PMA-induced activation of the p42/44ERK- and p38RK-MAP kinase cascades in HL-60 cells is PKC dependent but not essential for differentiation to the macrophage-like phenotype

J Cell Physiol. 1997 Dec;173(3):310-8. doi: 10.1002/(SICI)1097-4652(199712)173:3<310::AID-JCP2>3.0.CO;2-Q.


The signaling mechanisms leading to phorbol ester myristate (PMA)-induced differentiation of HL-60 cells to the macrophagelike phenotype were investigated by using different protein kinase inhibitors. The protein kinase C inhibitor Ro 31-8220 specifically blocks PMA-induced differentiation, activation of the p42/44ERK- and p38RK-MAP kinase cascades and Hsp27-phosphorylation in HL-60 cells. Because Ro 31-8220 does not inhibit activation of the MAP kinase cascades by protein kinase C (PKC)-independent signals such as epidermal growth factor (EGF), heat shock, or anisomycin in these cells, only PMA-induced activation of the MAP kinases can be downstream of PKC. The MEK1 inhibitor PD 098059 and the p38RK inhibitor SB 203580 also were used to analyze whether the PMA-induced PKC-dependent activation of MAP kinases is involved in the differentiation process. Under certain conditions, PD 098059 can completely block the PMA-induced activation of the p42ERK as monitored by immunoprecipitation kinase assay by using the substrate myelin basic protein. SB 203580 specifically inhibits activation of p38RK as judged by MAPKAP kinase 2 activity against the substrate Hsp27 and also blocks Hsp27 phosphorylation in the cells. In contrast, neither PD 098059 nor SB 203580 nor both inhibitors together prevent PMA-induced differentiation of the HL-60 cells to the macrophagelike phenotype. The results suggest the existence of a diversification of PMA-induced signaling in HL-60 cells downstream of PKC, leading to activation of MAP kinases that are not essential for differentiation and to phosphorylation of other, so far unidentified, targets responsible for differentiation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calcium-Calmodulin-Dependent Protein Kinases / metabolism*
  • Cell Differentiation
  • Enzyme Activation
  • Enzyme Inhibitors / pharmacology
  • Flavonoids / pharmacology
  • HL-60 Cells
  • Humans
  • Imidazoles / pharmacology
  • Indoles / pharmacology
  • Intracellular Signaling Peptides and Proteins
  • Macrophages / cytology
  • Macrophages / drug effects
  • Macrophages / physiology*
  • Mitogen-Activated Protein Kinase 1 / metabolism*
  • Mitogen-Activated Protein Kinases*
  • Myelin Basic Protein / metabolism
  • Protein Kinase C / metabolism*
  • Protein-Serine-Threonine Kinases / metabolism
  • Pyridines / pharmacology
  • Substrate Specificity
  • Tetradecanoylphorbol Acetate / pharmacology*
  • p38 Mitogen-Activated Protein Kinases


  • Enzyme Inhibitors
  • Flavonoids
  • Imidazoles
  • Indoles
  • Intracellular Signaling Peptides and Proteins
  • Myelin Basic Protein
  • Pyridines
  • MAP-kinase-activated kinase 2
  • Protein-Serine-Threonine Kinases
  • Protein Kinase C
  • Calcium-Calmodulin-Dependent Protein Kinases
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinases
  • p38 Mitogen-Activated Protein Kinases
  • Tetradecanoylphorbol Acetate
  • SB 203580
  • 2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one
  • Ro 31-8220