Enteric neuroblasts require the phosphatidylinositol 3-kinase/Akt/Forkhead pathway for GDNF-stimulated survival

Glial cell line-derived neurotrophic factor (GDNF)/Ret signaling is required for enteric neural crest survival, proliferation, migration and process extension, but signaling pathways that mediate enteric nervous system (ENS) precursor development are poorly understood. We therefore examined GDNF effects on immunoselected ENS precursor survival and neuronal process extension in the presence of phosphatidylinositol 3-kinase and mitogen-activated protein kinase pathway inhibitors. These studies demonstrated that GDNF promotes ENS precursor survival through phosphatidylinositol-3-kinase. Specifically, GDNF induces phosphorylation of Akt and loss of the Akt substrates FOXO1 and FOXO3a from the nucleus of ENS precursors. Furthermore, dominant negative Akt or active FOXO1 constructs promote ENS precursor cell death while a dominant negative FOXO1 construct prevents cell death. In contrast, the MAPK kinase inhibitor PD98059 did not influence ENS precursor survival or neurite extension. These data demonstrate a critical role for PI-3 kinase/Akt/FOXO signaling, but not for MAPK in ENS precursor survival and neurite extension.