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Disease-associated N-terminal Complement Factor H Mutations Perturb Cofactor and Decay-accelerating Activities

Pechtl, I. C., Kavanagh, D., Mcintosh, N., Harris, Claire Louise and Barlow, P. N. 2011. Disease-associated N-terminal Complement Factor H Mutations Perturb Cofactor and Decay-accelerating Activities. Journal of Biological Chemistry 286 (13) , pp. 11082-11090. 10.1074/jbc.M110.211839

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Abstract

Many mutations associated with atypical hemolytic uremic syndrome (aHUS) lie within complement control protein modules 19–20 at the C terminus of the complement regulator factor H (FH). This region mediates preferential action of FH on self, as opposed to foreign, membranes and surfaces. Hence, speculation on disease mechanisms has focused on deficiencies in regulation of complement activation on glomerular capillary beds. Here, we investigate the consequences of aHUS-linked mutations (R53H and R78G) within the FH N-terminal complement control protein module that also carries the I62V variation linked to dense-deposit disease and age-related macular degeneration. This module contributes to a four-module C3b-binding site (FH1–4) needed for complement regulation and sufficient for fluid-phase regulatory activity. Recombinant FH1–4V62 and FH1–4I62 bind immobilized C3b with similar affinities (KD = 10–14 μM), whereas FH1–4I62 is slightly more effective than FH1–4V62 as cofactor for factor I-mediated cleavage of C3b. The mutant (R53H)FH1–4V62 binds to C3b with comparable affinity (KD ∼12 μM) yet has decreased cofactor activities both in fluid phase and on surface-bound C3b, and exhibits only weak decay-accelerating activity for C3 convertase (C3bBb). The other mutant, (R78G)FH1–4V62, binds poorly to immobilized C3b (KD >35 μM) and is severely functionally compromised, having decreased cofactor and decay-accelerating activities. Our data support causal links between these mutations and disease; they demonstrate that mutations affecting the N-terminal activities of FH, not just those in the C terminus, can predispose to aHUS. These observations reinforce the notion that deficiency in any one of several FH functional properties can contribute to the pathogenesis of this disease.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Medicine
Systems Immunity Research Institute (SIURI)
Subjects: Q Science > Q Science (General)
R Medicine > RZ Other systems of medicine
Uncontrolled Keywords: Complement; Immunology; Kidney; Mutant; Protein-Protein Interactions; C3 Convertase; Age-related Macular Degeneration; Alternative Pathway; Atypical Hemolytic Uremic Syndrome; Dense Deposit Disease
Publisher: American Society for Biochemistry and Molecular Biology
ISSN: 0021-9258
Last Modified: 04 Jun 2017 03:43
URI: http://orca.cf.ac.uk/id/eprint/25396

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