Intra-condensate demixing of TDP-43 inside stress granules generates pathological aggregates
Xiao Yan, David Kuster, Priyesh Mohanty, Jik Nijssen, Karina Pombo‐García, Jorge García Morato, Azamat Rizuan, Titus M. Franzmann, Aleksandra Sergeeva, Anh Ly, Feilin Liu, Patricia M. dos Passos, Leah George, Szu‐Huan Wang, Jayakrishna Shenoy, Helen L. Danielson, Busra Ozguney, Alf Honigmann, Yuna M. Ayala, Nicolas L. Fawzi, Dennis W. Dickson, Wilfried Rossoll, Jeetain Mittal, Simon Alberti, Anthony A. Hyman
Abstract
Cytosolic aggregation of the nuclear protein TAR DNA-binding protein 43 (TDP-43) is associated with many neurodegenerative diseases, but the triggers for TDP-43 aggregation are still debated. Here, we demonstrate that TDP-43 aggregation requires a double event. One is up-concentration in stress granules beyond a threshold, and the other is oxidative stress. These two events collectively induce intra-condensate demixing, giving rise to a dynamic TDP-43-enriched phase within stress granules, which subsequently transition into pathological aggregates. Intra-condensate demixing of TDP-43 is observed in iPS-motor neurons, a disease mouse model, and patient samples. Mechanistically, intra-condensate demixing is triggered by local unfolding of the RRM1 domain for intermolecular disulfide bond formation and by increased hydrophobic patch interactions in the C-terminal domain. By engineering TDP-43 variants resistant to intra-condensate demixing, we successfully eliminate pathological TDP-43 aggregates in cells. We suggest that up-concentration inside condensates followed by intra-condensate demixing could be a general pathway for protein aggregation.