Induction of Pro-Fibrotic CLIC4 in Dermal Fibroblasts by TGF-ß/Wnt3a Is Mediated by GLI2 Upregulation.

ABSTRACT

Chloride intracellular channel 4 (CLIC4) is a recently discovered driver of fibroblast activation in Scleroderma (SSc) and cancer-associated fibroblasts (CAF). CLIC4 expression and activity are regulated by TGF-ß signalling through the SMAD3 transcription factor. In view of the aberrant activation of canonical Wnt-3a and Hedgehog (Hh) signalling in fibrosis, we investigated their role in CLIC4 upregulation. Here, we show that TGF-ß/SMAD3 co-operates with Wnt3a/ß-catenin and Smoothened/GLI signalling to drive CLIC4 expression in normal dermal fibroblasts, and that the inhibition of ß-catenin and GLI expression or activity abolishes TGF-ß/SMAD3-dependent CLIC4 induction. We further show that the expression of the pro-fibrotic marker α-smooth muscle actin strongly correlates with CLIC4 expression in dermal fibroblasts. Further investigations revealed that the inhibition of CLIC4 reverses morphogen-dependent fibroblast activation. Our data highlights that CLIC4 is a common downstream target of TGF-ß, Hh, and Wnt-3a through signalling crosstalk and we propose a potential therapeutic avenue using CLIC4 inhibitors.