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Mapping interactions between complement C3 and regulators using mutations in atypical hemolytic uremic syndrome
Journal article   Open access   Peer reviewed

Mapping interactions between complement C3 and regulators using mutations in atypical hemolytic uremic syndrome

Elizabeth C Schramm, Lubka T Roumenina, Tania Rybkine, Sophie Chauvet, Paula Vieira-Martins, Christophe Hue, Tara Maga, Elisabetta Valoti, Valerie Wilson, Sakari Jokiranta, …
Blood, Vol.125(15), pp.2359-2369
04/09/2015
DOI: 10.1182/blood-2014-10-609073
PMCID: PMC4392009
PMID: 25608561
url
https://doi.org/10.1182/blood-2014-10-609073View
Published (Version of record) Open Access

Abstract

The pathogenesis of atypical hemolytic uremic syndrome (aHUS) is strongly linked to dysregulation of the alternative pathway of the complement system. Mutations in complement genes have been identified in about two-thirds of cases, with 5% to 15% being in C3. In this study, 23 aHUS-associated genetic changes in C3 were characterized relative to their interaction with the control proteins factor H (FH), membrane cofactor protein (MCP; CD46), and complement receptor 1 (CR1; CD35). In surface plasmon resonance experiments, 17 mutant recombinant proteins demonstrated a defect in binding to FH and/or MCP, whereas 2 demonstrated reduced binding to CR1. In the majority of cases, decreased binding affinity translated to a decrease in proteolytic inactivation (known as cofactor activity) of C3b via FH and MCP. These results were used to map the putative binding regions of C3b involved in the interaction with MCP and CR1 and interrogated relative to known FH binding sites. Seventy-six percent of patients with C3 mutations had low C3 levels that correlated with disease severity. This study expands our knowledge of the functional consequences of aHUS-associated C3 mutations relative to the interaction of C3 with complement regulatory proteins mediating cofactor activity.
Complement C3 - analysis Complement C3 - metabolism Humans Models, Molecular Male Protein Interaction Maps Atypical Hemolytic Uremic Syndrome - pathology Atypical Hemolytic Uremic Syndrome - metabolism Female Mutation Atypical Hemolytic Uremic Syndrome - genetics Binding Sites Complement C3 - genetics Cohort Studies

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