ATF3 plays a key role in Kdo2-lipid A-induced TLR4-dependent gene expression via NF-κB activation.

Sangdun Choi,Dong-Gun Kim,Hyuk-Kwon Kwon,Joo-Young Kim,Niels Olsen Saraiva Câmara,Yong-Min Choi,Eun-Young Kim,Hye Young Shin,Dong-Kwon Rhee,You-Sun Kim

doi:10.1371/journal.pone.0014181

Sangdun Choi, Dong-Gun Kim + Show 8 more

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https://doi.org/10.1371/journal.pone.0014181

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Journal: PloS one	Publication Date: Dec 2, 2010
Citations: 60	License type: CC BY 4.0

Affiliation: Ajou University, Sungkyunkwan University

Abstract

BackgroundActivating transcription factor 3 (ATF3) is a negative regulator of proinflammatory cytokine expression in macrophages, and ATF3 deficient mice are more susceptible to endotoxic shock. This study addresses the role of ATF3 in the Kdo2-Lipid A-induced Toll-like receptor 4 (TLR4) signaling pathway in mouse embryonic fibroblasts (MEF). Kdo2-Lipid A upregulates ATF3 expression in wild type MEF cells and induces both nuclear factor kappa B (NF-κB) and c-Jun N-terminal kinase (JNK) activation via the TLR4 signaling pathway, while neither of these pathways is activated in ATF3-/- MEF cells. Interestingly, in contrast to Kdo2-Lipid A, the activation of both NF-κB and JNK by TNF-α was normal in ATF3-/- MEF cells.Methodology/Principal FindingsWe found that several genes were dramatically upregulated in ATF3+/+ MEF cells in response to Kdo2-Lipid A treatment, while little difference was observed in the ATF3-/- MEF cells. However, we also found that the signal intensities of IκBζ in ATF3-/- MEF cells were substantially higher than those in wild type MEF cells upon microarray analyses, and upregulated IκBζ expression was detected in the cytosol fraction.Conclusions/SignificanceOur findings indicate that ATF3 deficiency affects Kdo2-Lipid A-induced TLR4 signaling pathways in MEF cells, that it may upregulate IκBζ expression and that the high levels of IκBζ expression in ATF3-/- cells disrupts Kdo2-Lipid A-mediated signaling pathways.

Highlights

Toll-like receptors (TLRs) are membrane-bound patternrecognition receptors (PRRs) that sense a variety of microbialspecific motifs to trigger an innate immune response [1,2]
We investigated the function of Activating transcription factor 3 (ATF3) in the Kdo2-Lipid A-mediated Toll-like receptor 4 (TLR4) signaling pathways in mouse embryonic fibroblast (MEF) cells
Early degradation of IkBa was abrogated in ATF3-/- mouse embryonic fibroblasts (MEF) cells that were treated with Kdo2-Lipid A, indicating that ATF3 is required for TLR4-dependent nuclear factor kappa B (NF-kB) activation (Fig. 1A)

Summary

Introduction

Toll-like receptors (TLRs) are membrane-bound patternrecognition receptors (PRRs) that sense a variety of microbialspecific motifs to trigger an innate immune response [1,2]. Once a LRR motif is engaged by PAMPs, TLRs initiate specific signaling pathways via the recruitment of TIR domaincontaining adaptor molecules such as myeloid differentiation primary response protein 88 (MyD88) or TIR domain-containing adaptor inducing IFN-b (TRIF) [7,8]. Upon stimulation with LPS, TLR4 recruits MAL and TRIF through its TIR domain and initiates a series of signaling cascades that result in the activation of nuclear factor kappa B (NF-kB) and mitogenactivated protein kinases (MAPKs) [14,15]. This study addresses the role of ATF3 in the Kdo2-Lipid A-induced Toll-like receptor 4 (TLR4) signaling pathway in mouse embryonic fibroblasts (MEF). Kdo2-Lipid A upregulates ATF3 expression in wild type MEF cells and induces both nuclear factor kappa B (NF-kB) and c-Jun N-terminal kinase (JNK) activation via the TLR4 signaling pathway, while neither of these pathways is activated in ATF3-/- MEF cells. In contrast to Kdo2-Lipid A, the activation of both NF-kB and JNK by TNF-a was normal in ATF3-/- MEF cells

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