EXPRESSION OF HUMAN H-TYPE ALPHA-1,2-FUCOSYL-TRANSFERASE ENCODING FORBLOOD-GROUP H(O) ANTIGEN IN CHINESE-HAMSTER OVARY CELLS - EVIDENCE FOR PREFERENTIAL FUCOSYLATION AND TRUNCATION OF POLYLACTOSAMINE SEQUENCES

The human H(O) blood group is specified by the structure Fuc alpha 1-2 Gal beta 1-R, but the factors regulating expression of this determinan t on cell surface glycoconjugates are not well understood. To learn mo re about the regulation of H blood group expression, cDNA encoding the human H-type GDPFuc:beta-D-galactoside alpha 1,2-fucosyltransferase ( alpha 1,2FT) was stably transfected into Chinese hamster ovary (CHO) c ells, The new cell line, designated CHO(alpha 1,2)FT, expressed surfac e neoglycans containing the H antigen. The structures of the fucosylat ed neoglycans in CHO(alpha 1,2)FT cells and the distribution of these glycans on glycoproteins were characterized. Seventeen percent of the [H-3]Gal-labeled glycopeptides from CHO(alpha 1,2)FT cells bound to th e immobilized H blood group-specific lectin Ulex europaeus agglutinin- I (UEA-I), whereas none from parental CHO cells bound to the lectin. T he glycopeptides from CHO(alpha 1,2)FT cells binding to UEA-I containe d polylactosamine [3Gal beta 1-4GlcNAc beta 1-] with the terminal sequ ence Fuc alpha 1-2Gal beta 1-4GlcNAc-R. Fucosylation of the polylactos amine sequences on complex-type N-glycans in CHO(alpha 1,2)FT cells ca used a decrease in both sialylation and length of polylactosamine. Une xpectedly, only small amounts of terminal fucosylation was found in di antennary complex type N-glycans. The O-glycans and glycolipids were n ot fucosylated by the H-type alpha 1,2FT. Two major high molecular wei ght glycoproteins, one of which was shown to be the lysosome-associate d membrane glycoprotein LAMP-1, preferentially contained the H-type st ructure and were bound by immobilized UEA-I. These results demonstrate that in CHO cells the expressed H-type alpha 1,2FT does not indiscrim inately fucosylate terminal galactosyl residues in complex-type N-glyc ans, but it favors glycans containing polylactosamine and dramatically alters their length and sialylation.