EFFECTS OF DIBUTYRYL-CAMP AND BROMODEOXYURIDINE ON EXPRESSION OF N-ACETYLGLUCOSAMINYLTRANSFERASE-III AND N-ACETYLGLUCOSAMINYLTRANSFERASE-V IN GOTO NEUROBLASTOMA-CELLS

The sugar chain structures of the cell surface change dramatically dur ing cellular differentiation. A human neuroblastoma cell line, GOTO, i s known to differentiate into neuronal cells and Schwannian cell-like cells on treatments with dibutyryl cAMP and bromodeoxyuridine, respect ively. We have examined the expression of UDP-N-acetylglucosamine: bet a-D-mannoside beta-1,4N-acetylglucosaminyltransferase III (GnT-III:EC 2.4.1.144) and UDP-N-acetylglucosamine: alpha-6-D-mannoside beta-1,6N- acetylglucosaminyltransferase V (GnT-V: EC 2.4.1.155), two major branc h forming enzymes in N-glycan synthesis, in GOTO cells on two distinct directions of differentiation. In neuronal cell differentiation, GnT- III activity showed a slight increase during initial treatment with Bt (2)cAMP for 4 days and decreased drastically after the fourth day, but the mRNA level of GnT-III did not show a decrease but in fact a sligh t increase. GnT-V activity increased to approximately two- to three-fo ld the initial level with increasing mRNA level after 8 days, and lect in blot analysis showed an increase in reactivity to Datsura stramoniu m (DSA) of the immunoprecipitated neural cell adhesion molecule (NCAM) . In Schwannian cell differentiation, the activity and mRNA level of G nT-III showed no significant change on treatment with BrdU. GnT-V acti vity also showed no change in spite of the gradual increase in the mRN A level. These results suggest that the activation of GnT-V during neu ronal cell differentiation of GOTO cells might be a specific change fo r branch formation in N-glycans, and this affects the sugar chain stru ctures of some glycoproteins such as NCAM.