Stress Granule Assembly Can Facilitate but Is Not Required for TDP-43 Cytoplasmic Aggregation

• Main Authors: Nikita Fernandes, Luke Nero, Shawn M. Lyons, Pavel Ivanov, Telsa M. Mittelmeier, Timothy A. Bolger, J. Ross Buchan
• Format: Article
• Language: English
• Published: MDPI AG 2020-09-01
• Series: Biomolecules
• Subjects: TDP-43; stress granules; P-bodies
• Online Access: https://www.mdpi.com/2218-273X/10/10/1367

Stress granules (SGs) are hypothesized to facilitate TAR DNA-binding protein 43 (TDP-43) cytoplasmic mislocalization and aggregation, which may underly amyotrophic lateral sclerosis pathology. However, much data for this hypothesis is indirect. Additionally, whether P-bodies (PBs; related mRNA-protein granules) affect TDP-43 phenotypes is unclear. Here, we determine that induction of TDP-43 expression in yeast results in the accumulation of SG-like foci that in >90% of cases become the sites where TDP-43 cytoplasmic foci first appear. Later, TDP-43 foci associate less with SGs and more with PBs, though independent TDP-43 foci also accumulate. However, depleting or over-expressing yeast SG and PB proteins reveals no consistent trend between SG or PB assembly and TDP-43 foci formation, toxicity or protein abundance. In human cells, immunostaining endogenous TDP-43 with different TDP-43 antibodies reveals distinct localization and aggregation behaviors. Following acute arsenite stress, all phospho-TDP-43 foci colocalize with SGs. Interestingly, in SG assembly mutant cells (<i>G3BP1/2ΔΔ</i>), TDP-43 is enriched in nucleoli. Finally, formation of TDP-43 cytoplasmic foci following low-dose chronic arsenite stress is impaired, but not completely blocked, in <i>G3BP1/2ΔΔ </i>cells. Collectively, our data suggest that SG and PB assembly may facilitate TDP-43 cytoplasmic localization and aggregation but are likely not essential for these events.