C3 glomerulopathy–associated CFHR1 mutation alters FHR oligomerization and complement regulation
Agustín Tortajada, Hugo Yébenes, Cynthia Abarrategui-Garrido, Jaouad Anter, Jesús M. García-Fernández, Rubén Martínez-Barricarte, María Alba-Domínguez, Talat H. Malik, Rafael Bedoya, Rocío Cabrera Pérez, Margarita López Trascasa, Matthew C. Pickering, Claire L. Harris, Pilar Sánchez-Corral, Oscar Llorca, Santiago Rodríguez de Córdoba
Agustín Tortajada, Hugo Yébenes, Cynthia Abarrategui-Garrido, Jaouad Anter, Jesús M. García-Fernández, Rubén Martínez-Barricarte, María Alba-Domínguez, Talat H. Malik, Rafael Bedoya, Rocío Cabrera Pérez, Margarita López Trascasa, Matthew C. Pickering, Claire L. Harris, Pilar Sánchez-Corral, Oscar Llorca, Santiago Rodríguez de Córdoba
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Research Article

C3 glomerulopathy–associated CFHR1 mutation alters FHR oligomerization and complement regulation

Abstract

C3 glomerulopathies (C3G) are a group of severe renal diseases with distinct patterns of glomerular inflammation and C3 deposition caused by complement dysregulation. Here we report the identification of a familial C3G-associated genomic mutation in the gene complement factor H–related 1 (CFHR1), which encodes FHR1. The mutation resulted in the duplication of the N-terminal short consensus repeats (SCRs) that are conserved in FHR2 and FHR5. We determined that native FHR1, FHR2, and FHR5 circulate in plasma as homo- and hetero-oligomeric complexes, the formation of which is likely mediated by the conserved N-terminal domain. In mutant FHR1, duplication of the N-terminal domain resulted in the formation of unusually large multimeric FHR complexes that exhibited increased avidity for the FHR1 ligands C3b, iC3b, and C3dg and enhanced competition with complement factor H (FH) in surface plasmon resonance (SPR) studies and hemolytic assays. These data revealed that FHR1, FHR2, and FHR5 organize a combinatorial repertoire of oligomeric complexes and demonstrated that changes in FHR oligomerization influence the regulation of complement activation. In summary, our identification and characterization of a unique CFHR1 mutation provides insights into the biology of the FHRs and contributes to our understanding of the pathogenic mechanisms underlying C3G.

Authors

Agustín Tortajada, Hugo Yébenes, Cynthia Abarrategui-Garrido, Jaouad Anter, Jesús M. García-Fernández, Rubén Martínez-Barricarte, María Alba-Domínguez, Talat H. Malik, Rafael Bedoya, Rocío Cabrera Pérez, Margarita López Trascasa, Matthew C. Pickering, Claire L. Harris, Pilar Sánchez-Corral, Oscar Llorca, Santiago Rodríguez de Córdoba

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Figure 5

Mutant FHR1 protein shows an abnormal heparin chromatography elution profile and assembles into high–molecular weight multimers.

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Mutant FHR1 protein shows an abnormal heparin chromatography elution pro...
(A) Elution profiles of the FHR1, FHR2, and FHR5 proteins from GN29M illustrated that the mutant FHR1 coeluted with FHR2 in a major peak extending through most of the NaCl gradient and a minor peak at low NaCl concentration. Heparin fractions were characterized by Western blot using MBC125. Samples from the elution profiles were run in 3 separate gels. (B) EDTA plasma from GN29M was passed through the MBC125 affinity column. The retained FHRs were eluted in 100 mM glycine, pH 2.5; dialyzed against PBS; and analyzed by size-exclusion Superdex 200 PC 3.2/30 chromatography in 20 mM Tris-HCl (pH 7.5) and 350 mM NaCl (GN29M FHR1-FHR2). Purified proteins corresponding to the FHRs heparin chromatography elution peak 1 from a normal individual (Native FHR1-FHR2; corresponding to FHR1-FHR2 dimers) is also shown for size comparison. Also included is a preparation enriched of the high–molecular size species of the mutant FHR1 protein (Enriched Mut. FHR1). Proteins in the gel filtration fractions were characterized by Western blot and are shown below.