Glycogen synthase kinase 3β represses MYOGENIN function in alveolar rhabdomyosarcoma.

Abstract

MYOGENIN is a member of the muscle regulatory factor family that orchestrates an obligatory step in myogenesis, the terminal differentiation of skeletal muscle cells. A paradoxical feature of alveolar rhabdomyosarcoma (ARMS), a prevalent soft tissue sarcoma in children arising from cells with a myogenic phenotype, is the inability of these cells to undergo terminal differentiation despite the expression of MYOGENIN. The chimeric PAX3-FOXO1 fusion protein which results from a chromosomal translocation in ARMS has been implicated in blocking cell cycle arrest, preventing myogenesis from occurring. We report here that PAX3-FOXO1 enhances glycogen synthase kinase 3β (GSK3β) activity which in turn represses MYOGENIN activity. MYOGENIN is a GSK3β substrate in vitro on the basis of in vitro kinase assays and MYOGENIN is phosphorylated in ARMS-derived RH30 cells. Constitutively active GSK3β(S9A) increased the level of a phosphorylated form of MYOGENIN on the basis of western blot analysis and this effect was reversed by neutralization of the single consensus GSK3β phosphoacceptor site by mutation (S160/164A). Congruently, GSK3β inhibited the trans-activation of an E-box reporter gene by wild-type MYOGENIN, but not MYOGENIN with the S160/164A mutations. Functionally, GSK3β repressed muscle creatine kinase (MCK) promoter activity, an effect which was reversed by the S160/164A mutated MYOGENIN. Importantly, GSK3β inhibition or exogenous expression of the S160/164A mutated MYOGENIN in ARMS reduced the anchorage independent growth of RH30 cells in colony-formation assays. Thus, sustained GSK3β activity represses a critical regulatory step in the myogenic cascade, contributing to the undifferentiated, proliferative phenotype in alveolar rhabdomyosarcoma (ARMS).

• Authors: M G Dionyssiou, S Ehyai, E Avrutin, M K Connor, J C McDermott
• Journal: Cell death & disease (Cell Death Dis) Vol. 5 Pg. e1094 (Feb 27 2014) ISSN: 2041-4889 [Electronic] England
• PMID: 24577092 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• MYOG protein, human
• Myogenin
• Oncogene Proteins, Fusion
• PAX3-FOXO1A fusion protein, human
• Paired Box Transcription Factors
• Protein Kinase Inhibitors
• GSK3B protein, human
• Glycogen Synthase Kinase 3 beta
• Gsk3b protein, mouse
• Proto-Oncogene Proteins c-akt
• Glycogen Synthase Kinase 3
• Creatine Kinase, MM Form

Topics

• Animals
• COS Cells
• Cell Line, Tumor
• Cell Proliferation
• Chlorocebus aethiops
• Creatine Kinase, MM Form (genetics, metabolism)
• Electric Stimulation
• Enzyme Activation
• Gene Expression Regulation, Enzymologic
• Gene Expression Regulation, Neoplastic
• Genotype
• Glycogen Synthase Kinase 3 (antagonists & inhibitors, genetics, metabolism)
• Glycogen Synthase Kinase 3 beta
• Mice
• Mutation
• Myogenin (genetics, metabolism)
• Oncogene Proteins, Fusion (genetics, metabolism)
• Paired Box Transcription Factors (genetics, metabolism)
• Phenotype
• Phosphorylation
• Promoter Regions, Genetic
• Protein Kinase Inhibitors (pharmacology)
• Proto-Oncogene Proteins c-akt (metabolism)
• Rhabdomyosarcoma, Alveolar (enzymology, genetics, pathology)
• Time Factors
• Transcription, Genetic
• Transfection