Oligosaccharide chains are trimmed during synthesis of the envelope glycoprotein of vesicular stomatitis virus.

Abstract

The biosynthesis and maturation of the oligosaccharide moieties of the envelope glycoprotein of vesicular stomatitis virus were investigated in virus-infected [human cervical carcinoma] HeLa and [baby hamster kidney] BHK21 cells after pulse labeling with [2-3H]mannose. Two major forms of the virus glycoprotein were detected by polyacrylamide gel electrophoresis, which appear to correspond to the viral glycoprotein with either precursor or mature oligosaccharide chains. The precursor chains in both HeLa and BHK21 cells infected with vesicular stomatitis virus obtained after a 30 min pulse were large oligomannose structures containing approximately 7-9 mannose residues as estimated by gel filtration analysis. The size of the oligomannose structures initially transferred to the protein may be larger. Mature, virus-size oligosaccharide chains, which could be detected after a 20-30 min delay, contained only 3 mannose residues and, in addition, contained branch structures terminating in sialic acid. A precursor-product relationship of these 2 forms of oligosaccharide chains was demonstrated by pulse-chase labeling of virus-infected HeLa cells. The large oligomannosyl core structures initially added to the glycoprotein were apparently being trimmed by the removal of mannose residues prior to (and/or during) the addition of the branch chains terminating in sialic acid.