Copper homeostasis is critical to the functioning of the brain and its breakdown links to many brain diseases. Copper
is also known to interact with the negatively charged lipid, phosphatidylserine (PS), as well as α-synuclein, an aggregation-prone
protein enriched in the synapse which plays a role in synaptic vesicle docking and fusion. However, the interplay between copper,
PS lipid and α-synuclein is not known. Herein, we report a detailed and predominantly kinetic study of the interactions among these
three components pertinent to copper homeostasis and neurotransmission. We found that synaptic vesicle mimic small unilamellar
vesicles (SUVs) can sequester any excess free Cu2+ within milliseconds and bound Cu2+ on SUVs can be reduced to Cu+ by GSH at
a nearly constant rate under physiological conditions. Moreover, we revealed that SUV-bound Cu2+ does not affect the binding be tween wild-type α-synuclein and SUVs but affect that between N-terminal acetylated α-synuclein and SUVs. In contrast, Cu2+ can
effectively displace both types of α-synuclein from the vesicles. Our results suggest that synaptic vesicles may mediate copper transfer
in the brain while copper could participate in synaptic vesicle docking to the plasma membrane via its regulation of the interaction
between α-synuclein and synaptic vesicle.