1
|
C3d(g), iron nanoparticles, hemin and cytochrome c may induce oxidative cytotoxicity in tumors and reduce tumor-associated myeloid cells-mediated immunosuppression. Med Hypotheses 2022. [DOI: 10.1016/j.mehy.2022.110944] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
|
2
|
Cortes C, Desler C, Mazzoli A, Chen JY, Ferreira VP. The role of properdin and Factor H in disease. Adv Immunol 2022; 153:1-90. [PMID: 35469595 DOI: 10.1016/bs.ai.2021.12.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The complement system consists of three pathways (alternative, classical, and lectin) that play a fundamental role in immunity and homeostasis. The multifunctional role of the complement system includes direct lysis of pathogens, tagging pathogens for phagocytosis, promotion of inflammatory responses to control infection, regulation of adaptive cellular immune responses, and removal of apoptotic/dead cells and immune complexes from circulation. A tight regulation of the complement system is essential to avoid unwanted complement-mediated damage to the host. This regulation is ensured by a set of proteins called complement regulatory proteins. Deficiencies or malfunction of these regulatory proteins may lead to pro-thrombotic hematological diseases, renal and ocular diseases, and autoimmune diseases, among others. This review focuses on the importance of two complement regulatory proteins of the alternative pathway, Factor H and properdin, and their role in human diseases with an emphasis on: (a) characterizing the main mechanism of action of Factor H and properdin in regulating the complement system and protecting the host from complement-mediated attack, (b) describing the dysregulation of the alternative pathway as a result of deficiencies, or mutations, in Factor H and properdin, (c) outlining the clinical findings, management and treatment of diseases associated with mutations and deficiencies in Factor H, and (d) defining the unwanted and inadequate functioning of properdin in disease, through a discussion of various experimental research findings utilizing in vitro, mouse and human models.
Collapse
Affiliation(s)
- Claudio Cortes
- Department of Foundational Medical Studies, Oakland University William Beaumont School of Medicine, Rochester, MI, United States.
| | - Caroline Desler
- Oakland University William Beaumont School of Medicine, Rochester, MI, United States
| | - Amanda Mazzoli
- Oakland University William Beaumont School of Medicine, Rochester, MI, United States
| | - Jin Y Chen
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States
| | - Viviana P Ferreira
- Department of Medical Microbiology and Immunology, University of Toledo College of Medicine and Life Sciences, Toledo, OH, United States.
| |
Collapse
|
3
|
Haque A, Cortes C, Alam MN, Sreedhar M, Ferreira VP, Pangburn MK. Characterization of Binding Properties of Individual Functional Sites of Human Complement Factor H. Front Immunol 2020; 11:1728. [PMID: 32849614 PMCID: PMC7417313 DOI: 10.3389/fimmu.2020.01728] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Accepted: 06/29/2020] [Indexed: 01/15/2023] Open
Abstract
Factor H exists as a 155,000 dalton, extended protein composed of twenty small domains which is flexible enough that it folds back on itself. Factor H regulates complement activation through its interactions with C3b and polyanions. Three binding sites for C3b and multiple polyanion binding sites have been identified on Factor H. In intact Factor H these sites appear to act synergistically making their individual contributions difficult to distinguish. Recombinantly expressed fragments of human Factor H were examined using surface plasmon resonance (SPR) for interactions with C3, C3b, iC3b, C3c, and C3d. Eleven recombinant proteins of lengths from one to twenty domains were used to show that the three C3b-binding sites exhibit 100-fold different affinities for C3b. The N-terminal site [complement control protein (CCP) domains 1-6] bound C3b with a Kd of 0.08 μM and this interaction was not influenced by the presence or absence of domains 7 and 8. Full length Factor H similarly exhibited a Kd for C3b of 0.1 μM. Unexpectedly, the N-terminal site (CCP 1-6) bound native C3 with a Kd of 0.4 μM. The C-terminal domains (CCP 19-20) exhibited a Kd of 1.7 μM for C3b. We localized a weak third C3b binding site in the CCP 13-15 region with a Kd estimated to be ~15 μM. The C-terminal site (CCP 19-20) bound C3b, iC3b, and C3d equally well with a Kd of 1 to 2 μM. In order to identify and compare regions of Factor H that interact with polyanions a family of 18 overlapping three domain recombinant proteins spanning the entire length of Factor H were expressed and purified. Immobilized heparin was used as a model polyanion and SPR confirmed the presence of heparin binding sites in CCP 6-8 (Kd 1.2 μM) and in CCP 19-20 (4.9 μM) and suggested the existence of a weak third polyanion binding site in the center of Factor H (CCP 11-13). Our results unveil the relative contributions of different regions of Factor H to its regulation of complement, and may contribute to the understanding of how defects in certain Factor H domains lead to disease.
Collapse
Affiliation(s)
- Aftabul Haque
- Center for Biomedical Research, University of Texas Health Science Center, Tyler, TX, United States.,The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - Claudio Cortes
- Department of Foundational Medical Sciences, Oakland University William Beaumont School of Medicine, Rochester, MI, United States
| | - M Nurul Alam
- Center for Biomedical Research, University of Texas Health Science Center, Tyler, TX, United States.,Department of Biology, College of Arts, Sciences, and Education, Texas A&M University-Texarkana, Texarkana, TX, United States
| | - Maladi Sreedhar
- Center for Biomedical Research, University of Texas Health Science Center, Tyler, TX, United States
| | - Viviana P Ferreira
- Department of Medical Microbiology and Immunology, University of Toledo College of Medicine, Toledo, OH, United States
| | - Michael K Pangburn
- Center for Biomedical Research, University of Texas Health Science Center, Tyler, TX, United States
| |
Collapse
|
4
|
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: 1011] [Impact Index Per Article: 112.3] [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.
Collapse
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
| |
Collapse
|
5
|
Perkins SJ, Fung KW, Khan S. Molecular Interactions between Complement Factor H and Its Heparin and Heparan Sulfate Ligands. Front Immunol 2014; 5:126. [PMID: 24744754 PMCID: PMC3978290 DOI: 10.3389/fimmu.2014.00126] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Accepted: 03/12/2013] [Indexed: 11/13/2022] Open
Abstract
Complement factor H (CFH) is the major regulator of the central complement protein C3b in the alternative pathway of complement activation. A molecular view of the CFH interaction with native heparan sulfate (HS) is central for understanding the mechanism of how surface-bound CFH interacts with C3b bound to host cell surfaces. HS is composed of sulfated heparin-like S-regions that alternate with desulfated NA-regions. Solution structural studies of heparin (equivalent to the S-regions) and desulfated HS (the NA-regions) by scattering and ultracentrifugation showed that each structure was mostly extended and partially bent, but with greater bending and flexibility in the NA-regions compared to the S-regions. Their solution structures have been deposited in the Protein Data Bank. The largest HS oligosaccharides showed more bent and flexible structures than those for heparin. A folded-back domain structure for the solution structure of the 20 domains in CFH was determined likewise. CFH binds to the S-regions but less so to the NA-regions of HS. The bivalent interaction of CFH–heparin was observed by ultracentrifugation, and binding studies of CFH fragments with heparin-coated sensor chips. In common with other CFH interactions with its physiological and pathophysiological ligands, the CFH–heparin and CFH–C3b interactions have moderate micromolar dissociation constants KD, meaning that these complexes do not fully form in vivo. The combination of the solution structures and binding studies indicated a two-site interaction model of CFH with heparin at cell surfaces. By this, the bivalent binding of CFH to a cell surface is co-operative. Defective interactions at either of the two independent CFH–heparin sites reduce the CFH interaction with surface-bound C3b and lead to immune disorders.
Collapse
Affiliation(s)
- Stephen J Perkins
- Department of Structural and Molecular Biology, University College London , London , UK
| | - Ka Wai Fung
- Department of Structural and Molecular Biology, University College London , London , UK
| | - Sanaullah Khan
- Department of Structural and Molecular Biology, University College London , London , UK
| |
Collapse
|
6
|
Wang Y, Song G, Wang Y, Qiu L, Qin X, Liu H, Li F, Wang X, Li F, Guo S, Zhang Y, Li Z. Elevated Serum Levels of Circulating Immunoinflammation-Related Protein Complexes Are Associated with Cancer. J Proteome Res 2013; 13:710-9. [DOI: 10.1021/pr4008255] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Yanying Wang
- Department of Biophysics and Structural Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing 100005, P. R. China
| | - Gaoguang Song
- Department of Biophysics and Structural Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing 100005, P. R. China
| | - Yanmin Wang
- Department
of Clinical Laboratory, Heze Municipal Hospital, Shandong 274031, P. R. China
| | - Ling Qiu
- Department of Clinical Laboratory, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100730, P. R. China
| | - Xuzhen Qin
- Department of Clinical Laboratory, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100730, P. R. China
| | - Hui Liu
- Department of Biophysics and Structural Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing 100005, P. R. China
| | - Fang Li
- Department of Biophysics and Structural Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing 100005, P. R. China
| | - Xiaodong Wang
- Department of Biophysics and Structural Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing 100005, P. R. China
| | - Fenjie Li
- Department of Biophysics and Structural Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing 100005, P. R. China
| | - Shuai Guo
- Department of Biophysics and Structural Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing 100005, P. R. China
| | - Yaping Zhang
- Department of Biophysics and Structural Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing 100005, P. R. China
| | - Zhili Li
- Department of Biophysics and Structural Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing 100005, P. R. China
| |
Collapse
|
7
|
Li K, Gor J, Holers VM, Storek MJ, Perkins SJ. Solution structure of TT30, a novel complement therapeutic agent, provides insight into its joint binding to complement C3b and C3d. J Mol Biol 2012; 418:248-63. [PMID: 22387467 DOI: 10.1016/j.jmb.2012.02.038] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2011] [Revised: 02/21/2012] [Accepted: 02/24/2012] [Indexed: 12/21/2022]
Abstract
A novel therapeutic reagent TT30 was designed to be effective in diseases of the alternative pathway of complement such as paroxysmal nocturnal hemoglobinuria and other diseases. TT30 is constructed from the first four short complement regulator (SCR) domains of complement receptor type 2 (CR2) that bind to complement C3d, followed by the first five SCR domains of complement factor H that bind to complement C3b. In order to assess how TT30 binds to C3d and C3b, we determined the TT30 solution structure by a combination of analytical ultracentrifugation, X-ray scattering and constrained modeling. The sedimentation coefficients and radius of gyration of TT30 were unaffected by citrate or phosphate-buffered saline buffers and indicate an elongated monomeric structure with a sedimentation coefficient of 3.1 S and a radius of gyration R(G) of 6.9 nm. Molecular modeling starting from 3000 randomized TT30 conformations showed that high-quality X-ray curve fits were obtained with extended SCR arrangements, showing that TT30 has a limited degree of inter-SCR flexibility in its solution structure. The best-fit TT30 structural models are readily merged with the crystal structure of C3b to show that the four CR2 domains extend freely into solution when the five complement factor H domains are bound within C3b. We reevaluated the solution structure of the CR2-C3d complex that confirmed its recent crystal structure. This recent CR2-C3d crystal structure showed that TT30 is able to interact readily with C3d ligands in many orientations when TT30 is bound to C3b.
Collapse
Affiliation(s)
- Keying Li
- Department of Structural and Molecular Biology, Darwin Building, University College London, Gower Street, London WC1E 6BT, UK
| | | | | | | | | |
Collapse
|
8
|
Complement factor H-ligand interactions: self-association, multivalency and dissociation constants. Immunobiology 2011; 217:281-97. [PMID: 22137027 DOI: 10.1016/j.imbio.2011.10.003] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2011] [Revised: 10/07/2011] [Accepted: 10/13/2011] [Indexed: 11/21/2022]
Abstract
Factor H (FH) is the major plasma regulator of the central complement protein C3b in the alternative pathway of complement activation. The elucidation of the FH interactions with five major ligands (below) is complicated by their weak μM dissociation constants K(D) and FH multivalency. We present the first survey of all the K(D) values for the major FH-ligand interactions and critically review their physiological significance. (i) FH self-association is presently well-established. We review multiple data sets that show that 5-14% of FH is self-associated in physiological conditions. FH self-association is significant for both laboratory investigations and physiological function.(ii) The FH-C3b complex shows low M affinity, meaning that the complex is not fully formed in plasma. In addition, C3, its hydrolysed form C3u, and its cleaved forms C3b and C3d show multimerisation. Current data favour a model when two C3b molecules bind independently to one FH molecule, as opposed to a1:1 stoichiometry where FH wraps itself around C3b.(iii) Heparin is often used as an analogue of the polyanionic host cell surface. The FH-heparin complex also shows a low M affinity, again meaning that complexes are not fully formed in vivo. The oligomeric FH-heparin complexes clarify a two-site interaction model of FH with host-cell surfaces.(iv) Reinvestigation of the FH and C-reactive protein (CRP) interaction revealed that this can only occur in plasma when CRP levels are elevated during acute-phase conditions. Given that CRP binds more weakly to the His402 allotype of FH than the Tyr402 allotype, this suggested a link with age-related macular degeneration (AMD).(v) FH activity is inhibited by zinc, which causes FH to aggregate strongly. High levels of bioavailable zinc occur in sub-retinal pigment epithelial deposits which lead to AMD. Excess zinc binds weakly to a central region of FH, explaining how zinc inhibits FH regulation of C3b.
