Modulation of viral replication, apoptosis and antiviral response by induction and mutual regulation of EGR and AP-1 family genes during coronavirus infection

Abstract

Coronaviruses have evolved a variety of strategies to exploit normal cellular processes and signalling pathways for their efficient reproduction in a generally hostile cellular environment. One immediate-early response gene (IEG) family, the AP-1 gene family, was previously shown to be activated by coronavirus infection. In this study, we report that another IEG family, the EGR family, is also activated in cells infected with four different coronaviruses in three genera, i.e. gammacoronavirus infectious bronchitis virus (IBV), alphacoronaviruses porcine epidemic diarrhoea virus (PEDV) and human coronavirus-229E (HCoV-229E), and betacoronavirus HCoV-OC43. Knockdown of EGR1 reduced the expression of cJUN and cFOS, and knockdown of cJUN and/or cFOS reduced the expression of EGR1, demonstrating that these two IEG families may be cross-activated and mutual regulated. Furthermore, ERK1/2 was identified as an upstream kinase, and JNK and p38 as inhibitors of EGR1 activation in coronavirus-infected cells. However, upregulation of EGR family genes, in particular EGR1, appears to play a differential role in regulating viral replication, apoptosis and antiviral response. EGR1 was shown to play a limited role in regulation of coronavirus replication, and an anti-apoptotic role in cells infected with IBV or PEDV, but not in cells infected with HCoV-229E. Upregulation of EGR1 may also play a differential role in the regulation of antiviral response against different coronaviruses. This study reveals a novel regulatory network shared by different coronaviruses in the immediate-early response of host cells to infection.

Transcriptomic analysis reveals crucial regulatory roles of immediate-early response genes and related signaling pathways in coronavirus infectious bronchitis virus infection

“…Among them, GADD34 and GADD153 were significantly upregulated by IBV infection-induced ER stress response and play important roles in regulating IBV replication and virus-host interaction ( Liao et al, 2013 ; Wang et al, 2009a , Wang et al, 2009b ). Our studies also reveal the essential roles of EGR family genes, especially EGR1, in regulating coronavirus replication and pathogenesis, and SGK1 in virion assembly and release ( Yuan et al, 2022 ; Zhu et al, in preparation).…”

“…The top 10 genes with the most significant differential expression during IBV infection were FOXJ1, FOSB, cFOS, EGR4, CRB2, CASS4, ZNF474, RRAD, EGR3 and EGR1. Using this information as starting points, the regulatory roles of several DEGs and related cellular pathways in coronavirus replication and pathogenesis were studied in detail in our previous publications ( Li et al, 2022 ; Yuan et al, 2020 , 2022 ; Zhu et al, 2021 ).…”

Examining the role of EGR1 during viral infections

“…EGR1 was found to be activated via ERK1/2 signaling and loss of EGR1 via siRNA resulted in a significant decrease in viral replication (~2 log 10 ) suggesting EGR1 may play a role in viral replication (Cai et al, 2006). More recent studies found EGR1 mRNA and protein levels are upregulated following infection with infectious bronchitis virus (IBV) in H1299, Vero, and DF1 cells (Yuan et al, 2022). Other coronaviruses examined, including porcine epidemic diarrhea virus (PEDV), human coronavirus (HCoV)-229E, and HCoV-OC43, were also found to activate EGR1 at both the mRNA and protein level following infection in both H1299 and Vero cells (Yuan et al, 2022).…”

“…More recent studies found EGR1 mRNA and protein levels are upregulated following infection with infectious bronchitis virus (IBV) in H1299, Vero, and DF1 cells (Yuan et al, 2022). Other coronaviruses examined, including porcine epidemic diarrhea virus (PEDV), human coronavirus (HCoV)-229E, and HCoV-OC43, were also found to activate EGR1 at both the mRNA and protein level following infection in both H1299 and Vero cells (Yuan et al, 2022). Following siRNA-mediated knock-down of EGR1, it was shown that loss of EGR1 has no significant impact on IBV replication but knock-down cells had significantly higher percentages of PARP cleavage, an indicator of cell death, which suggests that EGR1 may function as a survival factor during IBV infection of H1299 cells (Yuan et al, 2022).…”

“…Other coronaviruses examined, including porcine epidemic diarrhea virus (PEDV), human coronavirus (HCoV)-229E, and HCoV-OC43, were also found to activate EGR1 at both the mRNA and protein level following infection in both H1299 and Vero cells (Yuan et al, 2022). Following siRNA-mediated knock-down of EGR1, it was shown that loss of EGR1 has no significant impact on IBV replication but knock-down cells had significantly higher percentages of PARP cleavage, an indicator of cell death, which suggests that EGR1 may function as a survival factor during IBV infection of H1299 cells (Yuan et al, 2022). Knock-down of EGR1 resulted in slightly, but not significantly, reduced replication of PEDV and increased PARP cleavage, similar to results observed with IBV.…”