Huntingtin (HTT) Protein
<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">Huntingtin (HTT)</th>
</tr>
<tr>
<td class="label">Gene</td>
<td>[HTT](/genes/htt)</td>
</tr>
<tr>
<td class="label">UniProt</td>
<td><a href="https://www.uniprot.org/uniprot/P42857" target="_blank">P42857</a></td>
</tr>
<tr>
<td class="label">PDB</td>
<td><a href="https://www.rcsb.org/structure/3IO4" target="_blank">3IO4</a>, <a href="https://www.rcsb.org/structure/6ZFR" target="_blank">6ZFR</a></td>
</tr>
<tr>
<td class="label">Mol. Weight</td>
<td>~350 kDa (full-length)</td>
</tr>
<tr>
<td class="label">Localization</td>
<td>Cytoplasm, nucleus, synapses</td>
</tr>
<tr>
<td class="label">Family</td>
<td>[Huntingtin protein](/proteins/huntingtin) family</td>
</tr>
<tr>
<td class="label">Diseases</td>
<td>[Huntington's Disease](/diseases/huntingtons)</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">ALS</a>, <a href="/wiki/alzheimer's-disease" style="color:#ef9a9a">ALZHEIMER'S DISEASE</a>, <a href="/wiki/aging" style="color:#ef9a9a">Aging</a>, <a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/alzheimer" style="color:#ef9a9a">Alzheimer</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">243 edges</a></td>
</tr>
</table>
Huntingtin (HTT)
Introduction
...Huntingtin (HTT) Protein
<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">Huntingtin (HTT)</th>
</tr>
<tr>
<td class="label">Gene</td>
<td>[HTT](/genes/htt)</td>
</tr>
<tr>
<td class="label">UniProt</td>
<td><a href="https://www.uniprot.org/uniprot/P42857" target="_blank">P42857</a></td>
</tr>
<tr>
<td class="label">PDB</td>
<td><a href="https://www.rcsb.org/structure/3IO4" target="_blank">3IO4</a>, <a href="https://www.rcsb.org/structure/6ZFR" target="_blank">6ZFR</a></td>
</tr>
<tr>
<td class="label">Mol. Weight</td>
<td>~350 kDa (full-length)</td>
</tr>
<tr>
<td class="label">Localization</td>
<td>Cytoplasm, nucleus, synapses</td>
</tr>
<tr>
<td class="label">Family</td>
<td>[Huntingtin protein](/proteins/huntingtin) family</td>
</tr>
<tr>
<td class="label">Diseases</td>
<td>[Huntington's Disease](/diseases/huntingtons)</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">ALS</a>, <a href="/wiki/alzheimer's-disease" style="color:#ef9a9a">ALZHEIMER'S DISEASE</a>, <a href="/wiki/aging" style="color:#ef9a9a">Aging</a>, <a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/alzheimer" style="color:#ef9a9a">Alzheimer</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">243 edges</a></td>
</tr>
</table>
Huntingtin (HTT)
Introduction
Huntingtin (Htt) Protein is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
Overview
Huntingtin (HTT) is a massive 3,144-amino acid protein encoded by the HTT gene that is central to the pathogenesis of Huntington's disease (HD), an autosomal dominant neurodegenerative disorder[@huntingtons1993]. Wild-type huntingtin is essential for normal neuronal function, while mutant huntingtin with expanded polyglutamine (polyQ) tracts becomes toxic and leads to progressive neurodegeneration in the striatum and [cortex](/brain-regions/cortex)[@macdonald1993].
Huntingtin is one of the largest proteins in the human proteome and participates in numerous cellular functions including vesicle trafficking, transcription regulation, mitochondrial dynamics, and synaptic transmission. The discovery that CAG repeat expansion in HTT causes HD has made this protein a major therapeutic target[@gusella2006].
Structure
Huntingtin is a modular protein with multiple functional domains:
N-Terminal Region (residues 1-100)
Contains the polyglutamine (polyQ) tract whose length determines disease onset:
- Normal: <26 CAG repeats
- Intermediate: 27-35 repeats (may expand in offspring)
- Penetrant: ≥36 repeats (causative of HD)
HEAT Repeats (throughout)
Huntingtin contains approximately 36 HEAT repeats - helical repeats that mediate protein-protein interactions. These repeats form a superhelical structure involved in binding various partner proteins.
Caspase Cleavage Sites
Multiple caspase (especially caspase-6) cleavage sites in the N-terminal region generate toxic fragments in disease states.
Nuclear Localization Signal (NLS)
Located near the C-terminus, involved in nuclear import of huntingtin fragments.
Proline-Rich Region
Located downstream of the polyQ tract, involved in protein interactions via SH3 domains.
