title: Isolation and characterization of a nerve growth factor-regulated Fos kinase from PC12 cells.
abstract: Nerve growth factor (NGF) treatment of PC12 cells activates a protein kinase that phosphorylates c-Fos protein at a site near its C terminus, as well as a peptide corresponding to a C-terminal region of c-Fos (Taylor, L. K., Marshak, D. R., and Landreth, G. E. (1993) Proc. Natl. Acad. Sci. U. S. A. 90, 368-372). This serine/threonine kinase, termed Fos kinase, has been purified > 24,000-fold through five column steps to near homogeneity and is shown to be a 37-kDa protein as determined by SDS-polyacrylamide gel electrophoresis (PAGE) with a pI = 6.0. Fos kinase is distinguishable from previously characterized NGF-regulated kinases by its chromatographic behavior, its response to specific kinase inhibitors, and its substrate specificity. The concentration of NGF required to activate Fos kinase is consistent with signaling from the high affinity NGF receptor. Fos kinase phosphorylates c-Fos at its C terminus as indicated by competitive inhibition with a peptide corresponding to C-terminal phosphorylation sites and lack of phosphorylation of a C-terminal deletion mutant of c-Fos. Hyperphosphorylation of c-Fos in vivo, as detected by reduced electrophoretic mobility of c-Fos, is induced by the same ligands which activate Fos kinase. Moreover, Fos kinase phosphorylation of c-Fos in vitro results in a similar electrophoretic mobility shift, demonstrating that Fos kinase may be responsible for growth factor-stimulated alterations in mobility on SDS-PAGE and phosphorylation of this transcription factor. The ability of this unique growth factor-responsive kinase to phosphorylate c-Fos at its C terminus, a region essential for the transrepressive properties of c-Fos, suggests that Fos kinase may play a role in the regulation of the transcriptional repressive activity of c-Fos.
authors.affiliation: Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106.
authors.forename: L K
authors.initials: LK
authors.lastname: Taylor
authors.forename: K D
authors.initials: KD
authors.lastname: Swanson
authors.forename: J
authors.initials: J
authors.lastname: Kerigan
authors.forename: W
authors.initials: W
authors.lastname: Mobley
authors.forename: G E
authors.initials: GE
authors.lastname: Landreth
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002412:Cations; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D009414:Nerve Growth Factors / Q000378:metabolism*; D016716:PC12 Cells; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000302:isolation & purification* / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D038744:Ribosomal Protein S6 Kinases, 90-kDa; D015398:Signal Transduction; D013347:Subcellular Fractions / Q000201:enzymology; D013379:Substrate Specificity
chemical_list: D002412:Cations; D009414:Nerve Growth Factors; D016760:Proto-Oncogene Proteins c-fos; D004815:Epidermal Growth Factor; D017346:Protein Serine-Threonine Kinases; D038744:Ribosomal Protein S6 Kinases, 90-kDa