title: p38 MAPK-induced nuclear factor-kappaB activity is required for skeletal muscle differentiation: role of interleukin-6.
abstract: p38 MAPK and nuclear factor-kappaB (NF-kappaB) signaling pathways have been implicated in the control of skeletal myogenesis. However, although p38 is recognized as a potent activator of myoblast differentiation, the role of NF-kappaB remains controversial. Here, we show that p38 is activated only in differentiating myocytes, whereas NF-kappaB activity is present both in proliferation and differentiation stages. NF-kappaB activation was found to be dependent on p38 activity during differentiation, being NF-kappaB an effector of p38, thus providing a novel mechanism for the promyogenic effect of p38. Activation of p38 in C2C12 cells induced the activity of NF-kappaB, in a dual way: first, by reducing IkappaBalpha levels and inducing NF-kappaB-DNA binding activity and, second, by potentiating the transactivating activity of p65-NF-kappaB. Finally, we show that interleukin (IL)-6 expression is induced in C2C12 differentiating myoblasts, in a p38- and NF-kappaB-dependent manner. Interference of IL-6 mRNA reduced, whereas its overexpression increased, the extent of myogenic differentiation; moreover, addition of IL-6 was able to rescue significantly the negative effect of NF-kappaB inhibition on this process. This study provides the first evidence of a crosstalk between p38 MAPK and NF-kappaB signaling pathways during myogenesis, with IL-6 being one of the effectors of this promyogenic mechanism.
authors.affiliation: Center for Genomic Regulation, Program on Differentiation and Cancer, E-08003 Barcelona, Spain.
authors.forename: Bernat
authors.initials: B
authors.lastname: Baeza-Raja
authors.forename: Pura
authors.initials: P
authors.lastname: Muñoz-Cánoves
mesh_terms: D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D002454:Cell Differentiation; D002455:Cell Division; D002460:Cell Line; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015151:Immunoblotting; D015850:Interleukin-6 / Q000378:metabolism*; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D015534:Trans-Activators / Q000378:metabolism; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D004791:Enzyme Inhibitors; D015850:Interleukin-6; D016328:NF-kappa B; D009687:Nuclear Proteins; D012333:RNA, Messenger; D015534:Trans-Activators; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases