Glycosylation mutants of dengue virus NS1 protein.

The non-structural glycoprotein NS1 of dengue virus type 2 contains sites for N-linked glycosylation at Asn-130 and Asn-207. NS1 synthesized in infected cells is glycosylated at both locations. We have now examined the dimerization and secretion of NS1 lacking one or both of these sites by transient expression of mutagenized cDNA inserted into a simian virus 40-based vector. Immunoblotting and radioimmunoprecipitation were used to detect NS1 associated with transfected cells and in the extracellular medium. Elimination of one or both glycosylation sites did not abolish dimerization and secretion of NS1. However, NS1 lacking Asn-207 showed reduced dimer stability and secretion. Treatment of secreted NS1 with endoglycosidase H demonstrated that complex glycans were attached at Asn-130 and high-mannose glycans at Asn-207.