Monson Ebony A, Crosse Keaton M, Das Mithun, Helbig Karla J
Department of Physiology, Anatomy and Microbiology, La Trobe University, Melbourne, Victoria.
PLoS One. 2018 Jan 2;13(1):e0190597. doi: 10.1371/journal.pone.0190597. eCollection 2018.
The cellular localisation of many innate signalling events following viral infection has yet to be elucidated, however there has been a few cases in which membranes of certain cellular organelles have acted as platforms to these events. Of these, lipid droplets (LDs) have recently been identified as signalling platforms for innate TLR7 and 9 signalling. Despite their wide range of similar roles in various metabolic pathways, LDs have been overlooked as potential platforms for antiviral innate signalling events. This study established an in vitro model to evaluate the efficiency of the early innate immune response in cells with reduced LD content to the viral mimics, dsDNA and dsRNA, and Sendai viral infection. Using RT-qPCR, the expression of IFN-β and IFN-λ was quantified following stimulation along with the expression of specific ISGs. Luciferase based assays evaluated the combined expression of ISRE-promoter driven ISGs under IFN-β stimulation. Cellular LD content did not alter the entry of fluorescently labelled viral mimics into cells, but significantly decreased the ability of both Huh-7 and HeLa cells to produce type I and III IFN, as well as downstream ISG expression, indicative of an impeded innate immune response. This observation was also seen during Sendai virus infection of HeLa cells, where both control and LD reduced cells replicated the virus to the same level, but a significantly impaired type I and III IFN response was observed in the LD reduced cells. In addition to altered IFN production, cells with reduced LD content exhibited decreased expression of specific antiviral ISGs: Viperin, IFIT-1 and OAS-1 under IFN-β stimulation; However the overall induction of the ISRE-promoter was not effected. This study implicates a role for LDs in an efficient early innate host response to viral infection and future work will endeavour to determine the precise role these important organelles play in induction of an antiviral response.
病毒感染后许多先天性信号事件的细胞定位尚未阐明,然而,有少数情况表明某些细胞器的膜充当了这些事件的平台。其中,脂滴(LDs)最近被确定为先天性TLR7和9信号的信号平台。尽管脂滴在各种代谢途径中具有广泛的相似作用,但它们作为抗病毒先天性信号事件的潜在平台却被忽视了。本研究建立了一个体外模型,以评估LD含量降低的细胞对病毒模拟物、双链DNA和双链RNA以及仙台病毒感染的早期先天性免疫反应效率。使用RT-qPCR,在刺激后对IFN-β和IFN-λ的表达以及特定ISG的表达进行定量。基于荧光素酶的测定评估了IFN-β刺激下ISRE启动子驱动的ISG的联合表达。细胞LD含量并未改变荧光标记的病毒模拟物进入细胞的情况,但显著降低了Huh-7和HeLa细胞产生I型和III型IFN以及下游ISG表达的能力,这表明先天性免疫反应受到阻碍。在HeLa细胞感染仙台病毒期间也观察到了这一现象,对照细胞和LD减少的细胞将病毒复制到相同水平,但在LD减少的细胞中观察到I型和III型IFN反应明显受损。除了IFN产生的改变外,LD含量降低的细胞在IFN-β刺激下还表现出特定抗病毒ISG的表达降低:Viperin、IFIT-1和OAS-1;然而,ISRE启动子的总体诱导没有受到影响。本研究表明脂滴在宿主对病毒感染的高效早期先天性反应中发挥作用,未来的工作将致力于确定这些重要细胞器在诱导抗病毒反应中的确切作用。