Inhibition of fusion of skeletal myoblasts by tunicamycin and its reversal by N-acetylglucosamine.

The differentiation of a permanent line of rat skeletal myoblasts is inhibited by a low concentration of tunicamycin in the growth medium. At a level of 0.9 micrograms/mL, mannose incorporation in trichloroacetic-acid-insoluble material is inhibited to the extent of about 50% by the antibiotic. Blotting of glycoproteins of the cytoplasmic membrane of myoblasts separated by gel electrophoresis by radioiodinated concanavalin A revealed that four major glycoproteins of 230,0000, 145,000, 119,000, and 46,000 daltons were present in lower relative amounts in the plasma membrane following tunicamycin treatment. The 119,000 dalton glycoprotein was a major radioiodinated protein in intact cells and was presumably localized on the periphery of the membrane. The effect of tunicamycin on both fusion and glycosylation of membrane proteins could be reversed by N-acetylglucosamine, but not by the protease inhibitors leupeptin and pepstatin.