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

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.

Functional genomic screen of human stem cell differentiation reveals pathways involved in neurodevelopment and neurodegeneration

“…Several genes within this group, including TARDBP, TIAL1, SIRT1, and PQBP1, which have recently been implicated in neurodegenerative diseases (ALS/FTLD spectrum, SMA, Lewy Body Dementia, Parkinson disease, MR, respectively), are involved in mRNA trafficking, stability, and microRNA biogenesis, associated with various types of RNA granules or involved in protein misfolding (25,26). Silencing of additional genes within these pathways (e.g., G3BP1, TAF15, and SNRPB2) in our shRNA screen displayed different PSA-NCAM phenotypes (Table S5), in line with the interaction and differential regulation of RNA granule components (27).…”

Linking RNA Dysfunction and Neurodegeneration in Amyotrophic Lateral Sclerosis

“…Within the nucleus, TDP43 has essential roles in RNA transcription, splicing, and stability [13,14,[47][48][49][50], and transports select mRNA to localized sites of translation within the cytoplasm [20,51,52]. In addition to its function in RNA trafficking, cytoplasmic TDP43 also helps regulate RNA translation and homeostasis by sequestering transcripts in RNA granules [53][54][55][56]. Thus, the loss of TDP43 function stemming from inadequate nuclear protein, a gain of function arising from the accumulation of cytoplasmic TDP43, or both, might result in RNA misprocessing and subsequent neurodegeneration.…”

“…Prion-like domains are also found in mammalian proteins whose function requires reversible selfaggregation, including proteins that are involved in the formation of stress granules [89], RNA-dense cytoplasmic particles that sequester nonessential mRNAs and prevent their translation when cells are under duress [90]. TDP43 and FUS are incorporated into cytoplasmic stress granules upon exposure to oxidative, heat, or endoplasmic reticulum stress, but return to their normal (predominantly nuclear) localization when the stress is removed [41,53,55,56,91,92]. The reversible aggregation of TDP43 and FUS, and the resulting sequestration of any bound RNAs, may be essential to their physiological functions [87]; however, disrupting the precarious balance between aggregate formation and dissolution may also contribute to the irreversible development of inclusions and the pathogenic deposition of RNA binding proteins in ALS [93] (Fig.…”

“…Prolonged or repeated insults over time may erode the ability of the cell to dissociate stress granules efficiently, altering the kinetics of the reaction and increasing stress granule stability [94,95]. ALS-linked mutations in TARDBP and FUS disrupt stress granule dynamics, favoring larger and less soluble granules [53,56]. In addition, valosin-containing protein (VCP) deficiency or chemical inhibition of VCP blocks stress granule disassembly in human cells [96].…”

Staurosporine Induced Apoptosis Rapidly Downregulates TDP-43 in Glioma Cells

“…TDP-43 is directed to stress granules (SG) in response of osmotic or oxidative stressor in many types of cells including neurons (Dewey et al, 2011). Formation of SG is significantly delayed without TDP-43 (McDonald et al, 2011). Translocation of TDP-43 from nucleus to SG in cytoplasm is mediated by RNA Recognition Motif 1 (RRM1) and glycinerich region of TDP-43, which harbors the majority of pathogenic mutations (Bentmann et al, 2012).…”