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Nuclear accumulation of HDAC4 in ATM deficiency promotes neurodegeneration in ataxia telangiectasia.

Li J, Chen J, Ricupero CL, Hart RP, Schwartz MS, Kusnecov A, Herrup K - Nat. Med. (2012)

Bottom Line: To remain cytoplasmic, HDAC4 must be phosphorylated.The activity of the HDAC4 phosphatase, protein phosphatase 2A (PP2A), is downregulated by ATM-mediated phosphorylation.In ATM deficiency, enhanced PP2A activity leads to HDAC4 dephosphorylation and the nuclear accumulation of HDAC4.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology and Neuroscience, Nelson Biological Laboratories, Rutgers University, Piscataway, New Jersey, USA.

ABSTRACT
Ataxia telangiectasia is a neurodegenerative disease caused by mutation of the Atm gene. Here we report that ataxia telangiectasia mutated (ATM) deficiency causes nuclear accumulation of histone deacetylase 4 (HDAC4) in neurons and promotes neurodegeneration. Nuclear HDAC4 binds to chromatin, as well as to myocyte enhancer factor 2A (MEF2A) and cAMP-responsive element binding protein (CREB), leading to histone deacetylation and altered neuronal gene expression. Blocking either HDAC4 activity or its nuclear accumulation blunts these neurodegenerative changes and rescues several behavioral abnormalities of ATM-deficient mice. Full rescue of the neurodegeneration, however, also requires the presence of HDAC4 in the cytoplasm, suggesting that the ataxia telangiectasia phenotype results both from a loss of cytoplasmic HDAC4 as well as its nuclear accumulation. To remain cytoplasmic, HDAC4 must be phosphorylated. The activity of the HDAC4 phosphatase, protein phosphatase 2A (PP2A), is downregulated by ATM-mediated phosphorylation. In ATM deficiency, enhanced PP2A activity leads to HDAC4 dephosphorylation and the nuclear accumulation of HDAC4. Our results define a crucial role of the cellular localization of HDAC4 in the events leading to ataxia telangiectasia neurodegeneration.

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Inhibition of HDAC4 and blocking its nuclear accumulation partially reverses the A-T phenotypea) TSA injection reverses neuronal degeneration markers in the Atm−/− cerebellum. Fluorescent images of Atm−/− brain sections immunostained for cleaved caspase-3 as well as PCNA and cyclin D1. White arrows indicate the labeled Purkinje cells. Scale bar, 25μm.b) Quantification of the degeneration markers for the experiment illustrated in (a). Each bar represents the average of three independent experiments; error bars denote SEM.c) Immunoblot assays of neuronal and cell cycle genes in mice cerebella lysates prepared from DMSO- or TSA-injected wild-type and Atm−/− mice)d) Quantification of western blot bands illustrated in panel (c). Error bars denotes standard deviations.e) Effects of TSA on the motor function of Atm−/− and wild-type animals. Motor performance measured as the average latency before falling from a rota-rod. Each treatment group consisted of 4-6 animals.f-g) Effects of TSA on the spontaneous locomotor activities (f) and the exploratory activities (g) in Atm−/−mice were observed by open-field test. Data are presented as mean values ± SEM.
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Figure 3: Inhibition of HDAC4 and blocking its nuclear accumulation partially reverses the A-T phenotypea) TSA injection reverses neuronal degeneration markers in the Atm−/− cerebellum. Fluorescent images of Atm−/− brain sections immunostained for cleaved caspase-3 as well as PCNA and cyclin D1. White arrows indicate the labeled Purkinje cells. Scale bar, 25μm.b) Quantification of the degeneration markers for the experiment illustrated in (a). Each bar represents the average of three independent experiments; error bars denote SEM.c) Immunoblot assays of neuronal and cell cycle genes in mice cerebella lysates prepared from DMSO- or TSA-injected wild-type and Atm−/− mice)d) Quantification of western blot bands illustrated in panel (c). Error bars denotes standard deviations.e) Effects of TSA on the motor function of Atm−/− and wild-type animals. Motor performance measured as the average latency before falling from a rota-rod. Each treatment group consisted of 4-6 animals.f-g) Effects of TSA on the spontaneous locomotor activities (f) and the exploratory activities (g) in Atm−/−mice were observed by open-field test. Data are presented as mean values ± SEM.

Mentions: Our data indicate that shifting the location of HDAC4 from cytoplasm to nucleus is neurotoxic. Curiously, HDAC4 knockout mice have smaller brains, which suggests that genetic deletion of HDAC4 is also neurotoxic14. To explore this potential discrepancy, we treated Atm−/− and wild-type mice with trichostatin A (TSA), a classic HDAC inhibitor25-27. We used Na-butyrate, a Class I HDAC inhibitor, as a control. After seven days of TSA treatment, the levels of markers of degeneration such as cleaved caspase-3 and the cell cycle markers PCNA and cyclin D1 were substantially reduced from those normally found in Atm−/− cerebellum (Fig. 3a, b); neuronal survival proteins, by contrast were increased (Fig. 3c, d). Na-butyrate had little effect (Supplementary Fig. 4a, b).


