Effects of dexamethasone on protein degradation and protease gene expression in rat L8 myotube cultures.
Mol Cell Endocrinol
; 108(1-2): 199-209, 1995 Feb 27.
Article
em En
| MEDLINE
| ID: mdl-7758836
ABSTRACT
We examined the effects of a synthetic glucocorticoid (dexamethasone; Dex) on protoeolysis and on protease messenger RNA (mRNA) concentrations in rat L8 skeletal myotube cultures. Protein degradation was measured as release of radioactive trichloroacetic acid-soluble material from intracellular proteins pre-labelled with [3H]tyrosine. Dex (1 microM) stimulated protein degradation (P < 0.01). This effect was entirely blocked by the glucocorticoid antagonist, RU38486 (mifepristone; P < 0.01). Hence, actions of Dex on muscle protein degradation are mediated via intracellular glucocorticoid receptors. Molecular mechanisms by which glucocorticoids stimulate protein degradation in skeletal muscle are not known. Here, we investigated the regulation of protease (cathepsin B, cathepsin D, proteasome C2 subunit and m-calpain) mRNA concentrations by Dex in cultured L8 muscle cells. Cathepsin B mRNA concentration was enhanced 3.3-fold by Dex. This effect was blocked by RU38486. RU38486 alone did not affect cathepsin B mRNA concentration or mRNAs of other proteases. Concentrations of cathepsin D and m-calpain mRNAs were also increased by Dex. These effects were also abolished by RU38486. Proteasome C2 mRNA was unaffected by Dex and Dex reduced alpha-tubulin mRNA. Thus, glucocorticoids specifically regulate the concentrations of mRNAs encoding some proteases in muscle cells. The regulation of protease mRNA concentration is mediated via interaction between Dex with glucocorticoid receptors and is independent of the actions of Dex on mRNA encoding house-keeping proteins. These changes may underlie glucocorticoid-dependent control of proteolysis in muscle.
Buscar no Google
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Endopeptidases
/
Dexametasona
/
Músculo Esquelético
/
Proteínas Musculares
Limite:
Animals
Idioma:
En
Revista:
Mol Cell Endocrinol
Ano de publicação:
1995
Tipo de documento:
Article
País de afiliação:
Estados Unidos