Nucleoporin 50 rescues hallmarks of TDP-43 proteinopathy in ALS/FTD disease models

Abstract

Abstract Nuclear depletion and cytoplasmic aggregation of RNA-binding protein TDP-43 are common neuropathological hallmarks of the amyotrophic lateral sclerosis and frontotemporal degeneration (ALS/FTD) disease spectrum. Although defects in nucleocytoplasmic transport are well-documented in ALS/FTD disease models and patient tissue, and nuclear transport receptors have been shown to modulate TDP-43 pathology, the role of nucleoporins in TDP-43 mislocalization and cytoplasmic aggregation is not well understood. Here, we show that nucleoporin 50 (NUP50), which has been genetically linked to ALS risk, acts as a protective modifier of TDP-43 pathology in cellular models of ALS/FTD. NUP50 expression reduces detergent-insoluble TDP-43, visible TDP-43 aggregation, and pathological TDP-43 hyperphosphorylation. We show that its activity against TDP-43 aggregation depends on association with the nuclear pore complex (NPC) and identify a 41-amino-acid NUP50 fragment that is sufficient for both NPC association and reduction of pathological TDP-43 aggregation. We demonstrate that this active fragment reduces TDP-43 aggregation and neurotoxicity in primary neurons. We also characterize an ALS-linked NUP50 missense variant with impaired activity against TDP-43 aggregation and show that NUP50 partially co-localizes with pathological TDP-43 inclusions in human ALS/FTD brain tissue. Together, our results identify NUP50 as a modifier of TDP-43 aggregation and toxicity, support a model in which reduced NUP50 activity contributes to TDP-43 proteinopathy, and highlight NUP50 activity and its minimal active fragment as promising starting points for therapeutic development aimed at reducing TDP-43 aggregation and toxicity.