title: Growth hormone-induced alteration in ErbB-2 phosphorylation status in 3T3-F442A fibroblasts.
abstract: The growth hormone receptor (GHR), a cytokine receptor superfamily member, requires the JAK2 tyrosine kinase for signaling. We now examine functional interactions between growth hormone (GH) and epidermal growth factor (EGF) in 3T3-F442A fibroblasts. Although EGF enhanced ErbB-2 tyrosine phosphorylation, GH, while causing retardation of its migration on SDS-polyacrylamide gel electrophoresis, decreased ErbB-2's tyrosine phosphorylation. GH-induced retardation was reversed by treatment of anti-ErbB-2 precipitates with both alkaline phosphatase and protein phosphatase 2A, suggesting that GH induced serine/threonine phosphorylation of ErbB-2. Both GH-induced shift in ErbB-2 migration and GH-induced MAP kinase activation were unaffected by a protein kinase C inhibitor but were blocked by the mitogen-activated protein kinase/extracellular signal-regulated kinase kinase 1 (MEK1) inhibitor, PD98059. Notably, leukemia inhibitory factor, but not interferon-gamma, also promoted ErbB-2 shift and mitogen-activated protein kinase activation. Cotreatment with EGF and GH versus EGF alone resulted in a 35% decline in acute ErbB-2 tyrosine 1248 autophosphorylation, a marked decline (approximately 50%) in DNA synthesis, and substantially decreased cyclin D1 expression. We conclude that in 3T3-F442A cells, 1) the GH-induced decrease in ErbB-2 tyrosine phosphorylation correlates with MEK1/mitogen-activated protein kinase activity and 2) GH antagonizes EGF-induced DNA synthesis and cyclin D1 expression in a pattern consistent with its alteration in ErbB-2 phosphorylation status.
authors.affiliation: Department of Medicine, University of Alabama at Birmingham, AL 35294, USA.
authors.forename: S O
authors.initials: SO
authors.lastname: Kim
authors.forename: J C
authors.initials: JC
authors.lastname: Houtman
authors.forename: J
authors.initials: J
authors.lastname: Jiang
authors.forename: J M
authors.initials: JM
authors.lastname: Ruppert
authors.forename: P J
authors.initials: PJ
authors.lastname: Bertics
authors.forename: S J
authors.initials: SJ
authors.lastname: Frank
mesh_terms: D016475:3T3 Cells; D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D000906:Antibodies; D019938:Cyclin D1 / Q000235:genetics; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D066246:ErbB Receptors / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D006131:Growth Inhibitors / Q000494:pharmacology; D019382:Human Growth Hormone / Q000494:pharmacology*; D006801:Humans; D015850:Interleukin-6; D053614:Janus Kinase 2; D053605:Leukemia Inhibitory Factor; D008222:Lymphokines / Q000494:pharmacology; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D054648:Protein Phosphatase 2; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D011994:Recombinant Proteins / Q000494:pharmacology
chemical_list: D000469:Alkaline Phosphatase; D000906:Antibodies; D019938:Cyclin D1; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D006131:Growth Inhibitors; D019382:Human Growth Hormone; D015850:Interleukin-6; D053614:Janus Kinase 2; D053605:Leukemia Inhibitory Factor; D008222:Lymphokines; D020928:Mitogen-Activated Protein Kinases; D010749:Phosphoprotein Phosphatases; D019000:Phosphotyrosine; D054648:Protein Phosphatase 2; D011505:Protein-Tyrosine Kinases; D011518:Proto-Oncogene Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases; D011994:Recombinant Proteins; C507837:LIF protein, human; C507838:Lif protein, mouse; C507924:JAK2 protein, human; C507926:Jak2 protein, mouse