Internalization of glycosyl-phosphatidylinositol (GPI)-anchored lymphocyte proteins. II. GPI-anchored and transmembrane molecules internalize through distinct pathways.
Ly-6A.2 (T cell-activating protein, TAP) and Thy-1 are glycosyl-phosphatidyl-inositol (GPI)-anchored proteins expressed on the surface of murine T lymphocytes. We have found that Ly-6A.2 (TAP) and Thy-1 are internalized by T cells. In the present study we have investigated whether these GPI-anchored proteins enter cells by endocytosis through coated pits. Two lines of evidence argue against the involvement of coated pits in the internalization of Ly-6A.2 (TAP) and Thy-1. First, drugs that effectively blocked the endocytosis of transferrin receptor and H-2 class I molecules, (which are known to be internalized via coated pits) did not inhibit the internalization of the GPI-anchored proteins. Second, in ultrastructural analyses, Ly-6A2 (TAP) and Thy-1, in contrast to the transferrin receptor, were rarely found in coated pits or vesicles. These observations suggest that the GPI-anchored proteins on T lymphocytes are internalized by a distinct pathway that does not involve endocytosis through coated pits.
Harvard Medical School, Department of Pathology, Boston, MA.
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Bamezai
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Goldmacher
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Rock
D000818:Animals; D000950:Antigens, Ly / Q000378:metabolism; D000954:Antigens, Surface / Q000378:metabolism; D002460:Cell Line; D005033:Ethylmaleimide / Q000494:pharmacology; D006017:Glycolipids / Q000378:metabolism*; D017261:Glycosylphosphatidylinositols; D006183:H-2 Antigens / Q000378:metabolism; D007700:Kinetics; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D010716:Phosphatidylinositols / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000502:physiology; D018160:Receptors, Cytoplasmic and Nuclear; D011990:Receptors, Transferrin / Q000378:metabolism; D013601:T-Lymphocytes / Q000378:metabolism*; D018800:Thy-1 Antigens
D000950:Antigens, Ly; D000954:Antigens, Surface; D006017:Glycolipids; D017261:Glycosylphosphatidylinositols; D006183:H-2 Antigens; D008565:Membrane Proteins; D010716:Phosphatidylinositols; D011956:Receptors, Cell Surface; D018160:Receptors, Cytoplasmic and Nuclear; D011990:Receptors, Transferrin; D018800:Thy-1 Antigens; C040985:phosphatidylinositol receptors; D005033:Ethylmaleimide