The p38alpha/beta mitogen-activated protein kinases mediate recruitment of CREB-binding protein to preserve fast myosin heavy chain IId/x gene activity in myotubes.
In skeletal muscle, the transformation of fast into slow fiber type is accompanied by shifts in fiber type-specific gene expression that includes down-regulation of the adult fast fiber myosin heavy chain IId/x (MyHCIId/x) gene. Here, we report that the mitogen-activated protein kinases (MAPKs) p38alpha/beta regulate MyHCIId/x gene expression. Electrical stimulation of rabbit skeletal muscle cells with a slow fiber type activity pattern and treatment of C2C12 myotubes with Ca(2+)-ionophore inhibited p38alpha/beta MAPKs and reduced fast fiber type MyHC protein expression and promoter activity. Pharmacological inhibition of p38alpha/beta also down-regulated MyHCII gene expression. In controls, binding of the myocyte enhancer factor-2 (MEF-2) isoforms C and D as a heterodimer to a proximal consensus site within the MyHCIId/x promoter and recruitment of a transcriptional coactivator, the CREB-binding protein CBP, were observed. Overexpression of wild type MEF-2C but not of a MEF-2C mutant that cannot be phosphorylated by p38 induced promoter activity. Mutation of the MEF-2-binding site decreased the inducing effect of overexpressed CBP. Inhibition of p38alpha/beta MAPKs abolished CBP binding, whereas enforced induction of p38 by activated MAPK kinase 6 (MKK6EE) enhanced binding of CBP and increased promoter activity. Furthermore, knockdown of endogenous CBP by RNA interference eliminated promoter activation by MEF-2C or MKK6EE. In electrical stimulated and Ca(2+)-ionophore-treated myotubes, CBP was absent in complex formation at that site. Taken together, the data indicate that p38alpha/beta MAPKs-mediated coactivator recruitment at a proximal MEF-2 site is important for MyHCIId/x gene regulation in skeletal muscle.
Meissner
Joachim D
JD
Department of Physiology, Hannover Medical School, D-30625 Hannover, Germany.
Chang
Kin-Chow
KC
Kubis
Hans-Peter
HP
Nebreda
Angel R
AR
Gros
Gerolf
G
Scheibe
Renate J
RJ
D000818:Animals; D050882:CREB-Binding Protein / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D004558:Electric Stimulation; D007476:Ionophores / Q000494:pharmacology; D064326:MEF2 Transcription Factors; D051379:Mice; D048290:Mitogen-Activated Protein Kinase 11 / Q000502:physiology*; D048308:Mitogen-Activated Protein Kinase 14 / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000378:metabolism*; D018006:Myogenic Regulatory Factors / Q000502:physiology; D018995:Myosin Heavy Chains / Q000235:genetics*; D011401:Promoter Regions, Genetic; D021381:Protein Transport; D011817:Rabbits
D007476:Ionophores; D064326:MEF2 Transcription Factors; C578041:Mef2c protein, mouse; D018006:Myogenic Regulatory Factors; D050882:CREB-Binding Protein; C494364:Crebbp protein, mouse; D048290:Mitogen-Activated Protein Kinase 11; D048308:Mitogen-Activated Protein Kinase 14; D018995:Myosin Heavy Chains; D002118:Calcium