title: Divergence in signal transduction pathways of platelet-derived growth factor (PDGF) and epidermal growth factor (EGF) receptors. Involvement of sphingosine 1-phosphate in PDGF but not EGF signaling.
abstract: Platelet-derived growth factor (PDGF) and serum, but not epidermal growth factor (EGF), stimulated sphingosine kinase activity in Swiss 3T3 fibroblasts and increased intracellular concentrations of sphingosine 1-phosphate (SPP), a sphingolipid second messenger (Olivera, A., and Spiegel, S. (1993) Nature 365, 557-560). We report herein that DL-threo-dihydrosphingosine (DHS), a competitive inhibitor of sphingosine kinase that prevents PDGF-induced SPP formation, specifically inhibited the activation of two cyclin-dependent kinases (p34(cdc2) kinase and Cdk2 kinase) induced by PDGF, but not by EGF. SPP reversed the inhibitory effects of DHS on PDGF-stimulated cyclin-dependent kinases and DNA synthesis, demonstrating that the DHS effects were mediated via inhibition of sphingosine kinase. DHS also markedly reduced PDGF-stimulated but not EGF-stimulated mitogen-activated protein kinase activity and DNA binding activity of activator protein-1. Examination of the early signaling events of PDGF action revealed that DHS did not affect PDGF-induced autophosphorylation of the growth factor receptor or phosphorylation of the SH2/SH3 adaptor protein Shc and its association with Grb2. This sphingosine kinase inhibitor did not abrogate activation of phosphatidylinositol 3-kinase by PDGF. In agreement, treatment with SPP had no effect on these responses but did, however, potently stimulate phosphorylation of Crk, another SH2/SH3 adaptor protein. Moreover, DHS inhibited PDGF-stimulated, but not EGF-stimulated, Crk phosphorylation. Thus, regulation of sphingosine kinase activity defines divergence in signal transduction pathways of PDGF and EGF receptors leading to mitogen-activated protein kinase activation.
authors.affiliation: Department of Biochemistry and Molecular Biology, Georgetown University Medical Center, Washington, D. C. 20007, USA.
authors.forename: C S
authors.initials: CS
authors.lastname: Rani
authors.forename: F
authors.initials: F
authors.lastname: Wang
authors.forename: E
authors.initials: E
authors.lastname: Fuior
authors.forename: A
authors.initials: A
authors.lastname: Berger
authors.forename: J
authors.initials: J
authors.lastname: Wu
authors.forename: T W
authors.initials: TW
authors.lastname: Sturgill
authors.forename: D
authors.initials: D
authors.lastname: Beitner-Johnson
authors.forename: D
authors.initials: D
authors.lastname: LeRoith
authors.forename: L
authors.initials: L
authors.lastname: Varticovski
authors.forename: S
authors.initials: S
authors.lastname: Spiegel
mesh_terms: D016475:3T3 Cells; D000818:Animals; D016203:CDC2 Protein Kinase / Q000378:metabolism; D042846:CDC2-CDC28 Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D066246:ErbB Receptors / Q000502:physiology*; D007700:Kinetics; D008246:Lysophospholipids; D051379:Mice; D019869:Phosphatidylinositol 3-Kinases; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D017479:Receptors, Platelet-Derived Growth Factor / Q000502:physiology*; D015290:Second Messenger Systems / Q000187:drug effects; D015398:Signal Transduction; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D018808:Transcription Factor AP-1 / Q000378:metabolism; D000099157:Sphingosine Kinase
chemical_list: D016203:CDC2 Protein Kinase; D042846:CDC2-CDC28 Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D004247:DNA; D004791:Enzyme Inhibitors; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D008246:Lysophospholipids; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D010982:Platelet-Derived Growth Factor; D017346:Protein Serine-Threonine Kinases; D017479:Receptors, Platelet-Derived Growth Factor; D013110:Sphingosine; D018808:Transcription Factor AP-1; D000099157:Sphingosine Kinase; C060506:sphingosine 1-phosphate; C495893:Cdk2 protein, mouse; C005682:safingol