The Glucocorticoid Receptor and Its Direct Target Gene MuRF1 Are Required for Dexamethasone-Induced Skeletal Muscle Atrophy.

The muscle specific ubiquitin E3 ligase MuRF1 has been implicated as a key regulator of muscle atrophy under a variety of conditions, such as during synthetic glucocorticoid treatment. FOXO class transcription factors have been proposed as important regulators of MuRF1 expression, but its regulation by glucocorticoids is not well understood. The MuRF1 promoter contains a near-perfect palindromic glucocorticoid response element (GRE) 200 base pairs upstream of the transcription start site. The GRE is highly conserved in the mouse, rat, and human genes along with a directly adjacent FOXO binding element (FBE). Transient transfection assays in HepG2 cells and C2C12 myotubes demonstrate that the MuRF1 promoter is responsive to both the dexamethasone (DEX)-activated glucocorticoid receptor (GR) and FOXO1, whereas coexpression of GR and FOXO1 leads to a dramatic synergistic increase in reporter gene activity. Mutation of either the GRE or the FBE significantly impairs activation of the MuRF1 promoter. Consistent with these findings, DEX-induced upregulation of MuRF1 is significantly attenuated in mice expressing a homodimerization-deficient GR despite no effect on the degree of muscle loss in these mice vs. their wild-type counterparts. Finally, chromatin immunoprecipitation analysis reveals that both GR and FOXO1 bind to the endogenous MuRF1 promoter in C2C12 myotubes, and IGF-I inhibition of DEX-induced MuRF1 expression correlates with the loss of FOXO1 binding. These findings present new insights into the role of the GR and FOXO family of transcription factors in the transcriptional regulation of the MuRF1 gene, a direct target of the GR in skeletal muscle.

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A cell-autonomous role for the glucocorticoid receptor in skeletal muscle atrophy induced by systemic glucocorticoid exposure

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00512.2011 ◽

2012 ◽

Vol 302 (10) ◽

pp. E1210-E1220 ◽

Cited By ~ 57

Author(s):

Monica L. Watson ◽

Leslie M. Baehr ◽

Holger M. Reichardt ◽

Jan P. Tuckermann ◽

Sue C. Bodine ◽

...

Keyword(s):

Skeletal Muscle ◽

Glucocorticoid Receptor ◽

Muscle Atrophy ◽

Target Genes ◽

Prolonged Exposure ◽

Skeletal Muscle Atrophy ◽

High Dose ◽

Nerve Lesion ◽

Nutritional Deprivation

Glucocorticoids (GCs) are important regulators of skeletal muscle mass, and prolonged exposure will induce significant muscle atrophy. To better understand the mechanism of skeletal muscle atrophy induced by elevated GC levels, we examined three different models: exogenous synthetic GC treatment [dexamethasone (DEX)], nutritional deprivation, and denervation. Specifically, we tested the direct contribution of the glucocorticoid receptor (GR) in skeletal muscle atrophy by creating a muscle-specific GR-knockout mouse line (MGRe3KO) using Cre-lox technology. In MGRe3KO mice, we found that the GR is essential for muscle atrophy in response to high-dose DEX treatment. In addition, DEX regulation of multiple genes, including two important atrophy markers, MuRF1 and MAFbx, is eliminated completely in the MGRe3KO mice. In a condition where endogenous GCs are elevated, such as nutritional deprivation, induction of MuRF1 and MAFbx was inhibited, but not completely blocked, in MGRe3KO mice. In response to sciatic nerve lesion and hindlimb muscle denervation, muscle atrophy and upregulation of MuRF1 and MAFbx occurred to the same extent in both wild-type and MGRe3KO mice, indicating that a functional GR is not required to induce atrophy under these conditions. Therefore, we demonstrate conclusively that the GR is an important mediator of skeletal muscle atrophy and associated gene expression in response to exogenous synthetic GCs in vivo and that the MGRe3KO mouse is a useful model for studying the role of the GR and its target genes in multiple skeletal muscle atrophy models.

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Dual-specificity phosphatase 29 is induced during neurogenic skeletal muscle atrophy and attenuates glucocorticoid receptor activity in muscle cell culture

AJP Cell Physiology ◽

10.1152/ajpcell.00200.2020 ◽

2020 ◽

Vol 319 (2) ◽

pp. C441-C454

Author(s):

Lisa M. Cooper ◽

Rita C. West ◽

Caleb S. Hayes ◽

David S. Waddell

Keyword(s):

