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Hauer JJ, Zhang Y, Goodfellow R, Taylor A, Meyer NC, Roberts S, Shao D, Fergus L, Borsa NG, Hall M, Nester CM, Smith RJ. Defining Nephritic Factors as Diverse Drivers of Systemic Complement Dysregulation in C3 Glomerulopathy. Kidney Int Rep 2024; 9:464-477. [PMID: 38344720 PMCID: PMC10851021 DOI: 10.1016/j.ekir.2023.11.025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Revised: 11/22/2023] [Accepted: 11/27/2023] [Indexed: 09/19/2024] Open
Abstract
Introduction C3 glomerulopathy (C3G) is an ultrarare renal disease characterized by deposition of complement component C3 in the glomerular basement membrane (GBM). Rare and novel genetic variation in complement genes and autoantibodies to complement proteins are commonly identified in the C3G population and thought to drive the underlying complement dysregulation that results in renal damage. However, disease heterogeneity and rarity make accurately defining characteristics of the C3G population difficult. Methods Here, we present a retrospective analysis of the Molecular Otolaryngology and Renal Research Laboratories C3G cohort. This study integrated complement biomarker testing and in vitro tests of autoantibody function to achieve the following 3 primary goals: (i) define disease profiles of C3G based on disease drivers, complement biomarkers, and age; (ii) determine the relationship between in vitro autoantibody tests and in vivo complement dysregulation; and (iii) evaluate the association between autoantibody function and disease progression. Results The largest disease profiles of C3G included patients with autoantibodies to complement proteins (48%) and patients for whom no genetic and/or acquired drivers of disease could be identified (43%). The correlation between the stabilization of convertases by complement autoantibodies as measured by in vitro modified hemolytic assays and systemic biomarkers that reflect in vivo complement dysregulation was remarkably strong. In patients positive for autoantibodies, the degree of stabilization capacity predicted worse renal function. Conclusion This study implicates complement autoantibodies as robust drivers of systemic complement dysregulation in approximately 50% of C3G but also highlights the need for continued discovery-based research to identify novel drivers of disease.
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Affiliation(s)
- Jill J. Hauer
- Molecular Otolaryngology and Renal Research Laboratories, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Yuzhou Zhang
- Molecular Otolaryngology and Renal Research Laboratories, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Renee Goodfellow
- Molecular Otolaryngology and Renal Research Laboratories, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Amanda Taylor
- Molecular Otolaryngology and Renal Research Laboratories, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Nicole C. Meyer
- Molecular Otolaryngology and Renal Research Laboratories, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Sarah Roberts
- Molecular Otolaryngology and Renal Research Laboratories, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Dingwu Shao
- Molecular Otolaryngology and Renal Research Laboratories, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Lauren Fergus
- Molecular Otolaryngology and Renal Research Laboratories, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Nicolo Ghiringhelli Borsa
- Molecular Otolaryngology and Renal Research Laboratories, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Monica Hall
- Molecular Otolaryngology and Renal Research Laboratories, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Carla M. Nester
- Molecular Otolaryngology and Renal Research Laboratories, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
- Department of Pediatrics and Internal Medicine, Divisions of Nephrology, University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA
| | - Richard J.H. Smith
- Molecular Otolaryngology and Renal Research Laboratories, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
- Department of Pediatrics and Internal Medicine, Divisions of Nephrology, University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA
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2
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Hourcade DE, Mitchell LM. A Monoclonal Antibody That Provides a Model for C3 Nephritic Factors. Monoclon Antib Immunodiagn Immunother 2023; 42:9-14. [PMID: 36853837 PMCID: PMC9983123 DOI: 10.1089/mab.2022.0028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Accepted: 01/17/2023] [Indexed: 03/01/2023] Open
Abstract
Complement is a major innate defense system that protects the intravascular space from microbial invasion. Complement activation results in the assembly of C3 convertases, serine proteases that cleave complement protein C3, generating bioactive fragments C3a and C3b. The complement response is rapid and robust, largely due to a positive feedback regulatory loop mediated by alternative pathway (AP) C3 convertase. C3 nephritic factors (C3NEFs) are autoantibodies that stabilize AP convertase, resulting in uncontrolled C3 cleavage, which, in principle, can promote critical tissue injury similar to that seen in certain renal conditions. Investigations of C3NEFs are hampered by a challenging issue: each C3NEF is derived from a different donor source, and there is no method to compare one C3NEF to another. We have identified a widely available mouse anti-C3 mAb that, similar to many C3NEFs, can stabilize functional AP convertase in a form resistant to decay acceleration by multiple complement regulators. The antibody requires the presence of properdin to confer convertase stability, and hampers the activity of Salp20, a tic salivary protein that accelerates convertase dissociation by displacing properdin from the convertase complex. This mAb can serve as an urgently needed standard for the investigation of C3NEFs. This study also provides novel insights into the dynamics of AP convertase.
