FIGURE 11.

Model of BMP/GDF growth factor complexes bound to fibrillin-containing microfibril networks. A, in this model of microfibrils, fibrillin-1 molecules are staggered with N-terminal halves on the outside of the microfibril and C-terminal halves forming the core of the microfibril (22). Binding sites for BMP/GDF growth factor complexes can be mapped to the shaded fibrillin-1 domains shown in the schematic representation. B, fibrillin microfibril networks with associated LTBPs sequester latent complexes of TGF-β (4). In addition, cells secrete BMPs as growth factor complexes (white butterflies), which are then targeted by prodomain/fibrillin interactions to specific positions on microfibrils. Cells receiving positional information through integrins or other receptors that interact with microfibril components determine whether to send or receive growth factor signals. Through this exchange of positional and signaling information, cells may either utilize growth factors immediately or store them on the microfibrils for later use. LAP, latency-associated peptide.