title: Glycine transporters GlyT1 and GlyT2 are differentially modulated by glycogen synthase kinase 3β.
abstract: Inhibitory glycinergic neurotransmission is terminated by the specific glycine transporters GlyT1 and GlyT2 which actively reuptake glycine from the synaptic cleft. GlyT1 is associated with both glycinergic and glutamatergic pathways, and is the main regulator of the glycine levels in the synapses. GlyT2 is the main supplier of glycine for vesicle refilling, a process that is vital to preserve the quantal glycine content in synaptic vesicles. Therefore, to control glycinergic neurotransmission efficiently, GlyT1 and GlyT2 activity must be regulated by diverse neuronal and glial signaling pathways. In this work, we have investigated the possible functional modulation of GlyT1 and GlyT2 by glycogen synthase kinase 3 (GSK3β). This kinase is involved in mood stabilization, neurodegeneration and plasticity at excitatory and inhibitory synapses. The co-expression of GSK3β with GlyT1 or GlyT2 in COS-7 cells and Xenopus laevis oocytes, leads to inhibition and stimulation of GlyT1 and GlyT2 activities, respectively, with a decrease of GlyT1, and an increase in GlyT2 levels at the plasma membrane. The specificity of these changes is supported by the antagonism exerted by a catalytically inactive form of the kinase and through inhibitors of GSK3β such as lithium chloride and TDZD-8. GSK3β also increases the incorporation of 32Pi into GlyT1 and decreases that of GlyT2. The pharmacological inhibition of the endogenous GSK3β in neuron cultures of brainstem and spinal cord leads to an opposite modulation of GlyT1 and GlyT2.Our results suggest that GSK3β is important for stabilizing and/or controlling the expression of functional GlyTs on the neural cell surface.
authors.affiliation: Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras, ISCIII, Madrid, Spain; IdiPAZ-Hospital Universitario La Paz, Madrid, Spain.
authors.forename: Esperanza
authors.initials: E
authors.lastname: Jiménez
authors.affiliation: Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras, ISCIII, Madrid, Spain; IdiPAZ-Hospital Universitario La Paz, Madrid, Spain.
authors.forename: Enrique
authors.initials: E
authors.lastname: Núñez
authors.affiliation: Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras, ISCIII, Madrid, Spain; IdiPAZ-Hospital Universitario La Paz, Madrid, Spain.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Ibáñez
authors.affiliation: Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras, ISCIII, Madrid, Spain; IdiPAZ-Hospital Universitario La Paz, Madrid, Spain.
authors.forename: Francisco
authors.initials: F
authors.lastname: Zafra
authors.affiliation: Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras, ISCIII, Madrid, Spain; IdiPAZ-Hospital Universitario La Paz, Madrid, Spain.
authors.forename: Carmen
authors.initials: C
authors.lastname: Aragón
authors.affiliation: Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras, ISCIII, Madrid, Spain; IdiPAZ-Hospital Universitario La Paz, Madrid, Spain. Electronic address: cgimenez@cbm.csic.es.
authors.forename: Cecilio
authors.initials: C
authors.lastname: Giménez
mesh_terms: D000818:Animals; D001692:Biological Transport; D001933:Brain Stem / Q000166:cytology; D019556:COS Cells; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics; D005998:Glycine / Q000378:metabolism / Q000494:pharmacology; D050487:Glycine Plasma Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D038362:Glycogen Synthase Kinase 3 / Q000235:genetics / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D018021:Lithium Chloride / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D009865:Oocytes; D051381:Rats; D017208:Rats, Wistar; D013116:Spinal Cord / Q000166:cytology; D014316:Tritium / Q000378:metabolism; D014982:Xenopus laevis
chemical_list: D004791:Enzyme Inhibitors; D050487:Glycine Plasma Membrane Transport Proteins; C493269:Slc6a5 protein, rat; C493266:Slc6a9 protein, rat; D014316:Tritium; D000071679:Glycogen Synthase Kinase 3 beta; C000605508:Gsk3b protein, rat; D038362:Glycogen Synthase Kinase 3; D018021:Lithium Chloride; D005998:Glycine
keywords: GSK3β; GlyT1; GlyT2; Glycinergic neurotransmission; Hereditary hyperekplexia; Pharmacological inhibitors