Active nuclear import and passive nuclear export are the primary determinants of TDP-43 localization

Sci Rep. 2018 May 4;8(1):7083. doi: 10.1038/s41598-018-25008-4.

Abstract

ALS (Amyotrophic Lateral Sclerosis) is a neurodegenerative disease characterized by the redistribution of the RNA binding protein TDP-43 in affected neurons: from predominantly nuclear to aggregated in the cytosol. However, the determinants of TDP-43 localization and the cellular insults that promote redistribution are incompletely understood. Here, we show that the putative Nuclear Export Signal (NES) is not required for nuclear egress of TDP-43. Moreover, when the TDP-43 domain which contains the putative NES is fused to a reporter protein, YFP, the presence of the NES is not sufficient to mediate nuclear exclusion of the fusion protein. We find that the previously studied "∆NES" mutant, in which conserved hydrophobic residues are mutated to alanines, disrupts both solubility and splicing function. We further show that nuclear export of TDP-43 is independent of the exportin XPO1. Finally, we provide evidence that nuclear egress of TDP-43 is size dependent; nuclear export of dTomato TDP-43 is significantly impaired compared to Flag TDP-43. Together, these results suggest nuclear export of TDP-43 is predominantly driven by passive diffusion.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Active Transport, Cell Nucleus*
  • Amino Acid Sequence
  • Animals
  • Binding Sites
  • Cell Line
  • DNA-Binding Proteins / chemistry
  • DNA-Binding Proteins / metabolism*
  • Genes, Reporter
  • Humans
  • Karyopherins / chemistry
  • Karyopherins / metabolism
  • Mice
  • Models, Molecular
  • Nuclear Export Signals
  • Protein Binding
  • Protein Conformation
  • Protein Interaction Domains and Motifs
  • Protein Transport
  • Pyramidal Cells / metabolism
  • Rats
  • Receptors, Cytoplasmic and Nuclear / chemistry
  • Receptors, Cytoplasmic and Nuclear / metabolism
  • Ribonucleoside Diphosphate Reductase / chemistry
  • Ribonucleoside Diphosphate Reductase / metabolism

Substances

  • DNA-Binding Proteins
  • Karyopherins
  • Nuclear Export Signals
  • Receptors, Cytoplasmic and Nuclear
  • TARDBP protein, human
  • exportin 1 protein
  • ribonucleotide reductase M2
  • Ribonucleoside Diphosphate Reductase