Identification and characterization of the vesicular GABA transporter.
Synaptic transmission involves the regulated exocytosis of vesicles filled with neurotransmitter. Classical transmitters are synthesized in the cytoplasm, and so must be transported into synaptic vesicles. Although the vesicular transporters for monoamines and acetylcholine have been identified, the proteins responsible for packaging the primary inhibitory and excitatory transmitters, gamma-aminobutyric acid (GABA) and glutamate remain unknown. Studies in the nematode Caenorhabditis elegans have implicated the gene unc-47 in the release of GABA. Here we show that the sequence of unc-47 predicts a protein with ten transmembrane domains, that the gene is expressed by GABA neurons, and that the protein colocalizes with synaptic vesicles. Further, a rat homologue of unc-47 is expressed by central GABA neurons and confers vesicular GABA transport in transfected cells with kinetics and substrate specificity similar to those previously reported for synaptic vesicles from the brain. Comparison of this vesicular GABA transporter (VGAT) with a vesicular transporter for monoamines shows that there are differences in the bioenergetic dependence of transport, and these presumably account for the differences in structure. Thus VGAT is the first of a new family of neurotransmitter transporters.
McIntire
S L
SL
Graduate Programs in Neuroscience, Cell Biology and Biomedical Sciences, Department of Neurology, UCSF School of Medicine, San Francisco, California 94143-0435, USA.
Reimer
R J
RJ
Schuske
K
K
Edwards
R H
RH
Jorgensen
E M
EM
D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000378:metabolism; D017173:Caenorhabditis elegans / Q000235:genetics / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D050485:GABA Plasma Membrane Transport Proteins; D015801:Helminth Proteins / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D009154:Mutation; D009474:Neurons / Q000378:metabolism; D027361:Organic Anion Transporters; D016716:PC12 Cells; D051381:Rats; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013572:Synaptic Vesicles / Q000378:metabolism; D050495:Vesicular Inhibitory Amino Acid Transport Proteins; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D050485:GABA Plasma Membrane Transport Proteins; D015801:Helminth Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D027361:Organic Anion Transporters; D011994:Recombinant Proteins; D050495:Vesicular Inhibitory Amino Acid Transport Proteins; C493420:unc-47 protein, C elegans; D005680:gamma-Aminobutyric Acid