Synapsin Condensates Recruit alpha-Synuclein

•This study examines how α-synuclein affects the liquid phase of synapsin and SVs.•A phase of synapsin 1 sequesters α-synuclein.•SVs act as catalyzers for the phase separation of synapsin 1 and α-synuclein.•At physiological conditions, α-synuclein alone cannot induce a liquid phase of SVs.•The excess of α-synuclein slows down the rate of synapsin/SV condensate formation.