Figure 10.

Model for Mn²⁺ activation of α5β1 integrin and FN matrix assembly. (A) FN binding to α5β1 results in receptor clustering and unfolding of the FN molecule, exposing FN-FN binding sites required for initiation of matrix assembly. (B) A different α5β1 conformation is induced, thus allowing the formation of FN fibrils. Mn²⁺ can increase the rate of conversion from conformation A to conformation B. (C) In the absence of the synergy region of FN, conformation B is not induced and matrix assembly does not proceed. Mn²⁺ stimulation of α5β1 results in an activated receptor that can support FN assembly in the absence of the synergy site.