Besnard-Guérin C. Eur J Neurosci 2020.
TDP-43 is an RNA/DNA-binding protein associated with amyotrophic lateral sclerosis (ALS). Under pathological conditions, TDP-43 exported from the nucleus accumulates in the cytoplasm, forming inclusion bodies. However, the molecular mechanisms that contribute to such aggregation are unclear. The pathogenic processes that lead to aggregation in ALS were investigated by analyzing the effects of wildtype human TDP-43 or with mutations in the nuclear-localization sequence (NLS) or those associated
with ALS in stress-granule formation. TDP-43 (WT, △NLS, or G348C), with or without a GFP-tag, was expressed in SH-SY5Y neuroblastoma or HeLa cells and stress granules induced by oxidative stress or heat shock. Stress granule formation was altered in cells strongly expressing GFP-TDP-△NLS, or untagged TDP-43-△NLS in the cytoplasm but not the negative controls, GFP or GFP-UtrCH. In contrast, there was no reduction in stress-granule formation by cells that expressed untagged TDP-43 (WT or G348C) in the nucleus upon stress induction. GFP labeling of TDP-43 (WT or G348C) promotes high cytoplasm expression and nuclear aggregation. Stress granule formation was impaired in cells expressing GFP-TDP-43 (WT or G348C) in the cytoplasm. Overall, these results suggest that stress-granule formation may be inhibited by high levels of TDP-43 protein in the cytoplasm. As stress granules serve a protective function, their deregulation may promote neurodegeneration due to an aberrant stress response.