Cestari I, Ansa-Addo E, Deolindo P, Inal JM, Ramirez MI. Trypanosoma cruzi immune evasion mediated by host cell-derived microvesicles. THE JOURNAL OF IMMUNOLOGY 2012; 188:1942-52. [PMID: 22262654 DOI: 10.4049/jimmunol.1102053] [Citation(s) in RCA: 124] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The innate immune system is the first mechanism of vertebrate defense against pathogen infection. In this study, we present evidence for a novel immune evasion mechanism of Trypanosoma cruzi, mediated by host cell plasma membrane-derived vesicles. We found that T. cruzi metacyclic trypomastigotes induced microvesicle release from blood cells early in infection. Upon their release, microvesicles formed a complex on the T. cruzi surface with the complement C3 convertase, leading to its stabilization and inhibition, and ultimately resulting in increased parasite survival. Furthermore, we found that TGF-β-bearing microvesicles released from monocytes and lymphocytes promoted rapid cell invasion by T. cruzi, which also contributed to parasites escaping the complement attack. In addition, in vivo infection with T. cruzi showed a rapid increase of microvesicle levels in mouse plasma, and infection with exogenous microvesicles resulted in increased T. cruzi parasitemia. Altogether, these data support a role for microvesicles contributing to T. cruzi evasion of innate immunity.
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Affiliation(s)
- Igor Cestari
- Laboratório de Biologia Molecular de Parasitas e Vetores, Instituto Oswaldo Cruz, Rio de Janeiro 21040-900, Brazil
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Ahmad M, Raut S, Pyaram K, Kamble A, Mullick J, Sahu A. Domain Swapping Reveals Complement Control Protein Modules Critical for Imparting Cofactor and Decay-Accelerating Activities in Vaccinia Virus Complement Control Protein. THE JOURNAL OF IMMUNOLOGY 2010; 185:6128-37. [DOI: 10.4049/jimmunol.1001617] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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16
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Pyaram K, Kieslich CA, Yadav VN, Morikis D, Sahu A. Influence of electrostatics on the complement regulatory functions of Kaposica, the complement inhibitor of Kaposi's sarcoma-associated herpesvirus. THE JOURNAL OF IMMUNOLOGY 2010; 184:1956-67. [PMID: 20089702 DOI: 10.4049/jimmunol.0903261] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Kaposica, the complement regulator of Kaposi's sarcoma-associated herpesvirus, inhibits complement by supporting factor I-mediated inactivation of the proteolytically activated form of C3 (C3b) and C4 (C4b) (cofactor activity [CFA]) and by accelerating the decay of classical and alternative pathway C3-convertases (decay-accelerating activity [DAA]). Previous data suggested that electrostatic interactions play a critical role in the binding of viral complement regulators to their targets, C3b and C4b. We therefore investigated how electrostatic potential on Kaposica influences its activities. We built a homology structure of Kaposica and calculated the electrostatic potential of the molecule, using the Poisson-Boltzmann equation. Mutants were then designed to alter the overall positive potential of the molecule or of each of its domains and linkers by mutating Lys/Arg to Glu/Gln, and the functional activities of the expressed mutants were analyzed. Our data indicate that 1) positive potential at specific sites and not the overall positive potential on the molecule guides the CFAs and classical pathway DAA; 2) positive potential around the linkers between complement control protein domains (CCPs) 1-2 and 2-3 is more important for DAAs than for CFAs; 3) positive potential in CCP1 is crucial for binding to C3b and C4b, and thereby its functional activities; 4) conversion to negative or enhancement of negative potential for CCPs 2-4 has a marked effect on C3b-linked activities as opposed to C4b-linked activities; and 5) reversal of the electrostatic potential of CCP4 to negative has a differential effect on classical and alternative pathway DAAs. Together, our data provide functional relevance to conservation of positive potential in CCPs 1 and 4 and the linkers of viral complement regulators.
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Affiliation(s)
- Kalyani Pyaram
- National Centre for Cell Science, Pune University Campus, Ganeshkhind, Pune, India
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17
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Liu A, Lin H, Liu Y, Cao X, Wang X, Li Z. Correlation of C3 level with severity of generalized myasthenia gravis. Muscle Nerve 2009; 40:801-8. [DOI: 10.1002/mus.21398] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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18
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Mapping of functional domains in herpesvirus saimiri complement control protein homolog: complement control protein domain 2 is the smallest structural unit displaying cofactor and decay-accelerating activities. J Virol 2009; 83:10299-304. [PMID: 19640995 DOI: 10.1128/jvi.00217-09] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Herpesvirus saimiri encodes a functional homolog of human regulator-of-complement-activation proteins named CCPH that inactivates complement by accelerating the decay of C3 convertases and by serving as a cofactor in factor I-mediated inactivation of their subunits C3b and C4b. Here, we map the functional domains of CCPH. We demonstrate that short consensus repeat 2 (SCR2) is the minimum domain essential for classical/lectin pathway C3 convertase decay-accelerating activity as well as for factor I cofactor activity for C3b and C4b. Thus, CCPH is the first example wherein a single SCR domain has been shown to display complement regulatory functions.
