Ubiquitin-specific protease 14 regulates LPS-induced inflammation by increasing ERK1/2 phosphorylation and NF-κB activation

Persistent activation of nuclear factor B (NF-kappa B) 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-alpha (TNF-alpha) 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 I kappa B alpha phosphorylation, increased amounts of the NF-kappa B inhibitor I kappa B alpha, and reduced NF-kappa B p65 transport from the cytoplasm into nucleus. These findings suggested that USP14 induces NF-kappa B activity and ERK1/2 phosphorylation triggered by microbial infection.