Dataset Information

PolyQ-expanded ataxin-1 formed insoluble protein inclusions perturbing translation in a spinocerebellar ataxia type-1 model

ABSTRACT: Spinocerebellar ataxia type-1 is caused by an abnormally expanded polyglutamine (polyQ) tract in ataxin-1 protein. These expansions are responsible for protein misfolding and self-assembly into intranuclear inclusion bodies (IIBs) that are linked to neuronal death. Here, we describe a nuclear protein aggregation model of pathogenic human ataxin-1. Using an inducible Sleeping Beauty transposon system, we overexpressed ATXN1Q82 gene in human mesenchymal stem cells that are resistant to the early cytotoxic effects of the mutant protein. We characterized the structure and the protein composition of insoluble polyQ IIBs which gradually occupy the nuclei. In response to their formation, our transcriptome analysis reveals a cerebellum-specific perturbed protein interaction network, primarily affecting protein translation. Our study resolves the previously unknown architecture of insoluble polyQ IIBs and suggests that they affect the assembly and the function of the ribosome. Our inducible cell system faithfully models a human cerebellum at the end-stage of the disease.

INSTRUMENT(S): impact II

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Mesenchymal Stem Cell, Stem Cell

SUBMITTER: Kamil Mikulasek

LAB HEAD: Zbynek Zdrahal

PROVIDER: PXD012709 | Pride | 2020-02-18

REPOSITORIES: Pride

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Publications

Nuclear inclusions of pathogenic ataxin-1 induce oxidative stress and perturb the protein synthesis machinery.

Laidou Stamatia S Alanis-Lobato Gregorio G Pribyl Jan J Raskó Tamás T Tichy Boris B Mikulasek Kamil K Tsagiopoulou Maria M Oppelt Jan J Kastrinaki Georgia G Lefaki Maria M Singh Manvendra M Zink Annika A Chondrogianni Niki N Psomopoulos Fotis F Prigione Alessandro A Ivics Zoltán Z Pospisilova Sarka S Skladal Petr P Izsvák Zsuzsanna Z Andrade-Navarro Miguel A MA Petrakis Spyros S

Redox biology 20200211

Spinocerebellar ataxia type-1 (SCA1) is caused by an abnormally expanded polyglutamine (polyQ) tract in ataxin-1. These expansions are responsible for protein misfolding and self-assembly into intranuclear inclusion bodies (IIBs) that are somehow linked to neuronal death. However, owing to lack of a suitable cellular model, the downstream consequences of IIB formation are yet to be resolved. Here, we describe a nuclear protein aggregation model of pathogenic human ataxin-1 and characterize IIB e ...[more]

PMID: 32145456

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Project description:Spinocerebellar Ataxia Type 2 (SCA2) is caused by expansion of a polyglutamine encoding triplet repeat in the human ATXN2 gene beyond (CAG)31. This is thought to mediate toxic gain-of-function by protein aggregation, and affect RNA processing, resulting in degenerative processes affecting preferentially cerebellar neurons. As a faithful animal model, we generated a knock-in mouse replacing the single CAG of murine Atxn2 with CAG42, a frequent patient genotype. This expansion size was inherited stably. The mice showed phenotypes with reduced weight and later motor incoordination. Although brain Atxn2 mRNA became elevated, soluble ATXN2 protein levels diminished over time, which might explain partial loss-of-function effects. Deficits in soluble ATXN2 protein correlated with the appearance of insoluble ATXN2, a progressive feature in cerebellum possibly reflecting toxic gains-of-function. Since in vitro ATXN2 overexpression was known to reduce levels of its protein interactor PABPC1, we studied expansion effects on PABPC1. In cortex, PABPC1 transcript, soluble and insoluble protein levels were increased. In more vulnerable cerebellum the progressive insolubility of PABPC1 was accompanied by decreased soluble protein levels, with PABPC1 mRNA showing no compensatory increase. The sequestration of PABPC1 into insolubility by ATXN2 function gains was validated in human cell culture. To understand consequences on mRNA processing, transcriptome profiles at medium and old age in three different tissues were studied and demonstrated selective induction of Fbxw8 in old cerebellum. Fbxw8 is encoded next to the Atxn2 locus and was shown in vitro to decrease the level of expanded insoluble ATXN2 protein. In conclusion, our data support the concept that expanded ATXN2 undergoes progressive insolubility and affects PABPC1 by a toxic gain-of-function mechanism with tissue-specific effects, which may be partially alleviated by the induction of FBXW8. Factorial design comparing Atxn2 knock-in mice with wild type littermates in three different tissues (brainstem, cerebellum, liver)

Project description:Huntington's disease (HD) is a dominantly inherited genetic disease caused by mutant huntingtin (htt) protein with expanded polyglutamine tracts. A neuropathological hallmark of HD is the presence of neuronal inclusions of mutant htt. p62 is an important regulatory protein in selective autophagy, a process by which aggregated proteins are degraded, and it is associated with several neurodegenerative disorders including HD. Here we investigated the effect of p62 depletion in three HD model mice: R6/2, HD190QG and HD120QG mice. We found that loss of p62 in these models led to longer lifespans and reduced nuclear inclusions, although cytoplasmic inclusions increased with polyglutamine length. In mouse embryonic fibroblasts (MEFs) with or without p62, mutant htt with a nuclear localization signal (NLS) showed no difference in nuclear inclusion between the two MEF types. In the case of mutant htt without NLS, however, p62 depletion increased cytoplasmic inclusions. Furthermore, to examine the effect of impaired autophagy in HD model mice, we crossed R6/2 mice with Atg5 conditional knockout mice. These mice also showed decreased nuclear inclusions and increased cytoplasmic inclusions, similar to HD mice lacking p62. These data suggest that the genetic ablation of p62 in HD model mice enhances cytoplasmic inclusion formation by interrupting autophagic clearance of polyQ inclusions. This reduces polyQ nuclear influx and paradoxically ameliorates disease phenotypes by decreasing toxic nuclear inclusions. Gene expression profiles were analyzed to examine the effects of p62 depletion in mouse with or without mutant huntingtin exon 1 To examine the effect of p62 depletion on the transcriptome of Huntington's disease model mice, we crossed p62 knockout mice with HD model mice. We extracted total RNA from the striatum of these mice at 8 weeks and used for a microaaray analysis. The samples are HD transgenic mice with p62 knockout (HD_p62KO), HD mice with normal p62 (HD_p62WT), non-HD-transgenic mice with p62 knockout (NT_p62KO), and non-HD-transgenic mice with normal p62 (NT_p62WT).

Dataset Information

PolyQ-expanded ataxin-1 formed insoluble protein inclusions perturbing translation in a spinocerebellar ataxia type-1 model

Publications

Nuclear inclusions of pathogenic ataxin-1 induce oxidative stress and perturb the protein synthesis machinery.

Similar Datasets

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