Related Experiment Video
Updated: Dec 21, 2025
Assay Development for High Content Quantification of Sod1 Mutant Protein Aggregate Formation in Living Cells
Published on: October 4, 2017
Exposure of a cryptic Hsp70 binding site determines the cytotoxicity of the ALS-associated SOD1-mutant A4V
Filip Claes1,2, Stanislav Rudyak1,2,3, Angela S Laird4,5
1VIB Center for Brain & Disease Research, Switch Laboratory, Herestraat 49, Leuven, Belgium.
Abstract:
The accumulation of toxic protein aggregates is thought to play a key role in a range of degenerative pathologies, but it remains unclear why aggregation of polypeptides into non-native assemblies is toxic and why cellular clearance pathways offer ineffective protection. We here study the A4V mutant of SOD1, which forms toxic aggregates in motor neurons of patients with familial amyotrophic lateral sclerosis (ALS). A comparison of the location of aggregation prone regions (APRs) and Hsp70 binding sites in the denatured state of SOD1 reveals that ALS-associated mutations promote exposure of the APRs more than the strongest Hsc/Hsp70 binding site that we could detect. Mutations designed to increase the exposure of this Hsp70 interaction site in the denatured state promote aggregation but also display an increased interaction with Hsp70 chaperones. Depending on the cell type, in vitro this resulted in cellular inclusion body formation or increased clearance, accompanied with a suppression of cytotoxicity. The latter was also observed in a zebrafish model in vivo. Our results suggest that the uncontrolled accumulation of toxic SOD1A4V aggregates results from insufficient detection by the cellular surveillance network.
Insights
Toxic protein aggregate accumulation in neurodegenerative diseases like ALS is poorly understood. This study shows that enhancing cellular chaperone interactions with SOD1 aggregates can reduce toxicity and improve clearance, suggesting a target for therapeutic intervention.
Area of Science:
- Neuroscience
- Molecular Biology
- Protein Biochemistry
Background:
- Toxic protein aggregates are implicated in neurodegenerative diseases.
- Familial amyotrophic lateral sclerosis (ALS) involves SOD1 protein aggregation.
- Cellular mechanisms for clearing misfolded proteins are not fully understood.
Purpose of the Study:
- Investigate why SOD1 aggregation is toxic in ALS.
- Determine the role of cellular clearance pathways in SOD1 aggregation.
- Explore strategies to enhance cellular protection against toxic protein aggregates.
Main Methods:
- Studied the A4V mutant of SOD1, linked to familial ALS.
- Compared aggregation-prone regions (APRs) with Hsp70 binding sites in denatured SOD1.
- Engineered SOD1 mutations to enhance Hsp70 interaction.
- Assessed aggregation, clearance, and cytotoxicity in vitro and in a zebrafish model.
Main Results:
- ALS-associated SOD1 mutations expose aggregation-prone regions more than Hsp70 binding sites.
- Mutations increasing Hsp70 interaction sites promoted aggregation but enhanced chaperone binding.
- In vitro, this led to inclusion body formation or increased clearance and reduced cytotoxicity.
- In vivo, enhanced clearance and suppressed cytotoxicity were observed in a zebrafish ALS model.
Conclusions:
- Insufficient detection by cellular surveillance networks contributes to toxic SOD1 aggregate accumulation.
- Enhancing Hsp70 chaperone interaction with SOD1 aggregates can mitigate cytotoxicity.
- Targeting cellular clearance pathways offers a potential therapeutic strategy for ALS and other proteinopathies.
