Mammalian glycosyltransferase expression allows sialoglycoprotein production by baculovirus-infected insect cells

The baculovirus-insect cell expression system is widely used to produce rec ombinant mammalian glycoproteins, but the glycosylated end products are rar ely authentic. This is because insect cells are typically unable to produce glycoprotein glycans containing terminal sialic acid residues. In this stu dy, we examined the influence of two mammalian glycosyltransferases on N-gl ycoprotein sialylation by the baculovirus-insect cell system. This was acco mplished by using a novel baculovirus vector designed to express a mammalia n alpha2,6-sialyltransferase early in infection and a new insect cell line stably transformed to constitutively express a mammalian beta1,4-galactosyl transferase. Various biochemical assays showed that a foreign glycoprotein was sialylated by this virus-host combination, but not by a control virus-h ost combination, which lacked the mammalian glycosyltransferase genes. Thus , this study demonstrates that the baculovirus-insect cell expression syste m can be metabolically engineered for N-glycoprotein sialylation by the add ition of two mammalian glycosyltransferase genes. (C) 2001 Academic Press.