Mutations in Complement Factor H Impair Alternative Pathway Regulation on Mouse Glomerular Endothelial Cells in Vitro
Publication year
2016Source
Journal of Biological Chemistry, 291, 10, (2016), pp. 4974-81ISSN
Publication type
Article / Letter to editor
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Organization
Nephrology
Biochemistry (UMC)
Journal title
Journal of Biological Chemistry
Volume
vol. 291
Issue
iss. 10
Page start
p. 4974
Page end
p. 81
Subject
Radboudumc 10: Reconstructive and regenerative medicine RIMLS: Radboud Institute for Molecular Life Sciences; Radboudumc 11: Renal disorders RIMLS: Radboud Institute for Molecular Life SciencesAbstract
Complement factor H (FH) inhibits complement activation and interacts with glomerular endothelium via its complement control protein domains 19 and 20, which also recognize heparan sulfate (HS). Abnormalities in FH are associated with the renal diseases atypical hemolytic uremic syndrome and dense deposit disease and the ocular disease age-related macular degeneration. Although FH systemically controls complement activation, clinical phenotypes selectively manifest in kidneys and eyes, suggesting the presence of tissue-specific determinants of disease development. Recent results imply the importance of tissue-specifically expressed, sulfated glycosaminoglycans (GAGs), like HS, in determining FH binding to and activity on host tissues. Therefore, we investigated which GAGs mediate human FH and recombinant human FH complement control proteins domains 19 and 20 (FH19-20) binding to mouse glomerular endothelial cells (mGEnCs) in ELISA. Furthermore, we evaluated the functional defects of FH19-20 mutants during complement activation by measuring C3b deposition on mGEnCs using flow cytometry. FH and FH19-20 bound dose-dependently to mGEnCs and TNF-alpha treatment increased binding of both proteins, whereas heparinase digestion and competition with heparin/HS inhibited binding. Furthermore, 2-O-, and 6-O-, but not N-desulfation of heparin, significantly increased the inhibitory effect on FH19-20 binding to mGEnCs. Compared with wild type FH19-20, atypical hemolytic uremic syndrome-associated mutants were less able to compete with FH in normal human serum during complement activation on mGEnCs, confirming their potential glomerular pathogenicity. In conclusion, our study shows that FH and FH19-20 binding to glomerular endothelial cells is differentially mediated by HS but not other GAGs. Furthermore, we describe a novel, patient serum-independent competition assay for pathogenicity screening of FH19-20 mutants.
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- Academic publications [238441]
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- Faculty of Medical Sciences [90373]
- Open Access publications [97518]
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