Journal of Virology：哈獸研發現內質網應激調控冠狀病毒TGEV感染的新機制

導 讀

豬傳染性胃腸炎病毒（Transmissible Gastroenteritis Virus，TGEV）屬於α冠狀病毒，是引起規模化養豬場新生仔豬腹瀉性死亡的重要原因，給我國養豬業造成了嚴重的經濟損失。近日，中國農業科學院哈爾濱獸醫研究所馮力研究員團隊在國際期刊Journal of Virology發表了題為The PERK Arm of the Unfolded Protein Response Negatively Regulates Transmissible Gastroenteritis Virus Replication by Suppressing Protein Translation and Promoting Type I IFN Production的論文。研究闡明了內質網應激（ER stress）抑制TGEV複製的分子機制，為研發抗冠狀病毒藥物靶點和制定抗病毒新策略提供了重要理論依據。

Fig .TGEV感染通過PERK通路激活導致eIF2α磷酸化模式圖

研究背景

豬傳染性胃腸炎病毒（TransmissibleGastroenteritis Virus，TGEV）屬於α冠狀病毒，能引起豬嘔吐、脫水和嚴重腹瀉等癥狀，2周齡內的仔豬死亡率可達90%-100%。TGEV是引起規模化養豬場新生仔豬腹瀉性死亡的重要原因，給我國養豬業造成了嚴重的經濟損失。

內質網作為蛋白質摺疊和翻譯後修飾的重要場所，是病毒複製和成熟的必需細胞器。病毒感染後，細胞內合成大量的病毒蛋白，從而增加內質網的負擔，進而增加了未摺疊蛋白和錯誤摺疊蛋白的堆積。病毒感染後通常會誘發內質網應激，但對於內質網應激如何調控冠狀病毒的複製及其調控機制目前還不明確。

結果速覽

本研究發現：

（1）TGEV感染在體內和體外均能誘導內質網應激，激活未摺疊蛋白反應，進一步研究發現TGEV誘導的內質網應激負調控病毒複製（圖1）。儘管TGEV感染能夠不同程度的激活PERK、ATF6和IRE1三個信號通路（圖2-3），利用RNA干擾和特異性抑製劑處理髮現僅PERK通路發揮抑制TGEV複製的功能（圖4）。

（2）分子機制研究發現，TGEV感染通過PERK通路激活導致eIF2α磷酸化，磷酸化的eIF2α通過抑制蛋白翻譯抑制TGEV複製；除了對病毒複製直接的抑制作用，PERK-eIF2α通路還激活NF-κB，促進I型干擾素產生，從而抑制TGEV複製（圖5）。

Fig. 1.TGEV infection induces ER stress in ST and IPEC-J2 cells

Fig 2. TGEV infection activates all three UPR signaling pathways in vitro.

Fig 3. TGEV infection activates all three UPR signaling pathways in vivo.

Fig 4. The activated PERK-eIF2? pathway of the UPR inhibits TGEVreplication.

Fig5 . Model depicting the viral suppression by PERK-eIF2α pathway 1027 activation during TGEV infection

結 語

本研究表明內質網應激的PERK-eIF2α通路在調節天然免疫和冠狀病毒複製方面發揮重要作用。研究受到國家重點研發計劃（2016YFD0500100和2017YFD0502200）的資助，薛美博士為本文第一作者，馮力研究員和劉平黃研究員為共同通訊作者。

ABSTRACT

Coronavirus replication is closely associated with the endoplasmic reticulum (ER), the primary cellular organelle for protein synthesis, folding, and modification. ER stress is a common consequence in coronavirus-infected cells. However, how the virus-induced ER stress influences coronavirus replication and pathogenesis remains controversial. Here, we demonstrated that infection with the alpha coronavirus transmissible gastroenteritis virus (TGEV) induced ER stress and triggered the unfolded protein response (UPR) in vitro and in vivo, and ER stress negatively regulated TGEV replication in vitro. Although TGEV infection activated all three UPR pathways (ATF6, IRE1, and PERK), the virus-triggered UPR suppressed TGEV replication in both ST and IPEC-J2 cells primarily through activation ofthe PERK-eIF2α axis, as shown by functional studies with overexpression, siRNA,or specific chemical inhibitors. Moreover, we demonstrated that PERK-eIF2αaxis-mediated inhibition of TGEV replication is through phosphorylated eIF2α-inducedoverall attenuation of protein translation. In addition to direct inhibition of viral production, the PERK-eIF2α pathway activated NF-κB and then facilitated type I IFN production, resulting in TGEV suppression. Taken together, our results suggest that the TGEV-triggered PERK-eIF2α pathway negatively regulates TGEV replication and represents a vital aspect of host innate responses to invading pathogens.

參考文獻：

1. Mei Xue, Fang Fu, Yanlong Ma, XinZhang, Liang Li, Li Feng* and Pinghuang Liu*.The PERK Arm of the UnfoldedProtein Response Negatively Regulates Transmissible Gastroenteritis VirusReplication by Suppressing Protein Translation and Promoting Type I IFNProduction. Accepted manuscript posted online 16 May 2018, doi: 10.1128/JVI.00431-18

http://jvi.asm.org/content/early/2018/05/10/JVI.00431-18.abstract

2.哈獸研官網：哈獸研發現內質網應激調控冠狀病毒TGEV感染的新機制。

http://www.hvri.ac.cn/html/zonghexinwen/keyanjinzhan/2018/0521/1674.html

本期編輯：Annabella

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