Molecular Modulation of the Crosstalk Between TDP-43 and SOD1.

Glycation of superoxide dismutase 1 (SOD1) has been shown to modulate the cytosolic levels of phosphorylated TAR DNA-binding protein 43 (TDP-43), a hallmark of amyotrophic lateral sclerosis (ALS) pathology. In this study, we investigated the interaction between TDP-43 and SOD1 and assessed how methylglyoxal (MGO)-induced glycation and the ALS-associated G93A SOD1 mutation affect this interplay in H4 cells. MGO exposure reduced SOD1 activity and TDP-43 phosphorylation in cells expressing WT SOD1, but not in those expressing G93A SOD1. Both WT and mutant SOD1 interacted with TDP-43 in the nucleus and cytosol; however, cytosolic interactions were more prevalent in G93A-expressing cells. Although MGO did not significantly alter the overall interaction between TDP-43 and WT SOD1, it induced cytosolic inclusion formation at 0.4 mM, a concentration associated with reduced cell viability. These inclusions did not colocalize with stress granules, indicating alternative aggregation pathways. Treatment with cyclosporin A, which inhibits the phosphatase calcineurin, decreased both TDP-43-WT SOD1 inclusions and cytosolic interactions between TDP-43 and G93A SOD1. Together, these findings suggest that SOD1 damage, induced by glycation or ALS-linked mutation, may affect TDP-43 phosphorylation status and promote its cytosolic mislocalization and aggregation, providing new insights into ALS-associated proteinopathy.