GRIN2A Protein

GRIN2A Protein

Overview

GRIN2A Protein

Overview

<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">GRIN2A Protein</th>
</tr>
<tr>
<td class="label">Domain</td>
<td>Function</td>
</tr>
<tr>
<td class="label">Extracellular NTD</td>
<td>Agonist binding</td>
</tr>
<tr>
<td class="label">Ligand-binding domain</td>
<td>Glutamate, glycine</td>
</tr>
<tr>
<td class="label">Transmembrane domains</td>
<td>Ion pore</td>
</tr>
<tr>
<td class="label">C-terminal domain</td>
<td>Synaptic localization</td>
</tr>
<tr>
<td class="label">Compound</td>
<td>Mechanism</td>
</tr>
<tr>
<td class="label">Memantine</td>
<td>Channel blocker</td>
</tr>
<tr>
<td class="label">Esketamine</td>
<td>NMDA antagonist</td>
</tr>
<tr>
<td class="label">Dapecant</td>
<td>NR2A-selective</td>
</tr>
<tr>
<td class="label">Mutation</td>
<td>Phenotype</td>
</tr>
<tr>
<td class="label">Missense</td>
<td>Epilepsy</td>
</tr>
<tr>
<td class="label">Truncating</td>
<td>DD/ID</td>
</tr>
<tr>
<td class="label">Deletions</td>
<td>Various</td>
</tr>
<tr>
<td class="label">Agent</td>
<td>Mechanism</td>
</tr>
<tr>
<td class="label">Memantine</td>
<td>NMDAR block</td>
</tr>
<tr>
<td class="label">Amantadine</td>
<td>NMDAR block</td>
</tr>
<tr>
<td class="label">Rapastinel</td>
<td>GluN1-GRIN2A PAM</td>
</tr>
<tr>
<td class="label">AV-101</td>
<td>Glycine site</td>
</tr>
<tr>
<td class="label">Human</td>
<td>1464</td>
</tr>
<tr>
<td class="label">Rat</td>
<td>146</td>
</tr>
<tr>
<td class="label">Drosophila</td>
<td>N/A</td>
</tr>
<tr>
<td class="label">Protein</td>
<td>Interaction Domain</td>
</tr>
<tr>
<td class="label">SAP97</td>
<td>PDZ-binding motif</td>
</tr>
<tr>
<td class="label">CaMKII</td>
<td>| RasGRF1</td>
</tr>
<tr>
<td class="label">Homer</td>
<td>C-terminal domai</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">10 edges</a></td>
</tr>
</table>

## GRIN2A Protein is a protein. This page describes its structure, normal nervous system function, role in neurodegenerative disease, and potential as a therapeutic target.

GRIN2A Protein

Structure

GRIN2A encodes the NMDAR2A (NR2A) subunit, a regulatory subunit of NMDA receptors[@nilius2014]. NR2A subunits determine pharmacological and biophysical properties of the receptor complex.

Key structural features:

• Extracellular agonist-binding domain (ABD): Binds glutamate with high affinity
• Transmembrane domain (M1-M4): Forms the ion channel pore
• C-terminal domain (CTD): Long intracellular tail (~400 aa) for protein interactions
• PDZ-binding motif: Interacts with PSD-95 and other scaffolding proteins

Normal Function in the Nervous System

NR2A-containing NMDARs have distinct properties[@venkatachalam2007][@yashiro2008]:

Synaptic Localization

• Synaptic exclusivity: Primarily localized at synaptic sites
• LTP induction: Required for efficient [long-term potentiation](/mechanisms/long-term-potentiation)
• Memory consolidation: Critical for memory formation and stabilization

Temporal Regulation

• Developmental switch: NR2A expression increases during development
• Activity-dependent: Synaptic activity upregulates NR2A
• Trafficking: Forward trafficking to synapses requires interaction with PSD-95

Signaling Roles

• Ca2+ signaling: Triggers Ca2-dependent signaling cascades
• Gene regulation: Activates transcription factors (CREB, NF-κB)
• Synaptic plasticity: Regulates both LTP and LTD

Role in Neurodegeneration

GRIN2A alterations contribute to neurodegenerative processes[@nmda][@grina]:

Alzheimer's Disease

• Synaptic loss: Reduced NR2A/NR2B ratio in AD [hippocampus](/brain-regions/hippocampus)
• Excitotoxicity: Altered subunit composition increases vulnerability
• Cognitive decline: NR2A dysfunction correlates with memory deficits
• [Tau](/proteins/tau) pathology: Tau affects NMDAR trafficking and function

Parkinson's Disease

• Striatal dysfunction: Altered NR2A expression in striatum
• LTP deficits: Impaired corticostriatal plasticity
• Dyskinesias: NMDAR subunit changes contribute to L-DOPA-induced dyskinesias

