EXPRESSION OF HUMAN INTERFERON OMEGA-1 IN SF9 CELLS - NO EVIDENCE FORCOMPLEX-TYPE N-LINKED GLYCOSYLATION OR SIALYLATION

Human interferon omega1 (IFN-omega1) was expressed in Spodoptera frugi perda Sf9 insect cells using the baculovirus expression system. Half o f the protein purified by immunoaffinity chromatography was shown to b e N-glycosylated at the same site as the natural IFN-omega1. The degre e of glycosylation was independent of the expression rate. While natur al IFN-omega1 was shown to carry complex-type oligosaccharides [Adolf, G. R., Maurer-Fogy, I., Kalsner, I. & Cantell, K. (1990) J. Biol. Che m. 265, 9290-9295], the insect cell produced protein which was demonst rated by lectin blot, mass spectroscopy and HPLC analysis to contain o nly the core oligosaccharide. Two different structures, (Man)2(GlcNAc) 2[Fuc] and (Man)3(GlcNAc)2[Fuc] were identified. The fucosylation was identified to be (alpha1-6)-linked to the core saccharide. Sialic acid residues were clearly absent. IFN-omega1 expressed in S. frugiperda c ells was shown to be partially truncated at the C-terminus by nine res idues; its antiviral activity when glycosylated was significantly lowe r than the activity of IFN-omega1 produced by Sendai-virus-stimulated leukocytes. Circular dichroism and fluorescence spectroscopy did not r eveal any structural differences between glycosylated and nonglycosyla ted IFN-omega1. This implies the importance of a complex-type glycosyl ation for the maximal biological activity of human IFN-omega1.