Static stretch promotes MEF2A nuclear translocation and expression of neonatal myosin heavy chain in C2C12 myocytes in a calcineurin- and p38-dependent manner.
Although the effects of mechanical stimuli have been studied extensively in fully differentiated skeletal muscle and have been shown to promote changes in phenotype, including altered myosin heavy chain isoform expression, the effects of a change in mechanical environment have been poorly studied at earlier stages of skeletal muscle differentiation. In particular, the early events elicited by mechanical stimuli upon differentiating myocytes have not been investigated. In the present study, the effect of static stretch on the activation of transcriptional factors MEF2A and NFATc1, which have been shown to be involved in the differentiation and phenotype regulation of skeletal muscle, have been examined. Furthermore, putative second messenger signaling pathways that could be involved in the dephosphorylation and hence activation of these factors were also examined. We have demonstrated that static stretch application produces a robust increase in p38 phosphorylation preceding MEF2A, but not NFATc1, nuclear translocation as well as deactivation of GSK-3beta via its phosphorylation. Using SB-203580 and cyclosporine A drugs to inhibit both p38- or/and calcineurin-dependent signals, respectively, we have shown that MEF2A phosphorylation and subsequent nuclear translocation are regulated by p38 and calcineurin in a biphasic, time-dependent manner. Moreover, we also present evidence for another kinase that is involved in the stretch-related signal triggering MEF2A hyperphosphorylation, impairing its nuclear translocation, and that is related to p38. Finally, we have shown that static stretch application overnight promotes neonatal myosin heavy chain expression, which is inhibited by an inactivation of both p38 and calcineurin.
Muscle and Molecular Biology Unit, Department of Veterinary Basic Sciences, Royal Veterinary College, University of London, Royal College St., London NW1 0TU, United Kingdom.
Cyril
C
Rauch
Paul T
PT
Loughna
D021581:Active Transport, Cell Nucleus / Q000502:physiology*; D000818:Animals; D019703:Calcineurin / Q000378:metabolism*; D065095:Calcineurin Inhibitors; D002460:Cell Line; D016572:Cyclosporine / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D064326:MEF2 Transcription Factors; D051379:Mice; D032383:Myocytes, Cardiac / Q000166:cytology / Q000502:physiology*; D018006:Myogenic Regulatory Factors; D018995:Myosin Heavy Chains / Q000378:metabolism*; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins / Q000378:metabolism; D010766:Phosphorylation; D020033:Protein Isoforms / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D011897:Random Allocation; D015398:Signal Transduction / Q000502:physiology; D013314:Stress, Mechanical; D014157:Transcription Factors / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*
D065095:Calcineurin Inhibitors; D004268:DNA-Binding Proteins; D064326:MEF2 Transcription Factors; C578036:Mef2a protein, mouse; D018006:Myogenic Regulatory Factors; D050778:NFATC Transcription Factors; C494005:Nfatc1 protein, mouse; D009687:Nuclear Proteins; D020033:Protein Isoforms; D011518:Proto-Oncogene Proteins; D014157:Transcription Factors; D016572:Cyclosporine; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D048051:p38 Mitogen-Activated Protein Kinases; D038362:Glycogen Synthase Kinase 3; D019703:Calcineurin; D018995:Myosin Heavy Chains