Collapse
|
9
|
The effect of electrostatics on factor H function and related pathologies. J Mol Graph Model 2011; 29:1047-55. [PMID: 21605993 DOI: 10.1016/j.jmgm.2011.04.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2011] [Revised: 04/26/2011] [Accepted: 04/28/2011] [Indexed: 12/15/2022]
Abstract
Factor H (FH) contributes to the regulation of the complement system by binding to polyanionic surfaces and the proteins C3b/C3c/C3d. This implicates charge and electrostatic interactions in recognition and binding of FH. Despite the large amount of experimental and pathology data the exact mechanism at molecular level is not yet known. We have implemented a computational framework for comparative analysis of the charge and electrostatic diversity of FH modules and C3b domains to identify electrostatic hotspots and predict potential binding sites. Our electrostatic potential clustering analysis shows that charge distributions and electrostatic potential distributions are more useful in understanding C3b-FH interactions than net charges alone. We present a model of non-specific electrostatic interactions of FH with polyanion-rich surfaces and specific interactions with C3b, using our computational data and existing experimental data. We discuss the electrostatic contributions to the formation of the C3b-FH complex and the competition between FH and Factor Bb (Bb) for binding to C3b. We also discuss the significance of mutations of charged amino acids in the pathobiology of FH-mediated disease, such as age-related macular degeneration, atypical hemolytic uremic syndrome, and dense deposit disease. Our data can be used to guide future experimental studies.
Collapse
|
10
|
Nan R, Farabella I, Schumacher FF, Miller A, Gor J, Martin ACR, Jones DT, Lengyel I, Perkins SJ. Zinc binding to the Tyr402 and His402 allotypes of complement factor H: possible implications for age-related macular degeneration. J Mol Biol 2011; 408:714-35. [PMID: 21396937 PMCID: PMC3092982 DOI: 10.1016/j.jmb.2011.03.006] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2011] [Accepted: 03/01/2011] [Indexed: 12/29/2022]
Abstract
The Tyr402His polymorphism of complement factor H (FH) with 20 short complement regulator (SCR) domains is associated with age-related macular degeneration (AMD). How FH contributes to disease pathology is not clear. Both FH and high concentrations of zinc are found in drusen deposits, the key feature of AMD. Heterozygous FH is inhibited by zinc, which causes FH to aggregate. Here, zinc binding to homozygous FH was studied. By analytical ultracentrifugation, large amounts of oligomers were observed with both the native Tyr402 and the AMD-risk His402 homozygous allotypes of FH and both the recombinant SCR-6/8 allotypes with Tyr/His402. X-ray scattering also showed that both FH and SCR-6/8 allotypes strongly aggregated at > 10 μM zinc. The SCR-1/5 and SCR-16/20 fragments were less likely to bind zinc. These observations were supported by bioinformatics predictions. Starting from known zinc binding sites in crystal structures, we predicted 202 putative partial surface zinc binding sites in FH, most of which were in SCR-6. Metal site prediction web servers also suggested that SCR-6 and other domains bind zinc. Predicted SCR-6/8 dimer structures showed that zinc binding sites could be formed at the protein–protein interface that would lead to daisy-chained oligomers. It was concluded that zinc binds weakly to FH at multiple surface locations, most probably within the functionally important SCR-6/8 domains, and this explains why zinc inhibits FH activity. Given the high pathophysiological levels of bioavailable zinc present in subretinal deposits, we discuss how zinc binding to FH may contribute to deposit formation and inflammation associated with AMD.
