Identification of the differentiation-associated Na+/PI transporter as a novel vesicular glutamate transporter expressed in a distinct set of glutamatergic synapses.
Glutamate transport into synaptic vesicles is a prerequisite for its regulated neurosecretion. Here we functionally identify a second isoform of the vesicular glutamate transporter (VGLUT2) that was previously identified as a plasma membrane Na+-dependent inorganic phosphate transporter (differentiation-associated Na+/P(I) transporter). Studies using intracellular vesicles from transiently transfected PC12 cells indicate that uptake by VGLUT2 is highly selective for glutamate, is H+ dependent, and requires Cl- ion. Both the vesicular membrane potential (Deltapsi) and the proton gradient (DeltapH) are important driving forces for vesicular glutamate accumulation under physiological Cl- concentrations. Using an antibody specific for VGLUT2, we also find that this protein is enriched on synaptic vesicles and selective for a distinct class of glutamatergic nerve terminals. The pathway-specific, complementary expression of two different vesicular glutamate transporters suggests functional diversity in the regulation of vesicular release at excitatory synapses. Together, the two isoforms may account for the uptake of glutamate by synaptic vesicles from all central glutamatergic neurons.
Varoqui
Helene
H
Neuroscience Center and Department of Opthalmology, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, USA.
Schäfer
Martin K H
MK
Zhu
Heming
H
Weihe
Eberhard
E
Erickson
Jeffrey D
JD
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D001692:Biological Transport / Q000502:physiology; D015415:Biomarkers / Q000737:chemistry; D001921:Brain / Q000166:cytology / Q000378:metabolism; D001923:Brain Chemistry; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism / Q000493:pharmacokinetics; D006863:Hydrogen-Ion Concentration; D008564:Membrane Potentials / Q000502:physiology; D026901:Membrane Transport Proteins; D009434:Neural Pathways / Q000166:cytology / Q000378:metabolism; D009928:Organ Specificity; D016716:PC12 Cells; D020033:Protein Isoforms / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D051381:Rats; D013116:Spinal Cord / Q000166:cytology / Q000378:metabolism; D013569:Synapses / Q000378:metabolism; D013572:Synaptic Vesicles / Q000737:chemistry / Q000378:metabolism; D014162:Transfection; D050598:Vesicular Glutamate Transport Protein 1; D050599:Vesicular Glutamate Transport Protein 2; D033921:Vesicular Transport Proteins
D000906:Antibodies; D015415:Biomarkers; D002352:Carrier Proteins; D002712:Chlorides; D026901:Membrane Transport Proteins; D020033:Protein Isoforms; C493475:Slc17a6 protein, rat; C493466:Slc17a7 protein, rat; D050598:Vesicular Glutamate Transport Protein 1; D050599:Vesicular Glutamate Transport Protein 2; D033921:Vesicular Transport Proteins; D018698:Glutamic Acid; D000255:Adenosine Triphosphate