Prion-like C-Terminal Domain of TDP-43 and α-Synuclein Interact Synergistically to Generate Neurotoxic Hybrid Fibrils

Aberrant aggregation and amyloid formation of tar DNA binding protein (TDP-43) and alpha-synuclein (alpha S) underlie frontotemporal dementia (FTD) and Parkinson's disease (PD), respectively. Amyloid inclusions of TDP-43 and alpha S are also commonly co-observed in amyotrophic lateral sclerosis (ALS), dementia with Lewy bodies (DLB) and Alzheimer disease (AD). Emerging evidence from cellular and animal models show colocalization of the TDP-43 and alpha S aggregates, raising the possibility of direct interactions and co-aggregation between the two proteins. In this report, we set out to answer this question by investigating the interactions between alpha S and prion-like pathogenic C-terminal domain of TDP-43 (TDP-43 PrLD). PrLD is an aggregation-prone fragment generated both by alternative splicing as well as aberrant proteolytic cleavage of full length TDP-43. Our results indicate that two proteins interact in a synergistic manner to augment each other's aggregation towards hybrid fibrils. While monomers, oligomers and sonicated fibrils of alpha S seed TDP-43 PrLD monomers, TDP-43 PrLD fibrils failed to seed alpha S monomers indicating selectivity in interactions. Furthermore, alpha S modulates liquid droplets formed by TDP-43 PrLD and RNA to promote insoluble amyloid aggregates. Importantly, the cross-seeded hybrid aggregates show greater cytotoxicity as compared to the individual homotypic aggregates suggesting that the interactions between the two proteins have a discernable impact on cellular functions. Together, these results bring forth insights into TDP-43 PrLD - alpha S interactions that could help explain clinical and pathological presentations in patients with co-morbidities involving the two proteins. Published by Elsevier Ltd.

Automated summary

Aberrant aggregation and amyloid formation of TDP-43 and alpha S underlie FTD and PD respectively. Interaction between these proteins can lead to hybrid fibrils with greater cytotoxicity, impacting cellular functions.