Functional specificity of cytoplasmic and transmembrane tyrosine kinases: identification of 130- and 75-kilodalton substrates of c-fps/fes tyrosine kinase in macrophages.
c-fps/fes encodes a 92-kDa protein-tyrosine kinase (NCP92) that is expressed at the highest levels in macrophages. To determine if c-fps/fes can mediate the action of the colony-stimulating factor 1 (CSF-1) receptor (CSF-1R) and to identify potential targets of c-fps/fes in macrophages, we have overexpressed c-fps/fes in a CSF-1-dependent macrophage cell line. A 30- to 50-fold overexpression of c-fps/fes partially released these cells from their factor dependence by a nonautocrine mechanism, and this correlated with the tyrosine phosphorylation of two proteins of 130 and 75 kDa (P130 and P75). c-fps/fes did not cause tyrosine phosphorylation or activation of CSF-1 dependent targets, including CSF-1R, Shc, and phosphatidylinositol 3-kinase, and conversely, CSF-1 did not induce tyrosine phosphorylation of P130 and P75. P75 appears to be a novel phosphotyrosyl protein, whereas P130 cross-reacts with a known substrate of v-src. P130 and P75 may be direct substrates of c-fps/fes: P130 was tightly associated with NCP92, and the src homology 2 domain of NCP92 specifically bound phosphorylated P130 and P75 but not the CSF-1-induced phosphotyrosyl proteins, consistent with the possibility that P130 and P75 are physiological targets of c-fps/fes. We conclude that although c-fps/fes can functionally substitute for CSF-1R to a certain extent, these tyrosine kinases act largely independently of each other and that P130 and P75 are novel targets whose mechanisms of action may be unrelated to the signalling pathways utilized by receptor tyrosine kinases.
Areces
L B
LB
Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore.
Dello Sbarba
P
P
Jücker
M
M
Stanley
E R
ER
Feldman
R A
RA
D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology; D003593:Cytoplasm / Q000201:enzymology; D020690:GTPase-Activating Proteins; D006801:Humans; D007700:Kinetics; D016173:Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D008264:Macrophages / Q000378:metabolism*; D015688:Oncogene Protein pp60(v-src) / Q000378:metabolism; D010750:Phosphoproteins / Q000302:isolation & purification / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D016186:Receptor, Macrophage Colony-Stimulating Factor / Q000187:drug effects / Q000378:metabolism*; D013379:Substrate Specificity; D013816:Thermodynamics; D014162:Transfection; D015854:Up-Regulation
D020690:GTPase-Activating Proteins; D010750:Phosphoproteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; C052602:proto-oncogene protein c-fes-fps; D016173:Macrophage Colony-Stimulating Factor; D011505:Protein-Tyrosine Kinases; D016186:Receptor, Macrophage Colony-Stimulating Factor; D015688:Oncogene Protein pp60(v-src)