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Karnchanaphanurach P, Mirchev R, Ghiran I, Asara JM, Papahadjopoulos-Sternberg B, Nicholson-Weller A, Golan DE. C3b deposition on human erythrocytes induces the formation of a membrane skeleton-linked protein complex. J Clin Invest 2009; 119:788-801. [PMID: 19258706 DOI: 10.1172/jci36088] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2008] [Accepted: 01/07/2009] [Indexed: 11/17/2022] Open
Abstract
Decay-accelerating factor (DAF, also known as CD55), a glycosylphosphatidylinositol-linked (GPI-linked) plasma membrane protein, protects autologous cells from complement-mediated damage by inhibiting complement component 3 (C3) activation. An important physical property of GPI-anchored complement regulatory proteins such as DAF is their ability to translate laterally in the plasma membrane. Here, we used single-particle tracking and tether-pulling experiments to measure DAF lateral diffusion, lateral confinement, and membrane skeletal associations in human erythrocyte membranes. In native membranes, most DAF molecules exhibited Brownian lateral diffusion. Fluid-phase complement activation caused deposition of C3b, one of the products of C3 cleavage, onto erythrocyte glycophorin A (GPA). We then determined that DAF, C3b, GPA, and band 3 molecules were laterally immobilized in the membranes of complement-treated cells, and GPA was physically associated with the membrane skeleton. Mass spectrometry analysis further showed that band 3, alpha-spectrin, beta-spectrin, and ankyrin were present in a complex with C3b and GPA in complement-treated cells. C3b deposition was also associated with a substantial increase in erythrocyte membrane stiffness and/or viscosity. We therefore suggest that complement activation stimulates the formation of a membrane skeleton-linked DAF-C3b-GPA-band 3 complex on the erythrocyte surface. This complex may promote the removal of senescent erythrocytes from the circulation.
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Affiliation(s)
- Pallop Karnchanaphanurach
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02115, USA
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20
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Sequence diversity of the Trypanosoma cruzi complement regulatory protein family. Infect Immun 2007; 76:750-8. [PMID: 18070905 DOI: 10.1128/iai.01104-07] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
As a central component of innate immunity, complement activation is a critical mechanism of containment and clearance of microbial pathogens in advance of the development of acquired immunity. Several pathogens restrict complement activation through the acquisition of host proteins that regulate complement activation or through the production of their own complement regulatory molecules (M. K. Liszewski, M. K. Leung, R. Hauhart, R. M. Buller, P. Bertram, X. Wang, A. M. Rosengard, G. J. Kotwal, and J. P. Atkinson, J. Immunol. 176:3725-3734, 2006; J. Lubinski, L. Wang, D. Mastellos, A. Sahu, J. D. Lambris, and H. M. Friedman, J. Exp. Med. 190:1637-1646, 1999). The infectious stage of the protozoan parasite Trypanosoma cruzi produces a surface-anchored complement regulatory protein (CRP) that functions to inhibit alternative and classical pathway complement activation (K. A. Norris, B. Bradt, N. R. Cooper, and M. So, J. Immunol. 147:2240-2247, 1991). This study addresses the genomic complexity of the T. cruzi CRP and its relationship to the T. cruzi supergene family comprising active trans-sialidase (TS) and TS-like proteins. The TS superfamily consists of several functionally distinct subfamilies that share a characteristic sialidase domain at their amino termini. These TS families include active TS, adhesions, CRPs, and proteins of unknown functions (G. A. Cross and G. B. Takle, Annu. Rev. Microbiol. 47:385-411, 1993). A sequence comparison search of GenBank using BLASTP revealed several full-length paralogs of CRP. These proteins share significant homology at their amino termini and a strong spatial conservation of cysteine residues. Alternative pathway complement regulation was confirmed for CRP paralogs with 58% (low) and 83% (high) identity to AAB49414. CRPs are functionally similar to the microbial and mammalian proteins that regulate complement activation. Sequence alignment of mammalian complement control proteins to CRP showed that these sequences are distinct, supporting a convergent evolutionary pathway. Finally, we show that a clonal line of T. cruzi expresses multiple unique copies of CRP that are differentially recognized by patient sera.
