Ganglioside inhibition of fibronectin-mediated cell adhesion to collagen.

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Abstract
Fibronectin mediates the adhesion of cells to collagen by 1st binding to the collagen substrate, followed by attachment of the cells to the fibronectin-collagen complex. Bovine brain gangliosides blocked fibronectin-mediated cell adhesion to collagen in a concentration-dependent manner. The gangliosides did not block the binding of fibronectin to collagen but did prevent the attachment of the cells to the fibronectin-collagen complex. Of the gangliosides tested, GT1 and GD1a were the most effective inhibitors followed by GD1b .mchgt. GM1 .mchgt. GM2; GM3 was not an inhibitor. Cell adhesion inhibited with the oligosaccharide portion of the gangliosides, but not with ceramides or with a variety of free sugars of glycosaminoglycans. Mild periodate oxidation of mixed gangliosides or of GD1a were no longer inhibitory; subsequent reduction with NaBH4 did not restore the inhibitory activity of the modified gangliosides. Specific gangliosides or related sialic acid-containing glycoconjugates on the cell surface may act as the receptors for fibronectin.