PHARMACOLOGICAL RESCUE OF DOPAMINE TRANSPORTER MUTANTS LINKED WITH INFANTILE PARKINSONISM-DYSTONIA

H.M. Mazhar Asjad, Ameya Kasture, Ali El-Kasaby, Michael Freissmuth and Sonja Sucic

Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Waehringerstrasse 13A, 1090 Vienna, Austria

Abstract

Point mutation in the gene for dopamine transporter leaves the transporter misfolded which leads to infantile/juvenile parkinsonism- dystonia or dopamine transporter deficiency syndrome (DTDS). Our working hypothesis states that the ER stalled misfolded DAT mutants could be functionally rescued by pharmacological means. We verified this conjecture by (i) heterologously expressed DAT mutants stayed retained in the ER of HEK293 cells, (ii) various pharmacological compounds were screened which are known to either stabilize the transporter folding intermediates or bypass the ER quality control sensors, (iii) noribogaine which binds to and stabilizes inward facing conformation of transporter and pifithrin-μ, an inhibitor of HSP70 could functionally rescue three disease causing DAT mutants: namely, hDAT-V158F, hDAT-G327R and hDAT-L368Q, (iii) upon noribogaine treatment, hDAT-V158F traffics to presynaptic terminals in dopaminergic neurons of adult fly brain, and (iv) noribogaine or pifithrin-µ treatment restores the sleep in Drosophila expressing hDAT-V158F and hDAT-G327R in DAT-null background. The current research work not only provides a systematic in-vitro and in-vivo approach for screening DTDS causing DAT mutants but also consolidates the fact that pharmacochaperoning can be used to remedy disease causing folding deficiencies in SLC6 transporters.

Keywords: Dopamine transporter, pharmacochaperoning, dopamine transporter deficiency syndrome, drosophila, endoplasmic reticulum.