1
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Lorvellec M, Chouquet A, Koch J, Bally I, Signor L, Vigne J, Dalonneau F, Thielens NM, Rabilloud T, Dalzon B, Rossi V, Gaboriaud C. HMGB1 cleavage by complement C1s and its potent anti-inflammatory product. Front Immunol 2023; 14:1151731. [PMID: 37180096 PMCID: PMC10169756 DOI: 10.3389/fimmu.2023.1151731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Accepted: 04/11/2023] [Indexed: 05/15/2023] Open
Abstract
Complement C1s association with the pathogenesis of several diseases cannot be simply explained only by considering its main role in activating the classical complement pathway. This suggests that non-canonical functions are to be deciphered for this protease. Here the focus is on C1s cleavage of HMGB1 as an auxiliary target. HMGB1 is a chromatin non-histone nuclear protein, which exerts in fact multiple functions depending on its location and its post-translational modifications. In the extracellular compartment, HMGB1 can amplify immune and inflammatory responses to danger associated molecular patterns, in health and disease. Among possible regulatory mechanisms, proteolytic processing could be highly relevant for HMGB1 functional modulation. The unique properties of HMGB1 cleavage by C1s are analyzed in details. For example, C1s cannot cleave the HMGB1 A-box fragment, which has been described in the literature as an inhibitor/antagonist of HMGB1. By mass spectrometry, C1s cleavage was experimentally identified to occur after lysine on position 65, 128 and 172 in HMGB1. Compared to previously identified C1s cleavage sites, the ones identified here are uncommon, and their analysis suggests that local conformational changes are required before cleavage at certain positions. This is in line with the observation that HMGB1 cleavage by C1s is far slower when compared to human neutrophil elastase. Recombinant expression of cleavage fragments and site-directed mutagenesis were used to confirm these results and to explore how the output of C1s cleavage on HMGB1 is finely modulated by the molecular environment. Furthermore, knowing the antagonist effect of the isolated recombinant A-box subdomain in several pathophysiological contexts, we wondered if C1s cleavage could generate natural antagonist fragments. As a functional readout, IL-6 secretion following moderate LPS activation of RAW264.7 macrophage was investigated, using LPS alone or in complex with HMGB1 or some recombinant fragments. This study revealed that a N-terminal fragment released by C1s cleavage bears stronger antagonist properties as compared to the A-box, which was not expected. We discuss how this fragment could provide a potent brake for the inflammatory process, opening the way to dampen inflammation.
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Affiliation(s)
- Marie Lorvellec
- Institute of Structural Biology (IBS), University Grenoble Alpes, CEA, CNRS, Grenoble, France
| | - Anne Chouquet
- Institute of Structural Biology (IBS), University Grenoble Alpes, CEA, CNRS, Grenoble, France
| | - Jonas Koch
- Institute of Structural Biology (IBS), University Grenoble Alpes, CEA, CNRS, Grenoble, France
| | - Isabelle Bally
- Institute of Structural Biology (IBS), University Grenoble Alpes, CEA, CNRS, Grenoble, France
| | - Luca Signor
- Institute of Structural Biology (IBS), University Grenoble Alpes, CEA, CNRS, Grenoble, France
| | - Jeanne Vigne
- Institute of Structural Biology (IBS), University Grenoble Alpes, CEA, CNRS, Grenoble, France
| | - Fabien Dalonneau
- Institute of Structural Biology (IBS), University Grenoble Alpes, CEA, CNRS, Grenoble, France
| | - Nicole M. Thielens
- Institute of Structural Biology (IBS), University Grenoble Alpes, CEA, CNRS, Grenoble, France
| | - Thierry Rabilloud
- Chemistry and Biology of Metals, University Grenoble Alpes, CNRS UMR 5249, CEA, IRIG-LCBM, Grenoble, France
| | - Bastien Dalzon
- Chemistry and Biology of Metals, University Grenoble Alpes, CNRS UMR 5249, CEA, IRIG-LCBM, Grenoble, France
| | - Véronique Rossi
- Institute of Structural Biology (IBS), University Grenoble Alpes, CEA, CNRS, Grenoble, France
| | - Christine Gaboriaud
- Institute of Structural Biology (IBS), University Grenoble Alpes, CEA, CNRS, Grenoble, France
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2
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Booth CE, Powell-Pierce AD, Skare JT, Garcia BL. Borrelia miyamotoi FbpA and FbpB Are Immunomodulatory Outer Surface Lipoproteins With Distinct Structures and Functions. Front Immunol 2022; 13:886733. [PMID: 35693799 PMCID: PMC9186069 DOI: 10.3389/fimmu.2022.886733] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Accepted: 04/19/2022] [Indexed: 01/04/2023] Open
Abstract
Pathogens that traffic in the blood of their hosts must employ mechanisms to evade the host innate immune system, including the complement cascade. The Lyme disease spirochete, Borreliella burgdorferi, has evolved numerous outer membrane lipoproteins that interact directly with host proteins. Compared to Lyme disease-associated spirochetes, relatively little is known about how an emerging tick-borne spirochetal pathogen, Borrelia miyamotoi, utilizes surface lipoproteins to interact with a human host. B. burgdorferi expresses the multifunctional lipoprotein, BBK32, that inhibits the classical pathway of complement through interaction with the initiating protease C1r, and also interacts with fibronectin using a separate intrinsically disordered domain. B. miyamotoi encodes two separate bbk32 orthologs denoted fbpA and fbpB; however, the activities of these proteins are unknown. Here, we show that B. miyamotoi FbpA binds human fibronectin in a manner similar to B. burgdorferi BBK32, whereas FbpB does not. FbpA and FbpB both bind human complement C1r and protect a serum-sensitive B. burgdorferi strain from complement-mediated killing, but surprisingly, differ in their ability to recognize activated C1r versus zymogen states of C1r. To better understand the observed differences in C1r recognition and inhibition properties, high-resolution X-ray crystallography structures were solved of the C1r-binding regions of B. miyamotoi FbpA and FbpB at 1.9Å and 2.1Å, respectively. Collectively, these data suggest that FbpA and FbpB have partially overlapping functions but are functionally and structurally distinct. The data presented herein enhances our overall understanding of how bloodborne pathogens interact with fibronectin and modulate the complement system.
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Affiliation(s)
- Charles E Booth
- Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, NC, United States
| | - Alexandra D Powell-Pierce
- Department of Microbial Pathogenesis and Immunology, College of Medicine, Texas A&M University, Bryan, TX, United States
| | - Jon T Skare
- Department of Microbial Pathogenesis and Immunology, College of Medicine, Texas A&M University, Bryan, TX, United States
| | - Brandon L Garcia
- Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, NC, United States
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3
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Garrigues RJ, Powell-Pierce AD, Hammel M, Skare JT, Garcia BL. A Structural Basis for Inhibition of the Complement Initiator Protease C1r by Lyme Disease Spirochetes. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2021; 207:2856-2867. [PMID: 34759015 PMCID: PMC8612984 DOI: 10.4049/jimmunol.2100815] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Accepted: 09/23/2021] [Indexed: 12/26/2022]
Abstract
Complement evasion is a hallmark of extracellular microbial pathogens such as Borrelia burgdorferi, the causative agent of Lyme disease. Lyme disease spirochetes express nearly a dozen outer surface lipoproteins that bind complement components and interfere with their native activities. Among these, BBK32 is unique in its selective inhibition of the classical pathway. BBK32 blocks activation of this pathway by selectively binding and inhibiting the C1r serine protease of the first component of complement, C1. To understand the structural basis for BBK32-mediated C1r inhibition, we performed crystallography and size-exclusion chromatography-coupled small angle X-ray scattering experiments, which revealed a molecular model of BBK32-C in complex with activated human C1r. Structure-guided site-directed mutagenesis was combined with surface plasmon resonance binding experiments and assays of complement function to validate the predicted molecular interface. Analysis of the structures shows that BBK32 inhibits activated forms of C1r by occluding substrate interaction subsites (i.e., S1 and S1') and reveals a surprising role for C1r B loop-interacting residues for full inhibitory activity of BBK32. The studies reported in this article provide for the first time (to our knowledge) a structural basis for classical pathway-specific inhibition by a human pathogen.
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Affiliation(s)
- Ryan J Garrigues
- Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, NC
| | - Alexandra D Powell-Pierce
- Department of Microbial Pathogenesis and Immunology, College of Medicine, Texas A&M University, Bryan/College Station, TX; and
| | - Michal Hammel
- Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA
| | - Jon T Skare
- Department of Microbial Pathogenesis and Immunology, College of Medicine, Texas A&M University, Bryan/College Station, TX; and
| | - Brandon L Garcia
- Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, NC;
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4
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Targeting the Initiator Protease of the Classical Pathway of Complement Using Fragment-Based Drug Discovery. Molecules 2020; 25:molecules25174016. [PMID: 32899120 PMCID: PMC7504721 DOI: 10.3390/molecules25174016] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 08/30/2020] [Accepted: 09/01/2020] [Indexed: 12/23/2022] Open
Abstract
The initiating protease of the complement classical pathway, C1r, represents an upstream and pathway-specific intervention point for complement-related autoimmune and inflammatory diseases. Yet, C1r-targeted therapeutic development is currently underrepresented relative to other complement targets. In this study, we developed a fragment-based drug discovery approach using surface plasmon resonance (SPR) and molecular modeling to identify and characterize novel C1r-binding small-molecule fragments. SPR was used to screen a 2000-compound fragment library for binding to human C1r. This led to the identification of 24 compounds that bound C1r with equilibrium dissociation constants ranging between 160–1700 µM. Two fragments, termed CMP-1611 and CMP-1696, directly inhibited classical pathway-specific complement activation in a dose-dependent manner. CMP-1611 was selective for classical pathway inhibition, while CMP-1696 also blocked the lectin pathway but not the alternative pathway. Direct binding experiments mapped the CMP-1696 binding site to the serine protease domain of C1r and molecular docking and molecular dynamics studies, combined with C1r autoactivation assays, suggest that CMP-1696 binds within the C1r active site. The group of structurally distinct fragments identified here, along with the structure–activity relationship profiling of two lead fragments, form the basis for future development of novel high-affinity C1r-binding, classical pathway-specific, small-molecule complement inhibitors.
