title: Blockades of mitogen-activated protein kinase and calcineurin both change fibre-type markers in skeletal muscle culture.
abstract: Activation of either the calcineurin or the extracellular signal-regulated kinase (ERK1/2) pathway increases the percentage of slow fibres in vivo suggesting that both pathways can regulate fibre phenotypes in skeletal muscle. We investigated the effect of calcineurin blockade with cyclosporin A and mitogen-activated protein kinase kinase (MEK1/2) blockade with U0126 upon myosin heavy chain (MHC) isoform mRNA levels and activities of metabolic enzymes after 1 day, 3 days and 7 days of treatment in primary cultures of spontaneously twitching rat skeletal muscle. U0126 treatment significantly decreased MHC Ibeta mRNA levels and significantly increased MHC IIX, MHC IIB, embryonal MHC and perinatal MHC mRNA levels when compared to control. In addition, U0126 treatment significantly increased lactate dehydrogenase, creatine kinase, hexokinase, malate dehydrogenase and beta-hydroxyacyl-CoA dehydrogenase activities above control values while a significant reduction in the percentage of pyruvate dehydrogenase in the active form was also observed. Calcineurin blockade significantly decreased both MHC Ibeta and embryonal mRNA levels below control and significantly increased MHC IIX mRNA levels. Significant increases in the activities of both lactate dehydrogenase and creatine kinase above control values were also seen following cyclosporin A treatment. In conclusion, the results suggest that calcineurin upregulates slow-fibre genes and suppresses fast-fibre genes. Similarly, the ERK1/2 pathway upregulates slow-fibre MHC and suppresses fast-fibre MHC isoforms. However, the effect on enzyme activities is not fibre-type specific. The effect of U0126 on the percentage of pyruvate dehydrogenase in the active form suggests that the ERK1/2 pathway may also be involved in regulation of the phosphorylation state of this enzyme.
authors.affiliation: Muscle Research Group, Department of Biological Sciences, University of Central Lancashire, Preston PR1 2HE, UK. jhigginson1@uclan.ac.uk
authors.forename: James
authors.initials: J
authors.lastname: Higginson
authors.forename: Henning
authors.initials: H
authors.lastname: Wackerhage
authors.forename: Niall
authors.initials: N
authors.lastname: Woods
authors.forename: Peter
authors.initials: P
authors.lastname: Schjerling
authors.forename: Aivaras
authors.initials: A
authors.lastname: Ratkevicius
authors.forename: Niels
authors.initials: N
authors.lastname: Grunnet
authors.forename: Bjørn
authors.initials: B
authors.lastname: Quistorff
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000032:analysis; D002070:Butadienes / Q000494:pharmacology*; D065095:Calcineurin Inhibitors; D002478:Cells, Cultured; D016572:Cyclosporine / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors*; D018656:Muscle Fibers, Fast-Twitch / Q000378:metabolism*; D018657:Muscle Fibers, Slow-Twitch / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000235:genetics; D009570:Nitriles / Q000494:pharmacology*; D020033:Protein Isoforms / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
chemical_list: D015415:Biomarkers; D002070:Butadienes; D065095:Calcineurin Inhibitors; D004791:Enzyme Inhibitors; D009570:Nitriles; D020033:Protein Isoforms; D012333:RNA, Messenger; C113580:U 0126; D016572:Cyclosporine; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D020928:Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D020929:Mitogen-Activated Protein Kinase Kinases; D018995:Myosin Heavy Chains