Calcium-mobilizing insulin secretagogues stimulate transcription that is directed by the cyclic adenosine 3',5'-monophosphate/calcium response element in a pancreatic islet beta-cell line.
In pancreatic beta-cells, calcium is required for insulin secretion, but can also stimulate gene transcription. High potassium-induced membrane depolarization and calcium influx have previously been shown to activate kinases that phosphorylate and thereby activate the transcription factor cAMP response element (CRE-binding protein (CREB) binding to CREs. It is unknown, however, whether hormones and neurotransmitters can activate this mechanism. Arginine vasopressin (AVP), bombesin, and acetylcholine potentiate glucose-induced insulin secretion and are known to raise cytosolic calcium levels through binding to cell surface receptors that activate phospholipase C. The effect of AVP on CRE-directed transcription was examined in the beta-cell line HIT. AVP (0.1-100 nM) stimulated gene transcription after transient transfection of a reporter gene that was placed under the transcriptional control of a CRE. This effect was inhibited by a vasopressin V1 receptor antagonist and depended on calcium influx and calcineurin phosphatase activity. By immunoblots with antiphospho-CREB antibodies and by using a Gal4-CREB fusion protein, it was shown that AVP induces the phosphorylation and activation of CREB. Like AVP, bombesin (100 nM) and the muscarinic agonist carbachol (200 microM) stimulated CRE-mediated transcription. These results show that calcium-mediating insulin secretagogues can activate CREB/CRE-directed transcription in HIT cells, offering a mechanism by which these secretagogues could produce long term effects on beta-cell function, changing the pattern of gene expression.
Department of Biochemical Pharmacology, University of Gottingen, Germany.
B
B
Eckert
M
M
Schwaninger
W
W
Knepel
D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism* / Q000502:physiology; D002460:Cell Line; D006224:Cricetinae; D017362:Cyclic AMP Response Element-Binding Protein / Q000502:physiology*; D016572:Cyclosporine / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000166:cytology / Q000502:physiology*; D010766:Phosphorylation / Q000187:drug effects; D016559:Tacrolimus / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects
D017362:Cyclic AMP Response Element-Binding Protein; D007328:Insulin; D001127:Arginine Vasopressin; D016572:Cyclosporine; D002118:Calcium; D016559:Tacrolimus