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Affiliation(s)
- Dennis E. Hourcade
- Division of Rheumatology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Lynne M. Mitchell
- Division of Rheumatology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
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3
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Michels MAHM, Volokhina EB, van de Kar NCAJ, van den Heuvel LPJ. Challenges in diagnostic testing of nephritic factors. Front Immunol 2022; 13:1036136. [PMID: 36451820 PMCID: PMC9702996 DOI: 10.3389/fimmu.2022.1036136] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2022] [Accepted: 10/12/2022] [Indexed: 09/27/2023] Open
Abstract
Nephritic factors (NeFs) are autoantibodies promoting the activity of the central enzymes of the complement cascade, an important first line of defense of our innate immune system. NeFs stabilize the complement convertase complexes and prevent their natural and regulator-mediated decay. They are mostly associated with rare complement-mediated kidney disorders, in particular with C3 glomerulopathy and related diseases. Although these autoantibodies were already described more than 50 years ago, measuring NeFs for diagnostic purposes remains difficult, and this also complicates our understanding of their clinical associations. In this review, we address the multifactorial challenges of NeF diagnostics. We describe the diseases NeFs are associated with, the heterogenic mechanisms of action of different NeF types, the different methods available in laboratories used for their detection, and efforts for standardization. Finally, we discuss the importance of proper NeF diagnostics for understanding the clinical impact of these autoantibodies in disease pathophysiology and for considering future complement-directed therapy.
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Affiliation(s)
- Marloes A. H. M. Michels
- Department of Pediatric Nephrology, Amalia Children’s Hospital, Radboud University Medical Center, Nijmegen, Netherlands
| | - Elena B. Volokhina
- Department of Pediatric Nephrology, Amalia Children’s Hospital, Radboud University Medical Center, Nijmegen, Netherlands
- Innatoss Laboratories, Oss, Netherlands
| | - Nicole C. A. J. van de Kar
- Department of Pediatric Nephrology, Amalia Children’s Hospital, Radboud University Medical Center, Nijmegen, Netherlands
| | - Lambertus P.W. J. van den Heuvel
- Department of Pediatric Nephrology, Amalia Children’s Hospital, Radboud University Medical Center, Nijmegen, Netherlands
- Department of Laboratory Medicine, Radboud University Medical Center, Nijmegen, Netherlands
- Department of Pediatrics/Pediatric Nephrology, University Hospitals Leuven, Leuven, Belgium
- Department of Development and Regeneration, University Hospitals Leuven, Leuven, Belgium
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4
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Soliman SA, Stanley S, Vanarsa K, Ismail F, Mok CC, Mohan C. Exploring urine:serum fractional excretion ratios as potential biomarkers for lupus nephritis. Front Immunol 2022; 13:910993. [PMID: 36091001 PMCID: PMC9449537 DOI: 10.3389/fimmu.2022.910993] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Accepted: 08/01/2022] [Indexed: 11/26/2022] Open
Abstract
Objectives The goal of this exploratory study is to determine if urine:serum fractional excretion ratios can outperform the corresponding urinary biomarker proteins in identifying active renal disease in systemic lupus erythematosus (SLE). Methods Thirty-six adult SLE patients and twelve healthy controls were examined for serum and urine levels of 8 protein markers, namely ALCAM, calpastatin, hemopexin, peroxiredoxin 6 (PRDX6), platelet factor 4 (PF4), properdin, TFPI and VCAM-1, by ELISA. Fractional excretion of analyzed biomarkers was calculated after normalizing both the urine and serum biomarker levels against creatinine. A further validation cohort of fifty SLE patients was included to validate the initial findings. Results The FE ratios of all 8 proteins interrogated outperformed conventional disease activity markers such as anti-dsDNA, C3 and C4 in identifying renal disease activity. All but VCAM-1FE were superior to the corresponding urine biomarkers levels in differentiating LN activity, exhibiting positive correlation with renal SLEDAI. ALCAMFE, PF4FE and properdinFE ratios exhibited the highest accuracy (AUC>0.9) in distinguishing active LN from inactive SLE. Four of the FE ratios exhibited perfect sensitivity (calpastatin, PRDX6, PF4 and properdin), while ALCAMFE, PF4FE and properdinFE exhibited the highest specificity values for active LN. In addition, several of these novel biomarkers were associated with higher renal pathology activity indices. In the validation cohort ALCAMFE, PF4FE and properdinFE once again exhibited higher accuracy metrics, surpassing corresponding urine and serum biomarkers levels, with ALCAMFE exhibiting 95% accuracy in distinguishing active LN from inactive SLE. Conclusions With most of the tested proteins, urine:serum fractional excretion ratios outperformed corresponding urine and serum protein measurements in identifying active renal involvement in SLE. Hence, this novel class of biomarkers in SLE ought to be systemically evaluated in larger independent cohorts for their diagnostic utility in LN assessment.
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Affiliation(s)
- Samar A. Soliman
- Department of Rheumatology & Rehabilitation, Faculty of Medicine, Minia University, Minia, Egypt
- Department of Biomedical Engineering, University of Houston, Houston, TX, United States
| | - Samantha Stanley
- Department of Biomedical Engineering, University of Houston, Houston, TX, United States
| | - Kamala Vanarsa
- Department of Biomedical Engineering, University of Houston, Houston, TX, United States
| | - Faten Ismail
- Department of Rheumatology & Rehabilitation, Faculty of Medicine, Minia University, Minia, Egypt
| | - Chi Chiu Mok
- Department of Medicine, Tuen Mun Hospital, Hong Kong, Hong Kong SAR, China
| | - Chandra Mohan
- Department of Biomedical Engineering, University of Houston, Houston, TX, United States
- *Correspondence: Chandra Mohan,
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5
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Cortes C, Desler C, Mazzoli A, Chen JY, Ferreira VP. The role of properdin and Factor H in disease. Adv Immunol 2022; 153:1-90. [PMID: 35469595 DOI: 10.1016/bs.ai.2021.12.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The complement system consists of three pathways (alternative, classical, and lectin) that play a fundamental role in immunity and homeostasis. The multifunctional role of the complement system includes direct lysis of pathogens, tagging pathogens for phagocytosis, promotion of inflammatory responses to control infection, regulation of adaptive cellular immune responses, and removal of apoptotic/dead cells and immune complexes from circulation. A tight regulation of the complement system is essential to avoid unwanted complement-mediated damage to the host. This regulation is ensured by a set of proteins called complement regulatory proteins. Deficiencies or malfunction of these regulatory proteins may lead to pro-thrombotic hematological diseases, renal and ocular diseases, and autoimmune diseases, among others. This review focuses on the importance of two complement regulatory proteins of the alternative pathway, Factor H and properdin, and their role in human diseases with an emphasis on: (a) characterizing the main mechanism of action of Factor H and properdin in regulating the complement system and protecting the host from complement-mediated attack, (b) describing the dysregulation of the alternative pathway as a result of deficiencies, or mutations, in Factor H and properdin, (c) outlining the clinical findings, management and treatment of diseases associated with mutations and deficiencies in Factor H, and (d) defining the unwanted and inadequate functioning of properdin in disease, through a discussion of various experimental research findings utilizing in vitro, mouse and human models.
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Affiliation(s)
- Claudio Cortes
- Department of Foundational Medical Studies, Oakland University William Beaumont School of Medicine, Rochester, MI, United States.
| | - Caroline Desler
- Oakland University William Beaumont School of Medicine, Rochester, MI, United States
| | - Amanda Mazzoli
- Oakland University William Beaumont School of Medicine, Rochester, MI, United States
| | - Jin Y Chen
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States
| | - Viviana P Ferreira
- Department of Medical Microbiology and Immunology, University of Toledo College of Medicine and Life Sciences, Toledo, OH, United States.
