TDP-43 mutations causing amyotrophic lateral sclerosis are associated with altered expression of RNA-binding protein hnRNP K and affect the Nrf2 antioxidant pathway.
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 metabolism by 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 downstream antioxidant 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.
Department of Pathology, The University of Melbourne, Victoria 3010, Australia.
Diane
D
Moujalled
Department of Pathology, The University of Melbourne, Victoria 3010, Australia.
Alexandra
A
Grubman
Department of Pathology, The University of Melbourne, Victoria 3010, Australia.
Karla
K
Acevedo
The Australian School of Advanced Medicine, Macquarie University, NSW 2109, Australia.
Shu
S
Yang
Dementia Research Unit, Department of Anatomy, Faculty of Medicine, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia.
Yazi D
YD
Ke
Australian Centre for Blood Diseases (ACBD), The Alfred Centre, Victoria 3004, Australia.
Donia M
DM
Moujalled
Florey Institute of Neuroscience and Mental Health, Parkville, Victoria 3010, Australia.
Clare
C
Duncan
Department of Pathology, The University of Melbourne, Victoria 3010, Australia.
Aphrodite
A
Caragounis
Florey Institute of Neuroscience and Mental Health, Parkville, Victoria 3010, Australia.
Nirma D
ND
Perera
Florey Institute of Neuroscience and Mental Health, Parkville, Victoria 3010, Australia.
Bradley J
BJ
Turner
Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224, USA.
Mercedes
M
Prudencio
Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224, USA.
Leonard
L
Petrucelli
The Australian School of Advanced Medicine, Macquarie University, NSW 2109, Australia.
Ian
I
Blair
Dementia Research Unit, Department of Anatomy, Faculty of Medicine, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia.
Lars M
LM
Ittner
Department of Pathology, The University of Melbourne, Victoria 3010, Australia.|Florey Institute of Neuroscience and Mental Health, Parkville, Victoria 3010, Australia.
Peter J
PJ
Crouch
Department of Pathology, The University of Melbourne, Victoria 3010, Australia.
Jeffrey R
JR
Liddell
Department of Pathology, The University of Melbourne, Victoria 3010, Australia.|Florey Institute of Neuroscience and Mental Health, Parkville, Victoria 3010, Australia.|Berghofer Medical Research Institute, Herston, Queensland 4006, Australia.
Anthony R
AR
White
D000818:Animals; D006801:Humans; D051379:Mice; D000690:Amyotrophic Lateral Sclerosis / Q000235:genetics / Q000378:metabolism; D000975:Antioxidants; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D057180:Frontotemporal Dementia / Q000378:metabolism; D057174:Frontotemporal Lobar Degeneration / Q000235:genetics; D034641:Heterogeneous-Nuclear Ribonucleoprotein K / Q000235:genetics / Q000378:metabolism; D034441:Heterogeneous-Nuclear Ribonucleoproteins / Q000235:genetics; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009046:Motor Neurons / Q000378:metabolism; D009154:Mutation; D051267:NF-E2-Related Factor 2 / Q000378:metabolism; D012313:RNA / Q000378:metabolism; D013116:Spinal Cord / Q000378:metabolism
D000975:Antioxidants; D004268:DNA-Binding Proteins; D034641:Heterogeneous-Nuclear Ribonucleoprotein K; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D012313:RNA; C000598624:TARDBP protein, human