Abstract
BackgroundThe dopamine transporter (DAT) plays a critical role in terminating the action of dopamine by rapid reuptake into the presynaptic neuron. Previous studies have revealed that the DAT carboxyl terminus (DAT-CT) can directly interact with other cellular proteins and regulate DAT function and trafficking.ResultsHere, we have identified that carboxypeptidase E (CPE), a prohormone processing exopeptidase and sorting receptor for the regulated secretory pathway, interacts with the DAT-CT and affects DAT function. Mammalian cell lines coexpressing CPE and DAT exhibited increased DAT-mediated dopamine uptake activity compared to cells expressing DAT alone. Moreover, coexpression of an interfering DAT-CT minigene inhibited the effects of CPE on DAT. Functional changes caused by CPE could be attributed to enhanced DAT expression and subsequent increase in DAT cell surface localization, due to decreased DAT degradation. In addition, CPE association could reduce the phosphorylation state of DAT on serine residues, potentially leading to reduced internalization, thus stabilizing plasmalemmal DAT localization.ConclusionTaken together, our results reveal a novel role for CPE in the regulation of DAT trafficking and DAT-mediated DA uptake, which may provide a novel target in the treatment of dopamine-governed diseases such as drug addiction and obesity.
Highlights
The dopamine transporter (DAT) plays a critical role in terminating the action of dopamine by rapid reuptake into the presynaptic neuron
DAT carboxyl terminus (CT) directly interacts with carboxypeptidase E (CPE) To search for DAT-interacting proteins, we employed the entire DAT carboxyl terminus (DAT-CT) as bait to screen a human substantia nigra library using the yeast two-hybrid system (Fig 1A)
To exclude the possibility of CPE non- binding to GST fusion peptides, intracellular N-terminal domain of DAT was employed as a control
Summary
The dopamine transporter (DAT) plays a critical role in terminating the action of dopamine by rapid reuptake into the presynaptic neuron. Previous studies have revealed that the DAT carboxyl terminus (DAT-CT) can directly interact with other cellular proteins and regulate DAT function and trafficking. The dopamine transporter (DAT) is a presynaptic plasma protein found on dopaminergic nerve terminals that terminates dopamine signaling by rapidly sequestering dopamine released into the synaptic cleft [1,2]. Morphological studies reveal that functional DATs are localized on the plasma membrane of axons, pre-synaptic (page number not for citation purposes). The PDZ domain-containing protein PICK1, which binds to a type II PDZ binding site localized at the DAT distal carboxyl termini, increases the efficiency of ER-to-plasma membrane trafficking of the transporter [7,16]. Our lab has shown that the DAT CT can bind to α-synuclein, which stabilizes DAT on the surface and could accelerate DA-induced oxidative stress and cell death [18]
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call