How epigallocatechin gallate binds and assembles oligomeric forms of human alpha-synuclein

Area of Science:

• Biochemistry
• Neuroscience
• Molecular Biology

Background:

• Alpha-synuclein (αSN) protein aggregation into toxic oligomers is implicated in neurodegenerative diseases.
• (-)-epigallocatechin gallate (EGCG) is known to modulate αSN self-assembly and reduce its toxicity.
• Detailed structural and kinetic insights into the EGCG-αSN interaction are lacking.

Purpose of the Study:

• To investigate the interaction between EGCG and monomeric and oligomeric forms of αSN using liquid-state NMR spectroscopy.
• To characterize the binding sites, affinity, and kinetics of EGCG binding to αSN.
• To understand the mechanism by which EGCG inhibits αSN cytotoxicity.

Main Methods:

• Liquid-state Nuclear Magnetic Resonance (NMR) spectroscopy.
• Analysis of EGCG binding to monomeric and oligomeric αSN.
• Kinetic studies of EGCG-αSN interaction during oligomerization.

Main Results:

• EGCG binds to all regions of monomeric αSN, with highest affinity for the N-terminal region.
• Monomeric αSN binds approximately 54 EGCG molecules during oligomerization, with EGCG dimerization coupled to αSN association.
• Preformed αSN oligomers bind fewer EGCG molecules per protomer (approximately 7) due to their compact structure.
• Low EGCG concentrations (0.36 EGCG per αSN) reduce αSN oligomer toxicity by 50%.

Conclusions:

• EGCG effectively inhibits αSN cytotoxicity at substoichiometric concentrations.
• Synergistic effects between αSN association and EGCG dimerization likely contribute to efficient toxicity inhibition.
• This study provides a structural and kinetic basis for EGCG's neuroprotective potential against αSN-related pathologies.