Abstract
The double-stranded RNA-activated protein kinase R (PKR) is a Type I interferon (IFN) stimulated gene that has important biological and immunological functions. In viral infections, in general, PKR inhibits or promotes viral replication, but PKR-IPNV interaction has not been previously studied. We investigated the involvement of PKR during infectious pancreatic necrosis virus (IPNV) infection using a custom-made rabbit antiserum and the PKR inhibitor C16. Reactivity of the antiserum to PKR in CHSE-214 cells was confirmed after IFNα treatment giving an increased protein level. IPNV infection alone did not give increased PKR levels by Western blot, while pre-treatment with PKR inhibitor before IPNV infection gave decreased eukaryotic initiation factor 2-alpha (eIF2α) phosphorylation. This suggests that PKR, despite not being upregulated, is involved in eIF2α phosphorylation during IPNV infection. PKR inhibitor pre-treatment resulted in decreased virus titers, extra- and intracellularly, concomitant with reduction of cells with compromised membranes in IPNV-permissive cell lines. These findings suggest that IPNV uses PKR activation to promote virus replication in infected cells.
Highlights
Type I interferon (IFNα/β) responses constitute some of the crucial innate responses against virus infections
We showed that infectious pancreatic necrosis virus (IPNV) infection of permissive cells resulted in eIF2α phosphorylation but Protein kinase R (PKR)
Our findings show that PKR is not PKRinduced is not induced in IPNV infected cells any of the time points examined
Summary
Type I interferon (IFNα/β) responses constitute some of the crucial innate responses against virus infections. The induction of these responses begins with the stimulation of IFN production that can be induced through different pathways [1]. An antiviral state is created characterized by increased transcription of several antiviral IFN stimulated genes (ISGs). Examples of these genes are those encoding the myxovirus resistance protein (MX), Protein kinase R (PKR) and ISG15 [2]. Genes encoding PKR have been characterized in different mammalian and fish species [3,4]. Phylogenetic analysis and amino acid sequence alignment of the kinase domain from mammalian and fish PKR revealed low sequence conservation some of the domains that are important for dimerization or substrate interaction were conserved [3]
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