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Neuron. 2014 Dec 17;84(6):1287-301. doi: 10.1016/j.neuron.2014.11.008. Epub 2014 Nov 26.

Vesicular glutamate transporters use flexible anion and cation binding sites for efficient accumulation of neurotransmitter.

Author information

1
Department of Neurobiology, Max-Planck-Institute for Biophysical Chemistry, 37077 Göttingen, Germany.
2
AG Functional Cell Biology, Institute for Integrative Neuroanatomy, Charité University Medicine Berlin, Germany.
3
Faculty of Science and Engineering, Waseda University, Shinjuku-ku, Tokyo 169-8555, Japan; Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuta 4259, Yokohama 226-8503, Japan.
4
Department of Neurobiology, Max-Planck-Institute for Biophysical Chemistry, 37077 Göttingen, Germany. Electronic address: rjahn@gwdg.de.

Abstract

Vesicular glutamate transporters (VGLUTs) accumulate the neurotransmitter glutamate in synaptic vesicles. Transport depends on a V-ATPase-dependent electrochemical proton gradient (ΔμH+) and requires chloride ions, but how chloride acts and how ionic and charge balance is maintained during transport is controversial. Using a reconstitution approach, we used an exogenous proton pump to drive VGLUT-mediated transport either in liposomes containing purified VGLUT1 or in synaptic vesicles fused with proton-pump-containing liposomes. Our data show that chloride stimulation can be induced at both sides of the membrane. Moreover, chloride competes with glutamate at high concentrations. In addition, VGLUT1 possesses a cation binding site capable of binding H+ or K+ ions, allowing for proton antiport or K+ / H+ exchange. We conclude that VGLUTs contain two anion binding sites and one cation binding site, allowing the transporter to adjust to the changing ionic conditions during vesicle filling without being dependent on other transporters or channels.

PMID:
25433636
DOI:
10.1016/j.neuron.2014.11.008
[Indexed for MEDLINE]
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