Granato Marisa, Santarelli Roberta, Farina Antonella, Gonnella Roberta, Lotti Lavinia Vittoria, Faggioni Alberto, Cirone Mara
Department of Experimental Medicine, Sapienza University of Rome, Rome, Italy.
Department of Experimental Medicine, Sapienza University of Rome, Rome, Italy
J Virol. 2014 Nov;88(21):12715-26. doi: 10.1128/JVI.02199-14. Epub 2014 Aug 20.
Autophagy is a catabolic pathway that helps cells to survive under stressful conditions. Cells also use autophagy to clear microbiological infections, but microbes have learned how to manipulate the autophagic pathway for their own benefit. The experimental evidence obtained in this study suggests that the autophagic flux is blocked at the final steps during the reactivation of Epstein-Barr virus (EBV) from latency. This is indicated by the level of the lipidated form of LC3 that does not increase in the presence of bafilomycin and by the lack of colocalization of autophagosomes with lysosomes, which correlates with reduced Rab7 expression. Since the inhibition of the early phases of autophagy impaired EBV replication and viral particles were observed in autophagic vesicles in the cytoplasm of producing cells, we suggest that EBV exploits the autophagic machinery for its transportation in order to enhance viral production. The autophagic block was not mediated by ZEBRA, an immediate-early EBV lytic gene, whose transfection in Ramos, Akata, and 293 cells promoted a complete autophagic flux. The block occurred only when the complete set of EBV lytic genes was expressed. We suggest that the inhibition of the early autophagic steps or finding strategies to overcome the autophagic block, allowing viral degradation into the lysosomes, can be exploited to manipulate EBV replication.
This study shows, for the first time, that autophagy is blocked at the final degradative steps during EBV replication in several cell types. Through this block, EBV hijacks the autophagic vesicles for its intracellular transportation and enhances viral production. A better understanding of virus-host interactions could help in the design of new therapeutic approaches against EBV-associated malignancies.
自噬是一种分解代谢途径，可帮助细胞在应激条件下存活。细胞也利用自噬来清除微生物感染，但微生物已经学会如何操纵自噬途径以自身获益。本研究获得的实验证据表明，在爱泼斯坦-巴尔病毒（EBV）从潜伏状态重新激活的最后步骤中，自噬通量被阻断。这通过在巴弗洛霉素存在下LC3脂化形式的水平不增加以及自噬体与溶酶体缺乏共定位来表明，这与Rab7表达降低相关。由于自噬早期阶段的抑制损害了EBV复制，并且在产生细胞的细胞质中的自噬小泡中观察到病毒颗粒，我们认为EBV利用自噬机制进行运输以增强病毒产生。自噬阻断不是由EBV早期即刻裂解基因ZEBRA介导的，其在Ramos、Akata和293细胞中的转染促进了完整的自噬通量。阻断仅在表达完整的EBV裂解基因集时发生。我们认为，抑制自噬早期步骤或找到克服自噬阻断的策略，使病毒能够在溶酶体中降解，可用于操纵EBV复制。
本研究首次表明，在几种细胞类型中，EBV复制期间自噬在最后的降解步骤被阻断。通过这种阻断，EBV劫持自噬小泡进行细胞内运输并增强病毒产生。更好地理解病毒与宿主的相互作用有助于设计针对EBV相关恶性肿瘤的新治疗方法。
