Dopamine Transporter Interacts With Sigma‐1R

Abstract

The dopamine transporter (DAT) is a plasma membrane transporter that is implicated in neuropsychiatric and neurodegenerative diseases. DAT is a target for psychostimulants such as methamphetamine. Interestingly, it has been shown that activation of sigma‐1R, an ER protein, can increase dopamine synthesis and release. The sigma‐1R is a novel non‐opioid protein discovered by Dr. Tsung Ping‐Su. Sigma‐1R antagonists have shown to prevent neurotoxicity and dopamine depletions while sigma‐1R agonists thought to increase the synthesis and release of dopamine. In this study we asked whether DAT and sigma‐1R interact. We used florescence recovery after photobleaching (FRAP) and florescence resonance energy transfer (FRET) in order to examine the potential interaction between CFP‐sigma‐1R and YFP‐DAT in CHO cells stably expressing YFP‐DAT, and transiently expressing CFP‐sigma‐1R. In cells co‐expressing CFP‐sigma‐ 1R and YFP‐DAT, there is a positive FRET signal between CFP‐sigma‐1R and YFP‐DAT. This positive FRET signal is detectable at the plasma membrane. Therefore, our preliminary data suggest a potential interaction between sigma‐1R and DAT. Furthermore, we found that the frequency of positive FRET signal between CFP‐sigma‐1R and YFP‐DAT increases when the cells are pre‐treated with methamphetamine a DAT substrate and a sigma‐1R ligand. Our FRAP data further confirms this potential interaction. We found that the mobility of globular CFP‐sigma‐1R increases in YFP‐DAT expressing cells. Importantly, methamphetamine exposure increases the mobility of sigma‐1R in the presence or absence of YFP‐DAT. Currently, we are examining the cell surface and intracellular dynamic of filament clusters of sigma‐1R in DAT expressing cells as well as when the cell are exposed to methamphetamine. Understanding the molecular mechanism of potential DAT/sigma‐1R interaction is critical in understanding of dopaminergic system in the brain under normal condition and when it is exposed to psychostimulants.