TY - JOUR
T1 - Ablation of elongation factor 2 kinase enhances heat-shock protein 90 chaperone expression and protects cells under proteotoxic stress
AU - Xie, Jianling
AU - Van Damme, Petra
AU - Fang, Danielle
AU - Proud, Christopher G.
N1 - Publisher Copyright:
© 2019 Xie et al. Published under exclusive license by The American Society for Biochemistry and Molecular Biology, Inc.
PY - 2019/5/3
Y1 - 2019/5/3
N2 - Eukaryotic elongation factor 2 kinase (eEF2K) negatively regulates the elongation stage ofmRNAtranslation 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.
AB - Eukaryotic elongation factor 2 kinase (eEF2K) negatively regulates the elongation stage ofmRNAtranslation 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.
UR - http://www.scopus.com/inward/record.url?scp=85065600733&partnerID=8YFLogxK
U2 - 10.1074/jbc.AC119.008036
DO - 10.1074/jbc.AC119.008036
M3 - Article
C2 - 30890561
AN - SCOPUS:85065600733
SN - 0021-9258
VL - 294
SP - 7169
EP - 7176
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 18
ER -