Soluble fibronectin interaction with cell surface and extracellular matrixis mediated by carbohydrate-to-carbohydrate interaction

Cell adhesion and spreading on solid phase fibronectin (FN), coated on plat e or presented in extracellular matrix, are mediated by integrin receptors alpha 5 beta 1, alpha 4 beta 1, etc., although binding of ''soluble-form F' ' to cell surface varies extensively depending on glycosylation status of F N per se. Deposition or incorporation at the cell surface or pericellular m atrix of soluble-form FN from body fluids or synthesized de novo takes plac e through a yet-unknown (perhaps integrin-independent) mechanism. Here we p resent evidence that the mechanism involves carbohydrate-to-carbohydrate in teraction. Binding or incorporation of soluble-form placental or hepatoma F N to cell surface or pericellular matrix is highly dependent on the specifi c glycosylation status of FN per se and combination with glycosylation stat us of the cell surface, and is greatly promoted by a certain type of coexis ting (shedded) glycosphingolipid, A few lines of study indicate that the pr ocess is mediated by interaction of FN carbohydrate with cell surface carbo hydrate. The great enhancement of the binding process by glycosphingolipid is based on dual interaction of glycosphingolipid carbohydrate with FN carb ohydrate and with cell surface carbohydrate. Here we present an example of promotion of binding of soluble-form FN from placenta or from hepatoma cell s, having a specific carbohydrate epitope termed ''disialyl-I,'' to K562 or VA13 cell surface in the presence of glycosphingolipid Gg3, which interact s specifically with disialyl-I. (C) 2000 Academic Press.