Figure 2

GCNT1 modifies the prostate cancer glycome. (A) GCNT1 is a key enzyme for the formation of core 2 linked O-glycans. In O-glycan synthesis GalNAc is transferred to Ser and Thr residues in the polypeptide, which can then be further extended with various carbohydrates. Four common O-glycan structures are expressed in mammalian tissues, core 1 through core 4. GCNT1 adds GlcNAc to GalNAc to form the core 2 branch. The core 2 branch is a scaffold for the production of lactosamine disaccharide repeats (specifically poly-N-acetyllactosamine) on O-glycans. (B) Lectin immunofluorescence shows PC3 cells with upregulated GCNT1 have increased levels of core 2 branched O-glycans (detected by enhanced binding of LEA and RCA₁₂₀ lectins^39,40), reduced levels of mannose terminated and biantennary structures respectively (detected using ConA lectin⁴⁰) and reduced levels of terminal GlcNAc (detected using WGA lectin⁴⁰). (C) Detection of SLe^X in PC3 cells using a glycan specific binding antibody⁴¹ indicates upregulation of GCNT1 promotes increased expression of the SLe^X antigen in prostate cancer cells. (D) Glycoproteomics to map GCNT1 glycosylation sites on specific proteins in DU145 prostate cancer cells with upregulated GCNT1 identified 60 glycopeptides as statistically significant (p < 0.001) specific substrates of GCNT1. Putative glycan structures in this figure were created using the DrawGlycan-SNFG tool⁸⁵.