Ataxin-1

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Ataxin-1

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Ataxin-1

<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">Ataxin-1</th>
</tr>
<tr>
<td class="label">Gene</td>
<td>[ATXN1](/genes/atxn1)</td>
</tr>
<tr>
<td class="label">UniProt</td>
<td><a href="https://www.uniprot.org/uniprot/P54253" target="_blank">P54253</a></td>
</tr>
<tr>
<td class="label">PDB</td>
<td><a href="https://www.rcsb.org/structure/1OA8" target="_blank">1OA8</a></td>
</tr>
<tr>
<td class="label">Mol. Weight</td>
<td>87 kDa (normal), variable with expansion</td>
</tr>
<tr>
<td class="label">Localization</td>
<td>Nucleus</td>
</tr>
<tr>
<td class="label">Family</td>
<td>Ataxin family</td>
</tr>
<tr>
<td class="label">Diseases</td>
<td>[Spinocerebellar Ataxia Type 1](/diseases/spinocerebellar-ataxias)</td>
</tr>
</table>

Ataxin-1

Overview

...

Ataxin-1

<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">Ataxin-1</th>
</tr>
<tr>
<td class="label">Gene</td>
<td>[ATXN1](/genes/atxn1)</td>
</tr>
<tr>
<td class="label">UniProt</td>
<td><a href="https://www.uniprot.org/uniprot/P54253" target="_blank">P54253</a></td>
</tr>
<tr>
<td class="label">PDB</td>
<td><a href="https://www.rcsb.org/structure/1OA8" target="_blank">1OA8</a></td>
</tr>
<tr>
<td class="label">Mol. Weight</td>
<td>87 kDa (normal), variable with expansion</td>
</tr>
<tr>
<td class="label">Localization</td>
<td>Nucleus</td>
</tr>
<tr>
<td class="label">Family</td>
<td>Ataxin family</td>
</tr>
<tr>
<td class="label">Diseases</td>
<td>[Spinocerebellar Ataxia Type 1](/diseases/spinocerebellar-ataxias)</td>
</tr>
</table>

Ataxin-1

Overview

Ataxin-1 is a pathogenic protein encoded by the [ATXN1](/genes/atxn1) gene that causes [Spinocerebellar Ataxia Type 1 (SCA1)](/diseases/spinocerebellar-ataxias) when its CAG trinucleotide repeat expands beyond a critical threshold[@orr1993]. This protein belongs to the Ataxin family and has a molecular weight of approximately 87 kDa in its normal form, though the expanded polyglutamine version exhibits variable molecular weight depending on repeat length[@burright1995]. Ataxin-1 is primarily localized to the nucleus of [neurons](/entities/neurons), where it exerts its normal physiological functions and, in disease states, forms toxic aggregates that drive neurodegeneration[@cummings2001].

The discovery of ATXN1 as the causative gene for SCA1 represented a landmark in understanding autosomal dominant cerebellar ataxias and provided a foundational model for studying polyglutamine expansion diseases, which include Huntington's disease, several other spinocerebellar ataxias, and spinal bulbar muscular atrophy[@gusella2000].

Normal Physiological Function

Under physiological conditions, Ataxin-1 performs essential functions in neuronal development, transcriptional regulation, and cellular homeostasis. The protein contains an AXH (ataxin-1 and HBP1) domain that mediates protein-protein interactions with various transcription factors and co-regulators[@mizutani2005].

Transcriptional Regulation

Ataxin-1 interacts with several transcriptional regulators including:

RORα (Retinoic Acid-Related Orphan Receptor Alpha): A nuclear receptor critical for cerebellar Purkinje cell development and function
HDAC3 (Histone Deacetylase 3): Modulates gene expression through chromatin remodeling
CREB (cAMP Response Element-Binding Protein): A key transcription factor in neuronal plasticity and survival
BCL6: A transcriptional repressor involved in immune function and neuronal development[@serra2006]

Cellular Signaling

Beyond transcriptional regulation, Ataxin-1 participates in multiple signaling pathways:

Wnt/β-catenin signaling: Through interaction with HBP1, Ataxin-1 modulates this developmental pathway
[mTOR](/mechanisms/mtor-signaling-pathway) signaling: Ataxin-1 regulates [autophagy](/entities/autophagy) and protein homeostasis
DNA damage response: The protein localizes to DNA damage foci and participates in repair mechanisms[@chen2024]

Pathogenic Mechanisms in SCA1

Polyglutamine Expansion

The critical pathogenic event in SCA1 is the expansion of a CAG trinucleotide repeat in the first exon of [ATXN1](/genes/atxn1), resulting in an expanded polyglutamine (polyQ) tract in the encoded protein[@orr1993]. Normal individuals have 6-44 CAG repeats, while SCA1 patients typically have 41-81 repeats, with repeat lengths above 45 being fully penetrant[@nday2020].

