Defining the native state of α-synuclein

Area of Science:

• Neuroscience
• Molecular Biology
• Biochemistry

Background:

• Misfolding and aggregation of alpha-synuclein (αSyn) are key features of Parkinson's disease.
• The native physiological state of αSyn in healthy cells is not fully understood, with prevailing theories suggesting it exists mainly as an unfolded monomer.

Purpose of the Study:

• To investigate the hypothesis that endogenous αSyn exists in normal cells as a metastable, helically folded tetramer.
• To characterize the oligomeric state of αSyn in intact cells and its relationship to aggregation.

Main Methods:

• In vivo crosslinking to trap αSyn in intact cells.
• Purification of αSyn from normal human brain.
• Development of monoclonal antibodies for αSyn ELISAs.
• Comparison with non-pathogenic homolog β-synuclein.

Main Results:

• In vivo crosslinking confirmed αSyn exists as metastable tetramers and oligomers in the cytosol of both neuronal and non-neural cells.
• These findings were supported by similar oligomeric assemblies observed for β-synuclein.
• αSyn tetramers rapidly dissociate to monomers upon standard cell lysis but are stabilized under conditions of molecular crowding.

Conclusions:

• Endogenous αSyn natively exists as helical tetramers in dynamic equilibrium with unfolded monomers.
• These physiological tetramers are relatively resistant to aggregation, unlike monomers, suggesting a protective role against the formation of pathogenic inclusions.