N-glycosylation patterns of HSA/CD24 from different cell lines and brain homogenates: a comparison.

N-glycans of the mouse glycoprotein HSA and its human analogue CD24 from lymphoblastoma, neuroblastoma and astrocytoma cell lines as well as from mouse brain homogenate were analysed and compared to each other and to the N-glycosylation pattern of total glycoproteins from mouse and human brain. The N-glycans were released from PVDF-blotted HSA or CD24 and separated on Carbograph SPE into neutral and acid glycans. The naturally neutral glycan fraction and the fraction of glycans rendered neutral after neuraminidase treatment were analysed without further purification by MALDI-MS. In each fraction, about 25 molecular ions with an intensity >10% of the base peak were identified which corresponded to glycans with distinct isobaric monosaccharide compositions. Comparison of the neutral and desialylated glycans revealed some similarities between the samples analysed, but also clear differences. HSA and CD24 from all cell lines express almost no neutral N-glycans with two or more fucose in contrast to brain HSA and glycoproteins from mouse and human brain. The lack of extensive fucosylation was also observed for desialylated glycans of HSA and CD24 from all cell lines analysed except for CD24 from a human neuroblastoma cell line which exhibits like total human and mouse brain glycoproteins a large variety of highly fucosylated, higher branched N-glycans. HSA from mouse brain carries in addition desialylated non-fucosylated glycans of high abundance which were detected, if at all, only at low intensity in all other samples analysed suggesting that they may be implicated in specific functions of mouse brain HSA. Therefore, a rapid assessment of similarities or differences between glycosylation patterns of a glycoprotein isolated from different sources is possible using methods as described here.