Maturation of Hantaan virus glycoproteins G1 and G2

Hantaan virus-infected Vero E6 cell lysates were used for immunoprecipitation with monoclonal antibodies against glycoprotein G1 (MAbG1) or G2 (MAbG2). When cell lysates were prepared with buffer containing nonionic detergent, both G1 and G2 glycoproteins were precipitated with either MAbG1 or MAbG2. In contrast, when cell lysates were prepared with a buffer containing ionic detergents MAbG1 precipitated only glycoprotein G1 and MAbG2 precipitated only glycoprotein G2. Heterodimers and possibly higher oligomeric forms of the glycoproteins were detected on nonreducing SDS-polyacrylamide gels only after chemical cross-linking and immunoprecipitation with either MAbG1 or MAbG2. In order to determine the sites of Hantaan virus glycoproteins maturation and the G1-G2 complex formation, infected cells were treated with inhibitors that prevent specific steps of oligosaccharide processing. Furthermore, glycoproteins G1 and G2 immunoprecipitated from infected cell lysates or from isolated virus particles were tested for sensitivity to endoglycosidase H, endoglycosidase F, and endoglycosidase D. The results of these experiments show that maturation of both G1 and G2 takes place in the endoplasmic reticulum (ER). Furthermore, G1-G2 complex formation occurs in the ER as well, since the two glycoproteins co-precipitated with either MAbG1 or MAbG2 from infected cell lysates treated with brefeldin A and prepared with buffer containing nonionic detergent.