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A wealth of genotype-specific proteoforms fine-tunes hemoglobin scavenging by haptoglobin. Proc Natl Acad Sci U S A 2020; 117:15554-15564. [PMID: 32561649 PMCID: PMC7355005 DOI: 10.1073/pnas.2002483117] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Haptoglobin (Hp) is one of the most abundant plasma proteins; it binds with high affinity to hemoglobin (Hb). Thereby Hp protects against the toxic effects of the heme when Hb leaks into plasma from damaged red blood cells. Therefore, serum Hp is an important antioxidant and a clinically important protein, often used as a protein biomarker. Here, we address in detail what proteoforms and proteoform assemblies co-occur in serum, and show how they differ in individuals with distinct genotypes. Our data, obtained by a range of state-of-the-art analytical methods, reveal in unprecedented detail how these hundreds of Hp proteoforms influence the scavenging of Hb through several distinctive molecular features of Hp genotypes. The serum haptoglobin protein (Hp) scavenges toxic hemoglobin (Hb) leaked into the bloodstream from erythrocytes. In humans, there are two frequently occurring allelic forms of Hp, resulting in three genotypes: Homozygous Hp 1-1 and Hp 2-2, and heterozygous Hp 2-1. The Hp genetic polymorphism has an intriguing effect on the quaternary structure of Hp. The simplest form, Hp 1-1, forms dimers consisting of two α1β units, connected by disulfide bridges. Hp 2-1 forms mixtures of linear (α1)2(α2)n-2(β)n oligomers (n > 1) while Hp 2-2 occurs in cyclic (α2)n(β)n oligomers (n > 2). Different Hp genotypes bind Hb with different affinities, with Hp 2-2 being the weakest binder. This behavior has a significant influence on Hp’s antioxidant capacity, with potentially distinctive personalized clinical consequences. Although Hp has been studied extensively in the past, the finest molecular details of the observed differences in interactions between Hp and Hb are not yet fully understood. Here, we determined the full proteoform profiles and proteoform assemblies of all three most common genetic Hp variants. We combined several state-of-the-art analytical methods, including various forms of chromatography, mass photometry, and different tiers of mass spectrometry, to reveal how the tens to hundreds distinct proteoforms and their assemblies influence Hp’s capacity for Hb binding. We extend the current knowledge by showing that Hb binding does not just depend on the donor’s genotype, but is also affected by variations in Hp oligomerization, glycosylation, and proteolytic processing of the Hp α-chain.
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6
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Gröbner R, Kapferer-Seebacher I, Amberger A, Redolfi R, Dalonneau F, Björck E, Milnes D, Bally I, Rossi V, Thielens N, Stoiber H, Gaboriaud C, Zschocke J. C1R Mutations Trigger Constitutive Complement 1 Activation in Periodontal Ehlers-Danlos Syndrome. Front Immunol 2019; 10:2537. [PMID: 31749804 PMCID: PMC6848165 DOI: 10.3389/fimmu.2019.02537] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Accepted: 10/14/2019] [Indexed: 11/20/2022] Open
Abstract
Heterozygous missense or in-frame insertion/deletion mutations in complement 1 subunits C1r and C1s cause periodontal Ehlers-Danlos Syndrome (pEDS), a specific EDS subtype characterized by early severe periodontal destruction and connective tissue abnormalities like easy bruising, pretibial haemosiderotic plaques, and joint hypermobility. We report extensive functional studies of 16 C1R variants associated with pEDS by in-vitro overexpression studies in HEK293T cells followed by western blot, size exclusion chromatography and surface plasmon resonance analyses. Patient-derived skin fibroblasts were analyzed by western blot and Enzyme-linked Immunosorbent Assay (ELISA). Overexpression of C1R variants in HEK293T cells revealed that none of the pEDS variants was integrated into the C1 complex but cause extracellular presence of catalytic C1r/C1s activities. Variants showed domain-specific abnormalities of intracellular processing and secretion with preservation of serine protease function in the supernatant. In contrast to C1r wild type, and with the exception of a C1R missense variant disabling a C1q binding site, pEDS variants had different impact on the cell: retention of C1r fragments inside the cell, secretion of aggregates, or a new C1r cleavage site. Overexpression of C1R variants in HEK293T as well as western blot analyses of patient fibroblasts showed decreased levels of secreted C1r. Importantly, all available patient fibroblasts exhibited activated C1s and activation of externally added C4 in the supernatant while control cell lines secreted proenzyme C1s and showed no increase in C4 activation. The central elements in the pathogenesis of pEDS seem to be the intracellular activation of C1r and/or C1s, and extracellular presence of activated C1s that independently of microbial triggers can activate the classical complement cascade.
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Affiliation(s)
- Rebekka Gröbner
- Institute for Human Genetics, Medical University Innsbruck, Innsbruck, Austria
| | - Ines Kapferer-Seebacher
- Department for Operative and Restorative Dentistry, Medical University Innsbruck, Innsbruck, Austria
| | - Albert Amberger
- Institute for Human Genetics, Medical University Innsbruck, Innsbruck, Austria
| | - Rita Redolfi
- Institute for Human Genetics, Medical University Innsbruck, Innsbruck, Austria
| | | | - Erik Björck
- Department of Molecular Medicine and Surgery, Karolinska Institute, Stockholm, Sweden.,Department of Clinical Genetics, Karolinska University Hospital, Stockholm, Sweden
| | - Di Milnes
- Genetic Health Queensland, Royal Brisbane and Women's Hospital, Herston, QLD, Australia
| | - Isabelle Bally
- University of Grenoble Alpes, CEA, CNRS, IBS, Grenoble, France
| | - Veronique Rossi
- University of Grenoble Alpes, CEA, CNRS, IBS, Grenoble, France
| | - Nicole Thielens
- University of Grenoble Alpes, CEA, CNRS, IBS, Grenoble, France
| | - Heribert Stoiber
- Institute of Virology, Medical University Innsbruck, Innsbruck, Austria
| | | | - Johannes Zschocke
- Institute for Human Genetics, Medical University Innsbruck, Innsbruck, Austria
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7
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Zhuang Q, Holt BA, Kwong GA, Qiu P. Deconvolving multiplexed protease signatures with substrate reduction and activity clustering. PLoS Comput Biol 2019; 15:e1006909. [PMID: 31479443 PMCID: PMC6743790 DOI: 10.1371/journal.pcbi.1006909] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Revised: 09/13/2019] [Accepted: 07/29/2019] [Indexed: 12/16/2022] Open
Abstract
Proteases are multifunctional, promiscuous enzymes that degrade proteins as well as peptides and drive important processes in health and disease. Current technology has enabled the construction of libraries of peptide substrates that detect protease activity, which provides valuable biological information. An ideal library would be orthogonal, such that each protease only hydrolyzes one unique substrate, however this is impractical due to off-target promiscuity (i.e., one protease targets multiple different substrates). Therefore, when a library of probes is exposed to a cocktail of proteases, each protease activates multiple probes, producing a convoluted signature. Computational methods for parsing these signatures to estimate individual protease activities primarily use an extensive collection of all possible protease-substrate combinations, which require impractical amounts of training data when expanding to search for more candidate substrates. Here we provide a computational method for estimating protease activities efficiently by reducing the number of substrates and clustering proteases with similar cleavage activities into families. We envision that this method will be used to extract meaningful diagnostic information from biological samples. The activity of enzymatic proteins, which are called proteases, drives numerous important processes in health and disease: including cancer, immunity, and infectious disease. Many labs have developed useful diagnostics by designing sensors that measure the activity of these proteases. However, if we want to detect multiple proteases at the same time, it becomes impractical to design sensors that only detect one protease. This is due to a phenomenon called protease promiscuity, which means that proteases will activate multiple different sensors. Computational methods have been created to solve this problem, but the challenge is that these often require large amounts of training data. Further, completely different proteases may be detected by the same subset of sensors. In this work, we design a computational method to overcome this problem by clustering similar proteases into "subfamilies", which increases estimation accuracy. Further, our method tests multiple combinations of sensors to maintain accuracy while minimizing the number of sensors used. Together, we envision that this work will increase the amount of useful information we can extract from biological samples, which may lead to better clinical diagnostics.
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Affiliation(s)
- Qinwei Zhuang
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, United States of America
| | - Brandon Alexander Holt
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Tech College of Engineering and Emory School of Medicine, Atlanta, Georgia, United States of America
| | - Gabriel A. Kwong
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Tech College of Engineering and Emory School of Medicine, Atlanta, Georgia, United States of America
- Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia, United States of America
- Institute for Electronics and Nanotechnology, Georgia Institute of Technology, Atlanta, Georgia, United States of America
- Integrated Cancer Research Center, Georgia Institute of Technology, Atlanta, Georgia, United States of America
- Georgia ImmunoEngineering Consortium, Georgia Tech and Emory University, Atlanta, Georgia, United States of America
- * E-mail: (GAK); (PQ)
| | - Peng Qiu
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Tech College of Engineering and Emory School of Medicine, Atlanta, Georgia, United States of America
- Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia, United States of America
- * E-mail: (GAK); (PQ)
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8
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Ugurlar D, Howes SC, de Kreuk BJ, Koning RI, de Jong RN, Beurskens FJ, Schuurman J, Koster AJ, Sharp TH, Parren PWHI, Gros P. Structures of C1-IgG1 provide insights into how danger pattern recognition activates complement. Science 2018; 359:794-797. [PMID: 29449492 DOI: 10.1126/science.aao4988] [Citation(s) in RCA: 105] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Accepted: 01/10/2018] [Indexed: 01/10/2023]
Abstract
Danger patterns on microbes or damaged host cells bind and activate C1, inducing innate immune responses and clearance through the complement cascade. How these patterns trigger complement initiation remains elusive. Here, we present cryo-electron microscopy analyses of C1 bound to monoclonal antibodies in which we observed heterogeneous structures of single and clustered C1-immunoglobulin G1 (IgG1) hexamer complexes. Distinct C1q binding sites are observed on the two Fc-CH2 domains of each IgG molecule. These are consistent with known interactions and also reveal additional interactions, which are supported by functional IgG1-mutant analysis. Upon antibody binding, the C1q arms condense, inducing rearrangements of the C1r2s2 proteases and tilting C1q's cone-shaped stalk. The data suggest that C1r may activate C1s within single, strained C1 complexes or between neighboring C1 complexes on surfaces.
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Affiliation(s)
- Deniz Ugurlar
- Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, Netherlands
| | - Stuart C Howes
- Section of Electron Microscopy, Department of Molecular Cell Biology, Leiden University Medical Center, Einthovenweg 20, 2300 RC Leiden, Netherlands
| | | | - Roman I Koning
- Section of Electron Microscopy, Department of Molecular Cell Biology, Leiden University Medical Center, Einthovenweg 20, 2300 RC Leiden, Netherlands.,NeCEN, Gorlaeus Laboratories, Leiden University, 2333 CC Leiden, Netherlands
| | | | | | | | - Abraham J Koster
- Section of Electron Microscopy, Department of Molecular Cell Biology, Leiden University Medical Center, Einthovenweg 20, 2300 RC Leiden, Netherlands.,NeCEN, Gorlaeus Laboratories, Leiden University, 2333 CC Leiden, Netherlands
| | - Thomas H Sharp
- Section of Electron Microscopy, Department of Molecular Cell Biology, Leiden University Medical Center, Einthovenweg 20, 2300 RC Leiden, Netherlands.
| | - Paul W H I Parren
- Genmab, Yalelaan 60, 3584 CM Utrecht, Netherlands. .,Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, Netherlands
| | - Piet Gros
- Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, Netherlands.
