N-methyl-D-aspartate receptor (GluN2A-GluN2D subunits) (NMDAR (GluN2A-D))

The N-methyl-D-aspartate (NMDA) receptor is a heterotetrameric ligand-gated ion channel that serves as a primary mediator of excitatory neurotransmission and synaptic plasticity in the central nervous system [1, 2]. It is typically composed of two obligatory glycine-binding GluN1 subunits and two regulatory glutamate-binding GluN2 subunits, which are categorized into four subtypes: GluN2A, GluN2B, GluN2C, and GluN2D [2, 7]. These subunits, encoded by the GRIN2A-D genes, confer distinct biophysical properties to the receptor, such as varying deactivation kinetics, open probability, and sensitivity to magnesium block [3, 8]. GluN2A and GluN2B are widely expressed in the adult forebrain and are essential for cognitive functions like learning and memory, whereas GluN2C and GluN2D show more restricted expression in areas such as the cerebellum and interneurons [1, 21]. Dysregulation or genetic mutations in these subunits are linked to numerous neurological and psychiatric disorders, including epilepsy, schizophrenia, Alzheimer's disease, and major depressive disorder [10, 14, 20]. Therapeutic strategies targeting these subunits include non-selective channel blockers like ketamine and memantine, as well as subunit-selective allosteric modulators aimed at achieving precise neuroprotective or cognitive-enhancing effects while minimizing side effects such as dissociation [5, 11].

Other names

Glutamate receptor ionotropic NMDA 2AGlutamate receptor ionotropic NMDA 2BGlutamate receptor ionotropic NMDA 2CGlutamate receptor ionotropic NMDA 2DGRIN2AGRIN2BGRIN2CGRIN2DNR2ANR2BNR2CNR2DGluN2 subunitsNMDA receptor type 2

Drugs targeting the GluN2A-D subunits of the NMDA receptor primarily act through non-competitive antagonism (channel blocking), positive allosteric modulation (PAM), or negative allosteric modulation (NAM) [1, 7, 11]. Channel blockers like ketamine and memantine bind within the ionophore to inhibit ion flux in a use-dependent manner [5, 17]. Subunit-selective allosteric modulators bind to distinct sites, such as the amino-terminal domain (ATD) or the ligand-binding domain (LBD) interface, to either enhance or reduce receptor activity [7, 16].