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Gel-like inclusions of C-terminal fragments of TDP-43 sequester stalled proteasomes in neurons

ABSTRACT: Aggregation of the multifunctional RNA-binding protein TDP-43 defines large subgroups of amyotrophic lateral sclerosis and frontotemporal dementia and correlates with neurodegeneration in both diseases. In disease, characteristic C-terminal fragments of ~25 kDa ("TDP-25") accumulate in cytoplasmic inclusions. Here, we analyzed gain-of-function mechanisms of TDP-25 combining cryo-electron tomography, proteomics and functional assays. In neurons, cytoplasmic TDP-25 inclusions are amorphous and photobleaching experiments revealed gel-like biophysical properties far less dynamic than nuclear TDP-43. Compared to full length TDP-43, the TDP-25 interactome was depleted of lowcomplexity domain proteins. TDP-25 inclusions are enriched in 26S proteasomes adopting exclusively substrate-processing conformations, suggesting that inclusions sequester proteasomes, which are largely stalled and no longer undergo the cyclic conformational changes required for proteolytic activity. Reporter assays confirmed that TDP-25 impaired proteostasis, which is further enhanced by ALS-causing mutations. These findings bolster the importance of proteasome dysfunction in ALS/FTD. Key words ALS / neurodegeneration / phase separation / proteasome / TDP-43 Introduction

INSTRUMENT(S): Orbitrap Exploris 480

ORGANISM(S): Rattus Norvegicus (rat)

TISSUE(S): Brain, Primary Motor Neuron, Cell Culture

DISEASE(S): Frontotemporal Dementia And/or Amyotrophic Lateral Sclerosis-3

SUBMITTER: Mario Oroshi

LAB HEAD: Matthias Mann

PROVIDER: PXD031083 | Pride | 2022-05-08

REPOSITORIES: Pride

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Gel-like inclusions of C-terminal fragments of TDP-43 sequester and inhibit proteasomes

Project description:TDP-43 inclusions enriched in C-terminal terminal fragments of ~25 kDa ("TDP-25") are associated with neurodegeneration in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Here, we analyzed gain-of-function mechanisms of TDP-25 combining cryo-electron tomography, proteomics and functional assays. We show that TDP-25 inclusions are amorphous with gel-like properties. Inclusions sequester proteasomes adopting exclusively substrate-processing conformations. This leads to proteostasis impairment, further enhanced by pathogenic mutations. These findings bolster the importance of proteasome dysfunction in ALS/FTD.

2022-04-14 | PXD024358 | Pride

TDP-43 is a genome-wide DNA-binding protein and regulator of snRNA expression

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Altered Distributions of SMN-containing GEMs and Mitochondria in Motor Neurons of TDP-43 transgenic Mice

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Distinct and shared functions of ALS-associated TDP-43, FUS, and TAF15 revealed by comprehensive multi-system integrative analyses [RNA-Seq_Stability]

Project description:TDP-43, FUS, and TAF15 are implicated in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia. We integrate CLIP-seq and RNA Bind-N-Seq technologies to discover that TAF15 binds to ~4,900 RNAs enriched for GGUA motifs. In the mouse brain, TAF15 and FUS, but not TDP-43, exhibit strikingly similar RNA binding profiles, yet they alter the expression of distinct mRNA populations upon their individual depletions. TAF15 has a minimal role in alternative splicing and instead affects RNA turnover, consistent with an enrichment of TAF15 binding sites in 3â untranslated regions. In human stem cell-derived motor neurons, loss of both TAF15 and FUS affected mRNAs distinct from those altered by loss of either protein alone, revealing redundant roles for TAF15 and FUS in maintaining mRNA levels. Furthermore, concomitant rather than individual depletion of TAF15 and FUS more closely resembles RNA profiles of motor neurons derived from FUS R521G ALS patients or from late-stage, sporadic ALS patients. Our study reveals convergent and divergent mechanisms by which FUS, TAF15 and TDP-43 affects RNA metabolism in neurological disease. RNA-seq, CLIP-seq and arrays in mouse and human against TAF15 knockdowns This Series represents RNA-seq sample(s).

2016-07-05 | E-GEOD-77704 | biostudies-arrayexpress

TDP-43 Interactor and Motor Neuron Tagged Ribosome Affinity Purification in a Drosophila Model of ALS

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