title: Modulation of skeletal muscle fiber type by mitogen-activated protein kinase signaling.
abstract: Skeletal muscle is composed of diverse fiber types, yet the underlying molecular mechanisms responsible for this diversification remain unclear. Herein, we report that the extracellular signal-regulated kinase (ERK) 1/2 pathway, but not p38 or c-Jun NH(2)-terminal kinase (JNK), is preferentially activated in fast-twitch muscles. Pharmacological blocking of ERK1/2 pathway increased slow-twitch fiber type-specific reporter activity and repressed those associated with the fast-twitch fiber phenotype in vitro. Overexpression of a constitutively active ERK2 had an opposite effect. Inhibition of ERK signaling in cultured myotubes increased slow-twitch fiber-specific protein accumulation while repressing those characteristic of fast-twitch fibers. Overexpression of MAP kinase phosphatase-1 (MKP1) in mouse and rat muscle fibers containing almost exclusively type IIb or IIx fast myosin heavy chain (MyHC) isoforms induced de novo synthesis of the slower, more oxidative type IIa and I MyHCs in a time-dependent manner. Conversion to the slower phenotype was confirmed by up-regulation of slow reporter gene activity and down-regulation of fast reporter activities in response to forced MKP1 expression in vivo. In addition, activation of ERK2 signaling induced up-regulation of fast-twitch fiber program in soleus. These data suggest that the MAPK signaling, most likely the ERK1/2 pathway, is necessary to preserve the fast-twitch fiber phenotype with a concomitant repression of slow-twitch fiber program.
authors.affiliation: Department of Animal Sciences, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Hao
authors.initials: H
authors.lastname: Shi
authors.forename: Jason M
authors.initials: JM
authors.lastname: Scheffler
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Pleitner
authors.forename: Caiyun
authors.initials: C
authors.lastname: Zeng
authors.forename: Sungkwon
authors.initials: S
authors.lastname: Park
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Hannon
authors.forename: Alan L
authors.initials: AL
authors.lastname: Grant
authors.forename: David E
authors.initials: DE
authors.lastname: Gerrard
mesh_terms: D000818:Animals; D002460:Cell Line; D054638:Dual Specificity Phosphatase 1 / Q000235:genetics / Q000378:metabolism; D018274:Electroporation; D005419:Flavonoids / Q000494:pharmacology; D015870:Gene Expression; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000235:genetics; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D018656:Muscle Fibers, Fast-Twitch / Q000187:drug effects / Q000378:metabolism*; D018657:Muscle Fibers, Slow-Twitch / Q000187:drug effects / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014162:Transfection
chemical_list: D005419:Flavonoids; D047428:Protein Kinase Inhibitors; D011993:Recombinant Fusion Proteins; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D054638:Dual Specificity Phosphatase 1; C517020:Dusp1 protein, mouse; C517021:Dusp1 protein, rat; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one