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J Biol Chem. 2019 May 3;294(18):7169-7176. doi: 10.1074/jbc.AC119.008036. Epub 2019 Mar 19.

Ablation of elongation factor 2 kinase enhances heat-shock protein 90 chaperone expression and protects cells under proteotoxic stress.

Author information

1
From the Lifelong Health Theme, South Australian Health and Medical Research Institute, North Terrace, Adelaide SA5000, Australia.
2
Department of Biochemistry and Microbiology, Ghent University, B-9000 Ghent, Belgium.
3
VIB Center for Medical Biotechnology, Ghent, Belgium, and.
4
School of Biological Sciences, University of Adelaide, Adelaide SA5005, Australia.
5
From the Lifelong Health Theme, South Australian Health and Medical Research Institute, North Terrace, Adelaide SA5000, Australia, christopher.proud@sahmri.com.

Abstract

Eukaryotic elongation factor 2 kinase (eEF2K) negatively regulates the elongation stage of mRNA translation and is activated under different stress conditions to slow down protein synthesis. One effect of eEF2K is to alter the repertoire of expressed proteins, perhaps to aid survival of stressed cells. Here, we applied pulsed stable isotope labeling with amino acids in cell culture (SILAC) to study changes in the synthesis of specific proteins in human lung adenocarcinoma (A549) cells in which eEF2K had been depleted by an inducible shRNA. We discovered that levels of heat-shock protein 90 (HSP90) are increased in eEF2K-depleted human cells as well as in eEF2K-knockout (eEF2K-/-) mouse embryonic fibroblasts (MEFs). This rise in HSP90 coincided with an increase in the fraction of HSP90 mRNAs associated with translationally active polysomes, irrespective of unchanged total HSP90 levels. These results indicate that blocking eEF2K function can enhance expression of HSP90 chaperones. In eEF2K-/- mouse embryonic fibroblasts (MEFs), inhibition of HSP90 by its specific inhibitor AUY922 promoted the accumulation of ubiquitinated proteins. Notably, HSP90 inhibition promoted apoptosis of eEF2K-/- MEFs under proteostatic stress induced by the proteasome inhibitor MG132. Up-regulation of HSP90 likely protects cells from protein folding stress, arising, for example, from faster rates of polypeptide synthesis due to the lack of eEF2K. Our findings indicate that eEF2K and HSPs closely cooperate to maintain proper proteostasis and suggest that concomitant inhibition of HSP90 and eEF2K could be a strategy to decrease cancer cell survival.

KEYWORDS:

apoptosis; cancer; elongation; eukaryotic elongation factor 2 kinase (eEF2K); heat shock protein (HSP); mRNA translation; molecular chaperone; proteasome; protein synthesis; translation elongation factor

PMID:
30890561
PMCID:
PMC6509509
[Available on 2020-05-03]
DOI:
10.1074/jbc.AC119.008036

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