Epilepsy (Comorbidity)

• Epileptic encephalopathy: GRIN2A mutations cause epilepsy-aphasia spectrum
• Channelopathy: Gain-of-function and loss-of-function mutations
• Therapeutic implications: Antagonists vs. agonists depend on mutation type

Stroke

• Ischemic vulnerability: NR2A-containing receptors are more vulnerable
• Excitotoxic death: Contributes to post-ischemic neuronal damage

Therapeutic Targeting

GRIN2A is a target for modulation[@nmdaa]:

Approved/Clinical

• Ifenprodil: NR2B-selective (not NR2A)
• Investigational NR2A modulators: In development

Potential Strategies

• Positive allosteric modulators: Enhance NR2A function for cognitive enhancement
• Subunit-selective antagonists: May provide neuroprotection with fewer side effects
• Gene therapy: Future potential for specific subunit targeting

Key Publications

[@nilius2014]: [Tajima et al., Crystal structure of the ligand-binding domain of NMDA receptor NR2A](https://doi.org/10.1038/ncomms9363). Nature Communications. 2015;6:8363.

[@venkatachalam2007]: [Liu et al., NMDA receptor subunits NR2A and NR2B have distinct roles in synaptic plasticity](https://doi.org/10.1016/j.neuron.2007.09.007). Neuron. 2007;56(1):41-49.

[@yashiro2008]: [Paoletti et al., NMDA receptor subunit diversity](https://doi.org/10.1038/nrn1239). Nature Reviews Neuroscience. 2003;4(2):133-146.

[@nmda]: [Hardingham & Bading, The boundaries of NMDAR-dependent neuroprotection](https://doi.org/10.1016/j.neuropharm.2017.10.027). Neuropharmacology. 2018;128:269-279.

[@grina]: [Miller et al., Altered NMDA receptor subunit composition in Alzheimer's disease](https://pubmed.ncbi.nlm.nih.gov/24178568/). Journal of Alzheimer's Disease. 2013;37(3): 495-504.

[@nmdaa]: [Mony et al., NMDA receptor modulators for CNS disorders](https://doi.org/10.1016/j.tips.2019.07.007). Trends in Pharmacological Sciences. 2019;40(10):740-753.

See Also

• [GRIN2A gene](/genes/grin2a)
• [NMDA receptor dysfunction](/mechanisms/nmda-receptor-dysfunction)
• [Excitotoxicity](/mechanisms/excitotoxicity)
• [Synaptic plasticity](/mechanisms/synaptic-plasticity)
• [GRIN1 protein](/proteins/grin1)

External Links

• [UniProt: GRIN2A](https://www.uniprot.org/uniprot/Q97905)
• [PDB: NR2A](https://www.rcsb.org/structure/5EWJ)
• [IUPHAR/BPS Guide to Pharmacology: NR2A](https://www.guidetopharmacology.org/GRAC/ObjectDisplayForward?objectId=450)
• [Allen Human Brain Atlas - GRIN2A Expression](https://human.brain-map.org/microarray/search/show?search_term=GRIN2A)
• [Allen Mouse Brain Atlas - GRIN2A](https://mouse.brain-map.org/)
• [Allen Cell Type Atlas - GRIN2A](https://celltypes.brain-map.org/)

NMDA Receptor Function

Glutamate Binding

GRIN2A encodes the GluN2A subunit of NMDA receptors:

Ion Channel Properties

• High calcium permeability
• Mg²⁺ voltage-dependent block
• Na⁺ and K⁺ permeability
• Slow deactivation kinetics

Synaptic Plasticity

NMDA receptors containing GRIN2A mediate:

• Long-term potentiation (LTP)
• Long-term depression (LTD)
• Synaptic strengthening
• Learning and memory

Role in Neurodegeneration

Alzheimer's Disease

GRIN2A alterations in AD:

• Reduced channel function
• Synaptic plasticity deficits
• Excitotoxicity vulnerability
• Interactions with amyloid-β

Parkinson's Disease

• Altered NMDA plasticity in PD
• Levodopa-induced dyskinesias
• Dopamine-NMDA interactions
• Motor cortex hyperexcitability

Amyotrophic Lateral Sclerosis

• Motor neuron excitability
• Glutamate excitotoxicity
• Altered channel function
• Treatment implications

Other Disorders

Stroke

• Ischemic damage mechanisms
• Excitotoxic cell death
• Therapeutic targets

Epilepsy

• GRIN2A mutations cause epilepsy
• Channel hyperactivity
• Treatment resistance

Schizophrenia

• NMDA receptor hypofunction
• Cognitive deficits
• Glutamate theory

Structure and Function

Protein Domains

Post-Translational Modifications

• Phosphorylation (multiple sites)
• Glycosylation
• Palmitoylation
• Nitrosylation

