Modulation of the biologic activities of IgE binding factor. VI. The activation of phospholipase by glycosylation enhancing factor.
Glycosylation enhancing factor (GEF) from rat T cells is a kallikrein-like enzyme and enhances the assembly of N-linked oligosaccharides to IgE binding factors during their biosynthesis, whereas another T cell factor, i.e., glycosylation inhibiting factor (GIF), is a fragment of phosphorylated lipomodulin (i.e., phospholipase inhibitor), which when dephosphorylated inhibits phospholipase and the glycosylation process. The two T cell factors compete with each other when they are added to normal mesenteric lymph node cells during the formation of IgE binding factors. The addition of GEF to T cell hybridoma 23A4 cell switches the cells from the formation of unglycosylated IgE binding factor to the formation of N-glycosylated IgE binding factor. However, GEF neither inactivated GIF nor inhibited the formation of GIF by the T cell hybridoma. Stimulation of the T cell hybridoma with either affinity-purified GEF or bradykinin resulted in the release of GIF from the cells. GIF released by GEF stimulation had a m.w. of approximately 15,000 and bound to monoclonal antibody against lipomodulin. GEF and bradykinin also induced normal mesenteric lymph node cells to release GIF. Incorporation of 14C-arachidonic acid into 23A4 cells, followed by stimulation of the cells with GEF, resulted in the release of 14C-arachidonate. The results suggest that lipomodulin, a phospholipase inhibitory protein, is present in lymphocytes, and indicate that GEF and bradykinin induce the activation of phospholipase by stimulating cells to release lipomodulin.
D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism; D001667:Binding, Competitive; D001798:Blood Proteins / Q000378:metabolism / Q000502:physiology*; D004789:Enzyme Activation; D006825:Hybridomas / Q000276:immunology / Q000378:metabolism; D007073:Immunoglobulin E / Q000378:metabolism*; D008198:Lymph Nodes / Q000378:metabolism; D008222:Lymphokines / Q000302:isolation & purification / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D010740:Phospholipases / Q000378:metabolism*; D029584:Prostatic Secretory Proteins; D051381:Rats; D011917:Rats, Inbred Lew
D001095:Arachidonic Acids; D001798:Blood Proteins; D008222:Lymphokines; D029584:Prostatic Secretory Proteins; C043076:beta-microseminoprotein; C011850:immunoenhancing factor; C013059:immunoglobulin-binding factors; D016718:Arachidonic Acid; D007073:Immunoglobulin E; D010740:Phospholipases