GRANULOCYTE-COLONY-STIMULATING FACTOR-INDUCED ACTIVATION OF PROTEIN-KINASE-C IN MYELOID CELLS

Granulocyte colony stimulating factor (G-CSF) regulates survival, prol iferation, 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 k inase (PTK) activation have not been completely identified. We explore d the potential involvement of protein kinase-C (PKC) in G-CSF-R signa l transduction. In this report, we provide direct evidence of PKC acti vation by G-CSF-R. G-CSF treatment of peripheral blood neutrophils, gr anulocytic 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 inhibitor s of PKC, 2-Bis(2-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid (BAP TA), a chelator of intracellular calcium, and 3,4,5-trimethoxybenzoic acid 8-(diethylamino)-ortyl ester (TMB-8), an inhibitor of intracellul ar calcium release, blocked G-CSF-induced PKC activation in HL-60 cell s, and reduced CD11b upregulation in neutrophils, but did not affect l igand-binding or down-modulation of G-CSF-R. Methyl 2,5-dihydroxycinna mate (MDHC), a potent inhibitor of protein tyrosine kinases (PTK), als o inhibited PKC activation in response to G-CSF treatment, suggesting that PKC activation may occur downstream of PTK activation. Our result s demonstrate the involvement of PKC in G-CSF-R signal transduction, a nd suggest a common signaling pathway in myeloid cells of granulocytic and monocytic lineages. (C) 1997 Wiley-Liss, Inc.