Activity-dependent nuclear translocation and intranuclear distribution of NFATc in adult skeletal muscle fibers.
TTranscription factor nuclear factor of activated T cells NFATc (NFATc1, NFAT2) may contribute to slow-twitch skeletal muscle fiber type-specific gene expression. Green fluorescence protein (GFP) or FLAG fusion proteins of either wild-type or constitutively active mutant NFATc [NFATc(S-->A)] were expressed in cultured adult mouse skeletal muscle fibers from flexor digitorum brevis (predominantly fast-twitch). Unstimulated fibers expressing NFATc(S-->A) exhibited a distinct intranuclear pattern of NFATc foci. In unstimulated fibers expressing NFATc-GFP, fluorescence was localized at the sarcomeric z-lines and absent from nuclei. Electrical stimulation using activity patterns typical of slow-twitch muscle, either continuously at 10 Hz or in 5-s trains at 10 Hz every 50 s, caused cyclosporin A-sensitive appearance of fluorescent foci of NFATc-GFP in all nuclei. Fluorescence of nuclear foci increased during the first hour of stimulation and then remained constant during a second hour of stimulation. Kinase inhibitors and ionomycin caused appearance of nuclear foci of NFATc-GFP without electrical stimulation. Nuclear translocation of NFATc-GFP did not occur with either continuous 1 Hz stimulation or with the fast-twitch fiber activity pattern of 0.1-s trains at 50 Hz every 50 s. The stimulation pattern-dependent nuclear translocation of NFATc demonstrated here could thus contribute to fast-twitch to slow-twitch fiber type transformation.
Liu
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Y
Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
Cseresnyés
Z
Z
Randall
W R
WR
Schneider
M F
MF
D021581:Active Transport, Cell Nucleus / Q000502:physiology*; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D017930:Genes, Reporter / Q000235:genetics; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007093:Imidazoles / Q000494:pharmacology; D007150:Immunohistochemistry; D064326:MEF2 Transcription Factors; D051379:Mice; D018613:Microscopy, Confocal; D018656:Muscle Fibers, Fast-Twitch / Q000187:drug effects / Q000378:metabolism; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism*; D018006:Myogenic Regulatory Factors; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism*; D012261:Ribonucleoproteins; D000068103:Serine-Arginine Splicing Factors; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism*
D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D005419:Flavonoids; D007093:Imidazoles; D064326:MEF2 Transcription Factors; D018006:Myogenic Regulatory Factors; D050778:NFATC Transcription Factors; C494003:NFATC1 protein, human; C494005:Nfatc1 protein, mouse; D009687:Nuclear Proteins; D011725:Pyridines; D011993:Recombinant Fusion Proteins; D012261:Ribonucleoproteins; C499372:SRSF2 protein, mouse; D014157:Transcription Factors; C073288:SRSF2 protein, human; D000068103:Serine-Arginine Splicing Factors; C090942:4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one