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9
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Verma S, Mandal A, Ansari MY, Kumar A, Abhishek K, Ghosh AK, Kumar A, Kumar V, Das S, Das P. Leishmania donovani Inhibitor of Serine Peptidases 2 Mediated Inhibition of Lectin Pathway and Upregulation of C5aR Signaling Promote Parasite Survival inside Host. Front Immunol 2018; 9:63. [PMID: 29434593 PMCID: PMC5796892 DOI: 10.3389/fimmu.2018.00063] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2017] [Accepted: 01/10/2018] [Indexed: 11/30/2022] Open
Abstract
Leishmania donovani, the causative agent of Indian visceral leishmaniasis has to face several barriers of the immune system inside the mammalian host for its survival. The complement system is one of the first barriers and consists of a well-balanced network of proteases including S1A family serine proteases (SPs). Inhibitor of serine peptidases (ISPs) is considered as inhibitor of S1A family serine peptidases and is reported to be present in trypanosomes, including Leishmania. In our previous study, we have deciphered the role of ISPs [LdISP1 and L. donovani inhibitor of serine peptidases 2 (LdISP2)] in the survival of L. donovani inside the sandfly midgut. However, the role of theses ISPs in the survival of L. donovani inside mammalian host still remains elusive. In the present study, we have deciphered the inhibitory effect of LdISPs on the host complement S1A serine peptidases, such as C1r/C1s and MASP1/MASP2. Our study suggested that although both rLdISP1 and rLdISP2 inferred strong interaction with C1complex and MBL-associated serine proteases (MASPs) but rLdISP2 showed the stronger inhibitory effect on MASP2 than rLdISP1. Moreover, we found that rLdISP2 significantly reduces the formation of C3, C5 convertase, and membrane attacking complex (MAC) by lectin pathway (LP) resulting in significant reduction in serum mediated lysis of the parasites. The role of LdISP2 on neutrophil elastase-mediated C5aR signaling was also evaluated. Notably, our results showed that infection of macrophages with ISP2-overexpressed Leishmania parasites significantly induces the expression of C5aR both at the transcript and translational level. Simultaneously, infection with ISP2KD parasites results in downregulation of host PI3K/AKT phosphorylation and increased in IL-12 production. Taken together, our findings clearly suggest that LdISP2 promotes parasite survival inside host by inhibiting MAC formation and complement-mediated lysis via LP and by upregulation of C5aR signaling.
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Affiliation(s)
- Sudha Verma
- Department of Molecular Biology, Rajendra Memorial Research Institute of Medical Sciences (ICMR), Patna, India
| | - Abhishek Mandal
- Department of Molecular Biology, Rajendra Memorial Research Institute of Medical Sciences (ICMR), Patna, India
| | - Md Yousuf Ansari
- MM College of Pharmacy, Maharishi Markandeshwar University, Ambala, India
| | - Ajay Kumar
- Department of Molecular Biology, Rajendra Memorial Research Institute of Medical Sciences (ICMR), Patna, India
| | - Kumar Abhishek
- Department of Molecular Biology, Rajendra Memorial Research Institute of Medical Sciences (ICMR), Patna, India
| | - Ayan Kumar Ghosh
- Department of Molecular Biology, Rajendra Memorial Research Institute of Medical Sciences (ICMR), Patna, India
| | - Ashish Kumar
- Department of Molecular Biology, Rajendra Memorial Research Institute of Medical Sciences (ICMR), Patna, India
| | - Vinod Kumar
- Department of Molecular Biology, Rajendra Memorial Research Institute of Medical Sciences (ICMR), Patna, India
| | - Sushmita Das
- Department of Microbiology, All India Institute of Medical Sciences, Patna, India
| | - Pradeep Das
- Department of Molecular Biology, Rajendra Memorial Research Institute of Medical Sciences (ICMR), Patna, India
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10
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Pang SS, Wijeyewickrema LC, Hor L, Tan S, Lameignere E, Conway EM, Blom AM, Mohlin FC, Liu X, Payne RJ, Whisstock JC, Pike RN. The Structural Basis for Complement Inhibition by Gigastasin, a Protease Inhibitor from the Giant Amazon Leech. THE JOURNAL OF IMMUNOLOGY 2017; 199:3883-3891. [PMID: 29061764 DOI: 10.4049/jimmunol.1700158] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Accepted: 09/27/2017] [Indexed: 11/19/2022]
Abstract
Complement is crucial to the immune response, but dysregulation of the system causes inflammatory disease. Complement is activated by three pathways: classical, lectin, and alternative. The classical and lectin pathways are initiated by the C1r/C1s (classical) and MASP-1/MASP-2 (lectin) proteases. Given the role of complement in disease, there is a requirement for inhibitors to control the initiating proteases. In this article, we show that a novel inhibitor, gigastasin, from the giant Amazon leech, potently inhibits C1s and MASP-2, whereas it is also a good inhibitor of MASP-1. Gigastasin is a poor inhibitor of C1r. The inhibitor blocks the active sites of C1s and MASP-2, as well as the anion-binding exosites of the enzymes via sulfotyrosine residues. Complement deposition assays revealed that gigastasin is an effective inhibitor of complement activation in vivo, especially for activation via the lectin pathway. These data suggest that the cumulative effects of inhibiting both MASP-2 and MASP-1 have a greater effect on the lectin pathway than the more potent inhibition of only C1s of the classical pathway.
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Affiliation(s)
- Siew Siew Pang
- Department of Biochemistry and Molecular Biology and Australian Research Council Centre of Excellence in Advanced Molecular Imaging, Biomedicine Discovery Institute, Monash University, Melbourne, Victoria 3800, Australia
| | - Lakshmi C Wijeyewickrema
- Department of Biochemistry and Genetics and Australian Research Council Centre of Excellence in Advanced Molecular Imaging, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia
| | - Lilian Hor
- Department of Biochemistry and Genetics and Australian Research Council Centre of Excellence in Advanced Molecular Imaging, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia
| | - Sheareen Tan
- Department of Biochemistry and Molecular Biology and Australian Research Council Centre of Excellence in Advanced Molecular Imaging, Biomedicine Discovery Institute, Monash University, Melbourne, Victoria 3800, Australia
| | - Emilie Lameignere
- Centre for Blood Research, Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Edward M Conway
- Centre for Blood Research, Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Anna M Blom
- Division of Medical Protein Chemistry, Department of Translational Medicine, Lund University, Malmö SE-221 00, Sweden; and
| | - Frida C Mohlin
- Division of Medical Protein Chemistry, Department of Translational Medicine, Lund University, Malmö SE-221 00, Sweden; and
| | - Xuyu Liu
- School of Chemistry, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Richard J Payne
- School of Chemistry, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - James C Whisstock
- Department of Biochemistry and Molecular Biology and Australian Research Council Centre of Excellence in Advanced Molecular Imaging, Biomedicine Discovery Institute, Monash University, Melbourne, Victoria 3800, Australia;
| | - Robert N Pike
- Department of Biochemistry and Genetics and Australian Research Council Centre of Excellence in Advanced Molecular Imaging, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia;
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11
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Iyer A, Xu W, Reid RC, Fairlie DP. Chemical Approaches to Modulating Complement-Mediated Diseases. J Med Chem 2017; 61:3253-3276. [DOI: 10.1021/acs.jmedchem.7b00882] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Abishek Iyer
- Centre for Inflammation and Disease Research, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia
- ARC Centre of Excellence in Advanced Molecular Imaging, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Weijun Xu
- ARC Centre of Excellence in Advanced Molecular Imaging, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Robert C. Reid
- ARC Centre of Excellence in Advanced Molecular Imaging, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia
| | - David P. Fairlie
- Centre for Inflammation and Disease Research, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia
- ARC Centre of Excellence in Advanced Molecular Imaging, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia
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12
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Andersen CBF, Stødkilde K, Sæderup KL, Kuhlee A, Raunser S, Graversen JH, Moestrup SK. Haptoglobin. Antioxid Redox Signal 2017; 26:814-831. [PMID: 27650279 DOI: 10.1089/ars.2016.6793] [Citation(s) in RCA: 107] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Haptoglobin (Hp) is an abundant human plasma protein that tightly captures hemoglobin (Hb) during hemolysis. The Hb-Hp complex formation reduces the oxidative properties of heme/Hb and promotes recognition by the macrophage scavenger receptor CD163. This leads to Hb-Hp breakdown and heme catabolism by heme oxygenase and biliverdin reductase. Gene duplications of a part of or the entire Hp gene in the primate evolution have led to variant Hp gene products that collectively may be designated "the haptoglobins (Hps)" as they all bind Hb. These variant products include the human-specific multimeric Hp phenotypes in individuals, which are hetero- or homozygous for an Hp2 gene allele. The Hp-related protein (Hpr) is another Hp duplication product in humans and other primates. Alternative functions of the variant Hps are indicated by numerous reports on association between Hp phenotypes and disease as well as the elucidation of a specific role of Hpr in the innate immune defense. Recent Advances: Recent functional and structural information on Hp and receptor systems for Hb removal now provides insight on how Hp carries out essential functions such as the Hb detoxification/removal, and how Hpr, by acting as an Hp-lookalike, can sneak a lethal toxin into trypanosome parasites that cause mammalian sleeping sickness. Critical Issues and Future Directions: The new structural insight may facilitate ongoing attempts of developing Hp derivatives for prevention of Hb toxicity in hemolytic diseases such as sickle cell disease and other hemoglobinopathies. Furthermore, the new structural knowledge may help identifying yet unknown functions based on other disease-relevant biological interactions involving Hps. Antioxid. Redox Signal. 26, 814-831.
