A phosphatidylinositol-linkage-deficient T-cell mutant contains insulin-sensitive glycosyl-phosphatidylinositol.
Glycosyl-phosphatidylinositol molecules, acting as both signal transduction elements and membrane protein anchors, have been proposed to play a role during T-cell activation. The MVB2 cell line is a mutant, derived from the wild-type T-T hybrid YH.16.33, which has a defect in the biosynthesis of PtdIns-protein linkages. As a consequence, MVB2 mutants are defective in activation through the T-cell receptor. Despite the lack of glycosyl-PtdIns anchors in the mutant MVB2 cells, a comparison of the levels and structural features of the insulin-sensitive glycosyl-PtdIns between the MVB2 and YH.16.33 lineages indicates that both cell lines are identical in this respect. The time course for insulin-responsiveness coincides in both cell lines, with maximal hydrolysis 30 s after insulin addition. The ultimate localization of insulin-regulated glycosyl-PtdIns at the outer surface of the cell membrane is also similar. These data indicate that the glycosyl-PtdIns whose hydrolysis is regulated by insulin is not anchoring proteins at the cell surface of T-lymphocytes.
Avila
M A
MA
Instituto de Investigaciones Biomédicas, Consejo Superior de Investigaciones Cientificas, Universidad Autónoma de Madrid, Spain.
Clemente
R
R
Varela-Nieto
I
I
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D005944:Glucosamine / Q000378:metabolism; D006017:Glycolipids / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D017261:Glycosylphosphatidylinositols; D006868:Hydrolysis / Q000187:drug effects; D007295:Inositol Phosphates / Q000502:physiology; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D007457:Iodine Radioisotopes; D050356:Lipid Metabolism; D008213:Lymphocyte Activation / Q000502:physiology; D051379:Mice; D009154:Mutation; D010716:Phosphatidylinositols / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D011134:Polysaccharides / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D013601:T-Lymphocytes / Q000378:metabolism / Q000502:physiology*; D014316:Tritium
D006017:Glycolipids; D017261:Glycosylphosphatidylinositols; D007295:Inositol Phosphates; D007328:Insulin; D007457:Iodine Radioisotopes; D010716:Phosphatidylinositols; D011134:Polysaccharides; D014316:Tritium; D005944:Glucosamine