Enhancement of insulin-induced PI3K/Akt/GSK-3beta and ERK signaling by neuronal nicotinic receptor/PKC-alpha/ERK pathway: up-regulation of IRS-1/-2 mRNA and protein in adrenal chromaffin cells.
In cultured bovine adrenal chromaffin cells treated with nicotine (10 microm for 24 h), phosphorylation of Akt, glycogen synthase kinase-3beta (GSK-3beta) and extracellular signal-regulated kinase (ERK)1/2 induced by insulin (100 nm for 10 min) was enhanced by approximately 62%, without altering levels of these protein kinases. Nicotine produced time (> 12 h)- and concentration (EC(50) 3.6 and 13 microm)-dependent increases in insulin receptor substrate (IRS)-1 and IRS-2 levels by approximately 125 and 105%, without altering cell surface density of insulin receptors. In these cells, insulin-induced tyrosine phosphorylation of IRS-1/IRS-2 and recruitment of phosphoinositide 3-kinase (PI3K) to IRS-1/IRS-2 were augmented by approximately 63%. The increase in IRS-1/IRS-2 levels induced by nicotine was prevented by nicotinic acetylcholine receptor (nAChR) antagonists, the Ca(2+) chelator 1,2-bis(2-aminophenoxy)-ethane-N,N,N',N'-tetra-acetic acid tetrakis-acetoxymethyl ester, cycloheximide or actinomycin D. Nicotine increased IRS-1 and IRS-2 mRNA levels by approximately 57 and approximately 50%, and this was prevented by conventional protein kinase C (cPKC) inhibitor Gö6976, or ERK kinase inhibitors PD98059 and U0126. Nicotine phosphorylated cPKC-alpha, thereby increasing phosphorylation of ERK1/ERK2, as demonstrated by using Gö6976, PD98059 or U0126. Selective activation of cPKC-alpha by thymeleatoxin mimicked these effects of nicotine. Thus, stimulation of nAChRs up-regulated expression of IRS-1/IRS-2 via Ca(2+)-dependent sequential activation of cPKC-alpha and ERK, and enhanced insulin-induced PI3K/Akt/GSK-3beta and ERK signaling pathways.
Sugano
Takashi
T
Department of Pharmacology, Miyazaki Medical College, University of Miyazaki, Miyazaki, Japan.
Yanagita
Toshihiko
T
Yokoo
Hiroki
H
Satoh
Shinya
S
Kobayashi
Hideyuki
H
Wada
Akihiko
A
D000313:Adrenal Medulla / Q000166:cytology; D000818:Animals; D015152:Blotting, Northern / Q000379:methods; D002417:Cattle; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D007328:Insulin / Q000494:pharmacology*; D055504:Insulin Receptor Substrate Proteins; D007456:Iodine Isotopes / Q000493:pharmacokinetics; D051058:Oncogene Protein v-akt / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D051571:Protein Kinase C-alpha / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011978:Receptors, Nicotinic / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology; D015854:Up-Regulation / Q000187:drug effects* / Q000502:physiology
D004791:Enzyme Inhibitors; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D007456:Iodine Isotopes; D010750:Phosphoproteins; D012333:RNA, Messenger; D011978:Receptors, Nicotinic; D019869:Phosphatidylinositol 3-Kinases; D000071679:Glycogen Synthase Kinase 3 beta; D051058:Oncogene Protein v-akt; D051571:Protein Kinase C-alpha; D048049:Extracellular Signal-Regulated MAP Kinases; D038362:Glycogen Synthase Kinase 3