Glucose and forskolin regulate IAPP gene expression through different signal transduction pathways.
Molecular mechanisms for the regulation of islet amyloid polypeptide (IAPP) gene expression remain unclear. In the present study, we investigated the effects of glucose and forskolin on IAPP gene regulation in the INS-1 islet beta-cell line. Both glucose and forskolin increased the level of expression of this gene, as measured by Northern blot analysis, and increased IAPP gene transcription in a time- and concentration-dependent manner, as demonstrated in a reporter gene assay. Although inhibition of protein kinase A activity with H-89 eliminated the effect of forskolin on this gene, the glucose effect was unaffected. This supported the predominant use of a protein kinase A-independent signaling pathway for glucose regulation of the IAPP gene. Electrophoretic mobility shift assay further indicated that glucose and forskolin regulated expression of this gene by targeting different elements of the promoter. Mutation of the cAMP regulatory element flanking the IAPP coding region resulted in the loss of most of the forskolin-stimulated IAPP gene promoter activity, whereas glucose-enhanced IAPP gene transcription was unaffected. These results demonstrate parallel and distinct regulatory pathways involved in glucose- and forskolin-induced IAPP gene expression in this model beta-cell system.
Ding
W Q
WQ
Department of Medicine, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA.
Holicky
E
E
Miller
L J
LJ
D000067956:Adenylyl Cyclase Inhibitors; D000682:Amyloid / Q000235:genetics*; D015152:Blotting, Northern; D021441:Carcinoma, Pancreatic Ductal; D005576:Colforsin / Q000494:pharmacology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects*; D005947:Glucose / Q000494:pharmacology*; D006801:Humans; D058228:Islet Amyloid Polypeptide; D007546:Isoquinolines / Q000494:pharmacology; D010190:Pancreatic Neoplasms; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013449:Sulfonamides; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D000067956:Adenylyl Cyclase Inhibitors; D000682:Amyloid; D004791:Enzyme Inhibitors; D058228:Islet Amyloid Polypeptide; D007546:Isoquinolines; D012333:RNA, Messenger; D013449:Sulfonamides; D005576:Colforsin; D017868:Cyclic AMP-Dependent Protein Kinases; D005947:Glucose; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; D013755:Tetradecanoylphorbol Acetate