Fibrillar α-Synuclein (α-Syn) is the principal component of Lewy bodies which are evident in individuals affected by Parkinson disease (PD). This neuropathologic form of α-Syn contributes to PD progression and propagation of exogeneous α-Syn between neurons has been demonstrated. In order to identify proteins interacting with extracellularly applied α-syn assemblies (either oligomeric or fibrillar α -syn) and identify in particular plasma membrane proteins exposed extracellularly, we exposed pure-neuronal cultures to oligomeric and fibrillar α-syn for 10 min, pulled down the complex, and identified the associated proteins using a proteomic-based approach. Using pull-down of whole cell lysates and MS, we have identified proteins interacting with extracellularly applied α-syn in three different conditions. Each condition consisted in three experimental replicates of cells exposed 10 min to α-syn assemblies and the non-treated cells used as controls.