Breaking β-sheets in FUS prion-like domain preserves phase separation and function but prevents aggregation and...

Area of Science:

• Biochemistry
• Molecular Biology
• Neuroscience

Background:

• The RNA-binding protein Fused in Sarcoma (FUS) is crucial for RNA processing via phase separation.
• Aberrant aggregation of FUS, particularly its prion-like low complexity (LC) domain, into solid-like structures is implicated in neurodegenerative diseases like ALS and FTD.
• The role of β-sheet formation in FUS aggregation and its contribution to toxicity remain areas of active investigation.

Purpose of the Study:

• To investigate the role of β-sheet structures in FUS aggregation and neurotoxicity.
• To develop FUS variants that prevent pathological aggregation without compromising physiological functions.
• To explore β-sheet modulation as a therapeutic strategy for FUS-related neurodegeneration.

Main Methods:

• Introduction of β-sheet-breaking proline residues into the FUS LC domain.
• Assessment of structural integrity, protein dynamics, and phase separation behavior of engineered FUS variants.
• Evaluation of FUS cellular localization, regulatory functions, and aggregation propensity.
• Testing the efficacy of β-sheet-deficient FUS variants in Drosophila models of neurodegeneration.

Main Results:

• Engineered FUS variants with proline insertions maintained native-like global motions, disorder, and phase separation properties.
• These variants failed to undergo the liquid-to-solid transition (LST) associated with aggregation.
• Biochemical partitioning, cellular localization, and FUS regulatory functions remained largely unchanged.
• FUS-induced neurodegeneration in Drosophila models was significantly reduced by the β-sheet-deficient FUS variants.

Conclusions:

• β-sheets are key drivers of FUS condensate maturation and subsequent neuronal toxicity.
• Modulating backbone structure to prevent β-sheet formation is a viable strategy to mitigate FUS-related neurodegeneration.
• Targeted proline additions offer a therapeutic entry point for treating pathologies associated with prion-like domain protein aggregation.