Distinct Binding Interactions of α(5)β(1)-Integrin and Proteoglycans with Fibronectin

Dynamic single-molecule force spectroscopy was performed to monitor the unbinding of fibronectin with the proteoglycans syndecan-4 (SDC4) and decorin and to compare this with the unbinding characteristics of α(5)β(1)-integrin. A single energy barrier was sufficient to describe the unbinding of both SDC4 and decorin from fibronectin, whereas two barriers were observed for the dissociation of α(5)β(1)-integrin from fibronectin. The outer (high-affinity) barriers in the interactions of fibronectin with α(5)β(1)-integrin and SDC4 are characterized by larger barrier heights and widths and slower dissociation rates than those of the inner (low-affinity) barriers in the interactions of fibronectin with α(5)β(1)-integrin and decorin. These results indicate that SDC4 and (ultimately) α(5)β(1)-integrin have the ability to withstand deformation in their interactions with fibronectin, whereas the decorin-fibronectin interaction is considerably more brittle.