title: Insulin-like growth factor-I induces androgen receptor activation in differentiating C2C12 skeletal muscle cells.
abstract: The modulating effect of IGF-I on the regulation of AR gene expression and activation in skeletal muscle cells remains poorly understood. In this study, the effects of IGF-I treatment on AR induction and activation in the absence of AR ligands were examined. Differentiating C2C12 cells were treated with different concentrations (0-250 ng/ml) of IGF-I or for various periods of time (0-60 min) of 250 ng/ml IGF-I. Treatment of C2C12 cells with IGF-I resulted in a dose- and time-dependent increase in total AR and phosphorylated AR (Ser 213). IGF-I treatment also led to significantly increased AR mRNA expression when compared with the control. The levels of skeletal alpha-actin and myogenin mRNA, known target genes of AR, were also significantly upregulated after 5 or 10 min of treatment with IGF-I. Confocal images revealed that IGF-I stimulated nuclear localization of AR in the absence of ligands. In addition, an electrophoretic mobility shift assay indicated that IGF-I stimulated the AR DNA binding activity in a time-dependent manner. The present results suggest that IGF-I stimulates the expression and activation of AR by ligand-independent mechanism in differentiating C2C12 mouse skeletal muscle cells.
authors.affiliation: Department of Exercise Science, College of Health Sciences, Ewha Womans University, Seoul, Korea.
authors.forename: Hye Jin
authors.initials: HJ
authors.lastname: Kim
authors.forename: Won Jun
authors.initials: WJ
authors.lastname: Lee
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D002467:Cell Nucleus / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D051379:Mice; D018482:Muscle, Skeletal / Q000166:cytology*; D010766:Phosphorylation; D012333:RNA, Messenger / Q000378:metabolism; D011944:Receptors, Androgen / Q000378:metabolism*
chemical_list: D012333:RNA, Messenger; D011944:Receptors, Androgen; D007334:Insulin-Like Growth Factor I