title: Phosphorylation of the human leukemia inhibitory factor (LIF) receptor by mitogen-activated protein kinase and the regulation of LIF receptor function by heterologous receptor activation.
abstract: We used a bacterially expressed fusion protein containing the entire cytoplasmic domain of the human leukemia inhibitory factor (LIF) receptor to study its phosphorylation in response to LIF stimulation. The dose- and time-dependent relationships for phosphorylation of this construct in extracts of LIF-stimulated 3T3-L1 cells were superimposable with those for the stimulation of mitogen-activated protein kinase (MAPK). Indeed, phosphorylation of the cytoplasmic domain of the low-affinity LIF receptor alpha-subunit (LIFR) in Mono Q-fractionated, LIF-stimulated 3T3-L1 extracts occurred only in those fractions containing activated MAPK; Ser-1044 served as the major phosphorylation site in the human LIFR for MAPK both in agonist-stimulated 3T3-L1 lysates and by recombinant extracellular signal-regulated kinase 2 in vitro. Expression in rat H-35 hepatoma cells of LIFR or chimeric granulocyte-colony-stimulating factor receptor (G-CSFR)-LIFR mutants lacking Ser-1044 failed to affect cytokine-stimulated expression of a reporter gene under the control of the beta-fibrinogen gene promoter but eliminated the insulin-induced attenuation of cytokine-stimulated gene expression. Thus, our results identify the human LIFR as a substrate for MAPK and suggest a mechanism of heterologous receptor regulation of LIFR signaling occurring at Ser-1044.
authors.affiliation: Department of Pharmacology, University of Washington, Seattle 98195, USA.
authors.forename: W P
authors.initials: WP
authors.lastname: Schiemann
authors.forename: L M
authors.initials: LM
authors.lastname: Graves
authors.forename: H
authors.initials: H
authors.lastname: Baumann
authors.forename: K K
authors.initials: KK
authors.lastname: Morella
authors.forename: D P
authors.initials: DP
authors.lastname: Gearing
authors.forename: M D
authors.initials: MD
authors.lastname: Nielsen
authors.forename: E G
authors.initials: EG
authors.lastname: Krebs
authors.forename: N M
authors.initials: NM
authors.lastname: Nathanson
mesh_terms: D016475:3T3 Cells; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D006131:Growth Inhibitors / Q000378:metabolism*; D006801:Humans; D015850:Interleukin-6; D053605:Leukemia Inhibitory Factor; D053680:Leukemia Inhibitory Factor Receptor alpha Subunit; D008222:Lymphokines / Q000378:metabolism*; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D051381:Rats; D018121:Receptors, Cytokine / Q000378:metabolism*; D053606:Receptors, OSM-LIF; D014407:Tumor Cells, Cultured
chemical_list: D006131:Growth Inhibitors; D015850:Interleukin-6; C507837:LIF protein, human; C507840:LIFR protein, human; D053605:Leukemia Inhibitory Factor; D053680:Leukemia Inhibitory Factor Receptor alpha Subunit; C507838:Lif protein, mouse; C507841:Lifr protein, mouse; C507842:Lifr protein, rat; D008222:Lymphokines; D018121:Receptors, Cytokine; D053606:Receptors, OSM-LIF; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases