Signal Processing in the TGF-β Superfamily Ligand-Receptor Network
Figure 7
Time courses of the numbers of active receptor complexes when TGF-β concentration (in red) is increased, repeatedly in steps or continuously. Left panels (A, C, and E) show the responses to step increases as shown in inset in (A). Right panels (B, D, and F) show the response to a continuous increase as shown in inset in (B). There is also a second ligand present (here BMP7, in blue) whose concentration is kept constant. The two ligands induce the formation of two ligand-receptor complexes, CBMP7 (blue) and CTGF-β (red), that share the type I receptor Alk2. The green line on the left panels shows the total number of active receptor complexes (CBMP7 + CTGF−β). As in Figure 6, a key control quantity of the qualitative behavior of the system is the CIR. The parameter values for (A–F) are the same as in Figure 6A–6F, respectively.