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- Almandoz Gil, Leire, 1988-
(författare)
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Characterization of Physiological and Pathological Alpha-Synuclein : Implications for Parkinson’s Disease and Related Disorders
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 2. |
- Molisak, Agnieszka, et al.
(författare)
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CRISPR/Cas9 as a tool to disrupt wild-type and A53T SNCA in sporadic and familial Parkinson’s disease
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Parkinson’s Disease (PD) is characterized by pathological accumulation of α-synuclein (αSyn) as Lewy bodies and Lewy neurites in the brain. Current treatment strategies can only alleviate the symptoms but do not interfere with the disease progression. With the discovery of the CRISPR/Cas9 gene editing tool, it has become possible to target the generation of pathological protein aggregates at the DNA level. Disrupting the αSyn gene (SNCA) could prevent the formation of Lewy-related pathologies. Here, we have designed two CRISPR/Cas9-based approaches by using guide RNAs (gRNAs) that are targeting either wild-type (WT) SNCA (pan-SNCA) or mutant A53T SNCA that causes early-onset familial PD. We could demonstrate that plasmid vector-mediated transfection of the pan-SNCA gRNA led to robust allelic disruption in HEK293T cells and human fibroblasts and that the editing efficiency was further increased with the use of a lentiviral transduction system. In addition, the SNCA A53T gRNA was specific towards the mutation site, but resulted in low and inconsistent targeting efficiencies in human patient fibroblasts carrying the SNCA A53T mutation. Our results indicate that SNCA can be targeted by CRISPR/Cas9, although the system efficiency varies across different cell types. In the future, systemically administered gene-editing treatments based on CRISPR/Cas9 could provide a valid therapeutic approach for PD patients.
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| 3. |
- Stefanis, Leonidas, et al.
(författare)
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How is alpha-synuclein cleared from the cell?
- 2019
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Ingår i: Journal of Neurochemistry. - : Wiley. - 0022-3042 .- 1471-4159. ; 150:5, s. 577-590
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Forskningsöversikt (refereegranskat)abstract
- The levels and conformers of alpha-synuclein are critical in the pathogenesis of Parkinson's Disease and related synucleinopathies. Homeostatic mechanisms in protein degradation and secretion have been identified as regulators of alpha-synuclein at different stages of its intracellular trafficking and transcellular propagation. Here we review pathways involved in the removal of various forms of alpha-synuclein from both the intracellular and extracellular environment. Proteasomes and lysosomes are likely to play complementary roles in the removal of intracellular alpha-synuclein species, in a manner that depends on alpha-synuclein post-translational modifications. Extracellular alpha-synuclein is cleared by extracellular proteolytic enzymes, or taken up by neighboring cells, especially microglia and astrocytes, and degraded within lysosomes. Exosomes, on the other hand, represent a vehicle for egress of excess burden of the intracellular protein, potentially contributing to the transfer of alpha-synuclein between cells. Dysfunction in any one of these clearance mechanisms, or a combination thereof, may be involved in the initiation or progression of Parkinson's disease, whereas targeting these pathways may offer an opportunity for therapeutic intervention. (Figure presented.).
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