Nuclear accumulation of HDAC4 in ATM deficiency promotes neurodegeneration in ataxia telangiectasia.

Li J, Chen J, Ricupero CL, Hart RP, Schwartz MS, Kusnecov A, Herrup K - Nat. Med. (2012)

Inhibition of HDAC4 and blocking its nuclear accumulation partially reverses the A-T phenotypea) TSA injection reverses neuronal degeneration markers in the Atm−/− cerebellum. Fluorescent images of Atm−/− brain sections immunostained for cleaved caspase-3 as well as PCNA and cyclin D1. White arrows indicate the labeled Purkinje cells. Scale bar, 25μm.b) Quantification of the degeneration markers for the experiment illustrated in (a). Each bar represents the average of three independent experiments; error bars denote SEM.c) Immunoblot assays of neuronal and cell cycle genes in mice cerebella lysates prepared from DMSO- or TSA-injected wild-type and Atm−/− mice)d) Quantification of western blot bands illustrated in panel (c). Error bars denotes standard deviations.e) Effects of TSA on the motor function of Atm−/− and wild-type animals. Motor performance measured as the average latency before falling from a rota-rod. Each treatment group consisted of 4-6 animals.f-g) Effects of TSA on the spontaneous locomotor activities (f) and the exploratory activities (g) in Atm−/−mice were observed by open-field test. Data are presented as mean values ± SEM.
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Related In: Results  -  Collection

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Figure 3: Inhibition of HDAC4 and blocking its nuclear accumulation partially reverses the A-T phenotypea) TSA injection reverses neuronal degeneration markers in the Atm−/− cerebellum. Fluorescent images of Atm−/− brain sections immunostained for cleaved caspase-3 as well as PCNA and cyclin D1. White arrows indicate the labeled Purkinje cells. Scale bar, 25μm.b) Quantification of the degeneration markers for the experiment illustrated in (a). Each bar represents the average of three independent experiments; error bars denote SEM.c) Immunoblot assays of neuronal and cell cycle genes in mice cerebella lysates prepared from DMSO- or TSA-injected wild-type and Atm−/− mice)d) Quantification of western blot bands illustrated in panel (c). Error bars denotes standard deviations.e) Effects of TSA on the motor function of Atm−/− and wild-type animals. Motor performance measured as the average latency before falling from a rota-rod. Each treatment group consisted of 4-6 animals.f-g) Effects of TSA on the spontaneous locomotor activities (f) and the exploratory activities (g) in Atm−/−mice were observed by open-field test. Data are presented as mean values ± SEM.
Mentions: Our data indicate that shifting the location of HDAC4 from cytoplasm to nucleus is neurotoxic. Curiously, HDAC4 knockout mice have smaller brains, which suggests that genetic deletion of HDAC4 is also neurotoxic14. To explore this potential discrepancy, we treated Atm−/− and wild-type mice with trichostatin A (TSA), a classic HDAC inhibitor25-27. We used Na-butyrate, a Class I HDAC inhibitor, as a control. After seven days of TSA treatment, the levels of markers of degeneration such as cleaved caspase-3 and the cell cycle markers PCNA and cyclin D1 were substantially reduced from those normally found in Atm−/− cerebellum (Fig. 3a, b); neuronal survival proteins, by contrast were increased (Fig. 3c, d). Na-butyrate had little effect (Supplementary Fig. 4a, b).

Bottom Line: To remain cytoplasmic, HDAC4 must be phosphorylated.The activity of the HDAC4 phosphatase, protein phosphatase 2A (PP2A), is downregulated by ATM-mediated phosphorylation.In ATM deficiency, enhanced PP2A activity leads to HDAC4 dephosphorylation and the nuclear accumulation of HDAC4.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology and Neuroscience, Nelson Biological Laboratories, Rutgers University, Piscataway, New Jersey, USA.

ABSTRACT
Ataxia telangiectasia is a neurodegenerative disease caused by mutation of the Atm gene. Here we report that ataxia telangiectasia mutated (ATM) deficiency causes nuclear accumulation of histone deacetylase 4 (HDAC4) in neurons and promotes neurodegeneration. Nuclear HDAC4 binds to chromatin, as well as to myocyte enhancer factor 2A (MEF2A) and cAMP-responsive element binding protein (CREB), leading to histone deacetylation and altered neuronal gene expression. Blocking either HDAC4 activity or its nuclear accumulation blunts these neurodegenerative changes and rescues several behavioral abnormalities of ATM-deficient mice. Full rescue of the neurodegeneration, however, also requires the presence of HDAC4 in the cytoplasm, suggesting that the ataxia telangiectasia phenotype results both from a loss of cytoplasmic HDAC4 as well as its nuclear accumulation. To remain cytoplasmic, HDAC4 must be phosphorylated. The activity of the HDAC4 phosphatase, protein phosphatase 2A (PP2A), is downregulated by ATM-mediated phosphorylation. In ATM deficiency, enhanced PP2A activity leads to HDAC4 dephosphorylation and the nuclear accumulation of HDAC4. Our results define a crucial role of the cellular localization of HDAC4 in the events leading to ataxia telangiectasia neurodegeneration.

Show MeSH
Related in: MedlinePlus