Granulocyte-macrophage colony-stimulating factor induces transcriptional activation of Egr-1 in murine peritoneal macrophages.
Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a pleiotropic hematopoietic growth factor that induces both growth and differentiation of tissue macrophages. The subcellular mechanism of action of GM-CSF is unknown. We have examined the effect of GM-CSF on the immediate early response gene, Egr-1, in murine peritoneal macrophages. Our data demonstrate that recombinant GM-CSF (25 units/ml) produces a 12-fold increase in Egr-1 mRNA within 30 min. Pretreatment with cycloheximide (10 micrograms/ml) had no effect on the ability of GM-CSF to increase Egr-1 mRNA. In nuclear runoff studies, GM-CSF increased the transcription rate of Egr-1 by 10-fold at 10 min. The maximal effect on Egr-1 transcription occurred at 25 min (13-fold) and decreased by 45 min. The half-life of Egr-1 mRNA in GM-CSF-treated macrophages is 13-21 min. We were unable to calculate the half-life in control cells, however, because of the short half-life and low level of constitutive expression of Egr-1 mRNA. Endogenous protein kinase C activity in macrophages was depleted by treatment with 12-O-tetradecanoylphorbol-13-acetate for 24 h. GM-CSF increased Egr-1 mRNA in protein kinase C-depleted macrophages, whereas the stimulatory effect of 12-O-tetradecanoylphorbol-13-acetate on Egr-1 was blocked. These data show that GM-CSF rapidly increases transcription of Egr-1 mRNA. The effect of GM-CSF on Egr-1 mRNA does not require de novo protein synthesis or protein kinase C. These findings provide a basis for investigating the molecular mechanism of action of GM-CSF in tissue macrophages.
Liu
J W
JW
Department of Internal Medicine, Yale University School of Medicine, West Haven, Connecticut.
Lacy
J
J
Sukhatme
V P
VP
Coleman
D L
DL
D000818:Animals; D001483:Base Sequence; D004591:Electrophoresis, Polyacrylamide Gel; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D010529:Peritoneal Cavity / Q000166:cytology; D012333:RNA, Messenger / Q000032:analysis; D011994:Recombinant Proteins / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects*
D012333:RNA, Messenger; D011994:Recombinant Proteins; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D013755:Tetradecanoylphorbol Acetate