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Pseudorabies Virus Infection of Epithelial Cells Leads to Persistent but Aberrant Activation of the NF-?B Pathway, Inhibiting Hallmark NF-?B-Induced Proinflammatory Gene Expression.

ABSTRACT: The nuclear factor kappa B (NF-?B) is a potent transcription factor, activation of which typically results in robust proinflammatory signaling and triggering of fast negative feedback modulators to avoid excessive inflammatory responses. Here, we report that infection of epithelial cells, including primary porcine respiratory epithelial cells, with the porcine alphaherpesvirus pseudorabies virus (PRV) results in the gradual and persistent activation of NF-?B, illustrated by proteasome-dependent degradation of the inhibitory NF-?B regulator I?B and nuclear translocation and phosphorylation of the NF-?B subunit p65. PRV-induced persistent activation of NF-?B does not result in expression of negative feedback loop genes, like the gene for I?B? or A20, and does not trigger expression of prototypical proinflammatory genes, like the gene for tumor necrosis factor alpha (TNF-?) or interleukin-6 (IL-6). In addition, PRV infection inhibits TNF-?-induced canonical NF-?B activation. Hence, PRV infection triggers persistent NF-?B activation in an unorthodox way and dramatically modulates the NF-?B signaling axis, preventing typical proinflammatory gene expression and the responsiveness of cells to canonical NF-?B signaling, which may aid the virus in modulating early proinflammatory responses in the infected host.IMPORTANCE The NF-?B transcription factor is activated via different key inflammatory pathways and typically results in the fast expression of several proinflammatory genes as well as negative feedback loop genes to prevent excessive inflammation. In the current report, we describe that infection of cells with the porcine alphaherpesvirus pseudorabies virus (PRV) triggers a gradual and persistent aberrant activation of NF-?B, which does not result in expression of hallmark proinflammatory or negative feedback loop genes. In addition, although PRV-induced NF-?B activation shares some mechanistic features with canonical NF-?B activation, it also shows remarkable differences; e.g., it is largely independent of the canonical I?B kinase (IKK) and even renders infected cells resistant to canonical NF-?B activation by the inflammatory cytokine TNF-?. Aberrant PRV-induced NF-?B activation may therefore paradoxically serve as a viral immune evasion strategy and may represent an important tool to unravel currently unknown mechanisms and consequences of NF-?B activation.

SUBMITTER: Romero N

PROVIDER: S-EPMC7199412 | biostudies-literature | 2020 May

REPOSITORIES: biostudies-literature

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Pseudorabies Virus Infection of Epithelial Cells Leads to Persistent but Aberrant Activation of the NF-κB Pathway, Inhibiting Hallmark NF-κB-Induced Proinflammatory Gene Expression.

Romero Nicolás N Van Waesberghe Cliff C Favoreel Herman W HW

Journal of virology 20200504 10

The nuclear factor kappa B (NF-κB) is a potent transcription factor, activation of which typically results in robust proinflammatory signaling and triggering of fast negative feedback modulators to avoid excessive inflammatory responses. Here, we report that infection of epithelial cells, including primary porcine respiratory epithelial cells, with the porcine alphaherpesvirus pseudorabies virus (PRV) results in the gradual and persistent activation of NF-κB, illustrated by proteasome-dependent ...[more]

