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-μ). Stimulation of B cells by anti-μ 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-μ. Maximal stimulation of N-glycosylation activity was observed at an anti-μ concentration of 20-50 μg/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-μ in a serumfree medium, or by activating with anti-μ 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.
|Number of pages
|Archives of Biochemistry and Biophysics
|Published - Dec 1987
ASJC Scopus subject areas
- Molecular Biology