{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\n GRIN2B encodes the NR2B subunit of N‐methyl‐D‐aspartate receptors (NMDARs), which are essential components of glutamate‐gated ion channels that mediate Ca²⁺ influx and are critical for synaptic transmission and plasticity in the central nervous system. Early molecular cloning studies revealed that NR2B, along with other NR2 subunits, co‐assembles with the obligatory NR1 subunit to form heteromeric NMDARs with unique gating properties and voltage-dependent Mg²⁺ sensitivity, thereby modulating synaptic signaling."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "1"}]}, {"type": "t", "text": "\n "}]}, {"type": "t", "text": "\n "}, {"type": "p", "children": [{"type": "t", "text": "\n Subsequent investigations indicated that genetic disturbances—such as de novo mutations in GRIN2B—can alter receptor properties by disrupting the Mg²⁺ block and Ca²⁺ permeability. These perturbations have been linked to neurodevelopmental conditions including intellectual disability and epilepsy."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "2"}]}, {"type": "t", "text": "\n "}]}, {"type": "t", "text": "\n "}, {"type": "p", "children": [{"type": "t", "text": "\n In pathological contexts, NR2B‐containing receptors also play a pivotal role in excitotoxic signaling. For example, direct interaction with death-associated protein kinase 1 (DAPK1) leads to phosphorylation of the NR2B C-terminal domain, enhancing channel conductance at extrasynaptic sites and contributing to injurious Ca²⁺ influx during cerebral ischemia."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "3"}]}, {"type": "t", "text": " In Huntington’s disease models, excitotoxic death of striatal neurons is mediated through NR2B-containing NMDARs, as selective antagonism of NR2B prevents NMDA-induced cell death."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "4"}]}, {"type": "t", "text": "\n "}]}, {"type": "t", "text": "\n "}, {"type": "p", "children": [{"type": "t", "text": "\n In the mature brain, the NR2B subunit is integral to synaptic plasticity and cognitive function. Studies in the prefrontal and cingulate cortices demonstrate that blockade or genetic impairment of NR2B leads to deficits in long-term potentiation (LTP) and contextual memory formation."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "5"}]}, {"type": "t", "text": " Furthermore, developmental investigations have shown that loss of NR2B activity can alter synapse maturation, highlighting its role in preventing premature synaptic stabilization."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "6"}]}, {"type": "t", "text": "\n "}]}, {"type": "t", "text": "\n "}, {"type": "p", "children": [{"type": "t", "text": "\n In adult hippocampal neurons, NR2B is largely incorporated into triheteromeric receptor assemblies with NR2A, a configuration that fine-tunes synaptic kinetics and contributes to the balance of excitatory signaling."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "7"}]}, {"type": "t", "text": " Moreover, the dynamic regulation of NR2B levels—illustrated by studies showing that inhibition of its degradation (for instance, via decreased Cdk5-mediated proteolysis) enhances NR2B currents and improves synaptic plasticity and learning—further underscores its crucial role in cognitive function."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "9"}]}, {"type": "t", "text": "\n "}]}, {"type": "t", "text": "\n "}, {"type": "p", "children": [{"type": "t", "text": "\n Finally, direct in vivo deletion of GRIN2B in cortical and hippocampal pyramidal neurons results in deficits in both LTP and long-term depression (LTD), reductions in dendritic spine density, and impairments in multiple behavioral assays of learning and memory. These findings collectively demonstrate that proper NR2B function is vital not only for the development and maintenance of synaptic efficacy but also for protecting neurons from excitotoxic insults, with its dysfunction contributing to a spectrum of neurological disorders."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "10"}]}, {"type": "t", "text": "\n "}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "H Monyer, R Sprengel, R Schoepfer, et al. 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