Expression and activity of C/EBPbeta and delta are upregulated by dexamethasone in skeletal muscle.
The influence of glucocorticoids on the expression and activity of the transcription factors CCAAT/enhancer binding protein (C/EBP)beta and delta in skeletal muscle was examined by treating rats or cultured L6 myotubes with dexamethasone. Treatment of rats with 10 mg/kg of dexamethasone resulted in increased C/EBPbeta and delta DNA binding activity in the extensor digitorum longus muscle as determined by electrophoretic mobility shift assay (EMSA) and supershift analysis. A similar response was noticed in dexamethasone-treated myotubes. In other experiments, myocytes were transfected with a plasmid containing a promoter construct consisting of multiple C/EBP binding elements upstream of a luciferase reporter gene. Treatment of these cells with dexamethasone resulted in a fourfold increase in luciferase activity, suggesting that glucocorticoids increase C/EBP-dependent gene activation in muscle cells. In addition, dexamethasone upregulated the protein and gene expression of C/EBPbeta and delta in the myotubes in a time- and dose-dependent fashion as determined by Western blotting and real-time PCR, respectively. The results suggest that glucocorticoids increase C/EBPbeta and delta activity and expression through a direct effect in skeletal muscle.
Yang
Hongmei
H
Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA.
Mammen
Joshua
J
Wei
Wei
W
Menconi
Michael
M
Evenson
Amy
A
Fareed
Moin
M
Petkova
Victoria
V
Hasselgren
Per-Olof
PO
D000818:Animals; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000235:genetics* / Q000378:metabolism; D051743:CCAAT-Enhancer-Binding Protein-delta; D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects; D005938:Glucocorticoids / Q000494:pharmacology*; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D018482:Muscle, Skeletal / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects
D022782:CCAAT-Enhancer-Binding Protein-beta; D022762:CCAAT-Enhancer-Binding Proteins; C497254:Cebpd protein, rat; D005938:Glucocorticoids; D014157:Transcription Factors; D051743:CCAAT-Enhancer-Binding Protein-delta; D003907:Dexamethasone