Limits...
Autophagy induction reduces mutant ataxin-3 levels and toxicity in a mouse model of spinocerebellar ataxia type 3.

Menzies FM, Huebener J, Renna M, Bonin M, Riess O, Rubinsztein DC - Brain (2009)

Bottom Line: The mutant protein forms intracellular aggregates in the brain.However, the cellular mechanisms causing toxicity are still poorly understood and there are currently no effective treatments.This identified ubiquitin specific peptidase-15, which showed expression changes at both the messenger ribonucleic acid and protein level.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge, UK.

ABSTRACT
Spinocerebellar ataxia type 3 is a neurodegenerative disorder caused by the expansion of the polyglutamine repeat region within the ataxin-3 protein. The mutant protein forms intracellular aggregates in the brain. However, the cellular mechanisms causing toxicity are still poorly understood and there are currently no effective treatments. In this study we show that administration of a rapamycin ester (cell cycle inhibitor-779, temsirolimus) improves motor performance in a transgenic mouse model of spinocerebellar ataxia type 3. Temsirolimus inhibits mammalian target of rapamycin and hence upregulates protein degradation by autophagy. Temsirolimus reduces the number of aggregates seen in the brains of transgenic mice and decreases levels of cytosolic soluble mutant ataxin-3, while endogenous wild-type protein levels remain unaffected. Temsirolimus is designed for long-term use in patients and therefore represents a possible therapeutic strategy for the treatment of spinocerebellar ataxia type 3. Using this disease model and treatment paradigm, we employed a microarray approach to investigate transcriptional changes that might be important in the pathogenesis of spinocerebellar ataxia type 3. This identified ubiquitin specific peptidase-15, which showed expression changes at both the messenger ribonucleic acid and protein level. Ubiquitin specific peptidase-15 levels were also changed in mice expressing another mutant polyglutamine protein, huntingtin. In total we identified 16 transcripts that were decreased in transgenic ataxin-3 mice that were normalized following temsirolimus treatment. In this mouse model with relatively mild disease progression, the number of transcripts changed was low and the magnitude of these changes was small. However, the importance of these transcriptional alterations in the pathogenesis of spinocerebellar ataxia type 3 remains unclear.

Show MeSH

Related in: MedlinePlus

Temsirolimus administration improves rotarod performance in ataxin-3 transgenic mice. (A) Mice expressing mutant ataxin-3 (black line) demonstrate a decreased latency to fall on the accelerating rotarod test compared with non-transgenic littermate controls (grey line). Data shown represent mean values and standard error. P < 0.001 by ANOVA. (B) Mice administered temsirolimus (CCI-779; black line) show an increase in performance on the rotarod over placebo treated control animals (grey line) throughout the period of the study. P < 0.001 by ANOVA. For placebo treated mice n = 17 at each time point. For temsirolimus treated mice n = 17 up to and including 14 weeks, n = 15 at 16 weeks and n = 14 thereafter.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC2801325&req=5

Figure 1: Temsirolimus administration improves rotarod performance in ataxin-3 transgenic mice. (A) Mice expressing mutant ataxin-3 (black line) demonstrate a decreased latency to fall on the accelerating rotarod test compared with non-transgenic littermate controls (grey line). Data shown represent mean values and standard error. P < 0.001 by ANOVA. (B) Mice administered temsirolimus (CCI-779; black line) show an increase in performance on the rotarod over placebo treated control animals (grey line) throughout the period of the study. P < 0.001 by ANOVA. For placebo treated mice n = 17 at each time point. For temsirolimus treated mice n = 17 up to and including 14 weeks, n = 15 at 16 weeks and n = 14 thereafter.

Mentions: Transgenic mice overexpressing full-length human ataxin-3 with an expanded polyglutamine repeat of 70 glutamines have previously been shown to possess a neuropathological phenotype (Bichelmeier et al., 2007). In our laboratory, the mice did not demonstrate as severe a phenotype as previously reported. Transgene expression was not seen to decrease lifespan and no overt cellular phenotype was noted by staining of cerebellum with calbindin or phosphorylated neurofilament antibodies (data not shown), although clear mutant ataxin-3 aggregation was observed (see below). We examined the motor coordination of these mice using rotarod performance. A decreased ability to walk on the rotarod was observed in mice expressing expanded polyglutamine ataxin-3 relative to non-transgenic littermate controls (Fig. 1A). This decrease was most pronounced in young mice as the rotarod performance of wild-type mice declined with age. Rotarod assessment was the only motor phenotype that gave quantifiable readouts in the first 6 months of life; we saw no clear effects with tremor, fore- and hind-limb grip strength, wire manoeuvre or hind limb grasping (data not shown).Figure 1


Autophagy induction reduces mutant ataxin-3 levels and toxicity in a mouse model of spinocerebellar ataxia type 3.

