One of the key cellular responses to stress is the attenuation of mRNA translation and protein synthesis via the phosphorylation of eIF2α (eukaryotic translation initiation factor 2α). This is mediated by four eIF2α kinases and it has been suggested that each kinase is specific to the cellular stress imposed. In the present study, we show that both PERK (PKR-like endoplasmic reticulum kinase/eIF2α kinase 3) and GCN2 (general control non-derepressible 2/eIF2α kinase 4) are required for the stress responses associated with conditions encountered by cells overexpressing secreted recombinant protein. Importantly, whereas GCN2 is the kinase that is activated following cold-shock/hypothermic culturing of mammalian cells, PERK and GCN2 have overlapping functions since knockdown of one of these at the mRNA level is compensated for by the cell by up-regulating levels of the other. The protein p58IPK {also known as DnaJ3C [DnaJ heat-shock protein (hsp) 40 homologue, subfamily C, member 3]} is known to inhibit the eIF2α kinases PKR (dsRNA-dependent protein kinase/eIF2α kinase 2) and PERK and hence prevent or delay eIF2α phosphorylation and consequent inhibition of translation. However, we show that p58IPK is a general inhibitor of the eIF2α kinases in that it also interacts with GCN2. Thus forced overexpression of cytoplasmic p58 delays eIF2α phosphorylation, suppresses GCN2 phosphorylation and prolongs protein synthesis under endoplasmic reticulum (ER), hypothermic and prolonged culture stress conditions. Taken together, our data suggest that there is considerable cross talk between the eIF2α kinases to ensure that protein synthesis is tightly regulated. Their activation is controlled by p58 and the expression levels and localization of this protein are crucial in the capacity the cells to respond to cellular stress via control of protein synthesis rates and subsequent folding in the ER.
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Research Article|
January 06 2015
p58IPK is an inhibitor of the eIF2α kinase GCN2 and its localization and expression underpin protein synthesis and ER processing capacity
Anne Roobol;
Anne Roobol
*Centre for Molecular Processing and Protein Science Group, School of Biosciences, University of Kent, Canterbury, Kent, CT2 7NJ, U.K.
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Jo Roobol;
Jo Roobol
*Centre for Molecular Processing and Protein Science Group, School of Biosciences, University of Kent, Canterbury, Kent, CT2 7NJ, U.K.
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Amandine Bastide;
Amandine Bastide
†MRC Toxicology Unit, Hodgkin Building, PO Box 138, Lancaster Road, Leicester LE1 9HN, U.K.
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John R. P. Knight;
John R. P. Knight
†MRC Toxicology Unit, Hodgkin Building, PO Box 138, Lancaster Road, Leicester LE1 9HN, U.K.
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Anne E. Willis;
Anne E. Willis
1
†MRC Toxicology Unit, Hodgkin Building, PO Box 138, Lancaster Road, Leicester LE1 9HN, U.K.
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C. Mark Smales
C. Mark Smales
1
*Centre for Molecular Processing and Protein Science Group, School of Biosciences, University of Kent, Canterbury, Kent, CT2 7NJ, U.K.
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Publisher: Portland Press Ltd
Received:
July 07 2014
Revision Received:
October 02 2014
Accepted:
October 20 2014
Accepted Manuscript online:
October 20 2014
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© The Authors Journal compilation © 2015 Biochemical Society
2015
Biochem J (2015) 465 (2): 213–225.
Article history
Received:
July 07 2014
Revision Received:
October 02 2014
Accepted:
October 20 2014
Accepted Manuscript online:
October 20 2014
Citation
Anne Roobol, Jo Roobol, Amandine Bastide, John R. P. Knight, Anne E. Willis, C. Mark Smales; p58IPK is an inhibitor of the eIF2α kinase GCN2 and its localization and expression underpin protein synthesis and ER processing capacity. Biochem J 15 January 2015; 465 (2): 213–225. doi: https://doi.org/10.1042/BJ20140852
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