Figure 8. The major role of the FN synergy site is to re-enforce cell adhesion.
(A) Hydrodynamic shear force-exposed fibroblasts seeded on a FNwt-coated surface form catch-bonds that strengthen α5β1 integrin-mediated adhesions to FN and trigger phosphorylation of Y397-FAK (upper image). On FNsyn-coated surfaces, the αvβ3 integrins compensate for the absent synergy site allowing fibroblast adhesion and the reduced α5β1 binding strength leads to diminished phosphorylation of pY397-FAK (middle image). The elimination of αv-class integrins decreases cell adhesion on FNsyn-coated surfaces, reduces cell spreading and delays the maturation of FA and fibrillar adhesions (lower image). (B) Platelets in Fn1+/+ mice form tight aggregates on injured vessel walls that withstand the shear forces of the blood flow (upper image), while platelets in an injured vessel in Fn1syn/syn mice fail to withstand the blood flow leading to a delayed thrombus formation (lower image). Endothelial cells (EC); vascular smooth muscle cells (VSMC).