Transcriptional regulation of the endoplasmic reticulum stress gene chop in pancreatic insulin-producing cells.
Endoplasmic reticulum stress-mediated apoptosis may play an important role in the destruction of pancreatic beta-cells, thus contributing to the development of type 1 and type 2 diabetes. One of the regulators of endoplasmic reticulum stress-mediated cell death is the CCAAT/enhancer binding protein (C/EBP) homologous protein (Chop). We presently studied the molecular regulation of Chop expression in insulin-producing cells (INS-1E) in response to three pro-apoptotic and endoplasmic reticulum stress-inducing agents, namely the cytokines interleukin-1beta + interferon-gamma, the free fatty acid palmitate, and the sarcoendoplasmic reticulum pump Ca(2+) ATPase blocker cyclopiazonic acid (CPA). Detailed mutagenesis studies of the Chop promoter showed differential regulation of Chop transcription by CPA, cytokines, and palmitate. Whereas palmitate- and cytokine-induced Chop expression was mediated via a C/EBP-activating transcription factor (ATF) composite and AP-1 binding sites, CPA induction required the C/EBP-ATF site and the endoplasmic reticulum stress response element. Cytokines, palmitate, and CPA induced eIF2alpha phosphorylation in INS-1E cells leading to activation of the transcription factor ATF4. Chop transcription in response to cytokines and palmitate depends on the binding of ATF4 and AP-1 to the Chop promoter, but distinct AP-1 dimers were formed by cytokines and palmitate. These results suggest a differential response of beta-cells to diverse endoplasmic reticulum stress inducers, leading to a differential regulation of Chop transcription.
Pirot
Pierre
P
Laboratory of Experimental Medicine, Université Libre de Bruxelles, Route de Lennik, 808-CP-618, 1070 Brussels, Belgium.
Ortis
Fernanda
F
Cnop
Miriam
M
Ma
Yanjun
Y
Hendershot
Linda M
LM
Eizirik
Décio L
DL
Cardozo
Alessandra K
AK
D000818:Animals; D002460:Cell Line; D017931:DNA Primers; D004721:Endoplasmic Reticulum / Q000502:physiology*; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D007328:Insulin / Q000502:physiology*; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D007340:Insulinoma; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D015183:Restriction Mapping; D051742:Transcription Factor CHOP / Q000235:genetics*; D014158:Transcription, Genetic; D014162:Transfection
D017931:DNA Primers; D007328:Insulin; D012333:RNA, Messenger; D051742:Transcription Factor CHOP