Normal neutrophil maturation is associated with selective loss of MAP kinase activation by G-CSF

Abstract

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.

Shp1 function in myeloid cells

“…However, Dong et al [71] report a weak interaction between the C-terminal tail of the G-CSFR and Shp1 when overexpressed in 293T cells, which is required to limit the activation of Stat3 but not Akt or MAPK. Baumann et al [72] suggest that G-CSF signaling activates MAPK during neutrophil maturation to promote proliferation, but upregulation of Shp1 inhibits this pathway to enhance differentiation in mature neutrophils. More recently, CEACAM-1, which is an ITIM-containing receptor expressed highly on the surface of neutrophils and up-regulated upon neutrophil activation [73], has been suggested to mediate Shp1 inhibition of G-CSF signaling.…”

IL-6 Production Is Positively Regulated by Two Distinct Src Homology Domain 2-Containing Tyrosine Phosphatase-1 (SHP-1)–Dependent CCAAT/Enhancer-Binding Protein β and NF-κB Pathways and an SHP-1–Independent NF-κB Pathway in Lipopolysaccharide-Stimulated Bone Marrow-Derived Macrophages

“…Furthermore, SHP-1 has also been implicated in the regulation of the MAPK pathway in human neutrophils, brain pericytes, and the renal cortex of diabetic mice (41,42). Therefore, to examine the involvement of MAPKs pathway in LPS-induced IL-6 production, we compared the activation of MAPK family members in LPS-stimulated BMDMs derived from me/me and normal mice.…”

Impairment of SHP-1 down-regulation in the lipid rafts of human neutrophils under GM-CSF stimulation contributes to their age-related, altered functions

“…It is of note that the association was found to be strong in resting cells and was reduced during interferon-␣ (IFN-␣) stimulation of a T cell line [5]. Given the wide range of its ligand, it is likely that SHP-1 plays various roles in cells besides inhibition of cell activation, including maturation of receptors [6] and of cells such as polymorphonuclear leukocytes (PMN) or platelets [7][8][9][10][11], and that specific adaptor proteins mediate each of these roles. Moreover, it was shown that SHP-1 might be the phosphatase responsible for down-regulation of mitogenactivated protein kinase (MAPK) activation by granulocytecolony stimulating factor (G-CSF) during the course of PMN maturation [10].…”