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6
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Essen MF, Schlagwein N, den Hoven EM, Gijlswijk‐Janssen DJ, Lubbers R, den Bos RM, den Born J, Ruben JM, Trouw LA, Kooten C. Initial properdin binding contributes to alternative pathway activation at the surface of viable and necrotic cells. Eur J Immunol 2022; 52:597-608. [PMID: 35092629 PMCID: PMC9303752 DOI: 10.1002/eji.202149259] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 12/01/2021] [Accepted: 01/10/2022] [Indexed: 11/16/2022]
Abstract
Properdin, the only known positive regulator of the complement system, stabilizes the C3 convertase, thereby increasing its half‐life. In contrast to most other complement factors, properdin is mainly produced extrahepatically by myeloid cells. Recent data suggest a role for properdin as a pattern recognition molecule. Here, we confirmed previous findings of properdin binding to different necrotic cells including Jurkat T cells. Binding can occur independent of C3, as demonstrated by HAP‐1 C3 KO cells, excluding a role for endogenous C3. In view of the cellular source of properdin, interaction with myeloid cells was examined. Properdin bound to the surface of viable monocyte‐derived pro‐ and anti‐inflammatory macrophages, but not to DCs. Binding was demonstrated for purified properdin as well as fractionated P2, P3, and P4 properdin oligomers. Binding contributed to local complement activation as determined by C3 and C5b‐9 deposition on the cell surfaces and seems a prerequisite for alternative pathway activation. Interaction of properdin with cell surfaces could be inhibited with the tick protein Salp20 and by different polysaccharides, depending on sulfation and chain length. These data identify properdin as a factor interacting with different cell surfaces, being either dead or alive, contributing to the local stimulation of complement activation.
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Affiliation(s)
- Mieke F. Essen
- Div. of Nephrology and Transplant Medicine Dept. of Medicine Leiden University Medical Center Leiden The Netherlands
| | - Nicole Schlagwein
- Div. of Nephrology and Transplant Medicine Dept. of Medicine Leiden University Medical Center Leiden The Netherlands
| | - Elisa M.P. den Hoven
- Div. of Nephrology and Transplant Medicine Dept. of Medicine Leiden University Medical Center Leiden The Netherlands
| | - Daniëlle J. Gijlswijk‐Janssen
- Div. of Nephrology and Transplant Medicine Dept. of Medicine Leiden University Medical Center Leiden The Netherlands
| | - Rosalie Lubbers
- Department of Rheumatology Leiden University Medical Center Leiden The Netherlands
| | - Ramon M. den Bos
- Crystal and Structural Chemistry Bijvoet Center for Biomolecular Research Department of Chemistry Faculty of Science Utrecht University Utrecht The Netherlands
| | - Jacob den Born
- Department of Nephrology University Medical Center Groningen Groningen The Netherlands
| | - Jurjen M. Ruben
- Div. of Nephrology and Transplant Medicine Dept. of Medicine Leiden University Medical Center Leiden The Netherlands
| | - Leendert A. Trouw
- Department of Rheumatology Leiden University Medical Center Leiden The Netherlands
- Department of Immunology Leiden University Medical Center Leiden The Netherlands
| | - Cees Kooten
- Div. of Nephrology and Transplant Medicine Dept. of Medicine Leiden University Medical Center Leiden The Netherlands
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7
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Braunger K, Ahn J, Jore MM, Johnson S, Tang TTL, Pedersen DV, Andersen GR, Lea SM. Structure and function of a family of tick-derived complement inhibitors targeting properdin. Nat Commun 2022; 13:317. [PMID: 35031611 PMCID: PMC8760278 DOI: 10.1038/s41467-021-27920-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Accepted: 12/17/2021] [Indexed: 12/12/2022] Open
Abstract
Activation of the serum-resident complement system begins a cascade that leads to activation of membrane-resident complement receptors on immune cells, thus coordinating serum and cellular immune responses. Whilst many molecules act to control inappropriate activation, Properdin is the only known positive regulator of the human complement system. By stabilising the alternative pathway C3 convertase it promotes complement self-amplification and persistent activation boosting the magnitude of the serum complement response by all triggers. In this work, we identify a family of tick-derived alternative pathway complement inhibitors, hereafter termed CirpA. Functional and structural characterisation reveals that members of the CirpA family directly bind to properdin, inhibiting its ability to promote complement activation, and leading to potent inhibition of the complement response in a species specific manner. We provide a full functional and structural characterisation of a properdin inhibitor, opening avenues for future therapeutic approaches.
