title: Glial cell line-derived neurotrophic factor-stimulated phosphatidylinositol 3-kinase and Akt activities exert opposing effects on the ERK pathway: importance for the rescue of neuroectodermic cells.
abstract: Glial cell line-derived neurotrophic factor (GDNF) plays a crucial role in rescuing neural crest cells from apoptosis during their migration in the foregut. This survival factor binds to the heterodimer GDNF family receptor alpha1/Ret, inducing the Ret tyrosine kinase activity. ret loss-of-function mutations result in Hirschsprung's disease, a frequent developmental defect of the enteric nervous system. Although critical to enteric nervous system development, the intracellular signaling cascades activated by GDNF and their importance in neuroectodermic cell survival still remain elusive. Using the neuroectodermic SK-N-MC cell line, we found that the Ret tyrosine kinase activity is essential for GDNF to induce phosphatidylinositol 3-kinase (PI3K)/Akt and ERK pathways as well as cell rescue. We demonstrate that activation of PI3K is mandatory for GDNF-induced cell survival. In addition, evidence is provided for a critical up-regulation of the ERK pathway by PI3K at the level of Raf-1. Conversely, Akt inhibits the ERK pathway. Thus, both PI3K and Akt act in concert to finely regulate the level of ERK. We found that Akt activation is indispensable for counteracting the apoptotic signal on mitochondria, whereas ERK is partially involved in precluding procaspase-3 cleavage. Altogether, these findings underscore the importance of the Ret/PI3K/Akt pathway in GDNF-induced neuroectodermic cell survival.
authors.affiliation: INSERM U 364, IFR50, Faculté de Médecine Pasteur, 06107 Nice Cedex 02, France. mograbi@unice.fr
authors.forename: B
authors.initials: B
authors.lastname: Mograbi
authors.forename: R
authors.initials: R
authors.lastname: Bocciardi
authors.forename: I
authors.initials: I
authors.lastname: Bourget
authors.forename: R
authors.initials: R
authors.lastname: Busca
authors.forename: N
authors.initials: N
authors.lastname: Rochet
authors.forename: D
authors.initials: D
authors.lastname: Farahi-Far
authors.forename: T
authors.initials: T
authors.lastname: Juhel
authors.forename: B
authors.initials: B
authors.lastname: Rossi
mesh_terms: D000730:Androstadienes / Q000494:pharmacology; D017209:Apoptosis; D015153:Blotting, Western; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D005434:Flow Cytometry; D051100:Glial Cell Line-Derived Neurotrophic Factor; D006801:Humans; D008564:Membrane Potentials; D008928:Mitochondria / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008954:Models, Biological; D009154:Mutation; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins / Q000378:metabolism* / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D011498:Protein Precursors / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors; D014162:Transfection; D014407:Tumor Cells, Cultured; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D053148:Caspase 3; D020169:Caspases; D018076:DNA, Complementary; D004791:Enzyme Inhibitors; D005419:Flavonoids; D051100:Glial Cell Line-Derived Neurotrophic Factor; D020928:Mitogen-Activated Protein Kinases; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins; D019869:Phosphatidylinositol 3-Kinases; D011498:Protein Precursors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D019908:Proto-Oncogene Proteins c-raf; D000077191:Wortmannin; C495039:GDNF protein, human; C494918:AKT1 protein, human; C505407:CASP3 protein, human; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one