Coagulation Factor Binding Orientation and Dimerization May Influence Infectivity of Adenovirus-Coagulation Factor Complexes
Coagulation Factor Binding Orientation and Dimerization May Influence Infectivity of Adenovirus-Coagulation Factor Complexes
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DOI：
10.1128/jvi.01070-13
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发表时间：
2013-09-01
影响因子：
5.4
通讯作者：
Shayakhmetov, Dmitry M.
中科院分区：
文献类型：
--
作者：
Irons, Eric E.;Flatt, Justin W.;Shayakhmetov, Dmitry M.
腺病毒（Ads）是用于人类治疗干预的有前景的载体。当注射到血流中时，Ad载体可以结合几种维生素K依赖性凝血因子，这有助于通过促进肝细胞的转导而将病毒隔离在肝脏中。虽然凝血因子FVII和FX都以非常高的亲和力结合人Ad血清型5（HAdv 5）的六邻体蛋白，但似乎只有FX在体内介导Ad-肝细胞转导中起作用。为了理解FVII与六邻体结合的功效与其支持病毒细胞进入的明显差的能力之间的差异，我们通过使用高分辨率冷冻电子显微镜（cryo-EM）随后进行分子动态柔性拟合（MDFF）模拟来分析HAdv 5-FVII复合物。结果表明，虽然六邻体氨基酸T423、E424和T425（较早被鉴定为FX结合的关键氨基酸）也参与介导FVII的结合，但FVII GLA结构域位于表面暴露的六邻体三聚体抑制内，与FX所发现的方向不同。此外，我们发现当与六邻体结合时，两个近端FVII分子通过其丝氨酸蛋白酶（SP）结构域相互作用，并将潜在的硫酸乙酰肝素蛋白聚糖（HSPG）受体结合残基埋在二聚体界面内。相比之下，早期的冷冻电镜研究的Ad-FX相互作用显示没有证据的二聚体形成。FVII与Ad结合的二聚化可能是Ad-FX和Ad-FVII复合物的差异感染性的一个促成机制因素，尽管这两种凝血因子与病毒的高亲和力结合。
Adenoviruses (Ads) are promising vectors for therapeutic interventions in humans. When injected into the bloodstream, Ad vectors can bind several vitamin K-dependent blood coagulation factors, which contributes to virus sequestration in the liver by facilitating transduction of hepatocytes. Although both coagulation factors FVII and FX bind the hexon protein of human Ad serotype 5 (HAdv5) with a very high affinity, only FX appears to play a role in mediating Ad-hepatocyte transduction in vivo. To understand the discrepancy between efficacy of FVII binding to hexon and its apparently poor capacity for supporting virus cell entry, we analyzed the HAdv5-FVII complex by using high-resolution cryo-electron microscopy (cryo-EM) followed by molecular dynamic flexible fitting (MDFF) simulations. The results indicate that although hexon amino acids T423, E424, and T425, identified earlier as critical for FX binding, are also involved in mediating binding of FVII, the FVII GLA domain sits within the surface-exposed hexon trimer depression in a different orientation from that found for FX. Furthermore, we found that when bound to hexon, two proximal FVII molecules interact via their serine protease (SP) domains and bury potential heparan sulfate proteoglycan (HSPG) receptor binding residues within the dimer interface. In contrast, earlier cryo-EM studies of the Ad-FX interaction showed no evidence of dimer formation. Dimerization of FVII bound to Ad may be a contributing mechanistic factor for the differential infectivity of Ad-FX and Ad-FVII complexes, despite high-affinity binding of both these coagulation factors to the virus.