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

The events that lead to protein misfolding diseases are not fully understood. Many proteins implicated in neurodegenerative diseases (e.g., TDP43) interact with nucleic acids, including RNA G-quadruplexes. In this work, we investigate whether RNA G-quadruplexes play a role in TDP43 condensation in biophysical and cellular models. We find that G-quadruplexes 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 G-quadruplexes causes increased TDP43 accumulation in cells before cellular death. In HEK293T cells expressing TDP43, incubation with G-quadruplex-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 G-quadruplexes co-localize with TDP43 condensates under stress conditions and treatment with G-quadruplex-binding small molecules decreases TDP43-mediated toxicity. Together, these findings suggest that a novel future approach to explore for treating protein misfolding diseases may be to target specific RNA structures such as G-quadruplexes.