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 7

Mutant FHR1 shows increased binding to surface-bound C3b, iC3b, and C3dg.

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Mutant FHR1 shows increased binding to surface-bound C3b, iC3b, and C3dg...
(A) SPR analysis of native (black lines) and mutant (gray lines) FHR1 binding to C3b, iC3b, and C3dg. C3b (150 RU) was amine-coupled to a CM5 Biacore chip and used as a nidus for convertase formation. Further C3b (1,240 RU) was deposited on the chip surface by flowing FB and FD to form C3bBb, followed by C3 as convertase substrate. The surface C3b was converted to iC3b by incubating with FH and FI until the surface no longer supported convertase formation. Conversion to C3dg was achieved by incubating the iC3b surface with soluble CR1 and FI until no further C3c was released. 1:2 serial dilutions from 28 μg/ml native and mutant FHR1 were flowed across the surface for 3 minutes, then allowed to dissociate for 3 minutes prior to regenerating the surface. Avidity effects affecting dissociation of mutant FHR1 are clear. (B) Comparative binding of native and mutant FHR1 and FH to C3b and iC3b. Serial dilutions of native FHR1 (WT; 28 μg/ml), mutant FHR1 (Mut; 28 μg/ml), and FH (bottom; 26 μg/ml) were flowed across the C3b surface (gray lines) as described in A. The surface C3b was converted to iC3b by incubating with FH and FI until the surface no longer supported convertase formation. Native and mutant FHR1 as well as FH were flowed across iC3b (black lines) at identical concentrations as in A. Binding of native or mutant FHR1 was little affected by conversion of C3b to iC3b, whereas binding of FH was almost eliminated.