title: Androgens up-regulate transcription of the Notch inhibitor Numb in C2C12 myoblasts via Wnt/β-catenin signaling to T cell factor elements in the Numb promoter.
abstract: Androgen signaling via the androgen receptor is a key pathway that contributes to development, cell fate decisions, and differentiation, including that of myogenic progenitors. Androgens and synthetic steroids have well established anabolic actions on skeletal muscle. Wnt and Notch signaling pathways are also essential to myogenic cell fate decisions during development and tissue repair. However, the interactions among these pathways are largely unknown. Androgenic regulation of Wnt signaling has been reported. Nandrolone, an anabolic steroid, has been shown to inhibit Notch signaling and up-regulate Numb, a Notch inhibitor. To elucidate the mechanisms of interaction between nandrolone and Wnt/Notch signaling, we investigated the effects of nandrolone on Numb expression and Wnt signaling and determined the roles of Wnt signaling in nandrolone-induced Numb expression in C2C12 myoblasts. Nandrolone increased Numb mRNA and protein levels and T cell factor (Tcf) transcriptional activity via inhibition of glycogen synthase kinase 3β. Up-regulation of Numb expression by nandrolone was blocked by the Wnt inhibitors, sFRP1 and DKK1, whereas Wnt3a increased Numb mRNA and protein expression. In addition, we observed that the proximal promoter of the Numb gene had functional Tcf binding elements to which β-catenin was recruited in a manner enhanced by both nandrolone and Wnt3a. Moreover, site-directed mutagenesis indicated that the Tcf binding sites in the Numb promoter are required for the nandrolone-induced Numb transcriptional activation in this cell line. These results reveal a novel molecular mechanism underlying up-regulation of Numb transcription with a critical role for increased canonical Wnt signaling. In addition, the data identify Numb as a novel target gene of the Wnt signaling pathway by which Wnts would be able to inhibit Notch signaling.
authors: James J. Peter Veterans Affairs Medical Center, Bronx, New York 10468, USA.
authors: Xin-Hua
authors: XH
authors: Liu
authors: Yong
authors: Y
authors: Wu
authors: Shen
authors: S
authors: Yao
authors: Alice C
authors: AC
authors: Levine
authors: Alexander
authors: A
authors: Kirschenbaum
authors: Lauren
authors: L
authors: Collier
authors: William A
authors: WA
authors: Bauman
authors: Christopher P
authors: CP
authors: Cardozo
mesh_terms: D000728:Androgens / Q000494:pharmacology; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D015153:Blotting, Western; D002460:Cell Line; D015870:Gene Expression / Q000187:drug effects; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D018613:Microscopy, Confocal; D009154:Mutation; D032446:Myoblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D009277:Nandrolone / Q000494:pharmacology*; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011485:Protein Binding; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D051820:TCF Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism*; D060509:Wnt3A Protein / Q000235:genetics / Q000378:metabolism; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism*
chemical_list: D000728:Androgens; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; C106293:Numb protein, mouse; D051820:TCF Transcription Factors; D051153:Wnt Proteins; D060509:Wnt3A Protein; D051176:beta Catenin; D009277:Nandrolone; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D038362:Glycogen Synthase Kinase 3
keywords: Anabolic Steroids; Androgen; Androgen Receptor; Myogenesis; Notch; Numb; Wnt Signaling
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