Activation of the Nipah Virus Fusion Protein in MDCK Cells Is Mediated by Cathepsin B within the Endosome-Recycling Compartment
Activation of the Nipah Virus Fusion Protein in MDCK Cells Is Mediated by Cathepsin B within the Endosome-Recycling Compartment
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DOI：
10.1128/jvi.06628-11
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发表时间：
2012-04-01
影响因子：
5.4
通讯作者：
Maisner, Andrea
中科院分区：
文献类型：
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作者：
Diederich, Sandra;Sauerhering, Lucie;Maisner, Andrea
高致病性尼帕病毒(NivF)融合蛋白的蛋白水解性激活是产生感染性颗粒和通过细胞间融合传播病毒的先决条件。与其他副粘病毒融合蛋白不同的是，功能性的Niv F激活需要内吞作用和内体酶在单一裂解部位的pH依赖的切割。利用Vero原型细胞，组织蛋白酶L先前被鉴定为一种裂解酶。与Vero细胞相比，MDCK细胞在Niv感染和Niv F转基因细胞中显示出显著更高的F裂解率。令人惊讶的是，这既不能用F内吞速率的增加解释，也不能用组织蛋白酶L活性的升高来解释。相反，mDCK细胞不显示任何可检测到的组织蛋白L活性。虽然我们可以确定组织蛋白酶L负责在Vero细胞中激活F，但抑制剂研究表明，在MDCK细胞中，组织蛋白酶B是F蛋白切割和病原性新城疫病毒的有效复制所必需的。内吞的F蛋白和组织蛋白酶B与内体标志蛋白EEA-1(EEA-1)、Rab4和Rab11显著共定位，支持MDCK细胞早期和循环内小体有效切割F的观点，而NIV F不需要通过晚期内体隔室运输来激活F。综上所述，这项研究首次表明，内体组织蛋白酶B在高致病性新城疫病毒的激活过程中可以发挥功能作用。
Proteolytic activation of the fusion protein of the highly pathogenic Nipah virus (NiV F) is a prerequisite for the production of infectious particles and for virus spread via cell-to-cell fusion. Unlike other paramyxoviral fusion proteins, functional NiV F activation requires endocytosis and pH-dependent cleavage at a monobasic cleavage site by endosomal proteases. Using prototype Vero cells, cathepsin L was previously identified to be a cleavage enzyme. Compared to Vero cells, MDCK cells showed substantially higher F cleavage rates in both NiV-infected and NiV F-transfected cells. Surprisingly, this could not be explained either by an increased F endocytosis rate or by elevated cathepsin L activities. On the contrary, MDCK cells did not display any detectable cathepsin L activity. Though we could confirm cathepsin L to be responsible for F activation in Vero cells, inhibitor studies revealed that in MDCK cells, cathepsin B was required for F-protein cleavage and productive replication of pathogenic NiV. Supporting the idea of an efficient F cleavage in early and recycling endosomes of MDCK cells, endocytosed F proteins and cathepsin B colocalized markedly with the endosomal marker proteins early endosomal antigen 1 (EEA-1), Rab4, and Rab11, while NiV F trafficking through late endosomal compartments was not needed for F activation. In summary, this study shows for the first time that endosomal cathepsin B can play a functional role in the activation of highly pathogenic NiV.