α-synuclein assemblies sequester neuronal α3-Na+/K+-ATPase and impair Na+ gradient

Extracellular alpha-synuclein (alpha-syn) assemblies can be up-taken by neurons; however, their interaction with the plasma membrane and proteins has not been studied specifically. Here we demonstrate that alpha-syn assemblies form clusters within the plasma membrane of neurons. Using a proteomic-based approach, we identify the alpha 3-subunit of Na+/K+-ATPase (NKA) as a cell surface partner of alpha-syn assemblies. The interaction strength depended on the state of alpha-syn, fibrils being the strongest, oligomers weak, and monomers none. Mutations within the neuron-specific alpha 3-subunit are linked to rapid-onset dystonia Parkinsonism (RDP) and alternating hemiplegia of childhood (AHC). We show that freely diffusing alpha 3-NKA are trapped within alpha-syn clusters resulting in alpha 3-NKA redistribution and formation of larger nanoclusters. This creates regions within the plasma membrane with reduced local densities of alpha 3-NKA, thereby decreasing the efficiency of Na+ extrusion following stimulus. Thus, interactions of alpha 3-NKA with extracellular alpha-syn assemblies reduce its pumping activity as its mutations in RDP/AHC.