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Sci Rep. 2018 Apr 16;8(1):6030. doi: 10.1038/s41598-018-24463-3.

Elimination of TDP-43 inclusions linked to amyotrophic lateral sclerosis by a misfolding-specific intrabody with dual proteolytic signals.

Author information

1
Department of Neurology, Shiga University of Medical Science, Otsu, Japan.
2
Department of Neurology, Kyoto University Graduate School of Medicine, Kyoto, Japan.
3
Molecular Neuroscience Research Center, Shiga University of Medical Science, Otsu, Japan.
4
Department of Chemistry, Keio University, Yokohama, Japan.
5
Department of Neurology, Shiga University of Medical Science, Otsu, Japan. uru@belle.shiga-med.ac.jp.
6
Molecular Neuroscience Research Center, Shiga University of Medical Science, Otsu, Japan. uru@belle.shiga-med.ac.jp.

Abstract

Aggregation of TAR DNA-binding protein of 43 kDa (TDP-43) is implicated in the pathogenesis of sporadic and certain familial forms of amyotrophic lateral sclerosis (ALS), suggesting elimination of TDP-43 aggregates as a possible therapeutic strategy. Here we generated and investigated a single-chain variable fragment (scFv) derived from the 3B12A monoclonal antibody (MAb) that recognises D247 of the TDP-43 nuclear export signal, an epitope masked in the physiological state. In transfected HEK293A cells, 3B12A scFv recapitulated the affinity of the full-length MAb to mislocalised TDP-43 with a defective nuclear localising signal and to a TDP-43 inclusion mimic with cysteine-to-serine substitution at RRM1. Moreover, 3B12A scFv accelerated proteasome-mediated degradation of aggregated TDP-43, likely due to an endogenous PEST-like proteolytic signal sequence in the VH domain CDR2 region. Addition of the chaperone-mediated autophagy (CMA)-related signal to 3B12A scFv induced HSP70 transcription, further enhancing TDP-43 aggregate clearance and cell viability. The 3B12A scFv also reduced TDP-43 aggregates in embryonic mouse brain following in utero electroporation while causing no overt postnatal brain pathology or developmental anomalies. These results suggest that a misfolding-specific intrabody prone to synergistic proteolysis by proteasomal and autophagic pathways is a promising strategy for mitigation of TDP-43 proteinopathy in ALS.

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