Phosphorylation of eIF4E is dispensable for skeletal muscle hypertrophy.

Phosphorylation of eIF4E is dispensable for skeletal muscle hypertrophy.
Am J Physiol Cell Physiol. 2019 Oct 09;:
Authors: Figueiredo VC, Englund DA, Vechetti IJ, Alimov A, Peterson CA, McCarthy JJ
Abstract
The eukaryotic initiation factor 4E (eIF4E) is a major mRNA cap-binding protein that has a central role in translation initiation. Serine 209 (Ser209) is the single phosphorylation site within eIF4E and modulates its activity in response to MAPK pathway activation. Previous studies have reported that phosphorylation of eIF4E Ser209 promotes translation of key mRNAs such as cyclin D1 that regulate ribosome biogenesis. We hypothesized that phosphorylation of Ser209 is required for skeletal muscle growth in response to a hypertrophic stimulus by promoting ribosome biogenesis. To test this hypothesis, wild-type (WT) and eIF4E Knocked-In (KI) mice were subjected to synergistic ablation to induce muscle hypertrophy of the plantaris muscle as the result of mechanical overload; the KI mouse has Ser209 of eIF4E replaced with a non-phosphorylatable alanine. Contrary to our hypothesis, we observed no difference in the magnitude of hypertrophy between WT and KI groups in response to 14 days of mechanical overload induced by synergistic ablation. Similarly, the increases in cyclin D1 protein levels, ribosome biogenesis and translational capacity were not different between WT and KI groups. Based on these findings, we conclude that phosphorylat...

Source: Am J Physiol Cell Ph... - October 8, 2019 Category: Cytology Authors: Figueiredo VC, Englund DA, Vechetti IJ, Alimov A, Peterson CA, McCarthy JJ Tags: Am J Physiol Cell Physiol Source Type: research