Abstract
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 α5β1-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 α5β1-integrin from fibronectin. The outer (high-affinity) barriers in the interactions of fibronectin with α5β1-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 α5β1-integrin and decorin. These results indicate that SDC4 and (ultimately) α5β1-integrin have the ability to withstand deformation in their interactions with fibronectin, whereas the decorin-fibronectin interaction is considerably more brittle.
Highlights
It is well known that the binding between ligands and receptors at the cell surface regulate cell function and behavior [1]
Control experiments were carried out on an uncoated surface to test that the chemically modified probes successfully exhibited proteins at cysteine residues via PEG chains. This is important for syndecan, which is relatively depleted in cysteine compared to other PGs [48,49]
Single-molecule events characterized in the measurements between the SDC4 probe and the fibronectin surface were not observed on an uncoated gold substrate, indicating that the rupture events are due to the functionalized probe and fibronectin
Summary
It is well known that the binding between ligands and receptors at the cell surface regulate cell function and behavior [1]. Cell responses are controlled by the cell environment such as the extracellular matrix (ECM) and binding of specific cell surface molecules to matrix proteins. Fibronectin is a large protein of $0.5 MDa, which comprises two similar subunits attached through disulfide linkages. It is a primary ECM component and interacts with cell surface integrins and proteoglycans [2,3]. Integrins are transmembrane proteins that comprise an aand a b-subunit and provide attachment to the ECM and. The transmembrane domain is linked to the actin cytoskeleton via membrane proximal proteins, including talin and vinculin, and exists in high- or low-affinity states depending on their internal structure [7]
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