Western blot analysis after immunoprecipitation by anti-ErbB2 magnetic beads to demonstrate the interaction between ErbB2 and Smad7 in cardiac fibroblasts treated with TGF-β1 (10 ng/mL) or amphiregulin (ARG, 1 ng/mL). Upper panel: Immunoprecipitated (IP) ErbB2 fractions from cell lysates (upper, first band), show Smad7 expression (upper, second band), demonstrating that Smad7 interacts with ErbB2 in unstimulated and stimulated cardiac fibroblasts. Validation of the ErbB2 IP technique is shown by both the absence of ErbB2 expression in the IgG-immunoprecipitated fraction, as well as the absence of ErbB2 protein in the whole-cell lysate (WCL) of ErbB2 pull-down cells (lower panel, first band). GAPDH levels in the WCL were used as loading controls. Representative blots are shown (n = 3).