First Insight into the Modulation of Noncanonical NF-κB Signaling Components by Poxviruses in Established Immune-Derived Cell Lines: An In Vitro Model of Ectromelia Virus Infection.

Justyna Struzik,Matylda B Mielcarska,Małgorzata Gieryńska,Lidia Szulc-Dąbrowska,Michał Koper,Magdalena Bossowska-Nowicka

doi:10.3390/pathogens9100814

Justyna Struzik, Matylda B Mielcarska + Show 4 more

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https://doi.org/10.3390/pathogens9100814

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Abstract

Dendritic cells (DCs) and macrophages are the first line of antiviral immunity. Viral pathogens exploit these cell populations for their efficient replication and dissemination via the modulation of intracellular signaling pathways. Disruption of the noncanonical nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) signaling has frequently been observed in lymphoid cells upon infection with oncogenic viruses. However, several nononcogenic viruses have been shown to manipulate the noncanonical NF-κB signaling in different cell types. This study demonstrates the modulating effect of ectromelia virus (ECTV) on the components of the noncanonical NF-κB signaling pathway in established murine cell lines: JAWS II DCs and RAW 264.7 macrophages. ECTV affected the activation of TRAF2, cIAP1, RelB, and p100 upon cell treatment with both canonical and noncanonical NF-κB stimuli and thus impeded DNA binding by RelB and p52. ECTV also inhibited the expression of numerous genes related to the noncanonical NF-κB pathway and RelB-dependent gene expression in the cells treated with canonical and noncanonical NF-κB activators. Thus, our data strongly suggest that ECTV influenced the noncanonical NF-κB signaling components in the in vitro models. These findings provide new insights into the noncanonical NF-κB signaling components and their manipulation by poxviruses in vitro.

Highlights

Transcription factor nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) regulates genes that are involved in the various mechanisms of the innate antiviral immune response [1].The canonical NF-κB signaling pathway can be induced by numerous stimuli: (1) by the pathogen-associated molecular patterns (PAMPs) activating Toll-like receptors (TLRs) and other pattern recognition receptors (PRRs); (2) by the proinflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) [2,3]; (3) by interferon-γ (IFN-γ); and (4) by phorbol12-myristate 13-acetate (PMA) [4]
For the first time, we focused on the noncanonical NF-κB signaling components in established immune-derived cell lines that are permissive for ectromelia virus (ECTV) infection: RAW 264.7 macrophages and JAWS II Dendritic cells (DCs) [28,29]
RAW 264.7 cells are characterized by very low expression of CD40, a member of the TNF superfamily, which induces the noncanonical NF-κB signaling in macrophages [33,34]

Summary

Introduction

Transcription factor nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) regulates genes that are involved in the various mechanisms of the innate antiviral immune response [1].The canonical NF-κB signaling pathway can be induced by numerous stimuli: (1) by the pathogen-associated molecular patterns (PAMPs) activating Toll-like receptors (TLRs) and other pattern recognition receptors (PRRs); (2) by the proinflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) [2,3]; (3) by interferon-γ (IFN-γ); and (4) by phorbol12-myristate 13-acetate (PMA) [4]. The canonical NF-κB signaling pathway can be induced by numerous stimuli: (1) by the pathogen-associated molecular patterns (PAMPs) activating Toll-like receptors (TLRs) and other pattern recognition receptors (PRRs); (2) by the proinflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) [2,3]; (3) by interferon-γ (IFN-γ); and (4) by phorbol. Activated IKK, in turn, leads to the phosphorylation and proteasomal degradation of IκBα. Degradation of IκBα results in the rapid translocation of RelA (p65)/p50 and c-Rel/p50 heterodimers from the cytoplasm to the nucleus to regulate the transcription of the genes involved in innate immunity and inflammation [3]. Canonical NF-κB activators, such as lipopolysaccharide (LPS), TNF-α, IFN-γ, and PMA may induce the noncanonical NF-κB signaling pathway [6]. The activation of the noncanonical NF-κB signaling pathway is based on the stabilization of its central component, NF-κB-inducing kinase (NIK). NIK interacts with TNF receptor-associated factor 3 (TRAF3) and is continuously degraded by E3 ubiquitin ligase complex composed of cellular inhibitor of apoptosis protein 1/2

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