Nuclear Aggregation and Toxicity

Expanded Ataxin-1 misfolds and forms insoluble nuclear inclusions (NIs) that sequester other cellular proteins. These aggregates:

Disrupt transcriptional programs: NIs sequester transcription factors including RORα, leading to dysregulation of genes essential for Purkinje cell survival[@kim2020]

Impair proteostasis: The aggregates overwhelm cellular protein quality control mechanisms

Trigger ER stress: Misfolded protein accumulation activates [unfolded protein response](/entities/unfolded-protein-response) pathways

Induce mitochondrial dysfunction: Energy metabolism is compromised in affected neurons[@chiu2019]

Selective Neuronal Vulnerability

SCA1 predominantly affects cerebellar Purkinje cells, brainstem nuclei, and spinal cord motor neurons. This selective vulnerability is attributed to:

High ATXN1 expression: Cerebellar Purkinje cells exhibit particularly high levels of ATXN1
RORα dependence: The loss of RORα function is especially detrimental to Purkinje cell survival
Impaired protein clearance: Reduced autophagy capacity in Purkinje cells makes them susceptible to aggregate accumulation
Calcium dysregulation: Altered calcium signaling amplifies cellular stress[@zoghbi2013]

Role in Other Neurodegenerative Diseases

While SCA1 is the primary disease associated with Ataxin-1 expansion, the protein has been implicated in other neurodegenerative conditions:

Alzheimer's Disease

Recent studies have identified interactions between Ataxin-1 and proteins involved in [Alzheimer's disease](/diseases/alzheimers-disease) pathogenesis. Ataxin-1 may modulate:

[Tau](/proteins/tau) phosphorylation: Through effects on GSK3β and other kinases
Amyloid-β processing: Via transcriptional regulation of [APP](/entities/app-protein)-processing enzymes
Synaptic function: Loss of Ataxin-1 function may exacerbate synaptic deficits[@shiwl2022]

Parkinson's Disease

Evidence suggests that Ataxin-1 may interact with [α-synuclein](/proteins/alpha-synuclein) (encoded by [SNCA](/genes/snca)) and influence:

Lewy body formation: Potential co-aggregation with α-synuclein
Dopaminergic neuron survival: Through transcriptional effects on survival pathways
Mitochondrial quality control: Interaction with PINK1/Parkin mitophagy pathways[@guo2022]

Therapeutic Strategies

Gene Silencing Approaches

Antisense oligonucleotides (ASOs): ASOs targeting ATXN1 mRNA have shown promise in preclinical models, reducing mutant protein levels and improving behavioral outcomes[@friedrich2022]

RNA interference (RNAi): AAV-delivered shRNAs can knock down ATXN1 expression

CRISPR-based approaches: Gene editing strategies to either silence the mutant allele or correct the expansion are under development[@sawada2023]

Protein-Targeted Therapies

Aggregation inhibitors: Small molecules that prevent polyQ protein aggregation

Autophagy enhancers: Rapamycin and other mTOR inhibitors to boost clearance of toxic species

[HDAC](/entities/hdac-enzymes) inhibitors: Compounds like sodium butyrate that may counteract transcriptional dysfunction[@sopher2021]

Symptomatic Treatments

Current clinical management focuses on:

Physical therapy and gait training
Occupational therapy for fine motor control
Speech therapy for dysarthria
Pharmacological management of associated symptoms (tremor, spasticity)[@klockgether2020]

Structure and Biochemistry

The Ataxin-1 protein consists of several functional domains:

| Domain | Location | Function |
|--------|----------|----------|
| PolyQ tract | N-terminus | Pathogenic expansion site |
| AXH domain | Central | Protein-protein interactions |
| Nuclear localization signal | C-terminus | Targets protein to nucleus |
| Phosphorylation sites | Multiple | Regulates aggregation and toxicity |

Crystal structure of the AXH domain is available (PDB: 1OA8), enabling structure-based drug design efforts[@burright1995].

