Ändra sökning
RefereraExporteraLänk till posten
Permanent länk

Direktlänk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Differential degradation of full-length and cleaved ataxin-7 fragments in a novel stable inducible SCA7 model
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för neurokemi.ORCID-id: 0000-0001-9834-4554
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för neurokemi.ORCID-id: 0000-0001-9064-5432
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för neurokemi.
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för neurokemi.ORCID-id: 0000-0002-8630-2127
2012 (Engelska)Ingår i: Journal of Molecular Neuroscience, ISSN 0895-8696, E-ISSN 1559-1166, Vol. 47, nr 2, s. 219-233Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Spinocerebellar ataxia type 7 (SCA7) is one of nine neurodegenerative disorders caused by expanded polyglutamine repeats, and a common toxic gain-of-function mechanism has been proposed. Proteolytic cleavage of several polyglutamine proteins has been identified and suggested to modulate the polyglutamine toxicity. In this study, we show that full-length and cleaved fragments of the SCA7 disease protein ataxin-7 (ATXN7) are differentially degraded. We found that the ubiquitin-proteosome system (UPS) was essential for the degradation of full-length endogenous ATXN7 or transgenic full-length ATXN7 with a normal or expanded glutamine repeat in both HEK 293T and stable PC12 cells. However, a similar contribution by UPS and autophagy was found for the degradation of proteolytically cleaved ATXN7 fragments. Furthermore, in our novel stable inducible PC12 model, induction of mutant ATXN7 expression resulted in toxicity and this toxicity was worsened by inhibition of either UPS or autophagy. In contrast, pharmacological activation of autophagy could ameliorate the ATXN7-induced toxicity. Based on our findings, we propose that both UPS and autophagy are important for the reduction of mutant ataxin-7-induced toxicity, and enhancing ATXN7 clearance through autophagy could be used as a potential therapeutic strategy in SCA7.

Ort, förlag, år, upplaga, sidor
2012. Vol. 47, nr 2, s. 219-233
Nyckelord [en]
Aggregation, Ataxin-7, Autophagy, Polyglutamine, Proteasome, SCA7
Nationell ämneskategori
Biologiska vetenskaper Kemi
Forskningsämne
neurokemi med molekylär neurobiologi
Identifikatorer
URN: urn:nbn:se:su:diva-64160DOI: 10.1007/s12031-012-9722-8ISI: 000304567700002OAI: oai:DiVA.org:su-64160DiVA, id: diva2:455938
Forskningsfinansiär
Vetenskapsrådet, K2010-68X-21449-01-3
Anmärkning

AuthorCount: 4;

Tillgänglig från: 2011-11-11 Skapad: 2011-11-11 Senast uppdaterad: 2017-12-08Bibliografiskt granskad
Ingår i avhandling
1. STUDIES OF FACTORS AFFECTING INTRACELLULAR TOXICITY OF THE SCA7 DISEASE PROTEIN ATAXIN - 7: FOCUS ON ATAXIN-7 DEGRADATION AND OXIDATIVE STRESS
Öppna denna publikation i ny flik eller fönster >>STUDIES OF FACTORS AFFECTING INTRACELLULAR TOXICITY OF THE SCA7 DISEASE PROTEIN ATAXIN - 7: FOCUS ON ATAXIN-7 DEGRADATION AND OXIDATIVE STRESS
2011 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Spinocerebellar ataxia type 7 (SCA7) is one of nine neurodegenerative disorders caused by expansion of CAG/polyglutamine repeats. Proteins carrying expanded polyglutamine (polyQ) domains are suggested to be resistant to degradation and aggregate. Furthermore, a negative correlation between aggregation and toxicity has been shown. So far, little is known about the turn-over rate and degradation of the SCA7 disease protein ataxin-7 (ATXN7) and how this protein induces cellular toxicity. For the studies in this thesis work, we constructed stable inducible PC12 cell lines expressing GFP-tagged ATXN7 with 10 or 65 glutamines (Qs). Using these cell lines, we studied the turn-over of ATXN7 and the relationship between mutant ATXN7 and oxidative stress.

We showed that ATXN7 with a normal glutamine repeat (ATXN7Q10-GFP) has a short half-life and is mainly degraded by the UPS. In cells expressing expanded ATXN7 (ATXN7Q65-GFP), aggregation and reduced viability was observed. The aggregation increased the half-life of mutant ATXN7. For expanded full-length ATXN7, UPS was still the main degradation pathway; however autophagy also played a role in clearance of soluble ATXN7 fragments and possibly in aggregated ATXN7 material. Moreover, activation of autophagy reduced the level of aggregation and ameliorated the toxicity in cells expressing mutant ATXN7. From this study, we could get the conclusion that although expansion of the polyQ repeat increases the stability of expanded ATXN7, the protein can still be degraded via both UPS and autophagy. Furthermore, stimulation of autophagy could ameliorate the expanded ATXN7 toxicity and could therefore be a potential therapeutic approach for SCA7.

Regarding the role of oxidative stress we showed that expression of mutant ATXN7 leads to increased ROS levels and oxidative stress. Treatment with an antioxidant or blockage of NADPH oxidase complexes (NOX) decreased ATXN7 aggregation, the levels of ROS and ameliorated ATXN7 induced toxicity. Based on these results, we suggest that mutant ATXN7 cause increased ROS production from NOX and antioxidants treatment and or inhibition of NADPH-oxidase might potentially be used as a therapeutic strategy in SCA7.

Ort, förlag, år, upplaga, sidor
Stockholm: Department of Neurochemistry, Stockholm University, 2011. s. 37
Nyckelord
Polyglutamine, SCA7, UPS, Autophagy
Nationell ämneskategori
Biologiska vetenskaper Kemi
Forskningsämne
neurokemi med molekylär neurobiologi
Identifikatorer
urn:nbn:se:su:diva-64167 (URN)978-91-7447-410-7 (ISBN)
Presentation
2011-12-09, Heilbronnsalen, Svante Arrhenius väg 21 A, Stockholm, 13:00 (Engelska)
Opponent
Handledare
Anmärkning

At the time of defence the following paper was unpublished and had a status as follows: Paper 2: Manuscript

Tillgänglig från: 2011-11-11 Skapad: 2011-11-11 Senast uppdaterad: 2015-03-16Bibliografiskt granskad
2. Molecular mechanism(s) underlying neurodegeneration in SCA7 disease: Role of NOX enzymes and oxidative stress
Öppna denna publikation i ny flik eller fönster >>Molecular mechanism(s) underlying neurodegeneration in SCA7 disease: Role of NOX enzymes and oxidative stress
2015 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Spinocerebellar ataxia type 7 (SCA7) is an autosomal dominant neurodegenerative disorder caused by a CAG trinucleotide expansion in the SCA7 gene resulting in progressive ataxia and retinal dystrophy. SCA7 belongs to a group of neurodegenerative disorders called polyglutamine (polyQ) diseases, that share the common feature of glutamine tract expansions within otherwise unrelated proteins. Common suggested mechanisms by which polyQ expanded proteins induce toxicity include aggregation and induction of oxidative stress. 

In this work we examined the connection between oxidative stress, aggregation and toxicity in SCA7 disease. We show that expression of the SCA7 disease protein, ataxin-7 (ATXN7), results in elevated levels of ROS and oxidative stress which in turn lead to toxicity. Our results also revealed that the oxidative stress further contributes to mutant ATXN7 aggregation. Moreover, we show, for the first time, that the major source of the elevated ROS in mutant ATXN7 cells is the increased activation of NOX1 enzymes. Interestingly, our results further revealed that the increased level of NOX1 activity together with altered p53 function leads to a metabolic shift in mutant ATXN7 expressing cells. Treatments with antioxidants, a NOX1 specific inhibitor or NOX1 knock-down, all decreased the ROS level, restored the metabolic shift and ameliorated the mutant ATXN7 induced toxicity. Taken together, we conclude that mutant ATXN7 activate NOX1 enzymes which results in oxidative stress, increased mutant ATXN7 aggregation, metabolic dysfunction and toxicity. NOX1 specific inhibition could thus be a potential therapeutic strategy for SCA7.

Ort, förlag, år, upplaga, sidor
Stockholm: Department of Neurochemistry, Stockholm University, 2015. s. 56
Nyckelord
neurodegeneration, oxidative stress, NOX, metabolism, p53
Nationell ämneskategori
Kemi
Forskningsämne
neurokemi med molekylär neurobiologi
Identifikatorer
urn:nbn:se:su:diva-119846 (URN)978-91-7649-257-4 (ISBN)
Disputation
2015-10-16, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 09:00 (Engelska)
Opponent
Handledare
Anmärkning

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.

Tillgänglig från: 2015-09-24 Skapad: 2015-08-26 Senast uppdaterad: 2019-11-01Bibliografiskt granskad
3. Studies of polyglutamine expanded Ataxin-7 toxicity
Öppna denna publikation i ny flik eller fönster >>Studies of polyglutamine expanded Ataxin-7 toxicity
2015 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Spinocerebellar ataxia type 7 (SCA7) is an autosomal dominant inherited neurodegenerative disease for which there is no cure. SCA7 belongs to the group of polyglutamine disorders, which are all caused by the expansion of a polyglutamine tract in different disease proteins. Common toxic mechanisms have been proposed for polyglutamine diseases; however the exact pathological mechanism(s) are still unclear.

The aim of this thesis was to identify and characterize the molecular mechanisms by which polyglutamine expansion in the ATXN7 protein cause SCA7 and how this can be counteracted. We found that mutant ATXN7 can be degraded by the ubiquitin proteasome system (UPS) and autophagy, the two main cellular degradation pathways. However aggregation stabilized the protein against degradation. Moreover, we found that mutant ATXN7 blocked the induction of autophagy by interfering with p53 and the ULK1-ATG13-FIP200 complex. Pharmacological stimulation of autophagy ameliorated aggregation, as well as toxicity.

We also found that oxidative stress plays an important role in mutant ATXN7 toxicity and that the oxidative stress is generated by activation of NADPH oxidase 1 (NOX1) complexes. Furthermore, we showed that the increased NOX1 activity, together with polyQ expanded ATXN7 mediated disruption of the transcription factor p53, results in metabolic alterations in SCA7 cells. The expression of key p53 regulated metabolic proteins like AIF, TIGAR and GLUT1 was altered in SCA7 cells and resulted in reduced mitochondrial respiration, a higher dependence on glycolysis and reduced ATP levels.

In summary, our data indicate that mutant ATXN7 mediated dysregulation of p53, resulting in autophagic and metabolic alterations, could play a key role in SCA7 and possibly other polyglutamine diseases.

Ort, förlag, år, upplaga, sidor
Stockholm: Department of Neurochemistry, Stockholm University, 2015. s. 74
Nyckelord
neurodegeneration, SCA7, protein degradation, aggregation, p53, oxidative stress, NOX
Nationell ämneskategori
Biokemi och molekylärbiologi
Forskningsämne
neurokemi med molekylär neurobiologi
Identifikatorer
urn:nbn:se:su:diva-121116 (URN)978-91-7649-249-9 (ISBN)
Disputation
2015-11-13, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 09:30 (Engelska)
Opponent
Handledare
Tillgänglig från: 2015-10-22 Skapad: 2015-09-24 Senast uppdaterad: 2020-02-27Bibliografiskt granskad

Open Access i DiVA

Fulltext(931 kB)224 nedladdningar
Filinformation
Filnamn FULLTEXT03.pdfFilstorlek 931 kBChecksumma SHA-512
0dadf51cbc2e95b719bd90cbb50765144a24afdf0cd738d4e595cf1fa46a136cd4512694f34fab28d039ea19cb33757d01d4b8e7dbbd61a22419cccfe65afc4a
Typ fulltextMimetyp application/pdf

Övriga länkar

Förlagets fulltext

Sök vidare i DiVA

Av författaren/redaktören
Yu, XinAjayi, AbiodunStröm, Anna-Lena
Av organisationen
Institutionen för neurokemi
I samma tidskrift
Journal of Molecular Neuroscience
Biologiska vetenskaperKemi

Sök vidare utanför DiVA

GoogleGoogle Scholar
Totalt: 224 nedladdningar
Antalet nedladdningar är summan av nedladdningar för alla fulltexter. Det kan inkludera t.ex tidigare versioner som nu inte längre är tillgängliga.

doi
urn-nbn

Altmetricpoäng

doi
urn-nbn
Totalt: 161 träffar
RefereraExporteraLänk till posten
Permanent länk

Direktlänk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf