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Activity-dependent and -independent nuclear fluxes of HDAC4 mediated by different kinases in adult skeletal muscle.

Liu Y, Randall WR, Schneider MF - J. Cell Biol. (2005)

Bottom Line: Class II histone deacetylases (HDACs) may decrease slow muscle fiber gene expression by repressing myogenic transcription factor myocyte enhancer factor 2 (MEF2).Thus, calcium transients for slow, but not fast, fiber stimulation patterns appear to provide sufficient Ca(2+)-dependent activation of nuclear CaMKII to result in net nuclear efflux of HDAC4.Nucleocytoplasmic shuttling of HDAC4-GFP in unstimulated resting fibers was not altered by KN-62, but was blocked by staurosporine, indicating that different kinases underlie nuclear efflux of HDAC4 in resting and stimulated muscle fibers.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA.

ABSTRACT
Class II histone deacetylases (HDACs) may decrease slow muscle fiber gene expression by repressing myogenic transcription factor myocyte enhancer factor 2 (MEF2). Here, we show that repetitive slow fiber type electrical stimulation, but not fast fiber type stimulation, caused HDAC4-GFP, but not HDAC5-GFP, to translocate from the nucleus to the cytoplasm in cultured adult skeletal muscle fibers. HDAC4-GFP translocation was blocked by calmodulin-dependent protein kinase (CaMK) inhibitor KN-62. Slow fiber type stimulation increased MEF2 transcriptional activity, nuclear Ca(2+) concentration, and nuclear levels of activated CaMKII, but not total nuclear CaMKII or CaM-YFP. Thus, calcium transients for slow, but not fast, fiber stimulation patterns appear to provide sufficient Ca(2+)-dependent activation of nuclear CaMKII to result in net nuclear efflux of HDAC4. Nucleocytoplasmic shuttling of HDAC4-GFP in unstimulated resting fibers was not altered by KN-62, but was blocked by staurosporine, indicating that different kinases underlie nuclear efflux of HDAC4 in resting and stimulated muscle fibers.

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Model of nuclear-cytoplasmic shuttling of HDAC4. Nuclear shuttling of HDAC in resting muscle fibers at low cytosolic and nuclear Ca2+ concentration is based on its intra-nuclear phosphorylation, 14-3-3– and CRM1-dependent nuclear export, cytosolic dephosphorylation, and subsequent nuclear reentry. In response to muscle activity, cytosolic and nuclear Ca2+ concentration are elevated (orange), nuclear CaMK is activated (red), nuclear HDAC is phosphorylated, and the rate of HDAC efflux from the nucleus is consequently increased. The various inhibitors of kinases, phosphatases, and CRM1 used in this work are indicated in blue. Nuclear HDAC inhibits MEF2 transcriptional activation of slow fiber genes (green), and the activity-dependent efflux of HDAC from the nucleus removes this inhibition.
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fig10: Model of nuclear-cytoplasmic shuttling of HDAC4. Nuclear shuttling of HDAC in resting muscle fibers at low cytosolic and nuclear Ca2+ concentration is based on its intra-nuclear phosphorylation, 14-3-3– and CRM1-dependent nuclear export, cytosolic dephosphorylation, and subsequent nuclear reentry. In response to muscle activity, cytosolic and nuclear Ca2+ concentration are elevated (orange), nuclear CaMK is activated (red), nuclear HDAC is phosphorylated, and the rate of HDAC efflux from the nucleus is consequently increased. The various inhibitors of kinases, phosphatases, and CRM1 used in this work are indicated in blue. Nuclear HDAC inhibits MEF2 transcriptional activation of slow fiber genes (green), and the activity-dependent efflux of HDAC from the nucleus removes this inhibition.

Mentions: Class II HDACs are transcriptional regulators that suppress the activity of MEF2, a transcription factor involved in slow skeletal muscle fiber type gene expression. The components in the regulation of translocation of HDACs from the nucleus to the cytoplasm are shown in Fig. 10. Our results demonstrate that HDAC4 translocates out of the nucleus, presumably in complex with the chaperone protein 14-3-3 (Wang et al., 2000) in response to Ca2+ activation of CaM kinase in the nucleus during electrical stimulation (Fig. 10, orange and red). Unexpectedly, there is a relatively high rate of balanced nuclear influx and efflux of HDAC4 in resting, unstimulated fibers, resulting in shuttling of HDAC4 between the nucleus and the cytoplasm. Shuttling of HDAC4 in resting fibers was revealed by the influx of HDAC4-GFP in the presence of a blocker (leptomycin B) of the CRM1 efflux carrier, by the net nuclear efflux of HDAC4-GFP when cytosolic PP1 and 2A were blocked by calyculin A, and by the rate of HDAC4-GFP influx after FRAP. The unidirectional flux rates in resting fibers are coincidentally roughly about equal to the net rate of efflux in fibers stimulated with the 10-Hz train pattern (a 5-s duration 10-Hz train repeated every 50 s). Thus, the increased rate of efflux activated by fiber stimulation is only about equal in magnitude to the unidirectional flux rates in a resting fiber (i.e., stimulation approximately doubles the efflux rate).


