Structurally distinct α-synuclein fibrils induce robust parkinsonian pathology

Area of Science:

• Neuroscience
• Molecular Biology
• Genetics

Background:

• Alpha-synuclein (α-syn) aggregation into Lewy bodies is central to Parkinson's disease (PD) pathogenesis.
• Genetic mutations in α-syn, such as G51D, are linked to familial forms of PD with severe clinical presentations.
• Despite severe symptoms, in vitro studies suggest the G51D mutation has a low aggregation propensity, posing a mechanistic question.

Purpose of the Study:

• To investigate the mechanisms underlying the severe neurotoxicity associated with the α-syn G51D mutation.
• To elucidate the structural and functional differences between wild-type and G51D α-syn fibrils.
• To evaluate the in vivo propagation and pathological consequences of G51D α-syn fibrils in a murine model.

Main Methods:

• Fourier transform infrared spectroscopy was used for structural analysis of wild-type and G51D α-syn fibrils.
• In vitro assessment of α-syn fibril aggregation in mammalian cells overexpressing α-syn.
• Intranigral injection of G51D α-syn fibrils into a mouse model to study propagation and cellular changes.

Main Results:

• G51D α-syn fibrils demonstrated higher β-sheet content compared to wild-type fibrils.
• Mammalian cells exposed to G51D fibrils showed increased formation of phosphorylated α-syn inclusions.
• Mice injected with G51D fibrils exhibited widespread phosphorylated α-syn pathology, progressive nigral neuronal loss, mitochondrial dysfunction, and motor impairment.

Conclusions:

• Structural differences in G51D α-syn fibrils contribute significantly to their enhanced neurotoxicity.
• The G51D mutation accelerates Parkinson's disease progression and severity through distinct fibril structures.
• This study provides mechanistic insights into G51D mutation-linked Parkinson's disease pathogenesis.