Amisodin alleviates TDP-43-associated ALS pathology by inhibiting the trimeric SOD1

Background Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by the progressive loss of motor neurons, in which aggregations of TDP-43 and SOD1 represents a central pathogenic hallmark. Despite both proteins constitute major genetic and molecular determinants of ALS, the mechanistic link these two hallmark proteins remain poorly understood. Methods To investigate the functional interplay between SOD1 and TDP-43, in vitro SOD1/TDP-43 oligomerization assays, immunofluorescence analyses, and protein–protein interaction assays were performed. Trimer-stabilizing and -destabilizing SOD1 expression constructs and recombinant proteins were employed to assess whether TDP-43–associated pathology depends on the conformational state of SOD1. To model TDP-43–related sporadic ALS in vivo, compound hTDP-43(+/+)/mSOD1(−/−) mice were generated and analyzed for progressive motor neuron loss and motor dysfunction driven by SOD1 aggregation. The therapeutic efficacy of Amisodin, a selective inhibitor of trimeric SOD1, was evaluated using hTDP-43 (+/+), hTDP-43 (+/-) and SOD1G93A transgenic mouse models. ALS-related pathological phenotypes were assessed by behavioral testing, neurofilament light chain (NF-L) measurements, and histological analysis. Results We demonstrate that cytoplasmic translocation of TDP-43, induced by its overexpression or cellular stress, directly binds to trimeric SOD1 via RNA recognition motif of TDP-43, thereby accelerating SOD1 aggregation. Conversely, destabilization of SOD1 trimers disrupts the TDP-43-SOD1 interaction, leading to a marked reduction in TDP-43 aggregation. Interestingly, ALS disease phenotypes observed in homozygous hTDP-43(+/+) transgenic mice were significantly alleviated in a SOD1 deficient background, indicating that TDP-43-driven neurodegeneration is contingent upon the expression of SOD1. Building upon these mechanistic insights, we evaluated Amisodin, a selective inhibitor targeting trimeric SOD1. Amisodin treatment effectively prevented cytoplasmic mislocalization of TDP-43 and conferred neuroprotective benefits in hTDP-43 Tg mice. Conclusions Together, our findings identify SOD1-dependent TDP-43 mislocalization and aggregation as a critical driver of ALS pathogenesis and highlight inhibition of trimeric SOD1 by Amisodin as a promising therapeutic strategy for TDP-43-associated ALS disease.