Ataxin-2 (ATXN2) is a cytoplasmic RNA-binding protein that regulates mRNA translation, stability, and stress granule dynamics. Intermediate-length CAG repeat expansions in ATXN2 are a major genetic risk factor for Amyotrophic Lateral Sclerosis (ALS), while longer expansions cause Spinocerebellar Ataxia Type 2 (SCA2).[1] Ataxin-2 is emerging as a critical node connecting RNA metabolism, proteostasis, and neurodegeneration.
Ataxin-2 contains:
The protein localizes to stress granules and processing bodies (P-bodies), key sites of mRNA metabolism.[2]
Ataxin-2 controls post-transcriptional gene expression:
During cellular stress, ataxin-2:
The LSm domain is essential for stress granule localization and dynamics.[3]
Long CAG expansions (>34 repeats) cause SCA2:
Intermediate-length repeats (24-34) increase ALS risk:[4]
Ataxin-2 modulates the toxicity of other ALS proteins:
The interaction between ataxin-2 and TDP-43 provides a molecular explanation for why ATXN2 expansions increase ALS risk.[5]
| Mechanism | Evidence | Consequence |
|---|---|---|
| Stress granule persistence | Mutant ATXN2 increases granule size | Impaired translation recovery |
| RNA processing defects | Altered splicing patterns | Dysregulated gene expression |
| Proteostasis overload | Inclusion formation | UPS and autophagy impairment |
| Strategy | Target | Status |
|---|---|---|
| Stress granule modulators | Reduce granule persistence | Preclinical |
| RNA-binding inhibitors | LSm domain | Discovery |
| Repeat-targeting | CAG RNA | Preclinical |
| Partner | Function | Disease Relevance |
|---|---|---|
| PABPC1 | Poly(A) binding | Translation regulation |
| TDP-43 | RNA-binding protein | ALS aggregation |
| DDX6 | RNA helicase | P-body function |
| AGO2 | miRNA machinery | Post-transcriptional regulation |
Elden AC, et al. Ataxin-2 intermediate-length polyglutamine expansions are associated with increased risk for ALS. Nature. 2010. ↩︎
Nonhoff S, et al. Ataxin-2 interacts with the DEAD/H-box RNA helicase DDX6 and interferes with P-bodies and stress granules. Molecular Biology of the Cell. 2007. ↩︎
Kaehler C, et al. Ataxin-2-like is a regulator of stress granule and dynein dynamics in neurons. Journal of Neuroscience. 2014. ↩︎
Van Damme P, et al. Expanded ATXN2 CAG repeat size in ALS identifies genetic overlap between ALS and SCA2. Brain. 2011. ↩︎
Kim HJ, et al. Mutations in prion-like domains in hnRNPA2B1 and hnRNPA1 cause multisystem proteinopathy and ALS. Nature. 2013. ↩︎