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Affiliation(s)
| | | | - Kirstine Lindhardt Sæderup
- 2 Cancer and Inflammation, Department of Molecular Medicine, University of Southern Denmark , Odense C, Denmark
| | - Anne Kuhlee
- 3 Department of Structural Biochemistry, Max-Planck Institute of Molecular Physiology , Dortmund, Germany
| | - Stefan Raunser
- 3 Department of Structural Biochemistry, Max-Planck Institute of Molecular Physiology , Dortmund, Germany
| | - Jonas H Graversen
- 2 Cancer and Inflammation, Department of Molecular Medicine, University of Southern Denmark , Odense C, Denmark
| | - Søren Kragh Moestrup
- 1 Department of Biomedicine, University of Aarhus , Aarhus C, Denmark .,2 Cancer and Inflammation, Department of Molecular Medicine, University of Southern Denmark , Odense C, Denmark .,4 Department of Clinical Biochemistry and Pharmacology, Odense University Hospital , Odense C, Denmark
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13
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Merle NS, Church SE, Fremeaux-Bacchi V, Roumenina LT. Complement System Part I - Molecular Mechanisms of Activation and Regulation. Front Immunol 2015; 6:262. [PMID: 26082779 PMCID: PMC4451739 DOI: 10.3389/fimmu.2015.00262] [Citation(s) in RCA: 960] [Impact Index Per Article: 106.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 05/11/2015] [Indexed: 12/12/2022] Open
Abstract
Complement is a complex innate immune surveillance system, playing a key role in defense against pathogens and in host homeostasis. The complement system is initiated by conformational changes in recognition molecular complexes upon sensing danger signals. The subsequent cascade of enzymatic reactions is tightly regulated to assure that complement is activated only at specific locations requiring defense against pathogens, thus avoiding host tissue damage. Here, we discuss the recent advances describing the molecular and structural basis of activation and regulation of the complement pathways and their implication on physiology and pathology. This article will review the mechanisms of activation of alternative, classical, and lectin pathways, the formation of C3 and C5 convertases, the action of anaphylatoxins, and the membrane-attack-complex. We will also discuss the importance of structure-function relationships using the example of atypical hemolytic uremic syndrome. Lastly, we will discuss the development and benefits of therapies using complement inhibitors.
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Affiliation(s)
- Nicolas S Merle
- UMR_S 1138, Cordeliers Research Center, Complement and Diseases Team, INSERM , Paris , France ; UMR_S 1138, Centre de Recherche des Cordeliers, Sorbonne Paris Cité, Université Paris Descartes , Paris , France ; UMR_S 1138, Centre de Recherche des Cordeliers, Sorbonne Universités, Université Pierre et Marie Curie-Paris , Paris , France
| | - Sarah Elizabeth Church
- UMR_S 1138, Centre de Recherche des Cordeliers, Sorbonne Paris Cité, Université Paris Descartes , Paris , France ; UMR_S 1138, Centre de Recherche des Cordeliers, Sorbonne Universités, Université Pierre et Marie Curie-Paris , Paris , France ; UMR_S 1138, Cordeliers Research Center, Integrative Cancer Immunology Team, INSERM , Paris , France
| | - Veronique Fremeaux-Bacchi
- UMR_S 1138, Cordeliers Research Center, Complement and Diseases Team, INSERM , Paris , France ; UMR_S 1138, Centre de Recherche des Cordeliers, Sorbonne Paris Cité, Université Paris Descartes , Paris , France ; UMR_S 1138, Centre de Recherche des Cordeliers, Sorbonne Universités, Université Pierre et Marie Curie-Paris , Paris , France ; Service d'Immunologie Biologique, Assistance Publique-Hôpitaux de Paris, Hôpital Européen Georges-Pompidou , Paris , France
| | - Lubka T Roumenina
- UMR_S 1138, Cordeliers Research Center, Complement and Diseases Team, INSERM , Paris , France ; UMR_S 1138, Centre de Recherche des Cordeliers, Sorbonne Paris Cité, Université Paris Descartes , Paris , France ; UMR_S 1138, Centre de Recherche des Cordeliers, Sorbonne Universités, Université Pierre et Marie Curie-Paris , Paris , France
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14
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Gaboriaud C, Ling WL, Thielens NM, Bally I, Rossi V. Deciphering the fine details of c1 assembly and activation mechanisms: "mission impossible"? Front Immunol 2014; 5:565. [PMID: 25414705 PMCID: PMC4222235 DOI: 10.3389/fimmu.2014.00565] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Accepted: 10/22/2014] [Indexed: 01/05/2023] Open
Abstract
The classical complement pathway is initiated by the large (~800 kDa) and flexible multimeric C1 complex. Its catalytic function is triggered by the proteases hetero-tetramer C1r2s2, which is associated to the C1q sensing unit, a complex assembly of 18 chains built as a hexamer of heterotrimers. Initial pioneering studies gained insights into the main architectural principles of the C1 complex. A dissection strategy then provided the high-resolution structures of its main functional and/or structural building blocks, as well as structural details on some key protein–protein interactions. These past and current discoveries will be briefly summed up in order to address the question of what is still ill-defined. On a functional point of view, the main molecular determinants of C1 activation and its tight control will be delineated. The current perspective remains to decipher how C1 really works and is controlled in vivo, both in normal and pathological settings.
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Affiliation(s)
- Christine Gaboriaud
- Institut de Biologie Structurale, Université Grenoble Alpes , Grenoble , France ; CNRS, Institut de Biologie Structurale , Grenoble , France ; CEA, Institut de Biologie Structurale , Grenoble , France
| | - Wai Li Ling
- Institut de Biologie Structurale, Université Grenoble Alpes , Grenoble , France ; CNRS, Institut de Biologie Structurale , Grenoble , France ; CEA, Institut de Biologie Structurale , Grenoble , France
| | - Nicole M Thielens
- Institut de Biologie Structurale, Université Grenoble Alpes , Grenoble , France ; CNRS, Institut de Biologie Structurale , Grenoble , France ; CEA, Institut de Biologie Structurale , Grenoble , France
| | - Isabelle Bally
- Institut de Biologie Structurale, Université Grenoble Alpes , Grenoble , France ; CNRS, Institut de Biologie Structurale , Grenoble , France ; CEA, Institut de Biologie Structurale , Grenoble , France
| | - Véronique Rossi
- Institut de Biologie Structurale, Université Grenoble Alpes , Grenoble , France ; CNRS, Institut de Biologie Structurale , Grenoble , France ; CEA, Institut de Biologie Structurale , Grenoble , France
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15
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Pike RN, Wijeyewickrema LC. The molecular switches controlling the interaction between complement proteases of the classical and lectin pathways and their substrates. Curr Opin Struct Biol 2013; 23:820-7. [DOI: 10.1016/j.sbi.2013.07.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Accepted: 07/24/2013] [Indexed: 11/29/2022]
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16
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Kromann-Hansen T, Lund IK, Liu Z, Andreasen PA, Høyer-Hansen G, Sørensen HP. Allosteric inactivation of a trypsin-like serine protease by an antibody binding to the 37- and 70-loops. Biochemistry 2013; 52:7114-26. [PMID: 24079451 DOI: 10.1021/bi400491k] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Serine protease catalytic activity is in many cases regulated by conformational changes initiated by binding of physiological modulators to exosites located distantly from the active site. Inhibitory monoclonal antibodies binding to such exosites are potential therapeutics and offer opportunities for elucidating fundamental allosteric mechanisms. The monoclonal antibody mU1 has previously been shown to be able to inhibit the function of murine urokinase-type plasminogen activator in vivo. We have now mapped the epitope of mU1 to the catalytic domain's 37- and 70-loops, situated about 20 Å from the S1 specificity pocket of the active site. Our data suggest that binding of mU1 destabilizes the catalytic domain and results in conformational transition into a state, in which the N-terminal amino group of Ile16 is less efficiently stabilizing the oxyanion hole and in which the active site has a reduced affinity for substrates and inhibitors. Furthermore, we found evidence for functional interactions between residues in uPA's C-terminal catalytic domain and its N-terminal A-chain, as deletion of the A-chain facilitates the mU1-induced conformational distortion. The inactive, distorted state is by several criteria similar to the E* conformation described for other serine proteases. Hence, agents targeting serine protease conformation through binding to exosites in the 37- and 70-loops represent a new class of potential therapeutics.
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Affiliation(s)
- Tobias Kromann-Hansen
- Danish-Chinese Centre for Proteases and Cancer and ‡Department of Molecular Biology and Genetics, Aarhus University , DK-8000 Aarhus C, Denmark
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17
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The serine protease domain of MASP-3: enzymatic properties and crystal structure in complex with ecotin. PLoS One 2013; 8:e67962. [PMID: 23861840 PMCID: PMC3701661 DOI: 10.1371/journal.pone.0067962] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Accepted: 05/23/2013] [Indexed: 11/19/2022] Open
Abstract
Mannan-binding lectin (MBL), ficolins and collectin-11 are known to associate with three homologous modular proteases, the MBL-Associated Serine Proteases (MASPs). The crystal structures of the catalytic domains of MASP-1 and MASP-2 have been solved, but the structure of the corresponding domain of MASP-3 remains unknown. A link between mutations in the MASP1/3 gene and the rare autosomal recessive 3MC (Mingarelli, Malpuech, Michels and Carnevale,) syndrome, characterized by various developmental disorders, was discovered recently, revealing an unexpected important role of MASP-3 in early developmental processes. To gain a first insight into the enzymatic and structural properties of MASP-3, a recombinant form of its serine protease (SP) domain was produced and characterized. The amidolytic activity of this domain on fluorescent peptidyl-aminomethylcoumarin substrates was shown to be considerably lower than that of other members of the C1r/C1s/MASP family. The E. coli protease inhibitor ecotin bound to the SP domains of MASP-3 and MASP-2, whereas no significant interaction was detected with MASP-1, C1r and C1s. A tetrameric complex comprising an ecotin dimer and two MASP-3 SP domains was isolated and its crystal structure was solved and refined to 3.2 Å. Analysis of the ecotin/MASP-3 interfaces allows a better understanding of the differential reactivity of the C1r/C1s/MASP protease family members towards ecotin, and comparison of the MASP-3 SP domain structure with those of other trypsin-like proteases yields novel hypotheses accounting for its zymogen-like properties in vitro.
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18
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Wijeyewickrema LC, Yongqing T, Tran TP, Thompson PE, Viljoen JE, Coetzer TH, Duncan RC, Kass I, Buckle AM, Pike RN. Molecular determinants of the substrate specificity of the complement-initiating protease, C1r. J Biol Chem 2013; 288:15571-80. [PMID: 23589288 PMCID: PMC3668718 DOI: 10.1074/jbc.m113.451757] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Revised: 03/21/2013] [Indexed: 12/31/2022] Open
Abstract
The serine protease, C1r, initiates activation of the classical pathway of complement, which is a crucial innate defense mechanism against pathogens and altered-self cells. C1r both autoactivates and subsequently cleaves and activates C1s. Because complement is implicated in many inflammatory diseases, an understanding of the interaction between C1r and its target substrates is required for the design of effective inhibitors of complement activation. Examination of the active site specificity of C1r using phage library technology revealed clear specificity for Gln at P2 and Ile at P1', which are found in these positions in physiological substrates of C1r. Removal of one or both of the Gln at P2 and Ile at P1' in the C1s substrate reduced the rate of C1r activation. Substituting a Gln residue into the P2 of the activation site of MASP-3, a protein with similar domain structure to C1s that is not normally cleaved by C1r, enabled efficient activation of this enzyme. Molecular dynamics simulations and structural modeling of the interaction of the C1s activation peptide with the active site of C1r revealed the molecular mechanisms that particularly underpin the specificity of the enzyme for the P2 Gln residue. The complement control protein domains of C1r also made important contributions to efficient activation of C1s by this enzyme, indicating that exosite interactions were also important. These data show that C1r specificity is well suited to its cleavage targets and that efficient cleavage of C1s is achieved through both active site and exosite contributions.
