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Abstract In Tau protein condensates formed by the Liquid–Liquid Phase Separation (LLPS) process, liquid‐to‐solid transitions lead to the formation of fibrils implicated in Alzheimer's disease. Here, by tracking two contacting Tau‐rich droplets using a simple and nonintrusive video microscopy, we found that the halftime of the liquid‐to‐solid transition in the Tau condensate is affected by the Hofmeister series according to the solvation energy of anions. After dissecting functional groups of physiologically relevant small molecules using a multivariate approach, we found that charged groups facilitate the liquid‐to‐solid transition in a manner similar to the Hofmeister effect, whereas hydrophobic alkyl chains and aromatic rings inhibit the transition. Our results not only elucidate the driving force of the liquid‐to‐solid transition in Tau condensates, but also provide guidelines to design small molecules to modulate this important transition for many biological functions for the first time.
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This content will become publicly available on March 19, 2026
Decoupling Phase Separation and Fibrillization Preserves Activity of Biomolecular Condensates
Abstract Age-dependent transition of metastable, liquid-like protein condensates to amyloid fibrils is an emergent phenomenon of numerous neurodegeneration-linked protein systems. A key question is whether the thermodynamic forces underlying reversible phase separation and maturation to irreversible amyloids are distinct and separable. Here, we address this question using an engineered version of the microtubule-associated protein Tau, which forms biochemically active condensates. Liquid-like Tau condensates exhibit rapid aging to amyloid fibrils under quiescent, cofactor-free conditions. Tau condensate interface promotes fibril nucleation, impairing their activity to recruit tubulin and catalyze microtubule assembly. Remarkably, a small molecule metabolite, L-arginine, selectively impedes condensate-to-fibril transition without perturbing phase separation in a valence and chemistry-specific manner. By heightening the fibril nucleation barrier, L-arginine counteracts age-dependent decline in the biochemical activity of Tau condensates. These results provide a proof-of-principle demonstration that small molecule metabolites can enhance the metastability of protein condensates against a liquid-to-amyloid transition, thereby preserving condensate function.
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- Award ID(s):
- 2146549
- PAR ID:
- 10608868
- Publisher / Repository:
- bioRxiv
- Date Published:
- Format(s):
- Medium: X
- Institution:
- bioRxiv
- Sponsoring Org:
- National Science Foundation
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