A1 Refereed original research article in a scientific journal
Prolyl Oligopeptidase Regulates Dopamine Transporter Oligomerization and Phosphorylation in a PKC- and ERK-Independent Manner
Authors: Julku Ulrika H, Jäntti Maria, Svarcbahs Reinis, Myöhänen Timo T
Publisher: MDPI
Publication year: 2021
Journal: International Journal of Molecular Sciences
Journal name in source: INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
Journal acronym: INT J MOL SCI
Article number: ARTN 1777
Volume: 22
Issue: 4
Number of pages: 16
eISSN: 1422-0067
DOI: https://doi.org/10.3390/ijms22041777
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/53629999
Prolyl oligopeptidase (PREP) is a serine protease that binds to alpha-synuclein (aSyn) and induces its aggregation. PREP inhibitors have been shown to have beneficial effects in Parkinson's disease models by enhancing the clearance of aSyn aggregates and modulating striatal dopamine. Additionally, we have shown that PREP regulates phosphorylation and internalization of dopamine transporter (DAT) in mice. In this study, we clarified the mechanism behind this by using HEK-293 and PREP knock-out HEK-293 cells with DAT transfection. We tested the effects of PREP, PREP inhibition, and alpha-synuclein on PREP-related DAT regulation by using Western blot analysis and a dopamine uptake assay, and characterized the impact of PREP on protein kinase C (PKC) and extracellular signal-regulated kinase (ERK) by using PKC assay and Western blot, respectively, as these kinases regulate DAT phosphorylation. Our results confirmed our previous findings that a lack of PREP can increase phosphorylation and internalization of DAT and decrease uptake of dopamine. PREP inhibition had a variable impact on phosphorylation of ERK dependent on the metabolic state of cells, but did not have an effect on phosphorylation or function of DAT. PREP modifications did not affect PKC activity either. Additionally, a lack of PREP elevated a DAT oligomerization that is associated with intracellular trafficking of DAT. Our results suggest that PREP-mediated phosphorylation, oligomerization, and internalization of DAT is not dependent on PKC or ERK.
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