Effect of palmitoylation on the dimer formation of the human dopamine transporter

Talia Zeppelin,Kasper B Pedersen,Birgit Schiøtt,Xavier Periole,Nils A Berglund

doi:10.1038/s41598-021-83374-y

Talia Zeppelin, Kasper B Pedersen + Show 3 more

Open Access

https://doi.org/10.1038/s41598-021-83374-y

Copy DOI

Abstract

The human dopamine transporter (hDAT) is one in three members of the monoamine transporter family (MAT). hDAT is essential for regulating the dopamine concentration in the synaptic cleft through dopamine reuptake into the presynaptic neuron; thereby controlling hDAT dopamine signaling. Dysfunction of the transporter is linked to several psychiatric disorders. hDAT and the other MATs have been shown to form oligomers in the plasma membrane, but only limited data exists on which dimeric and higher order oligomeric states are accessible and energetically favorable. In this work, we present several probable dimer conformations using computational coarse-grained self-assembly simulations and assess the relative stability of the different dimer conformations using umbrella sampling replica exchange molecular dynamics. Overall, the dimer conformations primarily involve TM9 and/or TM11 and/or TM12 at the interface. Furthermore, we show that a palmitoyl group (palm) attached to hDAT on TM12 modifies the free energy of separation for interfaces involving TM12, suggesting that S-palmitoylation may change the relative abundance of dimers involving TM12 in a biological context. Finally, a comparison of the identified interfaces of hDAT and palmitoylated hDAT to the human serotonin transporter interfaces and the leucine transporter interface, suggests similar dimer conformations across these protein family.

Highlights

The dopamine transporter (DAT) mediates reuptake of the neurotransmitter dopamine from the synaptic cleft back into the presynaptic neuron and thereby terminates dopaminergic signaling
Due to the location of the palm group on TM12, which has been shown from both leucine transporter (LeuT) crystal structures and hSERT self-assembly simulations to be involved in the dimer interface, we speculated that the palm group may have a regulatory mechanism on hDAT dimer formation, similar to what has been observed for some GPCRs35
In order to study which helices are most prevalent at the oligomeric interfaces of hDAT and how these are affected by hDAT being S-palmitoylated on TM12, we performed 10 self-assembly simulations each lasting 30 μs and containing 16 hDAT or 16 hDAT-palm proteins embedded in a pure POPC membrane bilayer (Fig. 1b)

Summary

Introduction

The dopamine transporter (DAT) mediates reuptake of the neurotransmitter dopamine from the synaptic cleft back into the presynaptic neuron and thereby terminates dopaminergic signaling. Due to the location of the palm group on TM12, which has been shown from both LeuT crystal structures and hSERT self-assembly simulations to be involved in the dimer interface, we speculated that the palm group may have a regulatory mechanism on hDAT dimer formation, similar to what has been observed for some GPCRs35. In this contribution, we employ our previous approach used for hSERT to investigate the impact of S-palmitoylation on hDAT oligomeric b ehavior[14,36]. We propose that the MATs share a common dimer pattern, which mainly involves the helices TM9, TM11, and TM12, and that S-palmitoylation may act as a functional switch

Methods

Results

Discussion

Conclusion