TAR DNA-binding protein 43 (TDP-43) regulates stress granule dynamics via differential regulation of G3BP and TIA-1

Centre d'excellence en neuromique de l'Université de Montréal, Centre de recherche du CHUM, Montréal, QC, Canada.
Human Molecular Genetics (Impact Factor: 6.68). 03/2011; 20(7):1400-10. DOI: 10.1093/hmg/ddr021
Source: PubMed

ABSTRACT TAR deoxyribonucleic acid-binding protein 43 (TDP-43) is a multifunctional protein with roles in transcription, pre-messenger ribonucleic acid (mRNA) splicing, mRNA stability and transport. TDP-43 interacts with other heterogeneous nuclear ribonucleoproteins (hnRNPs), including hnRNP A2, via its C-terminus and several hnRNP family members are involved in the cellular stress response. This relationship led us to investigate the role of TDP-43 in cellular stress. Our results demonstrate that TDP-43 and hnRNP A2 are localized to stress granules (SGs), following oxidative stress, heat shock and exposure to thapsigargin. TDP-43 contributes to both the assembly and maintenance of SGs in response to oxidative stress and differentially regulates key SGs components, including TIA-1 and G3BP. The controlled aggregation of TIA-1 is disrupted in the absence of TDP-43 resulting in slowed SG formation. In addition, TDP-43 regulates the levels of G3BP mRNA, a SG nucleating factor. The disease-associated mutation TDP-43(R361S) is a loss-of-function mutation with regards to SG formation and confers alterations in levels of G3BP and TIA-1. In contrast, a second mutation TDP-43(D169G) does not impact this pathway. Thus, mutations in TDP-43 are mechanistically divergent. Finally, the cellular function of TDP-43 extends beyond splicing and places TDP-43 as a participant of the central cellular response to stress and an active player in RNA storage.

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Available from: Christine Vande Velde, May 26, 2015
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    • "However, under pathological conditions or due to chronic stress, these granules may act as precursors of the pathologic inclusions or pre-inclusions, which may transform into irreversible dense aggregates that can act as seeds of aggregation (Fig. 1B). Indeed, TDP-43 (Bentmann et al., 2012; Fujita et al., 2008; Liu-Yesucevitz et al., 2010; McDonald et al., 2011; Udan-Johns et al., 2014) and FUS (Bentmann et al., 2012; Dormann et al., 2010) are incorporated in cytoplasmic and nuclear RNA granules. Stress granules and other RNA granules are likely to act as sites of nucleation, due to the increase of local TDP-43 and FUS concentration, which could facilitate the initiation of their aggregation . "
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    ABSTRACT: Propagation of pathological protein assemblies via a prion-like mechanism has been suggested to drive neurodegenerative diseases, such as Parkinson's and Alzheimer's. Recently, amyotrophic lateral sclerosis (ALS)-linked proteins, such as SOD1, TDP-43 and FUS were shown to follow self-perpetuating seeded aggregation, thereby adding ALS to the group of prion-like disorders. The cell-to-cell spread of these pathological protein assemblies and their pathogenic mechanism is poorly understood. However, as ALS is a non-cell autonomous disease and pathology in glial cells was shown to contribute to motor neuron damage, spreading mechanisms are likely to underlie disease progression via the interplay between affected neurons and their neighboring glial cells.
    Virus Research 02/2015; 8. DOI:10.1016/j.virusres.2014.12.032 · 2.83 Impact Factor
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    • "In addition to cytoplasmic redistribution, we showed that the M337V mutation had a clear effect on increasing the number of cytoplasmic TDP-43 aggregates, even in the absence of external cellular stressors, while the A382T mutation required ER stress induction to elevate levels of cytoplasmic aggregates. Similar TDP-43 cytoplasmic aggregates have been previously reported and associated with stress granules (McDonald et al, 2011). Under basal and ER stress conditions , nuclear TDP-43 aggregates were detected more frequently in cells expressing the M337V and A382T mutations compared with cells expressing wt-TDP. "
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    ABSTRACT: The transactive response DNA binding protein (TDP-43) is a major component of the characteristic neuronal cytoplasmic inclusions seen in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Furthermore, pathogenic mutations in the gene encoding TDP-43, TARDBP, are found in sporadic and familial ALS cases. To study the molecular mechanisms of cellular toxicity due to TDP-43 mutations we generated a novel in vitro cellular model using a fluorescently tagged human genomic TARDBP locus carrying one of two ALS-associated mutations, A382T or M337V, which were used to generate site-specific bacterial artificial chromosome (BAC) human stable cell lines and BAC transgenic mice. In cell lines and primary motor neurons in culture, TDP-M337V mislocalized to the cytoplasm more frequently than wild-type TDP (wt-TDP) and TDP-A382T, an effect potentiated by oxidative stress. Expression of mutant TDP-M337V correlated with increased apoptosis detected by cleaved caspase-3 staining. Cells expressing mislocalized TDP-M337V spontaneously developed cytoplasmic aggregates, while for TDP-A382T aggregates were only revealed after endoplasmic reticulum (ER) stress induced by the calcium-modifying drug thapsigargin. Lowering Ca(2+) concentration in the ER of wt-TDP cells partially recapitulated the effect of pathogenic mutations by increasing TDP-43 cytoplasmic mislocalization, suggesting Ca(2+) dysregulation as a potential mediator of pathology through alterations in Bcl-2 protein levels. Ca(2+) signalling from the ER was impaired in immortalized cells and primary neurons carrying TDP-43 mutations, with a 50% reduction in the levels of luminal ER Ca(2+) stores content and delayed Ca(2+) release compared to cells carrying wt-TDP. The deficits in Ca(2+) release in human cells correlated with upregulation of Bcl-2 and siRNA-mediated knockdown of Bcl-2 restored the amplitude of Ca(2+) oscillations in TDP-M337V cells. These results suggest that TDP-43 pathogenic mutations elicit cytoplasmic mislocalization of TDP-43 and Bcl-2 mediated ER Ca(2+) signaling dysregulation. Copyright © 2014. Published by Elsevier Inc.
    Neurobiology of Disease 12/2014; 75. DOI:10.1016/j.nbd.2014.12.010 · 5.20 Impact Factor
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    • "The most comprehensive study on the functional role of TDP-43 in SGs and cellular stress response has been performed by McDonald et al. (2011) (75). These authors showed that TDP-43 and its binding partner hnRNP A2 are components of SGs formed in response to oxidative stress. "
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    ABSTRACT: Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease caused by the death of motor neurons. While the exact molecular and cellular basis for motor neuron death is not yet fully understood, the current conceptualization is that multiple aberrant biological processes contribute. Among these, one of the most compelling is based on alterations of RNA metabolism. In this review, we examine how the normal process of cellular response to stress leading to RNA stress granule formation might become pathological, resulting in the formation of stable protein aggregates. We discuss the emerging roles of post-translational modifications of RNA binding proteins in the genesis of these aggregates. We also review the contemporary literature regarding the potential role for more widespread alterations in RNA metabolism in ALS, including alterations in miRNA biogenesis, spliceosome integrity and RNA editing. A hypothesis is presented in which aberrant RNA processing, modulated through pathological stress granule formation as a reflection of either mutations within intrinsically disordered or prion-like domains of critical RNA binding proteins, or the post-translational modification of RNA binding proteins, contributes directly to motor neuron death.
    02/2014; 15(5-6). DOI:10.3109/21678421.2014.881377
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