Claudin-2 protects from enteropathogenic E. coli-infection and colitis by promoting crypt fetalization via β1-integrin/FAK/YAP signaling

Abstract Citrobacter rodentium ( Cra ) infection, a murine model of enteropathogenic Escherichia coli (EPEC) infection, induces crypt proliferation that potentially promotes mucosal healing and pathogen clearance, yet the underlying molecular mechanisms remain poorly understood. Cra infection upregulates claudin-2 (CLDN2), which has been proposed to facilitate pathogen clearance by enhancing Na⁺ flux and diarrhea. However, CLDN2 is dispensable for intestinal Na⁺ homeostasis. Here, we investigate whether Cra -induced CLDN2 protects against Cra -infection and colitis by regulating crypt proliferation. Using mice with intestinal epithelial-specific CLDN2 overexpression or deletion ( Cldn2 KO), we evaluate the role of CLDN2 in Cra colonization, inflammation, and epithelial regeneration. Organoid cultures assess epithelial-intrinsic mechanisms, while co-immunoprecipitation identifies CLDN2-associated signaling complexes. CLDN2 overexpression protects against Cra colonization and colitis, whereas Cldn2 KO mice exhibit increased bacterial burden, exacerbated inflammation, and impaired crypt proliferation. Mechanistically, CLDN2 promotes crypt fetal-like reprogramming (fetalization), which is suppressed in Cldn2 KO mice. Inhibiting EGFR-activation abolishes CLDN2 induction and phenocopies Cldn2 KO phenotype. Furthermore, CLDN2 promotes FAK and YAP activation by stabilizing the β1-integrin-FAK complex, thereby driving crypt fetalization. Collectively, these findings identify CLDN2 as a critical regulator of mucosal defense and epithelial regeneration through activation of the β1-integrin-FAK-YAP signaling axis, beyond its classical role in paracellular ion permeability.