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Affiliation(s)
- Lakshmi C. Wijeyewickrema
- From the Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Tang Yongqing
- From the Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Thuy P. Tran
- From the Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Phillip E. Thompson
- the Monash Institute of Pharmaceutical Sciences, Parkville, Victoria 3052, Australia, and
| | - Jacqueline E. Viljoen
- the Department of Biochemistry, School of Life Sciences, University of KwaZulu-Natal (Pietermaritzburg Campus), Private Bag X01, Scottsville 3209, South Africa
| | - Theresa H. Coetzer
- the Department of Biochemistry, School of Life Sciences, University of KwaZulu-Natal (Pietermaritzburg Campus), Private Bag X01, Scottsville 3209, South Africa
| | - Renee C. Duncan
- From the Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Itamar Kass
- From the Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Ashley M. Buckle
- From the Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Robert N. Pike
- From the Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
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19
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Perry AJ, Wijeyewickrema LC, Wilmann PG, Gunzburg MJ, D'Andrea L, Irving JA, Pang SS, Duncan RC, Wilce JA, Whisstock JC, Pike RN. A molecular switch governs the interaction between the human complement protease C1s and its substrate, complement C4. J Biol Chem 2013; 288:15821-9. [PMID: 23592783 DOI: 10.1074/jbc.m113.464545] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The complement system is an ancient innate immune defense pathway that plays a front line role in eliminating microbial pathogens. Recognition of foreign targets by antibodies drives sequential activation of two serine proteases, C1r and C1s, which reside within the complement Component 1 (C1) complex. Active C1s propagates the immune response through its ability to bind and cleave the effector molecule complement Component 4 (C4). Currently, the precise structural and biochemical basis for the control of the interaction between C1s and C4 is unclear. Here, using surface plasmon resonance, we show that the transition of the C1s zymogen to the active form is essential for C1s binding to C4. To understand this, we determined the crystal structure of a zymogen C1s construct (comprising two complement control protein (CCP) domains and the serine protease (SP) domain). These data reveal that two loops (492-499 and 573-580) in the zymogen serine protease domain adopt a conformation that would be predicted to sterically abrogate C4 binding. The transition from zymogen to active C1s repositions both loops such that they would be able to interact with sulfotyrosine residues on C4. The structure also shows the junction of the CCP1 and CCP2 domains of C1s for the first time, yielding valuable information about the exosite for C4 binding located at this position. Together, these data provide a structural explanation for the control of the interaction with C1s and C4 and, furthermore, point to alternative strategies for developing therapeutic approaches for controlling activation of the complement cascade.
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Affiliation(s)
- Andrew J Perry
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Melbourne, Victoria 3800, Australia
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20
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Sathler PC, Lourenço AL, Miceli LA, Rodrigues CR, Albuquerque MG, Cabral LM, Castro HC. Structural model of haptoglobin and its complex with the anticoagulant ecotin variants: structure-activity relationship study and analysis of interactions. J Enzyme Inhib Med Chem 2013; 29:256-62. [PMID: 23477410 DOI: 10.3109/14756366.2013.774389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Recently the literature described the binding of Haptoglobin (HP) with ecotin, a fold-specific serine-proteases inhibitor with an anticoagulant profile and produced by Escherichia coli. In this work, we used some in silico and in vitro techniques to evaluate HP 3D-fold and its interaction with wild-type ecotin and two variants. Our data showed HP models conserved trypsin fold, in agreement to the in vitro immunological recognition of HP by trypsin antibodies. The analysis of the three ecotin-HP complexes using the mutants RR and TSRR/R besides the wild type revealed several hydrogen bonds between HP and ecotin secondary site. These data are in agreement with the in vitro PAGE assays that showed the HP-RR complex in native gel conditions. Interestingly, the ternary complex interactions varied depending on the inhibitor structure and site-directed mutation. The interaction of HP with TSRR/R involved new residues compared to wild type, which infers a binding energy increase caused by the mutation.
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21
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Pozzi N, Vogt AD, Gohara DW, Di Cera E. Conformational selection in trypsin-like proteases. Curr Opin Struct Biol 2012; 22:421-31. [PMID: 22664096 DOI: 10.1016/j.sbi.2012.05.006] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Revised: 05/08/2012] [Accepted: 05/10/2012] [Indexed: 01/30/2023]
Abstract
For over four decades, two competing mechanisms of ligand recognition--conformational selection and induced-fit--have dominated our interpretation of protein allostery. Defining the mechanism broadens our understanding of the system and impacts our ability to design effective drugs and new therapeutics. Recent kinetics studies demonstrate that trypsin-like proteases exist in equilibrium between two forms: one fully accessible to substrate (E) and the other with the active site occluded (E*). Analysis of the structural database confirms existence of the E* and E forms and vouches for the allosteric nature of the trypsin fold. Allostery in terms of conformational selection establishes an important paradigm in the protease field and enables protein engineers to expand the repertoire of proteases as therapeutics.
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Affiliation(s)
- Nicola Pozzi
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104, United States
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22
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Forneris F, Wu J, Gros P. The modular serine proteases of the complement cascade. Curr Opin Struct Biol 2012; 22:333-41. [PMID: 22560446 DOI: 10.1016/j.sbi.2012.04.001] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2011] [Accepted: 04/05/2012] [Indexed: 11/30/2022]
Abstract
Modular serine proteases are central to the complement cascade of the mammalian humoral immune system. These proteases form protein complexes through multi-domain interactions to achieve their proteolytic activity. We review the structural insights into complement initiation by auto-activation of the hetero-tetrameric proteases of the large danger-recognition protein complexes, amplification and labelling of particles by the formation and activity of C3 convertases, and regulation by convertase dissociation and degradation to prevent 'bystander' damage to healthy host cells and tissues. The data reveal that complex formation and large domain-domain rearrangements underlie the proteolytic reactions of the complement cascade, which enables the host to recognize and clear invading microbes and host debris from its blood and fluids surrounding tissues.
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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, Padualaan 8, 3584 CH Utrecht, The Netherlands
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23
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Allostery in trypsin-like proteases suggests new therapeutic strategies. Trends Biotechnol 2011; 29:577-85. [PMID: 21726912 DOI: 10.1016/j.tibtech.2011.06.001] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2011] [Revised: 05/19/2011] [Accepted: 06/02/2011] [Indexed: 11/21/2022]
Abstract
Trypsin-like proteases (TLPs) are a large family of enzymes responsible for digestion, blood coagulation, fibrinolysis, development, fertilization, apoptosis and immunity. A current paradigm posits that the irreversible transition from an inactive zymogen to the active protease form enables productive interaction with substrate and catalysis. Analysis of the entire structural database reveals two distinct conformations of the active site: one fully accessible to substrate (E) and the other occluded by the collapse of a specific segment (E*). The allosteric E*-E equilibrium provides a reversible mechanism for activity and regulation in addition to the irreversible zymogen to protease conversion and points to new therapeutic strategies aimed at inhibiting or activating the enzyme. In this review, we discuss relevant examples, with emphasis on the rational engineering of anticoagulant thrombin mutants.
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24
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Niu W, Chen Z, Gandhi PS, Vogt AD, Pozzi N, Pelc LA, Zapata F, Di Cera E. Crystallographic and kinetic evidence of allostery in a trypsin-like protease. Biochemistry 2011; 50:6301-7. [PMID: 21707111 DOI: 10.1021/bi200878c] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Protein allostery is based on the existence of multiple conformations in equilibrium linked to distinct functional properties. Although evidence of allosteric transitions is relatively easy to identify by functional studies, structural detection of a pre-existing equilibrium between alternative conformations remains challenging even for textbook examples of allosteric proteins. Kinetic studies show that the trypsin-like protease thrombin exists in equilibrium between two conformations where the active site is either collapsed (E*) or accessible to substrate (E). However, structural demonstration that the two conformations exist in the same enzyme construct free of ligands has remained elusive. Here we report the crystal structure of the thrombin mutant N143P in the E form, which complements the recently reported structure in the E* form, and both the E and E* forms of the thrombin mutant Y225P. The side chain of W215 moves 10.9 Å between the two forms, causing a displacement of 6.6 Å of the entire 215-217 segment into the active site that in turn opens or closes access to the primary specificity pocket. Rapid kinetic measurements of p-aminobenzamidine binding to the active site confirm the existence of the E*-E equilibrium in solution for wild-type and the mutants N143P and Y225P. These findings provide unequivocal proof of the allosteric nature of thrombin and lend strong support to the recent proposal that the E*-E equilibrium is a key property of the trypsin fold.
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Affiliation(s)
- Weiling Niu
- Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, Missouri 63104, USA
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25
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Mannose-binding lectin serine proteases and associated proteins of the lectin pathway of complement: two genes, five proteins and many functions? BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2011; 1824:253-62. [PMID: 21664989 DOI: 10.1016/j.bbapap.2011.05.021] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2011] [Revised: 05/27/2011] [Accepted: 05/27/2011] [Indexed: 10/18/2022]
Abstract
The lectin pathway of the complement system is activated following the binding of carbohydrate-based ligands by recognition molecules such as mannose-binding lectin (MBL) or ficolins. Engagement of the recognition molecules causes activation of associated MBL-associated serine proteases or MASPs, which in turn activate downstream complement molecules to activate the system. Two MASP genes are alternatively spliced during expression to yield 5 proteins, including three proteases (MASP-1, -2 and -3) and two truncated proteins, MAp19 and MAp44. Here we discuss what is currently known about these proteins in terms of their structure and function. MASP-2 is autoactivated following the initial binding events of the pathway and is able to subsequently activate the C4 and C2 substrates required to activate the rest of the pathway. MASP-1 is able to augment MASP-2 activation, but also appears to play other roles, although the physiological significance of these is not yet clear. The roles of the truncated Map19 and Map44 proteins and the MASP-3 protease are currently unknown. The proteases form an interesting sub-family of proteins that clearly should be the focus of future research in order to establish their biological roles. This article is part of a Special Issue entitled: Proteolysis 50 years after the discovery of lysosome.