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Harris CL, Pettigrew DM, Lea SM, Morgan BP. Decay-accelerating factor must bind both components of the complement alternative pathway C3 convertase to mediate efficient decay. THE JOURNAL OF IMMUNOLOGY 2007; 178:352-9. [PMID: 17182573 DOI: 10.4049/jimmunol.178.1.352] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Decay-accelerating factor (DAF; CD55) inhibits the complement (C) cascade by dissociating the multimolecular C3 convertase enzymes central to amplification. We have previously demonstrated using surface plasmon resonance (Biacore International) that DAF mediates decay of the alternative pathway C3 convertase, C3bBb, but not of the inactive proenzyme, C3bB, and have shown that the major site of interaction is with the larger cleavage subunit factor B (Bb) subunit. In this study, we dissect these interactions and demonstrate that the second short consensus repeat (SCR) domain of DAF (SCR2) interacts only with Bb, whereas SCR4 interacts with C3b. Despite earlier studies that found SCR3 to be critical to DAF activity, we find that SCR3 does not directly interact with either subunit. Furthermore, we demonstrate that properdin, a positive regulator of the alternative pathway, does not directly interact with DAF. Extending from studies of binding to decay-accelerating activity, we show that truncated forms of DAF consisting of SCRs 2 and 3 bind the convertase stably via SCR2-Bb interactions but have little functional activity. In contrast, an SCR34 construct mediates decay acceleration, presumably due to SCR4-C3b interactions demonstrated above, because SCR3 alone has no binding or functional effect. We propose that DAF interacts with C3bBb through major sites in SCR2 and SCR4. Binding to Bb via SCR2 increases avidity of binding, concentrating DAF on the active convertase, whereas more transient interactions through SCR4 with C3b directly mediate decay acceleration. These data provide new insights into the mechanisms involved in C3 convertase decay by DAF.
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Affiliation(s)
- Claire L Harris
- Department of Medical Biochemistry and Immunology, School of Medicine, Cardiff University, Cardiff, United Kingdom
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Richards A, Kavanagh D, Atkinson JP. Inherited complement regulatory protein deficiency predisposes to human disease in acute injury and chronic inflammatory statesthe examples of vascular damage in atypical hemolytic uremic syndrome and debris accumulation in age-related macular degeneration. Adv Immunol 2007; 96:141-77. [PMID: 17981206 DOI: 10.1016/s0065-2776(07)96004-6] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
In this chapter, we examine the role of complement regulatory activity in atypical hemolytic uremic syndrome (aHUS) and age-related macular degeneration (AMD). These diseases are representative of two distinct types of complement-mediated injury, one being acute and self-limited, the other reflecting accumulation of chronic damage. Neither condition was previously thought to have a pathologic relationship to the immune system. However, alterations in complement regulatory protein genes have now been identified as major predisposing factors for the development of both diseases. In aHUS, heterozygous mutations leading to haploinsufficiency and function-altering polymorphisms in complement regulators have been identified, while in AMD, polymorphic haplotypes in complement genes are associated with development of disease. The basic premise is that a loss of function in a plasma or membrane inhibitor of the alternative complement pathway allows for excessive activation of complement on the endothelium of the kidney in aHUS and on retinal debris in AMD. These associations have much to teach us about the host's innate immune response to acute injury and to chronic debris deposition. We all experience cellular injury and, if we live long enough, will deposit debris in blood vessel walls (atherosclerosis leading to heart attacks and strokes), the brain (amyloid proteins leading to Alzheimer's disease), and retina (lipofuscin pigments leading to AMD). These are three common causes of morbidity and mortality in the developed world. The clinical, genetic, and immunopathologic understandings derived from the two examples of aHUS and AMD may illustrate what to anticipate in related conditions. They highlight how a powerful recognition and effector system, the alternative complement pathway, reacts to altered self. A response to acute injury or chronic debris accumulation must be appropriately balanced. In either case, too much activation or too little regulation promotes undesirable tissue damage and human disease.
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Affiliation(s)
- Anna Richards
- Washington University School of Medicine, St. Louis, Missouri, USA
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Hui KM, Orriss G, Schirmer T, Magnadóttir B, Schifferli J, Inal J. Expression of functional recombinant von Willebrand factor-A domain from human complement C2: a potential binding site for C4 and CRIT. Biochem J 2005; 389:863-8. [PMID: 15823096 PMCID: PMC1180737 DOI: 10.1042/bj20050183] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
CRIT (complement C2 receptor inhibitor trispanning) is a newly described transmembrane molecule that is capable of binding C2 via its first extracellular domain (ed1). CRIT competes with C4b for the binding of C2. Previous experiments have suggested that a major binding site for C2 is located on short, almost identical peptide sequences of CRIT-ed1 and the beta-chain of C4. The C2 domains involved in binding, however, remain unknown. We cloned the vWFA (von Willebrand factor-A) domain of C2, as it is a region likely to be involved in interactions with other proteins, and were able to functionally express the 25 kDa human complement C2 vWFA domain (amino acids 224-437). The recombinant vWFA protein fixed on MagneHis Ni-Particles bound C4 in normal human serum. The C4 alpha, beta and gamma chains were separated by SDS/PAGE and purified separately by electro-elution. The purified C4 chains were then used in a sandwich ELISA, which showed the vWFA to bind C4 only via the C4beta chain. In a haemolytic assay, the recombinant vWFA protein inhibited complement activation by the classical pathway in a dose-dependent manner by competing with native C2 for binding to C4b. vWFA bound the ed1 peptide of CRIT as well, and specifically to the 11-amino-acid peptide fragment of ed1 that is known to interact with whole C2. These findings show that the vWFA domain is centrally involved in the C2-CRIT and C2-C4b bindings. The cloned vWFA domain will allow us to dissect out the fine interactions between C2 and CRIT or C4b.
