Mass spectrometric analysis of accumulated TDP-43 in amyotrophic lateral sclerosis brains

Sci Rep. 2016 Mar 16;6:23281. doi: 10.1038/srep23281.

Abstract

TDP-43 is the major disease-associated protein involved in the pathogenesis and progression of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration with ubiquitin-positive inclusions linked to TDP-43 pathology (FTLD-TDP). Abnormal phosphorylation, truncation and cytoplasmic mis-localization are known to be the characteristics for the aggregated forms of TDP-43, and gain of toxic abnormal TDP-43 or loss of function of physiological TDP-43 have been suggested as the cause of neurodegeneration. However, most of the post-translational modifications or truncation sites in the abnormal TDP-43 in brains of patients remain to be identified by protein chemical analysis. In this study, we carried out a highly sensitive liquid chromatography-mass spectrometry analysis of Sarkosyl-insoluble pathological TDP-43 from brains of ALS patients and identified several novel phosphorylation sites, deamidation sites, and cleavage sites. Almost all modifications were localized in the Gly-rich C-terminal half. Most of the cleavage sites identified in this study are novel and are located in N-terminal half, suggesting that these sites may be more accessible to proteolytic enzymes. The data obtained in this study provide a foundation for the molecular mechanisms of TDP-43 aggregation and ALS pathogenesis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Amino Acid Sequence
  • Amyotrophic Lateral Sclerosis / metabolism*
  • Brain / metabolism*
  • DNA-Binding Proteins / metabolism*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Peptide Fragments / metabolism
  • Phosphorylation
  • Protein Processing, Post-Translational
  • Tandem Mass Spectrometry

Substances

  • DNA-Binding Proteins
  • Peptide Fragments
  • TARDBP protein, human