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Proc Natl Acad Sci U S A. 2018 Jul 24;115(30):7813-7818. doi: 10.1073/pnas.1713129115. Epub 2018 Jul 10.

α-Synuclein oligomers induce early axonal dysfunction in human iPSC-based models of synucleinopathies.

Author information

1
Department of Stem Cell Biology, Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany; iryna.prots@uk-erlangen.de.
2
Department of Molecular Neurology, Universitätsklinikum Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany.
3
Department of Stem Cell Biology, Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany.
4
Institute of Biochemistry, Emil-Fischer-Center, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany.
5
Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany.
6
Department of Neurosciences, University of California, San Diego, La Jolla, CA 92093-0948.
7
Department of Psychiatry and Psychotherapy, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany.
8
Division of Neuroscience, National Institute on Aging, National Institutes of Health, Bethesda, MD 20892.
9
Department of Ophthalmology, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany.

Abstract

α-Synuclein (α-Syn) aggregation, proceeding from oligomers to fibrils, is one central hallmark of neurodegeneration in synucleinopathies. α-Syn oligomers are toxic by triggering neurodegenerative processes in in vitro and in vivo models. However, the precise contribution of α-Syn oligomers to neurite pathology in human neurons and the underlying mechanisms remain unclear. Here, we demonstrate the formation of oligomeric α-Syn intermediates and reduced axonal mitochondrial transport in human neurons derived from induced pluripotent stem cells (iPSC) from a Parkinson's disease patient carrying an α-Syn gene duplication. We further show that increased levels of α-Syn oligomers disrupt axonal integrity in human neurons. We apply an α-Syn oligomerization model by expressing α-Syn oligomer-forming mutants (E46K and E57K) and wild-type α-Syn in human iPSC-derived neurons. Pronounced α-Syn oligomerization led to impaired anterograde axonal transport of mitochondria, which can be restored by the inhibition of α-Syn oligomer formation. Furthermore, α-Syn oligomers were associated with a subcellular relocation of transport-regulating proteins Miro1, KLC1, and Tau as well as reduced ATP levels, underlying axonal transport deficits. Consequently, reduced axonal density and structural synaptic degeneration were observed in human neurons in the presence of high levels of α-Syn oligomers. Together, increased dosage of α-Syn resulting in α-Syn oligomerization causes axonal transport disruption and energy deficits, leading to synapse loss in human neurons. This study identifies α-Syn oligomers as the critical species triggering early axonal dysfunction in synucleinopathies.

KEYWORDS:

axonal transport; neurodegeneration; oligomers; synucleinopathies; α-synuclein

PMID:
29991596
PMCID:
PMC6065020
DOI:
10.1073/pnas.1713129115
[Indexed for MEDLINE]
Free PMC Article

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