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Massri M, Toonen EJ, Sarg B, Kremser L, Grasse M, Fleischer V, Torres-Quesada O, Hengst L, Skjoedt MO, Bayarri-Olmos R, Rosbjerg A, Garred P, Orth-Höller D, Prohászka Z, Würzner R. Complement C7 and clusterin form a complex in circulation. Front Immunol 2024; 15:1330095. [PMID: 38333209 PMCID: PMC10850381 DOI: 10.3389/fimmu.2024.1330095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Accepted: 01/04/2024] [Indexed: 02/10/2024] Open
Abstract
Introduction The complement system is part of innate immunity and is comprised of an intricate network of proteins that are vital for host defense and host homeostasis. A distinct mechanism by which complement defends against invading pathogens is through the membrane attack complex (MAC), a lytic structure that forms on target surfaces. The MAC is made up of several complement components, and one indispensable component of the MAC is C7. The role of C7 in MAC assembly is well documented, however, inherent characteristics of C7 are yet to be investigated. Methods To shed light on the molecular characteristics of C7, we examined the properties of serum-purified C7 acquired using polyclonal and novel monoclonal antibodies. The properties of serum‑purified C7 were investigated through a series of proteolytic analyses, encompassing Western blot and mass spectrometry. The nature of C7 protein-protein interactions were further examined by a novel enzyme-linked immunosorbent assay (ELISA), as well as size‑exclusion chromatography. Results Protein analyses showcased an association between C7 and clusterin, an inhibitory complement regulator. The distinct association between C7 and clusterin was also demonstrated in serum-purified clusterin. Further assessment revealed that a complex between C7 and clusterin (C7-CLU) was detected. The C7-CLU complex was also identified in healthy serum and plasma donors, highlighting the presence of the complex in circulation. Discussion Clusterin is known to dissociate the MAC structure by binding to polymerized C9, nevertheless, here we show clusterin binding to the native form of a terminal complement protein in vivo. The presented data reveal that C7 exhibits characteristics beyond that of MAC assembly, instigating further investigation of the effector role that the C7-CLU complex plays in the complement cascade.
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Affiliation(s)
- Mariam Massri
- Institute of Hygiene & Medical Microbiology, Medical University of Innsbruck, Innsbruck, Austria
| | | | - Bettina Sarg
- Institute of Medical Biochemsitry, Protein Core Facility, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Leopold Kremser
- Institute of Medical Biochemsitry, Protein Core Facility, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Marco Grasse
- Institute of Hygiene & Medical Microbiology, Medical University of Innsbruck, Innsbruck, Austria
| | - Verena Fleischer
- Institute of Hygiene & Medical Microbiology, Medical University of Innsbruck, Innsbruck, Austria
| | - Omar Torres-Quesada
- Institute of Medical Biochemistry, Medical University of Innsbruck, Biocenter, Innsbruck, Austria
- Tyrolean Cancer Research Institute, Innsbruck, Austria
| | - Ludger Hengst
- Institute of Medical Biochemistry, Medical University of Innsbruck, Biocenter, Innsbruck, Austria
| | - Mikkel-Ole Skjoedt
- Laboratory of Molecular Medicine, Department of Clinical Immunology, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark
- Institute of Immunology & Microbiology , University of Copenhagen, Copenhagen, Denmark
| | - Rafael Bayarri-Olmos
- Laboratory of Molecular Medicine, Department of Clinical Immunology, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark
| | - Anne Rosbjerg
- Laboratory of Molecular Medicine, Department of Clinical Immunology, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark
| | - Peter Garred
- Laboratory of Molecular Medicine, Department of Clinical Immunology, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark
| | - Dorothea Orth-Höller
- Institute of Hygiene & Medical Microbiology, Medical University of Innsbruck, Innsbruck, Austria
- MB-LAB Clinical Microbiology Laboratory, Innsbruck, Austria
| | - Zoltán Prohászka
- Department of Internal Medicine and Hematology, Semmelweis University, Budapest, Hungary
- Research Group for Immunology and Hematology, Semmelweis University-Eötvös Loránd Research Network (Office for Supported Research Groups), Budapest, Hungary
| | - Reinhard Würzner
- Institute of Hygiene & Medical Microbiology, Medical University of Innsbruck, Innsbruck, Austria
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Kellnerová S, Huber S, Massri M, Fleischer V, Losso K, Sarg B, Kremser L, Talasz H, He X, Varrone E, Brigotti M, Ardissino G, Orth-Höller D, Würzner R. Enzymatic Cleavage of Stx2a in the Gut and Identification of Pancreatic Elastase and Trypsin as Possible Main Cleavers. Microorganisms 2023; 11:2487. [PMID: 37894145 PMCID: PMC10609011 DOI: 10.3390/microorganisms11102487] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 09/15/2023] [Accepted: 10/02/2023] [Indexed: 10/29/2023] Open
Abstract
Shiga toxins (Stxs), especially the Stx2a subtype, are the major virulence factors involved in enterohemorrhagic Escherichia coli (EHEC)-associated hemolytic uremic syndrome (eHUS), a life-threatening disease causing acute kidney injury, especially in children. After oral transmission and colonization in the gut, EHEC release Stx. Intracellular cleavage of the Stx A subunit, when followed by reduction, boosts the enzymatic activity that causes damage to targeted cells. This cleavage was assumed to be mostly mediated by furin during Stx intracellular trafficking. To investigate whether this cleavage could occur in the intestine, even prior to entering target cells, Stx2a A subunit structure (intact or cleaved) was characterized after its exposure to specific host factors present in human stool. The molecular weight of Stx2a A subunit/fragments was determined by immunoblotting after electrophoretic separation under reducing conditions. In this study, it was demonstrated that Stx2a is cleaved by certain human stool components. Trypsin and chymotrypsin-like elastase 3B (CELA3B), two serine proteases, were identified as potential candidates that can trigger the extracellular cleavage of Stx2a A subunit directly after its secretion by EHEC in the gut. Whether the observed cleavage indeed translates to natural infections and plays a role in eHUS pathogenesis has yet to be determined. If so, it seems likely that a host's protease profile could affect disease development by changing the toxin's biological features.
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Affiliation(s)
- Sára Kellnerová
- Institute of Hygiene and Medical Microbiology, Medical University of Innsbruck, 6020 Innsbruck, Austria; (S.K.); (S.H.); (M.M.); (V.F.)
| | - Silke Huber
- Institute of Hygiene and Medical Microbiology, Medical University of Innsbruck, 6020 Innsbruck, Austria; (S.K.); (S.H.); (M.M.); (V.F.)
| | - Mariam Massri
- Institute of Hygiene and Medical Microbiology, Medical University of Innsbruck, 6020 Innsbruck, Austria; (S.K.); (S.H.); (M.M.); (V.F.)
| | - Verena Fleischer
- Institute of Hygiene and Medical Microbiology, Medical University of Innsbruck, 6020 Innsbruck, Austria; (S.K.); (S.H.); (M.M.); (V.F.)
| | - Klemens Losso
- Institute of Analytical Chemistry and Radiochemistry, University of Innsbruck, 6020 Innsbruck, Austria;
- Department of Food Technology and Nutrition, MCI|The Entrepreneurial School, 6020 Innsbruck, Austria
| | - Bettina Sarg
- Protein Core Facility, Institute of Medical Biochemistry, Center of Chemistry and Biomedicine, Medical University of Innsbruck, 6020 Innsbruck, Austria; (B.S.); (L.K.); (H.T.)
| | - Leopold Kremser
- Protein Core Facility, Institute of Medical Biochemistry, Center of Chemistry and Biomedicine, Medical University of Innsbruck, 6020 Innsbruck, Austria; (B.S.); (L.K.); (H.T.)
| | - Heribert Talasz
- Protein Core Facility, Institute of Medical Biochemistry, Center of Chemistry and Biomedicine, Medical University of Innsbruck, 6020 Innsbruck, Austria; (B.S.); (L.K.); (H.T.)
| | - Xiaohua He
- Western Regional Research Center, U.S. Department of Agriculture, Agricultural Research Service, Albany, CA 74710, USA;
| | - Elisa Varrone
- Department of Medical and Surgical Sciences, School of Medicine, University of Bologna, 40126 Bologna, Italy; (E.V.); (M.B.)
| | - Maurizio Brigotti
- Department of Medical and Surgical Sciences, School of Medicine, University of Bologna, 40126 Bologna, Italy; (E.V.); (M.B.)
| | - Gianluigi Ardissino
- Center for HUS Prevention, Control and Management at Pediatric Nephrology, Dialysis and Transplant Unit, Fondazione IRCCS Ca’ Granda, Ospedale Maggiore Policlinico, 20122 Milan, Italy;
| | - Dorothea Orth-Höller
- Institute of Hygiene and Medical Microbiology, Medical University of Innsbruck, 6020 Innsbruck, Austria; (S.K.); (S.H.); (M.M.); (V.F.)
- MB-LAB–Clinical Microbiology Laboratory, 6020 Innsbruck, Austria
| | - Reinhard Würzner
- Institute of Hygiene and Medical Microbiology, Medical University of Innsbruck, 6020 Innsbruck, Austria; (S.K.); (S.H.); (M.M.); (V.F.)
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Massri M, Foco L, Würzner R. Comprehensive Update and Revision of Nomenclature on Complement C6 and C7 Variants. J Immunol 2022; 208:2597-2612. [PMID: 35867677 DOI: 10.4049/jimmunol.2200045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Accepted: 04/11/2022] [Indexed: 06/15/2023]
Abstract
Complement genes encompass a wide array of variants, giving rise to numerous protein isoforms that have often been shown to exhibit clinical significance. Given that these variants have been discovered over a span of 50 y, one challenging consequence is the inconsistency in the terminology used to classify them. This issue is prominently evident in the nomenclature used for complement C6 and C7 variants, for which we observed a great discrepancy between previously published works and variants described in current genome browsers. This report discusses the causes for the discrepancies in C6 and C7 nomenclature and seeks to establish a classification system that would unify existing and future variants. The inconsistency in the methods used to annotate amino acids and the modifications pinpointed in the C6 and C7 primers are some of the factors that contribute greatly to the discrepancy in the nomenclature. Several variants that were classified incorrectly are highlighted in this report, and we showcase first-hand how a unified classification system is important to match previous with current genetic information. Ultimately, we hope that the proposed classification system of nomenclature becomes an incentive for studies on complement variants and their physiological and/or pathological effects.
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Affiliation(s)
- Mariam Massri
- Institute of Hygiene and Medical Microbiology, Medical University of Innsbruck, Innsbruck, Austria; and
| | - Luisa Foco
- Institute for Biomedicine (affiliated with the University of Lübeck), Eurac Research, Bolzano, Italy
| | - Reinhard Würzner
- Institute of Hygiene and Medical Microbiology, Medical University of Innsbruck, Innsbruck, Austria; and
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