Abstract: Insect-baculovirus expression system has been widely used to produce recombinant proteins. However, due to its deficiency in the post-translation modification, complex terminal sialylated N-linked glycans can not be obtained, thereby largely limiting the application of this system in biopharmaceutical industry. By comparing the glycosylation pathways in mammalian and insect cells, it is known that the initial steps are the same and then diverge. The differences mainly include that insect cells lack the mammalian glycosyltransferases like N-acetylglucosaminyltransferase II, galaetosyltransferase/N-acetylgalactosyltransferase, α-2,3-sialyltransferase and α-2,6-sialyltransferase. On the other hand, insect cells possess specific α-1,3-fucosyltransferase and N-acetylglucosaminidase which can specifically remove the terminal GlcNAc from GlcNAcMan3GlcNAc(±α3/6-Fuc)GlcNAc. Based on the comparison, this article summarized the research efforts to produce humanized proteins in insect cells through the inhibition of GlcNAcase and knock-in of the mammalian glycosyltransferases. The results showed that engineered insect cells could produce humanized glycoproteins, which would greatly expand the application of insect-baculovirus expression system. In addition, the feasibility of production of humanized proteins by selection of novel insect cell lines and/or culture condition was discussed.

Key words: Insect cells, mammalian cells, glycoprotein, protein Nglycosylation pathway, glycan, humanized glycoprotein