title: The activation of the Jak-STAT 1 signaling pathway by IL-5 in eosinophils.
abstract: The intracellular signal transduction of IL-5 in eosinophils is unknown. The objective of this study was to investigate the involvement of the newly discovered Jak-STAT pathway in the IL-5 signal transduction mechanism. Eosinophils were purified from peripheral blood by discontinuous Percoll gradients and stimulated with IL-5. The involvement of Jak 2 was investigated by immunoprecipitation followed by immunoblotting for tyrosine phosphorylation. The activation of Jak 2 was studied by autophosphorylation of the immunoprecipitated kinase. Jak 2 was tyrosine phosphorylated within 1 to 3 min after stimulation of eosinophils with IL-5. Further, the immunoprecipitated Jak 2 obtained from IL-5-stimulated cells underwent autophosphorylation. Jak 2 coprecipitated with the beta-subunit of the IL-5 receptor, suggesting a physical association of the kinase with the receptor. The nuclear factor STAT-1 (p91) was investigated by immunoprecipitation followed by immunoblotting for tyrosine phosphorylation. STAT-1 was tyrosine phosphorylated within 15 min of IL-5 stimulation. The presence of STAT-1 in the nuclear extract was studied by electrophoretic mobility shift assay. IL-5 induced two proteins that bound to the gamma-activating sequence. In the presence of an anti-STAT-1 Ab, the band was supershifted. Thus, we demonstrated that IL-5 activated the Jak 2-STAT 1 signaling pathway in eosinophils. We speculate that the Jak 2-STAT 1 pathway may be involved in the activation of IL-5-inducible genes in eosinophils.
authors.affiliation: Department of Internal Medicine, University of Texas Medical Branch, Galveston 77555, USA.
authors.forename: K
authors.initials: K
authors.lastname: Pazdrak
authors.forename: S
authors.initials: S
authors.lastname: Stafford
authors.forename: R
authors.initials: R
authors.lastname: Alam
mesh_terms: D001483:Base Sequence; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000502:physiology*; D004804:Eosinophils / Q000502:physiology*; D006801:Humans; D015151:Immunoblotting; D015848:Interleukin-5 / Q000502:physiology*; D053614:Janus Kinase 2; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011233:Precipitin Tests; D011505:Protein-Tyrosine Kinases / Q000502:physiology*; D011518:Proto-Oncogene Proteins; D050794:STAT1 Transcription Factor; D015398:Signal Transduction / Q000502:physiology*; D015534:Trans-Activators / Q000502:physiology*
chemical_list: D004268:DNA-Binding Proteins; D015848:Interleukin-5; D011518:Proto-Oncogene Proteins; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D015534:Trans-Activators; D011505:Protein-Tyrosine Kinases; C507924:JAK2 protein, human; D053614:Janus Kinase 2