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Affiliation(s)
- Katharina Braunger
- Sir William Dunn School of Pathology, University of Oxford, OX1 3RE, Oxford, UK
| | - Jiyoon Ahn
- Sir William Dunn School of Pathology, University of Oxford, OX1 3RE, Oxford, UK
| | - Matthijs M Jore
- Sir William Dunn School of Pathology, University of Oxford, OX1 3RE, Oxford, UK
- Department of Medical Microbiology, Radboud University Medical Centre, Nijmegen, Netherlands
| | - Steven Johnson
- Sir William Dunn School of Pathology, University of Oxford, OX1 3RE, Oxford, UK.
- Center for Structural Biology, Center for Cancer Research, National Cancer Institute, 21702, Frederick, MD, USA.
| | - Terence T L Tang
- Sir William Dunn School of Pathology, University of Oxford, OX1 3RE, Oxford, UK
- MRC Laboratory of Molecular Biology, Cambridge, UK
| | - Dennis V Pedersen
- Department of Molecular Biology and Genetics, Aarhus University, DK-8000, Aarhus, Denmark
| | - Gregers R Andersen
- Department of Molecular Biology and Genetics, Aarhus University, DK-8000, Aarhus, Denmark
| | - Susan M Lea
- Sir William Dunn School of Pathology, University of Oxford, OX1 3RE, Oxford, UK.
- Center for Structural Biology, Center for Cancer Research, National Cancer Institute, 21702, Frederick, MD, USA.
- Central Oxford Structural Molecular Imaging Centre, University of Oxford, OX1 3RE, Oxford, UK.
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8
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Long-term follow-up including extensive complement analysis of a pediatric C3 glomerulopathy cohort. Pediatr Nephrol 2022; 37:601-612. [PMID: 34476601 PMCID: PMC8921070 DOI: 10.1007/s00467-021-05221-6] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 07/06/2021] [Accepted: 07/06/2021] [Indexed: 11/28/2022]
Abstract
BACKGROUND C3 glomerulopathy (C3G) is a rare kidney disorder characterized by predominant glomerular depositions of complement C3. C3G can be subdivided into dense deposit disease (DDD) and C3 glomerulonephritis (C3GN). This study describes the long-term follow-up with extensive complement analysis of 29 Dutch children with C3G. METHODS Twenty-nine C3G patients (19 DDD, 10 C3GN) diagnosed between 1992 and 2014 were included. Clinical and laboratory findings were collected at presentation and during follow-up. Specialized assays were used to detect rare variants in complement genes and measure complement-directed autoantibodies and biomarkers in blood. RESULTS DDD patients presented with lower estimated glomerular filtration rate (eGFR). C3 nephritic factors (C3NeFs) were detected in 20 patients and remained detectable over time despite immunosuppressive treatment. At presentation, low serum C3 levels were detected in 84% of all patients. During follow-up, in about 50% of patients, all of them C3NeF-positive, C3 levels remained low. Linear mixed model analysis showed that C3GN patients had higher soluble C5b-9 (sC5b-9) and lower properdin levels compared to DDD patients. With a median follow-up of 52 months, an overall benign outcome was observed with only six patients with eGFR below 90 ml/min/1.73 m2 at last follow-up. CONCLUSIONS We extensively described clinical and laboratory findings including complement features of an exclusively pediatric C3G cohort. Outcome was relatively benign, persistent low C3 correlated with C3NeF presence, and C3GN was associated with higher sC5b-9 and lower properdin levels. Prospective studies are needed to further elucidate the pathogenic mechanisms underlying C3G and guide personalized medicine with complement therapeutics.
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9
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Michels MAHM, Maas RJF, van der Velden TJAM, van de Kar NCAJ, van den Heuvel LPWJ, Volokhina EB. The Role of Properdin in C5 Convertase Activity and C5b-9 Formation in the Complement Alternative Pathway. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2021; 207:2465-2472. [PMID: 34635587 DOI: 10.4049/jimmunol.2100238] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Accepted: 09/03/2021] [Indexed: 12/30/2022]
Abstract
The complement system is an important part of innate immunity. Complement activation leads to formation of convertase enzymes, switch of their specificity from C3 to C5 cleavage, and generation of lytic membrane attack complexes (C5b-9) on surfaces of pathogens. Most C5 cleavage occurs via the complement alternative pathway (AP). The regulator properdin promotes generation and stabilization of AP convertases. However, its role in C5 activation is not yet understood. In this work, we showed that serum properdin is essential for LPS- and zymosan-induced C5b-9 generation and C5b-9-mediated lysis of rabbit erythrocytes. Furthermore, we demonstrated its essential role in C5 cleavage by AP convertases. To this end, we developed a hemolytic assay in which AP convertases were generated on rabbit erythrocytes by using properdin-depleted serum in the presence of C5 inhibitor (step 1), followed by washing and addition of purified C5-C9 components to allow C5b-9 formation (step 2). In this assay, addition of purified properdin to properdin-depleted serum during convertase formation (step 1) was required to restore C5 cleavage and C5b-9-mediated hemolysis. Importantly, C5 convertase activity was also fully restored when properdin was added together with C5b-9 components (step 2), thus after convertase formation. Moreover, with C3-depleted serum, not capable of forming new convertases but containing properdin, in step 2 of the assay, again full C5b-9 formation was observed and blocked by addition of properdin inhibitor Salp20. Thus, properdin is essential for the convertase specificity switch toward C5, and this function is independent of properdin's role in new convertase formation.
