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.
- SourceAvailable from: William Brackenbury[Show abstract] [Hide abstract]
ABSTRACT: Although ion channels are increasingly being discovered in cancer cells in vitro and in vivo, and shown to contribute to different aspects and stages of the cancer process, much less is known about the mechanisms controlling their expression. Here, we focus on voltage-gated Na(+) channels (VGSCs) which are upregulated in many types of carcinomas where their activity potentiates cell behaviours integral to the metastatic cascade. Regulation of VGSCs occurs at a hierarchy of levels from transcription to post-translation. Importantly, mainstream cancer mechanisms, especially hormones and growth factors, play a significant role in the regulation. On the whole, in major hormone-sensitive cancers, such as breast and prostate cancer, there is a negative association between genomic steroid hormone sensitivity and functional VGSC expression. Activity-dependent regulation by positive feedback has been demonstrated in strongly metastatic cells whereby the VGSC is self-sustaining, with its activity promoting further functional channel expression. Such auto-regulation is unlike normal cells in which activity-dependent regulation occurs mostly via negative feedback. Throughout, we highlight the possible clinical implications of functional VGSC expression and regulation in cancer.Philosophical Transactions of The Royal Society B Biological Sciences 01/2014; 369(1638):20130105. · 6.23 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Haemopressin and RVD-haemopressin, derived from the haemoglobin α chain, are bioactive peptides isolated from the brain. These peptides are ligands for cannabinoid CB1 receptors. Previously, we reported that brain CB1 receptors play an inhibitory role in the secretion of intracerebroventricularly (i.c.v.) administered bombesin-induced adrenal catecholamines (noradrenaline and adrenaline) in the rat. Here, we investigated the effects of two haemoglobin-derived peptides on the bombesin-induced response regarding brain CB1 receptors in the rat. Under anaesthesia, male Wistar rats were i.c.v. pretreated with each haemoglobin-derived peptide 30 min before intracerebroventricular administration of bombesin, and plasma catecholamines were sequentially assayed. The direct effect of bombesin on the secretion of adrenal catecholamines was also examined using bovine adrenal chromaffin cells. Furthermore, we performed immunohistochemical analysis for a neuronal activation marker Fos on haemoglobin α-positive spinally projecting neurons in the rat hypothalamic paraventricular nucleus (PVN, a regulation centre of central adrenomedullary outflow) after the administration of bombesin. I.c.v. administered bombesin dose-dependently elevated plasma catecholamines while bombesin had no effect on spontaneous and nicotine-induced secretion of catecholamines from chromaffin cells. The elevation of bombesin-induced catecholamines was inhibited by i.c.v. pretreated RVD-haemopressin (CB1 receptor agonist) but not by haemopressin (CB1 receptor inverse agonist). Bombesin activated haemoglobin α-positive spinally projecting neurons in the PVN. Haemoglobin-derived peptide RVD-haemopressin in the brain plays an inhibitory role in bombesin-induced activation of central adrenomedullary outflow via brain CB1 receptors in the rat. These findings provide basic information for the therapeutic use of haemoglobin-derived peptides in the modulation of central adrenomedullary outflow.British Journal of Pharmacology 10/2013; · 5.07 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Orexin (hypocretin) is a neuropeptide secreted from hypothalamic neurons that is known to be activated during motivated behaviors and active waking. Presently, our knowledge of orexin is mainly limited to the central nervous system, and the involvement of the orexin system in peripheral tissues has received little attention. In the present study, we analyzed the existence of the orexin system in the adrenal medulla, which is part of the sympathetic nervous system. Orexin and its receptors are expressed in the bovine adrenal medulla. Orexins stimulated intracellular calcium changes and epinephrine release from cultured bovine adrenal medullary cells. Applied orexin decreased expression of prepro-orexin, orexin receptor-1 and orexin receptor-2, suggesting negative feedback regulation in the adrenal gland. Our results indicate involvement of the orexin system in the sympathetic regulation of the adrenal medulla.Pharmacology 04/2013; 91(5-6):250-258. · 1.60 Impact Factor