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Affiliation(s)
- Kwok-Min Hui
- *University Hospital Basel, Immunonephrology, Department of Research, Hebelstrasse 20, CH-4031 Basel, Switzerland
- Correspondence may be addressed to either of these authors (email or )
| | - George L. Orriss
- †Division of Structural Biology, Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland
| | - Tilman Schirmer
- †Division of Structural Biology, Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland
| | - Bergljót Magnadóttir
- ‡Institute for Experimental Pathology, University of Iceland, Keldur v. Vesturlandsveg, IS-112 Reykjavík, Iceland
| | - Jürg A. Schifferli
- *University Hospital Basel, Immunonephrology, Department of Research, Hebelstrasse 20, CH-4031 Basel, Switzerland
| | - Jameel M. Inal
- *University Hospital Basel, Immunonephrology, Department of Research, Hebelstrasse 20, CH-4031 Basel, Switzerland
- Correspondence may be addressed to either of these authors (email or )
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Abstract
The MHC, primarily known for its antigen-presenting class I and II molecules, harbours, within a central segment of less than 1 Mb, a dense collection of genes involved in various biological functions. Although MHC I and MHC II are principal players of adaptive immunity, several loci within this central (still called class III) MHC region encode members of the innate immune system. These include the long known factors of the complement system--potentially inhibitory and triggering natural killer receptors as well as stress proteins. Whether this physical proximity is fortuitous or functionally advantageous is an important question for the future of MHC genetics.
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Affiliation(s)
- Georges Hauptmann
- Centre de Recherche d'Immunologie et d'Hématologie, Faculté de Médecine, Hôpitaux Universitaires de Strasbourg, 4 rue Kirschleger, F-67085 Strasbourg Cedex, France.
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Mark L, Lee WH, Spiller OB, Proctor D, Blackbourn DJ, Villoutreix BO, Blom AM. The Kaposi's sarcoma-associated herpesvirus complement control protein mimics human molecular mechanisms for inhibition of the complement system. J Biol Chem 2004; 279:45093-101. [PMID: 15304516 DOI: 10.1074/jbc.m407558200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Kaposi's sarcoma-associated human herpesvirus (KSHV) is thought to cause Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman's disease. Previously, we reported that the KSHV complement control protein (KCP) encoded within the viral genome is a potent regulator of the complement system; it acts both as a cofactor for factor I and accelerates decay of the C3 convertases (Spiller, O. B., Blackbourn, D. J., Mark, L., Proctor, D. G., and Blom, A. M. (2003) J. Biol. Chem. 278, 9283-9289). KCP is a homologue to human complement regulators, being comprised of four complement control protein (CCP) domains. In this, the first study to identify the functional sites of a viral homologue at the amino acid level, we created a three-dimensional homology-based model followed by site-directed mutagenesis to locate complement regulatory sites. Classical pathway regulation, both through decay acceleration and factor I cleavage of C4b, required a cluster of positively charged amino acids in CCP1 stretching into CCP2 (Arg-20, Arg-33, Arg-35, Lys-64, Lys-65, and Lys-88) as well as positively (Lys-131, Lys-133, and His-135) and negatively (Glu-99, Glu-152, and Asp-155) charged areas at opposing faces of the border region between CCPs 2 and 3. The regulation of the alternative pathway (via factor I-mediated C3b cleavage) was found to both overlap with classical pathway regulatory sites (Lys-64, Lys-65, Lys-88 and Lys-131, Lys-133, His-135) as well as require unique, more C-terminal residues in CCPs 3 and 4 (His-158, His-171, and His-213) and CCP 4 (Phe-195, Phe-207, and Leu-209). We show here that KCP has evolved to maintain the spatial structure of its functional sites, especially the positively charged patches, compared with host complement regulators.
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Affiliation(s)
- Linda Mark
- Department of Clinical Chemistry, Lund University, University Hospital Malmö, S-20502 Malmö, Sweden
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