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: 4.24). 12/2008; 108(3):578-90. DOI: 10.1111/j.1471-4159.2008.05799.x
Source: PubMed

ABSTRACT 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.

Download full-text


Available from: Phillip Nagley, Dec 06, 2014
  • Source
    • "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"
    [Show abstract] [Hide abstract]
    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 · 4.99 Impact Factor
  • Source
    • "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). "
    [Show abstract] [Hide abstract]
    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 · 4.24 Impact Factor
  • Source
    • "This line of thought is based on results showing that mutant SOD1 was important in neurons for disease initiation and in glia for disease progression in a mouse model of ALS (Boillee et al., 2006). Although the role of protein aggregation in disease pathology has not been clarified, SOD1 aggregates are certainly toxic to the neurons they accumulate in culture (Matsumoto et al., 2005; Soo et al., 2009). It is possible then that protein aggregation and inclusion formation are linked with the initiation event in ALS. "
    [Show abstract] [Hide abstract]
    ABSTRACT: A large body of literature suggests that amyotrophic lateral sclerosis (ALS) pathology is intimately linked with neuroinflammation, specifically activation and recruitment of microglia and astrocytes. The actual cause of gliosis is unclear. Extracellular Cu/Zn superoxide dismutase (SOD1) has recently been shown to activate microglia in a CD14 dependant mechanism providing one potential pathway by which glial cells become activated. As protein inclusions are thought to be an important part of ALS pathology and are associated with all forms of ALS, we sought to determine if aggregated SOD1 would activate microglia. Recombinant SOD1 was aggregated and this, or monomeric forms of SOD1 were then added to EOC.13 microglial cells or primary microglial cells in culture. Although monomeric mutant SOD1 has been shown to promote microglial activation in the past, we found that aggregated SOD1 was able to much more efficiently activate microglia in culture when compared with the unaggregated form of mutant SOD1. In addition to CD14 dependant pathways, aggregated SOD1 also bound to the surface of glial cells and was internalized in a lipid raft and scavenger receptor dependent manner. We have for the first time shown that aggregated mutant SOD1 potently activates microglia. These results suggest that there may be a potential link between protein aggregation and microglial activation in ALS. © 2012 Wiley Periodicals, Inc.
    Glia 03/2013; 61(3). DOI:10.1002/glia.22444 · 6.03 Impact Factor
Show more