Activity-dependent and -independent nuclear fluxes of HDAC4 mediated by different kinases in adult skeletal muscle.

Liu Y, Randall WR, Schneider MF - J. Cell Biol. (2005)

Model of nuclear-cytoplasmic shuttling of HDAC4. Nuclear shuttling of HDAC in resting muscle fibers at low cytosolic and nuclear Ca2+ concentration is based on its intra-nuclear phosphorylation, 14-3-3– and CRM1-dependent nuclear export, cytosolic dephosphorylation, and subsequent nuclear reentry. In response to muscle activity, cytosolic and nuclear Ca2+ concentration are elevated (orange), nuclear CaMK is activated (red), nuclear HDAC is phosphorylated, and the rate of HDAC efflux from the nucleus is consequently increased. The various inhibitors of kinases, phosphatases, and CRM1 used in this work are indicated in blue. Nuclear HDAC inhibits MEF2 transcriptional activation of slow fiber genes (green), and the activity-dependent efflux of HDAC from the nucleus removes this inhibition.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2171787&req=5

fig10: Model of nuclear-cytoplasmic shuttling of HDAC4. Nuclear shuttling of HDAC in resting muscle fibers at low cytosolic and nuclear Ca2+ concentration is based on its intra-nuclear phosphorylation, 14-3-3– and CRM1-dependent nuclear export, cytosolic dephosphorylation, and subsequent nuclear reentry. In response to muscle activity, cytosolic and nuclear Ca2+ concentration are elevated (orange), nuclear CaMK is activated (red), nuclear HDAC is phosphorylated, and the rate of HDAC efflux from the nucleus is consequently increased. The various inhibitors of kinases, phosphatases, and CRM1 used in this work are indicated in blue. Nuclear HDAC inhibits MEF2 transcriptional activation of slow fiber genes (green), and the activity-dependent efflux of HDAC from the nucleus removes this inhibition.
Mentions: Class II HDACs are transcriptional regulators that suppress the activity of MEF2, a transcription factor involved in slow skeletal muscle fiber type gene expression. The components in the regulation of translocation of HDACs from the nucleus to the cytoplasm are shown in Fig. 10. Our results demonstrate that HDAC4 translocates out of the nucleus, presumably in complex with the chaperone protein 14-3-3 (Wang et al., 2000) in response to Ca2+ activation of CaM kinase in the nucleus during electrical stimulation (Fig. 10, orange and red). Unexpectedly, there is a relatively high rate of balanced nuclear influx and efflux of HDAC4 in resting, unstimulated fibers, resulting in shuttling of HDAC4 between the nucleus and the cytoplasm. Shuttling of HDAC4 in resting fibers was revealed by the influx of HDAC4-GFP in the presence of a blocker (leptomycin B) of the CRM1 efflux carrier, by the net nuclear efflux of HDAC4-GFP when cytosolic PP1 and 2A were blocked by calyculin A, and by the rate of HDAC4-GFP influx after FRAP. The unidirectional flux rates in resting fibers are coincidentally roughly about equal to the net rate of efflux in fibers stimulated with the 10-Hz train pattern (a 5-s duration 10-Hz train repeated every 50 s). Thus, the increased rate of efflux activated by fiber stimulation is only about equal in magnitude to the unidirectional flux rates in a resting fiber (i.e., stimulation approximately doubles the efflux rate).

Bottom Line: Class II histone deacetylases (HDACs) may decrease slow muscle fiber gene expression by repressing myogenic transcription factor myocyte enhancer factor 2 (MEF2).Thus, calcium transients for slow, but not fast, fiber stimulation patterns appear to provide sufficient Ca(2+)-dependent activation of nuclear CaMKII to result in net nuclear efflux of HDAC4.Nucleocytoplasmic shuttling of HDAC4-GFP in unstimulated resting fibers was not altered by KN-62, but was blocked by staurosporine, indicating that different kinases underlie nuclear efflux of HDAC4 in resting and stimulated muscle fibers.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA.

ABSTRACT
Class II histone deacetylases (HDACs) may decrease slow muscle fiber gene expression by repressing myogenic transcription factor myocyte enhancer factor 2 (MEF2). Here, we show that repetitive slow fiber type electrical stimulation, but not fast fiber type stimulation, caused HDAC4-GFP, but not HDAC5-GFP, to translocate from the nucleus to the cytoplasm in cultured adult skeletal muscle fibers. HDAC4-GFP translocation was blocked by calmodulin-dependent protein kinase (CaMK) inhibitor KN-62. Slow fiber type stimulation increased MEF2 transcriptional activity, nuclear Ca(2+) concentration, and nuclear levels of activated CaMKII, but not total nuclear CaMKII or CaM-YFP. Thus, calcium transients for slow, but not fast, fiber stimulation patterns appear to provide sufficient Ca(2+)-dependent activation of nuclear CaMKII to result in net nuclear efflux of HDAC4. Nucleocytoplasmic shuttling of HDAC4-GFP in unstimulated resting fibers was not altered by KN-62, but was blocked by staurosporine, indicating that different kinases underlie nuclear efflux of HDAC4 in resting and stimulated muscle fibers.

Show MeSH
Related in: MedlinePlus