title: Transcriptional up-regulation of cell surface Na V 1.7 sodium channels by insulin-like growth factor-1 via inhibition of glycogen synthase kinase-3β in adrenal chromaffin cells: enhancement of 22Na+ influx, 45Ca2+ influx and catecholamine secretion.
abstract: Insulin-like growth factor-1 (IGF-1) plays important roles in the regulation of neuronal development. The electrical activity of Na(+) channels is crucial for the regulation of synaptic formation and maintenance/repair of neuronal circuits. Here, we examined the effects of chronic IGF-1 treatment on cell surface expression and function of Na(+) channels. In cultured bovine adrenal chromaffin cells expressing Na(V)1.7 isoform of voltage-dependent Na(+) channels, chronic IGF-1 treatment increased cell surface [(3)H]saxitoxin binding by 31%, without altering the Kd value. In cells treated with IGF-1, veratridine-induced (22)Na(+) influx, and subsequent (45)Ca(2+) influx and catecholamine secretion were augmented by 35%, 33%, 31%, respectively. Pharmacological properties of Na(+) channels characterized by neurotoxins were similar between nontreated and IGF-1-treated cells. IGF-1-induced up-regulation of [(3)H]saxitoxin binding was prevented by phosphatydil inositol-3 kinase inhibitors (LY204002 or wortmannin), or Akt inhibitor (Akt inhibitor IV). Glycogen synthase kinase-3 (GSK-3) inhibitors (LiCl, valproic acid, SB216763 or SB415286) also increased cell surface [(3)H]saxitoxin binding by ∼ 33%, whereas simultaneous treatment of IGF-1 with GSK-3 inhibitors did not produce additive increasing effect on [(3)H]saxitoxin binding. IGF-1 (100 nM) increased Ser(437)-phosphorylated Akt and Ser(9)-phosphorylated GSK-3β, and inhibited GSK-3β activity. Treatment with IGF-1, LiCl or SB216763 increased protein level of Na(+) channel α-subunit; it was prevented by cycloheximide. Either treatment increased α-subunit mRNA level by ∼ 48% and accelerated α-subunit gene transcription by ∼ 30% without altering α-subunit mRNA stability. Thus, inhibition of GSK-3β caused by IGF-1 up-regulates cell surface expression of functional Na(+) channels via acceleration of α-subunit gene transcription.
authors.affiliation: Department of Pharmacology, Miyazaki Medical College, University of Miyazaki, 5200 Kihara Kiyotake, Miyazaki 889-1692, Japan. yanagita@med.miyazaki-u.ac.jp
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Yanagita
authors.forename: Shinya
authors.initials: S
authors.lastname: Satoh
authors.forename: Yasuhito
authors.initials: Y
authors.lastname: Uezono
authors.forename: Kiyotaka
authors.initials: K
authors.lastname: Matsuo
authors.forename: Takayuki
authors.initials: T
authors.lastname: Nemoto
authors.forename: Toyoaki
authors.initials: T
authors.lastname: Maruta
authors.forename: Norie
authors.initials: N
authors.lastname: Yoshikawa
authors.forename: Tomomi
authors.initials: T
authors.lastname: Iwakiri
authors.forename: Kouichiro
authors.initials: K
authors.lastname: Minami
authors.forename: Manabu
authors.initials: M
authors.lastname: Murakami
mesh_terms: D000311:Adrenal Glands / Q000166:cytology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002395:Catecholamines / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000187:drug effects* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D047468:Immunoprecipitation; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D012333:RNA, Messenger / Q000378:metabolism; D011868:Radioisotopes / Q000493:pharmacokinetics; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D011972:Receptor, Insulin / Q000378:metabolism; D012530:Saxitoxin / Q000493:pharmacokinetics; D012964:Sodium / Q000378:metabolism; D015222:Sodium Channels / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D015854:Up-Regulation / Q000187:drug effects*
chemical_list: D002395:Catecholamines; D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D011868:Radioisotopes; D015222:Sodium Channels; D012530:Saxitoxin; D007334:Insulin-Like Growth Factor I; D012964:Sodium; D017526:Receptor, IGF Type 1; D011972:Receptor, Insulin; D000071679:Glycogen Synthase Kinase 3 beta; D038362:Glycogen Synthase Kinase 3; D002118:Calcium