Fibronectin–collagen binding and requirement during cellular adhesion

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Abstract
Fibronectin isolated from human plasma and from the extracellular matrices of cell monolayers mediates the attachment in vitro and spreading of trypsin-treated cells on a collagen substratum. Fibronectin-dependent kinetics of cellular attachment to collagen were studied for several adherent cell types. Trypsin-treated human umbilical-cord cells, mouse sarcoma CMT81 cells, endothelial cells and human fibroblasts from a patient with Glanzmann''s disease were completely dependent on fibronectin for their attachment to collagen; guinea pig and monkey smooth muscle cells and chick embryo secondary fibroblasts displayed varying degrees of dependence on fibronectin for their attachment. Radiolabeled human plasma fibronectin possessed similar affinity for collagen types I, II and III from a variety of sources. The fibronectin bound equally well to the collagens with or without prior urea treatment. In the fibronectin-mediated adhesion assay using PyBHK fibroblasts, a greater number of cells adhered and more spreading was observed on urea-treated collagen. Fibronectin extracted from the extracellular matrix of chick embryo fibroblasts and that purified from human plasma demonstrated very similar kinetics of complexing to collagen-coated tissue culture dishes. Fibronectin from both sources bound to collagen in the presence of 0.05-4.0 M NaCl and over the pH range 2.6-10.6. The binding was inhibited when fibronectin was incubated with 40-80% ethylene glycol, the ionic detergents sodium dodecyl sulfate and deoxycholate, and the non-ionic detergents Nonidet P-40, Tween 80 and Triton X-100, all at a concentration of 0.1%. Fibronectin-collagen complexing is mainly attributable to hydrophobic interactions.