Serotonin modulates the dissociation of [3H]imipramine from human platelet recognition sites

Wennogle, Lawrence P.; Meyerson, Laurence R.

doi:10.1016/0014-2999(82)90333-8

Cited by 120 publications

(56 citation statements)

References 6 publications

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“…There is substantial evidence for the existence of a secondary low affinity allosteric site that can modulate dissociation rates of several SERT ligands from the high affinity binding site (39). Although further experiments are needed to fully address the existence of a functional relevant vestibule inhibitor-binding pocket, our observation that nonconservative mutations in this region in hSERT fail to alter inhibitor K i indicate that, if present, such a binding site has little influence on the overall inhibitory mechanism.…”

Section: Discussionmentioning

confidence: 89%

“…In both cases, the temporal accessibility of the inhibitor-binding site decreases. Indeed, it has been observed for imipramine that the dissociation rate is decreased in the presence of 5HT, which suggest cooperativity between two physically distinct binding sites (39). Therefore, the effects of mutation of Ile-172 and Ser-438 cannot be interpreted unambiguously without substantiating direct interactions between these residues and the inhibitor molecule.…”

Section: Discussionmentioning

confidence: 99%

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Location of the Antidepressant Binding Site in the Serotonin Transporter

Andersen

Taboureau

Hansen

et al. 2009

Journal of Biological Chemistry

108

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The serotonin transporter (SERT) regulates extracellular levels of serotonin (5-hydroxytryptamine, 5HT) in the brain by transporting 5HT into neurons and glial cells. The human SERT (hSERT) is the primary target for drugs used in the treatment of emotional disorders, including depression. hSERT belongs to the solute carrier 6 family that includes a bacterial leucine transporter (LeuT), for which a high resolution crystal structure has become available. LeuT has proved to be an excellent model for human transporters and has advanced the understanding of solute carrier 6 transporter structure-function relationships. However, the precise structural mechanism by which antidepressants inhibit hSERT and the location of their binding pockets are still elusive. We have identified a residue (Ser-438) located within the 5HT-binding pocket in hSERT to be a critical determinant for the potency of several antidepressants, including the selective serotonin reuptake inhibitor citalopram and the tricyclic antidepressants imipramine, clomipramine, and amitriptyline. A conservative mutation of Ser-438 to threonine (S438T) selectively increased the K i values for these antidepressants up to 175-fold. The effects of introducing a protein methyl group into the 5HT-binding pocket by S438T were absent or reduced for analogs of these antidepressants lacking a single methyl group. This suggests that these antidepressants interact directly with Ser-438 during binding to hSERT, implying an overlapping localization of substrateand inhibitor-binding sites in hSERT suggesting that antidepressants function by a mechanism that involves direct occlusion of the 5HT-binding site.

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Section: Discussionmentioning

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Location of the Antidepressant Binding Site in the Serotonin Transporter

Andersen

Taboureau

Hansen

et al. 2009

Journal of Biological Chemistry

108

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“…Monoamine transporters have twelve transmembrane helices (TM) with TMs 1-5 and TMs 6-10 forming an invertedtopological repeat within which is a central binding site for substrate and ions approximately halfway across the membrane [7][8][9] . An extracellular vestibule in the outward-facing conformation 7,9,10 forms a secondary, allosteric site which, when occupied by ligands, can result in modulation of transporter activity by altering the kinetics of ligand dissociation from the central site [11][12][13] . Addictive substances such as cocaine and amphetamine bind to monoamine transporters and can either inhibit NT transport or promote NT efflux, respectively 14,15 .…”

Section: Main Textmentioning

confidence: 99%

“…It is made available under a The copyright holder for this preprint (which was not . http://dx.doi.org/10.1101/204859 doi: bioRxiv preprint first posted online Oct. 17, 2017; page 3 of 15 in modulation of transporter activity by altering the kinetics of ligand dissociation from the central site [11][12][13] . Addictive substances such as cocaine and amphetamine bind to monoamine transporters and can either inhibit NT transport or promote NT efflux, respectively 14,15 .…”

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confidence: 99%

Structural basis for recognition of diverse antidepressants by the human serotonin transporter

