Transcriptional response of pancreatic beta cells to metabolic stimulation: large scale identification of immediate-early and secondary response genes.
BACKGROUND
Physiological long term adaptation of pancreatic beta cells is driven by stimuli such as glucose and incretin hormones acting via cAMP (e.g. GLP-1) and involves regulated gene expression. Several rapidly inducible immediate-early genes (IEGs) have been identified in beta cells. Many of these IEGs code for transcription factors and have the potential to control the transcription of downstream target genes likely involved in long term cellular adaptation. The identity of these target genes has not been determined, and the sequence of events occurring during beta cell adaptation is still unclear.


RESULTS
We have developed a microarray-based strategy for the systematic search of targets. In Min6 insulin-secreting cells, we identified 592 targets and 1278 IEGs responding to a co-stimulation with glucose and cAMP. Both IEGs and targets were involved in a large panel of functions, including those important to beta cell physiology (metabolism, secretion). Nearly 200 IEGs were involved in signaling and transcriptional regulation. To find specific examples of the regulatory link between IEGs and targets, target promoter sequences were analyzed in silico. Statistically significant over-representation of AP-1 response elements notably suggested an important role for this transcription factor, which was experimentally verified. Indeed, cell stimulation altered expression of IEG-encoded components of the AP-1 complex, activating AP-1-dependent transcription. Loss and gain-of-function experiments furthermore allowed to validate a new AP-1 regulated gene (sulfiredoxin) among the targets. AP-1 and sulfiredoxin are sequentially induced also in primary cells from rat islets of Langerhans.


CONCLUSIONS
By identifying IEGs and their downstream targets, this study brings a comprehensive description of the transcriptional response occurring after beta cell stimulation, as well as new mechanistic insights concerning the AP-1 transcription factor.
Glauser
Dominique A
DA
Fondation pour Recherches Médicales, University of Geneva, Geneva, Switzerland. dominique.glauser@medecine.unige.ch <dominique.glauser@medecine.unige.ch>
Brun
Thierry
T
Gauthier
Benoit R
BR
Schlegel
Werner
W
D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D020869:Gene Expression Profiling; D017930:Genes, Reporter / Q000235:genetics; D052216:Glucagon-Like Peptide 1 / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D007150:Immunohistochemistry; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D008156:Luciferases; D008297:Male; D051379:Mice; D020411:Oligonucleotide Array Sequence Analysis; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction
D017931:DNA Primers; D052216:Glucagon-Like Peptide 1; D000242:Cyclic AMP; D008156:Luciferases; D005947:Glucose