Prolyl oligopeptidase (PO) interacts with α-syncline in vitro. It is a weak interaction that induces a nucleation prone conformation of α-synuclein. PO accelerates aggregation and fibril formation of α-syncline in a process that can be reversed by specific inhibitors and is also influenced by an impairing mutation in the PO active site. There is evidence that PO and α-synuclein also interact intracellularly, especially in conditions where the expression of α-synuclein is high. Specific PO inhibitors reduce the number of cells with α-synuclein inclusions in a cellular model of Parkinson's disease. If these interactions also exist in the human brain, PO may be a target for the treatment of Parkinson's disease and other synucleinopathies. Whether PO also contributes to the normal physiological functions of α-syncline remains an open question, but there are some intriguing parallels between the proposed functions of both proteins that deserve further investigation.