Polylactosamine synthesis and branch formation of N-glycans in β1,4-galactosyltransferase-1-deficient mice

Analysis of glycans from erythrocyte membrane glycoproteins from β1,4-galactosyltransferase-1 (β4GalT-1)-deficient mice revealed moderately decreased galactosylation but comparable polylactosamine content compared to control β4GalT-1+/− mice. The increased expression of more branched N-glycans was observed in β4GalT-1−/− mice, and its extent was more remarkable in elder β4GalT-1−/− mice (28 weeks old) than in younger β4GalT-1−/− mice (6–9 weeks old). In relation to this issue, the less galactosylation of biantennary glycans was observed in the elder group, suggesting that β4GalTs actually compete with N-acetylglucosaminyltransferases IV and V in erythroid cells. In contrast, approximately 80% of core 2 O-glycans were not β1,4-galactosylated regardless of age of the knockout mice. These results suggest that β4GalT-1 expressed in erythroid cells may regulate a constant branch formation of N-glycans and plays a predominant role in β1,4-galactosylation of core 2 O-glycan.