Figure 6.

BMP signaling agonists enhance the efficacy of BMPs. A, BRE-Luc cells were treated with DMSO (black) or sb4 (gray) at a constant concentration of 10 μm in the presence of increasing concentrations of rhBMP4 (0.4, 1, 10, and 40 ng/ml) for 18 h. A representative experiment was conducted in triplicate, reported as -fold change over DMSO. B, Western blotting of protein lysates from BRE-luc cells treated for 1 h with rhBMP4 (2 ng/ml) followed by fresh media containing either vehicle (DMSO) or 1 μm sb4. Samples were harvested at 0, 5, 15, 30, 45, and 60 min after the addition of sb4. A representative Western blot for p-SMAD-1/5/9 from three independent biological experiments is shown. C, ratio of p-SMAD-1/5/9 to total SMAD-1 as quantified by densitometry is shown for experiments outlined in C. Ratio of p-SMAD-1/5/9 to total-SMAD-1 over time was compared by unpaired multiple t tests. *, p = 0.02. Note the increased stability of p-SMAD-1/5/9 in sb4-treated cells. Error bars, S.E.