ABSTRACT
Retinoid-related orphan receptor (RAR) gamma (RORγt)-expressing regulatory T cells (RORγt+ Tregs) play pivotal roles in preventing T cell hyperactivation and maintaining tissue homeostasis, in part by secreting the anti-inflammation cytokine interleukin-10 (IL-10). Here, we report that hypoxia-induced factor 1α (HIF1α) is the master transcription factor for Il10 in RORγt+ Tregs. This critical anti-inflammatory pathway is negatively regulated by an RNA binding protein DEAD box helicase 5 (DDX5). As a transcriptional corepressor, DDX5 restricts the expression of HIF1α and its downstream target gene Il10 in RORγt+ Tregs. T cell-specific Ddx5 knockout (DDX5ΔT) mice have augmented RORγt+ Treg suppressor activities and are better protected from intestinal inflammation. Genetic ablation or pharmacologic inhibition of HIF1α restores enteropathy susceptibility in DDX5ΔT mice. The DDX5-HIF1α-IL-10 pathway is conserved in mice and humans. These findings reveal potential therapeutic targets for intestinal inflammatory diseases.
Subject(s)
Interleukin-10 , Nuclear Receptor Subfamily 1, Group F, Member 3 , Humans , Mice , Animals , Interleukin-10/genetics , Nuclear Receptor Subfamily 1, Group F, Member 3/genetics , Nuclear Receptor Subfamily 1, Group F, Member 3/metabolism , Gene Expression Regulation , Transcription Factors/metabolism , RNA-Binding Proteins/genetics , RNA-Binding Proteins/metabolism , DEAD-box RNA Helicases/genetics , DEAD-box RNA Helicases/metabolism , Protein BindingABSTRACT
RAR-related orphan receptor-γ (RORγt) is an essential transcription factor for thymic T cell development, secondary lymphoid tissue organogenesis, and peripheral immune cell differentiation. Serine 182 phosphorylation is a major post-translational modification (PTM) on RORγt. However, the in vivo contribution of this PTM in health and disease settings is unclear. We report that this PTM is not involved in thymic T cell development and effector T cell differentiation. Instead, it is a critical regulator of inflammation downstream of IL-1ß signaling and extracellular signal regulated kinases (ERKs) activation. ERKs phosphorylation of serine 182 on RORγt serves to simultaneously restrict Th17 hyperactivation and promote anti-inflammatory cytokine IL-10 production in RORγt+ Treg cells. Phospho-null RORγtS182A knockin mice experience exacerbated inflammation in models of colitis and experimental autoimmune encephalomyelitis (EAE). In summary, the IL-1ß-ERK-RORγtS182 circuit protects against T cell-mediated inflammation and provides potential therapeutic targets to combat autoimmune diseases.
Subject(s)
Encephalomyelitis, Autoimmune, Experimental , Nuclear Receptor Subfamily 1, Group F, Member 3 , Animals , Cell Differentiation , Inflammation , Mice , Mice, Inbred C57BL , Nuclear Receptor Subfamily 1, Group F, Member 3/metabolism , Phosphorylation , Th17 CellsABSTRACT
Tumorigenesis in different segments of the intestinal tract involves tissue-specific oncogenic drivers. In the colon, complement component 3 (C3) activation is a major contributor to inflammation and malignancies. By contrast, tumorigenesis in the small intestine involves fatty acid-binding protein 1 (FABP1). However, little is known of the upstream mechanisms driving their expressions in different segments of the intestinal tract. Here, we report that the RNA-binding protein DDX5 binds to the mRNA transcripts of C3 and Fabp1 to augment their expressions posttranscriptionally. Knocking out DDX5 in epithelial cells protected mice from intestinal tumorigenesis and dextran sodium sulfate (DSS)-induced colitis. Identification of DDX5 as a common upstream regulator of tissue-specific oncogenic molecules provides an excellent therapeutic target for intestinal diseases.
