Effect of 4-Hydroxy-2-nonenal Modification on α-Synuclein Aggregation

Abstract

Several observations have implicated oxidative stress and aggregation of the presynaptic protein ␣-synuclein in the pathogenesis of Parkinson disease. ␣-Synuclein has been shown to have affinity for unsaturated fatty acids and membranes enriched in polyunsaturated fatty acids, which are especially sensitive to oxidation under conditions of oxidative stress. One of the most important products of lipid oxidation is 4-hydroxy-2-nonenal (HNE), which has been implicated in the pathogenesis of Parkinson disease. Consequently, we investigated the effects of the interaction of HNE with ␣-synuclein. Incubation of HNE with ␣-synuclein at pH 7.4 and 37°C resulted in covalent modification of the protein, with up to six HNE molecules incorporated as Michael addition products. Fourier transform infrared and CD spectra indicated that HNE modification of ␣-synuclein resulted in a major conformational change involving increased ␤-sheet. HNE modification of ␣-synuclein led to inhibition of fibrillation in an HNE concentration-dependent manner. This inhibition of fibrillation was shown to be due to the formation of soluble oligomers based on size exclusion high pressure liquid chromatography and atomic force microscope data. Small angle x-ray scattering analysis indicated that the HNE-induced oligomers were compact and tightly packed. Treatment with guanidinium chloride demonstrated that the HNE-induced oligomers were very stable with an extremely slow rate of dissociation. Addition of 5 M HNE-modified oligomers to primary mesencephalic cultures caused marked neurotoxicity because the integrity of dopaminergic and GABAergic neurons was reduced by 95 and 85%, respectively. Our observations indicate that HNE modification of ␣-synuclein prevents fibrillation but may result in toxic oligomers, which could therefore contribute to the demise of neurons subjected to oxidative damage.

Neuronal nitric oxide synthase phosphorylation induced by docosahexaenoic acid protects dopaminergic neurons in an experimental model of Parkinson’s disease

“…It is known that lipid peroxidation and the 4-HNE level in SN increases in PD [49]. This increase intensifies the activation of caspases 3-8 what leads to apoptosis [50] and formation of a-synuclein aggregates [51]. In this study we found that the injection of MPTP increased nigral 4-HNE amount.…”

Oligomerization and Membrane-binding Properties of Covalent Adducts Formed by the Interaction of α-Synuclein with the Toxic Dopamine Metabolite 3,4-Dihydroxyphenylacetaldehyde (DOPAL)

“…HNE has also been found to induce oligomerization of aS and cause toxicity to dopaminergic neurons in vitro (49). Similar to 4-oxo-2-nonenal and HNE, DOPAL can form covalent adducts with aS via MA and SB reactions (50), which target Lys residues.…”

Structural and Morphological Characterization of Aggregated Species of α-Synuclein Induced by Docosahexaenoic Acid

“…An important issue is to understand whether these chemical modifications are a requirement for the aggregation process. In the presence of lipids and fatty acids, these types of modifications, such as protein oxidations and aliphatic carbonyl adducts formation, have been observed both in vivo and in vitro (18,43,44). They are generated by radicals, hydroperoxides, and successively highly reactive aldehydes, produced by peroxidation of lipids.…”

“…Moreover, in vitro studies have shown that the lipid oxidation product, 4-hydroxy-2-nonenal, covalently binds to ␣-syn. As a consequence, ␣-syn can no longer form fibrils but only oligomeric species, which have been suggested to contribute to the damage of neurons subjected to oxidative stress (18). However, it was found that ␣-syn can act as scavenger of ROS, preventing unsaturated lipids oxidation in vesicles by the oxidation of the methionine residues to methionine-sulfoxide (19).…”