Figure 1.

Schematic of the Smad-dependent TGF-β signalling pathway upon stimulation with TGF-β and BMP. Arrows denote reaction steps, corresponding to the equations in table 2. Synthesis and degradation reactions are provided in the table (inset) with the notation for the different molecular species of table 1. Expression of Smad7 is under the control of a single gene, activated by pSmad1–Smad4 and/or pSmad2–Smad4 nuclear complexes. Smad7 ligand–receptor complex targeting and expression patterns are cell-dependent with all potential combinations illustrated in the inset. Mixed R-Smad complex formation in the HaCaT and C2C12 cases are not explicitly shown here; see text and the caption of table 2 for details of its implementation. (Online version in colour.)