Coleman

Gouaux

2017

Preprint

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Selective serotonin reuptake inhibitors are clinically prescribed antidepressants that act by increasing the local concentration of neurotransmitter at synapses and in extracellular spaces via blockade of the serotonin transporter. Here we report x-ray structures of engineered thermostable variants of the human serotonin transporter bound to the antidepressants sertraline, fluvoxamine, and paroxetine. The drugs prevent serotonin binding by occupying the central substrate binding site and stabilizing the transporter in an outward-open conformation.These structures explain how residues within the central site orchestrate binding of chemically diverse inhibitors and mediate transporter-drug selectivity. MAIN TEXTIn the central nervous system the serotonin transporter (SERT) modulates serotoninergic signaling by carrying out the uptake of serotonin (5-HT) from the synaptic space into presynaptic . An extracellular vestibule in the outward-facing conformation 7,9,10 forms a secondary, allosteric site which, when occupied by ligands, can result . CC-BY-NC-ND 4.0 International license peer-reviewed) is the author/funder. It is made available under a The copyright holder for this preprint (which was not . http://dx.doi.org/10.1101/204859 doi: bioRxiv preprint first posted online Oct. 17, 2017; page 3 of 15 in modulation of transporter activity by altering the kinetics of ligand dissociation from the central site [11][12][13] . Addictive substances such as cocaine and amphetamine bind to monoamine transporters and can either inhibit NT transport or promote NT efflux, respectively 14,15 . Selective serotonin reuptake inhibitors (SSRIs) are a class of small molecules that are highly selective for SERT over DAT and NET and that inhibit 5-HT reuptake with nanomolar potency Fig. 1), and as a consequence these compounds bind with a range of affinities to SERT. Sertraline contains a tetrahydronaphthalene ring system linked to a secondary amine together with a meta and para substituted dichlorophenyl group. Fluvoxamine, by contrast, consists of a 2-aminoethyloxime moiety attached to a methyoxybutyl group, and a phenyl group containing a trifluoronated methyl at the para positon. Fluoxetine also contains a trifluoronated aromatic group but is instead coupled to a phenylpropylamine moiety. Paroxetine and citalopram also differ substantially in the structures of their aromatic, amine, and halogenated substitutents.Recently, we solved x-ray structures of a thermostabilized, transport-inactive construct of human SERT, deemed the ts3 construct, in complex with the SSRIs paroxetine and citalopram 8 .We employed the thermostabilized variant of SERT in order to facilitate purification and crystallization 19,20 . One of the thermostabilizing mutations, however, involves a residue (Thr439Ser) that is directly positioned within the central binding site, in close proximity to the bound SSRIs. Moreover, recent computational modeling of a wild-type SERT-paroxetine complex, in which the structure of the Drosophila DAT was used as a ...

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“…The boxed conformation represents an actual crystal structure, whereas the others are conceptualizations. Outer panels reproduced from Singh et al 47 148 Although the extracellular vestibule site cannot be excluded as the low-affinity allosteric site reported in SERT, 157,158 the primary, high-affinity binding site for the TCAs (at least for CMI, IMI and DMI) probably resides a bit deeper in the protein core, close to or partly overlapping with the substrate binding site. Removing all ambiguities and conclusively pinpointing the actual TCA binding site will require crystal structure determination of a eukaryotic SERT/NET and/or an invertebrate DAT in complex with a TCA.…”

Section: Mechanism Of Inhibitionmentioning

confidence: 99%

LeuT: A prokaryotic stepping stone on the way to a eukaryotic neurotransmitter transporter structure

Singh¹

2008

Channels

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To cite this article: Satinder K. Singh (2008) LeuT: A prokaryotic stepping stone on the way to a eukaryotic neurotransmitter transporter structure, Channels Ion-coupled secondary transport is utilized by a broad range of integral membrane proteins to catalyze the energetically unfavorable movement of solute molecules across a lipid bilayer. Members of the solute carrier 6 (SLC6) family, present in both prokaryotes and eukaryotes, are sodium-coupled symporters that play crucial roles in processes as diverse as nutrient uptake and neurotransmitter clearance. The crystal structure of LeuT, a bacterial member of this family, provided the first atomic-level glimpse into overall architecture, pinpointed the substrate and sodium binding sites and implicated candidate helices and residues in the "gating" conformational changes that accompany ion binding and release. The structure is consistent with a wealth of elegant biochemical data on the eukaryotic counterparts and has for the first time permitted the construction of accurate homology models that can be directly tested experimentally. Sequence identity is especially high near the substrate and sodium binding sites and, thus, molecular insights within these regions have been substantial. However, there are several topics relevant to transport mechanism, inhibition and regulation that structure/function studies of LeuT cannot adequately address, suggesting the need for a eukaryotic transporter crystal structure.

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Serotonin modulates the dissociation of [3H]imipramine from human platelet recognition sites

Cited by 120 publications

References 6 publications

Location of the Antidepressant Binding Site in the Serotonin Transporter

Location of the Antidepressant Binding Site in the Serotonin Transporter

Structural basis for recognition of diverse antidepressants by the human serotonin transporter

LeuT: A prokaryotic stepping stone on the way to a eukaryotic neurotransmitter transporter structure

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