In Situ Structure of Neuronal C9orf72 Poly-GA Aggregates Reveals Proteasome Recruitment

Publication date: Available online 1 February 2018 Source:Cell Author(s): Qiang Guo, Carina Lehmer, Antonio Martínez-Sánchez, Till Rudack, Florian Beck, Hannelore Hartmann, Manuela Pérez-Berlanga, Frédéric Frottin, Mark S. Hipp, F. Ulrich Hartl, Dieter Edbauer, Wolfgang Baumeister, Rubén Fernández-Busnadiego Protein aggregation and dysfunction of the ubiquitin-proteasome system are hallmarks of many neurodegenerative diseases. Here, we address the elusive link between these phenomena by employing cryo-electron tomography to dissect the molecular architecture of protein aggregates within intact neurons at high resolution. We focus on the poly-Gly-Ala (poly-GA) aggregates resulting from aberrant translation of an expanded GGGGCC repeat in C9orf72, the most common genetic cause of amyotrophic lateral sclerosis and frontotemporal dementia. We find that poly-GA aggregates consist of densely packed twisted ribbons that recruit numerous 26S proteasome complexes, while other macromolecules are largely excluded. Proximity to poly-GA ribbons stabilizes a transient substrate-processing conformation of the 26S proteasome, suggesting stalled degradation. Thus, poly-GA aggregates may compromise neuronal proteostasis by driving the accumulation and functional impairment of a large fraction of cellular proteasomes. Graphical abstract Teaser Neuronal poly-GA aggregates linked to amyotrophic lateral sclerosis and frontotemporal dementia selecti...
Source: Cell - Category: Cytology Source Type: research

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AbstractInsoluble aggregates containing TDP-43 are widely observed in the diseased brain, and defined as “TDP-43 pathology” in a spectrum of neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS), Alzheimer’s disease and ALS with frontotemporal dementia. Here we report that Betz cells of patients with TDP-43 pathology display a distinct set of intracellular defects especially at the site of nuclear membrane, mitochondria and endoplasmic reticulum (ER). Numerous TDP-43 mouse models have been generated to discern the cellular and molecular basis of the disease, but mechanisms of neuronal vu...
Source: Acta Neuropathologica - Category: Neurology Source Type: research
TDP-43 aggregates in neurons and glia are the defining pathological hallmark of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), raising the possibility of glial damage in the disease pathogenesis. However, the normal physiological functions of TDP-43 in glia are largely unknown. To address how TDP-43 may be required for...
Source: Proceedings of the National Academy of Sciences - Category: Science Authors: Tags: PNAS Plus Source Type: research
In this study, we identified Xrp1, a nuclear chromatin-binding protein, as a key modifier of caz mutant phenotypes. Xrp1 expression was strongly up-regulated in caz mutants, and Xrp1 heterozygosity rescued their motor defects and life span. Interestingly, selective neuronal Xrp1 knockdown was sufficient to rescue, and neuronal Xrp1 overexpression phenocopied caz mutant phenotypes. The caz/Xrp1 genetic interaction depended on the functionality of the AT-hook DNA-binding domain in Xrp1, and the majority of Xrp1-interacting proteins are involved in gene expression regulation. Consistently, caz mutants displayed gene expressio...
Source: Journal of Cell Biology - Category: Cytology Authors: Tags: Chromatin or Epigenetics, DNA Biology, Neuroscience Articles Source Type: research
We report here that C9orf72, which is linked to the most common forms of the neurodegenerative diseases amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), is a key regulator of lipid metabolism under stress. Loss of C9orf72 leads to an overactivation of starvation-induced lipid metabolism that is mediated by dysregulated autophagic digestion of lipids and increased de novo fatty acid synthesis. C9orf72 acts by promoting the lysosomal degradation of coactivator-associated arginine methyltransferase 1 (CARM1), which in turn regulates autophagy–lysosomal functions and lipid metabolism. In ALS/FTD pat...
Source: Genes and Development - Category: Genetics & Stem Cells Authors: Tags: Research Papers Source Type: research
UBQLN2 is one of a family of proteins implicated in ubiquitin-dependent protein quality control and integrally tied to human neurodegenerative disease. Whereas wild-type UBQLN2 accumulates in intraneuronal deposits in several common age-related neurodegenerative diseases, mutations in the gene encoding this protein result in X-linked amyotrophic lateral sclerosis/frontotemporal dementia associated with...
Source: Proceedings of the National Academy of Sciences - Category: Science Authors: Tags: PNAS Plus Source Type: research
Publication date: October 2018Source: PM&R, Volume 10, Issue 10Author(s): Flora M. Hammond, William Sauve, Fred Ledon, Charles Davis, Andrea E. FormellaAbstractBackgroundDextromethorphan 20 mg / quinidine 10 mg (DM/Q) was approved to treat pseudobulbar affect (PBA) based on phase 3 trials conducted in participants with amyotrophic lateral sclerosis or multiple sclerosis. PRISM II evaluated DM/Q effectiveness, safety, and tolerability for PBA following stroke, dementia, or traumatic brain injury (TBI).ObjectiveTo report results from the TBI cohort of PRISM II, including a TBI-specific functional scale.DesignOpen-label trial...
Source: PMandR - Category: Rehabilitation Source Type: research
In this study, we attempted to delineate the aggregation-prone sequences of the structural domain of TDP-43. Here, we investigated the self-assembly of peptides of TDP-43 using aggregation prediction algorithms, Zipper DB and AMYLPRED2. The three aggregation-prone peptides identified were from N-terminal domain (24GTVLLSTV31), and RNA recognition motifs, RRM1 (128GEVLMVQV135) and RRM2 (247DLIIKGIS254). Furthermore, the amyloid fibril forming propensities of these peptides were analyzed through different biophysical techniques and molecular dynamics simulation. Our study shows the different aggregation ability of conserved ...
Source: Biochimica et Biophysica Acta (BBA) Proteins and Proteomics - Category: Biochemistry Source Type: research
(University of Bath) The normal function of a gene associated with the neurodegenerative diseases amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) has been determined for the first time by University of Bath scientists.
Source: EurekAlert! - Medicine and Health - Category: International Medicine & Public Health Source Type: news
Publication date: Available online 20 October 2018Source: Biochimica et Biophysica Acta (BBA) - Molecular Basis of DiseaseAuthor(s): Samantha N. Cobos, Seth A. Bennett, Mariana P. TorrenteAbstractEvery year, neurodegenerative disorders take more than 5000 lives in the US alone. Cures have not yet been found for many of the multitude of neuropathies. The majority of amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD) and Parkinson's disease (PD) cases have no known genetic basis. Thus, it is evident that contemporary genetic approaches have failed to explain the etiology or etiologies of ALS/FTD and PD. Recen...
Source: Biochimica et Biophysica Acta (BBA) Molecular Basis of Disease - Category: Molecular Biology Source Type: research
Microsatellite expansions cause more than 40 neurological disorders, including Huntington's disease, myotonic dystrophy, and C9ORF72 amyotrophic lateral sclerosis/frontotemporal dementia (ALS/FTD). These repeat expansion mutations can produce repeat-associated non-ATG (RAN) proteins in all three reading frames, which accumulate in disease-relevant tissues. There has been considerable interest in RAN protein products and their downstream consequences, particularly for the dipeptide proteins found in C9ORF72 ALS/FTD. Understanding how RAN translation occurs, what cellular factors contribute to RAN protein accumulation, and h...
Source: Journal of Biological Chemistry - Category: Chemistry Authors: Tags: Minireviews Source Type: research
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