title: Insulin-like growth factor-1-dependent maintenance of neuronal metabolism through the phosphatidylinositol 3-kinase-Akt pathway is inhibited by C2-ceramide in CAD cells.
abstract: Ceramide is a lipid second-messenger generated in response to stimuli associated with neurodegeneration that induces apoptosis, a mechanism underlying neuronal death in Parkinson's disease. We tested the hypothesis that insulin-like growth factor-1 (IGF-1) could mediate a metabolic response in CAD cells, a dopaminergic cell line of mesencephalic origin that differentiate into a neuronal-like phenotype upon serum removal, extend processes resembling neurites, synthesize abundant dopamine and noradrenaline and express the catecholaminergic biosynthetic enzymes tyrosine hydroxylase and dopamine beta-hydroxylase, and that this process was phosphatidylinositol 3-kinase (PI 3-K)-Akt-dependent and could be inhibited by C(2)-ceramide. The metabolic response was evaluated as real-time changes in extracellular acidification rate (ECAR) using microphysiometry. The IGF-1-induced ECAR response was associated with increased glycolysis, determined by increased NAD(P)H reduction, elevated hexokinase activity and Akt phosphorylation. C(2)-ceramide inhibited all these changes in a dose-dependent manner, and was specific, as it was not induced by the inactive C(2)-ceramide analogue C(2)-dihydroceramide. Inhibition of the upstream kinase, PI 3-K, also inhibited Akt phosphorylation and the metabolic response to IGF-1, similar to C(2)-ceramide. Decreased mitochondrial membrane potential occurred after loss of Akt phosphorylation. These results show that IGF-1 can rapidly modulate neuronal metabolism through PI 3-K-Akt and that early metabolic inhibition induced by C(2)-ceramide involves blockade of the PI 3-K-Akt pathway, and may compromise the first step of glycolysis. This may represent a new early event in the C(2)-ceramide-induced cell death pathway that could coordinate subsequent changes in mitochondria and commitment of neurons to apoptosis.
authors.affiliation: Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester, UK. gharboledab@unal.edu.co
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Arboleda
authors.forename: Tze-Jen
authors.initials: TJ
authors.lastname: Huang
authors.forename: Catherine
authors.initials: C
authors.lastname: Waters
authors.forename: Alex
authors.initials: A
authors.lastname: Verkhratsky
authors.forename: Paul
authors.initials: P
authors.lastname: Fernyhough
authors.forename: Rosemary M
authors.initials: RM
authors.lastname: Gibson
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D004298:Dopamine / Q000096:biosynthesis; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D004734:Energy Metabolism / Q000187:drug effects / Q000502:physiology; D006019:Glycolysis / Q000187:drug effects / Q000502:physiology; D007334:Insulin-Like Growth Factor I / Q000037:antagonists & inhibitors / Q000378:metabolism*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects / Q000502:physiology; D008636:Mesencephalon / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D009410:Nerve Degeneration / Q000378:metabolism / Q000503:physiopathology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D010300:Parkinson Disease / Q000378:metabolism / Q000503:physiopathology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology
chemical_list: D004298:Dopamine; D007334:Insulin-Like Growth Factor I; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D013110:Sphingosine; C064769:N-acetylsphingosine