Comparison of three glycoproteomic methods for the analysis of CHO cells treated with 1,3,4-O-Bu 3 ManNAc

Comprehensive analysis of the glycoproteome is critical due to the widespread importance of this post-translational modification to protein function, and difficult because of the tremendous complexity it exhibits. Here we compared three glycoproteomic analysis methods, a recently described chemoenzymatic glycoproteome analysis methods, N-linked glycans and glycosite containing peptides (NGAG), Solid-phase extraction of N-linked glycoproteins (SPEG), and hydrophilic interaction liquid chromatography (HILIC), for the analysis of N-linked glycosites of Chinese hamster ovarian (CHO) cells treated with 1,3,4-O-BuManNAc. The NGAG protocol resulted in substantially increased glycosite identifications over both SPEG and HILIC. Interestingly, while the glycosites identified by SPEG and HILIC overlapped strongly, NGAG identified many glycosites not observed in either of the other two methods. Further, utilizing the enhanced intact glycopeptide identification afforded by the NGAG workflow, we also found that of the sugar analog 1,3,4-O-BuManNAc increases sialylation of proteins secreted by CHO cells, including an ectopically expressed human proteins.