title: Ligand-induced phosphorylation of the colony-stimulating factor 1 receptor can occur through an intermolecular reaction that triggers receptor down modulation.
abstract: Ligand-induced tyrosine phosphorylation of the human colony-stimulating factor 1 receptor (CSF-1R) could involve either an intra- or intermolecular mechanism. We therefore examined the ability of a CSF-1R carboxy-terminal truncation mutant to phosphorylate a kinase-defective receptor, CSF-1R[met 616], that contains a methionine-for-lysine substitution at its ATP-binding site. By using an antipeptide serum that specifically reacts with epitopes deleted from the enzymatically competent truncation mutant, cross-phosphorylation of CSF-1R[met 616] on tyrosine was demonstrated, both in immune-complex kinase reactions and in intact cells stimulated with CSF-1. Both in vitro and in vivo, CSF-1R[met 616] was phosphorylated on tryptic peptides identical to those derived from wild-type CSF-1R, suggesting that receptor phosphorylation on tyrosine can proceed via an intermolecular interaction between receptor monomers. When expressed alone, CSF-1R[met 616] did not undergo ligand-induced down modulation, but its phosphorylation in cells coexpressing the kinase-active truncation mutant accelerated its degradation.
authors.affiliation: Department of Tumor Cell Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105.
authors.forename: M
authors.initials: M
authors.lastname: Ohtsuka
authors.forename: M F
authors.initials: MF
authors.lastname: Roussel
authors.forename: C J
authors.initials: CJ
authors.lastname: Sherr
authors.forename: J R
authors.initials: JR
authors.lastname: Downing
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D000906:Antibodies; D000936:Antigen-Antibody Complex; D002460:Cell Line; D002478:Cells, Cultured; D003115:Colony-Stimulating Factors / Q000378:metabolism* / Q000494:pharmacology; D008024:Ligands; D010449:Peptide Mapping; D010748:Phosphopeptides / Q000302:isolation & purification; D010766:Phosphorylation; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D016184:Receptors, Colony-Stimulating Factor; D014162:Transfection; D014443:Tyrosine
chemical_list: D000596:Amino Acids; D000906:Antibodies; D000936:Antigen-Antibody Complex; D003115:Colony-Stimulating Factors; D008024:Ligands; D010748:Phosphopeptides; D011956:Receptors, Cell Surface; D016184:Receptors, Colony-Stimulating Factor; D014443:Tyrosine