title: Inhibition of glycogen synthase kinase-3beta activity is sufficient to stimulate myogenic differentiation.
abstract: Skeletal muscle atrophy is a prominent and disabling feature of chronic wasting diseases. Prevention or reversal of muscle atrophy by administration of skeletal muscle growth (hypertrophy)-stimulating agents such as insulin-like growth factor I (IGF-I) could be an important therapeutic strategy in these diseases. To elucidate the IGF-I signal transduction responsible for muscle formation (myogenesis) during muscle growth and regeneration, we applied IGF-I to differentiating C(2)C(12) myoblasts and evaluated the effects on phosphatidylinositol 3-kinase (PI3K)/Akt/glycogen synthase kinase-3beta (GSK-3beta) signaling and myogenesis. IGF-I caused phosphorylation and inactivation of GSK-3beta activity via signaling through the PI3K/Akt pathway. We assessed whether pharmacological inhibition of GSK-3beta with lithium chloride (LiCl) was sufficient to stimulate myogenesis. Addition of IGF-I or LiCl stimulated myogenesis, evidenced by increased myotube formation, muscle creatine kinase (MCK) activity, and troponin I (TnI) promoter transactivation during differentiation. Moreover, mRNAs encoding MyoD, Myf-5, myogenin, TnI-slow, TnI-fast, MCK, and myoglobin were upregulated in myoblasts differentiated in the presence of IGF-I or LiCl. Importantly, blockade of GSK-3beta inhibition abrogated IGF-I- but not LiCl-dependent stimulation of myogenic mRNA accumulation, suggesting that the promyogenic effects of IGF-I require GSK-3beta inactivation and revealing an important negative regulatory role for GSK-3beta in myogenesis. Therefore, this study identifies GSK-3beta as a potential target for pharmacological stimulation of muscle growth.
authors.affiliation: Department of Respiratory Medicine, Maastricht University, Maastricht, The Netherlands.
authors.forename: Jos L J
authors.initials: JL
authors.lastname: van der Velden
authors.forename: Ramon C J
authors.initials: RC
authors.lastname: Langen
authors.forename: Marco C J M
authors.initials: MC
authors.lastname: Kelders
authors.forename: Emiel F M
authors.initials: EF
authors.lastname: Wouters
authors.forename: Yvonne M W
authors.initials: YM
authors.lastname: Janssen-Heininger
authors.forename: Annemie M W J
authors.initials: AM
authors.lastname: Schols
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000502:physiology*; D002460:Cell Line; D048430:Cell Shape; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D018021:Lithium Chloride / Q000378:metabolism; D051379:Mice; D018482:Muscle, Skeletal / Q000201:enzymology / Q000254:growth & development; D011401:Promoter Regions, Genetic; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D015533:Transcriptional Activation; D019210:Troponin I / Q000235:genetics / Q000378:metabolism
chemical_list: D019210:Troponin I; D007334:Insulin-Like Growth Factor I; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D051057:Proto-Oncogene Proteins c-akt; D038362:Glycogen Synthase Kinase 3; D018021:Lithium Chloride