Threonine Phosphorylation of STAT1 Safeguards Gut Epithelial Integrity and Restricts Interferon-mediated Cytotoxicity [RNA-seq]

Uncontrolled inflammation drives tissue damage, highlighting the need for tightly regulated immune responses and tissue integrity, particularly in barrier tissues like the intestine. To maintain this exquisite balance, intestinal epithelial cells (IECs) employ molecular circuits that preserve tissue integrity following inflammation. STAT1 is traditionally viewed as a pro-inflammatory driver in the intestine, acting as a central signaling mediator downstream of interferons (IFN). Here, we identify threonine 748 (Thr748) phosphorylation of Stat1 as an evolutionarily conserved adaptation that reciprocally regulates IEC integrity and IFN responsiveness. Mice expressing a phospho-deficient T748A Stat1 mutant exhibit severe pathology similar to Stat1 deficient littermates, underscoring Thr748’s critical role in Stat1-driven protection following intestinal inflammation. Bone marrow transfer experiments further demonstrate that this protective effect is non-hematopoietic. Integrated genomic and transcriptomic analyses reveal that Thr748 phosphorylation modulates Stat1 DNA binding, directly activating the Itgb4 promoter and enhancing integrin β4 expression in IECs following inflamamtion. In vitro intestinal organoid models, combined with gain- and loss-of-function experiments, show that Stat1 promotes integrin β4 expression via Thr748 phosphorylation following damage, boosting epithelial resilience independently of IFN-induced Tyrosine 701 (Tyr701) phosphorylation. In contrast, IFN stimulation triggers Tyr701 phosphorylation of Stat1, upregulating Zbp1—a sensor of cytotoxic damage-associated nucleic acids—while suppressing integrin β4, leading to epithelial cytotoxicity, which is mitigated by Thr748 phosphorylation. Our findings uncover a modular architecture of Stat1 signaling that enables epithelial adaptation to damage, with Thr748 phosphorylation acting as a rheostat to preserve tissue integrity while restricting IFN-mediated cytotoxicity.