Activity-dependent nuclear translocation and intranuclear distribution of NFATc in adult skeletal muscle fibers

Y Liu, Z Cseresnyés, WR Randall… - The Journal of cell …, 2001 - rupress.org
Y Liu, Z Cseresnyés, WR Randall, MF Schneider
The Journal of cell biology, 2001rupress.org
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 …
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.
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