Abstract
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.
Original language | English |
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Pages (from-to) | 313-20 |
Number of pages | 8 |
Journal | Biochemical Journal |
Volume | 347 Pt 1 |
Publication status | Published - 1 Apr 2000 |
Keywords / Materials (for Non-textual outputs)
- Amino Acid Substitution
- Animals
- Cell Line
- Gene Expression Regulation, Enzymologic
- Macrophage Colony-Stimulating Factor
- Macrophages
- Mice
- Mutagenesis, Site-Directed
- Phosphorylation
- Phosphotyrosine
- Promoter Regions, Genetic
- Receptor, Macrophage Colony-Stimulating Factor
- Recombinant Proteins
- Signal Transduction
- Transcription, Genetic
- Transfection
- Urokinase-Type Plasminogen Activator