Oligomerization and Membrane-Binding Properties of Covalent Adducts Formed by the Interaction of Alpha-Synuclein with the Toxic Dopamine Metabolite 3,4-Dihydroxyphenylacetaldehyde (DOPAL) (original) (raw)
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Journal of Molecular Biology, 2009
The deposition of α-synuclein (α-syn) aggregates in dopaminergic neurons is a key feature of Parkinson's disease. While dopamine (DA) can modulate α-syn aggregation, it is unclear which other factors can regulate the actions of DA on α-syn. In this study, we investigated the effect of solution conditions (buffer, salt and pH) on the oligomerization of α-syn by DA. We show that α-syn oligomerization is dependent on the oxidation of DA into reactive intermediates. Under acidic pH conditions, DA is stable, and DAmediated oligomerization of α-syn is inhibited. From pH 7.0 to pH 11.0, DA is unstable and undergoes redox reactions, promoting the formation of SDSresistant soluble oligomers of α-syn. We show that the reactive intermediate 5,6-dihydroxylindole mediates the formation of α-syn soluble oligomers under physiological conditions (pH 7.4). In contrast, under acidic conditions (pH 4.0), 5,6-dihydroxylindole promotes the formation of SDS-resistant insoluble oligomers that further associate to form sheet-like fibrils with βsheet structure that do not bind the dye thioflavin T. These results suggest that distinct reactive intermediates of DA, and not DA itself, interact with αsyn to generate the α-syn aggregates implicated in Parkinson's disease.
ACS Chemical Neuroscience, 2018
Identifying the mechanisms by which the presynaptic protein α-synuclein (aSyn) is associated to neurodegeneration of dopamine neurons is a major priority in the Parkinson's disease (PD) field. Studies indicate that DOPAL (3,4-dihydroxyphenylacetaldehyde), an aldehyde generated from the enzymatic oxidation of dopamine, may convert aSyn monomer into a neurotoxin via formation of covalently stabilized toxic oligomers. Herein we investigated the role of N-terminal acetylation and familial aSyn mutations (A30P, A53T, E46K, G51D and H50Q) on DOPAL-induced oligomerization of the protein. Our results indicate that wild-type (WT) N-terminally acetylated-aSyn (Ac-aSyn) is less prone to form oligomers upon incubation with DOPAL than the non-Nterminally acetylated protein. On the other hand, familial mutants from Ac-aSyn, particularly A53T, E46K and H50Q increased the formation of DOPAL-derived aSyn oligomers, especially large oligomers. Binding of aSyn to synaptic-like small unilamellar vesicles (SUVs) protected distinctively aSyn variants against the effects of DOPAL. While N-terminal acetylation increased the protective action of against DOPAL-induced aSyn oligomerization, A53T, A30P and H50Q mutations in Ac-aSyn had an opposite effect. It means that PD-linked mutations may not only perturb the affinity of aSyn for membranes but also influence the formation of DOPAL-mediated oligomers. Overall, our findings provide important evidences for the existence of a connection between familial mutations of aSyn, and their distinct affinity to lipid membranes, and the formation of potentially toxic oligomers of the protein mediated by DOPAL.
Dopamine quinones interact with α-synuclein to form unstructured adducts
Biochemical and Biophysical Research Communications, 2010
Oxidative stress Parkinson's disease a b s t r a c t a-Synuclein (asyn) fibril formation is considered a central event in the pathogenesis of Parkinson's disease (PD). In recent years, it has been proposed that prefibrillar annular oligomeric b-sheet-rich species, called protofibrils, rather than fibrils themselves, may be the neurotoxic species. The oxidation products of dopamine (DAQ) can inhibit asyn fibril formation supporting the idea that DAQ might stabilize asyn protofibrils.
DOPAL derived alpha-synuclein oligomers impair synaptic vesicles physiological function
Scientific Reports
Parkinson's disease is a neurodegenerative disorder characterized by the death of dopaminergic neurons and by accumulation of alpha-synuclein (aS) aggregates in the surviving neurons. The dopamine catabolite 3,4-dihydroxyphenylacetaldehyde (DOPAL) is a highly reactive and toxic molecule that leads to aS oligomerization by covalent modifications to lysine residues. Here we show that DOPAL-induced aS oligomer formation in neurons is associated with damage of synaptic vesicles, and with alterations in the synaptic vesicles pools. To investigate the molecular mechanism that leads to synaptic impairment, we first aimed to characterize the biochemical and biophysical properties of the aS-DOPAL oligomers; heterogeneous ensembles of macromolecules able to permeabilise cholesterolcontaining lipid membranes. aS-DOPAL oligomers can induce dopamine leak in an in vitro model of synaptic vesicles and in cellular models. The dopamine released, after conversion to DOPAL in the cytoplasm, could trigger a noxious cycle that further fuels the formation of aS-DOPAL oligomers, inducing neurodegeneration.
