Abstract
Recent studies suggest that brain cell type specific intracellular environments may play important roles in the generation of structurally different protein aggregates that define neurodegenerative diseases. Using human induced pluripotent stem cells (hiPSC) and biochemical and vibrational spectroscopy techniques, we studied whether Parkinson’s disease (PD) patient genomes could modulate alpha-synuclein (aSYN) protein aggregates formation. We found increased β-sheets and aggregated aSYN in PD patient hiPSC-derived midbrain cells, compared to controls. Importantly, we discovered that aSYN protein aggregation is modulated by patient brain cells’ intracellular milieus at the primary nucleation phase. Additionally, we found changes in the formation of aSYN fibrils when employing cellular extracts from familial PD compared to idiopathic PD, in a Thioflavin T-based fluorescence assay. The data suggest that changes in cellular milieu induced by patient genomes trigger structural changes of aSYN potentially leading to the formation of strains having different structures, properties and seeding propensities.
Highlights
Protein aggregation is one of the major cellular hallmarks of neurodegenerative diseases (ND)
We studied changes in intracellular environment of Parkinson’s disease (PD) patients’ brain cells and how they modulate aSYN protein aggregation, using human induced pluripotent stem cells and biochemical methods combined with infrared spectroscopy technique
Our work is the first to demonstrate that changes in intracellular environment induced by patient genomes are important for aSYN aggregation
Summary
Protein aggregation is one of the major cellular hallmarks of neurodegenerative diseases (ND). We found that while the amount of cellular lipids was decreased in PD midbrain spheroids, variation in their oxidation and chain length was dependent on the cells’ genome (Fig. 1e, f ) These data suggested that changes in lipids may fluctuate in different forms of PD, which prompted us to examine the effect of intracellular milieu on aSYN protein aggregation. There was a lower level of ThT-based fluorescence when employing extracts from familial PD hiPSC-derived midbrain spheroids compared to idiopathic PD ones (Fig. 1g) This finding was counterintuitive since previous work showed acceleration in the reaction of recombinant aSYN fibril formation after the addition of purified lipid extracts that are most abundant in PD GBA variant cells [11] or aSYN seeds generated using protein misfolding cyclic amplification [13]
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