Cooperativity between individual transporter protomers: new data fuelling old complexes

Sitte, Harald H.; Schütz, Gerhard J.; Freissmuth, Michael

doi:10.1111/jnc.13086

Cited by 3 publications

(3 citation statements)

References 27 publications

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“…The passage between these states takes place via intermediates occluded to both EC and IC regions either in substrate/Na ϩ -loaded form or in the apo state after the release of the cargo. In addition, eukaryotic NSS members such as DAT and SERT allow for the efflux of their substrate to the cell exterior, which has been attributed to the modulating effects of addictive psychostimulants such as AMPH (5,6).…”

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confidence: 99%

Allosteric modulation of human dopamine transporter activity under conditions promoting its dimerization

Cheng

Garcia‐Olivares

Wasserman

et al. 2017

Journal of Biological Chemistry

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The human dopamine (DA) transporter (hDAT) is a key regulator of neurotransmission and a target for antidepressants and addictive drugs. Despite the recent resolution of dDAT structures from , complete understanding of its mechanism of function and even information on its biological assembly is lacking. The resolved dDAT structures are monomeric, but growing evidence suggests that hDAT might function as a multimer, and its oligomerization may be relevant to addictive drug effects. Here, using structure-based computations, we examined the possible mechanisms of hDAT dimerization and its dynamics in a lipid bilayer. Using a combination of site-directed mutagenesis, DA-uptake, and cross-linking experiments that exploited the capacity of Cys-306 to form intermonomeric disulfide bridges in the presence of an oxidizing agent, we tested the effects of mutations at transmembrane segment (TM) 6 and 12 helices in HEK293 cells. The most probable structural model for hDAT dimer suggested by computations and experiments differed from the dimeric structure resolved for the bacterial homolog, LeuT, presumably because of a kink at TM12 preventing favorable monomer packing. Instead, TM2, TM6, and TM11 line the dimer interface. Molecular dynamics simulations of the dimeric hDAT indicated that the two subunits tend to undergo cooperative structural changes, both on local (extracellular gate opening/closure) and global (transition between outward-facing and inward-facing states) scales. These observations suggest that hDAT transport properties may be allosterically modulated under conditions promoting dimerization. Our study provides critical insights into approaches for examining the oligomerization of neurotransmitter transporters and sheds light on their drug modulation.

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confidence: 99%

Allosteric modulation of human dopamine transporter activity under conditions promoting its dimerization

Cheng

Garcia‐Olivares

Wasserman

et al. 2017

Journal of Biological Chemistry

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“…24−28 Oligomerization has been linked to cooperativity among monomeric units 29 and to AMPH-induced dopamine efflux. 30,31 The interfacial contacts observed in LeuT dimer are mainly between TM9 and TM12 (Figure 1A and B). In DAT, homodimers were detected upon cross-linking the EC ends of the TM6 helices using the endogenous Cys306.…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, oligomerization of NSSs has been suggested to be essential to their trafficking to the plasma membrane and efficient substrate transport . DAT has been shown to exist as a dimer or a higher oligomer in several studies. − Oligomerization has been linked to cooperativity among monomeric units and to AMPH-induced dopamine efflux. , The interfacial contacts observed in LeuT dimer are mainly between TM9 and TM12 (Figure A and B). In DAT, homodimers were detected upon cross-linking the EC ends of the TM6 helices using the endogenous Cys306 .…”

Section: Introductionmentioning

confidence: 99%

Effect of Dimerization on the Dynamics of Neurotransmitter:Sodium Symporters

et al. 2017

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Dimerization is a common feature among the members of the neurotransmitter:sodium symporter (NSS) family of membrane proteins. Yet, the effect of dimerization on the mechanism of action of NSS members is not fully understood. In this study, we examined the collective dynamics of two members of the family, leucine transporter (LeuT) and dopamine transporter (DAT), to assess the significance of dimerization in modulating the functional motions of the monomers. We used to this aim the anisotropic network model (ANM), an efficient and robust method for modeling the intrinsic motions of proteins and their complexes. Transporters belonging to the NSS family are known to alternate between outward-facing (OF) and inward-facing (IF) states, which enables the uptake and release of their substrate (neurotransmitter) respectively, as the substrate is transported from the exterior to the interior of the cell. In both LeuT and DAT, dimerization is found to alter the collective motions intrinsically accessible to the individual monomers in favor of the functional transitions (OF ↔ IF), suggesting that dimerization may play a role in facilitating transport.

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Glycine Transporters in Glia Cells: Structural Studies

López-Corcuera

Benito-Muñoz

Aragón

2017

Advances in Neurobiology

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Glycine, besides exerting essential metabolic functions, is an important inhibitory neurotransmitter in caudal areas of the central nervous system and also a positive neuromodulator at excitatory glutamate-mediated synapses. Glial cells provide metabolic support to neurons and modulate synaptic activity. Six transporters belonging to three solute carrier families (SLC6, SLC38, and SLC7) are capable of transporting glycine across the glial plasma membrane. The unique glial glycine-selective transporter GlyT1 (SLC6) is the main regulator of synaptic glycine concentrations, assisted by the neuronal GlyT2. The five additional glycine transporters ATB, SNAT1, SNAT2, SNAT5, and LAT2 display broad amino acid specificity and have differential contributions to glial glycine transport. Glial glycine transporters are divergent in sequence but share a similar architecture displaying the 5 + 5 inverted fold originally characterized in the leucine transporter LeuT. The availability of protein crystals solved at high resolution for prokaryotic and, more recently, eukaryotic homologues of this superfamily has advanced significantly our understanding of the mechanism of glycine transport.

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Cooperativity between individual transporter protomers: new data fuelling old complexes

Cited by 3 publications

References 27 publications

Allosteric modulation of human dopamine transporter activity under conditions promoting its dimerization

Allosteric modulation of human dopamine transporter activity under conditions promoting its dimerization

Effect of Dimerization on the Dynamics of Neurotransmitter:Sodium Symporters

Glycine Transporters in Glia Cells: Structural Studies

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