Tryptophan residues in TDP-43 and SOD1 modulate the cross-seeding and toxicity of SOD1

J Biol Chem. 2024 May;300(5):107207. doi: 10.1016/j.jbc.2024.107207. Epub 2024 Mar 22.


Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease of motor neurons. Neuronal superoxide dismutase-1 (SOD1) inclusion bodies are characteristic of familial ALS with SOD1 mutations, while a hallmark of sporadic ALS is inclusions containing aggregated WT TAR DNA-binding protein 43 (TDP-43). We show here that co-expression of mutant or WT TDP-43 with SOD1 leads to misfolding of endogenous SOD1 and aggregation of SOD1 reporter protein SOD1G85R-GFP in human cell cultures and promotes synergistic axonopathy in zebrafish. Intriguingly, this pathological interaction is modulated by natively solvent-exposed tryptophans in SOD1 (tryptophan-32) and TDP-43 RNA-recognition motif RRM1 (tryptophan-172), in concert with natively sequestered TDP-43 N-terminal domain tryptophan-68. TDP-43 RRM1 intrabodies reduce WT SOD1 misfolding in human cell cultures, via blocking tryptophan-172. Tryptophan-68 becomes antibody-accessible in aggregated TDP-43 in sporadic ALS motor neurons and cell culture. 5-fluorouridine inhibits TDP-43-induced G85R-GFP SOD1 aggregation in human cell cultures and ameliorates axonopathy in zebrafish, via its interaction with SOD1 tryptophan-32. Collectively, our results establish a novel and potentially druggable tryptophan-mediated mechanism whereby two principal ALS disease effector proteins might directly interact in disease.

Keywords: ALS; SOD1; TDP-43; cross-seeding; prion-like propagation; protein aggregation.

MeSH terms

  • Amyotrophic Lateral Sclerosis* / genetics
  • Amyotrophic Lateral Sclerosis* / metabolism
  • Amyotrophic Lateral Sclerosis* / pathology
  • Animals
  • DNA-Binding Proteins* / genetics
  • DNA-Binding Proteins* / metabolism
  • Humans
  • Motor Neurons / metabolism
  • Motor Neurons / pathology
  • Protein Folding
  • Superoxide Dismutase-1* / chemistry
  • Superoxide Dismutase-1* / genetics
  • Superoxide Dismutase-1* / metabolism
  • Tryptophan* / metabolism
  • Zebrafish*


  • Tryptophan
  • Superoxide Dismutase-1
  • TARDBP protein, human
  • DNA-Binding Proteins
  • SOD1 protein, human