Loss of TDP-43 oligomerization or RNA binding elicits distinct aggregation patterns

EMBO J. 2023 Sep 4;42(17):e111719. doi: 10.15252/embj.2022111719. Epub 2023 Jul 11.

Abstract

Aggregation of the RNA-binding protein TAR DNA-binding protein 43 (TDP-43) is the key neuropathological feature of neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). In physiological conditions, TDP-43 is predominantly nuclear, forms oligomers, and is contained in biomolecular condensates assembled by liquid-liquid phase separation (LLPS). In disease, TDP-43 forms cytoplasmic or intranuclear inclusions. How TDP-43 transitions from physiological to pathological states remains poorly understood. Using a variety of cellular systems to express structure-based TDP-43 variants, including human neurons and cell lines with near-physiological expression levels, we show that oligomerization and RNA binding govern TDP-43 stability, splicing functionality, LLPS, and subcellular localization. Importantly, our data reveal that TDP-43 oligomerization is modulated by RNA binding. By mimicking the impaired proteasomal activity observed in ALS/FTLD patients, we found that monomeric TDP-43 forms inclusions in the cytoplasm, whereas its RNA binding-deficient counterpart aggregated in the nucleus. These differentially localized aggregates emerged via distinct pathways: LLPS-driven aggregation in the nucleus and aggresome-dependent inclusion formation in the cytoplasm. Therefore, our work unravels the origins of heterogeneous pathological species reminiscent of those occurring in TDP-43 proteinopathy patients.

Keywords: LLPS; RNA; TDP-43; aggregation; oligomerization.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amyotrophic Lateral Sclerosis* / metabolism
  • DNA-Binding Proteins / metabolism
  • Frontotemporal Lobar Degeneration* / metabolism
  • Humans
  • Neurons / metabolism
  • RNA / genetics

Substances

  • DNA-Binding Proteins
  • RNA