Aggregation of α-synuclein underlies Parkinson’s disease (PD), dementia with Lewy bodies (DLB), and related synucleinopathies. The familial E46K substitution is an inherited, highly pathogenic variant that disrupts the E46-K80 salt bridge present in the wild-type, fibril conformation with enhanced amyloid assembly, seeding capacity, and prion-like propagation. Clinically, E46K develop early-onset Parkinsonism with cognitive decline, making this mutation a critical model. In previous studies, numerous polyphenols have been evaluated against wild-type α-synuclein and other amyloid proteins, their effects on familial mutants remain largely unexplored. Here, we investigated the anti-fibrillating properties of malvidin, a dietary anthocyanidin, on the E46K mutant of α-synuclein using a comprehensive suite of biophysical and cellular assays to probe its impact on aggregation, structure, and toxicity. Thioflavin T fluorescence assays revealed concentration-dependent inhibition of fibrillation, with a significant extension of the lag phase and near-complete suppression at a stoichiometric ratio of 1:2. ANS fluorescence assay showed reduced hydrophobic surface exposure, and static light scattering confirmed the formation of smaller size aggregate in the presence of malvidin. Morphological analyses by AFM and TEM demonstrated a shift from canonical amyloid fibrils to predominantly amorphous aggregates and oligomeric species. FTIR spectroscopy deconvoluted data revealed that malvidin induced a shift in secondary structure distribution with reduced β-sheet and slightly increased random coil content. Binding studies based on fluorescence titration and microscale thermophoresis suggested moderate binding of malvidin with monomeric E46K (K a ∼10 6 M −1 ). Functionally, malvidin-derived aggregates modestly improved cell viability relative to untreated E46K fibrils, though viability remained below control. Collectively, these results establish malvidin as a potent modulator of E46K aggregation, providing mechanistic insights into anthocyanidin-based therapeutic strategies for familial synucleinopathies.
Gupta et al. (Sun,) studied this question.