Transmembrane Domain 6 of the Human Serotonin Transporter Contributes to an Aqueously Accessible Binding Pocket for Serotonin and the Psychostimulant 3,4-Methylene Dioxymethamphetamine

A Conserved Asparagine Residue in Transmembrane Segment 1 (TM1) of Serotonin Transporter Dictates Chloride-coupled Neurotransmitter Transport

“…For example, our MD analysis implicated Ser-336 as an important residue in the Cl Ϫ dependence of transport coupling. This residue was previously proposed to coordinate Cl Ϫ in SERT (34,60) and GAT-1 (33, 59), and we found that S336C exhibits the same insensitivity to MTSES as N101C (64). Experimental analysis of the hSERT S336C mutant subsequently revealed that like in N101C, 5-HT transport by S336C was not dramatically stimulated by Cl Ϫ .…”

Transgenic elimination of high-affinity antidepressant and cocaine sensitivity in the presynaptic serotonin transporter

“…Based on hydrophobicity assessments and high-resolution crystal structures of the SLC6 family member LeuT Aa , SERT is proposed to contain 12 transmembrane domains (TMs), four of which-TMs 1, 3, 6, and 8-provide the key residues for ion and substrate recognition (24)(25)(26)(27). By using the pharmacological differences displayed by human and Drosophila melanogaster SERTs (hSERT and dSERT), we identified variation at a single residue in TM3 (I172 in human and mouse, M167 in fly) proximal to the proposed binding site for 5-HT (28).…”

SLC6 Neurotransmitter Transporters: Structure, Function, and Regulation

“…Accordingly, LeuTbased homology modeling is emerging as a valuable tool in studies of the NTT members, both in purely computational studies Huang and Zhan, 2007;Jørgensen et al, 2007a,b;Indarte et al, 2008;Xhaard et al, 2008;Kardos et al, 2010;Wein and Wanner, 2010) and as a complementary tool in functional studies (Dodd and Christie, 2007;Forrest et al, 2007Forrest et al, , 2008Paczkowski et al, 2007;Vandenberg et al, 2007;Zomot et al, 2007;Beuming et al, 2008;Celik et al, 2008b;Kniazeff et al, 2008;Andersen et al, 2009bAndersen et al, , 2010Kaufmann et al, 2009;Tavoulari et al, 2009;Field et al, 2010;Koldsø et al, 2010;Sinning et al, 2010) (section III). Modeling of DAT and SERT have so far received the most attention, which probably reflects the important role of these transporters as drug targets and results in generation of several three-dimensional models of human DAT (Beuming et al, , 2008Ravna, 2006;Indarte et al, 2008) and human SERT Forrest et al, 2007;Jørgensen et al, 2007a,b;Celik et al, 2008b;Forrest et al, 2008).…”

“…The central substrate binding pocket is an obvious candidate site for binding of competitive inhibitors, because inhibitor binding sites overlapping with the S1 substrate site offer a straightforward structural mechanism for competitive inhibition and are in agreement with pharmacological data showing that competitive inhibitors can be displaced in a concentration-dependent manner by substrates (Talvenheimo et al, 1979;Humphreys et al, 1988;Marcusson and Tiger, 1988;Graham et al, 1989;Apparsundaram et al, 2008). Although mutational studies on the SLC6 NTTs have identified residues in virtually all TM domains to be important for recognition of competitive inhibitors, the majority of the most sensitive residues reside within the regions that form the extracellular permeation pathway and the S1 substrate binding pocket (Barker et al, 1994(Barker et al, , 1998Barker and Blakely, 1996;Mortensen et al, 1999;Adkins et al, 2001;Larsen et al, 2004;Henry et al, 2006b;Beuming et al, 2008;Severinsen et al, 2008;Walline et al, 2008;Andersen et al, 2009bAndersen et al, , 2010Field et al, 2010). For example, in the monoamine transporters, sensitivity toward a wide range of competitive inhibitors, including fluoxetine, paroxetine, citalopram, and imipramine, as well as psychostimulants such as cocaine and amphet- THE SLC6 NEUROTRANSMITTER TRANSPORTERS amines, can be decreased by several orders of magnitude by mutation of S1 residues (Barker et al, 1999;Henry et al, 2006b;Beuming et al, 2008;Walline et al, 2008;Andersen et al, 2009bAndersen et al, , 2010Koldsø et al, 2010;Sinning et al, 2010).…”