ATP as a Key Modulator of Fused-in-sarcoma Phase Separation and Aggregation: Insights into Amyotrophic Lateral...

Area of Science:

• Biochemistry
• Neuroscience
• Molecular Biology

Background:

• Fused in sarcoma (FUS) is an RNA-binding protein implicated in amyotrophic lateral sclerosis (ALS) pathogenesis.
• Aberrant liquid-liquid phase separation (LLPS) and aggregation of FUS are linked to ALS.
• The role of adenosine triphosphate (ATP), a cellular hydrotrope, in modulating FUS LLPS and aggregation is not fully understood.

Purpose of the Study:

• To investigate how ATP influences the LLPS behavior and aggregation of wild-type FUS and its ALS-linked variants.
• To elucidate the molecular mechanisms by which ATP modulates FUS aggregation.
• To assess the potential of ATP as a therapeutic agent for ALS.

Main Methods:

• In vitro assays to study FUS LLPS and aggregation.
• Pressure-jump experiments to assess aggregation propensity.
• Molecular dynamic simulations to reveal molecular interactions.
• Investigation of FUS variants R495X and P525L.

Main Results:

• ATP destabilized both normal and high-pressure LLPS (HP-LLPS) of FUS, with a stronger inhibitory effect on HP-LLPS.
• ATP reduced the irreversible aggregation of FUS, particularly in ALS variants.
• Molecular dynamics simulations showed ATP's triphosphate and adenosine moieties disrupt intermolecular interactions essential for phase separation.
• Physiological ATP concentrations (1-12 mM) significantly inhibited FUS aggregation.

Conclusions:

• Decreased intracellular ATP levels may promote aberrant FUS phase transitions and contribute to ALS.
• ATP acts as a protective agent by inhibiting FUS aggregation.
• ATP holds potential as a therapeutic modulator for protein phase separation and aggregation in neurodegenerative disorders like ALS.