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

• Main Authors: Eun-Young Kim, Hye Young Shin, Joo-Young Kim, Dong-Gun Kim, Yong-Min Choi, Hyuk-Kwon Kwon, Dong-Kwon Rhee, You-Sun Kim, Sangdun Choi
• Format: Article
• Language: English
• Published: Public Library of Science (PLoS) 2010-01-01
• Series: PLoS ONE
• Online Access: http://europepmc.org/articles/PMC2996292?pdf=render

BACKGROUND: Activating 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 Kdo(2)-Lipid A-induced Toll-like receptor 4 (TLR4) signaling pathway in mouse embryonic fibroblasts (MEF). Kdo(2)-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 Kdo(2)-Lipid A, the activation of both NF-κB and JNK by TNF-α was normal in ATF3-/- MEF cells. METHODOLOGY/PRINCIPAL FINDINGS: We found that several genes were dramatically upregulated in ATF3+/+ MEF cells in response to Kdo(2)-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/SIGNIFICANCE: Our findings indicate that ATF3 deficiency affects Kdo(2)-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 Kdo(2)-Lipid A-mediated signaling pathways.