PMID: 10988252

 

    Legend: Sugar

Title : Characterization of the carbohydrate chains of the secreted form of the human epidermal growth factor receptor

Abstract :

1. The human epidermal growth factor receptor ( EGFR ) is a transmembrane glycoprotein having 11 potential N-glycosylation sites in its extracellular domain
2. N-Glycosylation is needed for proper membrane insertion, EGF binding and receptor functioning
3. The human epidermoid carcinoma A431 cell line secretes a soluble 105 kDa glycoprotein ( sEGFR ) that represents the extracellular domain of the membrane-bound form, and its glycosylation pattern has been investigated
4. After liberation of the oligosaccharides from sEGFR with PNGase F , the glycans were fractionated along different routes, including Concanavalin A affinity chromatography, anion-exchange chromatography, HPLC and high-pH anion-exchange chromatography
5. The oligosaccharide fractions were characterized by 500- and 600-MHz 1H-NMR spectroscopy and mass spectrometry ( FAB , ESI , and MALDI-TOF)
6. The oligomannose-type glycans range from Man5GlcNAc2 to Man8GlcNAc2 and account for 17% of the total carbohydrate moiety
7. Furthermore, di-, tri'- and tetraantennary complex-type structures are present, both neutral and (alpha2-3)-sialylated (up to tetrasialo), comprising 24 and 59%, respectively, of the total carbohydrate moiety
8. In this study, 32 new complex-type glycans are characterized containing the Le(x), Le(Y), and sialyl-Le(x) determinants , the bloodgroup A and H antigens, as well as the ALe(Y) determinant
9. This first comprehensive glycosylation study on a human nonrecombinant receptor shows the immense heterogeneity of the glycosylation of sEGFR