Direct membrane association drives mitochondrial fission by the Parkinson disease-associated protein alpha-synuclein
ABSTRACT The protein α-synuclein has a central role in Parkinson disease, but the mechanism by which it contributes to neural degeneration remains unknown. We now show that the expression of α-synuclein in mammalian cells, including neurons in vitro and in vivo, causes the fragmentation of mitochondria. The effect is specific for synuclein, with more fragmentation by α- than β- or γ-isoforms, and it is not accompanied by changes in the morphology of other organelles or in mitochondrial membrane potential. However, mitochondrial fragmentation is eventually followed by a decline in respiration and neuronal death. The fragmentation does not require the mitochondrial fission protein Drp1 and involves a direct interaction of synuclein with mitochondrial membranes. In vitro, synuclein fragments artificial membranes containing the mitochondrial lipid cardiolipin, and this effect is specific for the small oligomeric forms of synuclein. α-Synuclein thus exerts a primary and direct effect on the morphology of an organelle long implicated in the pathogenesis of Parkinson disease.
- SourceAvailable from: Nicoletta Plotegher
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- "Moreover , αsyn can translocate to mitochondria and accumulate, causing complex I impairment  . Our results, showing mitochondrial fragmentation, are in agreement with the literature     , excluding Zhu et al. (2012) . Moreover, our data suggest that there is a relationship between the presence of αsyn oligomers in the cytoplasm and variations in mitochondria morphology, while others could only establish a link between αsyn overexpression and mitochondria conditions. "
ABSTRACT: Background Alpha-synuclein oligomerization is associated to Parkinson's disease etiopathogenesis. The study of alpha-synuclein oligomerization properties in live cell and the definition of their effects on cellular viability are among fields expected to provide the knowledge required to unravel the mechanism(s) of toxicity that lead to the disease. Methods We used Number and Brightness method, which is a method based on fluorescence fluctuation analysis, to monitor alpha-synuclein tagged with EGFP aggregation in living SH-SY5Y cells. The presence of alpha-synuclein oligomers detected with this method was associated with intracellular structure conditions, evaluated by fluorescence confocal imaging. Results Cells overexpressing alpha-synuclein-EGFP present a heterogeneous ensemble of oligomers constituted by less than 10 monomers, when the protein approaches a threshold concentration value of about 90 nM in the cell cytoplasm. We show that the oligomeric species are partially sequestered by lysosomes and that the mitochondria morphology is altered in cells presenting oligomers, suggesting that these mitochondria may be dysfunctional. Conclusions We showed that alpha-synuclein overexpression in SH-SY5Y causes the formation of alpha-synuclein oligomeric species, whose presence is associated with mitochondrial fragmentation and autophagic-lysosomal pathway activation in live cells. General significance The unique capability provided by the Number and Brightness analysis to study alpha-synuclein oligomers distribution and properties, and the study their association to intracellular components in single live cells is important to forward our understanding of the molecular mechanisms Parkinson’s disease and it may be of general significance when applied to the study of other aggregating proteins in cellular models.Biochimica et Biophysica Acta (BBA) - General Subjects 06/2014; 1840(6). DOI:10.1016/j.bbagen.2014.02.013 · 3.83 Impact Factor
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- "The knockout of alpha‐synuclein, pink1, parkin and DJ‐1 in drosophila and cell culture based models leads to alterations in mitochondrial morphology and network formation (Clark et al. 2006; Greene et al. 2003; Martin et al. 2006; Nakamura et al. 2011; Park et al. 2005; Park et al. 2009). Mutations in alpha‐synuclein have been shown to cause fragmentation of the mitochondrial network and changes in the ultrastructure and distribution of the mitochondria suggesting increased mitochondrial fission, (Nakamura et al. 2011). Mutations in Pink1 and Parkin have been shown to cause a loss of mitochondrial ultrastructure as observed as changes in the electron density of the mitochondria and fragmentation of the mitochondrial network (Clark et al. 2006; Greene et al. 2003). "
ABSTRACT: As the second most common age related neurodegenerative disease after Alzheimer's disease, the health, social and economic impact resulting from Parkinson's disease will continue to increase alongside the longevity of the population. Ageing remains the biggest risk factor for developing idiopathic Parkinson's disease. Although research into the mechanisms leading to cell death in Parkinson's disease has shed light on many aspects of the pathogenesis of this disorder, we still cannot answer the fundamental question, what specific age related factors predispose some individuals to develop this common neurodegenerative disease. In this review we focus specifically on the neuronal population associated with the motor symptoms of Parkinson's disease, the dopaminergic neurons of the substantia nigra, and try to understand how ageing puts these neurons at risk to the extent that a slight change in protein metabolism or mitochondrial function can push the cells over the edge leading to catastrophic cell death and many of the symptoms seen in Parkinson's disease. We review the evidence that ageing is important for the development of Parkinson's disease and how age related decline leads to the loss of neurons within this disease, before describing exactly how advancing age may lead to substantia nigra neuronal loss and Parkinson's disease in some individuals.Ageing research reviews 02/2014; 14. DOI:10.1016/j.arr.2014.01.004 · 7.63 Impact Factor
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- "As shown in Fig. 6B, a dramatic increase of 255% (normalized by the total homogenate protein content) in GSSG/GSH ratio was found in NH 2 htau-infected cultures in contrast to control ones, further suggesting that their mitochondria were largely defective being source of deleterious ROS. Consistently with obvious ultrastructural changes (Fig. 1A) and in a similar way of other pathogenetic proteins that are also localized to mitochondria in different neurodegenerative human diseases, such as Parkinson's Disease (PD)-associated A53Tα-synuclein (Choubey et al., 2011; Nakamura et al., 2011) and DJ1 (Wang et al., 2012) and ALSlinked mutant SODG93A (Magrané et al., 2012), these results demonstrate that the NH 2 htau fragment impinges on the mitochondrial oxidative capacity and the antioxidant defense in neurons also by affecting the quality control of mitochondria. "
ABSTRACT: Functional as well as structural alterations in mitochondria size, shape and distribution are precipitating, early events in progression of Alzheimer's Disease (AD). We reported that a 20–22 kDa NH2-tau fragment (aka NH2htau), mapping between 26 and 230 amino acids of the longest human tau isoform, is detected in cellular and animal AD models and is neurotoxic in hippocampal neurons. The NH2htau –but not the physiological full-length protein– interacts with Aβ at human AD synapses and cooperates with it in inhibiting the mitochondrial ANT-1-dependent ADP/ATP exchange. Here we show that the NH2htau also adversely affects the interplay between the mitochondria dynamics and their selective autophagic clearance. Fragmentation and perinuclear mislocalization of mitochondria with smaller size and density are early found in dying NH2htau-expressing neurons. The specific effect of NH2htau on quality control of mitochondria is accompanied by (i) net reduction in their mass in correlation with a general Parkin-mediated remodeling of membrane proteome; (ii) their extensive association with LC3 and LAMP1 autophagic markers; (iii) bioenergetic deficits and (iv) in vitro synaptic pathology. These results suggest that NH2htau can compromise the mitochondrial biology thereby contributing to AD synaptic deficits not only by ANT-1 inactivation but also, indirectly, by impairing the quality control mechanism of these organelles.Neurobiology of Disease 02/2014; 62:489–507. DOI:10.1016/j.nbd.2013.10.018 · 5.20 Impact Factor