The secreted form of dengue virus nonstructural protein NS1 is endocytosed by hepatocytes and accumulates in late endosomes: Implications for viral infectivity
The secreted form of dengue virus nonstructural protein NS1 is endocytosed by hepatocytes and accumulates in late endosomes: Implications for viral infectivity
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DOI：
10.1128/jvi.79.17.11403-11411.2005
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发表时间：
2005-09-01
影响因子：
5.4
通讯作者：
Flamand, M
中科院分区：
文献类型：
--
作者：
Alcon-LePoder, S;Drouet, MT;Flamand, M
黄病毒非结构蛋白NS1在感染的哺乳动物细胞中以三种不同的形式表达：一种是病毒复制所必需的细胞内膜相关形式，一种是可能参与信号转导的细胞表面相关形式，另一种是分泌型(SNS1)，其生物学特性尚不清楚。为了确定登革病毒(DEN)sNS1蛋白在体内的分布，我们用免疫组织学方法分析了纯化的DEN sNS1经尾静脉注射给成年小鼠后的组织趋向性。SNS1蛋白主要与肝脏有关，肝细胞似乎是主要的靶细胞。我们进一步证明sNS1能在体外被人Huh7和HepG2肝细胞有效地内吞。在内化后，该蛋白在细胞内被检测到至少48小时，而没有实质上的降解。电子显微镜证实，sNS1与内溶酶体室标志的共定位研究表明，该蛋白特异性地靶向于富含溶二磷脂酸的结构，这使人想起晚期的内吞体内。在Huh7细胞中sNS1的细胞内积累增强了罗丹明标记的葡聚糖的液相摄取。此外，用sNS1预先孵育Huh7细胞可增加感染登革热病毒同源毒株后的登革病毒产量。我们的结果表明，在体外，登革热病毒在肝细胞内体晚期的积聚增强了随后的登革热病毒感染，增加了sNS1可能有助于病毒在体内传播的可能性。
The flavivirus nonstructural protein NS1 is expressed as three discrete species in infected mammalian cells: an intracellular, membrane-associated form essential for viral replication, a cell surface-associated form that may be involved in signal transduction, and a secreted form (sNS1), the biological properties of which remain elusive. To determine the distribution of the dengue virus (DEN) sNS1 protein in vivo, we have analyzed by immunohistological means the tissue tropism of purified DEN sNS1 injected intravenously into adult mice. The sNS1 protein was found predominantly associated with the liver, where hepatocytes appeared to represent a major target cell. We further showed that sNS1 could be efficiently endocytosed by human Huh7 and HepG2 hepatocytes in vitro. After its internalization, the protein was detected intracellularly for at least 48 h without being substantially degraded. Colocalization studies of sNS1 with markers of the endolysosomal compartments revealed that the protein was specifically targeted to lysobisphosphatidic acid-rich structures reminiscent of late endosomes, as confirmed by electron microscopy. Intracellular accumulation of sNS1 in Huh7 cells enhanced the fluid phase uptake of rhodamine-labeled dextran. Furthermore, preincubation of Huh7 cells with sNS1 increased dengue virus production after infection with the homologous strain of DEN-1 virus. Our results demonstrate that the accumulation of DEN sNS1 in the late endosomal compartment of hepatocytes potentializes subsequent dengue virus infection in vitro, raising the possibility that sNS1 may contribute to viral propagation in vivo.