Santos_2020_Biomolecules_10_

The aggregation of alpha-synuclein (alpha-Syn) is a characteristic of Parkinson's disease (PD). alpha-Syn oligomerization/aggregation is accelerated by the serine peptidase, prolyl oligopeptidase (POP). Factors that affect POP conformation, including most of its inhibitors and an impairing mutation in its active site, influence the acceleration of alpha-Syn aggregation resulting from the interaction of these proteins. It is noteworthy, however, that alpha-Syn is not cleaved by POP. Prolyl endopeptidase-like (PREPL) protein is structurally related to the serine peptidases belonging to the POP family. Based on the alpha-Syn-POP studies and knowing that PREPL may contribute to the regulation of synaptic vesicle exocytosis, when this protein can encounter alpha-Syn, we investigated the alpha-Syn-PREPL interaction. The binding of these two human proteins was observed with an apparent affinity constant of about 5.7 muM and, as in the alpha-Syn assays with POP, the presence of PREPL accelerated the oligomerization/aggregation events, with no alpha-Syn cleavage. Furthermore, despite this lack of hydrolytic cleavage, the serine peptidase active site inhibitor phenylmethylsulfonyl fluoride (PMSF) abolished the enhancement of the alpha-Syn aggregation by PREPL. Therefore, given the attention to POP inhibitors as potential drugs to treat synucleinopathies, the present data point to PREPL as another potential target to be explored for this purpose.