TDP-43 mutations causing amyotrophic lateral sclerosis are associated with altered expression of RNA-binding protein hnRNP K and affect the Nrf2 antioxidant pathway

Diane Moujalled*, Alexandra Grubman, Karla Acevedo, Shu Yang, Yazi D. Ke, Donia M. Moujalled, Clare Duncan, Aphrodite Caragounis, Nirma D. Perera, Bradley J. Turner, Mercedes Prudencio, Leonard Petrucelli, Ian Blair, Lars M. Ittner, Peter J. Crouch, Jeffrey R. Liddell, Anthony R. White

*Corresponding author for this work

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

TAR DNA binding protein 43 (TDP-43) is a major disease-associated protein involved in the pathogenesis of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-U). Our previous studies found a direct association between TDP-43 and heterogeneous nuclear ribonucleoprotein K (hnRNP K). In this study, utilizing ALS patient fibroblasts harboring a TDP-43M337V mutation and NSC-34 motor neuronal cell line expressing TDP-43Q331K mutation, we show that hnRNP K expression is impaired in urea soluble extracts from mutant TDP-43 cell models. This was confirmed in vivo using TDP-43Q331K and inducible TDP-43A315T murine ALS models. We further investigated the potential pathological effects of mutant TDP-43-mediated changes to hnRNP K metabolismby RNA binding immunoprecipitation analysis. hnRNP K protein was bound to antioxidant NFE2L2 transcripts encoding Nrf2 antioxidant transcription factor, with greater enrichment in TDP-43M337V patient fibroblasts compared to healthy controls. Subsequent gene expression profiling revealed an increase in downstreamantioxidant transcript expression of Nrf2 signaling in the spinal cord of TDP-43Q331K mice compared to control counterparts, yet the corresponding protein expression was not up-regulated in transgenic mice. Despite the elevated expression of antioxidant transcripts, we observed impaired levels of glutathione (downstream Nrf2 antioxidant) in TDP-43M337V patient fibroblasts and astrocyte cultures from TDP-43Q331K mice, indicative of elevated oxidative stress and failure of some upregulated antioxidant genes to be translated into protein. Our findings indicate that further exploration of the interplay between hnRNP K (or other hnRNPs) and Nrf2-mediated antioxidant signaling is warranted and may be an important driver for motor neuron degeneration in ALS.

Original languageEnglish
Article numberddx093
Pages (from-to)1732-1746
Number of pages15
JournalHuman Molecular Genetics
Volume26
Issue number9
DOIs
Publication statusPublished - 1 May 2017

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