Recruitment of mitochondria into apoptotic signaling correlates with the presence of inclusions formed by amyotrophic lateral sclerosisassociated SOD1 mutations

Department of Biochemistry and Molecular Biology, Monash University, Victoria, Australia.
Journal of Neurochemistry (Impact Factor: 4.28). 12/2008; 108(3):578-90. DOI: 10.1111/j.1471-4159.2008.05799.x
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Mutations in Cu, Zn-superoxide dismutase 1 (SOD1) are associated with degeneration of motor neurons in the disease, familial amyotrophic lateral sclerosis. Intracellular protein inclusions containing mutant SOD1 (mSOD1) are associated with disease but it is unclear whether they are neuroprotective or cytotoxic. We report here that the formation of mSOD1 inclusions in a motor neuron-like cell line (NSC-34) strongly correlates with apoptosis via the mitochondrial death pathway. Applying confocal microscopic analyses, we observed changes in nuclear morphology and activation of caspase 3 specifically in cells expressing mSOD1 A4V or G85R inclusions. Furthermore, markers of mitochondrial apoptosis (activation and recruitment of Bax, and cytochrome c redistribution) were observed in 30% of cells bearing mSOD1 inclusions but not in cells expressing dispersed SOD1. In the presence of additional apoptotic challenges (staurosporine, etoposide, and hydrogen peroxide), cells bearing mSOD1 inclusions were susceptible to further apoptosis suggesting they were in a pro-apoptotic state, thus confirming that inclusions are linked to toxicity. Surprisingly, cells displaying dispersed SOD1 [both wildtype (WT) and mutant] were protected against apoptosis upstream of mitochondrial apoptotic signaling, induced by all agents tested. This protection against apoptosis was unrelated to SOD1 enzymatic activity because the G85R that lacks enzymatic function protected cells similarly to both WT SOD1 and A4V that possesses WT-like activity. These findings demonstrate new aspects of SOD1 in relation to cellular viability; specifically, mSOD1 can be either neuroprotective or cytotoxic depending on its aggregation state.

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Available from: Phillip Nagley, Dec 06, 2014
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    • "Activated caspase 3 , Bax and cytochrome c in cells bearing mutant SOD1 inclusions but not in cells expressing dispersed SOD1 . Soo et al . , 2009 HEK293 , SH - SY5Y SOD1 G93A Mutant SOD1 induces mitochondrial morphological changes and compromises mitochondrial membrane integrity leading to release of cytochrome C only in the presence of Bcl - 2 . Pedrini et al . , 2010 NSC - 34 Tg mice SOD1 G93A Induced Bcl2 - A1 expression via the AP1 transcription factor in motor neuronal cells"
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    ABSTRACT: Amyotrophic lateral sclerosis (ALS) is an adult-onset neurodegenerative disease characterized by the selective death of upper and lower motor neurons which ultimately leads to paralysis and ultimately death. Pathological changes in ALS are closely associated with pronounced and progressive changes in mitochondrial morphology, bioenergetics and calcium homeostasis. Converging evidence suggests that impaired mitochondrial function could be pivotal in the rapid neurodegeneration of this condition. In this review, we provide an update of recent advances in understanding mitochondrial biology in the pathogenesis of ALS and highlight the therapeutic value of pharmacologically targeting mitochondrial biology to slow disease progression.Linked ArticlesThis article is part of a themed issue on Mitochondrial Pharmacology: Energy, Injury & Beyond. To view the other articles in this issue visit
    British Journal of Pharmacology 04/2014; 171(8). DOI:10.1111/bph.12476 · 4.84 Impact Factor
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    • "AMPK activation in NSC-34 cells stably transfected with dismutase active (G37R, G93A) or inactive (A4V, G85R) human SOD1 mutants was compared to NSC-34 cells expressing WT human SOD1. Although transient transfection with these mutants results in protein aggregates, ER stress and cell death [24], [25], [26], these features were not found in these stable cells, which may represent a pre-symptomatic ALS state i.e. SOD1G93A mice at P60. "
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    ABSTRACT: Bioenergetic abnormalities and metabolic dysfunctionoccur in amyotrophic lateral sclerosis (ALS) patients and genetic mouse models. However, whether metabolic dysfunction occurs earlyin ALS pathophysiology linked to different ALS genes remains unclear.Here, we investigatedAMP-activated protein kinase (AMPK) activation, which is a key enzyme induced by energy depletion and metabolic stress, inneuronal cells and mouse models expressing mutantsuperoxide dismutase 1 (SOD1)or TAR DNA binding protein 43 (TDP-43) linked to ALS.AMPKphosphorylation was sharply increased in spinal cords of transgenic SOD1G93A mice at disease onset and accumulated incytoplasmic granules in motor neurons, but not in pre-symptomatic mice. AMPK phosphorylation also occurred in peripheraltissues, liver and kidney, in SOD1G93A mice at disease onset, demonstrating that AMPK activation occurs late and is not restricted to motor neurons. Conversely, AMPK activity was drastically diminished in spinal cords and brains of presymptomatic and symptomatictransgenic TDP-43A315T mice and motor neuronal cells expressing different TDP-43 mutants. We show that mutant TDP-43 induction of the AMPK phosphatase,protein phosphatase 2A (PP2A), is associated with AMPK inactivation in these ALS models. Furthermore, PP2A inhibition by okadaic acid reversed AMPK inactivation by mutant TDP-43 in neuronal cells. Our results suggest that mutant SOD1 and TDP-43 exert contrasting effects on AMPK activation which may reflect key differences in energy metabolism and neurodegeneration in spinal cords of SOD1G93A and TDP-43A315T mice. While AMPK activation in motor neurons correlateswith progressionin mutant SOD1-mediated disease, AMPK inactivation mediated by PP2Ais associated withmutant TDP-43-linked ALS.
    PLoS ONE 03/2014; 9(3):e90449. DOI:10.1371/journal.pone.0090449 · 3.23 Impact Factor
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    • "Similarly, VSVG-ts045 transport was inhibited in two different mSOD1 stable cell lines, and fragmentation of the Golgi was detected in mSOD1 D90A expressing cells (Figure S3), neither of which formed inclusions. These data therefore suggest that small soluble forms of SOD1 inhibit transport, and while linked to apoptosis (Soo et al. 2009), inclusions form after apoptosis has commenced. We demonstrated previously that SOD1 is secreted and that the secretion of mSOD1 is impaired relative to SOD1 WT (Turner et al. 2005). "
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    ABSTRACT: Cu/Zn-superoxide dismutase (SOD1) is misfolded in familial and sporadic Amyotrophic Lateral Sclerosis (ALS), but it is not clear how this triggers endoplasmic reticulum (ER) stress or other pathogenic processes. Here we demonstrate that mutant SOD1 (mSOD1) is predominantly found in the cytoplasm in neuronal cells. Furthermore, we show that mSOD1 inhibits secretory protein transport from the ER to Golgi apparatus. ER-Golgi transport is linked to ER stress, Golgi fragmentation and axonal transport and we also show that inhibition of ER-Golgi trafficking preceded ER stress, Golgi fragmentation, protein aggregation and apoptosis in cells expressing mSOD1. Restoration of ER-Golgi transport by over-expression of coatomer coat protein II (COPII) subunit Sar1 protected against inclusion formation and apoptosis, thus linking dysfunction in ER-Golgi transport to cellular pathology. These findings thus link several cellular events in ALS into a single mechanism occurring early in mSOD1 expressing cells. This article is protected by copyright. All rights reserved.
    Journal of Neurochemistry 10/2013; 129(1). DOI:10.1111/jnc.12493 · 4.28 Impact Factor
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