Porcine Epidemic Diarrhea Virus Infection Inhibits Interferon Signaling by Targeted Degradation of STAT1

Abstract

Porcine epidemic diarrhea virus (PEDV) is a worldwide-distributed alphacoronavirus, but the pathogenesis of PEDV infection is not fully characterized. During virus infection, type I interferon (IFN) is a key mediator of innate antiviral responses. Most coronaviruses develop some strategy for at least partially circumventing the IFN response by limiting the production of IFN and by delaying the activation of the IFN response. However, the molecular mechanisms by which PEDV antagonizes the antiviral effects of interferon have not been fully characterized. Especially, how PEDV impacts IFN signaling components has yet to be elucidated. In this study, we observed that PEDV was relatively resistant to treatment with type I IFN. Western blot analysis showed that STAT1 expression was markedly reduced in PEDV-infected cells and that this reduction was not due to inhibition of STAT1 transcription. STAT1 downregulation was blocked by a proteasome inhibitor but not by an autophagy inhibitor, strongly implicating the ubiquitin-proteasome targeting degradation system. Since PEDV infection-induced STAT1 degradation was evident in cells pretreated with the general tyrosine kinase inhibitor, we conclude that STAT1 degradation is independent of the IFN signaling pathway. Furthermore, we report that PEDV-induced STAT1 degradation inhibits IFN-␣ signal transduction pathways. Pharmacological inhibition of STAT1 degradation rescued the ability of the host to suppress virus replication. Collectively, these data show that PEDV is capable of subverting the type I interferon response by inducing STAT1 degradation. IMPORTANCEIn this study, we show that PEDV is resistant to the antiviral effect of IFN. The molecular mechanism is the degradation of STAT1 by PEDV infection in a proteasome-dependent manner. This PEDV infection-induced STAT1 degradation contributes to PEDV replication. Our findings reveal a new mechanism evolved by PEDV to circumvent the host antiviral response. P orcine epidemic diarrhea virus (PEDV) is an enveloped, positive-stranded RNA virus in the genus Alphacoronavirus, family Coronaviridae, order Nidovirales (1, 2). PEDV is the causative agent of porcine epidemic diarrhea (PED), an acute, highly contagious, and devastating viral enteric disease with a high mortality rate in suckling piglets. Since PED was first reported in England in 1971 (3), the disease has broken out frequently in many pig-producing countries (4-9). Despite the availability of vaccines, outbreaks continue to increase and pose problems for the swine industry, as well as public health concerns (10-12).During viral infection, the innate immune response is often activated, leading to the induction of type I interferon (IFN-I), or alpha/beta interferon (IFN-␣/␤). IFN-␣/␤ is a potent cytokine of critical importance in controlling viral infections and priming adaptive immune responses (13). The biological activities of IFN-I are initiated by the binding of IFN-␣/␤ to its cognate receptors on the cell surface (14, 15). The binding of IFN-I to its rec...

Comparative Proteome Analysis of Porcine Jejunum Tissues in Response to a Virulent Strain of Porcine Epidemic Diarrhea Virus and Its Attenuated Strain

“…Among them, STAT1 and STAT2 are the most important in the IFN signaling pathway [23]. In vitro studies have demonstrated that PEDV infection inhibited the interferon signaling by targeted degradation of STAT1 [20,32]. However, in this work, no significant change was found in STAT1 and STAT2 in the two PEDV infected groups.…”

Tight Junction Protein Occludin Is a Porcine Epidemic Diarrhea Virus Entry Factor

“…Vero E6 (African green monkey kidney epithelial cells), IPEC-J2 (porcine intestinal epithelial cell clone J2), and BHK (baby hamster kidney fibroblasts) cell lines were grown and maintained in Dulbecco minimum essential medium (DMEM) supplemented with 10% heatinactivated fetal bovine serum (FBS; Thermo Fisher) (58). All cells were cultured in a humidified atmosphere at 37°C and 5% CO 2 .…”

“…An immunofluorescence assay was performed as previously described (58). Briefly, Vero E6 and IPEC-J2 cell monolayers were inoculated with PEDV at MOIs of 0.1 and 1, respectively.…”

Genome-wide analysis of differentially expressed genes and the modulation of PEDV infection in Vero E6 cells

“…It is generally believed that the type I (IFNα, IFN-β) and type III IFNs (IFN-λ2, IFN-λ3) play essential roles in antiviral defense [11]. Many viruses, including coronaviruses, have evolved strategies to counteract the signaling cascades of the innate immune system, especially through inhibiting IFN signaling and reduction of IFN production [12]. Viral proteins from different viruses, including influenza virus [13], Herpes virus [14], Coronaviruses severe acute respiratory syndrome (SARS) [15], Middle east respiratory syndrome (MERS) [16] and PEDV [17] have been identified as IFN antagonists.…”