Differential and cell-type specific microheterogeneity of high mannose-type Asn-linked oligosaccharides of human transferrin receptor

Abstract

The structural analysis of high mannose-type Asn-linkecl (N-linked) oligosaccharides of the human transferrin receptor (hTR) from D-[2-3H]mannose metabolic-radiolabeled human cells - A431, K562, BeWo, and HL60 - was investigated. The radiolabeled hTR glycopeptides were prepared and fractionated by a lectin chromatography of Concanavalin A-Sepharose. The composition analysis of hTR glycopeptides revealed that Con A-I contains both mannose and fucose, whereas Con A-III has mannose exclusively. The Con A-III glycopeptides were treated with Endo H. The released oligosaccharidcs were charge-fractionated by QAE-Sephadex. The neutral oligosaccharidcs were further size-fractionated by an amine absorption high performance liquid chromatography (HPLC). Our results demonstrate that the high mannose-type oligosaccharides of hTR ranged in size from Man5-R to Man9-R with cell-type specific patterns. A relative amount of each component was found to be differentially heterogeneous among the four different human cell lines.