1 research outputs found
Detection of TAR DNA-binding protein 43 (TDP-43) oligomers as initial intermediate species during aggregate formation
Aggregates of the RNA-binding protein TDP-43 (TAR DNAbinding protein) are a hallmark of the overlapping neurodegenerative disorders amyotrophic lateral sclerosis (ALS) and
frontotemporal dementia. The process of TDP-43 aggregation
remains poorly understood, and whether it includes formation
of intermediate complexes is unknown. Here, we analyzed
aggregates derived from purified TDP-43 under semidenaturing conditions, identifying distinct oligomeric complexes at the
initial time points before the formation of large aggregates. We
found that this early oligomerization stage is primarily driven by
TDP-43’s RNA-binding region. Specific binding to GU-rich
RNA strongly inhibited both TDP-43 oligomerization and
aggregation, suggesting that RNA interactions are critical for
maintaining TDP-43 solubility. Moreover, we analyzed TDP-43
liquid–liquid phase separation and detected similar detergentresistant oligomers upon maturation of liquid droplets into solid-like fibrils. These results strongly suggest that the oligomers
form during the early steps of TDP-43 misfolding. Importantly,
the ALS-linked TDP-43 mutations A315T and M337V significantly accelerate aggregation, rapidly decreasing the monomeric
population and shortening the oligomeric phase. We also show
that aggregates generated from purified TDP-43 seed intracellular
aggregation detected by established TDP-43 pathology markers.
Remarkably, cytoplasmic aggregate seeding was detected earlier
for the A315T and M337V variants and was 50% more widespread
than forWTTDP-43 aggregates.We provide evidence for aninitial
step of TDP-43 self-assembly into intermediate oligomeric complexes, whereby these complexes may provide a scaffold for aggregation. This process is altered by ALS-linked mutations, underscoring the role of perturbationsin TDP-43 homeostasisin protein
aggregation and ALS-FTD pathogenesis