title: Mitogenic effect of glial cell line-derived neurotrophic factor is dependent on the activation of p70S6 kinase, but independent of the activation of ERK and up-regulation of Ret in SH-SY5Y cells.
abstract: Glial cell line-derived neurotrophic factor (GDNF) activates c-Ret tyrosine kinase and several downstream intracellular pathways; the biological effects caused by the activation of each of these pathways, however, remain to be elucidated. Here we report the ability of GDNF to induce proliferation, rather than differentiation, of neuroblastoma cells (SH-SY5Y) by targeting the signaling pathway responsible for mediating this proliferative effect. GDNF induces the phosphorylation of Akt and p70S6 kinase (p70S6K) in SH-SY5Y cells in which Ret protein expression is relatively low. Interestingly, treating SH-SY5Y cells with retinoic acid greatly increases Ret protein levels and GDNF-induced Ret tyrosine phosphorylation, but does not affect the mitogenic action of GDNF and the activation of the Akt/p70S6K pathway. In contrast, the activation of the ERK pathway and the resulting induction of immediate-early genes parallel the increases in Ret protein levels. Rapamycin, a specific inhibitor of p70S6K activation by the mammalian target of rapamycin, completely prevents GDNF-induced proliferation and activation of p70S6K. These results suggest that GDNF promotes cell proliferation via the activation of p70S6K, independent of the ERK signaling pathway, and that GDNF activates the Akt/p70S6K pathway more efficiently than the ERK pathway in the cells in which Ret expression is low.
authors.affiliation: Department of Biomolecular Science, Faculty of Engineering, Gifu University, 1-1 Yanagido, 501-1193, Gifu, Japan. yoko@biomol.gifu-u.ac.jp
authors.forename: Yoko
authors.initials: Y
authors.lastname: Hirata
authors.forename: Kazutoshi
authors.initials: K
authors.lastname: Kiuchi
mesh_terms: D015153:Blotting, Western; D001932:Brain Neoplasms / Q000378:metabolism; D002455:Cell Division; D002460:Cell Line; D004789:Enzyme Activation / Q000187:drug effects; D051100:Glial Cell Line-Derived Neurotrophic Factor; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008934:Mitogens / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D009414:Nerve Growth Factors / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D009447:Neuroblastoma / Q000378:metabolism; D011233:Precipitin Tests; D020133:Reverse Transcriptase Polymerase Chain Reaction; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D015398:Signal Transduction / Q000502:physiology; D020123:Sirolimus / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D015854:Up-Regulation / Q000235:genetics*
chemical_list: C495039:GDNF protein, human; D051100:Glial Cell Line-Derived Neurotrophic Factor; D007166:Immunosuppressive Agents; D008934:Mitogens; D009414:Nerve Growth Factors; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D020928:Mitogen-Activated Protein Kinases; D020123:Sirolimus