Neuronal and glial glycine transporters have different stoichiometries.
A neurotransmitter transporter can potentially mediate uptake or release of substrate, and its stoichiometry is a key factor that controls the driving force and thus the neurotransmitter flux direction. We have used a combination of electrophysiology and radio-tracing techniques to evaluate the stoichiometries of two glycine transporters involved in glycinergic or glutamatergic transmission. We show that GlyT2a, a transporter present in glycinergic boutons, has a stoichiometry of 3 Na+/Cl-/glycine, which predicts effective glycine accumulation in all physiological conditions. GlyT1b, a glial transporter, has a stoichiometry of 2 Na+/Cl-/ glycine, which predicts that glycine can be exported or imported, depending on physiological conditions. GlyT1b may thus modulate glutamatergic synapses by increasing or decreasing the glycine concentration around N-methyl-D-aspartate receptors (NMDARs).
Roux
M J
MJ
Laboratoire de Neurobiologie, Unité Mixte de Recherche 8544, Centre National de la Recherche Scientifique, Ecole Normale Supérieure, Paris, France.
Supplisson
S
S
D026921:Amino Acid Transport Systems, Neutral; D000818:Animals; D001692:Biological Transport / Q000502:physiology; D002352:Carrier Proteins / Q000032:analysis* / Q000378:metabolism; D004553:Electric Conductivity; D004594:Electrophysiology; D005110:Extracellular Space / Q000378:metabolism; D005998:Glycine / Q000493:pharmacokinetics; D050487:Glycine Plasma Membrane Transport Proteins; D007700:Kinetics; D008564:Membrane Potentials / Q000502:physiology; D009457:Neuroglia / Q000737:chemistry* / Q000378:metabolism; D009474:Neurons / Q000737:chemistry* / Q000378:metabolism; D009865:Oocytes / Q000502:physiology; D051381:Rats; D012964:Sodium / Q000493:pharmacokinetics; D014982:Xenopus laevis
D026921:Amino Acid Transport Systems, Neutral; D002352:Carrier Proteins; D050487:Glycine Plasma Membrane Transport Proteins; D012964:Sodium; D005998:Glycine