Length of huntingtin and its polyglutamine tract influences localization and frequency of intracellular aggregates

Martindale, Diane; Hackam, Abigail S.; Wieczorek, Andrew; Ellerby, Lisa M.; Wellington, Cheryl L.; McCutcheon, Krista; Singaraja, Roshni R.; Kazemi-Esfarjani, Parsa; Devon, Richard M.; Kim, Seung Up; Bredesen, Dale E.; Tufaro, Frank; Hayden, Michael R.

doi:10.1038/ng0298-150

Cited by 452 publications

(356 citation statements)

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“…37 We developed a transient transfection system whereby primary rat striatal neurons expressed green fluorescent protein (GFP) and full-length Htt with normal repeat length (Htt15) or an expanded polyglutamine stretch (Htt138). 35 Expression of Htt138, but not Htt15, induced cell death in the cultured striatal neurons (Figure 3a). Cell body shrinkage, nuclear condensation, and neurite retraction were prominent features of these dying neurons Caspase-2 involvement in HD E Hermel et al ( Figure 3b).…”

Section: Inhibition Of Htt-induced Polyglutamine Repeatdependent Cellmentioning

confidence: 96%

“…[34][35][36] We have previously shown that Htt is cleaved in vitro by caspase-3 at amino acids 513 and 552, and by caspase-6 at amino-acid position 586. 36 However, in vivo, we found that Htt is specifically cleaved at a caspase consensus site at amino acid 552 in pyramidal cortical neurons, while the caspase consensus site at amino acid 513 does not appear to be utilized.…”

Section: Hd Is Specifically Cleaved By Caspase-2 At Caspase Consensusmentioning

confidence: 99%

“…26,27,34,35 We carried out our initial coimmunoprecipitations with caspases and Htt in 293T cells. We cotransfected 293T cells with constructs encoding either 15 or 138 polyglutamine repeats of full-length Htt or with an Nterminal truncated form of Htt (1955-15 and 1955-128; amino acids 1-548 of Htt) and a corresponding epitope-tagged caspase.…”

Section: Immunoprecipitation Of Htt/caspase Cell-death Complexesmentioning

confidence: 99%

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Specific caspase interactions and amplification are involved in selective neuronal vulnerability in Huntington's disease

et al. 2004

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Huntington's disease (HD) is an autosomal dominant progressive neurodegenerative disorder resulting in selective neuronal loss and dysfunction in the striatum and cortex. The molecular pathways leading to the selectivity of neuronal cell death in HD are poorly understood. Proteolytic processing of full-length mutant huntingtin (Htt) and subsequent events may play an important role in the selective neuronal cell death found in this disease. Despite the identification of Htt as a substrate for caspases, it is not known which caspase(s) cleaves Htt in vivo or whether regional expression of caspases contribute to selective neuronal cells loss. Here, we evaluate whether specific caspases are involved in cell death induced by mutant Htt and if this correlates with our recent finding that Htt is cleaved in vivo at the caspase consensus site 552. We find that caspase-2 cleaves Htt selectively at amino acid 552. Further, Htt recruits caspase-2 into an apoptosome-like complex. Binding of caspase-2 to Htt is polyglutamine repeat-length dependent, and therefore may serve as a critical initiation step in HD cell death. This hypothesis is supported by the requirement of caspase-2 for the death of mouse primary striatal cells derived from HD transgenic mice expressing full-length Htt (YAC72). Expression of catalytically inactive (dominant-negative) forms of caspase-2, caspase-7, and to some extent caspase-6, reduced the cell death of YAC72 primary striatal cells, while the catalytically inactive forms of caspase-3, -8, and -9 did not. Histological analysis of post-mortem human brain tissue and YAC72 mice revealed activation of caspases and enhanced caspase-2 immunoreactivity in medium spiny neurons of the striatum and the cortical projection neurons when compared to controls. Further, upregulation of caspase-2 correlates directly with decreased levels of brain-derived neurotrophic factor in the cortex and striatum of 3-month YAC72 transgenic mice and therefore suggests that these changes are early events in HD pathogenesis. These data support the involvement of caspase-2 in the selective neuronal cell death associated with HD in the striatum and cortex.

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Section: Inhibition Of Htt-induced Polyglutamine Repeatdependent Cellmentioning

confidence: 96%

Section: Hd Is Specifically Cleaved By Caspase-2 At Caspase Consensusmentioning

confidence: 99%

Section: Immunoprecipitation Of Htt/caspase Cell-death Complexesmentioning

confidence: 99%

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Specific caspase interactions and amplification are involved in selective neuronal vulnerability in Huntington's disease

et al. 2004

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“…Although mtHtt lacks a nuclear localization signal, mtHtt can translocate to the nucleus and produce neurotoxicity in cell culture models. [101][102][103][104] Reportedly, the mtHtt/SNO-GAPDH/Siah1 complex translocates to the nucleus, enabling mtHtt to contribute to toxicity. 100 Supporting Figure 4 Possible mechanism of S-nitrosylated GAPDH (SNO-GAPDH) contributing to neuronal cell damage or death.…”

Section: S-nitrosylation As a Potential Positive Regulator Of Excitotmentioning

confidence: 99%

S-Nitrosylation and uncompetitive/fast off-rate (UFO) drug therapy in neurodegenerative disorders of protein misfolding

