Functional and structural insight into properdin control of complement alternative pathway amplification
Functional and structural insight into properdin control of complement alternative pathway amplification
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DOI：
10.15252/embj.201696173
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发表时间：
2017-04-13
期刊：
影响因子：
11.4
通讯作者：
Andersen, Gregers R.
中科院分区：
文献类型：
--
作者：
Pedersen, Dennis V.;Roumenina, Lubka;Andersen, Gregers R.
备解素 (FP) 是补体替代途径 (AP) 的重要正调节因子，可稳定 C3 和 C5 转化酶，但其寡聚性质对结构分析提出了挑战。我们在此描述了一种由单点突变引起的新型 FP 缺陷 (E244K)，该缺陷导致 AP 活性水平非常低。重组 FP E244K 是单体，不支持溶菌，并且与 C3 产物的结合较弱。我们将其与从寡聚 FP 中切除的单体单元进行比较，该单体单元在溶菌中也功能失调，但结合 AP 原转化酶、C3 转化酶、C3 产物并部分稳定转化酶。这种 FP-转化酶复合物的晶体结构表明 FP 和 AP 转化酶之间的主要接触是由单个 FP 血小板反应蛋白重复序列和 C3b 中的小区域介导的。小角度 X 射线散射表明 FP E244K 被捕获在紧凑的构象中，防止其寡聚化。我们的研究证明了 FP 寡聚在体内的重要作用，而我们的单体能够提供详细的结构见解，为新型补体调节剂铺平了道路。
Properdin (FP) is an essential positive regulator of the complement alternative pathway (AP) providing stabilization of the C3 and C5 convertases, but its oligomeric nature challenges structural analysis. We describe here a novel FP deficiency (E244K) caused by a single point mutation which results in a very low level of AP activity. Recombinant FP E244K is monomeric, fails to support bacteriolysis, and binds weakly to C3 products. We compare this to a monomeric unit excised from oligomeric FP, which is also dysfunctional in bacteriolysis but binds the AP proconvertase, C3 convertase, C3 products and partially stabilizes the convertase. The crystal structure of such a FP-convertase complex suggests that the major contact between FP and the AP convertase is mediated by a single FP thrombospondin repeat and a small region in C3b. Small angle X-ray scattering indicates that FP E244K is trapped in a compact conformation preventing its oligomerization. Our studies demonstrate an essential role of FP oligomerization in vivo while our monomers enable detailed structural insight paving the way for novel modulators of complement.