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Orthopoxvirus K3 orthologs show virus- and host-specific inhibition of the antiviral protein kinase PKR.

ABSTRACT: The antiviral protein kinase R (PKR) is an important host restriction factor, which poxviruses must overcome to productively infect host cells. To inhibit PKR, many poxviruses encode a pseudosubstrate mimic of the alpha subunit of eukaryotic translation initiation factor 2 (eIF2), designated K3 in vaccinia virus. Although the interaction between PKR and eIF2? is highly conserved, some K3 orthologs from host-restricted poxviruses were previously shown to inhibit PKR in a species-specific manner. To better define this host range function, we compared the sensitivity of PKR from 17 mammals to inhibition by K3 orthologs from closely related orthopoxviruses, a genus with a generally broader host range. The K3 orthologs showed species-specific inhibition of PKR and exhibited three distinct inhibition profiles. In some cases, PKR from closely related species showed dramatic differences in their sensitivity to K3 orthologs. Vaccinia virus expressing the camelpox virus K3 ortholog replicated more than three orders of magnitude better in human and sheep cells than a virus expressing vaccinia virus K3, but both viruses replicated comparably well in cow cells. Strikingly, in site-directed mutagenesis experiments between the variola virus and camelpox virus K3 orthologs, we found that different amino acid combinations were necessary to mediate improved or diminished inhibition of PKR derived from different host species. Because there is likely a limited number of possible variations in PKR that affect K3-interactions but still maintain PKR/eIF2? interactions, it is possible that by chance PKR from some potential new hosts may be susceptible to K3-mediated inhibition from a virus it has never previously encountered. We conclude that neither the sensitivity of host proteins to virus inhibition nor the effectiveness of viral immune antagonists can be inferred from their phylogenetic relatedness but must be experimentally determined.

SUBMITTER: Park C

PROVIDER: S-EPMC7840043 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

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Orthopoxvirus K3 orthologs show virus- and host-specific inhibition of the antiviral protein kinase PKR.

Park Chorong C Peng Chen C Rahman M Julhasur MJ Haller Sherry L SL Tazi Loubna L Brennan Greg G Rothenburg Stefan S

PLoS pathogens 20210114 1

The antiviral protein kinase R (PKR) is an important host restriction factor, which poxviruses must overcome to productively infect host cells. To inhibit PKR, many poxviruses encode a pseudosubstrate mimic of the alpha subunit of eukaryotic translation initiation factor 2 (eIF2), designated K3 in vaccinia virus. Although the interaction between PKR and eIF2α is highly conserved, some K3 orthologs from host-restricted poxviruses were previously shown to inhibit PKR in a species-specific manner. ...[more]

PMID: 33444388

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Project description:Arenaviruses are enveloped negative-strand RNA viruses that cause significant human disease. These viruses encode only four proteins to accomplish the viral life cycle, so each arenavirus protein likely plays unappreciated accessory roles during infection. Here we used immunoprecipitation and mass spectrometry to identify human proteins that interact with the nucleoproteins (NPs) of the Old World arenavirus lymphocytic choriomeningitis virus (LCMV) and the New World arenavirus Junín virus (JUNV) strain Candid #1. Bioinformatic analysis of the identified protein partners of NP revealed that host translation appears to be a key biological process engaged during infection. In particular, NP associates with the double-stranded RNA (dsRNA)-activated protein kinase (PKR), a well-characterized antiviral protein that inhibits cap-dependent protein translation initiation via phosphorylation of eIF2?. JUNV infection leads to increased expression of PKR as well as its redistribution to viral replication and transcription factories. Further, phosphorylation of PKR, which is a prerequisite for its ability to phosphorylate eIF2?, is readily induced by JUNV. However, JUNV prevents this pool of activated PKR from phosphorylating eIF2?, even following exposure to the synthetic dsRNA poly(I·C), a potent PKR agonist. This blockade of PKR function is highly specific, as LCMV is unable to similarly inhibit eIF2? phosphorylation. JUNV's ability to antagonize the antiviral activity of PKR appears to be complete, as silencing of PKR expression has no impact on viral propagation. In summary, we provide a detailed map of the host machinery engaged by arenavirus NPs and identify an antiviral pathway that is subverted by JUNV.IMPORTANCE Arenaviruses are important human pathogens for which FDA-approved vaccines do not exist and effective antiviral therapeutics are needed. Design of antiviral treatment options and elucidation of the mechanistic basis of disease pathogenesis will depend on an increased basic understanding of these viruses and, in particular, their interactions with the host cell machinery. Identifying host proteins critical for the viral life cycle and/or pathogenesis represents a useful strategy to uncover new drug targets. This study reveals, for the first time, the extensive human protein interactome of arenavirus nucleoproteins and uncovers a potent antiviral host protein that is neutralized during Junín virus infection. In so doing, it shows further insight into the interplay between the virus and the host innate immune response and provides an important data set for the field.

Dataset Information

Orthopoxvirus K3 orthologs show virus- and host-specific inhibition of the antiviral protein kinase PKR.

Publications

Orthopoxvirus K3 orthologs show virus- and host-specific inhibition of the antiviral protein kinase PKR.

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