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Affiliation(s)
- Marloes A H M Michels
- Radboud Institute for Molecular Life Sciences, Department of Pediatric Nephrology, Amalia Children's Hospital, Radboud University Medical Center, Nijmegen, the Netherlands;
| | - Rianne J F Maas
- Department of Laboratory Medicine, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Thea J A M van der Velden
- Radboud Institute for Molecular Life Sciences, Department of Pediatric Nephrology, Amalia Children's Hospital, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Nicole C A J van de Kar
- Radboud Institute for Molecular Life Sciences, Department of Pediatric Nephrology, Amalia Children's Hospital, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Lambertus P W J van den Heuvel
- Radboud Institute for Molecular Life Sciences, Department of Pediatric Nephrology, Amalia Children's Hospital, Radboud University Medical Center, Nijmegen, the Netherlands.,Department of Laboratory Medicine, Radboud University Medical Center, Nijmegen, the Netherlands.,Department of Pediatrics/Pediatric Nephrology, University Hospitals Leuven, Leuven, Belgium; and.,Department of Development and Regeneration, University Hospitals Leuven, Leuven, Belgium
| | - Elena B Volokhina
- Radboud Institute for Molecular Life Sciences, Department of Pediatric Nephrology, Amalia Children's Hospital, Radboud University Medical Center, Nijmegen, the Netherlands.,Department of Laboratory Medicine, Radboud University Medical Center, Nijmegen, the Netherlands
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10
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Michels MAHM, van de Kar NCAJ, van Kraaij SAW, Sarlea SA, Gracchi V, Engels FAPT, Dorresteijn EM, van der Deure J, Duineveld C, Wetzels JFM, van den Heuvel LPWJ, Volokhina EB. Different Aspects of Classical Pathway Overactivation in Patients With C3 Glomerulopathy and Immune Complex-Mediated Membranoproliferative Glomerulonephritis. Front Immunol 2021; 12:715704. [PMID: 34456924 PMCID: PMC8386118 DOI: 10.3389/fimmu.2021.715704] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Accepted: 07/20/2021] [Indexed: 11/13/2022] Open
Abstract
The rare and heterogeneous kidney disorder C3 glomerulopathy (C3G) is characterized by dysregulation of the alternative pathway (AP) of the complement system. C3G is often associated with autoantibodies stabilizing the AP C3 convertase named C3 nephritic factors (C3NeF). The role of classical pathway (CP) convertase stabilization in C3G and related diseases such as immune complex-mediated membranoproliferative glomerulonephritis (IC-MPGN) remains largely unknown. Here, we investigated the CP convertase activity in patients with C3G and IC-MPGN. Using a refined two-step hemolytic assay, we measured the stability of CP convertases directly in the serum of 52 patients and 17 healthy controls. In four patients, CP convertase activity was prolonged compared to healthy controls, i.e. the enzymatic complex was stabilized. In three patients (2 C3G, 1 IC-MPGN) the convertase stabilization was caused by immunoglobulins, indicating the presence of autoantibodies named C4 nephritic factors (C4NeFs). Importantly, the assay also enabled detection of non-immunoglobulin-mediated stabilization of the CP convertase in one patient with C3G. Prolonged CP convertase activity coincided with C3NeF activity in all patients and for up to 70 months of observation. Crucially, experiments with C3-depleted serum showed that C4NeFs stabilized the CP C3 convertase (C4bC2a), that does not contain C3NeF epitopes. All patients with prolonged CP convertase activity showed clear signs of complement activation, i.e. lowered C3 and C5 levels and elevated levels of C3d, C3bc, C3bBbP, and C5b-9. In conclusion, this work provides new insights into the diverse aspects and (non-)immunoglobulin nature of factors causing CP convertase overactivity in C3G/IC-MPGN.
