Intracellular transport and processing of Sindbis virus glycoproteins

The intracellular transport and processing of Sindbis virus envelope glycoproteins were studied in cells infected with Sindbis virus using the mannose-specific enzyme, endoglycosidase H (endo H). In pulse/chase labeling experiments of hamster cells with [35S]methionine, Sindbis glycoproteins PE2 and E1 became endo H resistant in two steps at 12.5 and 20.0 min after a 5-min pulse, suggesting that the glycoproteins required this period of time to be transported to the Golgi compartments containing the enzymes which process the high mannose side chains acquired in the endoplasmic reticulum. E2 could be detected at the end of a 5-min pulse and the E2 produced early was found to be endo H sensitive. The rate at which PE2 was converted to E2, relative to the acquisition of endo H resistance, suggests the independence of this proteolytic event from cellular protein transport and raises the possibility that the proteolytic function is of viral origin.