A potential role of Ras-mediated signal transduction for the enhancement of depolarization-induced Ca2+ responses in hippocampal neurons by basic fibroblast growth factor.
Chronic treatment with basic fibroblast growth factor (bFGF) increases the expression of functional L-type voltage-dependent Ca2+ channels (VDCCs) in fetal rat hippocampal neurons. We investigated the intracellular signaling mechanisms involved in this effect, using high K+ depolarization-induced elevation of intracellular Ca2+ concentrations as a measure. Genistein, a protein tyrosine kinase inhibitor, significantly attenuated the effect of bFGF. The effect of bFGF was also diminished by concurrent application of a Ras inactivator, N-acetyl-S-farnesyl-l-cysteine. In contrast, a phospholipase C inhibitor U73122, a phosphatidylinositol-3 kinase inhibitor wortmannin, Li+ which inhibits inositol phospholipid turnover, or a protein kinase inhibitor calphostin C did not inhibit the effect of bFGF. Phorbol 12-myristate 13-acetate, a protein kinase C activator, did not mimic the effect of bFGF. On the other hand, an adenylyl cyclase activator forskolin and a cyclic AMP analog 8-Br-cyclic AMP markedly attenuated the effect of bFGF, which indicates the presence of a cyclic AMP-mediated negative regulatory mechanism, possibly the interference of Ras-Raf interaction. These results suggest that Ras-mediated signal transduction is required for the enhancement by bFGF of VDCC responses in hippocampal neurons.
Katsuki
H
H
Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan.
Shitaka
Y
Y
Saito
H
H
Matsuki
N
N
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D018692:Antimanic Agents / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology; D020864:Calcium Channels, N-Type; D002273:Carcinogens / Q000494:pharmacology; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004594:Electrophysiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology*; D006624:Hippocampus / Q000166:cytology; D018021:Lithium Chloride / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D009281:Naphthalenes / Q000494:pharmacology; D009474:Neurons / Q000737:chemistry* / Q000166:cytology / Q000201:enzymology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D011760:Pyrrolidinones / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D000077191:Wortmannin; D018631:ras Proteins / Q000378:metabolism*
D015124:8-Bromo Cyclic Adenosine Monophosphate; D000730:Androstadienes; D018692:Antimanic Agents; D002118:Calcium; D015220:Calcium Channels; D020864:Calcium Channels, N-Type; D002273:Carcinogens; D005576:Colforsin; D000242:Cyclic AMP; D004791:Enzyme Inhibitors; D004963:Estrenes; D016222:Fibroblast Growth Factor 2; D018021:Lithium Chloride; D009281:Naphthalenes; D010726:Phosphodiesterase Inhibitors; D011493:Protein Kinase C; D019908:Proto-Oncogene Proteins c-raf; D011760:Pyrrolidinones; D013755:Tetradecanoylphorbol Acetate; D000077191:Wortmannin; D018631:ras Proteins; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; C058819:calphostin C