Figure 2.

Hypothetical model of collagen fibril nucleation at the plasma membrane. (1) Dimeric FN (black) binds to α5β1 integrins (green). (2) Engagement of the integrin with the cytoskeleton (red lines) causes a conformational change in FN with subsequent fibril formation. Additional receptors (orange bars) bind FN. (3) Collagen I, procollagen I (black), and collagen V (purple) engage with FN at the fibril surface to facilitate collagen fibril formation. Decorin (interlocking dimers) shown bound to procollagen. (4) Activated collagen integrins (e.g. α2β1) bind collagen and induce a conformation change that facilitates fibril formation. (5) Collagen fibril formation at the cell surface. (6) Interactions between collagen fibrils (e.g. including tenascin-X and decorin) determine fibril diameter, organization, and spacing. Parts of the schematic are adapted from Mao and Schwarzbauer [8] and Bristow et al. [66].