[PDF][PDF] ALS mutations disrupt phase separation mediated by α-helical structure in the TDP-43 low-complexity C-terminal domain

AE Conicella, GH Zerze, J Mittal, NL Fawzi - Structure, 2016 - cell.com
AE Conicella, GH Zerze, J Mittal, NL Fawzi
Structure, 2016cell.com
RNA-binding protein TDP-43 mediates essential RNA processing but forms cytoplasmic
neuronal inclusions via its C-terminal domain (CTD) in amyotrophic lateral sclerosis (ALS). It
remains unclear if aggregated TDP-43 is neurotoxic and if∼ 50 ALS-associated missense
mutations in TDP-43 CTD promote aggregation, or if loss of normal function plays a role in
disease. Recent work points to the ability of related proteins to assemble into functional
phase-separated ribonucleoprotein granules via their structurally disordered prion-like …
Summary
RNA-binding protein TDP-43 mediates essential RNA processing but forms cytoplasmic neuronal inclusions via its C-terminal domain (CTD) in amyotrophic lateral sclerosis (ALS). It remains unclear if aggregated TDP-43 is neurotoxic and if ∼50 ALS-associated missense mutations in TDP-43 CTD promote aggregation, or if loss of normal function plays a role in disease. Recent work points to the ability of related proteins to assemble into functional phase-separated ribonucleoprotein granules via their structurally disordered prion-like domains. Here, we provide atomic details on the structure and assembly of the low-complexity CTD of TDP-43 into liquid-liquid phase-separated in vitro granules and demonstrate that ALS-associated variants disrupt interactions within granules. Using nuclear magnetic resonance spectroscopy, simulation, and microscopy, we find that a subregion cooperatively but transiently folds into a helix that mediates TDP-43 phase separation. ALS-associated mutations disrupt phase separation by inhibiting interaction and helical stabilization. Therefore, ALS-associated mutations can disrupt TDP-43 interactions, affecting function beyond encouraging aggregation.
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