Neuregulin-1β treatment induces phosphorylation of GSK-3β in human cardiac fibroblasts. A, Western blot analysis of protein lysates of NHCV fibroblasts treated for 30 min with 30 ng/mL of NRG-1β. Bands shown are 46 kDa and were detected using anti-rabbit GSK-3β and after re-probing with pan GSK-3β. Experimental conditions included untreated control cells, denoted by a “C”, and cells treated with NRG-1β (N), 1 ng/mL TGF-β (T), or both NRG-1β and TGF-1β (NT). Representative blots are shown. B, Western blots of protein lysates of NHCV fibroblasts probed first with pGSK-3β and then with pan GSK-3β (as a loading control). Treatments shown (in triplicate) include untreated control cells, and cells treated with the PI3K inhibitor LY294002 (LY), 30 ng/mL of NRG-1β (NRG), or both LY and NRG. C and D, Graphical representations of densitometry analysis results for the differentially expressed proteins shown in A and B, respectively (*p < 0.05 and ***p < 0.001, respectively for NRG-1β-treated cells, when compared to appropriate control treatments).