Cytoskeletal protein Flightless I differentially affects TGF-beta isoform expression in both in vitro and in vivo wound models

Flightless I (Flii) is a multifunctional cytoskeletal protein and a negative regulator of wound healing. It affects processes including cellular adhesion, migration and proliferation. These cell processes are also affected by the pro-fibrotic growth factor TGF-β1, which contributes to increased scar formation. Using Flii heterozygous (Flii+/-), wild-type (WT) and Flii overexpressing (FliiTg/+) mice in an incisional model of wound healing, and primary fibroblasts in in vitro models of wound healing, we examined whether changes in Flii gene expression could affect specific TGF-β isoform expression and signalling. TGF-β1 levels were increased in Flii overexpressing wounds while TGF-β3 was elevated in Flii-deficient wounds. Wounding fibroblasts in vitro led to a translocation of both Flii and TGF-β isoforms from the cytoplasm into the nucleus. Flii not only co-localised with all TGF-β isoforms, but it also associated with the activating protein-1 (AP-1) subunits c-fos and c-jun as well as nuclear Akt. Additionally, siRNA knockdown of Flii gene expression decreased TGF-β1 and Smad 3 and led to an elevation of inhibitory Smad 7, indicating a potential mechanistic role for Flii in TGF-β signalling. We conclude that Flii effects on wound healing could potentially be via its modulatory effects on the TGF-β signalling pathway