Freezing and piercing of in vitro asymmetric plasma membrane by α-synuclein

Synucleinopathies are neurological diseases that are characterized by the accumulation of aggregates of a cytosolic protein, α-synuclein, at the plasma membrane. Even though the pathological role of the protein is established, the mechanism by which it damages neurons remains unclear due to the difficulty to correctly mimic the plasma membrane in vitro. Using a microfluidic setup in which the composition of the plasma membrane, including the asymmetry of the two leaflets, is recapitulated, we demonstrate a triple action of α-synuclein on the membrane. First, it changes membrane topology by inducing pores of discrete sizes, likely nucleated from membrane-bound proteins and subsequently enlarged by proteins in solution. Second, protein binding to the cytosolic leaflet increases the membrane capacitance by thinning it and/or changing its relative permittivity. Third, α-synuclein insertion inside the membrane hydrophobic core immobilizes the lipids in both leaflets, including the opposing protein-free extracellular one.
Heo and Pincet demonstrate the influence of α-synuclein aggregation on in vitro asymmetric membranes using a microfluidic setup. They show that synuclein aggregation on the asymmetric membranes leads to its thinning and formation of pores of discrete sizes and synuclein insertion immobilizes both the leaflets of the asymmetric membrane.