Normal Function
Wild-type huntingtin is ubiquitously expressed and essential for development. Key normal functions include:
Vesicle Trafficking
- Participates in clathrin-mediated endocytosis
- Regulates synaptic vesicle recycling
- Facilitates axonal transport via interaction with kinesin and dynein
Transcription Regulation
- Interacts with transcription factors including p53, [NF-κB](/entities/nf-kb), and SP1
- Regulates brain-derived neurotrophic factor (BDNF) expression
- Controls neuronal gene expression programs
Mitochondrial Function
- Maintains mitochondrial morphology and distribution
- Regulates mitochondrial fission and fusion
- Protects against mitochondrial dysfunction
Cell Survival
- Antiapoptotic function via interaction with HAP40
- [Autophagy](/entities/autophagy) regulation
- Proteasomal degradation regulation
Synaptic Function
- Presynaptic and postsynaptic localization
- Regulates neurotransmitter release
- Controls dendritic spine morphology
Role in Disease
Huntington's Disease Pathogenesis
Mutant huntingtin (mHTT) with expanded polyQ repeats causes HD through multiple mechanisms:
1. Toxic Gain-of-Function
- Abnormal protein folding and aggregation
- Formation of soluble oligomers and insoluble aggregates
- Sequestration of essential cellular proteins
2. Transcriptional Dysregulation
- Disrupted transcription factor function
- Reduced BDNF expression
- Altered neuronal gene programs
3. Mitochondrial Dysfunction
- Impaired mitochondrial respiration
- Increased oxidative stress
- Abnormal mitochondrial dynamics
4. Synaptic Dysfunction
- Impaired vesicle trafficking
- Altered neurotransmitter release
- Dendritic spine loss
5. Autophagy Impairment
- Defective autophagosome formation
- Accumulation of damaged organelles
- Protein aggregate buildup
Selective Neuronal Vulnerability
The striatum (caudate nucleus and putamen) and cortex are most affected due to:
- High mutant huntingtin expression
- Transcriptional vulnerability
- Mitochondrial susceptibility
- Calcium signaling dysregulation
Therapeutic Targeting
Lowering Strategies
- ASOs: Nusinersen and similar ASOs targeting HTT mRNA
- RNAi: siRNA/shRNA approaches
- Small molecules: Pharmacological HTT expression modulators
Aggregation Modulators
- Esterastin: Inhibits HTT aggregation
- M相关文章: Natural compounds targeting mHTT aggregation
Gene Therapy
- CRISPR-Cas9 approaches to silence mutant HTT
- Allele-specific targeting of mutant allele
Symptomatic Treatments
- Dopamine antagonists for chorea
- [NMDA receptor](/entities/nmda-receptor) antagonists
- Neurotrophic factor delivery
Key Publications
[The Huntington's Disease Collaborative Research Project (1993)](https://doi.org/10.1016/0092-8674(93)90585-E)
[Gusella JF & MacDonald ME, Huntington's disease (2000)](https://doi.org/10.1016/S0092-8674(00)00070-2)
[Landles C & Bates GP, Huntingtin and the molecular pathogenesis of Huntington's disease (2004)](https://doi.org/10.1038/35065145)
[Trottier Y et al., Polyglutamine expansion as a pathological epitope in Huntington's disease (1995)](https://doi.org/10.1038/378398a0)
[Cattaneo E et al., Loss of normal huntingtin function (2001)](https://doi.org/10.1016/S0166-2236(01)02195-4)
[Ross CA & Tabrizi SJ, Huntington's disease: from molecular pathogenesis to clinical treatment (2011)](https://doi.org/10.1016/S1474-4422(10)70245-3)
Background
The study of Huntingtin (Htt) Protein has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
External Links
- [PubMed](https://pubmed.ncbi.nlm.nih.gov/) - Biomedical literature
- [Alzheimer's Disease Neuroimaging Initiative](https://adni.loni.usc.edu/) - Research data
- [Allen Brain Atlas](https://brain-map.org/) - Brain gene expression data
Cross-References
- [HTT Gene](/genes/htt)
- [Huntington's Disease](/diseases/huntingtons)
- [Polyglutamine Diseases](/diseases/polyglutamine-diseases)
- [Protein Aggregation Mechanisms](/mechanisms/protein-aggregation)
- [Transcription Dysregulation in Neurodegeneration](/mechanisms/transcription-dysregulation)
- [Mitochondrial Dysfunction in HD](/mechanisms/mitochondrial-dysfunction)
See Also
- [Cell Types Index](/cell-types/)
- [Proteins Index](/proteins/)
- [Genes Index](/genes/)
References
[Unknown, The Huntington's Disease Collaborative Research Project. A novel gene containing a trinucleotide repeat that is expanded and unstable on Huntington's disease chromosomes (1993)](https://doi.org/10.1016/0092-8674(93)
[MacDonald ME, Ambrose CM, Duyao MP, et al, A novel gene containing a trinucleotide repeat that is expanded and unstable on Huntington's disease chromosomes (1993)](https://doi.org/10.1016/0092-8674(93)
[Gusella JF, MacDonald ME, Huntington's disease: seeing the pathogenic process through a genetic lens (2006)](https://doi.org/10.1016/j.tibs.2006.06.009)