Electrostatic modulation of hnRNPA1 low-complexity domain liquid-liquid phase separation and aggregation

Area of Science:

• Biochemistry
• Molecular Biology
• Neuroscience

Background:

• Membrane-less organelles and RNP granules are rich in RNA and RNA-binding proteins with disordered regions.
• Heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1) is crucial for RNA metabolism and localizes to cytoplasmic RNP granules.
• hnRNPA1 dysfunction, including altered phase separation, is linked to neurodegeneration via abnormal amyloid aggregation.

Purpose of the Study:

• To investigate the mechanisms of protein phase separation and aggregation.
• To study the liquid-liquid phase separation (LLPS) of hnRNPA1 C-terminal domain (CTD).
• To explore how environmental factors like pH, salt, and RNA concentration influence hnRNPA1 LLPS and aggregation.

Main Methods:

• Studied LLPS of hnRNPA1 CTD under varying pH, protein, salt, and RNA concentrations.
• Probed the role of protein electrostatics in phase separation and aggregation.
• Observed conditions favoring LLPS and their impact on protein aggregation and fibrillation.

Main Results:

• LLPS of hnRNPA1 CTD was favored in acidic conditions.
• High protein, salt, and RNA concentrations promoted LLPS.
• Conditions that enhanced LLPS also increased protein aggregation and fibrillation, indicating an LLPS-mediated aggregation pathway.

Conclusions:

• LLPS plays a direct role in facilitating protein aggregation.
• Changes in cellular environment, particularly protein electrostatics, can contribute to pathological aggregation in neurodegeneration.
• Understanding LLPS mechanisms is key to addressing neurodegenerative diseases linked to hnRNPA1 aggregation.