The effect of G-quadruplexes on TDP43 condensation, distribution, and toxicity

Many proteins implicated in neurodegenerative diseases (e.g., trans-active response DNA binding protein 43 kDa [TDP43]) interact with nucleic acids, including RNA G-quadruplexes (G4s). We here investigate whether RNA G4s play a role in TDP43 condensation in biophysical and cellular models. We find that G4s modulate TDP43 aggregation in vitro and condensation in multiple cell types, including yeast, HEK293T, and motor-neuron-like NSC-34 cells. In yeast cells, treatment with G4s causes increased TDP43 accumulation in cells before cellular death. In HEK293T cells expressing TDP43, incubation with G4-binding small molecules causes an increase in G4 stability that also stabilizes TDP43 and reduces TDP43 condensation induced by proteasomal or oxidative stress. Finally, in NSC-34 cells overexpressing exogenous TDP43, we show that G4s co-localize with TDP43 condensates under stress conditions, and treatment with G4-binding small molecules decreases TDP43-mediated toxicity. Together, these findings suggest exploring treating protein misfolding diseases by targeting specific RNA structures such as G4s.