Menzies FM, Huebener J, Renna M, Bonin M, Riess O, Rubinsztein DC - Brain (2009)

Temsirolimus administration improves rotarod performance in ataxin-3 transgenic mice. (A) Mice expressing mutant ataxin-3 (black line) demonstrate a decreased latency to fall on the accelerating rotarod test compared with non-transgenic littermate controls (grey line). Data shown represent mean values and standard error. P < 0.001 by ANOVA. (B) Mice administered temsirolimus (CCI-779; black line) show an increase in performance on the rotarod over placebo treated control animals (grey line) throughout the period of the study. P < 0.001 by ANOVA. For placebo treated mice n = 17 at each time point. For temsirolimus treated mice n = 17 up to and including 14 weeks, n = 15 at 16 weeks and n = 14 thereafter.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2801325&req=5

Figure 1: Temsirolimus administration improves rotarod performance in ataxin-3 transgenic mice. (A) Mice expressing mutant ataxin-3 (black line) demonstrate a decreased latency to fall on the accelerating rotarod test compared with non-transgenic littermate controls (grey line). Data shown represent mean values and standard error. P < 0.001 by ANOVA. (B) Mice administered temsirolimus (CCI-779; black line) show an increase in performance on the rotarod over placebo treated control animals (grey line) throughout the period of the study. P < 0.001 by ANOVA. For placebo treated mice n = 17 at each time point. For temsirolimus treated mice n = 17 up to and including 14 weeks, n = 15 at 16 weeks and n = 14 thereafter.
Mentions: Transgenic mice overexpressing full-length human ataxin-3 with an expanded polyglutamine repeat of 70 glutamines have previously been shown to possess a neuropathological phenotype (Bichelmeier et al., 2007). In our laboratory, the mice did not demonstrate as severe a phenotype as previously reported. Transgene expression was not seen to decrease lifespan and no overt cellular phenotype was noted by staining of cerebellum with calbindin or phosphorylated neurofilament antibodies (data not shown), although clear mutant ataxin-3 aggregation was observed (see below). We examined the motor coordination of these mice using rotarod performance. A decreased ability to walk on the rotarod was observed in mice expressing expanded polyglutamine ataxin-3 relative to non-transgenic littermate controls (Fig. 1A). This decrease was most pronounced in young mice as the rotarod performance of wild-type mice declined with age. Rotarod assessment was the only motor phenotype that gave quantifiable readouts in the first 6 months of life; we saw no clear effects with tremor, fore- and hind-limb grip strength, wire manoeuvre or hind limb grasping (data not shown).Figure 1

Bottom Line: The mutant protein forms intracellular aggregates in the brain.However, the cellular mechanisms causing toxicity are still poorly understood and there are currently no effective treatments.This identified ubiquitin specific peptidase-15, which showed expression changes at both the messenger ribonucleic acid and protein level.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge, UK.

ABSTRACT
Spinocerebellar ataxia type 3 is a neurodegenerative disorder caused by the expansion of the polyglutamine repeat region within the ataxin-3 protein. The mutant protein forms intracellular aggregates in the brain. However, the cellular mechanisms causing toxicity are still poorly understood and there are currently no effective treatments. In this study we show that administration of a rapamycin ester (cell cycle inhibitor-779, temsirolimus) improves motor performance in a transgenic mouse model of spinocerebellar ataxia type 3. Temsirolimus inhibits mammalian target of rapamycin and hence upregulates protein degradation by autophagy. Temsirolimus reduces the number of aggregates seen in the brains of transgenic mice and decreases levels of cytosolic soluble mutant ataxin-3, while endogenous wild-type protein levels remain unaffected. Temsirolimus is designed for long-term use in patients and therefore represents a possible therapeutic strategy for the treatment of spinocerebellar ataxia type 3. Using this disease model and treatment paradigm, we employed a microarray approach to investigate transcriptional changes that might be important in the pathogenesis of spinocerebellar ataxia type 3. This identified ubiquitin specific peptidase-15, which showed expression changes at both the messenger ribonucleic acid and protein level. Ubiquitin specific peptidase-15 levels were also changed in mice expressing another mutant polyglutamine protein, huntingtin. In total we identified 16 transcripts that were decreased in transgenic ataxin-3 mice that were normalized following temsirolimus treatment. In this mouse model with relatively mild disease progression, the number of transcripts changed was low and the magnitude of these changes was small. However, the importance of these transcriptional alterations in the pathogenesis of spinocerebellar ataxia type 3 remains unclear.

Show MeSH
Related in: MedlinePlus