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Kocsis A, Kékesi KA, Szász R, Végh BM, Balczer J, Dobó J, Závodszky P, Gál P, Pál G. Selective inhibition of the lectin pathway of complement with phage display selected peptides against mannose-binding lectin-associated serine protease (MASP)-1 and -2: significant contribution of MASP-1 to lectin pathway activation. THE JOURNAL OF IMMUNOLOGY 2010; 185:4169-78. [PMID: 20817870 DOI: 10.4049/jimmunol.1001819] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The complement system, an essential part of the innate immune system, can be activated through three distinct routes: the classical, the alternative, and the lectin pathways. The contribution of individual activation pathways to different biological processes can be assessed by using pathway-selective inhibitors. In this paper, we report lectin pathway-specific short peptide inhibitors developed by phage display against mannose-binding lectin-associated serine proteases (MASPs), MASP-1 and MASP-2. On the basis of the selected peptide sequences, two 14-mer peptides, designated as sunflower MASP inhibitor (SFMI)-1 and SFMI-2, were produced and characterized. SFMI-1 inhibits both MASP-1 and MASP-2 with a K(I) of 65 and 1030 nM, respectively, whereas SFMI-2 inhibits only MASP-2 with a K(I) of 180 nM. Both peptides block the lectin pathway activation completely while leaving the classical and the alternative routes intact and fully functional, demonstrating that of all complement proteases only MASP-1 and/or MASP-2 are inhibited by these peptides. In a C4 deposition inhibitor assay using preactivated MASP-2, SFMI-2 is 10-fold more effective than SFMI-1 in accordance with the fact that SFMI-2 is a more potent inhibitor of MASP-2. Surprisingly, however, out of the two peptides, SFMI-1 is much more effective in preventing C3 and C4 deposition when normal human serum containing zymogen MASPs is used. This suggests that MASP-1 has a crucial role in the initiation steps of lectin pathway activation most probably by activating MASP-2. Because the lectin pathway has been implicated in several life-threatening pathological states, these inhibitors should be considered as lead compounds toward developing lectin pathway blocking therapeutics.
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Affiliation(s)
- Andrea Kocsis
- Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, Budapest, Hungary
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Brier S, Pflieger D, Le Mignon M, Bally I, Gaboriaud C, Arlaud GJ, Daniel R. Mapping surface accessibility of the C1r/C1s tetramer by chemical modification and mass spectrometry provides new insights into assembly of the human C1 complex. J Biol Chem 2010; 285:32251-63. [PMID: 20592021 DOI: 10.1074/jbc.m110.149112] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
C1, the complex that triggers the classic pathway of complement, is a 790-kDa assembly resulting from association of a recognition protein C1q with a Ca(2+)-dependent tetramer comprising two copies of the proteases C1r and C1s. Early structural investigations have shown that the extended C1s-C1r-C1r-C1s tetramer folds into a compact conformation in C1. Recent site-directed mutagenesis studies have identified the C1q-binding sites in C1r and C1s and led to a three-dimensional model of the C1 complex (Bally, I., Rossi, V., Lunardi, T., Thielens, N. M., Gaboriaud, C., and Arlaud, G. J. (2009) J. Biol. Chem. 284, 19340-19348). In this study, we have used a mass spectrometry-based strategy involving a label-free semi-quantitative analysis of protein samples to gain new structural insights into C1 assembly. Using a stable chemical modification, we have compared the accessibility of the lysine residues in the isolated tetramer and in C1. The labeling data account for 51 of the 73 lysine residues of C1r and C1s. They strongly support the hypothesis that both C1s CUB(1)-EGF-CUB(2) interaction domains, which are distant in the free tetramer, associate with each other in the C1 complex. This analysis also provides the first experimental evidence that, in the proenzyme form of C1, the C1s serine protease domain is partly positioned inside the C1q cone and yields precise information about its orientation in the complex. These results provide further structural insights into the architecture of the C1 complex, allowing significant improvement of our current C1 model.
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Affiliation(s)
- Sébastien Brier
- CNRS, UMR 8587, Université d'Evry-Val-d'Essonne, Laboratoire Analyse et Modélisation pour la Biologie et l'Environnement, Boulevard François Mitterrand, 91025 Evry, France.
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Major B, Kardos J, Kékesi KA, Lorincz Z, Závodszky P, Gál P. Calcium-dependent conformational flexibility of a CUB domain controls activation of the complement serine protease C1r. J Biol Chem 2010; 285:11863-9. [PMID: 20178990 DOI: 10.1074/jbc.m109.098541] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
C1, the first component of the complement system, is a Ca(2+)-dependent heteropentamer complex of C1q and two modular serine proteases, C1r and C1s. Current functional models assume significant flexibility of the subcomponents. Noncatalytic modules in C1r have been proposed to provide the flexibility required for function. Using a recombinant CUB2-CCP1 domain pair and the individual CCP1 module, we showed that binding of Ca(2+) induces the folding of the CUB2 domain and stabilizes its structure. In the presence of Ca(2+), CUB2 shows a compact, folded structure, whereas in the absence of Ca(2+), it has a flexible, disordered conformation. CCP1 module is Ca(2+)-insensitive. Isothermal titration calorimetry revealed that CUB2 binds a single Ca(2+) with a relatively high K(D) (430 mum). In blood, the CUB2 domain of C1r is only partially (74%) saturated by Ca(2+), therefore the disordered, Ca(2+)-free form could provide the flexibility required for C1 activation. In accordance with this assumption, the effect of Ca(2+) on the autoactivation of native, isolated C1r zymogen was proved. In the case of infection-inflammation when the local Ca(2+) concentration decreases, this property of CUB2 domain could serve as subtle means to trigger the activation of the classical pathway of complement. The CUB2 domain of C1r is a novel example for globular protein domains with marginal stability, high conformational flexibility, and proteolytic sensitivity. The physical nature of the behavior of this domain is similar to that of intrinsically unstructured proteins, providing a further example of functionally relevant ligand-induced reorganization of a polypeptide chain.
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Affiliation(s)
- Balázs Major
- Institute of Enzymology, Hungarian Academy of Sciences, Budapest H-1113, Hungary
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Dobó J, Harmat V, Beinrohr L, Sebestyén E, Závodszky P, Gál P. MASP-1, a promiscuous complement protease: structure of its catalytic region reveals the basis of its broad specificity. THE JOURNAL OF IMMUNOLOGY 2009; 183:1207-14. [PMID: 19564340 DOI: 10.4049/jimmunol.0901141] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Mannose-binding lectin (MBL)-associated serine protease (MASP)-1 is an abundant component of the lectin pathway of complement. The related enzyme, MASP-2 is capable of activating the complement cascade alone. Though the concentration of MASP-1 far exceeds that of MASP-2, only a supporting role of MASP-1 has been identified regarding lectin pathway activation. Several non-complement substrates, like fibrinogen and factor XIII, have also been reported. MASP-1 belongs to the C1r/C1s/MASP family of modular serine proteases; however, its serine protease domain is evolutionary different. We have determined the crystal structure of the catalytic region of active MASP-1 and refined it to 2.55 A resolution. Unusual features of the structure are an internal salt bridge (similar to one in factor D) between the S1 Asp189 and Arg224, and a very long 60-loop. The functional and evolutionary differences between MASP-1 and the other members of the C1r/C1s/MASP family are reflected in the crystal structure. Structural comparison of the protease domains revealed that the substrate binding groove of MASP-1 is wide and resembles that of trypsin rather than early complement proteases explaining its relaxed specificity. Also, MASP-1's multifunctional behavior as both a complement and a coagulation enzyme is in accordance with our observation that antithrombin in the presence of heparin is a more potent inhibitor of MASP-1 than C1 inhibitor. Overall, MASP-1 behaves as a promiscuous protease. The structure shows that its substrate binding groove is accessible; however, its reactivity could be modulated by an unusually large 60-loop and an internal salt bridge involving the S1 Asp.
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Affiliation(s)
- József Dobó
- Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, Budapest, Hungary.
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Gál P, Dobó J, Závodszky P, Sim RBM. Early complement proteases: C1r, C1s and MASPs. A structural insight into activation and functions. Mol Immunol 2009; 46:2745-52. [PMID: 19477526 DOI: 10.1016/j.molimm.2009.04.026] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2009] [Accepted: 04/28/2009] [Indexed: 10/20/2022]
Abstract
C1r, C1s and the mannose-binding lectin-associated serine proteases (MASPs) are responsible for the initiation of the classical- and lectin pathway activation of the complement system. These enzymes do not act alone, but form supramolecular complexes with pattern recognition molecules such as C1q, MBL, and ficolins. They share the same domain organization but have different substrate specificities and fulfill different physiological functions. In the recent years the rapid progress of structural biology facilitated the understanding of the molecular mechanism of complement activation at atomic level. In this review we summarize our current knowledge about the structure and function of the early complement proteases, delineate the latest models of the multimolecular complexes and present the functional consequences inferred from the structural studies. We also discuss some open questions and debated issues that need to be resolved in the future.
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Affiliation(s)
- Péter Gál
- Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, Budapest, Hungary.
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Beinrohr L, Dobó J, Závodszky P, Gál P. C1, MBL-MASPs and C1-inhibitor: novel approaches for targeting complement-mediated inflammation. Trends Mol Med 2008; 14:511-21. [PMID: 18977695 DOI: 10.1016/j.molmed.2008.09.009] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2008] [Revised: 09/26/2008] [Accepted: 09/26/2008] [Indexed: 10/21/2022]
Abstract
Complement activation is initiated by the pattern-recognition molecules complement component C1q, mannose-binding lectin (MBL) and ficolins (H-, L-, M-ficolin), which typically recognize antibody-antigen complexes or foreign polysaccharides. The associated proteases (C1r, C1s, MASP-1 and MASP-2) then activate the complement system. The serpin C1-inhibitor (C1-inh) blocks activity of all these complexes and has been successfully used in models of disease. Many structures of these components became available recently, including that of C1-inh, facilitating the structure-guided design of drugs targeting complement activation. Here, we propose an approach in which therapeutic proteins are made up of natural protein domains and C1-inh to allow targeting to the site of inflammation and more specific inhibition of complement activation. In particular, engineering a fast-acting C1-inh or fusing it to an 'aiming module' has been shown to be feasible and economical using a humanized yeast expression system. Complement-mediated inflammation has been linked to ischemia-reperfusion injury, organ graft rejection and even neurodegeneration, so targeting this process has direct clinical implications.
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Affiliation(s)
- László Beinrohr
- Institute of Enzymology, Karolina út 29, H-1113 Budapest, Hungary.
