Dexamethasone‐Induced Skeletal Muscle Atrophy Increases O‐GlcNAcylation in C2C12 Cells

Abstract

Skeletal muscle atrophy is a well-known adverse effect of chronic treatment with glucocorticoids and it also occurs when stress conditions such as sepsis and cachexia increase the release of endogenous glucocorticoids. Although the mechanisms of action of these hormones have been elucidated, the possible molecular mechanisms causing atrophy are not yet fully understood. The involvement of the O-GlcNAcylation process has recently been reported in disuse atrophy. O-GlcNAcylation, a regulatory post-translational modification of nuclear and cytoplasmic proteins consists in the attachment of O-GlcNAc residues on cell proteins and is regulated by two enzymes: O-GlcNAc-transferase (OGT) and O-GlcNAcase (OGA). O-GlcNAcylation plays a crucial role in many cellular processes and it seems to be related to skeletal muscle physiological function. The aim of this study is to investigate the involvement of O-GlcNAcylation in glucocorticoid-induced atrophy by using an "in vitro" model, achieved by treatment of C2C12 with 10 μM dexamethasone for 48 h. In atrophic condition, we observed that O-GlcNAc levels in cell proteins increased and concomitantly protein phosphorylation on serine and threonine residues decreased. Analysis of OGA expression at mRNA and protein levels showed a reduction in this enzyme in atrophic myotubes, whereas no significant changes of OGT expression were found. Furthermore, inhibition of OGA activity by Thiamet G induced atrophy marker expression. Our current findings suggest that O-GlcNAcylation is involved in dexamethasone-induced atrophy. In particular, we propose that the decrease in OGA content causes an excessive and mostly durable level of O-GlcNAc residues on sarcomeric proteins that might modify their function and stability. J. Cell. Biochem. 117: 1833-1842, 2016. © 2016 Wiley Periodicals, Inc.

Group I Paks support muscle regeneration and counteract cancer‐associated muscle atrophy

“…Skeletal muscle atrophy is an established adverse effect caused by treatment with glucocorticoids. 62 Consistently, we also observed reduced mRNA levels of Pak1 in atrophying myotubes following dexamethasone exposure in vitro (Figure 2E). Dexamethasone treatment causes myotube atrophy, as seen by reduced protein synthesis ( Figure S6A), while at the same time induces a down-regulation of Pak1 expression and MuRF1 induction (Figure 2E and 2F).…”

“…Moreover, CSA analysis of TA from C26‐bearing mice previously electroporated with DsRed2‐PAK1 or DsRed2 expressing plasmids suggested that overexpressed Pak1 preserves fiber area during cancer‐induced muscle wasting (Figure D–F). Skeletal muscle atrophy is an established adverse effect caused by treatment with glucocorticoids . Consistently, we also observed reduced mRNA levels of Pak1 in atrophying myotubes following dexamethasone exposure in vitro (Figure E).…”

Three-Dimensional Culture Model of Skeletal Muscle Tissue with Atrophy Induced by Dexamethasone

“…In the present study, Dex was used as a muscle atrophy inducer. It has been used for inducing muscle atrophy in 2D cultured skeletal muscle cells in vitro [ 8 , 23 , 24 ]. Dex treatment induced the expression of skeletal muscle atrophy-related genes, Atrogin-1 and MuRF-1 , in myotubes and decreased the size of myotubes and the amount of muscle protein.…”

DCAF8, a novel MuRF1 interaction partner, promotes muscle atrophy

“…In initial experiments we exposed the C2C12 myotubes to 10 µM Dexa (defined as a 'mild Dexa treatment') and, as recently published, this treatment caused a decrease in MyHC protein levels in scrambled siRNA-treated control cells (Fig. 8A) (Massaccesi et al, 2016). In cells impeded for the expression of either MuRF1 or DCAF8 the loss of MyHC was less pronounced.…”

“…To this end, we differentiated C2C12 cells that were downregulated for expression of individual genes into myotubes and induced atrophy using the glucocorticoid dexamethasone (Dexa). Dexa treatment serves as an established method to investigate muscle atrophy in cell culture but widely different concentrations of this substance have been used in individual studies (Hasselgren, 1999;Clarke et al, 2007;Menconi et al, 2008;Massaccesi et al, 2016). In initial experiments we exposed the C2C12 myotubes to 10 µM Dexa (defined as a 'mild Dexa treatment') and, as recently published, this treatment caused a decrease in MyHC protein levels in scrambled siRNA-treated control cells (Fig.…”