Autophagy Promotes Duck Tembusu Virus Replication by Suppressing p62/SQSTM1-Mediated Innate Immune Responses In Vitro.

Zhiqiang Hu,Mingshu Wang,Mujeeb Ur Rehman,Bin Tian,Mafeng Liu,Shun Chen,Xingcui Zhang,Dekang Zhu,Shaqiu Zhang,Yunya Liu,Anchun Cheng,Yanling Yu,Xinxin Zhao,Sai Mao,Qiao Yang,Ling Zhang,Leichang Pan,Zhongqiong Yin,Ying Wu,Xumin Ou,Juan Huang,Renyong Jia,Yuhong Pan

doi:10.3390/vaccines8010022

Abstract

Duck Tembusu virus (DTMUV) has recently appeared in ducks in China and the key cellular determiners for DTMUV replication in host cells remain unknown. Autophagy is an evolutionarily conserved cellular process that has been reported to facilitate flavivirus replication. In this study, we utilized primary duck embryo fibroblast (DEF) as the cell model and found that DTMUV infection triggered LC3-II increase and polyubiquitin-binding protein sequestosome 1 (p62) decrease, confirming that complete autophagy occurred in DEF cells. The induction of autophagy by pharmacological treatment increased DTMUV replication in DEF cells, whereas the inhibition of autophagy with pharmacological treatments or RNA interference decreased DTMUV replication. Inhibiting autophagy enhanced the activation of the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and interferon regulatory factor 7 (IRF7) pathways and increased the p62 protein level in DTMUV-infected cells. We further found that the overexpression of p62 decreased DTMUV replication and inhibited the activation of the NF-κB and IRF7 pathways, and changes in the NF-κB and IRF7 pathways were consistent with the level of phosphorylated TANK-binding kinase 1 (p-TBK1). Opposite results were found in p62 knockdown cells. In summary, we found that autophagy-mediated p62 degradation acted as a new strategy for DTMUV to evade host innate immunity.

Highlights

Duck Tembusu virus (DTMUV) is a single-strand positive sense RNA virus that is classified as a member of the Flavivirus genus within the Flaviviridae family [1]
We found many autophagosome-like vesicles (Figure 1B,C) in Rapa-treated duck embryo fibroblast (DEF) cells but just a few in mock-infected cells
We found that autophagy inhibition with knockdown of Beclin 1 and LC3B increased the mRNA levels of Type I interferons and interleukin 6 (IL-6) (Figure 5A) and enhanced interferon regulatory factor 7 (IRF7) and NF-κB promoter activation (Figure 5B)

Summary

Introduction

Duck Tembusu virus (DTMUV) is a single-strand positive sense RNA virus that is classified as a member of the Flavivirus genus within the Flaviviridae family [1]. It was first reported in South East. DTMUV infection has been associated with viral encephalitis in young ducks [4] and mice [5], which is similar to the neurologic symptoms caused by other flavivirus members such as Zika virus (ZIKA) [6], West Nile virus (WNV) [7], and Japanese encephalitis virus (JEV) [8]. The complete autophagy involves the enhancement of autophagosome biogenesis and the trafficking to lysosomes. Autophagic flux, which refers to the entire process of autophagy, is a more accurate index to judge autophagic activity. The p62 protein serves as a link between LC3 and ubiquitinated substrates [12], which become incorporated into the completed autophagosome and are degraded into autolysosomes, serving as an index of autophagic degradation [13]

Methods

Results

Discussion

Conclusion