Molecular Mechanisms of Inhibition of Influenza by Surfactant Protein D Revealed by Large-Scale Molecular Dynamics Simulation
Molecular Mechanisms of Inhibition of Influenza by Surfactant Protein D Revealed by Large-Scale Molecular Dynamics Simulation
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DOI：
10.1021/bi4010683
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发表时间：
2013-11-26
期刊：
影响因子：
2.9
通讯作者：
Seaton, Barbara A.
中科院分区：
文献类型：
--
作者：
Goh, Boon Chong;Rynkiewicz, Michael J.;Seaton, Barbara A.
表面活性蛋白D(SP-D)是一种哺乳动物C型凝集素，是甲型流感病毒(IAV)在肺部的主要天然抑制物。SP-D与高度支化的病毒N-糖链上的血凝素(HA)相互作用，通过未知的分子机制促进病毒聚集和中和。血凝素是IAV的一种丰富的囊膜蛋白，也是关键的毒力因子。本研究比较了代表颈部和碳水化合物识别结构域的两种截短的人类SP-D形式，野生型(WT)和双突变体D325A+R343V。而WT和D325A+R343V都与分离的糖基化HA结合，WT在中和试验中不抑制IAV；相反，D325A+R343V的中和效果好于全长天然SP-D。为了阐明这些生化观察的机制，我们测定了D325A+R343V在病毒存在和不存在的情况下的晶体结构(Man9)。根据D325A+R343V-Man9的结构和其他结晶学数据，建立了HA与WT或D325A+R343V的络合物模型，并对其进行了分子动力学研究。模拟结果表明，WT和D325A+R343V都阻断了HA的唾液酸受体部位，而D325A+R343V更稳定，由于额外的氢键和与HA残基的疏水作用导致了更强的结合。此外，HA对WT和D325A+R343V的封闭机制也不同，这是因为不同的多糖结合模式不同。综合结果提示，SP-D HA相互作用模式可显著影响病毒聚集和中和。这些研究提供了第一个关于天然宿主防御凝集素抑制其病毒糖蛋白靶标的原子水平的分子观点。
Surfactant protein D (SP-D), a mammalian C-type lectin, is the primary innate inhibitor of influenza A virus (IAV) in the lung. Interactions of SP-D with highly branched viral N-linked glycans on hemagglutinin (HA), an abundant IAV envelope protein and critical virulence factor, promote viral aggregation and neutralization through as yet unknown molecular mechanisms. Two truncated human SP-D forms, wild-type (WT) and double mutant D325A+R343V, representing neck and carbohydrate recognition domains are compared in this study. Whereas both WT and D325A +R343V bind to isolated glycosylated HA, WT does not inhibit IAV in neutralization assays; in contrast, D325A +R343V neutralization compares well with that of full-length native SP-D. To elucidate the mechanism for these biochemical observations, we have determined crystal structures of D325A +R343V in the presence and absence of a viral nonamannoside (Man9). On the basis of the D325A+R343V - Man9 structure and other crystallographic data, models of complexes between HA and WT or D325A+R343V were produced and subjected to molecular dynamics. Simulations reveal that whereas WT and D325A+R343V both block the sialic acid receptor site of HA, the D325A+R343V complex is more stable, with stronger binding caused by additional hydrogen bonds and hydrophobic interactions with HA residues. Furthermore, the blocking mechanism of HA differs for WT and D325A+R343V because of alternate glycan binding modes. The combined results suggest a mechanism through which the mode of SP-D HA interaction could significantly influence viral aggregation and neutralization. These studies provide the first atomic-level molecular view of an innate host defense lectin inhibiting its viral glycoprotein target.