title: Interactions of phosphatidylinositol kinase, GTPase-activating protein (GAP), and GAP-associated proteins with the colony-stimulating factor 1 receptor.
abstract: The interactions of the macrophage colony-stimulating factor 1 (CSF-1) receptor with potential targets were investigated after ligand stimulation either of mouse macrophages or of fibroblasts that ectopically express mouse CSF-1 receptors. In Rat-2 cells expressing the mouse CSF-1 receptor, full activation of the receptor and cellular transformation require exogenous CSF-1, whereas NIH 3T3 cells expressing mouse c-fms are transformed by autocrine stimulation. Activated CSF-1 receptors physically associate with a phosphatidylinositol (PI) 3'-kinase. A mutant CSF-1 receptor with a deletion of the kinase insert region was deficient in its ability to bind functional PI 3'-kinase and to induce PI 3'-kinase activity precipitable with antiphosphotyrosine antibodies. In fibroblasts, CSF-1 stimulation also induced the phosphorylation of the GTPase-activating protein (GAP)-associated protein p62 on tyrosine, although GAP itself was a relatively poor substrate. In contrast to PI 3'-kinase association, phosphorylation of p62 and GAP was not markedly affected by deletion of the kinase insert region. These results indicate that the kinase insert region selectively enhances the CSF-1-dependent association of the CSF-1 receptor with active PI 3'-kinase. The insert deletion mutant retains considerable transforming activity in NIH 3T3 cells (G. Taylor, M. Reedijk, V. Rothwell, L. Rohrschneider, and T. Pawson, EMBO J. 8:2029-2037, 1989). This mutant was more seriously impaired in Rat-2 cell transformation, although mutant-expressing Rat-2 cells still formed small colonies in soft agar in the presence of CSF-1. Therefore, phosphorylation of GAP and p62 through activation of the CSF-1 receptor does not result in full fibroblast transformation. The interaction between the CSF-1 receptor and PI 3'-kinase may contribute to c-fms fibroblast transformation and play a role in CSF-1-stimulated macrophages.
authors.affiliation: Division of Molecular and Developmental Biology, Samuel Lunenfeld Research Institute, Mt. Sinai Hospital, Toronto, Ontario, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Reedijk
authors.forename: X Q
authors.initials: XQ
authors.lastname: Liu
authors.forename: T
authors.initials: T
authors.lastname: Pawson
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D002872:Chromosome Deletion; D005347:Fibroblasts / Q000378:metabolism; D020690:GTPase-Activating Proteins; D006801:Humans; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D016297:Mutagenesis, Site-Directed; D019869:Phosphatidylinositol 3-Kinases; D010770:Phosphotransferases / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D016186:Receptor, Macrophage Colony-Stimulating Factor / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: D020690:GTPase-Activating Proteins; D011506:Proteins; D011994:Recombinant Proteins; D010770:Phosphotransferases; D019869:Phosphatidylinositol 3-Kinases; D016186:Receptor, Macrophage Colony-Stimulating Factor