title: 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.
abstract: 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.
authors.affiliation: Max-Delbrück-Center for Molecular Medicine, Berlin, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Schultz
authors.forename: K
authors.initials: K
authors.lastname: Engel
authors.forename: M
authors.initials: M
authors.lastname: Gaestel
mesh_terms: D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002454:Cell Differentiation; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D018922:HL-60 Cells; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases; D004676:Myelin Basic Protein / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D013379:Substrate Specificity; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases; D000099190:MAP-Kinase-Activated Kinase 2
chemical_list: D017871:Calcium-Calmodulin-Dependent Protein Kinases; D004791:Enzyme Inhibitors; D005419:Flavonoids; D007093:Imidazoles; D007211:Indoles; D047908:Intracellular Signaling Peptides and Proteins; D019950:Mitogen-Activated Protein Kinase 1; D020928:Mitogen-Activated Protein Kinases; D004676:Myelin Basic Protein; D011493:Protein Kinase C; D017346:Protein Serine-Threonine Kinases; D011725:Pyridines; D013755:Tetradecanoylphorbol Acetate; D048051:p38 Mitogen-Activated Protein Kinases; D000099190:MAP-Kinase-Activated Kinase 2; C093642:SB 203580; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; C064758:Ro 31-8220