Glucocorticoid induction of the alpha2,6 sialyltransferase enzyme in a mouse neural cell line.

Combined sialyltransferase (ST) activities were induced in the HN9 hippocampal cell line following treatment with the synthetic glucocorticoid dexamethasone (dex) for 24 hr. Induction occurred in a dose-dependent manner, with the maximum induction of a 2-fold increase over control enzyme levels occurring at a concentration of 10(-8) M dex. A minimum of 6 hr pretreatment with drug was required before significant induction could be detected and elevated enzyme levels persisted for up to 48 hr post-treatment. The induced form of the enzyme showed an increase in reaction maximum velocity (Vmax) while showing no change in affinity (Km) for the acceptor substrate asialofetuin. The alpha2,6 ST enzyme was demonstrated to be the primary enzyme induced and there was no change in expression of the alpha2,3 ST enzyme. Lectin blot analysis demonstrated an increase in the levels of the alpha2,6-linked cellular sialoglycoproteins and a parallel decrease in the alpha2,3 sialoglycoprotein levels.