RORγt serine 182 tightly regulates T cell heterogeneity to maintain mucosal homeostasis and restrict tissue inflammation

ABSTRACT Intestine homeostasis is maintained by the delicate balance of Th17 effector cells and Treg cells. Dysregulation of these cell populations contributes to inflammation, tissue damage, and chronic conditions. RORγt is essential for the differentiation of Th17 and a subset of Treg (RORγt + Treg) cells involved in intestinal inflammation. RORγt belongs to the nuclear receptor family of transcription factors with hinge regions that are highly flexible for co-activator/co-repressor interactions. Serine 182 at the hinge region of RORγt is phosphorylated. This study aims to uncover how S182 on RORγt contributes to mucosal homeostasis and diseases. We used CRISRP technology to generate a phosphor-null knock-in mutant mouse line (RORγt S182A ) to assess its role in intestine physiology. scRNA-seq was performed on WT and RORγt S182A cohoused littermates to evaluate colonic T cell heterogeneity under steady state and colitis settings. Single-cell transcriptomics revealed that RORγt S182 maintains colonic T cell heterogeneity under steady state, without interfering T cell development and differentiation. In inflamed tissues, RORγt S182 simultaneously restricts IL-1β-mediated Th17 activities and promotes anti-inflammatory cytokine IL-10 production in LT-like Treg cells. Phospho-null RORγt S182A knock-in mice challenged with DSS induced colitis and EAE experienced delayed recovery and exacerbated pathology. The double switch role of RORγt S182 is critical in resolving T cell-mediated inflammation and provides a potential therapeutic target to combat autoimmune diseases.