title: The glycophospholipid anchor of Thy-1. Biosynthetic labeling experiments with wild-type and class E Thy-1 negative lymphomas.
abstract: The Thy-1 antigen of the surface of lymphocytes and neurons is anchored to the plasma membrane via a glycophospholipid moiety. In contrast, the Thy-1 synthesized by the class E Thy-1 negative mutant lymphoma is secreted as a hydrophilic species. The present investigation uses the approach of biosynthetic labeling to investigate further the structure of the intracellular Thy-1 of wild-type cells and the secreted Thy-1 of these mutant cells. In the wild-type cells, Thy-1 can be labeled with [3H] mannose, [3H]galactose, [3H]fucose, [3H]ethanolamine, and [3H]palmitic acid. In the latter two cases the label is recovered almost exclusively in a detergent-binding Pronase fragment of the protein. The incorporated label is in the form of [3H]ethanolamine, or [3H]palmitate and stearate, respectively. Reductive methylation of biosynthetically labeled Thy-1 and a nonradioactive sample of Thy-1 shows that [3H]ethanolamine is incorporated equally into two residues of ethanolamine, only one of which has a free amino group. A single residue of glucosamine with a free amino group is also detected. Each of the sugar precursors is incorporated with extensive conservation of chemical identity. In the class E cells, each of the labeled sugars but neither [3H]ethanolamine nor [3H]palmitate is incorporated into Thy-1. The anchor moiety therefore appears to be entirely missing, although N-linked oligosaccharide processing is essentially normal. We postulate that the anchor deficiency in the mutant cells results from a biosynthetic lesion.
mesh_terms: D000818:Animals; D000954:Antigens, Surface / Q000235:genetics; D002460:Cell Line; D019856:Ethanolamine; D004983:Ethanolamines / Q000378:metabolism; D006017:Glycolipids / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D008223:Lymphoma / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D008563:Membrane Lipids / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D051379:Mice; D009154:Mutation; D010743:Phospholipids / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D018800:Thy-1 Antigens
chemical_list: D000954:Antigens, Surface; D004983:Ethanolamines; D006017:Glycolipids; D008563:Membrane Lipids; D010743:Phospholipids; D018800:Thy-1 Antigens; D019856:Ethanolamine