MDMA regulates serotonin transporter function via a Protein kinase C dependent mechanism

Serotonin (5-HT) is a neurotransmitter with an integral role in regulating mood and dysregulation of this system is implicated in disorders such as depression and withdrawal from drugs of abuse. 3,4- methylenedioxymethamphetamine (MDMA) or ‘Ecstasy’ is a commonly abused drug which primarily targets the serotonin transporter (SERT) and competes with serotonin (5-HT) for uptake into the pre-synaptic neuron. By understanding how MDMA regulates SERT function it may be possible to target this system to prevent or reverse the changes seen with MDMA use. Previous studies have shown that MDMA is able to down-regulate SERT expression from the cell surface to intracellular vesicles, thereby decreasing 5-HT transport. How MDMA targets this regulatory pathway is unclear. Protein Kinase C (PKC) is a well-known regulator of SERT, and activation of PKC causes phosphorylation of SERT, targeting the transporter for internalization. In this study, using rotating disc electrode voltammetry (RDEV) we show that MDMA causes a significant decrease in SERT function in HEK-293 cells transiently expressing EGFP-hSERT. This MDMA-induced down-regulation was not observed when cells were pretreated with PKC inhibitor, Bis I. This data shows that the MDMA-induced downregulation of SERT occurs via PKC dependent signaling pathways.