Induction of glycoprotein biosynthesis in activated B lymphocytes.
Resting murine splenic B lymphocytes (B cells) can be stimulated to proliferate by exposure to a variety of polyclonal activators. To investigate changes in glycoprotein synthesis that occur during the activation process, N-glycosylation activity was assessed by following the incorporation of [2-3H]mannose into dolichol-linked oligosaccharide intermediates and glycoprotein after B cells were exposed to anti-immunoglobulin M (anti-mu). Stimulation of B cells by anti-mu resulted in a dramatic induction of N-glycosylation activity. The incorporation of radiolabeled mannose into oligosaccharide-lipid increased 9-fold while the rate of labeling of glycoprotein increased 27-fold between 18 and 38 h after exposure to anti-mu. Maximal stimulation of N-glycosylation activity was observed at an anti-mu concentration of 20-50 micrograms/ml. Similar results were obtained when B cells were activated by bacterial lipopolysaccharide (LPS), another polyclonal activating agent. The major dolichol-bound oligosaccharide labeled during the induction period was determined to be Glc3Man9GlcNAc2 by HPLC analysis. Nearly full induction of oligosaccharide-lipid synthesis and protein N-glycosylation was also seen when DNA synthesis was suppressed by activating B cells with anti-mu in a serum-free medium, or by activating with anti-mu or LPS in the presence of hydroxyurea. The results suggest that the N-glycosylation pathway is induced during the G0 to G1 transition or during the G1 period, and that entry into S phase is not required. These studies describe a striking developmental increase in N-glycosylation activity and extend the information on biochemical changes occurring during the activation of B cells.
D000818:Animals; D001402:B-Lymphocytes / Q000378:metabolism*; D004261:DNA Replication / Q000187:drug effects; D006023:Glycoproteins / Q000096:biosynthesis*; D006031:Glycosylation; D006918:Hydroxyurea / Q000494:pharmacology; D007399:Interphase; D008358:Mannose / Q000378:metabolism; D051379:Mice; D008811:Mice, Inbred DBA; D013936:Thymidine / Q000378:metabolism; D014529:Uridine / Q000378:metabolism
D006023:Glycoproteins; D008358:Mannose; D013936:Thymidine; D014529:Uridine; D006918:Hydroxyurea