title: Mitogen-activated protein kinase signaling is necessary for the maintenance of skeletal muscle mass.
abstract: The signal transduction cascades that maintain muscle mass remain to be fully defined. Herein, we report that inhibition of extracellular signal-regulated kinase 1/2 (ERK1/2) signaling in vitro decreases myotube size and protein content after 3-day treatment with a MEK inhibitor. Neither p38 nor JNK inhibitors had any effect on myotube size or morphology. ERK1/2 inhibition also upregulated gene transcription of atrogin-1 and muscle-specific RING finger protein 1 and downregulated the phosphorylation of Akt and its downstream kinases. Forced expression of enhanced green fluorescent protein-tagged MAPK phosphatase 1 (MKP-1) in soleus and gastrocnemius muscles decreased both fiber size and reporter activity. This atrophic effect of MKP-1 was time dependent. Analysis of the reporter activity in vivo revealed that the activities of nuclear factor-kappaB and 26S proteasome were differentially activated in slow and fast muscles, suggesting muscle type-specific mechanisms may be utilized. Together, these findings suggest that MAPK signaling is necessary for the maintenance of skeletal muscle mass because inhibition of these signaling cascades elicits muscle atrophy in vitro and in vivo.
authors.affiliation: Dept. 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: Caiyun
authors.initials: C
authors.lastname: Zeng
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Pleitner
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; D002478:Cells, Cultured; D054638:Dual Specificity Phosphatase 1 / Q000378:metabolism; D017930:Genes, Reporter; D020935:MAP Kinase Signaling System / Q000502:physiology*; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics / Q000378:metabolism*; D018656:Muscle Fibers, Fast-Twitch / Q000201:enzymology / Q000473:pathology; D018657:Muscle Fibers, Slow-Twitch / Q000201:enzymology / Q000473:pathology; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000473:pathology; D009133:Muscular Atrophy / Q000378:metabolism* / Q000473:pathology; D016328:NF-kappa B / Q000378:metabolism; D010766:Phosphorylation / Q000502:physiology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D044843:SKP Cullin F-Box Protein Ligases / Q000235:genetics / Q000378:metabolism; D000070584:Tripartite Motif Proteins; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism
chemical_list: D009124:Muscle Proteins; D016328:NF-kappa B; D000070584:Tripartite Motif Proteins; C486692:Fbxo32 protein, rat; D044843:SKP Cullin F-Box Protein Ligases; C499086:Trim63 protein, rat; D044767:Ubiquitin-Protein Ligases; D051057:Proto-Oncogene Proteins c-akt; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D054638:Dual Specificity Phosphatase 1; C517021:Dusp1 protein, rat; D046988:Proteasome Endopeptidase Complex