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

• Published in: Scientific reports 2018-05, Vol.8 (1), p.7083-16, Article 7083
• Main Authors: Pinarbasi, Emile S., Cağatay, Tolga, Fung, Ho Yee Joyce, Li, Ying C., Chook, Yuh Min, Thomas, Philip J.
• Format: Article
• Language: English
• Subjects: 13; 13/109; 13/89; 14; 14/1; 631/378/1689; 631/80/389; 82; 82/47; Active Transport, Cell Nucleus; Amino Acid Sequence; Amyotrophic lateral sclerosis; Animals; Binding Sites; Cell Line; Cytosol; DNA-Binding Proteins - chemistry; DNA-Binding Proteins - metabolism; Exportin 1 Protein; Fusion protein; Genes, Reporter; Humanities and Social Sciences; Humans; Hydrophobicity; Karyopherins - chemistry; Karyopherins - metabolism; Localization; Mice; Models, Molecular; multidisciplinary; Nuclear Export Signals; Nuclear transport; Protein Binding; Protein Conformation; Protein Interaction Domains and Motifs; Protein Transport; Proteins; Pyramidal Cells - metabolism; Rats; Receptors, Cytoplasmic and Nuclear - chemistry; Receptors, Cytoplasmic and Nuclear - metabolism; Ribonucleic acid; Ribonucleoside Diphosphate Reductase - chemistry; Ribonucleoside Diphosphate Reductase - metabolism; RNA; RNA-binding protein; Science; Science (multidisciplinary); Splicing
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-018-25008-4

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.