title: Phosphorylation of cyclic AMP-response element-binding protein (CREB) is influenced by melatonin treatment in pancreatic rat insulinoma β-cells (INS-1).
abstract: The pineal hormone melatonin exerts its influence on the insulin secretion of pancreatic islets by a variety of signalling pathways. The purpose of the present study was to analyse the impact of melatonin on the phosphorylated transcription factor cAMP-response element-binding protein (pCREB). In pancreatic rat insulinoma β-cells (INS-1), pCREB immunofluorescence intensities in cell nuclei using digitised confocal image analysis were measured to semi-quantify differences in the pCREB immunoreactivity (pCREB-ir) caused by different treatments. Increasing concentrations of forskolin or 3-isobutyl-1-methylxanthine (IBMX) resulted in a dose-dependent rise of the mean fluorescence intensity in pCREB-ir nuclear staining. Concomitant melatonin application significantly decreased pCREB-ir in INS-1 cells after 30-min, 1-hr and 3-hr treatment. The melatonin receptor antagonists luzindole and 4-phenyl-2-propionamidotetraline (4P-PDOT) completely abolished the pCREB phosphorylation-decreasing effect of melatonin, indicating that both melatonin receptor isoforms (MT(1) and MT(2)) are involved. In a transfected INS-1 cell line expressing the human MT(2) receptor, melatonin caused the greatest reduction in pCREB after IBMX treatment compared with nontransfected INS-1 cells, indicating a crucial influence of melatonin receptor density on pCREB regulation. Furthermore, the downregulation of pCREB by melatonin is concomitantly associated with a statistically significant downregulation of Camk2d transcript levels, as measured after 3 hr. In conclusion, the present study provides evidence that the phosphorylation level of CREB is modulated in pancreatic β-cells by melatonin. Mediated via CREB, melatonin regulates the expression of genes that play an important functional role in the regulation of β-cell signalling pathways.
authors.affiliation: Institute of Anatomy and Cell Biology, Martin Luther University Halle-Wittenberg, Halle, Germany. ivonne.bazwinsky@medizin.uni-halle.de
authors.forename: Ivonne
authors.initials: I
authors.lastname: Bazwinsky-Wutschke
authors.forename: Sabine
authors.initials: S
authors.lastname: Wolgast
authors.forename: Eckhard
authors.initials: E
authors.lastname: Mühlbauer
authors.forename: Elke
authors.initials: E
authors.lastname: Albrecht
authors.forename: Elmar
authors.initials: E
authors.lastname: Peschke
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D005576:Colforsin / Q000494:pharmacology; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005455:Fluorescent Antibody Technique; D006801:Humans; D050417:Insulin-Secreting Cells / Q000187:drug effects* / Q000378:metabolism; D007340:Insulinoma / Q000235:genetics / Q000378:metabolism*; D008550:Melatonin / Q000494:pharmacology*; D018613:Microscopy, Confocal; D010190:Pancreatic Neoplasms / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D051381:Rats; D044122:Receptor, Melatonin, MT1 / Q000187:drug effects / Q000378:metabolism; D044123:Receptor, Melatonin, MT2 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013764:Tetrahydronaphthalenes / Q000494:pharmacology; D013997:Time Factors; D014162:Transfection; D014363:Tryptamines / Q000494:pharmacology
chemical_list: C114459:4-phenyl-2-propionamidotetraline; C508137:Creb1 protein, rat; D017362:Cyclic AMP Response Element-Binding Protein; D044122:Receptor, Melatonin, MT1; D044123:Receptor, Melatonin, MT2; D013764:Tetrahydronaphthalenes; D014363:Tryptamines; C057154:luzindole; D005576:Colforsin; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; C517677:Camk2d protein, rat; D008550:Melatonin; D015056:1-Methyl-3-isobutylxanthine