title: Modulation of TCR-mediated signaling pathway by thymic shared antigen-1 (TSA-1)/stem cell antigen-2 (Sca-2).
abstract: Thymic shared antigen-1 (TSA-1) is a glycosyl-phosphatidylinositol (GPI)-anchored differentiation Ag expressed on murine lymphocytes, and is identical to stem cell Ag-2 (Sca-2). Using newly established mAb against TSA-1/Sca-2, we have previously shown that surface TSA-1 expression is induced upon activation in T cells, and that anti-TSA-1 inhibits IL-2 production induced by anti-CD3 stimulation in T cell hybridomas. In the present study, we have analyzed the functional role of TSA-1 during T cell activation using normal T cells, T cell hybridomas, and transfected Jurkat cell lines that expressed either GPI-anchored or transmembrane form of TSA-1. Anti-TSA-1 inhibited IL-2 production from normal T cells stimulated with soluble anti-CD3 plus accessory cells. Anti-TSA-1 exhibited the inhibitory effect on T cells, but not on accessory cells, because anti-TSA-1 inhibited IL-2 production in Jurkat cells transfected with TSA-1 cDNA, but not in control transfectant. A transmembrane form of TSA-1 was expressed in Jurkat cells by fusing the extracellular portion of TSA-1 to the transmembrane and cytoplasmic regions of the class 1 Db. The analysis using this transfectant revealed that anti-TSA-1-mediated inhibition of IL-2 production did not require the GPI anchor of TSA-1. Finally, in addition to the inhibition of IL-2 production, tyrosine phosphorylation of CD3 zeta-chains observed following TCR stimulation, one of the important early activation events, was markedly reduced by anti-TSA-1. These results imply that TSA-1/Sca-2 plays an important regulatory role in the TCR signaling pathway of activated T cells in addition to its role in T cell differentiation.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology; D000945:Antigens, Differentiation, T-Lymphocyte / Q000276:immunology*; D000950:Antigens, Ly / Q000276:immunology*; D001483:Base Sequence; D017252:CD3 Complex / Q000276:immunology; D017261:Glycosylphosphatidylinositols / Q000502:physiology; D006825:Hybridomas / Q000276:immunology; D007376:Interleukin-2 / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D008565:Membrane Proteins / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D011506:Proteins / Q000276:immunology*; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D013601:T-Lymphocytes / Q000276:immunology; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D000911:Antibodies, Monoclonal; D000945:Antigens, Differentiation, T-Lymphocyte; D000950:Antigens, Ly; D017252:CD3 Complex; D017261:Glycosylphosphatidylinositols; D007376:Interleukin-2; D008565:Membrane Proteins; D011506:Proteins; D011948:Receptors, Antigen, T-Cell; C084839:thymic shared antigen-1