The principal mechanism underlying the reduced rate of protein synthesis in atrophied
skeletal muscle is largely unknown. Eukaryotic elongation factor 2 kinase (eEF2k)
impairs the ability of eukaryotic translation elongation factor 2 (eEF2) to bind to
the ribosome via T56 phosphorylation. Perturbations in the eEF2k/eEF2 pathway during
various stages of disuse muscle atrophy have been investigated utilizing a rat hind
limb suspension (HS) model. Two distinct components of eEF2k/eEF2 pathway misregulation
were demonstrated, observing a significant (P < 0.01) increase in eEF2k mRNA expression as early as 1-day HS and in eEF2k protein
level after 3-day HS. We set out to determine whether eEF2k activation is a Ca2+-dependent process with involvement of Cav1.1. The ratio of T56-phosphorylated/total
eEF2 was robustly elevated after 3-day HS, which was completely reversed by BAPTA-AM
and decreased by 1.7-fold (P < 0.05) by nifedipine. Transfection of C2C12 with pCMV-eEF2k and administration with
small molecules were used to modulate eEF2k and eEF2 activity. More important, pharmacologic
enhancement of eEF2 phosphorylation induced phosphorylated ribosomal protein S6 kinase
(T389) up-regulation and restoration of global protein synthesis in the HS rats. Taken
together, the eEF2k/eEF2 pathway is up-regulated during disuse muscle atrophy involving
calcium-dependent activation of eEF2k partly via Cav1.1. The study provides evidence,
in vitro and in vivo, of the eEF2k/eEF2 pathway impact on ribosomal protein S6 kinase activity as well
as protein expression of key atrophy biomarkers, muscle atrophy F-box/atrogin-1 and
muscle RING finger-1.
Graphical abstract
Graphical Abstract
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Article info
Publication history
Published online: March 02, 2023
Accepted:
February 10,
2023
Publication stage
In Press Journal Pre-ProofFootnotes
Disclosures: None declared.
Supported by Medical Research Council project grant AVR01600 (M.J.A.W.) and the Foundation for Basic Research grant RFBR11-04-01769-a (Y.L.).
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© 2023 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.