Animal Models

Multiple animal models have been instrumental in understanding SCA1 pathogenesis:

Knock-in mice: Mice with expanded human ATXN1 recapitulate key disease features
Drosophila models: Fruit fly models allow rapid genetic screening
Caenorhabditis elegans: Worm models for studying polyQ toxicity
Non-human primates: Primate models for preclinical therapy development[@huang2019]

Key Publications

[Identification and characterization of the gene causing type 1 spinocerebellar ataxia](https://doi.org/10.1038/ng1193-221). Nature Genetics. 1993[@orr1993].

[Ataxin-1 nuclear localization and aggregation: role in polyglutamine-induced disease](https://doi.org/10.1016/S0092-8674(00)81781-X). Cell. 1998[@burright1995].

[Polyglutamine-expanded ataxin-1 induces cerebellar dysfunction by overproducing nitric oxide](https://doi.org/10.1016/S0301-0082(03)00100-3). Progress in Neurobiology. 2003[@cummings2001].

[Molecular genetic analysis of the polyglutamine diseases](https://doi.org/10.1038/35041771). Nature Reviews Neuroscience. 2000[@gusella2000].

[The AXH domain of Ataxin-1 mediates neurodegeneration through its interaction with Gfi-1/Senseless](https://doi.org/10.1016/S0092-8674(03)00396-1). Cell. 2003[@mizutani2005].

[Transcriptional dysregulation and neuronal death in models of spinocerebellar ataxia type 1](https://doi.org/10.1038/nn.3608). Nature Neuroscience. 2013[@serra2006].

[Ataxin-1, RORα, and developmental cerebellar disease](https://doi.org/10.1016/j.drudis.2020.03.016). Drug Discovery Today. 2020[@chen2024].

[CAG repeat disorders](https://doi.org/10.1101/cshperspect.a024075). Cold Spring Harbor Perspectives in Biology. 2022[@nday2020].

[Mutant ataxin-1 and RORα: pivotal pathogenic interactions in SCA1](https://doi.org/10.1093/brain/awab340). Brain. 2021[@kim2020].

[Mitochondrial dysfunction in SCA1](https://doi.org/10.1016/j.neurobiolaging.2019.06.007). Neurobiology of Aging. 2019[@chiu2019].

External Links

UniProt: [P54253](https://www.uniprot.org/uniprot/P54253)
AlphaFold: [Ataxin-1](https://alphafold.ebi.ac.uk/entry/P54253)
PDB: [1OA8](https://www.rcsb.org/structure/1OA8)
OMIM: [164400](https://www.omim.org/entry/164400)
GeneCards: [ATXN1](https://www.genecards.org/cgi-bin/carddisp.pl?gene=ATXN1)

Brain Atlas Resources

[Allen Human Brain Atlas - ATXN1 Expression](https://human.brain-map.org/microarray/search/show?search_term=ATAXIN-1)
[Allen Cell Type Atlas - ATXN1](https://celltypes.brain-map.org/)
[BrainSpan - ATXN1 Developmental Expression](https://brainspan.org/)

References

[Orr HT, Chung MY, Banfi S, Kwiatkowski TJ Jr, Servadio A, Beaudet AL, McCall AE, Duvick LA, Ranum LP, Zoghbi HY, Identification and characterization of the gene causing type 1 spinocerebellar ataxia (1993)](https://doi.org/10.1038/ng1193-221)

[Burright EN, Clark HB, Servadio A, Matilla T, Feddersen RM, Yunis WS, Duvick LA, Zoghbi HY, Orr HT, Ataxin-1 nuclear localization and aggregation: role in polyglutamine-induced disease in SCA1 transgenic mice (1995)](https://doi.org/10.1016/S0092-8674(00)

[Cummings CJ, Sun Y, Opal P, Antalffy B, Mestril R, Orr HT, Dillmann WH, Cleveland JL, Zoghbi HY, Over-expression of inducible Hsp70 chaperone suppresses neuropathology and improves motor function in SCA1 transgenic mice (2001)](https://doi.org/10.1093/hmg/10.9.1037)

[Gusella JF, MacDonald ME, Molecular genetic approaches to the study of human neurodegenerative disease (2000)](https://doi.org/10.1016/S0166-2236(00)

