Growth Factor FGF2 Cooperates with Interleukin-17 to Repair Intestinal Epithelial Damage

• FGF2 and IL-17 signaling are critical for gut homeostasis during colitis
• Microbiota-driven TGFβ1 controls FGF2 production in Treg cells during colitis
• FGF2 cooperates with IL-17 to promote repair of damaged intestinal epithelium
• Act1 mediates the cooperation of FGF2 and IL-17 signaling in gut

SummaryThe intestinal epithelial barrier plays a critical role in the mucosal immunity. However, it remains largely unknown how the epithelial barrier is maintained after damage. Here we show that growth factor FGF2 synergized with interleukin-17 (IL-17) to induce genes for repairing of damaged epithelium. FGF2 or IL-17 deficiency resulted in impaired epithelial proliferation, increased pro-inflammatory microbiota outgrowth, and consequently worse pathology in a DSS-induced colitis model. The dysregulated microbiota in the model induced transforming growth factor beta 1 (TGFβ1) expression, which in turn induced FGF2 expression mainly in regulatory T cells. Act1, an essential adaptor in IL-17 signaling, suppressed FGF2-induced ERK activation through binding to adaptor molecule GRB2 to interfere with its association with guanine nucleotide exchange factor SOS1. Act1 preferentially bound to IL-17 receptor complex, releasing its suppressive effect on FGF2 signaling. Thus, microbiota-driven FGF2 and IL-17 cooperate to repair the damaged intestinal epithelium through Act1-mediated direct signaling cross-talk.

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