Pathogenic and non-pathogenic polyglutamine tracts have similar structural properties: towards a length-dependent...

Area of Science:

• Neuroscience
• Molecular Biology
• Biochemistry

Background:

• Expanded polyglutamine (polyQ) tracts cause toxic gain-of-function in proteins, leading to neurodegenerative diseases.
• A hypothesized structural transition above a specific polyQ length threshold was thought to explain length-dependent toxicity.

Purpose of the Study:

• To investigate the structural properties of polyQ tracts with pathogenic and non-pathogenic lengths.
• To determine if a structural transition explains the observed polyQ length-dependent toxicity threshold.

Main Methods:

• Utilized a combination of biochemical and biophysical approaches.
• Compared structural properties of polyQ tracts in soluble, interacting, aggregating, and aggregated states.

Main Results:

• Pathogenic and non-pathogenic polyQ tracts exhibit similar structural properties across various conditions.
• PolyQ length primarily affects aggregation kinetics and aggregate stability, not structure.

Conclusions:

• PolyQ toxicity is not dependent on a specific structural transition above a threshold.
• PolyQ tracts are inherently toxic sequences, with toxicity increasing gradually with length.
• Apparent length-dependent toxicity thresholds may be explained by polyQ properties and cellular factors.