Normal neutrophil maturation is associated with selective loss of MAP kinase activation by G-CSF.
Although both GM-CSF and G-CSF activate p42/44 MAPK in neutrophil progenitors, the ability of G-CSF to cause MAPK activation is lost in mature neutrophils, while GM-CSF exposure still causes activation. The mechanism of this differential effect related to maturation status has not been explored. We verified that G-CSF and GM-CSF receptors remain functional on purified mature neutrophils by demonstrating that both cytokines caused phosphorylation of STAT3. However, only GM-CSF was capable of activating MAPK as assessed by gel shift and in vitro kinase assay. Both G-CSF and GM-CSF caused activation of p21 ras in neutrophils, demonstrating that early events in the ras-MAPK pathway remain functional after stimulation by either cytokine. Inhibition of tyrosine phosphatase activity by pervanadate restored the ability of G-CSF to activate MAPK in mature neutrophils. Specific inhibition of the SHP-1 phosphatase, known to be activated by G-CSF but not GM-CSF also restored the ability of G-CSF to activate MAPK in neutrophils. These studies suggest that G-CSF activation of SHP-1 may be an important regulatory step for permitting optimal terminal differentiation during neutrophil production and add to our knowledge of the instructional role of G-CSF and GM-CSF for balancing proliferation and differentiation of neutrophil progenitor cells. This information may prove useful for the understanding of conditions in which neutrophil proliferative/differentiative balancing is dysregulated, such as myeloid leukemia and myelodysplastic disorders.
Baumann
Michael
M
Research Service, Department of Veterans Affairs, Medicine 111W, VAMC, 4100 W. Third Street, Dayton, OH 45428, USA. michael.baumann@wright.edu
Frye
Tricia
T
Naqvi
Tahir
T
Gomez-Cambronero
Julian
J
D002454:Cell Differentiation; D015536:Down-Regulation; D004789:Enzyme Activation; D016179:Granulocyte Colony-Stimulating Factor / Q000378:metabolism / Q000494:pharmacology*; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D020928:Mitogen-Activated Protein Kinases / Q000096:biosynthesis*; D009504:Neutrophils / Q000378:metabolism / Q000502:physiology*; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors; D015398:Signal Transduction; D014638:Vanadates / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases
C076715:pervanadate; D016179:Granulocyte Colony-Stimulating Factor; D014638:Vanadates; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D017027:Protein Tyrosine Phosphatases