Journal of Molecular Neuroscience, 2004
Parkinson's disease (PD) is a neurologic disorder resulting from the loss of dopaminergic neurons in the brain. Two lines of evidence suggest that the protein α-synuclein plays a role in the pathogenesis of PD: Fibrillar α-synuclein is a major component of Lewy bodies in diseased neurons, and two mutations in α-synuclein are linked to early-onset disease. Accordingly, the fibrillization of α-synuclein is proposed to contribute to neurodegeneration in PD. In this report, we provide evidence that oligomeric intermediates of the α-synuclein fibrillization pathway, termed protofibrils, might be neurotoxic. Analyses of protofibrillar α-synuclein by atomic force microscopy and electron microscopy indicate that the oligomers consist of spheres, chains, and rings. α-Synuclein protofibrils permeabilize synthetic vesicles and form pore-like assemblies on the surface of brainderived vesicles. Dopamine reacts with α-synuclein to form a covalent adduct that slows the conversion of protofibrils to fibrils. This finding suggests that cytosolic dopamine in dopaminergic neurons promotes the accumulation of toxic α-synuclein protofibrils, which might explain why these neurons are most vulnerable to degeneration in PD. Finally, we note that aggregation of α-synuclein likely occurs via different mechanisms in the cell versus the test tube. For example, the binding of α-synuclein to cellular membranes might influence its selfassembly. To address this point, we have developed a yeast model that might enable the selection of random α-synuclein mutants with different membrane-binding affinities. These variants might be useful to test whether membrane binding by α-synuclein is necessary for neurodegeneration in transgenic animal models of PD.
The structure of dopamine induced α-synuclein oligomers
European Biophysics Journal With Biophysics Letters, 2010
Inclusions of aggregated α-synuclein (α-syn) in dopaminergic neurons are a characteristic histological marker of Parkinson’s disease (PD). In vitro, α-syn in the presence of dopamine (DA) at physiological pH forms SDS-resistant non-amyloidogenic oligomers. We used a combination of biophysical techniques, including sedimentation velocity analysis, small angle X-ray scattering (SAXS) and circular dichroism spectroscopy to study the characteristics of α-syn oligomers formed in the presence of DA. Our SAXS data show that the trimers formed by the action of DA on α-syn consist of overlapping worm-like monomers, with no end-to-end associations. This lack of structure contrasts with the well-established, extensive β-sheet structure of the amyloid fibril form of the protein and its pre-fibrillar oligomers. We propose on the basis of these and earlier data that oxidation of the four methionine residues at the C- and N-terminal ends of α-syn molecules prevents their end-to-end association and stabilises oligomers formed by cross linking with DA-quinone/DA-melanin, which are formed as a result of the redox process, thus inhibiting formation of the β-sheet structure found in other pre-fibrillar forms of α-syn.
The FASEB Journal, 2005
Dopamine (DA) and α-synuclein (α-SN) are two key molecules associated with Parkinson's disease (PD). We have identified a novel action of DA in the initial phase of α-SN aggregation and demonstrate that DA induces α-SN to form soluble, SDS-resistant oligomers. The DA:α-SN oligomeric species are not amyloidogenic as they do not react with thioflavin T and lack the typical amyloid fibril structures as visualized with electron microscopy. Circular dichroism studies indicate that in the presence of lipid membranes DA interacts with α-SN, causing an alteration to the structure of the protein. Furthermore, DA inhibited the formation of ironinduced α-SN amyloidogenic aggregates, suggesting that DA acts as a dominant modulator of α-SN aggregation. These observations support the paradigm emerging for other neurodegenerative diseases that the toxic species is represented by a soluble oligomer and not the insoluble fibril.
Proceedings of the National Academy of Sciences of the United States of America, 2018
Parkinson's disease (PD) is characterized by a progressive loss of dopaminergic neurons, a process that current therapeutic approaches cannot prevent. In PD, the typical pathological hallmark is the accumulation of intracellular protein inclusions, known as Lewy bodies and Lewy neurites, which are mainly composed of α-synuclein. Here, we exploited a high-throughput screening methodology to identify a small molecule (SynuClean-D) able to inhibit α-synuclein aggregation. SynuClean-D significantly reduces the in vitro aggregation of wild-type α-synuclein and the familiar A30P and H50Q variants in a substoichiometric molar ratio. This compound prevents fibril propagation in protein-misfolding cyclic amplification assays and decreases the number of α-synuclein inclusions in human neuroglioma cells. Computational analysis suggests that SynuClean-D can bind to cavities in mature α-synuclein fibrils and, indeed, it displays a strong fibril disaggregation activity. The treatment with Syn...
In vivo demonstration that -synuclein oligomers are toxic
Proceedings of the National Academy of Sciences, 2011
The aggregation of proteins into oligomers and amyloid fibrils is characteristic of several neurodegenerative diseases, including Parkinson disease (PD). In PD, the process of aggregation of α-synuclein (α-syn) from monomers, via oligomeric intermediates, into amyloid fibrils is considered the disease-causative toxic mechanism. We developed α-syn mutants that promote oligomer or fibril formation and tested the toxicity of these mutants by using a rat lentivirus system to investigate loss of dopaminergic neurons in the substantia nigra. The most severe dopaminergic loss in the substantia nigra is observed in animals with the α-syn variants that form oligomers (i.e., E57K and E35K), whereas the α-syn variants that form fibrils very quickly are less toxic. We show that α-syn oligomers are toxic in vivo and that α-syn oligomers might interact with and potentially disrupt membranes.