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Impact of oligoarginine peptides in RNA-binding proteomes

ABSTRACT: Expanded intronic GGGGCC repeats in C9ORF72 produce several dipeptides, from which the two that contain arginine, (PR)n and (GR)n, accumulate at nucleoli and kill cells. While this toxicity plays an important role in ALS pathogenesis, its mechanism remains unknown. We here show that PR dipeptides bind avidly to DNA and RNA, so that any cellular reaction involving nucleic acids is impaired by the dipeptides. Consistently, PR-induced cell death can be rescued by addition of non-coding oligonucleotides. Interestingly, the effects of PR dipeptides are to a large extent mimicked by protamine, a sperm-specific Arg-rich protein, and the toxicity of either protamine or PR dipeptides is rescued by the anticoagulant heparin. We propose that the generalized coating of nucleic acids by Arg-rich peptides accounts for the toxicity of C9ORF72 mutations in ALS.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Homo Sapiens (human)

SUBMITTER: Eduardo Zarzuela

LAB HEAD: Javier Muñoz

PROVIDER: PXD014085 | Pride | 2021-04-12

REPOSITORIES: Pride

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Impact of oligoarginine peptides in ribosome composition and chromatin proteomes

Project description:Expanded intronic GGGGCC repeats in C9ORF72 produce several dipeptides, from which the two that contain arginine, (PR)n and (GR)n, accumulate at nucleoli and kill cells. While this toxicity plays an important role in ALS pathogenesis, its mechanism remains unknown. We here show that PR dipeptides bind avidly to DNA and RNA, so that any cellular reaction involving nucleic acids is impaired by the dipeptides. Consistently, PR-induced cell death can be rescued by addition of non-coding oligonucleotides. Interestingly, the effects of PR dipeptides are to a large extent mimicked by protamine, a sperm-specific Arg-rich protein, and the toxicity of either protamine or PR dipeptides is rescued by the anticoagulant heparin. We propose that the generalized coating of nucleic acids by Arg-rich peptides accounts for the toxicity of C9ORF72 mutations in ALS.

2021-04-12 | PXD010555 | Pride

N6-methyladenosine regulates RNA metabolism and neurodegeneration in C9ORF72-ALS/FTD [seq_polyA_RNA-decay]

Project description:N6-methyladenosine (m6A) is the most prevalent internal mRNA modification and regulates RNA metabolism. Repeat expansion in C9ORF72 is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal degeneration (FTD). Here, we showed that m6A is downregulated in C9ORF72-ALS/FTD patient-derived iPSC-differentiated neurons and postmortem brain tissues. The global m6A hypomethylation leads to transcriptome-wide mRNA stabilization and upregulated gene expression, especially ones involved in synaptic activity and neuronal functions. The m6A modification in the C9ORF72 intron sequence preceding the expanded repeats enhances RNA degradation via the nuclear reader YTHDC1. The m6A reduction leads to increased accumulation of repeat RNA and poly-dipeptides. Moreover, the antisense RNA can also be regulated by m6A. Elevating m6A level significantly reduces both sense and antisense repeat RNA and poly-dipeptides, rescues global mRNA homeostasis, and improves survival of C9ORF72-ALS/FTD patient neurons.

2023-06-09 | GSE203579 | GEO

N6-methyladenosine regulates RNA metabolism and neurodegeneration in C9ORF72-ALS/FTD [seq_polyA_RNA-RIP]

2023-06-09 | GSE203578 | GEO

N6-methyladenosine regulates RNA metabolism and neurodegeneration in C9ORF72-ALS/FTD [seq_total_RNA-MeRIP]

2023-06-09 | GSE203580 | GEO

C9ORF72 interaction with cofilin modulates actin dynamics in motoneurons

Project description:Intronic hexanucleotide expansions in C9ORF72 are common in ALS and FTLD, but it is unknown whether loss of function, toxicity by the expanded RNA or dipeptides from non ATG-initiated translation are responsible for the pathophysiology. We determined the interactome of C9ORF72 in motoneurons and found that C9ORF72 is present in a complex with cofilin and other actin binding proteins. Phosphorylation of cofilin is enhanced in C9ORF72 depleted motoneurons, in patient derived lymphoblastoid cells, iPS cell derived motoneurons and post-mortem brain samples from ALS patients. C9ORF72 modulates the activity of the small GTPases Arf6 and Rac1, resulting in enhanced activity of LIMK1/2. This results in reduced axonal actin dynamics in C9ORF72 depleted motoneurons. Dominant negative Arf6 rescues this defect, suggesting that C9ORF72 acts as a modulator of small GTPases in a pathway that regulates axonal actin dynamics.

2016-09-30 | PXD004913 | Pride

C9orf72 BAC Transgenic Mice Display Typical Pathologic Features of ALS/FTD

Project description:Noncoding expansions of a hexanucleotide repeat (GGGGCC) in the C9orf72 gene are the most common cause of familial amyotrophic lateral sclerosis and frontotemporal dementia. Here we report transgenic mice carrying a bacterial artificial chromosome (BAC) containing the full human C9orf72 gene with either a normal allele (15 repeats) or disease-associated expansion (~100â??1,000 repeats; C9-BACexp). C9-BACexp mice displayed pathologic features seen in C9orf72 expansion patients, including widespread RNA foci and repeat-associated non-ATG (RAN) translated dipeptides, which were suppressed by antisense oligonucleotides targeting human C9orf72. Nucleolin distribution was altered, supporting that either C9orf72 transcripts or RAN dipeptides promote nucleolar dysfunction. Despite early and widespread production of RNA foci and RAN dipeptides in C9-BACexp mice, behavioral abnormalities and neurodegeneration were not observed even at advanced ages, supporting the hypothesis that RNA foci and RAN dipeptides occur presymptomatically and are not sufficient to drive neurodegeneration in mice at levels seen in patients. To compare the RNA Seq profiles from the cortex and spinal cord of transgenic mice expressing unexpanded human C9orf72 (F08, n=4), expanded human C9orf72 (F112, n=3/4), and nontransgenic controls (n=4).

2016-02-10 | E-GEOD-77720 | biostudies-arrayexpress

Translation deficits drive C9orf72 associated poly-GR/PR toxicity

Project description:Frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) patients with the C9orf72 mutation show predominantly cytoplasmic aggregates of poly-GR and poly-PR proteins that are acutely toxic in various model systems. To identify the molecular mediators of neurotoxicity of poly-GR/PR, we analyzed their interactomes in primary neurons. GFP-(GR)149 and (PR)175-GFP preferentially interacted with RNA-binding proteins, including stress granule-associated and nucleolar proteins, as well as ribosomes. Overexpression of the poly-GR/PR interactors Staufen 1/2 (STAU1/2) and YBX1 led to cytoplasmic aggregation of poly-GR/PR into large stress granule-like inclusions, while the poly-GR/PR interactor nucleophosmin (NPM1) recruited poly-GR into the nucleolus. In addition, poly-PR expression reduced ribosome levels and translation, which is consistent with the widespread reduction of synaptic proteins detected by proteomics. Surprisingly, only GFP-(GR)53, but not GFP-(GR)149, localized to the nucleolus and reduced ribosome levels and translation in neurons, suggesting impaired ribosome biogenesis is driving the acute toxicity commonly observed in vitro. In C9orf72 patient brains, we detected co-aggregation of poly-GR/PR inclusions with ribosomes, but not stress granules. Partial sequestration of ribosomes may chronically impair protein synthesis and contribute to C9orf72 ALS/FTD pathogenesis.

2018-06-27 | PXD008691 | Pride

C9orf72 BAC Transgenic Mice Display Typical Pathologic Features of ALS/FTD

Project description:Noncoding expansions of a hexanucleotide repeat (GGGGCC) in the C9orf72 gene are the most common cause of familial amyotrophic lateral sclerosis and frontotemporal dementia. Here we report transgenic mice carrying a bacterial artificial chromosome (BAC) containing the full human C9orf72 gene with either a normal allele (15 repeats) or disease-associated expansion (~100–1,000 repeats; C9-BACexp). C9-BACexp mice displayed pathologic features seen in C9orf72 expansion patients, including widespread RNA foci and repeat-associated non-ATG (RAN) translated dipeptides, which were suppressed by antisense oligonucleotides targeting human C9orf72. Nucleolin distribution was altered, supporting that either C9orf72 transcripts or RAN dipeptides promote nucleolar dysfunction. Despite early and widespread production of RNA foci and RAN dipeptides in C9-BACexp mice, behavioral abnormalities and neurodegeneration were not observed even at advanced ages, supporting the hypothesis that RNA foci and RAN dipeptides occur presymptomatically and are not sufficient to drive neurodegeneration in mice at levels seen in patients.

2016-02-10 | GSE77720 | GEO

C9orf72 arginine-rich dipeptide repeat proteins disrupt importin beta-mediated nuclear import

Project description:Disruption of nucleocytoplasmic transport (NCT), including mislocalization of the importin beta cargo, TDP-43, is a hallmark of amyotrophic lateral sclerosis (ALS), including ALS caused by a hexanucleotide repeat expansion in C9orf72. However, the mechanism(s) remain unclear. Importin beta and its cargo adaptors have been shown to co-precipitate with the C9orf72-arginine-containing dipeptide repeat proteins (R-DPRs), poly-glycine arginine (GR) and poly-proline arginine (PR), and are protective in genetic modifier screens. Here, we show that R-DPRs interact with importin beta, disrupt its cargo loading, and inhibit nuclear import in permeabilized mouse neurons and HeLa cells, in a manner that can be rescued by RNA. Although R-DPRs induce widespread protein aggregation in this in vitro system, transport disruption is not due to NCT protein sequestration, nor blockade of the phenylalanine-glycine (FG)-rich nuclear pore complex. Our results support a model in which R-DPRs interfere with nuclear transport receptors in the vicinity of the nuclear envelope.

2020-05-20 | PXD015656 | Pride

p53 is a central regulator driving neurodegeneration caused by C9orf72 poly(PR)

Project description:To analyze the epigenomic landscape of neurodegeneration caused by ALS-associated protein aggregation, we developed a modified version of ATAC-seq that works on primary neurons. We discovered that C9orf72-ALS/FTD associated poly(PR) activated a remarkably specific signature of chromatin accessibility, involving transcriptional targets of the tumor suppressor gene p53. Our findings reveal an unexpected role of p53 as a mediator of neurodegeneration elicited by poly(PR) and provide an example of how ATAC-seq can now be applied to neurons to define mechanisms of neurodegeneration.

2020-12-09 | GSE162048 | GEO

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