Pharmacological Chaperones of the Dopamine Transporter Rescue Dopamine Transporter Deficiency Syndrome Mutations in Heterologous Cells.

Mutations in the dopamine transporter (DAT) gene cause hereditary dopamine transporter deficiency syndrome (DTDS), a rare condition often involving defective transporter trafficking and folding. Screening known DAT ligands revealed that bupropion and ibogaine increase DAT surface expression, while cocaine and methylphenidate do not. These drugs raise wild-type DAT protein levels and promote maturation of the ER-retained mutant K590A, an effect blocked by inhibiting ER-to-Golgi transport or by knocking down the COPII component SEC24D. Both drugs also rescue maturation and functional activity of DTDS-associated mutations A314V and R445C. This is the first demonstration of pharmacological chaperoning of DAT, suggesting a potential therapeutic approach for DTDS and related conditions.

Study at a glance

Abstract

A number of pathological conditions have been linked to mutations in the dopamine transporter gene, including hereditary dopamine transporter deficiency syndrome (DTDS). DTDS is a rare condition that is caused by autosomal recessive loss-of-function mutations in the dopamine transporter (DAT), which often affects transporter trafficking and folding. We examined the possibility of using pharmacological chaperones of DAT to rescue DTDS mutations. After screening a set of known DAT ligands for their ability to increase DAT surface expression, we found that bupropion and ibogaine increased DAT surface expression, whereas others, including cocaine and methylphenidate, had no effect. Bupropion and ibogaine increased wild type DAT protein levels and also promoted maturation of the endoplasmic reticulum (ER)-retained DAT mutant K590A. Rescue of K590A could be blocked by inhibiting ER to Golgi transport using brefeldin A. Furthermore, knockdown of coat protein complex II (COPII) component SEC24D, which is important in the ER export of wild type DAT, also blocked the rescue effects of bupropion and ibogaine. These data suggest that bupropion and ibogaine promote maturation of DAT by acting as pharmacological chaperones in the ER. Importantly, both drugs rescue DAT maturation and functional activity of the DTDS-associated mutations A314V and R445C. Together, these results are the first demonstration of pharmacological chaperoning of DAT and suggest this may be a viable approach to increase DAT levels in DTDS and other conditions associated with reduced DAT function.