FUS and TDP-43 aggregation are uncoupled from toxicity in ageing yeast models.

<h4>Background</h4>Protein aggregation is indicative of the loss of proteostasis(definition) associated with neurodegenerative diseases, including Amyotrophic Lateral Sclerosis (ALS) and Frontotemporal Dementia (FTD). Proteins like Fused in sarcoma (FUS) and Tar DNA-binding protein 43 (TDP-43) accumulate and aggregate in the cytosol of neurons in ALS/FTD. Yet, it remains unclear how ageing affects FUS and TDP-43 aggregation, and how these aggregates in turn influence neurodegeneration in ALS/FTD. In addition, mistranslation can reduce longevity, challenge proteostasis, and modulate protein aggregation. To investigate how ageing and mistranslation modulate FUS and TDP-43 aggregation and toxicity, we enlist tractable and reliable yeast models.<h4>Results</h4>Using optimized low-expression FUS and TDP-43 yeast models, we demonstrate that chronological ageing antagonizes proteostasis, the steady state levels and solubility of molecular chaperones, and aggregation of FUS and TDP-43. In addition, mistranslation caused by tRNA variants further antagonize FUS and TDP-43 aggregation and synergize to exacerbate FUS and TDP-43 cytotoxicity.<h4>Conclusions</h4>Our work provides new insights into factors that uncouple FUS and TDP-43 aggregation from toxicity and support a rather protective role for FUS and TDP-43 aggregates in promoting longevity.