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Ubiquitin-specific protease 14 regulates LPS-induced inflammation by increasing ERK1/2 phosphorylation and NF-κB
Ningning Liu1, Tianyu Kong2, Xiaohua Chen2
1Guangzhou Institute of Cardiovascular Disease, The Second Affiliated Hospital, Guangzhou Medical University, Guangzhou, 510260, Guangdong, People's Republic of China.
Abstract:
Persistent activation of nuclear factor B (NF-κB) is very important in the modulation of macrophages cellular response to microbial infections. The deubiquitinase USP14, which is critical for ubiquitin-mediated proteasomal degradation of proteins, is known to be involved in cancer, neurological diseases, and aging. However, the mechanism by which USP14 regulates inflammation remains unclear. Here, we demonstrated that decreasing the deubiquitinase activity of USP14 resulted in reduced lipopolysaccharides (LPS)-mediated tumor necrosis factor-α (TNF-α) and interleukin (IL)-6 release in THP-1 and RAW264.7 cells. Meanwhile, USP14 knockdown by siRNA showed the same effects, with no cytotoxicity in THP-1 cells. Moreover, inhibiting the deubiquitinase activity of USP14 or USP14 knockdown resulted in decreased ERK1/2 and IκBα phosphorylation, increased amounts of the NF-κB inhibitor IκBα, and reduced NF-κB p65 transport from the cytoplasm into nucleus. These findings suggested that USP14 induces NF-κB activity and ERK1/2 phosphorylation triggered by microbial infection.
Insights
USP14 deubiquitinase activity promotes inflammation by activating nuclear factor B (NF-κB) and ERK1/2 pathways during microbial infections. Inhibiting USP14 reduces inflammatory cytokine release and NF-κB activation.
Area of Science:
- Immunology
- Molecular Biology
- Cellular Biology
Background:
- Persistent nuclear factor B (NF-κB) activation modulates macrophage responses to microbial infections.
- The deubiquitinase USP14 is implicated in various diseases but its role in inflammation is unclear.
Purpose of the Study:
- To elucidate the mechanism by which USP14 regulates inflammation.
- To investigate USP14's role in NF-κB and ERK1/2 signaling pathways during microbial infection.
Main Methods:
- Utilized THP-1 and RAW264.7 cell lines.
- Assessed inflammatory cytokine release (TNF-α, IL-6) following lipopolysaccharides (LPS) stimulation.
- Investigated USP14 deubiquitinase activity inhibition and USP14 knockdown via siRNA.
- Analyzed phosphorylation of ERK1/2 and IκBα, IκBα protein levels, and NF-κB p65 nuclear translocation.
Main Results:
- Decreased USP14 deubiquitinase activity or USP14 knockdown reduced LPS-induced TNF-α and IL-6 release.
- USP14 inhibition or knockdown led to decreased ERK1/2 and IκBα phosphorylation.
- USP14 inhibition or knockdown increased IκBα protein levels and reduced NF-κB p65 nuclear translocation.
- No cytotoxicity was observed in THP-1 cells upon USP14 knockdown.
Conclusions:
- USP14 deubiquitinase activity is crucial for inducing NF-κB activity and ERK1/2 phosphorylation in response to microbial infection.
- USP14 inhibition represents a potential therapeutic strategy for inflammatory conditions triggered by microbial infections.