title: The mitogen-activated protein kinase cascade promotes myoblast cell survival by stabilizing the cyclin-dependent kinase inhibitor, p21WAF1 protein.
abstract: During myogenesis, proliferating myoblasts withdraw from the cell cycle and are either eliminated by programmed cell death or differentiate into mature myotubes. Previous studies indicate that mitogen-activated protein kinase (MAPK) activity is significantly induced with the onset of terminal differentiation of C2 myoblasts. We have investigated the part played by the MAPK pathway in the differentiation of C2 myoblasts. Specific activation of MAPK by expression of an active Raf1-estrogen receptor chimera protein reduced significantly the number of myoblasts undergoing programmed cell death in the differentiation medium. Activation of Raf1 prevented the proteolytic activation of the proapoptotic caspase 9-protein during differentiation. The antiapoptotic function of Raf1 correlated with accumulation of the p21WAF1 protein resulting from its increased stability. Antisense expression of p21 was used to determine whether the p21WAF1 protein mediated the antiapoptotic activity of Raf1. Reduction of p21WAF1 protein in muscle cells abolished the antiapoptotic activity of the MAPK pathway. We conclude that MAPK contributes to muscle differentiation by preventing apoptotic cell death of differentiating myoblasts and that this activity is mediated by stabilization of the p21WAF1 protein.
authors.affiliation: Department of Biochemistry, Rappaport Institute for Research in the Medical Sciences, Faculty of Medicine, Technion-Israel Institute of Technology, P. O. Box 9649, Haifa 31096, Israel.
authors.forename: Olga
authors.initials: O
authors.lastname: Ostrovsky
authors.forename: Eyal
authors.initials: E
authors.lastname: Bengal
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000235:genetics / Q000378:metabolism*; D016373:DNA, Antisense; D015870:Gene Expression; D020935:MAP Kinase Signaling System / Q000502:physiology*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D018482:Muscle, Skeletal / Q000166:cytology / Q000201:enzymology; D032446:Myoblasts / Q000166:cytology* / Q000201:enzymology*; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism
chemical_list: D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D016373:DNA, Antisense; D019908:Proto-Oncogene Proteins c-raf; D020928:Mitogen-Activated Protein Kinases