THE ROLE OF N-GLYCOSYLATION IN CELL-FUSION INDUCED BY A VACCINIA RECOMBINANT VIRUS EXPRESSING BOTH MEASLES-VIRUS GLYCOPROTEINS

We have evaluated the effect of inhibitors of N-glycosylation on syncytia formation in HeLa cell infected by a recombinant vaccinia virus expressing the measles virus hemagglutinin (HA) and fusion (F) glycoproteins (VV-HA/F). Inhibitors which block glucose trimming of oligosaccharide side chains of glycoproteins (glucosidase inhibitors) prevented syncytium formation. On the other hand, inhibitors which block trimming of mannose residues (mannosidase inhibitors) did not prevent syncytium formation. The HA and F synthesized in the presence of either glucosidase or mannosidase inhibitors oligomerized and were transported to the cell surface. Concanavalin A, a mannose-specific lectin, inhibited syncytium formation. The inhibitors did not block the cleavage of the F protein, but in fact enhanced it. These studies demonstrate the importance of protein N-glycosylation in the process of membrane fusion and suggest that trimming of glucose residues and the presence of terminal mannose residues are required for VV-HA/F syncytium induction. (C) 1994 Academic Press, Inc.