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Affiliation(s)
- Marloes A H M Michels
- Department of Pediatric Nephrology, Radboud Institute for Molecular Life Sciences, Amalia Children's Hospital, Radboud University Medical Center, Nijmegen, Netherlands
| | - Nicole C A J van de Kar
- Department of Pediatric Nephrology, Radboud Institute for Molecular Life Sciences, Amalia Children's Hospital, Radboud University Medical Center, Nijmegen, Netherlands
| | - Sanne A W van Kraaij
- Department of Laboratory Medicine, Radboud University Medical Center, Nijmegen, Netherlands
| | - Sebastian A Sarlea
- Department of Pediatric Nephrology, Radboud Institute for Molecular Life Sciences, Amalia Children's Hospital, Radboud University Medical Center, Nijmegen, Netherlands
| | - Valentina Gracchi
- Department of Pediatric Nephrology, Beatrix Children's Hospital, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
| | - Flore A P T Engels
- Department of Pediatric Nephrology, Maastricht University Medical Center+, Maastricht, Netherlands
| | - Eiske M Dorresteijn
- Department of Pediatric Nephrology, Sophia Children's Hospital, Erasmus Medical Center, Rotterdam, Netherlands
| | | | - Caroline Duineveld
- Department of Nephrology, Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, Netherlands
| | - Jack F M Wetzels
- Department of Nephrology, Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, Netherlands
| | - Lambertus P W J van den Heuvel
- Department of Pediatric Nephrology, Radboud Institute for Molecular Life Sciences, Amalia Children's Hospital, Radboud University Medical Center, Nijmegen, Netherlands.,Department of Laboratory Medicine, Radboud University Medical Center, Nijmegen, Netherlands.,Department of Pediatrics/Pediatric Nephrology, University Hospitals Leuven, Leuven, Belgium.,Department of Development and Regeneration, University Hospitals Leuven, Leuven, Belgium
| | - Elena B Volokhina
- Department of Pediatric Nephrology, Radboud Institute for Molecular Life Sciences, Amalia Children's Hospital, Radboud University Medical Center, Nijmegen, Netherlands.,Department of Laboratory Medicine, Radboud University Medical Center, Nijmegen, Netherlands
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Lammerts RGM, Talsma DT, Dam WA, Daha MR, Seelen MAJ, Berger SP, van den Born J. Properdin Pattern Recognition on Proximal Tubular Cells Is Heparan Sulfate/Syndecan-1 but Not C3b Dependent and Can Be Blocked by Tick Protein Salp20. Front Immunol 2020; 11:1643. [PMID: 32849563 PMCID: PMC7426487 DOI: 10.3389/fimmu.2020.01643] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Accepted: 06/19/2020] [Indexed: 11/13/2022] Open
Abstract
Introduction: Proteinuria contributes to progression of renal damage, partly by complement activation on proximal tubular epithelial cells. By pattern recognition, properdin has shown to bind to heparan sulfate proteoglycans on tubular epithelium and can initiate the alternative complement pathway (AP). Properdin however, also binds to C3b(Bb) and properdin binding to tubular cells might be influenced by the presence of C3b(Bb) on tubular cells and/or by variability in properdin proteins in vitro. In this study we carefully evaluated the specificity of the properdin – heparan sulfate interaction and whether this interaction could be exploited in order to block alternative complement activation. Methods: Binding of various properdin preparations to proximal tubular epithelial cells (PTEC) and subsequent AP activation was determined in the presence or absence of C3 inhibitor Compstatin and properdin inhibitor Salp20. Heparan sulfate proteoglycan dependency of the pattern recognition of properdin was evaluated on PTEC knocked down for syndecan-1 by shRNA technology. Solid phase binding assays were used to evaluate the effectivity of heparin(oids) and recombinant Salp20 to block the pattern recognition of properdin. Results: Binding of serum-derived and recombinant properdin preparations to PTECs could be dose-dependently inhibited (P < 0.01) and competed off (P < 0.01) by recombinant Salp20 (IC50: ~125 ng/ml) but not by Compstatin. Subsequent properdin-mediated AP activation on PTECs could be inhibited by Compstatin (P < 0.01) and blocked by recombinant Salp20 (P < 0.05). Syndecan-1 deficiency in PTECs resulted in a ~75% reduction of properdin binding (P = 0.057). In solid-phase binding assays, properdin binding to C3b could be dose-dependently inhibited by recombinant Salp20> heparin(oid) > C3b. Discussion: In this study we showed that all properdin preparations recognize heparan sulfate/syndecan-1 on PTECs with and without Compstatin C3 blocking conditions. In contrast to Compstatin, recombinant Salp20 prevents heparan sulfate pattern recognition by properdin on PTECs. Both complement inhibitors prevented properdin-mediated C3 activation. Binding of properdin to C3b could also be blocked by heparin(oids) and recombinant Salp20. This work indicates that properdin serves as a docking station for AP activation on PTECs and a Salp20 analog or heparinoids may be viable inhibitors in properdin mediated AP activation.
