Effect of inhibitors of glycoprotein processing on integrin and the adhesion of myoblasts to extracellular matrix proteins

The effect of the glucosidase inhibitors N-methyl-1-deoxynojirimycin (MDJN) and bromoconduritol on the adhesion of chick myoblasts and rat L6 myoblasts to fibronectin and laminin was compared with that of the mannosidase I inhibitor, 1-deoxymannojirimycin (ManDJN). Chick and rat L6 myoblasts treated with glucosidase inhibitors showed impaired binding to fibronectin. Glucosidase inhibitor-treated chick, but not rat L6, myoblasts also showed impaired binding to laminin. In contrast ManDJN had no significant effect on the adhesion of rat or chick cells to either substrate, suggesting that complex oligosaccharides are not required for normal biosynthesis of myoblast fibronectin or laminin receptors. Binding of monoclonal antibody JG22 to glucosidase-inhibitor-treated myoblasts revealed a marked decrease in the number of integrin molecules available at the cell surface. We suggest that the previously reported inhibitory effects of glucosidase inhibitors on the terminal differentiation of myoblasts may be mediated, at least in part, through their effect on integrin accumulation.