Optical pulse labeling studies reveal exogenous seeding slows α-synuclein clearance

Area of Science:

• Neuroscience
• Molecular Biology
• Cell Biology

Background:

• Alpha-synuclein (α-syn) aggregation into Lewy bodies (LBs) is linked to neurodegenerative diseases like Parkinson's disease.
• The precise mechanisms connecting α-syn accumulation, cellular dysfunction, and neurodegeneration remain unclear.
• Understanding α-syn dynamics is crucial for developing effective therapeutic strategies.

Purpose of the Study:

• To investigate the clearance and production dynamics of α-syn in a neuronal culture system.
• To determine how α-syn aggregation, specific mutations (A53T), and phosphorylation affect α-syn turnover.
• To explore the impact of exogenous α-syn fibril seeding on α-syn dynamics and cellular responses.

Main Methods:

• Organotypic murine brain slice cultures (BSCs) were transduced with adeno-associated viruses (AAVs) to express Dendra2-tagged human wild-type (WT) and mutant A53T α-syn.
• Cultures were treated with or without exogenous α-syn fibrillar seeds.
• α-syn dynamics were tracked over several weeks using optical pulse labeling and immunofluorescence (p62, Thiazin Red).

Main Results:

• Neurons expressing WT or mutant A53T α-syn exhibited similar turnover rates, irrespective of accumulated insoluble, phosphorylated Ser129 α-syn.
• Neither α-syn aggregation, overexpression, pSer129 modification, nor the A53T mutation altered α-syn dynamics in this model.
• Prion-type seeding with exogenous α-syn fibrils significantly reduced α-syn turnover without causing toxicity, but was associated with increased p62 and Thiazin Red staining.

Conclusions:

• α-syn dynamics in neurons are robust and not significantly impacted by aggregation, phosphorylation, or the A53T mutation in this experimental system.
• Exogenous α-syn fibrils can induce prion-type aggregation, leading to slower α-syn turnover and potentially indicating a protein clearance deficit.
• This brain slice culture model provides a valuable platform for long-term studies of α-syn dynamics and for investigating therapeutic interventions.