Skeletal Muscle ◽

Glucocorticoid Receptor ◽

Reporter Gene ◽

Muscle Cell ◽

Muscle Atrophy ◽

Muscle Cells ◽

Proximal Promoter ◽

Skeletal Muscle Atrophy ◽

Dual Specificity Phosphatase ◽

Dual Specificity

Skeletal muscle atrophy is caused by a decrease in muscle size and strength and results from a range of physiological conditions, including denervation, immobilization, corticosteroid exposure and aging. Newly named dual-specificity phosphatase 29 ( Dusp29) has been identified as a novel neurogenic atrophy-induced gene in skeletal muscle. Quantitative PCR analysis revealed that Dusp29 expression is significantly higher in differentiated myotubes compared with proliferating myoblasts. To determine how Dusp29 is transcriptionally regulated in skeletal muscle, fragments of the promoter region of Dusp29 were cloned, fused to a reporter gene, and found to be highly inducible in response to ectopic expression of the myogenic regulatory factors (MRF), MyoD and myogenin. Furthermore, site-directed mutagenesis of conserved E-box elements within the proximal promoter of Dusp29 rendered a Dusp29 reporter gene unresponsive to MRF overexpression. Dusp29, an atypical Dusp also known as Dupd1/Dusp27, was found to attenuate the ERK1/2 branch of the MAP kinase signaling pathway in muscle cells and inhibit muscle cell differentiation when ectopically expressed in proliferating myoblasts. Interestingly, Dusp29 was also found to destabilize AMPK protein while simultaneously enriching the phosphorylated pool of AMPK in muscle cells. Additionally, Dusp29 overexpression resulted in a significant increase in the glucocorticoid receptor (GR) protein and elevation in GR phosphorylation. Finally, Dusp29 was found to significantly impair the ability of the glucocorticoid receptor to function as a transcriptional activator in muscle cells treated with dexamethasone. Identifying and characterizing the function of Dusp29 in muscle provides novel insights into the molecular and cellular mechanisms for skeletal muscle atrophy.

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Skeletal muscle atrophy caused by acute pulmonary inflammation is dependent on a glycogen synthase kinase-3beta - glucocorticoid receptor signaling axis

10.1183/13993003.congress-2015.oa3494 ◽

2015 ◽

Author(s):

Ramon Langen ◽

Koen Verhees ◽

Marco Kelders ◽

Chiel De Theije ◽

Annemie Schols

Keyword(s):

Skeletal Muscle ◽

Glucocorticoid Receptor ◽

Muscle Atrophy ◽

Glycogen Synthase ◽

Pulmonary Inflammation ◽

Glycogen Synthase Kinase ◽

Skeletal Muscle Atrophy ◽

Receptor Signaling ◽

Glycogen Synthase Kinase 3Beta ◽

Signaling Axis

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Proanthocyanidins Induce miR-133b Expression to Promote Ischemic Skeletal Muscle Regeneration by Targeting MKP1

10.21203/rs.3.rs-63522/v1 ◽

2020 ◽

Author(s):

Shi Chen ◽

Chao Du ◽

Lilong Pan ◽

Qian Yang ◽

Peihe Yu ◽

...

Keyword(s):

Skeletal Muscle ◽

Muscle Regeneration ◽

Target Gene ◽

Myogenic Differentiation ◽

Limb Ischemia ◽

Skeletal Muscle Regeneration ◽

Aberrant Expression ◽

Direct Target Gene ◽

Direct Target

Abstract Background: Limb ischemic necrosis is mainly attributed to peripheral arterial disease (PAD). Reducing oxidative stress and promoting damaged skeletal muscle regeneration may be benefit for ischemic limb treatment. Proanthocyanidins (PC) is a powerful antioxidant and free radical scavenger, but little is known about its role and related molecular mechanism in limb ischemic injury. The current study was undertaken to explore its role in the damaged skeletal muscle regeneration both in vitro and vivo, and whether MicroRNAs (miRNAs) involved in this process. Methods: The potential effects of PC on the damaged muscle regeneration were explored in human skeletal muscle satellite cells (HSKMSCs) under hypoxic-ischemic condition and in mice limb ischemia model, then, aberrant expression of miRNAs in ischemic skeletal muscles were determined by microarray analysis, and regulatory mechanism of the specific miRNA on HSKMSCs myogenic differentiation was further investigated by gain and loss of functional experiments. Additionally, the direct target gene was examined by luciferase reporter assay.Results: In mice limb ischemia model, our results revealed that PC reduced oxidative stress level, significantly promoted ischemic limb damaged muscle regeneration and motor function recovery, then, aberrant expression of miRNAs in ischemic skeletal muscles were determined by microarray analysis, combine with the results of the RT-qPCR, the miR-133b-3p was proved to be the specific miRNA. In vitro, our results revealed that PC induced the overexpression of miR-133b to activate the p38-MAPK signal pathway and increased the myogenic differentiation-related molecules expression, which eventually promoted myotubes formation. Furthermore, MKP1 was confirmed a direct target gene of miR-133b.Conclusion: Our results suggest that PC display skeletal muscle protective properties that are mediated by miR-133b /MKP1/ p38-MAPK signal axis, offering a novel therapeutic opportunity for limb ischemic injury.

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