Nonaggregated α-synuclein influences SNARE-dependent vesicle docking via membrane binding

Area of Science:

• Neuroscience
• Biochemistry
• Molecular Biology

Background:

• Alpha-synuclein (α-Syn) is a key component of Lewy bodies, characteristic of Parkinson's disease (PD).
• While α-Syn overexpression reduces neurotransmitter release, the precise inhibitory mechanism remains unclear.
• Understanding α-Syn's role in neuroexocytosis is crucial for PD pathogenesis research.

Purpose of the Study:

• To investigate the effect of nonaggregated α-Syn on SNARE-dependent liposome fusion.
• To elucidate the mechanism by which α-Syn inhibits neurotransmitter release.
• To differentiate the effects of α-Syn on vesicle docking versus fusion.

Main Methods:

• Utilized ensemble in vitro fluorescence assays to measure lipid mixing mediated by SNAREs.
• Employed advanced single-vesicle assays to distinguish between vesicle docking and fusion events.
• Investigated the role of α-Syn binding to acidic lipids in membrane fusion inhibition.

Main Results:

• Nonaggregated α-Syn significantly reduces SNARE-mediated lipid mixing in vitro.
• Single-vesicle assays revealed that α-Syn specifically inhibits vesicle docking, not the fusion process itself.
• Inhibition of docking by α-Syn necessitates its binding to acidic lipid-containing membranes.

Conclusions:

• Nonaggregated α-Syn inhibits SNARE-dependent membrane fusion primarily by blocking vesicle docking.
• This inhibitory mechanism is dependent on α-Syn's interaction with acidic lipids on the target membrane.
• Suggests distinct mechanisms of α-Syn inhibition of membrane fusion at different concentrations and oligomeric states.