Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
Department of General Medicine, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan Department of Primary Care Medicine, Taipei Medical University Hospital, Taipei, Taiwan.
J Virol. 2014 Jun;88(12):6793-804. doi: 10.1128/JVI.00045-14. Epub 2014 Apr 2.
Positive-sense RNA viruses, such as dengue virus (DENV), hijack the intracellular membrane machinery for their own replication. The Rab18 protein, a member of the Rab GTPase family, key regulators of membrane trafficking, is located on the organelles involved in DENV infection, such as the endoplasmic reticulum (ER) and lipid droplets (LDs). In this study, we addressed the potential involvement of Rab18 in DENV infection by using cells overexpressing the wild-type, GTP-bound active form, or GDP-bound inactive form of Rab18 and cells with Rab18 knockdown. DENV replication, measured by viral protein, viral RNA, and viral progeny production, as well as LD induction, was reduced in cells with inactive Rab18 and in cells deprived of Rab18 expression, suggesting a positive role of Rab18 in the DENV life cycle. Interestingly, the interaction of fatty acid synthase (FASN), a key lipogenic enzyme in lipid biosynthesis, with DENV NS3 protein relied on the conversion of the GDP-bound to the GTP-bound form of Rab18. Furthermore, the targeting of FASN to sites participating in DENV infection, such as the ER and LDs, depends on functional Rab18. Thus, Rab18-mediated membrane trafficking of FASN and NS3 facilitates DENV replication, probably by ensuring a sufficient and coordinated lipid supply for membrane proliferation and arrangement.
Infection by dengue virus (DENV), an important mosquito-borne virus threatening ∼40% of the world's population, can cause mild dengue fever or severe dengue hemorrhagic fever and dengue shock syndrome. The pathogenesis mechanisms of DENV-related diseases are not clear, but high viral replication is believed to be a risk factor for the severe form of DENV infection. Thus, understanding the detailed mechanism of DENV replication might help address this devastating virus. Here, we found that Rab18, a small GTPase involved in vesicle trafficking and located in the endoplasmic reticulum network and on the surfaces of lipid droplets, positively regulates DENV replication. The functional machinery of Rab18 is required to recruit the enzyme fatty acid synthase to sites of DENV replication and to interact with DENV NS3 protein to promote fatty acid biosynthesis. Thus, DENV usurps Rab18 to facilitate its own replication.
正链 RNA 病毒，如登革热病毒（DENV），劫持细胞内的膜机制进行自身复制。Rab18 蛋白是 Rab GTPase 家族的成员之一，是膜运输的关键调节剂，位于参与 DENV 感染的细胞器上，如内质网（ER）和脂滴（LDs）。在这项研究中，我们通过使用过表达野生型、GTP 结合的活性形式或 GDP 结合的无活性形式的 Rab18 的细胞以及 Rab18 敲低的细胞，来研究 Rab18 与 DENV 感染的潜在关联。通过病毒蛋白、病毒 RNA 和病毒后代产生来测量 DENV 复制，以及 LD 诱导，在具有无活性 Rab18 的细胞中和在缺乏 Rab18 表达的细胞中，DENV 复制减少，表明 Rab18 在 DENV 生命周期中具有积极作用。有趣的是，脂肪酸合酶（FASN）与 DENV NS3 蛋白的相互作用，依赖于 Rab18 的 GDP 结合形式到 GTP 结合形式的转换。此外，FASN 靶向参与 DENV 感染的部位，如内质网和 LD，依赖于功能性 Rab18。因此，Rab18 介导的 FASN 和 NS3 的膜运输促进了 DENV 的复制，可能通过确保足够的协调的脂质供应，用于膜增殖和排列。
登革热病毒（DENV）的感染，一种威胁着世界上约 40%人口的重要蚊媒病毒，可导致轻度登革热或严重登革出血热和登革休克综合征。DENV 相关疾病的发病机制尚不清楚，但高病毒复制被认为是 DENV 感染严重形式的一个危险因素。因此，了解 DENV 复制的详细机制可能有助于解决这种破坏性病毒。在这里，我们发现参与囊泡运输的小 GTPase Rab18 在内质网网络和脂滴表面，正向调节 DENV 复制。Rab18 的功能机械装置被需要来招募酶脂肪酸合酶到 DENV 复制部位，并与 DENV NS3 蛋白相互作用，以促进脂肪酸的生物合成。因此，DENV 劫持 Rab18 来促进自身复制。
