Altered (Neo-) Lacto Series Glycolipid Biosynthesis Impairs Alpha 2-6 Sialylation On N-Glycoproteins In Ovarian Cancer Cells

The (neo-) lacto series glycosphingolipids (nsGSLs) comprise of glycan epitopes that are present as blood group antigens, act as primary receptors for human pathogens and are also increasingly associated with malignant diseases. Beta-1, 3-N-acetyl-glucosaminyl-transferase 5 (B3GNT5) is suggested as the key glycosyltransferase for the biosynthesis of nsGSLs. In this study, we investigated the impact of CRISPR-Cas9 -mediated gene disruption of B3GNT5 (Delta B3GNT5) on the expression of glycosphingolipids and N-glycoproteins by utilizing immunostaining and glycomics-based PGC-UHPLCESI-QTOF-MS/MS profiling. Delta B3GNT5 cells lost nsGSL expression coinciding with reduction of alpha 2-6 sialylation on N-glycoproteins. In contrast, disruption of B4GALNT1, a glycosyltransferase for ganglio series GSLs did not affect alpha 2-6 sialylation on N-glycoproteins. We further profiled all known alpha 2-6 sialyltransferase-encoding genes and showed that the loss of alpha 2-6 sialylation is due to silencing of ST6GAL1 expression in Delta B3GNT5 cells. These results demonstrate that nsGSLs are part of a complex network affecting N-glycosylation in ovarian cancer cells.