Collapse
Affiliation(s)
- Ruodan Nan
- Department of Structural and Molecular Biology, Division of Biosciences, Darwin Building, University College London, Gower Street, London WC1E 6BT, UK
| | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Perkins SJ, Nan R, Okemefuna AI, Li K, Khan S, Miller A. Multiple interactions of complement Factor H with its ligands in solution: a progress report. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 703:25-47. [PMID: 20711705 DOI: 10.1007/978-1-4419-5635-4_3] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/25/2023]
Abstract
Factor H (FH) is the major regulator of the central complement protein C3b in the alternative pathway of complement activation, and is comprised of 20 SCR domains. A FH Tyr402His polymorphism in SCR-7 is associated with age-related macular degeneration (AMD) and leads to deposition of complement in drusen. The unravelling of how FH interacts with five major physiological and patho-physiological ligands is complicated by the weak nature of these interactions, coupled with the multivalency of FH. Using multiple biophysical methods, we summarise our recent results for these five FH ligands: (1) FH by itself shows a folded-back SCR domain structure in solution, and self-associates in a manner dependent on electrostatic forces. (2) FH activity is inhibited by zinc, which causes FH to aggregate. The onset of FH-zinc aggregation for zinc concentrations above 20 muM appears to be enhanced with the His402 allotype, and may be relevant to AMD. (3) The FH and C-reactive protein (CRP) interaction has been controversial; however our new work resolves earlier discrepancies. The FH-CRP interaction is only observed when native CRP is at high acute-phase concentration levels, and CRP binds weakly to the His402 FH allotype to suggest a molecular mechanism that leads to AMD. (4) Heparin is an analogue of the polyanionic host cell surface, and FH forms higher oligomers with larger heparin fragments, suggesting a mechanism for more effective FH regulation. (5) The interaction of C3b with FH also depends on buffer, and FH forms multimers with the C3d fragment of C3b. This FH-C3d interaction at high FH concentration may also facilitate complement regulation. Overall, our results to date suggest that the FH interactions involving zinc and native CRP have the closest relevance for explaining the onset of AMD.
Collapse
Affiliation(s)
- Stephen J Perkins
- Department of Structural and Molecular Biology, University College London, London, UK.
| | | | | | | | | | | |
Collapse
|
12
|
Perkins SJ, Nan R, Li K, Khan S, Abe Y. Analytical ultracentrifugation combined with X-ray and neutron scattering: Experiment and modelling. Methods 2011; 54:181-99. [PMID: 21256219 DOI: 10.1016/j.ymeth.2011.01.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2010] [Revised: 12/30/2010] [Accepted: 01/13/2011] [Indexed: 10/18/2022] Open
Abstract
Analytical ultracentrifugation and solution scattering provide different multi-parameter structural and compositional information on proteins. The joint application of the two methods supplements high resolution structural studies by crystallography and NMR. We summarise the procedures required to obtain equivalent ultracentrifugation and X-ray and neutron scattering data. The constrained modelling of ultracentrifugation and scattering data is important to confirm the experimental data analysis and yields families of best-fit molecular models for comparison with crystallography and NMR structures. This modelling of ultracentrifugation and scattering data is described in terms of starting models, their conformational randomisation in trial-and-error fits, and the identification of the final best-fit models. Seven applications of these methods are described to illustrate the current state-of-the-art. These include the determination of antibody solution structures (the human IgG4 subclass, and oligomeric forms of human IgA and its secretory component), the solution structures of the complement proteins of innate immunity (Factor H and C3/C3u) and their interactions with macromolecular ligands (C-reactive protein), and anionic polysaccharides (heparin). Complementary features of joint ultracentrifugation and scattering experiments facilitate an improved understanding of crystal structures (illustrated for C3/C3u, C-reactive protein and heparin). If a large protein or its complex cannot be crystallised, the joint ultracentrifugation-scattering approach provides a means to obtain an overall macromolecular structure.
Collapse
Affiliation(s)
- Stephen J Perkins
- Department of Structural and Molecular Biology, University College London, Gower Street, London WC1E 6BT, UK.
| | | | | | | | | |
Collapse
|
13
|
Abstract
Central to the pathogenesis of atypical hemolytic uremic syndrome (aHUS) is over-activation of the alternative pathway of complement. Following the initial discovery of mutations in the complement regulatory protein, factor H, mutations have been described in factor I, membrane cofactor protein and thrombomodulin, which also result in decreased complement regulation. Autoantibodies to factor H have also been reported to impair complement regulation in aHUS. More recently, gain of function mutations in the complement components C3 and Factor B have been seen. This review focuses on the genetic causes of aHUS, their functional consequences, and clinical effect.
