Human A53T α-Synuclein Causes Reversible Deficits in Mitochondrial Function and Dynamics in Primary Mouse Cortical Neurons

PLOS ONE, Dec 2019

Parkinson’s disease (PD) is the second most common neurodegenerative disease. A key pathological feature of PD is Lewy bodies, of which the major protein component is α-synuclein (α-syn). Human genetic studies have shown that mutations (A53T, A30P, E46K) and multiplication of the α-syn gene are linked to familial PD. Mice overexpressing the human A53T mutant α-syn gene develop severe movement disorders. However, the molecular mechanisms of α-syn toxicity are not well understood. Recently, mitochondrial dysfunction has been linked with multiple neurodegenerative diseases including Parkinson’s disease. Here we investigated whether mitochondrial motility, dynamics and respiratory function are affected in primary neurons from a mouse model expressing the human A53T mutation. We found that mitochondrial motility was selectively inhibited in A53T neurons while transport of other organelles was not affected. In addition, A53T expressing neurons showed impairment in mitochondrial membrane potential and mitochondrial respiratory function. Furthermore, we found that rapamycin, an autophagy inducer, rescued the decreased mitochondrial mobility. Taken together, these data demonstrate that A53T α-syn impairs mitochondrial function and dynamics and the deficit of mitochondrial transport is reversible, providing further understanding of the disease pathogenesis and a potential therapeutic strategy for PD.

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Human A53T α-Synuclein Causes Reversible Deficits in Mitochondrial Function and Dynamics in Primary Mouse Cortical Neurons

et al. (2013) Human A53T -Synuclein Causes Reversible Deficits in Mitochondrial Function and Dynamics in Primary Mouse Cortical Neurons. PLoS ONE 8(12): e85815. doi:10.1371/journal.pone.0085815 Human A53T -Synuclein Causes Reversible Deficits in Mitochondrial Function and Dynamics in Primary Mouse Cortical Neurons Li Li 0 Sashi Nadanaciva 0 Zdenek Berger 0 Wei Shen 0 Katrina Paumier 0 Joel Schwartz 0 Kewa Mou 0 Paula Loos 0 Anthony J. Milici 0 John Dunlop 0 Warren D. Hirst 0 Charleen T Chu, University of Pittsburgh, United States of America 0 1 Neuroscience Research Unit, Pfizer, Inc., Cambridge, Massachusetts, United States of America, 2 Compound Safety Prediction Group, Pfizer, Inc. , Groton, Connecticut , United States of America Parkinson's disease (PD) is the second most common neurodegenerative disease. A key pathological feature of PD is Lewy bodies, of which the major protein component is -synuclein (-syn). Human genetic studies have shown that mutations (A53T, A30P, E46K) and multiplication of the -syn gene are linked to familial PD. Mice overexpressing the human A53T mutant -syn gene develop severe movement disorders. However, the molecular mechanisms of syn toxicity are not well understood. Recently, mitochondrial dysfunction has been linked with multiple neurodegenerative diseases including Parkinson's disease. Here we investigated whether mitochondrial motility, dynamics and respiratory function are affected in primary neurons from a mouse model expressing the human A53T mutation. We found that mitochondrial motility was selectively inhibited in A53T neurons while transport of other organelles was not affected. In addition, A53T expressing neurons showed impairment in mitochondrial membrane potential and mitochondrial respiratory function. Furthermore, we found that rapamycin, an autophagy inducer, rescued the decreased mitochondrial mobility. Taken together, these data demonstrate that A53T -syn impairs mitochondrial function and dynamics and the deficit of mitochondrial transport is reversible, providing further understanding of the disease pathogenesis and a potential therapeutic strategy for PD. - Competing interests: All authors are employed by Pfizer Inc. and hold stock in Pfizer Inc. However, this does not alter the authors' adherence to all the PLOS ONE policies on sharing data and materials. Parkinsons disease (PD) is the second most common neurodegenerative disease, affecting 1% of the population older than 60 and up to 3% of people older than 85 years [1]. This movement disorder is characterized by resting tremor, rigidity, postural reflex impairment and bradykinesia. Molecular mechanisms of the disease are still unclear. However, previous studies have shown that both environmental and genetic factors play a causal role in PD [2-5]. -synuclein (-syn) is the major protein component of Lewy bodies, the pathological hallmark of PD [6]. Human genetic studies have shown that mutations within the -synuclein gene, A53T, A30P, E46K, and multiplications of this gene are linked to familial PD [7]. More recently, genome-wide association (GWAS) studies have also demonstrated that SNCA, which encodes -syn, is linked to sporadic PD [8]. -syn is an abundant 140-residue protein, which is primarily found in neural tissues including the cortex, hippocampus, substantia nigra, thalamus, cerebellum and spinal cord [9]. It is localized in the cytosol, nucleus and mitochondria and is enriched presynaptically. Increased expression of -syn can drive its aggregation, and A53T -syn has increased propensity to oligomerize [10] and aggregate into fibrillar forms [11,12]. Mice expressing A53T -syn develop severe motor deficits leading to paralysis and death [13]. These animals also develop agedependent -syn inclusions that recapitulate the pathology seen in human PD patients. Although -syn plays a critical role in the pathogenesis of PD the underlying molecular mechanisms of -syn toxicity are still unclear. Mitochondrial dysfunction has been linked with multiple neurodegenerative diseases including PD [14,15]. Recent reports have shown that -syn exists in mitochondria and can affect mitochondrial function [16,17]. For example, overexpression of A53T -syn was shown to inhibit Complex I activity in the dopaminergic neurons of transgenic mice [18], depolarize mitochondrial membrane potential and increase reactive oxygen species in human neuroblastoma cells [19], and induce mitochondrial autophagy in neurons expressing the A53T mutation [18,20]. In addition, it was recently shown that -syn affects mitochondrial motility [21]. In the current study, we investigated whether the human A53T -syn mutation expressed in primary cortical neurons from mice affects mitochondrial transport, membrane potential and respiratory function and found that all these parameters were impaired in the presence of the mutant -syn. We also investigated whether the defective mitochondrial phenotype is reversible and demonstrated that (...truncated)


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Li Li, Sashi Nadanaciva, Zdenek Berger, Wei Shen, Katrina Paumier, Joel Schwartz, Kewa Mou, Paula Loos, Anthony J. Milici, John Dunlop, Warren D. Hirst. Human A53T α-Synuclein Causes Reversible Deficits in Mitochondrial Function and Dynamics in Primary Mouse Cortical Neurons, PLOS ONE, 2013, 12, DOI: 10.1371/journal.pone.0085815