Nakamura

Lipton

2007

Cell Death Differ

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Although activation of glutamate receptors is essential for normal brain function, excessive activity leads to a form of neurotoxicity known as excitotoxicity. Key mediators of excitotoxic damage include overactivation of N-methyl-D-aspartate (NMDA) receptors, resulting in excessive Ca 2 þ influx with production of free radicals and other injurious pathways. Overproduction of free radical nitric oxide (NO) contributes to acute and chronic neurodegenerative disorders. NO can react with cysteine thiol groups to form S-nitrosothiols and thus change protein function. S-nitrosylation can result in neuroprotective or neurodestructive consequences depending on the protein involved. Many neurodegenerative diseases manifest conformational changes in proteins that result in misfolding and aggregation. Our recent studies have linked nitrosative stress to protein misfolding and neuronal cell death. Molecular chaperones -such as protein-disulfide isomerase, glucose-regulated protein 78, and heat-shock proteins -can provide neuroprotection by facilitating proper protein folding. Here, we review the effect of S-nitrosylation on protein function under excitotoxic conditions, and present evidence that NO contributes to degenerative conditions by S-nitrosylating-specific chaperones that would otherwise prevent accumulation of misfolded proteins and neuronal cell death. In contrast, we also review therapeutics that can abrogate excitotoxic damage by preventing excessive NMDA receptor activity, in part via S-nitrosylation of this receptor to curtail excessive activity.

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“…The causative agent is a 350-kDa protein, huntingtin (Ht), with glutamine expansions in the N-terminal region (6). The toxicity of Ht in specific neurons correlates with the length of the glutamine expansion, but the mechanism of toxicity is unknown (7,8).A central event in HD is the production of an N-terminal fragment of Ht that aggregates in affected neurons during the natural progression of the disease in humans (9). In transgenic animal models an N-terminal fragment is sufficient to produce an HD-like phenotype, which also depends on the length of the Q repeat (10, 11).…”

mentioning

confidence: 99%

Aggregation of huntingtin in yeast varies with the length of the polyglutamine expansion and the expression of chaperone proteins

Krobitsch

Lindquist

2000

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

515

438

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P olyglutamine (polyQ) expansions in several unrelated proteins are responsible for at least eight inherited neurodegenerative diseases. These include Huntington's disease (HD), spinobulbar muscular atrophy, dentatorubral pallidoluysian atrophy, and spinocerebellar ataxia types 1, 2, 3, 6, and 7 (1-3). Perhaps the most baffling aspect of these diseases is that the proteins are expressed widely in brain and other tissues, yet each is toxic in a different, highly specific group of neurons and produces a distinct pathology (2).The major characteristic of HD is a selective loss of neurons in the striatum and cortex leading to movement disorders, dementia, and eventually, death (4, 5). The causative agent is a 350-kDa protein, huntingtin (Ht), with glutamine expansions in the N-terminal region (6). The toxicity of Ht in specific neurons correlates with the length of the glutamine expansion, but the mechanism of toxicity is unknown (7,8).A central event in HD is the production of an N-terminal fragment of Ht that aggregates in affected neurons during the natural progression of the disease in humans (9). In transgenic animal models an N-terminal fragment is sufficient to produce an HD-like phenotype, which also depends on the length of the Q repeat (10, 11). Aggregates are found in both the nucleus and/or the cytoplasm of affected neurons in human patients, transgenic animals, and cell lines (12). It is by no means clear, however, whether the aggregates are themselves pathogenic, simply benign byproducts (and thereby markers) of other pathogenic polyQ misfolding events, or a defense mechanism whose purpose is to reduce the interaction of toxic misfolded polyQ proteins with other proteins.Indeed, even the mechanisms underlying the aggregation of these fragments are unknown. A further complexity is that several other proteins interact with Ht. These include HAP1, HIP1, Hsp35, WW domain-containing proteins, the ubiquitin-conjugating enzyme hE2-25k, the SH3GL3 protein, cystathione ␤-synthase, and calmodulin (12)(13)(14).These problems are inherently difficult to study. Although several mammalian cell-line and transgenic-animal models exist for studying Ht, none is as readily amenable to genetic analysis as yeast. We demonstrate that the aggregation of N-terminal fragments of Ht in yeast cells depends on the length of its polyQ repeat and that this aggregation depends on the balance of chaperone protein activities in the cell. Furthermore, N-terminal fragments with up to 103 glutamines have little or no toxicity in either the aggregated or the soluble state. Thus, yeast cells should provide a valuable system for investigating general factors that affect aggregation and for determining what neuronal cell-type specific factors might inf luence toxicity. Materials and MethodsPlasmid Construction. Plasmids encoding fusions between the N-terminal region of Ht and green fluorescent protein (GFP) were the kind gift of G. Lawless (Univ. of California, Los Angeles).To create yeast expression plasmids for HtQ25 or HtQ103, DNAs were d...

show abstract

Length of huntingtin and its polyglutamine tract influences localization and frequency of intracellular aggregates

Cited by 452 publications

References 23 publications

Specific caspase interactions and amplification are involved in selective neuronal vulnerability in Huntington's disease

Specific caspase interactions and amplification are involved in selective neuronal vulnerability in Huntington's disease

S-Nitrosylation and uncompetitive/fast off-rate (UFO) drug therapy in neurodegenerative disorders of protein misfolding

Aggregation of huntingtin in yeast varies with the length of the polyglutamine expansion and the expression of chaperone proteins

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