Collapse
|
14
|
Self-association and domain rearrangements between complement C3 and C3u provide insight into the activation mechanism of C3. Biochem J 2010; 431:63-72. [PMID: 20666732 DOI: 10.1042/bj20100759] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Component C3 is the central protein of the complement system. During complement activation, the thioester group in C3 is slowly hydrolysed to form C3u, then the presence of C3u enables the rapid conversion of C3 into functionally active C3b. C3u shows functional similarities to C3b. To clarify this mechanism, the self-association properties and solution structures of C3 and C3u were determined using analytical ultracentrifugation and X-ray scattering. Sedimentation coefficients identified two different dimerization events in both proteins. A fast dimerization was observed in 50 mM NaCl but not in 137 mM NaCl. Low amounts of a slow dimerization was observed for C3u and C3 in both buffers. The X-ray radius of gyration RG values were unchanged for both C3 and C3u in 137 mM NaCl, but depend on concentration in 50 mM NaCl. The C3 crystal structure gave good X-ray fits for C3 in 137 mM NaCl. By randomization of the TED (thioester-containing domain)/CUB (for complement protein subcomponents C1r/C1s, urchin embryonic growth factor and bone morphogenetic protein 1) domains in the C3b crystal structure, X-ray fits showed that the TED/CUB domains in C3u are extended and differ from the more compact arrangement of C3b. This TED/CUB conformation is intermediate between those of C3 and C3b. The greater exposure of the TED domain in C3u (which possesses the hydrolysed reactive thioester) accounts for the greater self-association of C3u in low-salt conditions. This conformational variability of the TED/CUB domains would facilitate their interactions with a broad range of antigenic surfaces. The second dimerization of C3 and C3u may correspond to a dimer observed in one of the crystal structures of C3b.
Collapse
|
15
|
Siegel C, Hallström T, Skerka C, Eberhardt H, Uzonyi B, Beckhaus T, Karas M, Wallich R, Stevenson B, Zipfel PF, Kraiczy P. Complement factor H-related proteins CFHR2 and CFHR5 represent novel ligands for the infection-associated CRASP proteins of Borrelia burgdorferi. PLoS One 2010; 5:e13519. [PMID: 20975954 PMCID: PMC2958145 DOI: 10.1371/journal.pone.0013519] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2010] [Accepted: 09/21/2010] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND One virulence property of Borrelia burgdorferi is its resistance to innate immunity, in particular to complement-mediated killing. Serum-resistant B. burgdorferi express up to five distinct complement regulator-acquiring surface proteins (CRASP) which interact with complement regulator factor H (CFH) and factor H-like protein 1 (FHL1) or factor H-related protein 1 (CFHR1). In the present study we elucidate the role of the infection-associated CRASP-3 and CRASP-5 protein to serve as ligands for additional complement regulatory proteins as well as for complement resistance of B. burgdorferi. METHODOLOGY/PRINCIPAL FINDINGS To elucidate whether CRASP-5 and CRASP-3 interact with various human proteins, both borrelial proteins were immobilized on magnetic beads. Following incubation with human serum, bound proteins were eluted and separated by Glycine-SDS-PAGE. In addition to CFH and CFHR1, complement regulators CFHR2 and CFHR5 were identified as novel ligands for both borrelial proteins by employing MALDI-TOF. To further assess the contributions of CRASP-3 and CRASP-5 to complement resistance, a serum-sensitive B. garinii strain G1 which lacks all CFH-binding proteins was used as a valuable model for functional analyses. Both CRASPs expressed on the B. garinii outer surface bound CFH as well as CFHR1 and CFHR2 in ELISA. In contrast, live B. garinii bound CFHR1, CFHR2, and CFHR5 and only miniscute amounts of CFH as demonstrated by serum adsorption assays and FACS analyses. Further functional analysis revealed that upon NHS incubation, CRASP-3 or CRASP-5 expressing borreliae were killed by complement. CONCLUSIONS/SIGNIFICANCE In the absence of CFH and the presence of CFHR1, CFHR2 and CFHR5, assembly and integration of the membrane attack complex was not efficiently inhibited indicating that CFH in co-operation with CFHR1, CFHR2 and CFHR5 supports complement evasion of B. burgdorferi.
