Mechanisms of anion conduction by coupled glutamate transporters

Cell. 2015 Jan 29;160(3):542-53. doi: 10.1016/j.cell.2014.12.035.


Excitatory amino acid transporters (EAATs) are essential for terminating glutamatergic synaptic transmission. They are not only coupled glutamate/Na(+)/H(+)/K(+) transporters but also function as anion-selective channels. EAAT anion channels regulate neuronal excitability, and gain-of-function mutations in these proteins result in ataxia and epilepsy. We have combined molecular dynamics simulations with fluorescence spectroscopy of the prokaryotic homolog GltPh and patch-clamp recordings of mammalian EAATs to determine how these transporters conduct anions. Whereas outward- and inward-facing GltPh conformations are nonconductive, lateral movement of the glutamate transport domain from intermediate transporter conformations results in formation of an anion-selective conduction pathway. Fluorescence quenching of inserted tryptophan residues indicated the entry of anions into this pathway, and mutations of homologous pore-forming residues had analogous effects on GltPh simulations and EAAT2/EAAT4 measurements of single-channel currents and anion/cation selectivities. These findings provide a mechanistic framework of how neurotransmitter transporters can operate as anion-selective and ligand-gated ion channels.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Amino Acid Transport System X-AG / chemistry*
  • Amino Acid Transport System X-AG / metabolism
  • Animals
  • Anions / metabolism*
  • Archaeal Proteins / chemistry*
  • Archaeal Proteins / metabolism
  • Glutamate Plasma Membrane Transport Proteins / chemistry*
  • Glutamate Plasma Membrane Transport Proteins / genetics
  • Glutamate Plasma Membrane Transport Proteins / metabolism
  • Humans
  • Molecular Dynamics Simulation*
  • Molecular Sequence Data
  • Mutation
  • Patch-Clamp Techniques
  • Pyrococcus horikoshii / chemistry*
  • Rats
  • Sequence Alignment


  • Amino Acid Transport System X-AG
  • Anions
  • Archaeal Proteins
  • Glutamate Plasma Membrane Transport Proteins