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J Biol Chem. 2017 Jun 16;292(24):10262-10274. doi: 10.1074/jbc.M116.745729. Epub 2017 Apr 28.

Enterovirus 71 suppresses interferon responses by blocking Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling through inducing karyopherin-α1 degradation.

Wang C1,2,3, Sun M1,3, Yuan X1,3, Ji L1,3, Jin Y4,3, Cardona CJ5, Xing Z6,5.

Author information

1
From the Medical School and Jiangsu Provincial Key Laboratory of Medicine, Nanjing University, Nanjing 210008, China.
2
the Clinical Medical College, Xi'an Medical University, Xi'an 710021, China.
3
the Nanjing Children's Hospital, Nanjing Medical University, Nanjing 210029, China, and.
4
From the Medical School and Jiangsu Provincial Key Laboratory of Medicine, Nanjing University, Nanjing 210008, China, jinyuldyy@163.com.
5
the Department of Veterinary Biomedical Sciences, College of Veterinary Medicine, University of Minnesota at Twin Cities, St. Paul, Minnesota 55108.
6
From the Medical School and Jiangsu Provincial Key Laboratory of Medicine, Nanjing University, Nanjing 210008, China, zxing@umn.edu zxing@nju.edu.cn.

Abstract

Enterovirus 71 (EV71) has emerged as one of the most important enteroviruses since the eradication of poliovirus, and it causes severe neurological symptoms for which no effective antiviral drugs are available. Type I interferons (IFN) α/β have been used clinically as antiviral therapy as the first line of defense against virus infections successfully for decades. However, treatment with type I interferons has not been effective in patients with EV71 infection. In this study, we found that in cells pretreated with IFN-β, EV71 infection could still lead to a cytopathic effect, and the viral replication was not affected. The mechanism by which EV71 antagonizes interferon signaling, however, has been controversial. Our study indicated that EV71 infection did not inhibit phosphorylation of STAT1/2 induced by IFN-β stimulation, but p-STAT1/2 transport into the nucleus was significantly blocked. We showed that EV71 infection reduced the formation of STAT/karyopherin-α1 (KPNA1) complex upon interferon stimulation and that the virus down-regulated the expression of KPNA1, a nuclear localization signal receptor for p-STAT1. Using specific caspase inhibitors and siRNA for caspase-3, we demonstrated that EV71 infection induced degradation of cellular KPNA1 in a caspase-3-dependent manner, which led to decreased induction of interferon-inducible genes and IFN response. Viral 2A and 3C proteases did not degrade KPNA1, inhibit the activity of ISRE or suppress the transcription of interferon-inducible genes induced by IFN-β. Our study demonstrates a novel mechanism by which antiviral signaling is suppressed through degradation of KPNA1 by activated caspase-3 induced in an enteroviral infection.

KEYWORDS:

Janus kinase (JAK); RNA virus; STAT transcription factor; interferon; protein expression

PMID:
28455446
PMCID:
PMC5473229
DOI:
10.1074/jbc.M116.745729
[Indexed for MEDLINE]
Free PMC Article

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