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Thapsigargin down‐regulates protein levels of GRP78/BiP in INS‐1E cells
Author(s) -
Rosengren Victoria,
Johansson Henrik,
Lehtiö Janne,
Fransson Liselotte,
Sjöholm Åke,
Ortsäter Henrik
Publication year - 2012
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.24032
Subject(s) - thapsigargin , unfolded protein response , endoplasmic reticulum , protein disulfide isomerase , chaperone (clinical) , microbiology and biotechnology , western blot , chemistry , chop , glucose regulated protein , cell culture , intracellular , biology , biochemistry , medicine , genetics , pathology , gene
Pancreatic β‐cells have a well‐developed endoplasmic reticulum (ER) and express large amounts of chaperones and protein disulfide isomerases (PDI) to meet the high demand for synthesis of proteins. We have observed an unexpected decrease in chaperone protein level in the β‐cell model INS‐1E after exposure to the ER stress inducing agent thapsigargin. As these cells are a commonly used model for primary β‐cells and has been shown to be vulnerable to ER stress, we hypothesize these cells are incapable of mounting a chaperone defense upon activation of ER stress. To investigate the chaperone expression during an ER stress response, induced by thapsigargin in INS‐1E cells, we used quantitative mass spectrometry based proteomics. The results displayed a decrease of GRP78/BiP, PDIA3 and PDIA6. Decrease of GRP78/BiP was verified by Western blot and occurred in parallel with enhanced levels of p‐eIF2α and CHOP. In contrast to INS‐1E cells, GRP78/BiP was not decreased in MIN6 cell or rat and mouse islets after thapsigargin exposure. Investigation of the decreased protein levels of GRP78/BiP indicates that this is not a consequence of reduced mRNA expression. Rather the reduction results from the combined effect of reduced protein synthesis and enhanced proteosomal degradation and possibly also degradation via autophagy. Induction of ER stress with thapsigargin leads to lower protein levels of GRP78/BiP, PDIA3 and PDIA6 in INS‐1E cells which may contribute to the susceptibility of ER stress in this β‐cell model. J. Cell. Biochem. 113: 1635–1644, 2012. © 2011 Wiley Periodicals, Inc.