Granulocyte colony-stimulating factor-induced activation of protein kinase-C in myeloid cells

Abstract

Granulocyte colony stimulating factor (G-CSF) regulates survival, proliferation, differentiation, and activation of myeloid cells. It binds to a high affinity receptor (G-CSF-R) expressed on myeloid cells, for which the signal transduction mechanisms other than protein tyrosine kinase (PTK) activation have not been completely identified. We explored the potential involvement of protein kinase-C (PKC) in G-CSF-R signal transduction. In this report, we provide direct evidence of PKC activation by G-CSF-R. G-CSF treatment of peripheral blood neutrophils, granulocytic cell lines (HL-60, NFS-60, KG-1), and monocytic cell lines (WEHI-3B,U-937) resulted in PKC activation. Chelerythrine chloride and HA-100, an isoquinolinesulfonamide derivative, the specific inhibitors of PKC, 1,2-Bis(2-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid (BAPTA), a chelator of intracellular calcium, and 3,4,5-trimethoxybenzoic acid 8-(diethylamino)-octyl ester (TMB-8), an inhibitor of intracellular calcium release, blocked G-CSF-induced PKC activation in HL-60 cells, and reduced CD11b upregulation in neutrophils, but did not affect ligand-binding or down-modulation of G-CSF-R. Methyl 2,5-dihydroxycinnamate (MDHC), a potent inhibitor of protein tyrosine kinases (PTK), also inhibited PKC activation in response to G-CSF treatment, suggesting that PKC activation may occur downstream of PTK activation. Our results demonstrate the involvement of PKC in G-CSF-R signal transduction, and suggest a common signaling pathway in myeloid cells of granulocytic and monocytic lineages.

Signal transduction pathways that contribute to myeloid differentiation

“…143 PKC is also activated following G-CSF treatment of myeloid cells, and G-CSF-induced differentiation of HL-60 cells is blocked by PKC inhibitors and calcium chelators. 144 During granulocytic differentiation of 32Dcl3 cells, PKC contributes to Ras-induced phosphorylation and activation of C/EBPa, working to drive the differentiation process. 145 ATRA treatment also leads to PKC activation.…”

Involvement of Protein Kinase Cε in the Negative Regulation of Akt Activation Stimulated by Granulocyte Colony-Stimulating Factor

“…Expressions of various PKC isoforms are strictly regulated during hemopoietic development (20,21). Although PKC pathway has been implicated in G-CSF receptor signaling (22), its biological significance remains to be determined.…”

Retinoids and myelomonocytic growth factors cooperatively activate RARΑ and induce human myeloid leukemia cell differentiation via MAP kinase pathways

“…46 In addition, various kinases such as protein kinases A and C, which can phosphorylate RARs, 29 might be activated during G/GM-CSF signaling. 47,48 It also is worth noting that the treatment of leukemic cells with ATRA may lead to up-regulation of G-CSF and GM-CSF receptor expression, thus amplifying cooperative signaling by ATRA and GFs via a positive feedback-loop mechanism. …”