Abstract
The serine/threonine kinase RAF-1 is phosphorylated in intact macrophages in response to CSF-1 at 37°C The augmented phosphorylation of RAF-1 and a concomitant increase in RAF-1 associated serine/threonine kinase activity are kinetically later events than CSF-1 induced protein tyrosine phosphorylation. Furthermore, phosphoamino acid analysis of RAF-1 reveals the presence of phosphoserine, trace amounts of phosphothreonine but no phosphotyrosine and the phosphorylated RAF-1 does not react with anti-phosphotyrosine antibodies. In contrast to CSF-1 induced protein tyrosine phosphorylation, RAF-1 phosphorylation and activation are temperature dependent and do not occur at 4°C. Furthermore, coprecipitation experiments failed to reveal any non-covalent association of RAF-1 with the CSF-1 receptor. Thus, while RAF-1 is not a direct substrate for the CSF-1 receptor tyrosine kinase in vivo, its temperature dependent phosphorylation and activation represent an intriguing aspect of the CSF-1 response.
Original language | English (US) |
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Pages (from-to) | 3649-3657 |
Number of pages | 9 |
Journal | EMBO Journal |
Volume | 9 |
Issue number | 11 |
State | Published - 1990 |
Keywords
- CSF-1
- Growth factor receptors
- PDGF
- RAF-1 kinase
- Signal transduction
ASJC Scopus subject areas
- General Immunology and Microbiology
- General Biochemistry, Genetics and Molecular Biology
- Molecular Biology
- General Neuroscience