Collapse
Affiliation(s)
- Corinna Siegel
- Institute of Medical Microbiology and Infection Control, University Hospital of Frankfurt, Frankfurt/Main, Germany
| | - Teresia Hallström
- Department of Infection Biology, Leibniz-Institute for Natural Products Research and Infection Biology, Jena, Germany
| | - Christine Skerka
- Department of Infection Biology, Leibniz-Institute for Natural Products Research and Infection Biology, Jena, Germany
| | - Hannes Eberhardt
- Department of Infection Biology, Leibniz-Institute for Natural Products Research and Infection Biology, Jena, Germany
| | - Barbara Uzonyi
- Department of Infection Biology, Leibniz-Institute for Natural Products Research and Infection Biology, Jena, Germany
| | - Tobias Beckhaus
- Institute of Pharmaceutical Chemistry, Johann Wolfgang Goethe-University, Frankfurt/Main, Germany
| | - Michael Karas
- Institute of Pharmaceutical Chemistry, Johann Wolfgang Goethe-University, Frankfurt/Main, Germany
| | - Reinhard Wallich
- Institute of Immunology, University of Heidelberg, Heidelberg, Germany
| | - Brian Stevenson
- Department of Microbiology, Immunology and Molecular Genetics, University of Kentucky, Lexington, Kentucky, United States of America
| | - Peter F. Zipfel
- Department of Infection Biology, Leibniz-Institute for Natural Products Research and Infection Biology, Jena, Germany
- Friedrich Schiller University, Jena, Germany
| | - Peter Kraiczy
- Institute of Medical Microbiology and Infection Control, University Hospital of Frankfurt, Frankfurt/Main, Germany
- * E-mail:
| |
Collapse
|
16
|
Ferreira VP, Pangburn MK, Cortés C. Complement control protein factor H: the good, the bad, and the inadequate. Mol Immunol 2010; 47:2187-97. [PMID: 20580090 DOI: 10.1016/j.molimm.2010.05.007] [Citation(s) in RCA: 300] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The complement system is an essential component of the innate immune system that participates in elimination of pathogens and altered host cells and comprises an essential link between the innate and adaptive immune system. Soluble and membrane-bound complement regulators protect cells and tissues from unintended complement-mediated injury. Complement factor H is a soluble complement regulator essential for controlling the alternative pathway in blood and on cell surfaces. Normal recognition of self-cell markers (i.e. polyanions) and C3b/C3d fragments is necessary for factor H function. Inadequate recognition of host cell surfaces by factor H due to mutations and polymorphisms have been associated with complement-mediated tissue damage and disease. On the other hand, unwanted recognition of pathogens and altered self-cells (i.e. cancer) by factor H is used as an immune evasion strategy. This review will focus on the current knowledge related to these versatile recognition properties of factor H.
Collapse
Affiliation(s)
- Viviana P Ferreira
- Department of Medical Microbiology and Immunology, College of Medicine, University of Toledo, Toledo, OH 43614, United States.
| | | | | |
Collapse
|
17
|
Okemefuna AI, Nan R, Miller A, Gor J, Perkins SJ. Complement factor H binds at two independent sites to C-reactive protein in acute phase concentrations. J Biol Chem 2010; 285:1053-65. [PMID: 19850925 PMCID: PMC2801232 DOI: 10.1074/jbc.m109.044529] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2009] [Revised: 10/13/2009] [Indexed: 01/10/2023] Open
Abstract
Factor H (FH) regulates the activation of C3b in the alternative complement pathway, both in serum and at host cell surfaces. It is composed of 20 short complement regulator (SCR) domains. The Y402H polymorphism in FH is a risk factor for age-related macular degeneration. C-reactive protein (CRP) is an acute phase protein that binds Ca(2+). We established the FH-CRP interaction using improved analytical ultracentrifugation (AUC), surface plasmon resonance (SPR), and synchrotron x-ray scattering methods. Physiological FH and CRP concentrations were used in 137 mM NaCl and 2 mM Ca(2+), in which the occurrence of denatured CRP was avoided. In solution, AUC revealed FH-CRP binding. The FH-CRP interaction inhibited the formation of higher FH oligomers, indicating that CRP blocked FH dimerization sites at both SCR-6/8 and SCR-16/20. SPR confirmed the FH-CRP interaction and its NaCl concentration dependence upon using either immobilized FH or CRP. The SCR-1/5 fragment of FH did not bind to CRP. In order of increasing affinity, SCR-16/20, SCR-6/8 (His-402), and SCR-6/8 (Tyr-402) fragments bound to CRP. X-ray scattering showed that FH became more compact when binding to CRP, which is consistent with CRP binding at two different FH sites. We concluded that FH and CRP bind at elevated acute phase concentrations of CRP in physiological buffer. The SCR-16/20 site is novel and indicates the importance of the FH-CRP interaction for both age-related macular degeneration and atypical hemolytic uremic syndrome.
