Glutamate transporter types

The uptake process is driven by the electrochemical gradients across the cell membrane. Sodium is required for glutamate binding while potassium is required for net transport 

To understand glutamatergic neurotransmission it is necessary to obtain preeise information on the localizations and densities of glutamate transporters because they represent one of the major determinants of how glutamate diffuses from the point of release (Fig. 1). Sinee the cloning of the first glutamate transporters in 1992, a substantial amount of information on transporter distribution has been collected. 

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Somogyi, J., Baude, A., Omori, Y. et al. GABAergic basket cells expressing cholecysokinin contain vesicular glutamate transporter type 3 (VGLUT3). Eur J. Neurosci. 19 552-569,... 

Ma K., Zheng S., and Zuo Z. (2006). The transcription factor regulatory factor XI increases the expression of neuronal glutamate transporter type 3. J. Biol. Chem. 281 21250-21255. 

Vinatier J., Herzog E., Plamont M. A., Wojcik S. M., Schmidt A., Brose N., Daviet L., El Mestikawy S., and Giros B. (2006). Interaction between the vesicular glutamate transporter type 1 and endophilin Al, a protein essential for endocytosis. J. Neurochem. 97 1111-1125. 

Somogyi, J., Baude, A., Omori, Y., Shimizu, H., El Mestikawy, S., Fukaya, M., Shigemoto, R., Watanabe, M., and Somogyi, P. (2004). GABAergic basket cells expressing cholecystokinin contain vesicular glutamate transporter type 3 (VGLUT3) in their synaptic terminals in hippocampus and isocortex of the rat. Eur.J. Neurosci. 19, 552-569. 

The neurotransmitter phenotype, (i.e., what type of neurotransmitter is stored and ultimately will be released from the synaptic bouton) is determined by the identity of the neurotransmitter transporter that resides on the synaptic vesicle membrane. Although some exceptions to the rule may exist all synaptic vesicles of a given neuron normally will express only one transporter type and thus will have a dehned neurotransmitter phenotype (this concept is enveloped in what is known as Dale s principle see also Reference 19). To date, four major vesicular transporter systems have been characterized that support synaptic vesicle uptake of glutamate (VGLUT 1-3), GABA and glycine (VGAT), acetylcholine (VAChT), and monoamines such as dopamine, norepinephrine, and serotonin (VMAT 1 and 2). Vesicles that store and release neuropeptides do not have specific transporters to load and concentrate the peptides but, instead, are formed with the peptides already contained within. 

Yamada H, Yatsushiro S, Yamamoto A, Hayashi M, Nishi T, Futai M, Yamaguchi A. Moriyama Y (1997) Functional expression of a GLT-1 type Na -dependent glutamate transporter in rat pinealocytes. J Neurochem 69 1491-1498. 

Harkany, T., Hartig, W., Berghuis, R, et al. (2003) Complementary distribution of type 1 cannabinoid receptors and vesicular glutamate transporter 3 in basal forebrain suggests input-specific retrograde signaling by cholinergic neurons. Eur. J. Neurosci. 18 (7), 1979-1992. 

GABAAy2 GABA type-A receptor subunit y2, GADglutamic acid decarboxylase, rGATvesicular GABA transporter, vG/ t2vesicular glutamate transporter 2... 

Synaptic vesicles isolated from brain exhibit four distinct vesicular neurotransmitter transport activities one for monoamines, a second for acetylcholine, a third for the inhibitory neurotransmitters GABA and glycine, and a fourth for glutamate [1], Unlike Na+-dependent plasma membrane transporters, the vesicular activities couple to a proton electrochemical gradient (A. lh+) across the vesicle membrane generated by the vacuolar H+-ATPase ( vacuolar type proton translocating ATPase). Although all of the vesicular transport systems rely on ApH+, the relative dependence on the chemical and electrical components varies (Fig. 1). The... 

J Liaw, Y Rojanasakul, JR Robinson. (1991). The effect of charge type and charge density on corneal transport of lysine and glutamic acid—Evidence for active transport. Pharm Res 8(Suppl) S-130. 

Neurotransmitter transporters There are probably at least five types of transport protein specific for glutamate, acetylcholine, catecholamines, glycine/GABA and ATP. The type of transporter contributes to determining the transmitter specificity of a synapse. 

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