β-Adrenergic activation of glycosyltransferases in the dolichylmonophosphate-linked pathway of protein N-glycosylation

Abstract

β-Adrenoreceptor stimulation of rat parotid acinar cells increases the activity of several microsmal membrane associated, dolichylmonophosphate (Dol-P) linked glycosyltransferases. The activities of Man-P-Dol synthase and Glc-PDol synthase are increased by ∼50%, and the activity of N-acetylglucosaminyl 1-phosphate transferase plus N-acetylglucosaminyl transferase increased by ∼60%, after agonist treatment. Increases in enzyme activity are (i) independent of endogenous Dol-P levels and (ii) observed under conditions in which the specific activities of donor sugar nucleotides are kept constant. Activation of these enzymes is specific since comparable levels of NADPH-cytochrome c reductase are found in control and agonist-treated membranes. The data thus provide the initial demonstration of neurotransmitter modulation of enzymes in the dolichol-linked pathway of protein N-glycosylation.