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Mechanism of the association between Na+ binding and conformations at the intracellular gate in neurotransmitter:sodium symporters

Journal Article · · Journal of Biological Chemistry
 [1];  [2];  [3];  [4];  [5];  [4];  [4];  [2];  [3];  [5];  [6]
  1. Weill Medical College of Cornell Univ., New York, NY (United States); Cornell Univ., Ithaca, NY (United States); DOE Office of Scientific and Technical Information (OSTI)
  2. Columbia Univ. College of Physicians and Surgeons, New York, NY (United States); New York State Psychiatric Institute, New York, NY (United States)
  3. Univ. of Calgary, Calgary, AB (Canada)
  4. Univ. of Copenhagen, Copenhagen (Denmark)
  5. Weill Medical College of Cornell Univ., New York, NY (United States)
  6. Weill Medical College of Cornell Univ., New York, NY (United States); National Institutes of Health, Baltimore, MD (United States)
Neurotransmitter:sodium symporters (NSSs) terminate neurotransmission by Na+-dependent reuptake of released neurotransmitters. Previous studies suggested that Na+-binding reconfigures dynamically coupled structural elements in an allosteric interaction network (AIN) responsible for function-related conformational changes, but the intramolecular pathway of this mechanism has remained uncharted. Here we describe a new approach for the modeling and analysis of intramolecular dynamics in the bacterial NSS homolog LeuT. From microsecond-scale molecular dynamics simulations and cognate experimental verifications in both LeuT and human dopamine transporter (hDAT), we apply the novel method to identify the composition and the dynamic properties of their conserved AIN. In LeuT, two different perturbations disrupting Na+ binding and transport (i.e. replacing Na+ with Li+ or the Y268A mutation at the intracellular gate) affect the AIN in strikingly similar ways. In contrast, other mutations that affect the intracellular gate (i.e. R5A and D369A) do not significantly impair Na+ cooperativity and transport. Our analysis shows these perturbations to have much lesser effects on the AIN, underscoring the sensitivity of this novel method to the mechanistic nature of the perturbation. Notably, this set of observations holds as well for hDAT, where the aligned Y335A, R60A, and D436A mutations also produce different impacts on Na+ dependence. Furthermore, the detailed AIN generated from our method is shown to connect Na+ binding with global conformational changes that are critical for the transport mechanism. Lastly, that the AIN between the Na+ binding sites and the intracellular gate in bacterial LeuT resembles that in eukaryotic hDAT highlights the conservation of allosteric pathways underlying NSS function.
Research Organization:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF); UT-Battelle, LLC, Oak Ridge, TN (United States)
Sponsoring Organization:
USDOE Office of Science (SC)
Grant/Contract Number:
AC05-00OR22725
OSTI ID:
1348222
Journal Information:
Journal of Biological Chemistry, Journal Name: Journal of Biological Chemistry Journal Issue: 22 Vol. 290; ISSN 0021-9258
Publisher:
American Society for Biochemistry and Molecular BiologyCopyright Statement
Country of Publication:
United States
Language:
English

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Spontaneous Inward Opening of the Dopamine Transporter is Triggered by PIP2-Regulated Dynamics of the N-Terminus journal February 2016
Transition metal ion FRET uncovers K+ regulation of a neurotransmitter/sodium symporter journal September 2016
MHC class II complexes sample intermediate states along the peptide exchange pathway journal November 2016
A partially-open inward-facing intermediate conformation of LeuT is associated with Na+ release and substrate transport journal January 2018
Bases of Bacterial Sodium Channel Selectivity Among Organic Cations journal October 2019
A conserved leucine occupies the empty substrate site of LeuT in the Na+-free return state journal May 2016
Locking Two Rigid-body Bundles in an Outward-Facing Conformation: The Ion-coupling Mechanism in a LeuT-fold Transporter journal December 2019
Competition between Li + and Na + in sodium transporters and receptors: Which Na + -Binding sites are “therapeutic” Li + targets? journal January 2018
Conformational dynamics of a neurotransmitter:sodium symporter in a lipid bilayer journal February 2017
Two Na + Sites Control Conformational Change in a Neurotransmitter Transporter Homolog journal November 2015
Conformational Dynamics on the Extracellular Side of LeuT Controlled by Na + and K + Ions and the Protonation State of Glu 290 journal July 2016
PySFD: comprehensive molecular insights from significant feature differences detected among many simulated ensembles journal September 2018
Structure-activity relationship studies of citalopram derivatives: examining substituents conferring selectivity for the allosteric site in the 5-HT transporter: Development of S2 selective ligands for SERT journal February 2016
Modeling and Dynamics of the Inward-Facing State of a Na+/Cl− Dependent Neurotransmitter Transporter Homologue journal August 2010