Disease-associated mutations affect TIA1 phase separation and aggregation in a proline-dependent manner

Area of Science:

• Biochemistry
• Molecular Biology
• Neuroscience

Background:

• T-cell restriction intracellular antigen 1 (TIA1) is an RNA-binding protein crucial for stress granule (SG) formation.
• The low complexity domain (LCD) of TIA1 drives SG assembly via liquid-liquid phase separation (LLPS).
• Dysregulation of LLPS is implicated in various diseases, and proline-rich domains can influence this process.

Purpose of the Study:

• To investigate the role of proline residues in TIA1's LLPS and SG dynamics.
• To examine the impact of disease-associated proline mutations on TIA1 phase separation and cellular behavior.
• To elucidate the link between altered TIA1 LLPS and the pathogenesis of amyotrophic lateral sclerosis (ALS).

Main Methods:

• In-cell phase separation assays to observe TIA1 behavior.
• Analysis of proline-to-leucine (P-L) mutations' effects on TIA1 droplet morphology.
• Assessment of TIA1 in vivo behavior and stress granule kinetics.
• Investigation of pathological inclusion formation in relation to TIA1 mutation.

Main Results:

• TIA1 undergoes phase separation within cells.
• Disease-associated P-L mutations alter TIA1 droplet morphology and promote a liquid-to-solid phase transition into amyloid fibrils.
• These mutations disrupt normal SG kinetics and lead to the formation of pathological inclusions characteristic of ALS.
• Proline residues are identified as critical regulators of TIA1 LLPS.

Conclusions:

• Proline residues are essential for regulating TIA1's liquid-liquid phase separation (LLPS) and stress granule (SG) formation.
• Mutations affecting proline residues disrupt TIA1 LLPS, promoting aggregation into amyloid fibrils and contributing to ALS pathogenesis.
• This study highlights proline's critical role in TIA1 function and its implications for neurodegenerative diseases like ALS.