C-Jun N-terminal kinase controls TDP-43 accumulation in stress granules induced by oxidative stress

Jodi Meyerowitz,Laura J Vella,Sarah J Parker,Jeffrey R Liddell,Anthony R White,Takashi Nonaka,Katja M Kanninen,Dominic Ch Ng,Colin L Masters,Peter J Crouch,Aphrodite Caragounis,Katherine A Price,Masato Hasegawa,Qiao-Xin Li,Marie A Bogoyevitch

doi:10.1186/1750-1326-6-57

Abstract

BackgroundTDP-43 proteinopathies are characterized by loss of nuclear TDP-43 expression and formation of C-terminal TDP-43 fragmentation and accumulation in the cytoplasm. Recent studies have shown that TDP-43 can accumulate in RNA stress granules (SGs) in response to cell stresses and this could be associated with subsequent formation of TDP-43 ubiquinated protein aggregates. However, the initial mechanisms controlling endogenous TDP-43 accumulation in SGs during chronic disease are not understood. In this study we investigated the mechanism of TDP-43 processing and accumulation in SGs in SH-SY5Y neuronal-like cells exposed to chronic oxidative stress. Cell cultures were treated overnight with the mitochondrial inhibitor paraquat and examined for TDP-43 and SG processing.ResultsWe found that mild stress induced by paraquat led to formation of TDP-43 and HuR-positive SGs, a proportion of which were ubiquitinated. The co-localization of TDP-43 with SGs could be fully prevented by inhibition of c-Jun N-terminal kinase (JNK). JNK inhibition did not prevent formation of HuR-positive SGs and did not prevent diffuse TDP-43 accumulation in the cytosol. In contrast, ERK or p38 inhibition prevented formation of both TDP-43 and HuR-positive SGs. JNK inhibition also inhibited TDP-43 SG localization in cells acutely treated with sodium arsenite and reduced the number of aggregates per cell in cultures transfected with C-terminal TDP-43 162-414 and 219-414 constructs.ConclusionsOur studies are the first to demonstrate a critical role for kinase control of TDP-43 accumulation in SGs and may have important implications for development of treatments for FTD and ALS, targeting cell signal pathway control of TDP-43 aggregation.

Highlights

TAR DNA binding protein 43 (TDP-43) proteinopathies are characterized by loss of nuclear TDP-43 expression and formation of Cterminal TDP-43 fragmentation and accumulation in the cytoplasm
As heterogeneous nuclear ribonucleoprotein (hnRNP) K is known to bind to TDP-43, associate with stress granule (SG) and is phosphorylated by Jun N-terminal kinase (JNK), these findings suggest that modulation of TDP-43 SG association by JNK could be controlled through binding to hnRNP K
We show here that mild stress induced by paraquat, a well-characterized mitochondrial inhibitor and oxidative stress inducer, induced changes to TDP-43 metabolism that closely recapitulated features observed in brain and/or spinal cord of Frontotemporal dementia (FTD) and Amyotrophic lateral sclerosis (ALS) patients

Summary

Introduction

TDP-43 proteinopathies are characterized by loss of nuclear TDP-43 expression and formation of Cterminal TDP-43 fragmentation and accumulation in the cytoplasm. In 2006, TAR DNA binding protein 43 (TDP-43) was identified as the major protein constituent of ubiquitinated neuronal inclusions in FTLD-U and in non-SOD1 ALS cases [6,7]. This led to the re-classification of FTLD-U to FTLD-TDP-43, and TDP-43-positive ALS and FTLD-TDP-43 cases are referred to collectively as primary TDP-43 proteinopathies [8]. These findings provided further support for the concept of FTD and ALS as diseases within the same broad clinical spectrum. While the role of abnormal TDP-43 accumulation in both primary and secondary TDP-43 proteinopathies is not yet fully understood, the identification of TDP-43 mutations associated with ALS and FTD (~40 at present) has provided clear evidence that altered TDP-43 processing can be a primary cause of neurodegeneration and is not just a secondary phenomenon [9,10]

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