Change in the Oligomeric State of α-Synuclein Variants in Living Cells

Influence of Cigarette Aerosol in Alpha-Synuclein Oligomerization and Cell Viability in SH-SY5Y: Implications for Parkinson's Disease

Although cigarette aerosol exposure is associated with various adverse health issues, its impact on Parkinson's disease (PD) remains elusive. Here, we investigated the effect of cigarette aerosol extract (CAE) on SH-SY5Y cells for the first time, both with and without α-synuclein (α-Syn) overexpression. We found that α-Syn aggravates CAE-induced cell death, oxidative stress, and mitochondrial dysfunction. Fluorescence cross-correlation spectroscopy (FCCS) revealed a dual distribution of α-Syn within the cells, with homogeneous regions indicative of monomeric α-Syn and punctated regions, suggesting the formation of oligomers. Moreover, we observed colocalization of α-Syn oligomers with lysosomes along with a reduction in autophagy activity. These findings suggest that α-Syn overexpression exacerbates CAE-induced intracellular cytotoxicity, mitochondrial dysfunction, and autophagy dysregulation, leading to elevated cell mortality. Our findings provide new insights into the pathogenic mechanisms linking exposure to cigarette aerosols with neurodegenerative diseases.

Fibrillation of α-synuclein triggered by bacterial endotoxin and lipid vesicles is modulated by N-terminal acetylation and familial Parkinson's disease mutations

It has been hypothesized that --Parkinson's disease (PD) may be initiated in the gastrointestinal tract, before manifesting in the central nervous system. In this respect, it was demonstrated that lipopolysaccharide (LPS), an endotoxin from gram-negative bacteria, accelerates the in vitro formation of α-synuclein (aSyn) fibrils, whose intracellular deposits is a histological hallmark of the degeneration of dopaminergic neurons in PD. Herein, N-terminal acetylation and missense mutations of aSyn (A30P, A53T, E46K, H50Q and G51D) linked to rare, early-onset forms of familial PD were investigated regarding their effect on aSyn aggregation stimulated by either LPS or small unilamellar lipid vesicles (SUVs). Our findings indicated that LPS as well as SUVs induce the fibrillation of N-terminally acetylated wild-type aSyn (Ac-aSyn-WT) more remarkably than the non-acetylated protein, while the LPS-free protein alone did not undergo fibrillation under our assay conditions. In addition, with the exception of A30P, PD mutations increased the fibrillation of Ac-aSyn in the presence of LPS compared with Ac-aSyn-WT. The most pronounced effect of LPS was noticed for A53T, as observed when either Thioflavin-T or JC-1 were used as fluorescent probes for fibrils. Overall, our results suggest for the first time the existence of a synergy between LPS and PD mutations/N-terminal acetylation toward aSyn fibrillation.