Regulation of inflammatory responses by dynamic subcellular localization of RNA-binding protein Arid5a

Significance Immune cell activation is accompanied by dynamic changes in expression of genes related to inflammation. Concomitantly, immune reactions are tightly controlled to prevent harmful pathologies due to sustained inflammation. Gene expression is controlled at multiple checkpoints. Among these, the post-transcriptional regulation of the balance between Arid5a and Regnase-1 is important for the induction of inflammation. Our findings provide important insight into the role of the regulation of nucleocytoplasmic localization of Arid5a in the development of inflammation through the induction of a change in the ratio of Arid5a to Regnase-1.
Adenine-thymine (AT)-rich interactive domain 5a (Arid5a) is an RNA-binding protein found in the cytoplasm and nucleus of normally growing cells. Although Arid5a is known to play an important role in immune regulation, whether and how Arid5a subcellular localization impacts immune regulation has remained unclear. In this study, we generated Arid5a transgenic (TG) mice to address this question. While ectopic Arid5a overexpression did not affect expression of inflammatory cytokines under unstimulated conditions, significantly higher levels of inflammatory cytokines, such as IL-6, were produced in response to lipopolysaccharide (LPS) stimulation. Consistent with this, TG mice were more sensitive to LPS treatment than wild-type mice. We also found that Arid5a is imported into the nucleus via a classical importin-α/β1–mediated pathway. On stimulation, nuclear Arid5a levels were decreased, while there was a concomitant increase in cytoplasmic Arid5a. Arid5a is associated with up-frameshift protein 1, and its nuclear export is regulated by a nuclear export receptor, chromosomal region maintenance 1. Taken together, these data indicate that Arid5a is a dynamic protein that translocates to the cytoplasm from the nucleus so as to properly exert its dual function in mRNA stabilization and transcriptional regulation during inflammatory conditions.