Erk activity is integral for TGF-β signaling and inducing growth in fibroblasts.

<p>(<b>A</b>) Fold change in expression levels of two smad regulated genes, PAI-1 and smad7, relative to untreated controls levels are shown from AKR-2B fibroblasts treated for 10 minutes with or without TGF-β (2 ng/ml), with or without U0126 (10 µM) for 3 h. The mean values (±SEM) of six independent experiments are shown with statistical evaluation indicating differences between groups as (NS) not significant, (*) P<0.05, (***) P<0.001. (<b>B</b>) Thymidine incorporation was determined in serum deprived NIH 3T3 cells treated with TGF-β (5 ng/ml) with or without infection with Ad-dnPAK2 or Ad-EGFP (MOI = 125∶1) or U0126 (10 µM) prior to treatment. The effect of treatment is expressed as a fold change in thymidine incorporation relative to untreated cells (control = 1). The mean (±SEM) of triplicate assays is shown with statistical evaluation indicating differences between groups as previously describe. (<b>C</b>) Schematic representation of TGF-β signaling pathways in fibroblasts, indicating the proposed interactions and their subcellular locations. Arrows represent a functional link between the subsequent proteins, not necessarily a direct interaction.