Delineation and mapping of Stat5 isoforms activated by granulocyte colony-stimulating factor in myeloid cells

Granulocyte colony-stimulating factor (G-CSF) is a cytokine critical for pr oliferation and differentiation of granulocytic precursors and neutrophil f unctions that has previously been demonstrated to activate Stat3 and Stat5, two members of the signal transducer and activator of transcription (STAT) protein family. Stat3 has been identified to be critical for G-CSF recepto r (G-CSFR)-mediated signaling for granulocyte differentiation. Stat5 activa tion has been mapped to the proximal portion of the cytosolic region of the G-CSFR, However, delineation and mapping of the specific Stat5 isoforms ac tivated by G-CSF in myeloid cells have not been reported. In this study, we demonstrated that G-CSF activated a Stat5 complex in human myeloid cells c ontaining three isoforms of Stat5: Stat5A, Stat5B, and Stat5 p80. Activatio n of Stat5A and Stat5B maps to the proliferation-specific domain of the C-C SFR, whereas Stat5 p80 is recruited by phosphotyrosine-704 within the regio n of G-CSFR required for differentiation. G-CSF-activated Stat5A/B, but not Stat5 p80, formed a heterodimer with Stat3. The Stat5A/B-Stat3 heterodimer can bind to specific DNA sequences preferred by both Stat3 and Stat5. Thes e findings are consistent with the possibility that Stat5 p80 contributes t o G-CSF-induced myeloid differentiation. (C) 2000 Academic Press.