α-Synuclein emerges as a potent regulator of VDAC-facilitated calcium transport
When the Parkinsons disease (PD) related neuronal protein, alpha-synuclein (Syn), is added to the reconstituted mitochondrial voltage-dependent anion channel (VDAC), it reversibly and partially blocks VDAC conductance by its acidic C-terminal tail. Using single-molecule electrophysiology of reconstituted VDAC we now demonstrate that, at CaCl2 concentrations below 150 mM, Syn reverses the channels selectivity from anionic to cationic. Importantly, we find that the decrease in channel conductance upon its blockage by Syn is hugely overcompensated by a favorable change in the electrostatic environment for calcium, making the blocked state orders-of-magnitude more selective for calcium and thus increasing its net flux. These findings reveal a new regulatory role of Syn, with clear implications for both normal calcium signaling and PD-associated mitochondrial dysfunction.