3C pro of Foot-and-Mouth Disease Virus Antagonizes the Interferon Signaling Pathway by Blocking STAT1/STAT2 Nuclear Translocation

• Published in: Journal of virology 2014-05, Vol.88 (9), p.4908-4920
• Main Authors: Du, Yijun, Bi, Jingshan, Liu, Jiyu, Liu, Xing, Wu, Xiangju, Jiang, Ping, Yoo, Dongwan, Zhang, Yongguang, Wu, Jiaqiang, Wan, Renzhong, Zhao, Xiaomin, Guo, Lihui, Sun, Wenbo, Cong, Xiaoyan, Chen, Lei, Wang, Jinbao
• Format: Article
• Language: English
• ISSN: 0022-538X; 1098-5514
• DOI: 10.1128/JVI.03668-13

Foot-and-mouth disease virus (FMDV) causes a highly contagious, debilitating disease in cloven-hoofed animals with devastating economic consequences. To survive in the host, FMDV has evolved to antagonize the host type I interferon (IFN) response. Previous studies have reported that the leader proteinase (L pro ) and 3C pro of FMDV are involved in the inhibition of type I IFN production. However, whether the proteins of FMDV can inhibit type I IFN signaling is less well understood. In this study, we first found that 3C pro of FMDV functioned to interfere with the JAK-STAT signaling pathway. Expression of 3C pro significantly reduced the transcript levels of IFN-stimulated genes (ISGs) and IFN-stimulated response element (ISRE) promoter activity. The protein level, tyrosine phosphorylation of STAT1 and STAT2, and their heterodimerization were not affected. However, the nuclear translocation of STAT1/STAT2 was blocked by the 3C pro protein. Further mechanistic studies demonstrated that 3C pro induced proteasome- and caspase-independent protein degradation of karyopherin α1 (KPNA1), the nuclear localization signal receptor for tyrosine-phosphorylated STAT1, but not karyopherin α2, α3, or α4. Finally, we showed that the protease activity of 3C pro contributed to the degradation of KPNA1 and thus blocked STAT1/STAT2 nuclear translocation. Taken together, results of our experiments describe for the first time a novel mechanism by which FMDV evolves to inhibit IFN signaling and counteract host innate antiviral responses. IMPORTANCE We show that 3C pro of FMDV antagonizes the JAK-STAT signaling pathway by blocking STAT1/STAT2 nuclear translocation. Furthermore, 3C pro induces KPNA1 degradation, which is independent of proteasome and caspase pathways. The protease activity of 3C pro contributes to the degradation of KPNA1 and governs the ability of 3C pro to inhibit the JAK-STAT signaling pathway. This study uncovers a novel mechanism evolved by FMDV to antagonize host innate immune responses.