Glucose-dependent insulinotropic polypeptide-mediated up-regulation of beta-cell antiapoptotic Bcl-2 gene expression is coordinated by cyclic AMP (cAMP) response element binding protein (CREB) and cAMP-responsive CREB coactivator 2.
The cyclic AMP (cAMP)/protein kinase A (PKA) cascade plays a central role in beta-cell proliferation and apoptosis. Here, we show that the incretin hormone glucose-dependent insulinotropic polypeptide (GIP) stimulates expression of the antiapoptotic Bcl-2 gene in pancreatic beta cells through a pathway involving AMP-activated protein kinase (AMPK), cAMP-responsive CREB coactivator 2 (TORC2), and cAMP response element binding protein (CREB). Stimulation of beta-INS-1 (clone 832/13) cells with GIP resulted in increased Bcl-2 promoter activity. Analysis of the rat Bcl-2 promoter revealed two potential cAMP response elements, one of which (CRE-I [GTGACGTAC]) was shown, using mutagenesis and deletion analysis, to be functional. Subsequent studies established that GIP increased the nuclear localization of TORC2 and phosphorylation of CREB serine 133 through a pathway involving PKA activation and reduced AMPK phosphorylation. At the nuclear level, phospho-CREB and TORC2 were demonstrated to bind to CRE-I of the Bcl-2 promoter, and GIP treatment resulted in increases in their interaction. Furthermore, GIP-mediated cytoprotection was partially reversed by small interfering RNA-mediated reduction in BCL-2 or TORC2/CREB or by pharmacological activation of AMPK. The antiapoptotic effect of GIP in beta cells is therefore partially mediated through a novel mode of transcriptional regulation of Bcl-2 involving cAMP/PKA/AMPK-dependent regulation of CREB/TORC2 activity.
Kim
Su-Jin
SJ
Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, 2350 Health Sciences Mall, Vancouver, B.C. V6T 1Z3, Canada. mcintoch@interchange.ubc.ca.
Nian
Cuilan
C
Widenmaier
Scott
S
McIntosh
Christopher H S
CH
D000818:Animals; D053148:Caspase 3 / Q000032:analysis / Q000378:metabolism; D018929:Cell Culture Techniques; D002467:Cell Nucleus / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002999:Clone Cells / Q000378:metabolism; D003470:Culture Media; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005749:Gastric Inhibitory Polypeptide / Q000378:metabolism / Q000494:pharmacology*; D015870:Gene Expression; D017930:Genes, Reporter; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D008156:Luciferases / Q000032:analysis / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011401:Promoter Regions, Genetic; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D051381:Rats; D013223:Statistics as Topic; D015534:Trans-Activators; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D015854:Up-Regulation / Q000187:drug effects*; D001616:beta-Galactosidase / Q000378:metabolism
C545700:CRTC2 protein, rat; D003470:Culture Media; D017362:Cyclic AMP Response Element-Binding Protein; D019253:Proto-Oncogene Proteins c-bcl-2; D015534:Trans-Activators; D014157:Transcription Factors; D005749:Gastric Inhibitory Polypeptide; D008156:Luciferases; D001616:beta-Galactosidase; D053148:Caspase 3