Identification of a vesicular glutamate transporter that defines a glutamatergic phenotype in neurons.
Glutamate is the major excitatory neurotransmitter in the mammalian central nervous system. Synaptic vesicles are loaded with neurotransmitter by means of specific vesicular transporters. Here we show that expression of BNPI, a vesicle-bound transporter associated with sodium-dependent phosphate transport, results in glutamate uptake by intracellular vesicles. Substrate specificity and energy dependence are very similar to glutamate uptake by synaptic vesicles. Stimulation of exocytosis--fusion of the vesicles with the cell membrane and release of their contents--resulted in quantal release of glutamate from BNPI-expressing cells. Furthermore, we expressed BNPI in neurons containing GABA (gamma-aminobutyric acid) and maintained them as cultures of single, isolated neurons that form synapses to themselves. After stimulation of these neurons, a component of the postsynaptic current is mediated by glutamate as it is blocked by a combination of the glutamate receptor antagonists, but is insensitive to a GABA(A) receptor antagonist. We conclude that BNPI functions as vesicular glutamate transporter and that expression of BNPI suffices to define a glutamatergic phenotype in neurons.
Takamori
S
S
Department of Neurobiology, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany.
Rhee
J S
JS
Rosenmund
C
C
Jahn
R
R
D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D027322:Amino Acid Transport System X-AG; D000818:Animals; D017173:Caenorhabditis elegans; D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D050485:GABA Plasma Membrane Transport Proteins; D018698:Glutamic Acid / Q000378:metabolism*; D006801:Humans; D008564:Membrane Potentials; D008565:Membrane Proteins / Q000378:metabolism; D026901:Membrane Transport Proteins; D009474:Neurons / Q000378:metabolism*; D027361:Organic Anion Transporters; D010641:Phenotype; D051381:Rats; D050608:Sodium-Phosphate Cotransporter Proteins; D027981:Symporters; D013569:Synapses; D013572:Synaptic Vesicles / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured; D050495:Vesicular Inhibitory Amino Acid Transport Proteins; D014981:Xenopus; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D018528:ATP-Binding Cassette Transporters; D027322:Amino Acid Transport System X-AG; D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D050485:GABA Plasma Membrane Transport Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D027361:Organic Anion Transporters; D050608:Sodium-Phosphate Cotransporter Proteins; D027981:Symporters; D050495:Vesicular Inhibitory Amino Acid Transport Proteins; C493420:unc-47 protein, C elegans; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid