X-ray structures of Drosophila dopamine transporter in complex with nisoxetine and reboxetine

Abstract

Most antidepressants elicit their therapeutic benefits through selective blockade of Na+−Cl− - coupled neurotransmitters transporters. Here we report x-ray structures of the Drosophila melanogaster dopamine transporter in complexes with the polycyclic antidepressants nisoxetine or reboxetine. The inhibitors stabilize the transporter in an outward-open conformation by occupying the substrate binding site. These structures explain how interactions between the binding pocket and substituents on the aromatic rings of antidepressants modulate drug – transporter selectivity.

Glycinergic transmission: glycine transporter GlyT2 in neuronal pathologies

“…After binding, the transporter oscillates to an inward orientation releasing substrates and ions into the intracellular face of the membrane. Two Na + -binding sites have been identified in LeuT and dDAT that are conserved in GlyT2 and other SLC6 transporters [29][30][31][32]. Another potential binding site for Na + was identified in a cavity of GlyT2 formed by Trp 263 and Met 276 in the third transmembrane domanin (TM3), Ala 481 in TM6 and Glu 648 in TM10 [33].…”

“…Thus, while most of the transporters of this family present a cation coupling stoichiometry of two Na + transported with every neurotransmitter molecule (including GlyT1), GlyT2 is coupled to the electrochemical movement of three Na + , favoring the maintenance of a high glycine concentration gradient along the presynaptic membrane [28]. Recent structure-function studies have enhanced our current understanding of mechanisms of electrochemical coupling, studies that have been impelled by the determination of the crystal structures of two SLC6 transporters, the sodium-dependent bacterial leucine transporter, LeuT [29], and the Drosophila dopamine transporter, dDAT [30]. These transporters arrange the 12 transmembrane (TM) α-helices in a "shallow shot glass"-like structure with substrate-and ion-binding sites being located halfway across the membrane at the bottom of an extracellular-facing cavity.…”

Binding Mode Selection Determines the Action of Ecstasy Homologs at Monoamine Transporters

“…Inhibitors (e.g., cocaine) elevate extracellular monoamine concentrations by blocking reuptake of endogenous substrate from the extracellular space. Most of these inhibitors are competitive, and their binding sites overlap with the substrate-binding sites (Beuming et al, 2008;Penmatsa et al, 2013Penmatsa et al, , 2015Wang et al, 2015). Substrates (e.g., D-amphetamine), in contrast, increase extracellular monoamine concentrations via two mechanisms: 1) they compete with the endogenous substrate for reuptake from the extracellular space; and 2) they induce release of endogenous substrate molecules from intracellular stores by reversing the normal direction of transporter flux .…”

Markov State-Based Quantitative Kinetic Model of Sodium Release from the Dopamine Transporter

“…The function of NSS transporters in neuronal signaling implicate them in the mechanisms of action of abused psychostimulants, such as cocaine and amphetamine 2,3 , and in various psychiatric and neurological disorders including drug addiction, schizophrenia, and Parkinson's disease 3 . These essential neurophysiological roles have made NSS transporters primary targets for antidepressant medications.Breakthrough crystallographic determinations of members of the NSS family includes the bacterial homolog LeuT 4,5 , and most recently the structures of Drosophila DAT (dDAT) [6][7][8] . Structures of these transporters have been determined in complex with various substrates and ligands in the primary (S1) and secondary (S2) binding sites and with sodium ions bound in sites Na1 and Na2.…”

“…Breakthrough crystallographic determinations of members of the NSS family includes the bacterial homolog LeuT 4,5 , and most recently the structures of Drosophila DAT (dDAT) [6][7][8] . Structures of these transporters have been determined in complex with various substrates and ligands in the primary (S1) and secondary (S2) binding sites and with sodium ions bound in sites Na1 and Na2.…”