Polyglutamine expansion of huntingtin impairs its nuclear export

Cornett, Jonathan; Cao, Fengli; Wang, Chuan En; Ross, Christopher A.; Bates, Gillian P.; Li, Shengbo Eben

doi:10.1038/ng1503

Cited by 163 publications

(130 citation statements)

References 29 publications

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“…Although HeLa cells are not of neuronal origin, they provide access to large amounts of material, which significantly aids in the identification of interacting proteins. Our Flag antibody purifications from the nuclear fraction (data not shown) repeatedly identified the previously reported Htt-interactors, CA150 and Tpr (14,15). Based on Htt's abundance in the S100 fraction, we chose this fraction for the input to our purification and subsequent investigations.…”

Section: Argonaute 2 Copurifies With Huntingtinmentioning

confidence: 81%

Huntington's disease protein contributes to RNA-mediated gene silencing through association with Argonaute and P bodies

Savas

Makusky

Ottosen

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

155

113

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Huntington's disease is a dominant autosomal neurodegenerative disorder caused by an expansion of polyglutamines in the huntingtin (Htt) protein, whose cellular function remains controversial. To gain insight into Htt function, we purified epitope-tagged Htt and identified Argonaute as associated proteins. Colocalization studies demonstrated Htt and Ago2 to be present in P bodies, and depletion of Htt showed compromised RNA-mediated gene silencing. Mouse striatal cells expressing mutant Htt showed fewer P bodies and reduced reporter gene silencing activity compared with wild-type counterparts. These data suggest that the previously reported transcriptional deregulation in HD may be attributed in part to mutant Htt's role in post-transcriptional processes.microRNA ͉ poly-glutamine ͉ RNA interference ͉ post-transcriptional gene silencing ͉ neuronal RNA granule H untington's disease (HD) is caused by an expansion of the polymorphic stretch of uninterrupted CAG trinucleotide repeats in exon 1 of the IT15 gene, resulting in a long tract of polyglutamine (polyQ) in the N terminus of the HD protein huntingtin (Htt) (1). The human Htt protein contains 3,144 amino acids, and the polyQ stretch starts at the 18th amino acid, followed by a polyproline (polyP) sequence; the remaining portion of the protein is likely to be rich in ␣-helices, many of which compose HEAT repeats (2). The length of the glutamine repeats in the unaffected population varies from 6 to 35; HD is caused by expansion to 36 or more repeats (3, 4). HD is a member of a group of at least nine diseases caused by CAG repeat expansions that includes spinocerebellar ataxias (SCAs) 1-3, 6, 7, and 17, spinobulbar muscular atrophy, and dentatorubral-pallidoluysian atrophy. The protein that is subject to polyQ expansion in each disease appears to be unrelated, and despite their widespread expression in the brain and other tissues, mutation in each protein leads to distinct characteristic neurodegeneration patterns.Htt is expressed in a variety of tissues both within and outside of the nervous system. Many proteins have been demonstrated to interact with WT Htt and/or mutant Htt, and their functions support some of the mechanisms perturbed in HD, which include transcription, signaling, trafficking/endocytosis, and metabolism/mitochondrial functions (5-10). However, Htt's precise function has proven elusive, and our poor understanding of its function remains a limiting factor to the development of successful therapeutics (11). Proteolytic processing of WT and mutant Htt has been investigated extensively and appears to play a critical role in disease pathogenesis. Caspase-6 cleavage at amino acid 586 in mouse Htt and the release of the N-terminal Htt fragment are required for neuronal dysfunction and degeneration in an HD mouse model (12), but the basis for the need for this cleavage is unclear.We set out to search for binding proteins to elucidate the normal function of Htt. We chose a biochemical approach to purify proteins associated with WT and mutant Htt and ide...

