title: Skeletal muscle 11beta-HSD1 controls glucocorticoid-induced proteolysis and expression of E3 ubiquitin ligases atrogin-1 and MuRF-1.
abstract: Recent studies demonstrated expression and activity of the intracellular cortisone-cortisol shuttle 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) in skeletal muscle and inhibition of 11beta-HSD1 in muscle cells improved insulin sensitivity. Glucocorticoids induce muscle atrophy via increased expression of the E3 ubiquitin ligases Atrogin-1 (Muscle Atrophy F-box (MAFbx)) and MuRF-1 (Muscle RING-Finger-1). We hypothesized that 11beta-HSD1 controls glucocorticoid-induced expression of atrophy E3 ubiquitin ligases in skeletal muscle. Primary human myoblasts were generated from healthy volunteers. 11beta-HSD1-dependent protein degradation was analyzed by [(3)H]-tyrosine release assay. RT-PCR was used to determine mRNA expression of E3 ubiquitin ligases and 11beta-HSD1 activity was measured by conversion of radioactively labeled [(3)H]-cortisone to [(3)H]-cortisol separated by thin-layer chromatography. We here demonstrate that 11beta-HSD1 is expressed and biologically active in interconverting cortisone to active cortisol in murine skeletal muscle cells (C2C12) as well as in primary human myotubes. 11Beta-HSD1 expression increased during differentiation from myoblasts to mature myotubes (p < 0.01), suggesting a role of 11beta-HSD1 in skeletal muscle growth and differentiation. Treatment with cortisone increased protein degradation by about 20% (p < 0.001), which was paralleled by an elevation of Atrogin-1 and MuRF-1 mRNA expression (p < 0.01, respectively). Notably, pre-treatment with the 11beta-HSD1 inhibitor carbenoxolone (Cbx) completely abolished the effect of cortisone on protein degradation as well as on Atrogin-1 and MuRF-1 expression. In summary, our data suggest that 11beta-HSD1 controls glucocorticoid-induced protein degradation in human and murine skeletal muscle via regulation of the E3 ubiquitin ligases Atrogin-1 and MuRF-1.
authors.affiliation: Department of Endocrinology, Diabetes and Nutrition, Charité-Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Katrin
authors.initials: K
authors.lastname: Biedasek
authors.forename: Janin
authors.initials: J
authors.lastname: Andres
authors.forename: Knut
authors.initials: K
authors.lastname: Mai
authors.forename: Stephanie
authors.initials: S
authors.lastname: Adams
authors.forename: Simone
authors.initials: S
authors.lastname: Spuler
authors.forename: Jens
authors.initials: J
authors.lastname: Fielitz
authors.forename: Joachim
authors.initials: J
authors.lastname: Spranger
mesh_terms: D043205:11-beta-Hydroxysteroid Dehydrogenase Type 1 / Q000502:physiology*; D002478:Cells, Cultured; D005938:Glucocorticoids / Q000494:pharmacology; D006801:Humans; D032342:Muscle Cells / Q000378:metabolism; D018485:Muscle Fibers, Skeletal / Q000201:enzymology; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D032446:Myoblasts / Q000166:cytology; D012333:RNA, Messenger / Q000032:analysis; D044843:SKP Cullin F-Box Protein Ligases / Q000235:genetics / Q000378:metabolism*; D000070584:Tripartite Motif Proteins; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
chemical_list: D005938:Glucocorticoids; D009124:Muscle Proteins; D012333:RNA, Messenger; D000070584:Tripartite Motif Proteins; D043205:11-beta-Hydroxysteroid Dehydrogenase Type 1; C440907:FBXO32 protein, human; D044843:SKP Cullin F-Box Protein Ligases; C440908:TRIM63 protein, human; D044767:Ubiquitin-Protein Ligases