Structural differences between complex-type Asn-linked glycan chains of glycoproteins in rat hepatocytes and Zajdela hepatoma cells.
Using serial lectin-affinity chromatography, glycosidase digestion, and NMR and methylation analysis, the structures of complex N-linked glycan chains (M(r) range 2000-3500) of rat hepatocytes and poorly differentiated chemically transformed Zajdela ascites hepatoma cells were determined and compared. The results revealed considerable differences between the two cell types: (i) hepatoma cells only expressed tri- and/or tetra-antennary complex N-linked glycan chains, whereas hepatocytes displayed large amounts of bi-antennary N-linked structures and smaller amounts of tri-/tetra-antennary structures; (ii) 20% of the glycan chains in hepatoma cells contained a bisecting GlcNAc residue which was beta (1,4)-linked to the beta-mannosyl residue of the core and was not detected in the hepatocytes; (iii) hepatoma cells expressed a high proportion of the fucosylated or not GlNAc beta (1,6) Man alpha 1-->branch, whereas hepatocytes only contained a little of this branch; (iv) hepatoma cells, but not hepatocytes, exhibited a repeating (Gal beta(1,4) GlcNAc beta (1,3)) sequence characteristic of poly-N-acetyllactosaminoglycans. These glycans were capped by both alpha-galactosyl and sialyl residues; (v) The alpha (2,3)/alpha (2,6)-linkage ratio of sialic acid was significantly higher in hepatoma cells (4/1 vs. 2/1 in hepatocytes); (vi) Only hepatocytes expressed an unusual structure in which a sialyl residue was alpha (2,6)-linked to a GlcNAc residue located within a NeuAc alpha (2,3) Gal beta (1,3) GlcNAc branch which was beta (1,4)-linked to Man alpha 1,3-->. The differences between these complex N-linked glycan chains in hepatocytes and hepatoma cells seem to be both quantitative and qualitative, since some glycan structures were only present in one cell type.
Goulut-Chassaing
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C
Laboratoire de Biochimie Cellulaire, U.F.R. Biomédicale des Saints-Pères, Paris, France.
Bourrillon
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R
D000818:Animals; D002240:Carbohydrate Sequence; D002846:Chromatography, Affinity; D005959:Glucosidases / Q000378:metabolism; D006020:Glycopeptides / Q000737:chemistry; D037102:Lectins; D008099:Liver / Q000737:chemistry*; D008114:Liver Neoplasms, Experimental / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008562:Membrane Glycoproteins / Q000737:chemistry*; D008745:Methylation; D008969:Molecular Sequence Data; D051381:Rats; D017207:Rats, Sprague-Dawley
D006020:Glycopeptides; D037102:Lectins; D008562:Membrane Glycoproteins; D005959:Glucosidases