THE ACTIVATION OF THE JAK2 STAT5 PATHWAY IS COMMONLY INVOLVED IN SIGNALING THROUGH THE HUMAN IL-5 RECEPTOR/

The JAK (Janus kinase) family of protein tyrosine kinases and the STAT s (signal transducers and activators of transcription) have been shown to be activated in response to a number of cytokines and growth facto rs. In this study, we evaluated the activation of JAK/STAT pathway upo n human interleukin-5 (hIL-5) stimulation of two different hIL-5-respo nsive cell lines, hIL-5 receptor a-subunit (hIL-5Ra) cDNA-transfected TF1 (TF-h5R alpha) and butyric-acid-treated YY-1 (YY-Bu), and peripher al eosinophils. Immunoprecipitation and electrophoretic mobility shift analysis revealed that tyrosine phosphorylation of JAK2 and activatio n of STAT5 were induced upon stimulation with hIL-5 in all three cell types, while STAT1 activation was only observed in eosinophils. These results indicate that JAK2/STAT5 activation is a common JAK/STAT pathw ay for hIL-5-mediated signal in these cells.