Identification of tyrosine-phosphorylated colony-stimulating factor 1 (CSF-1) receptor and a 56-kilodalton protein phosphorylated in intact human cells in response to CSF-1
✍ Scribed by Richard D. Huhn; Mary Elizabeth Cicione; A. Raymond Frackelton Jr.
- Publisher
- John Wiley and Sons
- Year
- 1989
- Tongue
- English
- Weight
- 599 KB
- Volume
- 39
- Category
- Article
- ISSN
- 0730-2312
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✦ Synopsis
Colony-stimulating factor 1 (CSF-1) selectively supports the survival, proliferation, and maturation of hemopoietic cells of the monocytehacrophage lineage. Although the cellular receptor for CSF-1, (the c-fms protein) is a protein-tyrosine kinase activated by the binding of CFS-I, the role of phosphorylation of cellular proteins in CSF-1 signal transduction is poorly understood. Therefore, we examined the CSF-1-stimulated phosphorylation of cellular proteins in human BeWo choriocarcinoma cell line (known to express the c-fms protein). BeWo cells were metabolically labeled with 32Pi, stimulated with recombinant human CSF-1, and extracted with detergent. Phosphotyrosyl proteins were isolated from detergent extracts by affinity chromatography on a highly specific antibody to phosphotyrosine. Rapid phosphorylation of 170-kd protein, followed closely by the phosphorylation of a 56-kd protein, was observed in response to CSF-1. The 170-kd phosphotyrosyl protein bound to wheat germ agglutinin and was secondarily immunoprecipitated with a specific anti-fms serum, consistent with its identity as the CSF-1 receptor. Although purified human macrophages that proliferate in culture in response to CSF-1 are not generally accessible, CSF-1 did stimulate the phosphorylation of a 56-kd protein in intact mononuclear leukocytes from human peripheral blood. Thus, the BeWo cell line may represent a good model for the study of CSF-1-stimulated cellular protein phosphorylation.