Two distinct mechanisms for the interaction of cells with fibronectin substrata

Fibronectin (Fn) was adsorbed onto neutral, sulfonated, imine-conjugated or gelatin coated polystyrene latex beads. In all cases, the Fn coated beads bound effectively to Chinese hamster ovary (CHO) cells in suspension. However, the binding of Fn coated neutral or positively charged imine conjugated bead was inhibited by low concentrations of heparin or heparan sulfate or by treatment of the cells with Flavobacterium heparanase. By contrast, binding of Fn coated sulfonated or gelatin beads was insensitive to inhibition by heparin and to heparanase treatment of cells. Adhesion of CHO cells to Fn coated tissue culture plastic was not sensitive to heparin, whereas adhesion of CHO cells to Fn-coated imine-conjugated plastic was sensitive to heparin. These observations imply that the functional status of Fn can be modulated by the nature of the surface to which the Fn is adsorbed. They further imply that, under some circumstances, the heparin/heparan sulfate binding domains of Fn can play a role in the attachment of Fn to the cell membrane via membrane proteoglycans. Under other circumstances, the interaction of Fn with the cell may primarily involve other receptors for Fn, presumably cell surface glycoproteins.