title: Effect of tunicamycin on release of macromolecules and tumor antigens by human melanoma cells.
abstract: Tunicamycin, an inhibitor of glycosylation, was used to examine whether glycosylation is required for shedding of tumor antigens and other macromolecules by human melanoma cells. Cellular proteins were labeled with [35S]methionine, glycoproteins with [14C]glucosamine, and external surface components with 125I by the lactoperoxidase method; 0.5 and 2.5 microgram tunicamycin/ml effectively inhibited glycosylation without significantly reducing protein synthesis. We found that release of labeled macromolecules in the presence or absence of tunicamycin was similar. Tunicamycin-treated cells released 10.2% of [35S]methionine, 29.8% of [14C]glucosamine, and 57.2% of 125I-labeled macromolecules in 24 h compared to 5.5, 14.9, and 50.8%, respectively, for untreated control cells; 62.5% of the radioactivity associated with cell-surface melanoma-associated antigens defined by specific antiserum were released in 24 h as opposed to 50.4% by untreated cells. These results indicate that release of many cellular proteins, including glycoproteins, external surface proteins, and some melanoma-associated antigens, does not require glycosylation.
mesh_terms: D000951:Antigens, Neoplasm / Q000378:metabolism*; D005944:Glucosamine / Q000031:analogs & derivatives* / Q000378:metabolism; D006801:Humans; D008545:Melanoma / Q000276:immunology / Q000378:metabolism*; D058950:Melanoma-Specific Antigens; D008715:Methionine / Q000378:metabolism; D009363:Neoplasm Proteins / Q000378:metabolism*; D014415:Tunicamycin / Q000494:pharmacology*
chemical_list: D000951:Antigens, Neoplasm; D058950:Melanoma-Specific Antigens; D009363:Neoplasm Proteins; D014415:Tunicamycin; D008715:Methionine; D005944:Glucosamine