The role of STAT3 in granulocyte colony-stimulating factor-induced enhancement of neutrophilic differentiation of Me2SO-treated HL-60 cells - GM-CSF inhibits the nuclear translocation of tyrosine-phosphorylated STAT3

The role of granulocyte colony-stimulating factor (G-CSF) on neutrophilic d ifferentiation of Me2SO-treated HL-60 cells was studied. G-CSF augmented th e functional maturation of Me2SO-treated HL-60 cells in terms of both O-2(r adical anion)-generating ability and expression of the formyl-methionyl-leu cyl-phenylalanine receptor. G-CSF induced enhancement of cell growth in Me2 SO-treated HL-60 cells. These results indicate that G-CSF is a potent enhan cer for the differentiation and proliferation of Me2SO-treated HL-60 cells. G-CSF caused the activation of p70 S6 kinase but not mitogen-activated pro tein (MAP) kinase. On the other hand, G-CSF rapidly induced tyrosine phosph orylation of signal transducers and activators of transcription-3 (STAT3), but did not induce serine727 phosphorylation, From the analysis of confocal laser scanning fluorescence microscopy and differential centrifugation, it was clearly demonstrated that G-CSF induced nuclear translocation of tyros ine-phosphorylated STATE. The G-CSF-dependent enhancement of neutrophilic d ifferentiation in Me2SO-HL-60 cells was reversely inhibited by granulocyte- macrophage colony-stimulating factor (GMCSF), Notably, in the presence of G M-CSF, G-CSF induced the tyrosine phosphorylation of STATE but failed to in duce the nuclear translocation of tyrosine-phosphorylated STATE, GM-CSF ind uced activation of not only p70 S6 kinase, but also of MAP kinase, Furtherm ore, GM-CSF caused the rapid serine727 phosphorylation of STAT3, both in th e presence and absence of G-CSF, PD98059, an MEK1 inhibitor, inhibited the G-CSF-dependent serine727 phosphorylation of STAT3 and blocked the inhibito ry effect of GM-CSF on G-CSF-dependent nuclear translocation of STAT3, Thes e results suggest that G-CSF-dependent nuclear translocation of STAT3 coord inates with the promotion of neutrophilic differentiation in Me2SO-treated HL-60 cells.