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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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a-b) Representative images of PCNA- and cleaved caspase3-stained Purkinje cells show the effects of lentiviral delivery of different HDAC4 mutants on degenerative progression in Atm−/− mouse cerebellum.. NLS-HDAC4 (cytoplasmic) = 4A; nuclear export mutant HDAC4 (nuclear) = L1062A; Non-phosphorylatable HDAC4 (nuclear) = 3SA. Scale bar, 50 μm.c) Rota-rod tests show average latency to fall for wild type (+/+) and Atm−/− animals after injection of different HDAC4 as well as S401D lentiviral particles.d-e) Open–field tests show effects of different lentiviral HDAC4 as well as S401D on the spontaneous locomotor activity (d) and exploratory activity (e) in Atm−/−mice. Each treatment group consisted of 4-6 animals. Data are presented as mean values ± SEM.
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Figure 6: a-b) Representative images of PCNA- and cleaved caspase3-stained Purkinje cells show the effects of lentiviral delivery of different HDAC4 mutants on degenerative progression in Atm−/− mouse cerebellum.. NLS-HDAC4 (cytoplasmic) = 4A; nuclear export mutant HDAC4 (nuclear) = L1062A; Non-phosphorylatable HDAC4 (nuclear) = 3SA. Scale bar, 50 μm.c) Rota-rod tests show average latency to fall for wild type (+/+) and Atm−/− animals after injection of different HDAC4 as well as S401D lentiviral particles.d-e) Open–field tests show effects of different lentiviral HDAC4 as well as S401D on the spontaneous locomotor activity (d) and exploratory activity (e) in Atm−/−mice. Each treatment group consisted of 4-6 animals. Data are presented as mean values ± SEM.

Mentions: To verify that cytoplasmic HDAC4 prevents cell cycle re-entry and other degenerative changes in Atm−/− mice, we co-injected lentiviral particles encoding human wild-type HDAC4, a nuclear localization HDAC4 mutant (4A – R269A/R280A/K280A/R281A), a nuclear export mutant (L1062A) and a non-phosphorylatable mutant (3SA) together with shHdac4 (specific for the mouse Hdac4 message – Supplementary Fig.7a, b) into the cerebella of wild-type and Atm−/− mice. One week after injection of the two lentiviruses, gene transfer was monitored by immunohistochemistry using a human-specific HDAC4 antibody (Supplementary Fig.7c, d). In infected Atm−/− cerebellar neurons, cytoplasmic HDAC4 (4A) prevented cell cycle reentry and caspase-3 activation (Fig. 6a, b). By contrast, nuclear HDAC4 (L1062A and 3SA) resulted in cell cycle reentry and caspase-3 activation in both Atm−/− and wild-type mice (Fig. 6a, b). Reduced histone acetylation accompanied the increase in nuclear HDAC4, as confirmed by immunocytochemistry of Ac-H3 (Supplementary Fig.7e). Overexpression of unmodified human HDAC4 had little effect on either wild-type or Atm−/− neurons.


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)

a-b) Representative images of PCNA- and cleaved caspase3-stained Purkinje cells show the effects of lentiviral delivery of different HDAC4 mutants on degenerative progression in Atm−/− mouse cerebellum.. NLS-HDAC4 (cytoplasmic) = 4A; nuclear export mutant HDAC4 (nuclear) = L1062A; Non-phosphorylatable HDAC4 (nuclear) = 3SA. Scale bar, 50 μm.c) Rota-rod tests show average latency to fall for wild type (+/+) and Atm−/− animals after injection of different HDAC4 as well as S401D lentiviral particles.d-e) Open–field tests show effects of different lentiviral HDAC4 as well as S401D on the spontaneous locomotor activity (d) and exploratory activity (e) in Atm−/−mice. Each treatment group consisted of 4-6 animals. Data are presented as mean values ± SEM.
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Related In: Results  -  Collection

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Figure 6: a-b) Representative images of PCNA- and cleaved caspase3-stained Purkinje cells show the effects of lentiviral delivery of different HDAC4 mutants on degenerative progression in Atm−/− mouse cerebellum.. NLS-HDAC4 (cytoplasmic) = 4A; nuclear export mutant HDAC4 (nuclear) = L1062A; Non-phosphorylatable HDAC4 (nuclear) = 3SA. Scale bar, 50 μm.c) Rota-rod tests show average latency to fall for wild type (+/+) and Atm−/− animals after injection of different HDAC4 as well as S401D lentiviral particles.d-e) Open–field tests show effects of different lentiviral HDAC4 as well as S401D on the spontaneous locomotor activity (d) and exploratory activity (e) in Atm−/−mice. Each treatment group consisted of 4-6 animals. Data are presented as mean values ± SEM.
Mentions: To verify that cytoplasmic HDAC4 prevents cell cycle re-entry and other degenerative changes in Atm−/− mice, we co-injected lentiviral particles encoding human wild-type HDAC4, a nuclear localization HDAC4 mutant (4A – R269A/R280A/K280A/R281A), a nuclear export mutant (L1062A) and a non-phosphorylatable mutant (3SA) together with shHdac4 (specific for the mouse Hdac4 message – Supplementary Fig.7a, b) into the cerebella of wild-type and Atm−/− mice. One week after injection of the two lentiviruses, gene transfer was monitored by immunohistochemistry using a human-specific HDAC4 antibody (Supplementary Fig.7c, d). In infected Atm−/− cerebellar neurons, cytoplasmic HDAC4 (4A) prevented cell cycle reentry and caspase-3 activation (Fig. 6a, b). By contrast, nuclear HDAC4 (L1062A and 3SA) resulted in cell cycle reentry and caspase-3 activation in both Atm−/− and wild-type mice (Fig. 6a, b). Reduced histone acetylation accompanied the increase in nuclear HDAC4, as confirmed by immunocytochemistry of Ac-H3 (Supplementary Fig.7e). Overexpression of unmodified human HDAC4 had little effect on either wild-type or Atm−/− neurons.

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