Expression and N-glycan analysis of human 90K glycoprotein in Drosophila S2 cells

Human 90K (h90K; Mac-2-binding protein) glycoprotein is a potential pharmaceutical due to its inhibitory activity against cancer metastasis and expansion. Here, h90K glycoprotein was produced in insect Drosophila S2 cell system, and its N-glycan pattern was analyzed. A plasmid encoding h90K gene, fused with a hexahistidine tag under the control of Drosophila metallotionein promoter, was stably transfected into S2 cells. After copper sulfate induction, transfected S2 cells secreted recombinant h90K at a good expression level of 28mg/L in a 150-mL spinner flask culture. The purified recombinant h90K showed an apparent molecular weight of ∼78kDa which was much smaller than that (∼97kDa) of the natural h90K. Because de-N-glycosylated h90K appeared at ∼60kDa protein band, it was suggested that the recombinant h90K from S2 cells has small N-glycans with about half the molecular weight (∼18kDa) of N-glycans of the natural h90K. Through detail analyses using high-performance liquid chromatography and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, the S2-derived recombinant h90K was confirmed that it has simple paucimannosidic structures containing two or three mannose residues with core fucose as the major (∼79%) N-glycans.