PMID: 32132236

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Project description:The nuclear factor kappa B (NF-κB) pathway is known to integrate signaling associated with very diverse intra- and extracellular stressors, including virus infections, and triggers a powerful (proinflammatory) response through the expression of NF-κB-regulated genes. Typically, the NF-κB pathway collects and transduces threatening signals at the cell surface or in the cytoplasm leading to nuclear import of activated NF-κB transcription factors. In the current work, we demonstrate that the swine alphaherpesvirus pseudorabies virus (PRV) induces a peculiar mode of NF-κB activation known as "inside-out" NF-κB activation. We show that PRV triggers the DNA damage response (DDR) and that this DDR response drives NF-κB activation since inhibition of the nuclear ataxia telangiectasia-mutated (ATM) kinase, a chief controller of DDR, abolished PRV-induced NF-κB activation. Initiation of the DDR-NF-κB signaling axis requires viral protein synthesis but occurs before active viral genome replication. In addition, the initiation of the DDR-NF-κB signaling axis is followed by a virus-induced complete shutoff of NF-κB-dependent gene expression that depends on viral DNA replication. In summary, the results presented in this study reveal that PRV infection triggers a noncanonical DDR-NF-κB activation signaling axis and that the virus actively inhibits the (potentially antiviral) consequences of this pathway, by inhibiting NF-κB-dependent gene expression. IMPORTANCE The NF-κB signaling pathway plays a critical role in coordination of innate immune responses that are of vital importance in the control of infections. The current report generates new insights into the interaction of the alphaherpesvirus pseudorabies virus (PRV) with the NF-κB pathway, as they reveal that (i) PRV infection leads to NF-κB activation via a peculiar "inside-out" nucleus-to-cytoplasm signal that is triggered via the DNA damage response (DDR), (ii) the DDR-NF-κB signaling axis requires expression of viral proteins but is initiated before active PRV replication, and (iii) late viral factor(s) allow PRV to actively and efficiently inhibit NF-κB-dependent (proinflammatory) gene expression. These data suggest that activation of the DDR-NF-κB during PRV infection is host driven and that its potential antiviral consequences are actively inhibited by the virus.

Project description:Intestinal barrier function defects and dysregulation of intestinal immune responses are two key contributory factors in the pathogenesis of ulcerative colitis (UC). Phenazine biosynthesis-like domain-containing protein (PBLD) was recently identified as a tumor suppressor in gastric cancer, hepatocellular carcinoma, and breast cancer; however, its role in UC remains unclear. Therefore, we analyzed colonic tissue samples from patients with UC and constructed specific intestinal epithelial PBLD-deficient (PBLDIEC-/-) mice to investigate the role of this protein in UC pathogenesis. We found that epithelial PBLD was decreased in patients with UC and was correlated with levels of tight junction (TJ) and inflammatory proteins. PBLDIEC-/- mice were more susceptible to dextran sulfate sodium (DSS)- and 2,4,6-trinitrobenzene sulfonic acid-induced colitis compared with wild-type (WT) mice. In DSS-induced colitis, PBLDIEC-/- mice had impaired intestinal barrier function and greater immune cell infiltration in colonic tissue than WT mice. Furthermore, TJ proteins were markedly reduced in PBLDIEC-/- mice compared with WT mice with colitis. Nuclear factor (NF)-κB activation was markedly elevated and resulted in higher expression levels of downstream effectors (C-C motif chemokine ligand 20, interleukin [IL]-1β, IL-6, and tumor necrosis factor [TNF]-α) in colonic epithelial cells isolated from PBLDIEC-/- mice than WT mice with colitis. PBLD overexpression in intestinal epithelial cells (IECs) consistently inhibited TNF-α/interferon-γ-induced intestinal barrier disruption and TNF-α-induced inflammatory responses via the suppression of NF-κB. In addition, IKK inhibition (IKK-16) rescued excessive inflammatory responses induced by TNF-α in PBLD knockdown FHC cells. Co-immunoprecipitation assays showed that PBLD may interact with IKKα and IKKβ, thus inhibiting NF-κB signaling, decreasing inflammatory mediator production, attenuating colonic inflammation, and improving intestinal barrier function. Modulating PBLD expression may provide a novel approach for treatment in patients with UC.

Dataset Information

Pseudorabies Virus Infection of Epithelial Cells Leads to Persistent but Aberrant Activation of the NF-?B Pathway, Inhibiting Hallmark NF-?B-Induced Proinflammatory Gene Expression.

Publications

Pseudorabies Virus Infection of Epithelial Cells Leads to Persistent but Aberrant Activation of the NF-κB Pathway, Inhibiting Hallmark NF-κB-Induced Proinflammatory Gene Expression.

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