title: Involvement of Ras/MAP kinase in the regulation of Ca2+ channels in adult bullfrog sympathetic neurons by nerve growth factor.
abstract: The cellular mechanisms that underlie nerve growth factor (NGF) induced increase in Ca(2+)-channel current in adult bullfrog sympathetic B-neurons were examined by whole cell recording techniques. Cells were maintained at low density in neuron-enriched, defined-medium, serum-free tissue culture for 6 days in the presence or absence of NGF (200 ng/ml). The increase in Ba2+ current (IBa) density induced by NGF was attenuated by the RNA synthesis inhibitor cordycepin (20 microM), by the DNA transcription inhibitor actinomycin D (0.01 microgram/ml), by inhibitors of Ras isoprenylation (perillic acid 0.1-1.0 mM or alpha-hydroxyfarnesylphosphonic acid 10-100 microM), by tyrosine kinase inhibitors genistein (20 microM) or lavendustin A (1 microM), and by PD98059 (10-100 microM), an inhibitor of mitogen-activated protein kinase kinase. Inhibitors of the phosphatidylinositol 3-kinase (PI3K) pathway (wortmannin, 100 nM, or LY29400, 100 microM) were ineffective as were inhibitors of phospholipase C gamma (U73122 or neomycin, both 100 microM). The effect of NGF persisted in Ca(2+)-free medium that contained 1.8 mM Mg2+ and 2 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid. It was mimicked by a Trk antibody that was capable of inducing neurite outgrowth in explant cultures of bullfrog sympathetic ganglion. Antibodies raised against the low-affinity p75 neurotrophin receptor were ineffective in blocking the effect of NGF on IBa. These results suggest that NGF-induced increase in Ca2+ channel current in adult sympathetic neurons results, at least in part, from new channel synthesis after Trk activation of Ras and mitogen activated protein kinase by a mechanism that is independent of extracellular Ca2+.
authors.affiliation: Department of Pharmacology, University of Alberta, Edmonton, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Lei
authors.forename: W F
authors.initials: WF
authors.lastname: Dryden
authors.forename: P A
authors.initials: PA
authors.lastname: Smith
mesh_terms: D000320:Adrenergic Fibers / Q000737:chemistry / Q000187:drug effects / Q000201:enzymology*; D000367:Age Factors; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology*; D003839:Deoxyadenosines / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D019833:Genistein / Q000494:pharmacology; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D007529:Isoflavones / Q000494:pharmacology; D020929:Mitogen-Activated Protein Kinase Kinases; D009153:Mutagens / Q000494:pharmacology; D009414:Nerve Growth Factors / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051966:Phospholipase C gamma; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D011892:Rana catesbeiana; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism; D020800:Receptor, Nerve Growth Factor; D020917:Receptor, trkA; D017475:Receptors, Nerve Growth Factor / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D002118:Calcium; D015220:Calcium Channels; D003839:Deoxyadenosines; D004791:Enzyme Inhibitors; D005419:Flavonoids; D019833:Genistein; D007527:Isoenzymes; D007529:Isoflavones; D020929:Mitogen-Activated Protein Kinase Kinases; D009153:Mutagens; D009414:Nerve Growth Factors; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051966:Phospholipase C gamma; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases; D011505:Protein-Tyrosine Kinases; D011518:Proto-Oncogene Proteins; D020794:Receptor Protein-Tyrosine Kinases; D020800:Receptor, Nerve Growth Factor; D020917:Receptor, trkA; D017475:Receptors, Nerve Growth Factor; D010738:Type C Phospholipases; D018631:ras Proteins; C004742:daidzein; C058120:cordycepin; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one