title: Protein-tyrosine kinase-dependent activation of STAT transcription factors in interleukin-2- or interleukin-4-stimulated T lymphocytes.
abstract: The proliferation of activated T lymphocytes is critically dependent on the binding of the T-cell growth factors, interleukin (IL)-2 and IL-4, to distinct but evolutionarily related cell surface receptors. Previous results suggest that the IL-2 receptor (IL-2R) and IL-4R are coupled to both overlapping and distinct intracellular signaling pathways in T lymphocytes. In this study, we demonstrate that activation of Janus tyrosine kinases (JAKs) and STAT transcription factors is rapidly induced by exposure of factor-dependent murine T-cell lines to IL-2 or IL-4. Both IL-2 and IL-4 stimulated the rapid activation of JAK1 and JAK3, whereas JAK2 activity was unaffected by either cytokine. These responses were accompanied by the appearance in cell nuclei of 3 DNA binding activities that recognized a high-affinity binding site for STAT factors. In transient transfection assays, this STAT factor target sequence conferred IL-2 and IL-4 inducibility on a synthetic luciferase reporter gene. Antibody supershifting experiments indicated that IL-2 induces the formation of STAT dimers containing STAT3 and STAT1 alpha. Although IL-4 also activated STAT1 alpha, the major IL4-induced STAT factor is not STAT3 and remains undefined. Pretreatment of the T-cells with the protein-tyrosine kinase inhibitor herbimycin A blocked both the nuclear translocation of STAT factors and STAT-dependent reporter gene transcription. Immunoblot analyses confirmed that cytoplasmic STAT3 was heavily phosphorylated on tyrosine in IL-2-stimulated cells, and that phosphorylated STAT3 appeared in the nuclei of these cells. These results indicate that identical JAKs and partially overlapping sets of STATs are activated by IL-2 and IL-4 in T lymphocytes.
authors.affiliation: Department of Pharmacology, Mayo Clinic, Rochester, Minnesota 55905, USA.
authors.forename: G J
authors.initials: GJ
authors.lastname: Brunn
authors.forename: E L
authors.initials: EL
authors.lastname: Falls
authors.forename: A E
authors.initials: AE
authors.lastname: Nilson
authors.forename: R T
authors.initials: RT
authors.lastname: Abraham
mesh_terms: D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006801:Humans; D007376:Interleukin-2 / Q000494:pharmacology*; D015847:Interleukin-4 / Q000494:pharmacology*; D053613:Janus Kinase 1; D053614:Janus Kinase 2; D053616:Janus Kinase 3; D008156:Luciferases / Q000096:biosynthesis; D051379:Mice; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000494:pharmacology; D050796:STAT3 Transcription Factor; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D014162:Transfection
chemical_list: D004268:DNA-Binding Proteins; D007376:Interleukin-2; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; C494087:Stat3 protein, mouse; D015534:Trans-Activators; D014157:Transcription Factors; D015847:Interleukin-4; D008156:Luciferases; D011505:Protein-Tyrosine Kinases; C507904:JAK1 protein, human; C507924:JAK2 protein, human; C507933:JAK3 protein, human; C507905:Jak1 protein, mouse; C507926:Jak2 protein, mouse; C507935:Jak3 protein, mouse; D053613:Janus Kinase 1; D053614:Janus Kinase 2; D053616:Janus Kinase 3