Protein thiol alterations drive pathologic liquid-liquid phase separation in the aging brain.

Cellular homeostasis relies on regulation of processes, including protein post-translational modifications (PTMs) and biomolecular condensation. Aging disrupts the equilibrium of these processes, increasing susceptibility to disease and mortality. Here we used chemoproteomic techniques to generate an atlas of cysteine PTMs in the mouse brain and showed that age-related increases in thiol oxidation promoted the formation of biomolecular condensates. By contrast, protein persulfidation, regulated by hydrogen sulfide production, inhibited biomolecular condensation, preserving protein function. Age-induced alterations in cysteine PTMs influenced the phase separation properties of synapsin 1 and G3BP2, leading to impaired neurotransmitter release and defective stress granule formation and resolution, features associated with aging and neurodegenerative diseases. Mice deficient in cystathionine γ-lyase, the enzyme responsible for hydrogen sulfide production, exhibited reduced lifespans and spontaneously developed protein aggregates with age. Our results highlight the therapeutic potential of protein persulfidation in reversal of dysregulated biomolecular condensation and suggest that sulfide donors could be used to mitigate age-related diseases.