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Gaultier A, Arandjelovic S, Niessen S, Overton CD, Linton MF, Fazio S, Campana WM, Cravatt BF, Gonias SL. Regulation of tumor necrosis factor receptor-1 and the IKK-NF-kappaB pathway by LDL receptor-related protein explains the antiinflammatory activity of this receptor. Blood 2008; 111:5316-25. [PMID: 18369152 PMCID: PMC2396725 DOI: 10.1182/blood-2007-12-127613] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2007] [Accepted: 03/18/2008] [Indexed: 12/18/2022] Open
Abstract
Low-density lipoprotein receptor-related protein (LRP-1) functions in endocytosis and in cell signaling directly (by binding signaling adaptor proteins) or indirectly (by regulating levels of other cell-surface receptors). Because recent studies in rodents suggest that LRP-1 inhibits inflammation, we conducted activity-based protein profiling experiments to discover novel proteases, involved in inflammation, that are regulated by LRP-1. We found that activated complement proteases accumulate at increased levels when LRP-1 is absent. Although LRP-1 functions as an endocytic receptor for C1r and C1s, complement protease mRNA expression was increased in LRP-1-deficient cells, as was expression of inducible nitric oxide synthase (iNOS) and interleukin-6. Regulation of expression of inflammatory mediators was explained by the ability of LRP-1 to suppress basal cell signaling through the I kappaB kinase-nuclear factor-kappaB (NF-kappaB) pathway. LRP-1-deficient macrophages, isolated from mice, demonstrated increased expression of iNOS, C1r, and monocyte chemoattractant protein-1 (MCP-1); MCP-1 expression was inhibited by NF-kappaB antagonism. The mechanism by which LRP-1 inhibits NF-kappaB activity involves down-regulating cell-surface tumor necrosis factor receptor-1 (TNFR1) and thus, inhibition of autocrine TNFR1-initiated cell signaling. TNF-alpha-neutralizing antibody inhibited NF-kappaB activity selectively in LRP-1-deficient cells. We propose that LRP-1 suppresses expression of inflammatory mediators indirectly, by regulating TNFR1-dependent cell signaling through the I kappaB kinase-NF-kappaB pathway.
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Affiliation(s)
- Alban Gaultier
- Department of Pathology, University of California San Diego School of Medicine, La Jolla, CA 92093-0612, USA
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Revisiting the mechanism of the autoactivation of the complement protease C1r in the C1 complex: structure of the active catalytic region of C1r. Mol Immunol 2007; 45:1752-60. [PMID: 17996945 DOI: 10.1016/j.molimm.2007.09.031] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2007] [Revised: 09/25/2007] [Accepted: 09/27/2007] [Indexed: 11/20/2022]
Abstract
C1r is a modular serine protease which is the autoactivating component of the C1 complex of the classical pathway of the complement system. We have determined the first crystal structure of the entire active catalytic region of human C1r. This fragment contains the C-terminal serine protease (SP) domain and the preceding two complement control protein (CCP) modules. The activated CCP1-CCP2-SP fragment makes up a dimer in a head-to-tail fashion similarly to the previously characterized zymogen. The present structure shows an increased number of stabilizing interactions. Moreover, in the crystal lattice there is an enzyme-product relationship between the C1r molecules of neighboring dimers. This enzyme-product complex exhibits the crucial S1-P1 salt bridge between Asp631 and Arg446 residues, and intermolecular interaction between the CCP2 module and the SP domain. Based on these novel structural information we propose a new split-and-reassembly model for the autoactivation of the C1r. This model is consistent with experimental results that have not been explained adequately by previous models. It allows autoactivation of C1r without large-scale, directed movement of C1q arms. The model is concordant with the stability of the C1 complex during activation of the next complement components.
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Arlaud GJ, Barlow PN, Gaboriaud C, Gros P, Narayana SVL. Deciphering complement mechanisms: the contributions of structural biology. Mol Immunol 2007; 44:3809-22. [PMID: 17768099 DOI: 10.1016/j.molimm.2007.06.147] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2007] [Indexed: 12/25/2022]
Abstract
Since the resolution of the first three-dimensional structure of a complement component in 1980, considerable efforts have been put into the investigation of this system through structural biology techniques, resulting in about a hundred structures deposited in the Protein Data Bank by the beginning of 2007. By revealing its mechanisms at the atomic level, these approaches significantly improve our understanding of complement, opening the way to the rational design of specific inhibitors. This review is co-authored by some of the researchers currently involved in the structural biology of complement and its purpose is to illustrate, through representative examples, how X-ray crystallography and NMR techniques help us decipher the many sophisticated mechanisms that underlie complement functions.
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Affiliation(s)
- Gérard J Arlaud
- Institut de Biologie Structurale Jean-Pierre Ebel, CEA, CNRS, Université Joseph Fourier, 41 rue Jules Horowitz, F-38027 Grenoble, France.
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Kerr FK, Thomas AR, Wijeyewickrema LC, Whisstock JC, Boyd SE, Kaiserman D, Matthews AY, Bird PI, Thielens NM, Rossi V, Pike RN. Elucidation of the substrate specificity of the MASP-2 protease of the lectin complement pathway and identification of the enzyme as a major physiological target of the serpin, C1-inhibitor. Mol Immunol 2007; 45:670-7. [PMID: 17709141 DOI: 10.1016/j.molimm.2007.07.008] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2007] [Revised: 07/09/2007] [Accepted: 07/10/2007] [Indexed: 11/24/2022]
Abstract
Complement is a central component of host defence, but unregulated activation can contribute to disease. The system can be initiated by three pathways: classical, alternative and lectin. The classical and lectin pathways are initiated by the C1 and mannose-binding lectin (MBL) or ficolin complexes, respectively, with C1s the executioner protease of the C1 complex and MASP-2 its counterpart in the lectin complexes. These proteases in turn cleave the C4 and C2 components of the system. Here we have elucidated the cleavage specificity of MASP-2 using a randomised substrate phage display library. Apart from the crucial P1 position, the MASP-2 S2 and S3 subsites (in that order) play the greatest role in determining specificity, with Gly residues preferred at P2 and Leu or hydrophobic residues at P3. Cleavage of peptide substrates representing the known physiological cleavage sequences in C2, C4 or the serpin C1-inhibitor (a likely regulator of MASP-2) revealed that MASP-2 is up to 1000 times more catalytically active than C1s. C1-inhibitor inhibited MASP-2 50-fold faster than C1s and much faster than any other protease tested to date, implying that MASP-2 is a major physiological target of C1-inhibitor.
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Affiliation(s)
- Felicity K Kerr
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
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Duncan RC, Wijeyewickrema LC, Pike RN. The initiating proteases of the complement system: controlling the cleavage. Biochimie 2007; 90:387-95. [PMID: 17850949 DOI: 10.1016/j.biochi.2007.07.023] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2007] [Accepted: 07/24/2007] [Indexed: 11/22/2022]
Abstract
The complement system is a vital component of the host immune system, but when dysregulated, can also cause disease. The system is activated by three pathways: classical, lectin and alternative. The initiating proteases of the classical and lectin pathways have similar domain structure and employ similar mechanisms of activation. The C1r, C1s and MASP-2 proteases have the most defined roles in the activation of the system. This review focuses on the mechanisms whereby their interaction with substrates and inhibitors is regulated.
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Affiliation(s)
- Renee C Duncan
- Department of Biochemistry & Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
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Beinrohr L, Harmat V, Dobó J, Lörincz Z, Gál P, Závodszky P. C1 Inhibitor Serpin Domain Structure Reveals the Likely Mechanism of Heparin Potentiation and Conformational Disease. J Biol Chem 2007; 282:21100-9. [PMID: 17488724 DOI: 10.1074/jbc.m700841200] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
C1 inhibitor, a member of the serpin family, is a major down-regulator of inflammatory processes in blood. Genetic deficiency of C1 inhibitor results in hereditary angioedema, a dominantly inheritable, potentially lethal disease. Here we report the first crystal structure of the serpin domain of human C1 inhibitor, representing a previously unreported latent form, which explains functional consequences of several naturally occurring mutations, two of which are discussed in detail. The presented structure displays a novel conformation with a seven-stranded beta-sheet A. The unique conformation of the C-terminal six residues suggests its potential role as a barrier in the active-latent transition. On the basis of surface charge pattern, heparin affinity measurements, and docking of a heparin disaccharide, a heparin binding site is proposed in the contact area of the serpin-proteinase encounter complex. We show how polyanions change the activity of the C1 inhibitor by a novel "sandwich" mechanism, explaining earlier reaction kinetic and mutagenesis studies. These results may help to improve therapeutic C1 inhibitor preparations used in the treatment of hereditary angioedema, organ transplant rejection, and heart attack.
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Affiliation(s)
- László Beinrohr
- Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, Karolina út 29, H-1113 Budapest, Hungary.
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Gál P, Barna L, Kocsis A, Závodszky P. Serine proteases of the classical and lectin pathways: Similarities and differences. Immunobiology 2007; 212:267-77. [PMID: 17544812 DOI: 10.1016/j.imbio.2006.11.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2006] [Revised: 11/02/2006] [Accepted: 11/07/2006] [Indexed: 11/22/2022]
Abstract
C1r, C1s, MBL-associated serine protease (MASP)-1, MASP-2 and MASP-3 are mosaic serine proteases of the classical and lectin pathways of complement. They form a family of enzymes with identical domain organization and similar overall structure, but with different enzymatic properties. MASP-2 of the lectin pathway can autoactivate and cleave C4 and C2 components. In the classical pathway two enzymes mediate these functions: C1r autoactivates and activates C1s, while C1s cleaves C4 and C2. The substrate specificity and the biological function of MASP-1 and MASP-3 have not yet been completely resolved. MASP-1 can autoactivate and the activated MASP-1 has more relaxed substrate specificity than the other members of the family. It was demonstrated that MASP-1 can specifically cleave C2, C3 and fibrinogen, but the physiological relevance of these findings has to be proved. We do not know how MASP-3 becomes activated and its biological function is also not clear. In this review, we will summarize current knowledge about the structure and function of these proteases. Special emphasis will be laid on the specificity, autoactivation and evolution of these enzymes.
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Affiliation(s)
- Péter Gál
- Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, Karolina u. 29, Budapest H-1113, Hungary.
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Gál P, Harmat V, Kocsis A, Bián T, Barna L, Ambrus G, Végh B, Balczer J, Sim RB, Náray-Szabó G, Závodszky P. A true autoactivating enzyme. Structural insight into mannose-binding lectin-associated serine protease-2 activations. J Biol Chem 2005; 280:33435-44. [PMID: 16040602 DOI: 10.1074/jbc.m506051200] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Few reports have described in detail a true autoactivation process, where no extrinsic cleavage factors are required to initiate the autoactivation of a zymogen. Herein, we provide structural and mechanistic insight into the autoactivation of a multidomain serine protease: mannose-binding lectin-associated serine protease-2 (MASP-2), the first enzymatic component in the lectin pathway of complement activation. We characterized the proenzyme form of a MASP-2 catalytic fragment encompassing its C-terminal three domains and solved its crystal structure at 2.4 A resolution. Surprisingly, zymogen MASP-2 is capable of cleaving its natural substrate C4, with an efficiency about 10% that of active MASP-2. Comparison of the zymogen and active structures of MASP-2 reveals that, in addition to the activation domain, other loops of the serine protease domain undergo significant conformational changes. This additional flexibility could play a key role in the transition of zymogen MASP-2 into a proteolytically active form. Based on the three-dimensional structures of proenzyme and active MASP-2 catalytic fragments, we present model for the active zymogen MASP-2 complex and propose a mechanism for the autoactivation process.
