The Relative Activities of the C2GnT1 and ST3Gal-I Glycosyltransferases Determine O-Glycan Structure and Expression of a Tumor-associated Epitope on MUC1
| Autor: | Joy Burchell, Joyce Taylor-Papadimitriou, Inka Brockhausen, Stephen Gschmeissner, Henrik Clausen, Caroline A. Whitehouse, Martin Dalziel, Tilo Schwientek, Ian McFarlane |
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| Rok vydání: | 2001 |
| Předmět: |
beta-Galactoside alpha-2
3-Sialyltransferase Glycosylation Molecular Sequence Data Breast Neoplasms N-Acetylglucosaminyltransferases Biochemistry Epitope chemistry.chemical_compound symbols.namesake Glycosyltransferase Tumor Cells Cultured Humans skin and connective tissue diseases Molecular Biology MUC1 biology Mucin-1 Cell Biology Transfection Golgi apparatus Molecular biology Sialyltransferases Sialic acid Enzyme Activation carbohydrates (lipids) Epitope mapping chemistry biology.protein symbols Female Epitope Mapping |
| Zdroj: | Journal of Biological Chemistry. 276:11007-11015 |
| ISSN: | 0021-9258 |
| DOI: | 10.1074/jbc.m006523200 |
| Popis: | In breast cancer, the O-glycans added to the MUC1 mucin are core 1- rather than core 2-based. We have analyzed whether competition by the glycosyltransferase, ST3Gal-I, which transfers sialic acid to galactose in the core 1 substrate, is key to this switch in MUC1 glycosylation that results in the expression of the cancer-associated SM3 epitope. Of the three enzymes known to convert core 1 to core 2, by the addition of GlcNAc to GalNAc in core1 C2GnT1 is the dominant enzyme expressed in normal breast tissue. Expression of C2GnT1 is low or absent in around 50% of breast cancers, whereas expression of ST3Gal-I is consistently increased. Mapping of ST3Gal-I and C2GnT1 within the Golgi pathway showed some overlap. To examine functional competition, the enzymes were overexpressed in T47D cells, which normally make core 1-based structures, have no detectable C2GnT1 activity and express the SM3 epitope. Overexpression of C2GnT1 resulted in loss of binding of SM3 to MUC1, accompanied by a decrease in the GalNAc/GlcNAc ratio, indicative of a switch to core 2 structures. Transfection of a C2GnT1 expressing line with ST3Gal-I restored SM3 binding and reduced GlcNAc incorporation into MUC1 O-glycans. Thus, even when C2GnT1 is expressed, the O-glycans added to MUC1 become core 1-dominated structures, provided expression of ST3Gal-I is increased as it is in breast cancer. |
| Databáze: | OpenAIRE |
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