Table 1.
Classification and features of ionotropic glutamate receptors
| Family | Subunit* | Characteristics | Alternative nomenclature* |
|---|---|---|---|
|
| |||
| NMDA | GluN1 | - Glycine binding | GLUN1, NMDA-R1, NR1, GluRζ1 |
| - Obligatory subunit | |||
| GluN2A | - Primarily synaptic | GLUN2A, NMDA-R2A, NR2A, GluRε1 | |
| - Ubiquitous expression in adult brain | |||
| - High channel conductance | |||
| - High sensitivity to Mg2+ | |||
| GluN2B | - Glutamate and polyamine binding | GLUN2B, NMDA-R2B, NR2B, hNR3, GluRε2 | |
| - Primarily extrasynaptic | |||
| - Highly expressed in early development | |||
| - Primarily expressed in adult forebrain | |||
| - High channel conductance | |||
| - High sensitivity to Mg2+ | |||
| GluN2C | - Glutamate binding | GLUN2C, NMDA-R2C, NR2C, GluRε3 | |
| - Primarily expressed in adult cerebellum | |||
| - Low channel conductance | |||
| - Low sensitivity to Mg2+ | |||
| GluN2D | - Glutamate binding | GLUN2D, NMDA-R2D, NR2D, GluRε4 | |
| - Primarily extrasynaptic | |||
| - Highly expressed in early development | |||
| Low channel conductance | |||
| - Low sensitivity to Mg2+ | |||
| GluN3A | - Primarily extrasynaptic | GLUN3A, NMDA-R3A, NMDAR-L, chi-1 | |
| - Glycine binding | |||
| - Highly expressed in early development | |||
| - Low channel conductance | |||
| - Low sensitivity to Mg2+ | |||
| GluN3B | - Glycine binding | GLUN3B, NMDA-R3B | |
| - Primarily extrasynaptic | |||
| - Highly expressed in the spinal cord, pons, midbrain and medulla. | |||
| - Low channel conductance | |||
| - Low sensitivity to Mg2+ | |||
| AMPA | GluA1 | - Ca2+ permeable | GluA1,GluR1, GluRA, GluR-A, GluR-K1, HBGR1 |
| - Impermeable when coupled to edited GluA2 | |||
| - Higher conductance | |||
| GluA2 | - Q/R edited: Linear current-voltage relationship Impermeable to Ca2+ Low single-channel conductance | GluA2,GluR2, GluRB, GluR-B, GluR-K2, HBGR2 | |
| - Q/R unedited: Inwardly rectifying when blocked by endogenous intracellular polyamines Ca2+ permeable Higher conductance | |||
| GluA3 | - Ca2+ permeable | GLUA3, GluR3, GluRC, GluR-C, GluR-K3 | |
| - Impermeable when coupled to edited GluA2 | |||
| - Higher conductance | |||
| GluA4 | - Ca2+ permeable | GLUA4, GluR4, GluRD, GluR-D | |
| - Impermeable when coupled to edited GluA2 | |||
| - Higher conductance | |||
| Kainate | GluK1 | - Can form homomeric channels | GLUK5, GluR5, GluR-5, EAA3 |
| - Required for functional heteromeric receptors | |||
| - Found in cortex, striatum, hippocampus, dorsal root ganglia and cerebellum. | |||
| - Q/R edited: Linear current-voltage relationship Impermeable to Ca2+ Low single-channel conductance | |||
| - Q/R unedited: Inwardly rectifying when blocked by endogenous intracellular polyamines Ca2+ permeable Higher conductance | |||
| GluK2 | - Can form homomeric channels | GLUK6, GluR6, GluR-6, EAA4 | |
| - Required for functional heteromeric receptors | |||
| - Found in cortex, striatum, hippocampus, dorsal root ganglia, retina and cerebellum | |||
| - Q/R edited: Linear current-voltage relationship Impermeable to Ca2+ Low single-channel conductance | |||
| - Q/R unedited: Inwardly rectifying when blocked by endogenous intracellular polyamines Ca2+ permeable Higher conductance | |||
| GluK3 | - Can form homomeric channels | GLUK7, GluR7, GluR-7, EAA5 | |
| - Required for functional heteromeric receptors | |||
| - Found in cortex, hippocampus, retina and cerebellum. | |||
| GluK4 | - Only forms heteromeric receptors | GLUK1, KA1, KA-1, EAA1 | |
| - Primarily located at hippocampal CA3 and dentate granule neurons and purkinje cells in cerebellum | |||
| GluK5 | - Only forms heteromeric receptors | GLUK2, KA2, KA-2, EAA2 | |
| - Found in cortex, hippocampus, retina and cerebellum. | |||
*Collingridge et al., 2009.