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Mapping of Surface-Exposed Epitopes of In Vitro and In Vivo Aggregated Species of Alpha-Synuclein
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
BioArctic, Stockholm, Sweden.
Univ Tubingen, Hertie Inst Clin Brain Res, Dept Neurodegenerat, Lab Funct Neurogenet, Tubingen, Germany.;German Ctr Neurodegenerat Dis, Tubingen, Germany..
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2017 (English)In: Cellular and molecular neurobiology, ISSN 0272-4340, E-ISSN 1573-6830, Vol. 37, no 7, p. 1217-1226Article in journal (Refereed) Published
Abstract [en]

Aggregated alpha-synuclein is the main component of Lewy bodies, intraneuronal deposits observed in Parkinson's disease and dementia with Lewy bodies. The objective of the study was to identify surface-exposed epitopes of alpha-synuclein in vitro and in vivo formed aggregates. Polyclonal immunoglobulin Y antibodies were raised against short linear peptides of the alpha-synuclein molecule. An epitope in the N-terminal region (1-10) and all C-terminal epitopes (90-140) were found to be exposed in an indirect enzyme-linked immunosorbent assay (ELISA) using recombinant monomeric, oligomeric, and fibrillar alpha-synuclein. In a phospholipid ELISA, the N-terminus and mid-region of alpha-synuclein (i.e., 1-90) were associated with phosphatidylserine and thus occluded from antibody binding. The antibodies that reacted most strongly with epitopes in the in vitro aggregates (i.e., 1-10 and epitopes between positions 90-140) also labeled alpha-synuclein inclusions in brains from transgenic (Thy-1)-h[A30P] alpha-synuclein mice and Lewy bodies and Lewy neurites in brains of patients with alpha-synucleinopathies. However, differences in reactivity were observed with the C-terminal antibodies when brain tissue from human and transgenic mice was compared. Taken together, the study shows that although similar epitopes are exposed in both in vitro and in vivo formed alpha-synuclein inclusions, structural heterogeneity can be observed between different molecular species.

Place, publisher, year, edition, pages
2017. Vol. 37, no 7, p. 1217-1226
Keywords [en]
Parkinson's disease, Dementia with Lewy bodies, Alpha-synuclein, Epitope mapping
National Category
Geriatrics
Identifiers
URN: urn:nbn:se:uu:diva-334384DOI: 10.1007/s10571-016-0454-0ISI: 000409352200007OAI: oai:DiVA.org:uu-334384DiVA, id: diva2:1166773
Available from: 2017-12-15 Created: 2017-12-15 Last updated: 2018-02-23Bibliographically approved
In thesis
1. Characterization of Physiological and Pathological Alpha-Synuclein: Implications for Parkinson’s Disease and Related Disorders
Open this publication in new window or tab >>Characterization of Physiological and Pathological Alpha-Synuclein: Implications for Parkinson’s Disease and Related Disorders
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Aggregated alpha-synuclein is the main component of Lewy bodies and Lewy neurites, intraneuronal inclusions found in the brains of Parkinson’s disease (PD) and dementia with Lewy bodies (DLB) patients (synucleinopathies). Alpha-synuclein is a presynaptic protein, which is most commonly an unfolded monomer in its physiological state. However, under pathological conditions it can start to misfold and enter an aggregation pathway that will lead to the formation of oligomers of increasing size and finally insoluble fibrils. The oligomers have been hypothesized to be the most neurotoxic species, but studies of their properties have been hindered by their heterogeneity and kinetic instability. The overall aim of this thesis was to characterize and compare physiological and pathological forms of alpha-synuclein from different sources: recombinant monomers, oligomers formed in vitro through exposure to oxidative stress related reactive aldehydes, aggregates from a synucleinopathy mouse model and from synucleinopathy patients.

In paper I we studied the effect of low molar excess of two lipid peroxidation products, 4-oxo-2-nonenal (ONE) and 4-hydroxy-2-nonenal (HNE), on the oligomerization of alpha-synuclein. Through biophysical methods we observed that, although both aldehydes bound to alpha-synuclein directly, ONE produced SDS-stable oligomers more rapidly than HNE. Moreover, ONE induced oligomerization at both acidic and neutral pH, while HNE only formed oligomers at neutral pH.

In paper II we mapped the surface exposed epitopes of in vitro and in vivo generated alpha-synuclein species by using immunoglobulin Y antibodies raised against short linear peptides covering most of the alpha-synuclein sequence. Monomers were found to react with most antibodies, while the latter part of the N-terminus and mid-region of HNE oligomers and fibrils was found to be occluded in oligomers and fibrils. Through immunohistochemistry we compared alpha-synuclein aggregates in brain tissue from patients with synucleinopathies as well as from a mouse model expressing A30P human alpha-synuclein. Although the exposed epitopes were found to be similar overall, subtle differences were detected in the C-terminus.

An additional aim of this thesis was to characterize synaptic aggregates of alpha-synuclein. In paper III we obtained synaptosomal preparations of the A30P mouse model and found that a subset of the alpha-synuclein present in the synaptosomes was proteinase K resistant and therefore aggregated. Further biochemical analyses showed that the aggregated alpha-synuclein mainly was of human, i.e. transgenic, origin and that Ser 129 was not phosphorylated, which otherwise is a common post translational modification of alpha-synuclein in Lewy bodies.

It has been suggested that alpha-synuclein plays a role in neurotransmitter release by binding to the SNARE protein VAMP-2 and thereby chaperoning the SNARE complex assembly. In paper IV we used proximity ligation assay to visualize the co-localization of alpha-synuclein and the SNARE proteins in primary neurons from non-transgenic and A30P transgenic mice.

In conclusion, in this thesis we have characterized a variety of alpha-synuclein species and shed light on the diversity of alpha-synuclein aggregates. Additionally, we have characterized synaptic species of alpha-synuclein and analyzed the co-localization between alpha-synuclein and SNARE proteins in neurons.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 65
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1434
Keywords
Alpha-synuclein, Aggregation, Parkinson’s disease, Dementia with Lewy bodies, Oxidative stress, Antibodies, Synapses, SNARE
National Category
Neurosciences Biochemistry and Molecular Biology
Research subject
Molecular Medicine
Identifiers
urn:nbn:se:uu:diva-342761 (URN)978-91-513-0248-5 (ISBN)
Public defence
2018-04-13, Rudbecksalen, Rudbecklaboratoriet, Dag Hammarskjöldsväg 20, Uppsala, 09:15 (English)
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Supervisors
Available from: 2018-03-21 Created: 2018-02-23 Last updated: 2018-04-24

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