Factor H-Related (FHR)-1 and FHR-2 Form Homo- and Heterodimers, while FHR-5 Circulates Only As Homodimer in Human Plasma.
Factor H-Related (FHR)-1 and FHR-2 Form Homo- and Heterodimers, while FHR-5 Circulates Only As Homodimer in Human Plasma.
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DOI：
10.3389/fimmu.2017.01328
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发表时间：
2017
影响因子：
7.3
通讯作者：
Kuijpers TW
中科院分区：
文献类型：
--
作者：
van Beek AE;Pouw RB;Brouwer MC;van Mierlo G;Geissler J;Ooijevaar-de Heer P;de Boer M;van Leeuwen K;Rispens T;Wouters D;Kuijpers TW
补体因子H相关(FHR)蛋白被认为是为了微调补体因子H(FH)在补体系统替代途径中的调节作用。此外，FHR-1、FHR-2和FHR-5被认为是二聚体，这进一步复杂化了准确的分析。由于FHR之间和FH之间高度相似，获得用于血清水平定量和功能分析的特定试剂是具有挑战性的。在这项研究中，我们产生了抗体并开发了检测血清中FHR-1、FHR-2和FHR-5的ELISA。我们使用重组蛋白和血清衍生蛋白来证明人类循环中存在四种二聚体：FHR-1、FHR-2和FHR-5的同源二聚体，以及FHR-1/FHR-2的异源二聚体。未发现含有FHR-5的杂二聚体。在本研究中发现的CFHR1纯合子缺失或CFHR2错义/无义复合杂合性突变的个体中，分别缺少FHR-1和FHR-2的同源和杂合二聚体。通过FRET实验，我们发现重组FHR二聚体能够快速地交换单体。用FHR-1和FHR-2缺乏的血清在体外证实了这一点。在所有FHR二聚体中，FHR-5/5同源二聚体与肝素具有较强的结合亲和力。特异性ELISA结果显示，与FH相比，血清FHR-1/1、FHR-1/2、FHR-2/2和FHR-5/5二聚体水平较低，FH的摩尔过剩程度为FH的10-200倍。总之，FHR-1、FHR-2和FHR-5均为二聚体，FHR-1和FHR-2也形成杂二聚体，并在血浆中迅速平衡。
The complement factor H-related (FHR) proteins are hypothesized to fine-tune the regulatory role of complement factor H (FH) in the alternative pathway of the complement system. Moreover, FHR-1, FHR-2, and FHR-5 have been proposed to be dimers, which further complicates accurate analysis. As FHRs are highly similar among themselves and toward FH, obtaining specific reagents for quantification of serum levels and functional analysis is challenging. In this study, we generated antibodies and developed ELISAs to measure FHR-1, FHR-2, and FHR-5 in serum. We used both recombinant and serum-derived proteins to show that four dimers occur in human circulation: homodimers of FHR-1, FHR-2, and FHR-5, as well as FHR-1/FHR-2 heterodimers. Heterodimers containing FHR-5 were not found. In individuals with homozygous CFHR1 deletions or compound heterozygous CFHR2 missense/nonsense mutations identified in this study, the respective FHR-1 and FHR-2 homo- and heterodimers were absent. Using FRET, we found that recombinant FHR dimers exchange monomers rapidly. This was confirmed ex vivo, using FHR-1- and FHR-2-deficient sera. Of all FHR dimers, FHR-5/5 homodimers demonstrated strong binding affinity toward heparin. Specific ELISAs demonstrated that serum levels of FHR-1/1, FHR-1/2, FHR-2/2, and FHR-5/5 dimers were low compared to FH, which circulates at a 10- to 200-fold molar excess. In summary, FHR-1, FHR-2, and FHR-5 homodimerize, with FHR-1 and FHR-2 forming heterodimers as well, and equilibrate quickly in plasma.
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影响因子：
19.6
作者：
Hakobyan, Svetlana;Tortajada, Agustin;Harris, Claire L.;de Cordoba, Santiago R.;Morgan, Bryan P.
通讯作者：
Morgan, Bryan P.
影响因子：
3.5
作者：
Ansari M;McKeigue PM;Skerka C;Hayward C;Rudan I;Vitart V;Polasek O;Armbrecht AM;Yates JR;Vatavuk Z;Bencic G;Kolcic I;Oostra BA;Van Duijn CM;Campbell S;Stanton CM;Huffman J;Shu X;Khan JC;Shahid H;Harding SP;Bishop PN;Deary IJ;Moore AT;Dhillon B;Rudan P;Zipfel PF;Sim RB;Hastie ND;Campbell H;Wright AF
通讯作者：
Wright AF
影响因子：
3.6
作者：
Monteferrante, G.;Brioschi, S.;Noris, M.
通讯作者：
Noris, M.
影响因子：
19.6
作者：
Medjeral-Thomas NR;Lomax-Browne HJ;Beckwith H;Willicombe M;McLean AG;Brookes P;Pusey CD;Falchi M;Cook HT;Pickering MC
通讯作者：
Pickering MC
影响因子：
20.3
作者：
Heinen, Stefan;Hartmann, Andrea;Skerka, Christine
通讯作者：
Skerka, Christine