NF-κB and MAPK signaling pathways regulate the IL6 mRNA stability under TLR4 by regulating the expression and degradation of Arid5a

Abstract

Abstract AT-rich interactive domain (ARID) 5a controls the IL-6 mRNA stability by binding to its 3′UTR region and preventing it from degradation by Regnase-1. This mechanism was shown to contribute to the elevation of IL-6 levels, which causes the development of autoimmune diseases. However, almost nothing is known about the regulatory mechanisms of Arid5a mRNA and protein expression. In the present study, we have investigated the regulatory mechanisms of Arid5a at transcriptional, post-transcriptional and post-translational levels under TLR4 signaling. We found that in response to LPS stimulation NF-κB binds to the promoter region of Arid5a and induce its gene expression. After expression of Arid5a mRNA, MKP-1 signaling induces AUF-1 to translocate from the nucleus to the cytoplasm where it binds to the 3′UTR region of Arid5a and resulting in its destabilization. Inhibition of MKP-1 and AUF-1 results in the stabilization of Arid5a mRNA, which leads to higher expression of IL6, suggesting that this pathway has a significant role in regulating IL6 mRNA through Arid5a. We also show that during the late phase of LPS stimulation, p38 MAPK phosphorylates the Arid5a protein at Ser 253, 433 and 458 positions that lead to its ubiquitination at lysine 80 and 93 positions resulting in degradation. Inhibition of Arid5a phosphorylation and degradation causes the over-production IL6 mRNA further supports the importance of Arid5a in the regulation of IL6. Our data demonstrate that LPS signaling controls IL6 mRNA stability; therefore, its regulation through up-regulation of Arid5a by NF-κB at the early phase, and down-regulation of Arid5a at the mRNA and protein level by MKP-1-mediated AUF1 and P38 MAPK signaling, respectively at the later phase.