Fig. 6

Inhibition of ligand-induced signal transduction. a Dose-dependent inhibition of ALP gene expression induced by BMP-2 (black squares), GDF-5 (red diamonds), or GDF-5 R57A (blue asterisks) by increasing concentrations of the BMPR-IA-neutralizing Fab antibody AbD1564. The background absorption signal (without ligand, dotted line) of 0.36 ± 0.04 at 405 nm was not subtracted to highlight ALP induction mediated by endogenously expressed BMP ligands. Half-maximal inhibitory antibody concentrations (IC₅₀) for ALP activities induced by the different ligand proteins are indicated. A biological duplicate of this experiment is shown in Additional file 6: Figure S5. b Ligand-induced SMAD-1 phosphorylation in C2C12 cells. The cells were serum-starved and exposed to the indicated ligands for 1 h. Equal amounts of whole cell lysates were separated by SDS-PAGE and western blots were performed using an anti-SMAD-1 or anti-pSMAD-1 antibody