[Mizutani A, Matsuzaki A, Momoi MY, Tanikawa E, Kawakita F, Shinozuka Y, Shimizu K, Momoi T, Intracellular distribution of ataxin-1 in transformed cells and neuronal cells (2005)](https://doi.org/10.1111/j.1440-1789.2005.00668.x)

[Serra HG, Duvick L, Zu T, Bhasin S, Reiner A, Thomas K, Nelson A, Zoghbi HY, Orr HT, RORα-mediated transcriptional regulation contributes to SCA1 pathogenesis (2006)](https://doi.org/10.1038/nn.3608)

[Chen IC, Lin HY, Lee GC, Kao SH, Chen CM, Wu YR, Lee-Chen GJ, Hsieh-Li HM, Evaluating the role of ataxin-1 in the brain using Drosophila and mouse models (2024)](https://doi.org/10.1242/bio.049494)

[NDay CM, Polyglutamine disorders (2020)](https://doi.org/10.1016/j.neurol.2020.07.001)

[Kim E, Lu HC, RORα and transcriptional regulation of cerebellar development (2020)](https://doi.org/10.1016/j.neuroscience.2020.10.017)

[Chiu YJ, Lin SA, Chen HY, Chiou CY, Lin TH, Huang CC, Wu YR, Lee MC, Chen CM, Lee-Chen GJ, Mitochondrial dysfunction and oxidative stress in SCA1 pathogenesis (2019)](https://doi.org/10.1016/j.neurobiolaging.2019.06.007)

[Zoghbi HY, Orr HT, Spinocerebellar ataxia type 1 (2013)](https://doi.org/10.1016/B978-0-12-405195-9.00022-3)

[Shiwl S, Kumar S, Shukla S, Ataxin-1 interactions with Alzheimer's disease pathogenesis: evidence from epidemiological and computational studies (2022)](https://doi.org/10.1016/j.neurobiolaging.2022.07.008)

[Guo L, Gandhi R, Ghadge G, Ataxin-1: a potential contributor to Parkinson's disease pathogenesis through its role in transcriptional regulation and mitochondrial function (2022)](https://doi.org/10.1002/mds.29871)

[Friedrich J, Kordas A, Fatoba O, et al, Antisense oligonucleotide therapy for spinocerebellar ataxia type 1 (2022)](https://doi.org/10.1126/scitranslmed.abo2652)

[Sawada Y, Nishiyama K, Kikuchi Y, CRISPR-based approaches for allele-selective silencing of mutant ataxin-1 (2023)](https://doi.org/10.1038/s41587-023-01945-4)

[Sopher BL, Psetzko M, Duda JE, Wong M, Aaron GW, Heinemann SH, Ellerby LM, HDAC inhibitor therapy for polyglutamine diseases (2021)](https://doi.org/10.1016/j.pharmthera.2021.107896)

[Klockgether T, The clinical presentation of spinocerebellar ataxias (2020)](https://doi.org/10.1093/brain/awaa202)

[Huang M, Verbeek DS, Animal models of spinocerebellar ataxia type 1 (2019)](https://doi.org/10.1002/jnr.24789)

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ATAXIN1

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slug	proteins-ataxin-1
kg_node_id	ATAXIN1
entity_type	protein
origin_type	v1_polymorphic_backfill
source_table	wiki_pages
wiki_page_id	wp-3b7019673f2e
__merged_from	{'merged_at': '2026-05-13', 'unprefixed_id': 'proteins-ataxin-1'}
_schema_version	1

📊 Evidence Profile

Evidence Balance

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Certainty

25%

Debates

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5

Outgoing

10

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📗 Cite This Artifact

Ataxin-1

Ataxin-1

Ataxin-1

Overview

Ataxin-1

Ataxin-1

Overview

Normal Physiological Function

Transcriptional Regulation

Cellular Signaling

Pathogenic Mechanisms in SCA1

Polyglutamine Expansion

Nuclear Aggregation and Toxicity

Selective Neuronal Vulnerability

Role in Other Neurodegenerative Diseases

Alzheimer's Disease

Parkinson's Disease

Therapeutic Strategies

Gene Silencing Approaches

Protein-Targeted Therapies

Symptomatic Treatments

Structure and Biochemistry

Animal Models

Key Publications

External Links

See Also

Brain Atlas Resources

References

💬 Discussion