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Affiliation(s)
- Péter Gál
- Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, P.O. Box 7, Budapest H-1518, Hungary
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Harmat V, Gál P, Kardos J, Szilágyi K, Ambrus G, Végh B, Náray-Szabó G, Závodszky P. The Structure of MBL-associated Serine Protease-2 Reveals that Identical Substrate Specificities of C1s and MASP-2 are Realized Through Different Sets of Enzyme–Substrate Interactions. J Mol Biol 2004; 342:1533-46. [PMID: 15364579 DOI: 10.1016/j.jmb.2004.07.014] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2004] [Revised: 07/05/2004] [Accepted: 07/12/2004] [Indexed: 12/01/2022]
Abstract
A family of serine proteases mediates the proteolytic cascades of several defense mechanisms in vertebrates, such as the complement system, blood coagulation and fibrinolysis. These proteases usually form large complexes with other glycoproteins. Their common features are their modular structures and restricted substrate specificities. The lectin pathway of complement, where mannose-binding lectin (MBL) recognizes the carbohydrate structures on pathogens, is activated by mannose-binding lectin-associated serine protease-2 (MASP-2). We present the 2.25A resolution structure of the catalytic fragment of MASP-2 encompassing the second complement control protein module (CCP2) and the serine protease (SP) domain. The CCP2 module stabilizes the structure of the SP domain as demonstrated by differential scanning calorimetry measurements. The asymmetric unit contains two molecules with different CCP-SP domain orientations, reflecting increased modular flexibility at the CCP2/SP joint. This flexibility may partly explain the ability of the MASP-2 dimer to perform all of its functions alone, whereas the same functions are mediated by the much larger C1r2-C1s2 tetramer in the C1 complex of the classical pathway. The main scaffold of the MASP-2 SP domain is chymotrypsin-like. Eight surface loops determine the S1 and other subsite specificities. Surprisingly, some surface loops of MASP-2, e.g. loop 1 and loop 2, which form the S1 pocket are similar to those of trypsin, and show significant differences if compared with those of C1s, indicating that the nearly identical substrate specificities of C1s and MASP-2 are realized through different sets of enzyme-substrate interactions.
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Affiliation(s)
- Veronika Harmat
- Protein Modeling Group, Hungarian Academy of Sciences, Eötvös Loránd University, Pázmány Péter sétány. 1A, H-1117 Budapest, Hungary
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Wicher KB, Fries E. Prohaptoglobin is proteolytically cleaved in the endoplasmic reticulum by the complement C1r-like protein. Proc Natl Acad Sci U S A 2004; 101:14390-5. [PMID: 15385675 PMCID: PMC521962 DOI: 10.1073/pnas.0405692101] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Many secretory proteins are synthesized as proforms that become biologically active through a proteolytic cleavage in the trans-Golgi complex or at a later stage in the secretory pathway. Haptoglobin (Hp) is unusual in that it is cleaved in the endoplasmic reticulum before it enters the Golgi. Here, we present evidence that the recently discovered complement C1r-like protein (C1r-LP) mediates this cleavage. C1r-LP has not previously been shown to possess proteolytic activity, despite its homology to trypsin-like Ser proteinases. We demonstrate that coexpression of the proform of Hp (proHp) and C1r-LP in COS-1 cells effected cleavage of proHp in the endoplasmic reticulum. This cleavage depended on proteolytic activity of C1r-LP because mutation of the putative active-site Ser residue abolished the reaction. Furthermore, incubation of affinity-purified C1r-LP and proHp led to the cleavage of the latter protein. ProHp appeared to be cleaved at the expected site because substitution of Gly for Arg-161 blocked the reaction. C1r-LP showed specificity for proHp, in that it did not cleave the proform of complement C1s, a protein similar to Hp particularly around the cleavage site. C1r-LP accounts for at least part of the endogenous proHp-cleavage activity because suppression of the C1r-LP expression by RNA interference reduced the cleavage of proHp by up to 45% in the cells of a human hepatoma cell line (HepG2).
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Affiliation(s)
- Krzysztof B Wicher
- Department of Medical Biochemistry and Microbiology, Uppsala University, P.O. Box 582, S-751 23 Uppsala, Sweden.
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Gaboriaud C, Thielens NM, Gregory LA, Rossi V, Fontecilla-Camps JC, Arlaud GJ. Structure and activation of the C1 complex of complement: unraveling the puzzle. Trends Immunol 2004; 25:368-73. [PMID: 15207504 DOI: 10.1016/j.it.2004.04.008] [Citation(s) in RCA: 179] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Christine Gaboriaud
- Laboratoire de Cristallographie et Cristallogénèse des Protéines, Institut de Biologie Structurale Jean Pierre Ebel, CEA-CNRS-Université Joseph Fourier, 41, rue Jules Horowitz, 38027 Grenoble Cedex 1, France
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Abstract
Deficiency of C1 Inhibitor leads to unopposed activation of complement, with localized, unpredictable, and sometimes life-threatening attacks of angioedema. Treatment with plasma-derived C1 Inhibitor rapidly aborts attacks, and may be lifesaving, but is expensive, requires use of a pooled blood product, may need to be repeated and may not be effective in autoantibody mediated angioedema. The antifibrinolytic agents aprotinin, tranexamic acid, and epsilon-aminocaproic acid are useful for prophylaxis and treatment of angioedema, likely by inhibiting plasmin. Specific drugs to replace the deficient C1 Inh have not been reported. The kallikrein inhibitor DX-88 (Dyax) has received orphan drug status in Europe and is undergoing clinical trial in Europe and the USA.
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Gregory LA, Thielens NM, Arlaud GJ, Fontecilla-Camps JC, Gaboriaud C. X-ray structure of the Ca2+-binding interaction domain of C1s. Insights into the assembly of the C1 complex of complement. J Biol Chem 2003; 278:32157-64. [PMID: 12788922 DOI: 10.1074/jbc.m305175200] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
C1, the complex that triggers the classical pathway of complement, is assembled from two modular proteases C1r and C1s and a recognition protein C1q. The N-terminal CUB1-EGF segments of C1r and C1s are key elements of the C1 architecture, because they mediate both Ca2+-dependent C1r-C1s association and interaction with C1q. The crystal structure of the interaction domain of C1s has been solved and refined to 1.5 A resolution. The structure reveals a head-to-tail homodimer involving interactions between the CUB1 module of one monomer and the epidermal growth factor (EGF) module of its counterpart. A Ca2+ ion is bound to each EGF module and stabilizes both the intra- and inter-monomer interfaces. Unexpectedly, a second Ca2+ ion is bound to the distal end of each CUB1 module, through six ligands contributed by Glu45, Asp53, Asp98, and two water molecules. These acidic residues and Tyr17 are conserved in approximately two-thirds of the CUB repertoire and define a novel, Ca2+-binding CUB module subset. The C1s structure was used to build a model of the C1r-C1s CUB1-EGF heterodimer, which in C1 connects C1r to C1s and mediates interaction with C1q. A structural model of the C1q/C1r/C1s interface is proposed, where the rod-like collagen triple helix of C1q is accommodated into a groove along the transversal axis of the C1r-C1s heterodimer.
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Affiliation(s)
- Lynn A Gregory
- Laboratoire de Cristallographie et Cristallogénèse des Protéines, Institut de Biologie Structurale Jean-Pierre Ebel, 41 rue Jules Horowitz, 38027 Grenoble Cedex 1, France
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Feinberg H, Uitdehaag JCM, Davies JM, Wallis R, Drickamer K, Weis WI. Crystal structure of the CUB1-EGF-CUB2 region of mannose-binding protein associated serine protease-2. EMBO J 2003; 22:2348-59. [PMID: 12743029 PMCID: PMC155994 DOI: 10.1093/emboj/cdg236] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2003] [Revised: 03/18/2003] [Accepted: 03/19/2003] [Indexed: 11/13/2022] Open
Abstract
Serum mannose-binding proteins (MBPs) are C-type lectins that recognize cell surface carbohydrate structures on pathogens, and trigger killing of these targets by activating the complement pathway. MBPs circulate as a complex with MBP-associated serine proteases (MASPs), which become activated upon engagement of a target cell surface. The minimal functional unit for complement activation is a MASP homodimer bound to two MBP trimeric subunits. MASPs have a modular structure consisting of an N-terminal CUB domain, a Ca(2+)-binding EGF-like domain, a second CUB domain, two complement control protein modules and a C-terminal serine protease domain. The CUB1-EGF-CUB2 region mediates homodimerization and binding to MBP. The crystal structure of the MASP-2 CUB1-EGF-CUB2 dimer reveals an elongated structure with a prominent concave surface that is proposed to be the MBP-binding site. A model of the full six-domain structure and its interaction with MBPs suggests mechanisms by which binding to a target cell transmits conformational changes from MBP to MASP that allow activation of its protease activity.
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Affiliation(s)
- Hadar Feinberg
- Departments of Structural Biology and of Molecular and Cellular Physiology, Stanford University School of Medicine, 299 Campus Drive West, CA 94305-5126, USA
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Arlaud GJ, Gaboriaud C, Thielens NM, Budayova-Spano M, Rossi V, Fontecilla-Camps JC. Structural biology of the C1 complex of complement unveils the mechanisms of its activation and proteolytic activity. Mol Immunol 2002; 39:383-94. [PMID: 12413689 DOI: 10.1016/s0161-5890(02)00143-8] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
C1 is the multimolecular protease that triggers activation of the classical pathway of complement, a major element of antimicrobial host defense also involved in immune tolerance and various pathologies. This 790,000 Da complex is formed from the association of a recognition protein, C1q, and a catalytic subunit, the Ca2+-dependent tetramer C1s-C1r-C1r-C1s comprising two copies of each of the modular proteases C1r and C1s. Early studies mainly based on biochemical analysis and electron microscopy of C1 and its isolated components have allowed for characterization of their domain structure and led to a low-resolution model of the C1 complex in which the elongated C1s-C1r-C1r-C1s tetramer folds into a more compact, "8-shaped" conformation upon interaction with C1q. A major strategy used over the past years has been to dissect the C1 proteins into modular segments to characterize their function and solve their structure by either X-ray crystallography or nuclear magnetic resonance spectroscopy (NMR). The purpose of this review is to focus on this information, with particular emphasis on the architecture of the C1 complex and the mechanisms underlying its activation and proteolytic activity.
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Affiliation(s)
- Gérard J Arlaud
- Laboratoire d'Enzymologie Moleculaire, Institut de Biologie Structurale Jean-Pierre Ebel, CEA-CNRS-Université Joseph Fourier, 41 Rue Jules Horowitz, Avenue des Martyrs, 38027 Grenoble Cedex 1, France.
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