Abstract
Nerve growth factor (NGF) is a required differentiation and survival factor for sympathetic and a majority of neural crest-derived sensory neurons in the developing vertebrate peripheral nervous system. Although much is known about the function of NGF, the intracellular signaling cascade that it uses continues to be a subject of intense study. p21 ras signaling is considered necessary for sensory neuron survival. How additional intermediates downstream or in parallel may function has not been fully understood yet. Two intracellular signaling cascades, extra cellular regulated kinase (erk) and phosphatidylinositol-3 (PI 3) kinase, transduce NGF signaling in the pheochromocytoma cell line PC12. To elucidate the role these cascades play in survival and differentiation, we used a combination of recombinant adenoviruses and chemical inhibitors to perturb these pathways in sensory neurons from wild-type mice and mice deficient for neurofibromin in which the survival and differentiation pathway is constitutively active. We demonstrate that ras activity is both necessary and sufficient for the survival of embryonic sensory neurons. Downstream of ras, however, the erk cascade is neither required nor sufficient for neuron survival or overall differentiation. Instead, the activity of PI 3 kinase is necessary for the survival of the wild-type and neurofibromin-deficient neurons. Therefore, we conclude that in sensory neurons, NGF acts via a signaling pathway, which includes both ras and PI 3 kinase.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adenoviridae / genetics
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Animals
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Cell Differentiation / drug effects
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Cell Survival / drug effects
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Cell Survival / genetics
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Cells, Cultured
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Chromones / pharmacology
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Embryo, Mammalian
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Enzyme Activation
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Gene Deletion
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MAP Kinase Kinase 1
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Mice
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Mice, Neurologic Mutants
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Mitogen-Activated Protein Kinase Kinases*
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Mitogen-Activated Protein Kinases / metabolism
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Morpholines / pharmacology
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Nerve Tissue Proteins / genetics
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Neurofibromin 1
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Neurons, Afferent / drug effects
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Neurons, Afferent / metabolism
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Neurons, Afferent / physiology*
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Phosphatidylinositol 3-Kinases / physiology*
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Phosphoinositide-3 Kinase Inhibitors
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / physiology
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Protein-Tyrosine Kinases / genetics
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Protein-Tyrosine Kinases / physiology
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Proteins / genetics*
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Proto-Oncogene Proteins c-raf / genetics
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Proto-Oncogene Proteins c-raf / physiology
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Proto-Oncogene Proteins p21(ras) / genetics
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Proto-Oncogene Proteins p21(ras) / physiology*
Substances
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Chromones
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Morpholines
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Nerve Tissue Proteins
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Neurofibromin 1
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Phosphoinositide-3 Kinase Inhibitors
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Proteins
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2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
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Protein-Tyrosine Kinases
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Protein Serine-Threonine Kinases
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Proto-Oncogene Proteins c-raf
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Mitogen-Activated Protein Kinases
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MAP Kinase Kinase 1
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Map2k1 protein, mouse
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Mitogen-Activated Protein Kinase Kinases
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Proto-Oncogene Proteins p21(ras)