EAATs
In humans (as well as in rodents), five subtypes have been identified and named EAAT1-5 (SLC1A3, SLC1A2, SLC1A1, SLC1A6, SLC1A7). Subtypes EAAT1-2 are found in membranes of glial cells (astrocytes, microglia, and oligodendrocytes) as well as in endothelial cells, whereas EAAT3-4 is located on neurons. Finally, EAAT5 is only found in the retina where it is principally localised to photoreceptors and bipolar neurons in the retina. In rodents, the orthologs for EAAT1-3 are named GLAST, GLT1, and EAAC1, respectively, whereas the acronyms EAAT4 and EAAT5 are conserved.
When glutamate is taken up into glial cells by the EAATs, it is converted to glutamine and subsequently transported back into the presynaptic neuron, converted back into glutamate, and taken up into synaptic vesicles by action of the VGLUTs. This process is named the glutamate-glutamine cycle.
The glial transporters - in particular the various splice variants of GLT-1 (EAAT2) - play the largest role (90%) in regulating extracellular glutamate concentration.
| protein | gene | tissue distribution |
|---|---|---|
| EAAT1 | SLC1A3 | glial and endothelial cells |
| EAAT2 | SLC1A2 | glial and endothelial cells |
| EAAT3 | SLC1A1 | neurons |
| EAAT4 | SLC1A6 | neurons |
| EAAT5 | SLC1A7 | retina |
| VGLUT1 | SLC17A7 | neurons |
| VGLUT2 | SLC17A6 | neurons |
| VGLUT3 | SLC17A8 | neurons |
Read more about this topic: Excitatory Amino-acid Transporter, Classes