N-terminal Vacuolar Sorting Signal at the Mouse Antibody Alters the N-linked Glycosylation Pattern in Suspension-cultured Tobacco BY2 Cells

Recombinant DNA technology enables the use of plants as the host for the production of pharmaceutical proteins, such as antibodies. The glycosylation of recombinant proteins plays physiological and biological roles. However, because glycosylation in plants is different from that in human cells, the development of glycoengineering is required. In plant cells, glycan structures are shown to correlate with the localization of the recombinant protein produced. In this study, the vacuolar sorting signal (VSS) of sporamin was fused to the heavy (H) and light (L) chains of a mouse monoclonal antibody (mAb), and the mAb was produced in suspension-cultured tobacco BY2 cells. The sugar chain structures were determined by high-performance liquid chromatography, exoglycosidase digestion, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Typical plant glycans with α1,3-fucosylation and/or β1,2-xylosylation derived from mAb with the VSS-fused H-chain (mIgG1000) and mAb with the VSS-fused H- and L-chain (mIgG1010) occupied the large amount of the total N-glycans, 72.1% and 85.0%, respectively, such as those derived from mAb without VSS (mIgG0000), 74.6% (Fujiyama et al., J. Biosci. Bioeng., 101, 212-218, 2006). In contrast, the typical plant glycan structure Man₃FucXylGlcNAc₂ particularly in vacuoles accounted for 37.8% of the total sugar chains derived from mIgG1000 and 58.5% of those derived from mIgG1010 compared with 24.3% of those derived from mIgG0000. These results suggest that the sporamin signal peptide fused to mAb acts as a VSS and leads to the increase in the amount of Man₃FucXylGlcNAc₂, which is the main N-glycan structure in vacuoles.