title: Inhibition of ryanodine receptor 1 in fast skeletal muscle fibers induces a fast-to-slow muscle fiber type transition.
abstract: Skeletal muscle fiber type is regulated by innervation-induced cell signaling including calcium release mechanisms that lead to transcriptional activation of fiber type-specific genes. Avian fast pectoralis major (PM) and slow medial adductor (MA) muscles differentially control expression of the slow myosin heavy chain 2 (slow MyHC2) gene. We report here that slow MyHC2 gene expression in fast PM muscle fibers is repressed by endogenous activity of the ryanodine receptor 1 (RyR1). Inhibition of RyR1 with ryanodine led to expression of the slow MyHC2 gene in innervated PM muscle fibers in vitro. Administration of ryanodine to innervated PM muscle fibers also decreased protein kinase C (PKC) activity, the reduction of which is necessary for slow MyHC2 gene expression in both PM and MA muscle fibers. Furthermore, RyR1 inhibition increased slow MyHC2 promoter activity in innervated PM muscle fibers and enhanced transcriptional activities of nuclear factor of activated T cells (NFAT) and myocyte enhancer factor 2 (MEF2), as well as their interactions with their respective binding sites of the slow MyHC2 promoter. These results indicate that RyR1 activity in innervated fast PM muscle fibers contributes to the cell type-specific repression of slow muscle specific genes.
authors.affiliation: Department of Cell Biology and Anatomy, Chicago Medical School, 3333 Green Bay Road, North Chicago, IL 60064, USA.
authors.forename: Theresa
authors.initials: T
authors.lastname: Jordan
authors.forename: Hongbin
authors.initials: H
authors.lastname: Jiang
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.forename: Joseph X
authors.initials: JX
authors.lastname: DiMario
mesh_terms: D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002642:Chick Embryo; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D007150:Immunohistochemistry; D064326:MEF2 Transcription Factors; D018656:Muscle Fibers, Fast-Twitch / Q000378:metabolism*; D018657:Muscle Fibers, Slow-Twitch / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism*; D009132:Muscles / Q000166:cytology / Q000378:metabolism; D032446:Myoblasts / Q000378:metabolism; D018006:Myogenic Regulatory Factors; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins / Q000378:metabolism; D010641:Phenotype; D011401:Promoter Regions, Genetic; D011493:Protein Kinase C / Q000378:metabolism; D012433:Ryanodine / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000737:chemistry / Q000378:metabolism*; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection
chemical_list: D004268:DNA-Binding Proteins; D064326:MEF2 Transcription Factors; D018006:Myogenic Regulatory Factors; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D014157:Transcription Factors; D012433:Ryanodine; D004247:DNA; D011493:Protein Kinase C; D002118:Calcium