Modification of a putative third sodium site in the glycine transporter GlyT2 influences the chloride dependence of substrate transport
EntityUAM. Departamento de Biología Molecular; Instituto de Investigación Sanitaria Hospital Universitario de La Paz (IdiPAZ); Centro de Biología Molecular Severo Ochoa (CBM)
PublisherFrontiers Media S.A.
10.3389/fnmol.2018.00347Frontiers in Molecular Neuroscience 11 (2018): 347
Funded byThis work was supported by grants from the Spanish Dirección General de Investigación Científica y Técnica from the Spanish Ministerio de Economía y Competitividad (Grant Nos. SAF2014- 58045-R and SAF2017-84235-R). Institutional grants from the Fundación Ramón Areces and Banco de Santander to the CBMSO are also acknowledged. CB-M is a recipient of a grant BES-2015-072392 from the Spanish Ministerio de Economía y Competitividad.
ProjectGobierno de España. SAF2014- 58045-R; Gobierno de España. SAF2017-84235-R; Gobierno de España. BES-2015-072392
SubjectsGlyT; Hyperekplexia; Sodium site; Neurotransmitter reuptake; SLC6; Biología y Biomedicina / Biología
Rights© 2018 Benito-Muñoz, Perona, Abia, dos Santos, Núñez, Aragón and López-Corcuera.
Esta obra está bajo una Licencia Creative Commons Atribución 4.0 Internacional.
Neurotransmitter removal from glycine-mediated synapses relies on two sodium-driven high-affinity plasma membrane GlyTs that control neurotransmitter availability. Mostly glial GlyT1 is the main regulator of glycine synaptic levels, whereas neuronal GlyT2 promotes the recycling of synaptic glycine and supplies neurotransmitter for presynaptic vesicle refilling. The GlyTs differ in sodium:glycine symport stoichiometry, showing GlyT1 a 2:1 and GlyT2 a 3:1 sodium:glycine coupling. Sodium binds to the GlyTs at two conserved Na+ sites: Na1 and Na2. The location of GlyT2 Na3 site remains unknown, although Glu650 has been involved in the coordination. Here, we have used comparative MD simulations of a GlyT2 model constructed by homology to the crystalized DAT from Drosophila melanogaster by placing the Na3 ion at two different locations. By combination of in silico and experimental data obtained by biochemical and electrophysiological analysis of GlyTs mutants, we provide evidences suggesting the GlyT2 third sodium ion is held by Glu-250 and Glu-650, within a region with robust allosteric properties involved in cation-specific sensitivity. Substitution of Glu650 in GlyT2 by the corresponding methionine in GlyT1 reduced the charge-to-flux ratio to the level of GlyT1 without producing transport uncoupling. Chloride dependence of glycine transport was almost abolished in this GlyT2 mutant but simultaneous substitution of Glu250 and Glu650 by neutral amino acids rescued chloride sensitivity, suggesting that protonation/deprotonation of Glu250 substitutes chloride function. The differential behavior of equivalent GlyT1 mutations sustains a GlyT2-specific allosteric coupling between the putative Na3 site and the chloride site
Google Scholar:Benito-Muñoz, Cristina - Perona, Almudena - Abia, David - Santos, Helena G. dos - Núñez, Enrique - Aragón, Carmen - López Corcuera, Beatriz
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