The PERK Arm of the Unfolded Protein Response Negatively Regulates Transmissible Gastroenteritis Virus Replication by Suppressing Protein Translation and Promoting Type I Interferon Production

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 alphacoronavirus transmissible gastroenteritis virus (TGEV) induced ER stress and triggered the unfolded protein response (UPR) and, and ER stress negatively regulated TGEV replication Although TGEV infection activated all three UPR pathways (activating transcription factor 6 [ATF6], inositol-requiring enzyme 1 [IRE1], and protein kinase R-like ER kinase [PERK]), the virus-triggered UPR suppressed TGEV replication in both swine testicular (ST) and IPEC-J2 cells primarily through activation of the PERK-eukaryotic initiation factor 2α (eIF2α) axis, as shown by functional studies with overexpression, small interfering RNA (siRNA), or specific chemical inhibitors. Moreover, we demonstrated that PERK-eIF2α axis-mediated inhibition of TGEV replication occurs through phosphorylated eIF2α-induced overall 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. The induction of ER stress is a common outcome in cells infected with coronaviruses. The UPR initiated by ER stress is actively involved in viral replication and modulates the host innate responses to the invading viruses, but these underlying mechanisms remain incompletely understood. We show here that infection with the alphacoronavirus TGEV elicited ER stress and, and the UPR PERK-eIF2α branch was predominantly responsible for the suppression of TGEV replication by ER stress. Furthermore, the PERK-eIF2α axis inhibited TGEV replication through direct inhibition of viral proteins due to global translation inhibition and type I IFN induction. These findings highlight a critical role of the UPR PERK-eIF2α pathway in modulating host innate immunity and coronavirus replication.

The Coronavirus Transmissible Gastroenteritis Virus Evades the Type I Interferon Response through IRE1α-Mediated Manipulation of the MicroRNA miR-30a-5p/SOCS1/3 Axis

“…1A), indicating that Tg-derived ER stress reduces miR-30a-5p abundance. Our labs and others have shown that, similar to other coronaviral infections, TGEV infection triggers significant ER stress and initiates all three UPR pathways (1,8). To explore whether miR-30a-5p could be regulated by TGEV infection, we initially monitored miR-30a-5p expression in ST cells after TGEV infection at different multiplicities of infection (MOIs).…”

Porcine parvovirus replication is suppressed by activation of the PERK signaling pathway and endoplasmic reticulum stress-mediated apoptosis

“…Activation of ER stress is usually mediated by all three signaling pathways or one or two pathways during virus infection. Transmissible gastroenteritis virus, Borna disease virus, and dengue virus activate ER stress by targeting three branches of the UPR (Lee et al, 2018;Williams and Lipkin, 2006;Xue et al, 2018). Newcastle disease virus induces activation of ER stress via the PERK and ATF6 pathways, but not XBP1 (Cheng et al, 2016).…”

“…Cells were harvested at 12, 24, 36, and 48 h post-infection (hpi) and total RNA was extracted using an RNeasy mini kit (Qiagen, Hilden, Germany) and reverse-transcribed into complementary DNA (cDNA) using the PrimeScript™ II 1st strand cDNA synthesis kit (Takara, Dalian, China). To detect whether XBP1 splicing occurred in PPV-infected cells, RT-PCR was performed using specific primers for XBP1 as previously described (Xue et al, 2018). The PCR products were digested with PstI and separated by electrophoresis in 2% agarose gels.…”

Superinfection and cell regeneration can lead to chronic viral coinfections

“…But other mechanisms might alter the rates of internal protein and RNA production. Infection of a cell induces cellular responses that inhibit the replication of the virus ( Tang et al, 2014;Tian et al, 2012;Xue et al, 2018 ) while viruses have developed mechanisms to prevent these responses ( Wang et al, 2014 ). Thus, if one of the viruses involved in the superinfection can inhibit a cellular response that suppresses viral replication, the other virus can be produced more quickly than it would if it were infecting the cell alone.…”