Global profiling of genes modified by endoplasmic reticulum stress in pancreatic beta cells reveals the early degradation of insulin mRNAs.
OBJECTIVE
Pancreatic beta cells respond to endoplasmic reticulum (ER) stress by activating the unfolded protein response. If the stress is prolonged, or the adaptive response fails, apoptosis is triggered. We used a 'homemade' microarray specifically designed for the study of beta cell apoptosis (the APOCHIP) to uncover mechanisms regulating beta cell responses to ER stress.


METHODS
A time course viability and microarray analysis was performed in insulin-producing INS-1E cells exposed to the reversible ER stress inducer cyclopiazonic acid (CPA). Modification of selected genes was confirmed by real-time RT-PCR, and the observed inhibition of expression of the insulin-1 (Ins1) and insulin-2 (Ins2) genes was further characterised in primary beta cells exposed to a diverse range of agents that induce ER stress.


RESULTS
CPA-induced ER stress modified the expression of 183 genes at one or more of the time points studied. The expression of most of these genes returned to control levels after a 3 h recovery period following CPA removal, with all cells surviving. Two groups of genes were particularly affected by CPA, namely, those related to cellular responses to ER stress, which were mostly upregulated, and those related to differentiated beta cell functions, which were downregulated. Levels of Ins1 and Ins2 mRNAs were severely decreased in response to CPA treatment as a result of degradation, and there was a concomitant increase in the level of IRE1 activation.


CONCLUSIONS
In this study we provide the first global analysis of beta cell molecular responses to a severe ER stress, and identify the early degradation of mRNA transcripts of the insulin genes as an important component of this response.
Pirot
P
P
Laboratory of Experimental Medicine, Université Libre de Bruxelles (ULB), Route de Lennik, 808-CP-618, 1070 Brussels, Belgium.
Naamane
N
N
Libert
F
F
Magnusson
N E
NE
Ørntoft
T F
TF
Cardozo
A K
AK
Eizirik
D L
DL
D002460:Cell Line; D002470:Cell Survival; D002478:Cells, Cultured; D004721:Endoplasmic Reticulum / Q000502:physiology*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007328:Insulin / Q000235:genetics*; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D020411:Oligonucleotide Array Sequence Analysis; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism*; D013314:Stress, Mechanical
D007211:Indoles; D007328:Insulin; D012333:RNA, Messenger; C000543:cyclopiazonic acid