Deletions into an NH2-terminal hydrophobic domain result in secretion of rotavirus VP7, a resident endoplasmic reticulum membrane glycoprotein

The carbohydrate present on VP7 is of the high-mannose type and is endo-H sensitive, consistent with its ER location and the absence of terminal processing of the oligosaccharide. Analysis of VP7 glycoprotein processing shows that it does not reach the Golgi apparatus but rather accumulates in a subcompartment of the ER in a processing pathway quite different from VSV G-protein (21) . In our current observations, it should be noted that there is a distinctly larger size of the secreted VP7s in mutants 47-61, 43-61, and 42-61, due to the terminal glycosylation; they are also sensitive to tunicamycin and resistant to endo-H. This observation underscores the ER location of wild-type VP7 since it is apparent that its N-linked glycosylation can be modified and were the wild-type molecule to have reached the Golgi apparatus, further processing and terminal glycosylation should have occurred. In the mutant VP7s, the efficiency of secretion appears to be high for two reasons. First, there is no endo-Hresistant material inside the cell after either 2.5 or 4 h of labeling. Second, the amount of material secreted is similar in amount to that seen intracellulady.