Nikolic Jovan, Civas Ahmet, Lama Zoé, Lagaudrière-Gesbert Cécile, Blondel Danielle
Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette, France.
PLoS Pathog. 2016 Oct 17;12(10):e1005942. doi: 10.1371/journal.ppat.1005942. eCollection 2016 Oct.
Stress granules (SGs) are membrane-less dynamic structures consisting of mRNA and protein aggregates that form rapidly in response to a wide range of environmental cellular stresses and viral infections. They act as storage sites for translationally silenced mRNAs under stress conditions. During viral infection, SG formation results in the modulation of innate antiviral immune responses, and several viruses have the ability to either promote or prevent SG assembly. Here, we show that rabies virus (RABV) induces SG formation in infected cells, as revealed by the detection of SG-marker proteins Ras GTPase-activating protein-binding protein 1 (G3BP1), T-cell intracellular antigen 1 (TIA-1) and poly(A)-binding protein (PABP) in the RNA granules formed during viral infection. As shown by live cell imaging, RABV-induced SGs are highly dynamic structures that increase in number, grow in size by fusion events, and undergo assembly/disassembly cycles. Some SGs localize in close proximity to cytoplasmic viral factories, known as Negri bodies (NBs). Three dimensional reconstructions reveal that both structures remain distinct even when they are in close contact. In addition, viral mRNAs synthesized in NBs accumulate in the SGs during viral infection, revealing material exchange between both compartments. Although RABV-induced SG formation is not affected in MEFs lacking TIA-1, TIA-1 depletion promotes viral translation which results in an increase of viral replication indicating that TIA-1 has an antiviral effect. Inhibition of PKR expression significantly prevents RABV-SG formation and favors viral replication by increasing viral translation. This is correlated with a drastic inhibition of IFN-B gene expression indicating that SGs likely mediate an antiviral response which is however not sufficient to fully counteract RABV infection.
应激颗粒（SGs）是无膜的动态结构，由mRNA和蛋白质聚集体组成，在多种环境细胞应激和病毒感染时迅速形成。它们在应激条件下作为翻译沉默mRNA的储存位点。在病毒感染期间，SG的形成导致先天性抗病毒免疫反应的调节，并且几种病毒具有促进或阻止SG组装的能力。在这里，我们表明狂犬病病毒（RABV）在感染细胞中诱导SG形成，这通过在病毒感染期间形成的RNA颗粒中检测SG标记蛋白Ras GTPase激活蛋白结合蛋白1（G3BP1）、T细胞胞内抗原1（TIA-1）和聚腺苷酸结合蛋白（PABP）得以揭示。活细胞成像显示，RABV诱导的SG是高度动态的结构，其数量增加，通过融合事件增大尺寸，并经历组装/拆卸循环。一些SG定位于靠近细胞质病毒工厂（即内基小体，NBs）的位置。三维重建显示，即使两者紧密接触，这两种结构仍保持 distinct。此外，在病毒感染期间，在NBs中合成的病毒mRNA在SGs中积累，揭示了两个区室之间的物质交换。尽管在缺乏TIA-1的MEF中RABV诱导的SG形成不受影响，但TIA-1的缺失促进病毒翻译，导致病毒复制增加，表明TIA-1具有抗病毒作用。抑制PKR表达显著阻止RABV-SG形成，并通过增加病毒翻译促进病毒复制。这与IFN-β基因表达的剧烈抑制相关，表明SGs可能介导一种抗病毒反应，然而这种反应不足以完全对抗RABV感染。
