title: Involvement of sphingolipids metabolites in cellular proliferation modulated by ganglioside GM1.
abstract: The B subunit of cholera toxin, which binds specifically to ganglioside GM1, is mitogenic for quiescent Swiss 3T3 fibroblasts. Recently, sphingolipids metabolites, ceramide, sphingosine and sphingosine-1-phosphate, have been implicated as second messengers in cell growth regulation and differentiation. In this paper, we examined the possibility that interaction of the B subunit with membrane GM1 leads to alterations in metabolism of glycosphingolipids and that increased levels of sphingolipids metabolites may mediate the biological effects of the B subunit. While the B subunit did not induce a change in the level of ceramide or sphingosine, the level of sphingosine-1-phosphate was rapidly and transiently increased. The B subunit also transiently activated cytosolic sphingosine kinase activity, which catalyzes the phosphorylation of the primary hydroxyl group of sphingosine to produce sphingosine-1-phosphate. To determine whether the increase in sphingosine-1-phosphate level plays a role in B subunit-induced mitogenicity, we used a competitive inhibitor of sphingosine kinase, D,L-threo-dihydrosphingosine. D,L-thereo-Dihydrosphingosine not only inhibited B subunit-induced DNA synthesis by 26%, it also reduced its ability to stimulate DNA-binding activity of the transcription factor AP-1. This sphingosine kinase inhibitor also inhibited B subunit-induced increases in the activity of cell cycle-regulated, cyclin-dependent serine/threonine kinases, cdk2 and p34cdc2. These findings suggest that sphingosine-1-phosphate may play a role in the signal transduction pathways activated by binding of the B subunit to endogenous ganglioside GM1.
authors.affiliation: Department of Biochemistry and Molecular Biology, Georgetown University Medical Center, Washington, DC 20007, USA.
authors.forename: F
authors.initials: F
authors.lastname: Wang
authors.forename: N E
authors.initials: NE
authors.lastname: Buckley
authors.forename: A
authors.initials: A
authors.lastname: Olivera
authors.forename: K A
authors.initials: KA
authors.lastname: Goodemote
authors.forename: Y
authors.initials: Y
authors.lastname: Su
authors.forename: S
authors.initials: S
authors.lastname: Spiegel
mesh_terms: D016475:3T3 Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D001667:Binding, Competitive; D016203:CDC2 Protein Kinase / Q000187:drug effects / Q000378:metabolism; D042846:CDC2-CDC28 Kinases; D002455:Cell Division / Q000187:drug effects / Q000502:physiology*; D002518:Ceramides / Q000378:metabolism; D002772:Cholera Toxin / Q000378:metabolism / Q000494:pharmacology; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases / Q000187:drug effects / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005677:G(M1) Ganglioside / Q000276:immunology / Q000378:metabolism*; D008246:Lysophospholipids; D051379:Mice; D008934:Mitogens / Q000378:metabolism / Q000494:pharmacology; D010446:Peptide Fragments / Q000378:metabolism / Q000494:pharmacology; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000187:drug effects / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000187:drug effects / Q000378:metabolism; D013107:Sphingolipids / Q000378:metabolism*; D013110:Sphingosine / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D018808:Transcription Factor AP-1 / Q000378:metabolism; D000099157:Sphingosine Kinase
chemical_list: D000906:Antibodies; D016203:CDC2 Protein Kinase; D042846:CDC2-CDC28 Kinases; D002518:Ceramides; D002772:Cholera Toxin; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D004247:DNA; D004791:Enzyme Inhibitors; D004815:Epidermal Growth Factor; D005677:G(M1) Ganglioside; D008246:Lysophospholipids; D008934:Mitogens; D010446:Peptide Fragments; D017853:Phosphotransferases (Alcohol Group Acceptor); D010982:Platelet-Derived Growth Factor; D017346:Protein Serine-Threonine Kinases; D013107:Sphingolipids; D013110:Sphingosine; D013755:Tetradecanoylphorbol Acetate; D018808:Transcription Factor AP-1; D000099157:Sphingosine Kinase; C084765:cholera toxin B subunit (50-75); C060506:sphingosine 1-phosphate; C495893:Cdk2 protein, mouse; C005682:safingol