Chloride intracellular channel 4 (CLIC4) expression is transcriptionally regulated by crosstalk of the TGF-beta, Wnt and Hedgehog signalling pathways

Chloride intracellular channel 4 (CLIC4) is a recently discovered driver of fibroblast activation in Scleroderma (SSc) and cancer-associated fibroblasts. CLIC4 expression and activity are regulated by TGF-{beta} signalling through the SMAD3 transcription factor. In view of the aberrant activation of canonical Wnt and Hedgehog (Hh) signalling in fibrosis, we investigated their role in CLIC4 upregulation. Here, we show Wnt3a/{beta}-catenin and Smoothened/GLI signalling cooperate with SMAD3 to regulate CLIC4 expression in normal dermal fibroblasts, and that inhibition of SMAD3 expression or activity abolishes Wnt and Hh-dependent CLIC4 induction. We further show that expression of the profibrotic marker -smooth muscle actin strongly correlates with CLIC4 expression in dermal fibroblasts. Our data highlight novel mechanisms that regulate CLIC4 expression that present targetable pathways to prevent fibroblast activation in SSc and other fibrotic conditions.