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Section: Argonaute 2 Copurifies With Huntingtinmentioning

confidence: 81%

Huntington's disease protein contributes to RNA-mediated gene silencing through association with Argonaute and P bodies

Savas

Makusky

Ottosen

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

155

113

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“…The first 17 amino acids at the N terminus have been identified as a nuclear localization signal (NLS). 28 The poly-Q stretch, which in its mutated form causes HD, is located directly C terminus of the NLS and is followed by a proline-rich domain. Exon 1 of huntingtin consists of the N-terminal NLS, the poly-Q stretch and an additional 50 amino acids of the protein.…”

Section: Structural Aspects and Protein Interactors Of Human Exon 1 Hmentioning

confidence: 99%

Mutant huntingtin can paradoxically protect neurons from death

Züchner

Brundin

2007

Cell Death Differ

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Huntington's disease (HD) is a progressive neurodegenerative disorder caused by a mutation in the gene huntingtin and characterized by motor, cognitive and psychiatric symptoms. Huntingtin contains a CAG repeat in exon 1. An expansion of this CAG repeat above 35 results in misfolding of Huntingtin, giving rise to protein aggregates and neuronal cell death. There are several transgenic HD mouse models that reproduce most of the features of the human disorder, for example protein inclusions, some neurodegeneration as well as motor and cognitive symptoms. At the same time, a subgroup of the HD transgenic mouse models exhibit dramatically reduced susceptibility to excitotoxicity. The mechanism behind this is unknown. Here, we review the literature regarding this phenomenon, attempt to explain what protein domains are crucial for this phenomenon and point toward a putative mechanism. We suggest, that the C-terminal domain of exon 1 Huntingtin, namely the proline rich domain, is responsible for mediating a neuroprotective effect against excitotoxicity. Furthermore, we point out the possible importance of this mechanism for future therapies in neurological disorders that have been suggested to be associated with excitotoxicity, for example Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis.

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“…Htt contains a signal sequence that mediates its export from the nucleus to the cytoplasm and the first 17 amino acids of htt are critical to the cytoplasmic localization of htt [6]. Here, we analyzed the essential sequence within Htt 1-17 that is responsible for the cytoplasmic targeting of htt, using sequential truncation of amino acids from both ends of Htt [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] .…”

Section: Htt 4-17 Is Essential For Cytoplasmic Targetingmentioning

confidence: 99%

“…Here, we analyzed the essential sequence within Htt 1-17 that is responsible for the cytoplasmic targeting of htt, using sequential truncation of amino acids from both ends of Htt [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] . To study the subcellular distribution of Htt 1-17 , we added an NLS and GFP to the C-terminus of Htt [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] . All the primers used to engineer the constructs are shown in Table 1, the schematic structures are shown in Figure 1.…”

Section: Htt 4-17 Is Essential For Cytoplasmic Targetingmentioning

confidence: 99%

Essential sequence of the N-terminal cytoplasmic localization-related domain of huntingtin and its effect on huntingtin aggregates

Yan

Peng

Tian

et al. 2011

Sci. China Life Sci.

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Huntington's disease (HD) is caused by abnormal CAG repeat expansion in the 5′-end of the Huntingtin (HTT) gene. In addition to the canonical C-terminal full-length huntingtin (htt) nuclear export signal, a cytoplasmic localization-related domain (CLRD) in the N-terminus of htt has recently been reported. Here, we analyzed this domain by introducing deletion and substitution mutations in a truncated N-terminal htt protein and subsequently monitored htt expression, aggregation and subcellular localization by immunocytochemistry and Western blot analysis. We demonstrated that Htt 4-17 was the essential sequence for htt cytoplasmic localization. We also found that the subcellular distribution of htt was altered when Htt 1-17 was mutated to contain amino acids of different charges, suggesting a structural requirement of Htt 1-17 for the cytoplasmic localization of htt. Deletion of the first three amino acids did not affect its association with mitochondria. We observed that defective cytoplasmic localization resulted in a reduction of total htt aggregates and increased nuclear aggregates, indicating that the subcellular distribution of the protein might influence the aggregation process. These studies provide new insight into the molecular mechanism of htt aggregation in HD.huntingtin, aggregates, cytoplasmic localization related domain, mitochondria, polyglutamine Citation:Yan Y P, Peng D T, Tian J, et al. Essential sequence of the N-terminal cytoplasmic localization-related domain of huntingtin and its effect on huntingtin aggregates.

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Polyglutamine expansion of huntingtin impairs its nuclear export

Cited by 163 publications

References 29 publications

Huntington's disease protein contributes to RNA-mediated gene silencing through association with Argonaute and P bodies

Huntington's disease protein contributes to RNA-mediated gene silencing through association with Argonaute and P bodies

Mutant huntingtin can paradoxically protect neurons from death

Essential sequence of the N-terminal cytoplasmic localization-related domain of huntingtin and its effect on huntingtin aggregates

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