Regulation of urokinase plasminogen activator gene transcription in the RAW264 murine macrophage cell line by macrophage colony-stimulating factor (CSF-1) is dependent upon the level of cell-surface receptor.
Macrophage colony-stimulating factor (CSF-1) binds to a receptor (CSF-1R) encoded by the c-fms proto-oncogene and activates transcription of the urokinase plasminogen activator (uPA) gene in murine bone-marrow-derived macrophages. This article demonstrates that the murine macrophage cell line RAW264 responds to CSF-1 with inducible phosphorylation of cytoplasmic proteins on tyrosine residues but fails to induce transcription of uPA. The defect was correlated with a selective failure to maintain CSF-1Rs on the cell surface, whereas all RAW264 cells contained abundant CSF-1Rs within the presumptive Golgi/endoplasmic reticulum compartment. Transfection with a CSF-1R expression plasmid permitted CSF-1-dependent activation of the signalling pathway targeting an Ets/AP1 (activator protein 1) element in the uPA promoter that has been shown previously to be a target of oncogenic ras and protein kinase C pathways. Mutation of the expressed CSF-1R at either Y807 or Y559, sites of receptor tyrosine phosphorylation implicated in signal transduction, reduced but did not abolish uPA promoter activation by CSF-1. Activation by mutant CSF-1R plasmids was additive; there was no evidence of mutual complementation. The results indicate that maintenance of elevated uPA transcription by CSF-1 requires new receptors emerging continuously on the cell surface. Parallel, partly redundant, signalling pathways arising from phosphorylated tyrosines on the CSF-1R activate multiple cis-acting elements on the complex uPA promoter.
Fowles
L F
LF
Department of Biochemistry, Centre for Molecular and Cellular Biology, The University of Queensland, Q4072, Australia.
Stacey
K J
KJ
Marks
D
D
Hamilton
J A
JA
Hume
D A
DA
D019943:Amino Acid Substitution; D000818:Animals; D002460:Cell Line; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D016173:Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D008264:Macrophages / Q000201:enzymology*; D051379:Mice; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D011401:Promoter Regions, Genetic; D016186:Receptor, Macrophage Colony-Stimulating Factor / Q000235:genetics / Q000502:physiology*; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection; D014568:Urokinase-Type Plasminogen Activator / Q000235:genetics*
D011994:Recombinant Proteins; D019000:Phosphotyrosine; D016173:Macrophage Colony-Stimulating Factor; D016186:Receptor, Macrophage Colony-Stimulating Factor; D014568:Urokinase-Type Plasminogen Activator