Collapse
Affiliation(s)
- Azubuike I. Okemefuna
- From the Department of Structural and Molecular Biology, Darwin Building, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Ruodan Nan
- From the Department of Structural and Molecular Biology, Darwin Building, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Ami Miller
- From the Department of Structural and Molecular Biology, Darwin Building, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Jayesh Gor
- From the Department of Structural and Molecular Biology, Darwin Building, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Stephen J. Perkins
- From the Department of Structural and Molecular Biology, Darwin Building, University College London, Gower Street, London WC1E 6BT, United Kingdom
| |
Collapse
|
18
|
Perkins SJ, Okemefuna AI, Nan R, Li K, Bonner A. Constrained solution scattering modelling of human antibodies and complement proteins reveals novel biological insights. J R Soc Interface 2009; 6 Suppl 5:S679-96. [PMID: 19605402 DOI: 10.1098/rsif.2009.0164.focus] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
X-ray and neutron-scattering techniques characterize proteins in solution and complement high-resolution structural studies. They are useful when either a large protein cannot be crystallized, in which case scattering yields a solution structure, or a crystal structure has been determined and requires validation in solution. These solution structures are determined by the application of constrained modelling methods based on known subunit structures. First, an appropriate starting model is generated. Next, its conformation is randomized to generate thousands of models for trial-and-error fits. Comparison with the experimental data identifies a small family of best-fit models. Finally, their significance for biological function is assessed. We illustrate this in application to structure determinations for secretory immunoglobulin A, the most prevalent antibody in the human body and a first line of defence in mucosal immunity. We also discuss the applications to the large multi-domain proteins of the complement system, most notably its major regulator factor H, which is important in age-related macular degeneration and renal diseases. We discuss the importance of complementary data from analytical ultracentrifugation, and structural studies of protein-protein complexes. We conclude that constrained scattering modelling makes useful contributions to our understanding of antibody and complement structure and function.
Collapse
Affiliation(s)
- Stephen J Perkins
- Department of Structural and Molecular Biology, University College London, Darwin Building, Gower Street, London WC1E 6BT, UK.
| | | | | | | | | |
Collapse
|
19
|
Okemefuna AI, Nan R, Gor J, Perkins SJ. Electrostatic interactions contribute to the folded-back conformation of wild type human factor H. J Mol Biol 2009; 391:98-118. [PMID: 19505476 DOI: 10.1016/j.jmb.2009.06.010] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2009] [Revised: 05/27/2009] [Accepted: 06/03/2009] [Indexed: 11/28/2022]
Abstract
Factor H (FH), a major serum regulator of C3b in the complement alternative pathway, is composed of 20 short complement regulator (SCR) domains. Earlier solution structures for FH showed that this has a folded-back domain arrangement and exists as oligomers. To clarify the molecular basis for this, analytical ultracentrifugation and X-ray scattering studies of native FH were performed as a function of NaCl concentration and pH. The sedimentation coefficient for the FH monomer decreased from 5.7 S to 5.3 S with increase in NaCl concentration, showing that weak electrostatic inter-domain interactions affect its folded-back structure. FH became more elongated at pH 9.4, showing the involvement of histidine residue(s) in its folded-back structure. Similar studies of partially deglycosylated FH suggested that oligosaccharides were not significant in determining the FH domain structure. The formation of FH oligomers decreased with increased NaCl concentration, indicating that electrostatic interactions also affect this. X-ray scattering showed that the maximum length of FH increased from 32 nm in low salt to 38 nm in high salt. Constrained X-ray scattering modelling was used to generate significantly improved FH molecular structures at medium resolution. In 50 mM NaCl, the modelled structures showed that inter-SCR domain contacts are likely, while these contacts are fewer in 250 mM NaCl. The results of this study show that the conformation of FH is affected by its local environment, and this may be important for its interactions with C3b and when bound to polyanionic cell surfaces.
Collapse
Affiliation(s)
- Azubuike I Okemefuna
- Institute of Structural and Molecular Biology, Division of Biosciences, Darwin Building, University College London, Gower Street, London, UK
| | | | | | | |
Collapse
|