title: Glucosylceramide synthase inhibitor inhibits the action of nerve growth factor in PC12 cells.
abstract: Previous studies have shown that the ceramide analogue, D-threo-1-phenyl-2-decanoylamin-3-morpholino-propanol (D-PDMP), inhibits glucosylceramide synthase and thus leads to extensive depletion of glycosphingolipids derived from glucosyl ceramide. Our previous studies have shown that cholera toxin B subunit, which specifically binds to the cell surface ganglioside GM1, and GM1 itself can enhance the action of nerve growth factor (NGF) in responsive cells by enhancing the NGF-induced autophosphorylation of the high affinity NGF receptor, Trk. Using D-PDMP, we examined the effects of the inhibition of the biosynthesis of glycosphingolipids on intracellular NGF signaling pathway. D-PDMP was found to inhibit NGF-induced neurite outgrowth of PC12 cells. Moreover, D-PDMP clearly inhibited NGF-induced autophosphorylation of Trk and prevented the activation of phosphatidylinositol 3-kinase and mitogen-activated protein kinase, downstream targets of Trk-initiated intracellular protein kinase cascades. These effects of D-PDMP were abolished by the addition of GM1 but not by the addition of other ganglioside subspecies to the culture medium. Furthermore, the effect of D-PDMP seemed to be specific for the Trk receptor, because intracellular signaling pathway of epidermal growth factor was not affected by D-PDMP. Dimethylsphingosine and the cell-permeable analogue, C2-ceramide, did not show such a strong inhibitory effect on neurite outgrowth or on the autophosphorylation of Trk. The present results and our previous observations clearly demonstrate that Trk requires endogenous gangliosides, especially GM1, for its normal function in mediating the neurotrophic activity of NGF at least in PC12 cells.
authors.affiliation: Second Department of Internal Medicine, Division of Neurology, Faculty of Medicine, Fukui Medical University, Fukui 910-1193, Japan. mutoh@fukui-med.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Mutoh
authors.forename: A
authors.initials: A
authors.lastname: Tokuda
authors.forename: J
authors.initials: J
authors.lastname: Inokuchi
authors.forename: M
authors.initials: M
authors.lastname: Kuriyama
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D029721:Drosophila Proteins; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066246:ErbB Receptors / Q000378:metabolism; D005732:Gangliosides / Q000378:metabolism; D005964:Glucosyltransferases / Q000378:metabolism*; D006028:Glycosphingolipids / Q000378:metabolism; D019476:Insect Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008858:Microscopy, Phase-Contrast; D009025:Morpholines / Q000494:pharmacology*; D009414:Nerve Growth Factors / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects; D016716:PC12 Cells / Q000166:cytology / Q000187:drug effects; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects*; D013110:Sphingosine / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D029721:Drosophila Proteins; D004791:Enzyme Inhibitors; D005732:Gangliosides; D006028:Glycosphingolipids; D019476:Insect Proteins; D009025:Morpholines; C064769:N-acetylsphingosine; D009414:Nerve Growth Factors; C096356:trk protein, Drosophila; C033110:RV 538; D005964:Glucosyltransferases; C023246:ceramide glucosyltransferase; D019869:Phosphatidylinositol 3-Kinases; D066246:ErbB Receptors; D013110:Sphingosine