Gain-of-Function Mutations R249C and S250C in Complement C2 Protein Increase C3 Deposition in the Presence of C-Reactive Protein

Aleksandra Urban, Daria Kowalska, Grzegorz Stasiłojć, Alicja Kuźniewska, Anna Skrobińska, Emilia Arjona, Eugenia Castellote Alonso, María Ángeles Fenollosa Segarra, Ilse Jongerius, Robbert Spaapen, Simon Satchell, Marcel Thiel, Stanisław Ołdziej, Santiago Rodriguez de Córdoba, Marcin Okrój

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Abstract

The impairment of the alternative complement pathway contributes to rare kidney diseases such as atypical hemolytic uremic syndrome (aHUS) and C3 glomerulopathy (C3G). We recently described an aHUS patient carrying an exceptional gain-of-function (GoF) mutation (S250C) in the classical complement pathway component C2 leading to the formation of hyperactive classical convertases. We now report the identification of the same mutation and another C2 GoF mutation R249C in two other patients with a glomerulopathy of uncertain etiology. Both mutations stabilize the classical C3 convertases by a similar mechanism. The presence of R249C and S250C variants in serum increases complement-dependent cytotoxicity (CDC) in antibody-sensitized human cells and elevates deposition of C3 on ELISA plates coated with C-reactive protein (CRP), as well as on the surface of glomerular endothelial cells. Our data justify the inclusion of classical pathway genes in the genetic analysis of patients suspected of complement-driven renal disorders. Also, we point out CRP as a potential antibody-independent trigger capable of driving excessive complement activation in carriers of the GoF mutations in complement C2.
Original languageEnglish
Article number724361
JournalFrontiers in immunology
Volume12
DOIs
Publication statusPublished - 25 Nov 2021

Keywords

  • C3 glomerulopathy
  • aHUS
  • complement C2
  • complement system
  • endothelial cells

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