Toxic Metamorphosis-How Changes from Lysosomal to Cytosolic pH Modify the Alpha-Synuclein Aggregation Pattern
Bisher Eymsh1,2, Alice Drobny1, Timon R Heyn3
1Institute of Biochemistry, Kiel University, 24118 Kiel, Germany.
Biomacromolecules
|September 28, 2020
Summary
Alpha-synuclein (aSyn) aggregation differs significantly between neutral and acidic pH. Acidic conditions promote faster, distinct aSyn assembly, impacting protein stability and cellular toxicity.
Area of Science:
- Biochemistry
- Neuroscience
- Cell Biology
Background:
- Alpha-synuclein (aSyn) is a protein linked to neurodegenerative diseases like Parkinson's.
- aSyn exists in various forms (monomers, oligomers, fibrils) influenced by cellular environment.
- Under physiological conditions, aSyn is mainly in neuronal cytosol and synapses but also in lysosomes for degradation.
Purpose of the Study:
- To compare the aggregation speed, morphology, folding, and spreading of aSyn at cytosolic (pH 7.4) and lysosomal (pH 5) conditions.
- To investigate the seeding potential of lysosomal aSyn.
- To analyze the stability and structural changes of aSyn aggregates formed at acidic pH when exposed to neutral pH.
Main Methods:
- Thioflavin T fluorescence assay for aggregation kinetics.
- Transmission electron microscopy (TEM) for morphology.
- Circular dichroism (CD) and Fourier transform infrared spectroscopy (FTIR) for folding state.
- In vitro aggregation assays using purified aSyn and cell-derived aSyn.
Main Results:
- Substantial differences observed in aSyn aggregation between neutral and acidic pH.
- Lysosomal aSyn from cell lines demonstrated concentration-dependent seeding capability.
- aSyn aggregates formed at pH 5 were unstable at pH 7.4, collapsing into soluble forms with altered structures.
Conclusions:
- Cellular pH significantly influences alpha-synuclein aggregation pathways and kinetics.
- Lysosomal aSyn can actively seed further aggregation.
- The instability of acidic aSyn aggregates at neutral pH has implications for understanding intracellular toxicity and developing characterization methods.
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