title: Exercise and myocyte enhancer factor 2 regulation in human skeletal muscle.
abstract: Overexpression of GLUT4 in skeletal muscle enhances whole-body insulin action. Exercise increases GLUT4 gene and protein expression, and a binding site for the myocyte enhancer factor 2 (MEF-2) is required on the GLUT4 promoter for this response. However, the molecular mechanisms involved remain elusive. In various cell systems, MEF-2 regulation is a balance between transcriptional repression by histone deacetylases (HDACs) and transcriptional activation by the nuclear factor of activated T-cells (NFAT), peroxisome proliferator-activated receptor-gamma coactivator 1 (PGC-1), and the p38 mitogen-activated protein kinase. The purpose of this study was to determine if these same mechanisms regulate MEF-2 in contracting human skeletal muscle. Seven subjects performed 60 min of cycling at approximately 70% of VO2(peak). After exercise, HDAC5 was dissociated from MEF-2 and exported from the nucleus, whereas nuclear PGC-1 was associated with MEF-2. Exercise increased total and nuclear p38 phosphorylation and association with MEF-2, without changes in total or nuclear p38 protein abundance. This result was associated with p38 sequence-specific phosphorylation of MEF-2 and an increase in GLUT4 mRNA. Finally, we found no role for NFAT in MEF-2 regulation. From these data, it appears that HDAC5, PGC-1, and p38 regulate MEF-2 and could be potential targets for modulating GLUT4 expression.
authors.affiliation: Centre for Physical Activity and Nutrition, School of Exercise and Nutrition Sciences, Deakin University, 221 Burwood Highway, Burwood, Victoria 3125, Australia.
authors.forename: Sean L
authors.initials: SL
authors.lastname: McGee
authors.forename: Mark
authors.initials: M
authors.lastname: Hargreaves
mesh_terms: D000328:Adult; D001642:Bicycling; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015444:Exercise / Q000502:physiology*; D051275:Glucose Transporter Type 4; D006655:Histone Deacetylases / Q000378:metabolism; D006801:Humans; D064326:MEF2 Transcription Factors; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000235:genetics; D009124:Muscle Proteins; D018482:Muscle, Skeletal / Q000378:metabolism / Q000502:physiology*; D018006:Myogenic Regulatory Factors; D010766:Phosphorylation; D012333:RNA, Messenger / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D014018:Tissue Distribution; D014157:Transcription Factors / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D004268:DNA-Binding Proteins; D051275:Glucose Transporter Type 4; D064326:MEF2 Transcription Factors; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D018006:Myogenic Regulatory Factors; D012333:RNA, Messenger; C495692:SLC2A4 protein, human; D014157:Transcription Factors; C111264:peroxisome-proliferator-activated receptor-gamma coactivator-1; C517683:CAMK4 protein, human; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C404500:HDAC5 protein, human; D006655:Histone Deacetylases