Cell Surface Glycoconjugates


In eukaryotic cells, the interface between the extracellular space and the intracellular matrix is formed of a lipid bilayer in which structural or functional proteins are anchored. Carbohydrates also form components of the cell surface, as glycoconjugates, i.e. glycolipids or glycoproteins. Although the carbohydrate moieties account for a minor part in mass (5–10%), their location at the external face of the membrane confers upon them unique biological functions as ‘recognition signals’.

Keywords: glycoconjugates; cell recognition

Figure 1.

Membrane insertion of glycoconjugates. Protein moieties are inserted via their transmembrane hydrophobic domain: (a) N‐glycoprotein; (b) mucin type O‐glycosyl protein; (c) proteoglycan; (d) O‐glycosylated protein stem bearing a receptor domain. Insertion via a lipid moiety; (e) sphingoglycolipid; (f) N‐glycosylprotein anchored by a glycosylphosphatidylinositol; (g) proteoglycan anchored by a glycosylphosphatidylinositol.

Figure 2.

Illustration of cell‐specific recognition by lectin. Thymus is composed of mature (fully sialylated) (white) and immature (partially sialylated) (grey) thymocytes. Use of peanut agglutinin, which recognizes β‐galactosyl residues, allows agglutination of immature thymocytes. Red squares, β‐galactosyl residue; blue ovals, sialyl residue.

Figure 3.

Glycans as recognition signals. The different interactions mediated by the cell surface carbohydrates: cell–cell, cell–bacterium, cell–virus and recognition of asialoglycoprotein, antibody and lectin.


Further Reading

Dennis JW, Granovsky M and Warren CE (1999) Glycoprotein glycosylation and cancer progression. Biochimica et Biophysica Acta 1473: 21–34.

Feizi T (1990) The major blood group ABO(H) determining genes are isolated. Trends in Biochemical Sciences 15: 330–331.

Feizi T and Childs R (1987) Carbohydrates as antigenic determinants of glycoproteins. Biochemical Journal 245: 1–11.

Feizi T and Galustian C (1999) Novel oligosaccharide ligands and ligand‐processing pathways for the selectins. Trends in Biochemical Sciences 24: 369–372.

Fukuda M (1985) Cell surface glycoconjugates as onco‐differentiation markers in hematopoietic cells. Biochimica et Biophysica Acta 780: 119–150.

Fukuda M, Hiraoka N and Yek J‐C (1999) C‐Type lectins and sialyl lewis X oligosaccharides: versatile roles in cell–cell interaction. Journal of Cell Biology 147: 467–470.

Hakomori S‐I, Handa K, Iwabuchi K, Yamamura S and Prinetti A (1998) New insights in glycosphingolipid function: ‘glycosignaling domain’, a cell surface assembly of glycosphingolipids with signal transducer molecules, involved in cell adhesion coupled with signaling. Glycobiology 8: xi–xix.

Montreuil J, Vliegenthart JFG and Schachter H (1995) Glycoproteins. In: Neuberger A and van Deenen LLM (eds) New Comprehensive Biochemistry, chaps 29a, 29b. Amsterdam: Elsevier.

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Verbert, André, and Cacan, René(Apr 2001) Cell Surface Glycoconjugates. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1038/npg.els.0000707]