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Affiliation(s)
- Rosa G M Lammerts
- Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
| | - Ditmer T Talsma
- Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
| | - Wendy A Dam
- Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
| | - Mohamed R Daha
- Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
| | - Marc A J Seelen
- Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
| | - Stefan P Berger
- Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
| | - Jacob van den Born
- Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
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van den Bos RM, Pearce NM, Granneman J, Brondijk THC, Gros P. Insights Into Enhanced Complement Activation by Structures of Properdin and Its Complex With the C-Terminal Domain of C3b. Front Immunol 2019; 10:2097. [PMID: 31552043 PMCID: PMC6736995 DOI: 10.3389/fimmu.2019.02097] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Accepted: 08/20/2019] [Indexed: 11/13/2022] Open
Abstract
Properdin enhances complement-mediated opsonization of targeted cells and particles for immune clearance. Properdin occurs as dimers, trimers and tetramers in human plasma, which recognize C3b-deposited surfaces, promote formation, and prolong the lifetime of C3bBb-enzyme complexes that convert C3 into C3b, thereby enhancing the complement-amplification loop. Here, we report crystal structures of monomerized properdin, which was produced by co-expression of separate N- and C-terminal constructs that yielded monomer-sized properdin complexes that stabilized C3bBb. Consistent with previous low-resolution X-ray and EM data, the crystal structures revealed ring-shaped arrangements that are formed by interactions between thrombospondin type-I repeat (TSR) domains 4 and 6 of one protomer interacting with the N-terminal domain (which adopts a short transforming-growth factor B binding protein-like fold) and domain TSR1 of a second protomer, respectively. Next, a structure of monomerized properdin in complex with the C-terminal domain of C3b showed that properdin-domain TSR5 binds along the C-terminal α-helix of C3b, while two loops, one from domain TSR5 and one from TSR6, extend and fold around the C3b C-terminus like stirrups. This suggests a mechanistic model in which these TSR5 and TSR6 "stirrups" bridge interactions between C3b and factor B or its fragment Bb, and thereby enhance formation of C3bB pro-convertases and stabilize C3bBb convertases. In addition, properdin TSR6 would sterically block binding of the protease factor I to C3b, thus limiting C3b proteolytic degradation. The presence of a valine instead of a third tryptophan in the canonical Trp-ladder of TSR domains in TSR4 allows a remarkable ca. 60°-domain bending motion of TSR4. Together with variable positioning of TSR2 and, putatively, TSR3, this explains the conformational flexibility required for properdin to form dimers, trimers, and tetramers. In conclusion, the results indicate that binding avidity of oligomeric properdin is needed to distinguish surface-deposited C3b molecules from soluble C3b or C3 and suggest that properdin-mediated interactions bridging C3b-B and C3b-Bb enhance affinity, thus promoting convertase formation and stabilization. These mechanisms explain the enhancement of complement-mediated opsonization of targeted cells and particle for immune clearance.
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Affiliation(s)
- Ramon M van den Bos
- Crystal and Structural Chemistry, Department of Chemistry, Faculty of Science, Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, Netherlands
| | - Nicholas M Pearce
- Crystal and Structural Chemistry, Department of Chemistry, Faculty of Science, Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, Netherlands
| | - Joke Granneman
- Crystal and Structural Chemistry, Department of Chemistry, Faculty of Science, Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, Netherlands
| | - T Harma C Brondijk
- Crystal and Structural Chemistry, Department of Chemistry, Faculty of Science, Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, Netherlands
| | - Piet Gros
- Crystal and Structural Chemistry, Department of Chemistry, Faculty of Science, Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, Netherlands
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