DIFFERENTIAL EXPRESSION OF LACDINAC SEQUENCES (GALNAC-BETA-1-4GLCNAC-R) IN GLYCOPROTEINS SYNTHESIZED BY CHINESE-HAMSTER OVARY AND HUMAN-293-CELLS

The lacdiNAc sequence GalNAc beta 1-->4GlcNAc beta 1-R occurs in the N - and O-glycans of many glycoproteins in vertebrate and invertebrates, We now report that both human 293 cells and Chinese hamster ovary (CH O) cells contain a UDPGalNAc:GlcNAc beta 1,4 N-acetylgalactosaminyltra nsferase (beta 1,4GalNAcT) that forms the lacdiNAc sequence, The beta 1,4GalNAcT in CHO cells is distinct from beta 1,4 galactosyltransferas e in that the latter enzyme, but not the former, binds to a column of immobilized bovine alpha-lactalbumin, To determine whether endogenous glycoproteins in these cells contain lacdiNAc sequences, glycoproteins from 293 cells, CHO and Lec8 CHO cells mere desialylated and passed o ver immobilized Wisteria floribunda agglutinin (WFA), a plant lectin w ith affinity for terminal GalNAc residues, WFA bound to similar to 120 and similar to 80 kDa glycoproteins in 293 cells and glycans from the se glycoproteins contained lacdiNAc sequences. The similar to 120 kDa glycoproteins in 293 cells bound by WFA is a mixture of both the lysos ome-associated membrane glycoproteins LAMPs-1 and -2, WFA bound to two glycoproteins of similar to 47 and similar to 78 kDa in Lec8 CHO cell s, but these glycoproteins are not LAMPs and they do not contain the l acdiNAc sequence, Instead, they contain multiple GalNAc alpha-Ser/Thr O-glycans that promote binding to WFA, Thus, the beta 1,4GalNAcT in 29 3 cells displays a limited specificity in its recognition of accepters , whereas the beta 1,4GalNAcT in CHO cells fails to promote synthesis of the cognate lacdiNAc sequence, The presence of the beta 1,4GalNAcT may not be sufficient for synthesis of lacdiNAc sequences and other fa ctors may contribute to regulate the functionality of the enzyme.