Fig. 6.

Effects of USP15 overexpression or inhibition on TGF-β-induced SMAD3 phosphorylation in vitro

(A, B) Human synovial fibroblasts were left non-transfected, or transfected with control or USP15 siRNA, and then stimulated with TGF-β. (A) Representative USP15, phospho-SMAD3 and total SMAD3 western blot. (B) β-actin-normalized USP15, total SMAD3 and phospho-SMAD3 quantification in two different experiments. P-values were calculated using unpaired Student’s t-tests. *P < 0.01, ***P < 0.0001. (C, D) Human embryonic kidney (HEK293) cells were transfected with a control or USP15-encoding plasmid, and stimulated in duplicate wells with TGF-β. (C) Representative USP15, phospho-SMAD3 and total SMAD3 western blot. (D) β-actin-normalized USP15, total SMAD3 and phospho-SMAD3 quantification in three different experiments. P-values were calculated using unpaired Student’s t-tests. **P < 0.005. USP: ubiquitin-specific peptidase.