Disease-associated N-terminal complement factor H mutations perturb cofactor and decay-accelerating activities.
Disease-associated N-terminal complement factor H mutations perturb cofactor and decay-accelerating activities.
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DOI：
10.1074/jbc.m110.211839
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发表时间：
2011-04-01
期刊：
影响因子：
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通讯作者：
Barlow PN
中科院分区：
文献类型：
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作者：
Pechtl IC;Kavanagh D;McIntosh N;Harris CL;Barlow PN
与非典型溶血性尿毒综合征（阿胡斯）相关的许多突变位于补体调节因子H（FH）的C末端的补体控制蛋白模块19-20内。该区域介导FH对自身的优先作用，而不是外来的膜和表面。因此，对疾病机制的推测集中在对肾小球毛细血管床补体激活调节的缺陷上。在这里，我们研究了FH N-末端补体控制蛋白模块内aHUS连锁突变（R53 H和R78 G）的后果，该模块还携带与致密沉积物疾病和年龄相关性黄斑变性相关的I62 V变异。该模块有助于补体调节所需的四模块C3 b结合位点（FH 1 -4），并足以进行液相调节活性。重组FH 1 - 4V 62和FH 1 - 4 I62以相似的亲和力（KD = 10- 1 - 4 μm）结合固定的C3 b，而FH 1 - 4 I62作为因子I介导的C3 b切割的辅因子比FH 1 - 4V 62稍微更有效。突变体（R53 H）FH 1 - 4V 62与C3 b的结合亲和力相当（KD <12 μm），但在液相和表面结合的C3 b上的辅因子活性均降低，并且仅表现出对C3转化酶（C3 bBb）的弱衰变加速活性。另一个突变体（R78 G）FH 1 - 4V 62与固定化C3 b的结合较差（KD >35 μm），功能严重受损，辅因子和衰变加速活性降低。我们的数据支持这些突变和疾病之间的因果关系;它们表明，影响FH的N-末端活性的突变，而不仅仅是C末端的突变，可能易患阿胡斯。这些观察结果加强了以下概念，即几种FH功能特性中的任何一种的缺陷都可能导致这种疾病的发病机制。
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.