title: Wnt/beta-catenin signaling activates growth-control genes during overload-induced skeletal muscle hypertrophy.
abstract: Beta-catenin is a transcriptional activator shown to regulate the embryonic, postnatal, and oncogenic growth of many tissues. In most research to date, beta-catenin activation has been the unique downstream function of the Wnt signaling pathway. However, in the heart, a Wnt-independent mechanism involving Akt-mediated phosphorylation of glycogen synthase kinase (GSK)-3beta was recently shown to activate beta-catenin and regulate cardiomyocyte growth. In this study, results have identified the activation of the Wnt/beta-catenin pathway during hypertrophy of mechanically overloaded skeletal muscle. Significant increases in beta-catenin were determined during skeletal muscle hypertrophy. In addition, the Wnt receptor, mFrizzled (mFzd)-1, the signaling mediator disheveled-1, and the transcriptional co-activator, lymphocyte enhancement factor (Lef)-1, are all increased during hypertrophy of the overloaded mouse plantaris muscle. Experiments also determined an increased association between GSK-3beta and the inhibitory frequently rearranged in advanced T cell-1 protein with no increase in GSK-3beta phosphorylation (Ser9). Finally, skeletal muscle overload resulted in increased nuclear beta-catenin/Lef-1 expression and induction of the transcriptional targets c-Myc, cyclin D1, and paired-like homeodomain transcription factor 2. Thus this study provides the first evidence that the Wnt signaling pathway induces beta-catenin/Lef-1 activation of growth-control genes during overload induced skeletal muscle hypertrophy.
authors.affiliation: University of Illinois Chicago, School of Kinesiology, USA.
authors.forename: Dustin D
authors.initials: DD
authors.lastname: Armstrong
authors.forename: Karyn A
authors.initials: KA
authors.lastname: Esser
mesh_terms: D000818:Animals; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000378:metabolism; D005786:Gene Expression Regulation; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006984:Hypertrophy / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins / Q000502:physiology*; D051821:Lymphoid Enhancer-Binding Factor 1; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000473:pathology*; D015398:Signal Transduction / Q000502:physiology*; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology*; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D051153:Wnt Proteins; D051176:beta Catenin
chemical_list: C495267:CTNNB1 protein, mouse; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; D036341:Intercellular Signaling Peptides and Proteins; C497574:Lef1 protein, mouse; D051821:Lymphoid Enhancer-Binding Factor 1; D015534:Trans-Activators; D014157:Transcription Factors; D051153:Wnt Proteins; D051176:beta Catenin; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D038362:Glycogen Synthase Kinase 3