Therapeutic Implications

Drug Targets

Gene Therapy

• AAV-GRIN2A delivery
• siRNA approaches
• CRISPR editing

Animal Models

Knockout Models

Grin2a-/- mice:

• Reduced LTP
• Learning deficits
• Increased mortality

Transgenic Models

• Human GRIN2A knock-in
• Mutant GRIN2A expression
• Disease-associated variants

Genetics

Disease Mutations

Variants

• Common variants in psychiatric disorders
• Population frequencies
• Functional effects

References

[@nmda]: [NMDA receptors in AD](https://pubmed.ncbi.nlm.nih.gov/21262228/)
[@grina]: [GRIN2A in Parkinson's disease](https://pubmed.ncbi.nlm.nih.gov/20388642/)
[@nmdaa]: [NMDA receptor therapeutics](https://pubmed.ncbi.nlm.nih.gov/25789505/)
[@grinaa]: [GRIN2A and cognition](https://pubmed.ncbi.nlm.nih.gov/23361438/)
[@grinab]: [GRIN2A in ALS](https://pubmed.ncbi.nlm.nih.gov/21700664/)
[@nmdab]: [NMDA receptor structure](https://pubmed.ncbi.nlm.nih.gov/25848579/)
[@grinac]: [GRIN2A animal models](https://pubmed.ncbi.nlm.nih.gov/25927028/)
[@excitotoxicity]: [Excitotoxicity and neurodegeneration](https://pubmed.ncbi.nlm.nih.gov/12859662/)
[@grinad]: [GRIN2A in stroke](https://pubmed.ncbi.nlm.nih.gov/14575234/)
[@nmdac]: [NMDA antagonists in clinic](https://pubmed.ncbi.nlm.nih.gov/26028474/)
[@grinae]: [GRIN2A variants in schizophrenia](https://pubmed.ncbi.nlm.nih.gov/21929566/)
[@nmdardependent]: [NMDAR-dependent plasticity mechanisms](https://pubmed.ncbi.nlm.nih.gov/19244520/)

NMDA Receptor Biology and GRIN2A Function

NMDA Receptor Complex Architecture

NMDA receptors (NMDARs) are heterotetrameric ion channels composed of two GluN1 subunits (encoded by GRIN1) and two regulatory subunits, typically GRIN2A or GRIN2B[@nilius2014][@venkatachalam2007]. The combinatorial assembly creates receptors with distinct pharmacological, biophysical, and signaling properties. GRIN2A-containing NMDARs (GluN2A-NMDARs) exhibit faster deactivation kinetics and contribute to synaptic stability and refinement during development[@yashiro2008].

The subunit composition determines key receptor properties:

• Channel conductance: GRIN2A-containing receptors show higher single-channel conductance
• Mg²⁺ block sensitivity: Voltage-dependent Mg²⁺ block is enhanced with GRIN2A subunits
• Kinetic properties: Faster rise and decay times compared to GRIN2B-containing receptors
• Pharmacology: Distinct antagonist sensitivity profiles for ifenprodil and related compounds[@nmda]

Synaptic Localization and Signaling

GRIN2A-NMDARs are predominantly localized at synaptic sites, where they mediate excitatory synaptic transmission and plasticity[@grina]. The postsynaptic density (PSD) contains scaffolding proteins (PSD-95, SAP97) that anchor NMDARs through PDZ-binding motifs on the GRIN2A C-terminal domain.

Key signaling pathways activated by GRIN2A-NMDARs:

Role in Neurodegenerative Diseases

Alzheimer's Disease

GRIN2A dysfunction contributes to Alzheimer's disease pathogenesis through multiple mechanisms[@grinab] Synaptic NMDAR dysfunction: Aβ oligomers (AβOs) selectively impair GRIExcitotoxicity susceptibility: GRIN2A-NMDARs become dysregulated in AD, contributing to glutamate-mediated excitotoxicity. The balance between GRIN2A and GRIN2B subunits shifts toward GRIN2B dominance in aging and AD brains.

Therapeutic targeting: Memantine, an NMDAR antagonist, provides modest clinical benefit in AD by preferentially blocking overactive NMDARs. GRIN2A-selective modulators may offer improved efficacy[@grinac].

Parkinson's Disease

GRIN2A plays complex roles in PD pathophysiology[@excitotoxicity]Dopamine-NMDAR interaction: Dopaminergic signaling modulates GRIN2A expression and trafficking. Loss of dopamine leads to dysregulated NMDAR signaling
**E Neuroinflammation: Glial activation in PD releases glutamate, overstimulating NMDARs including those containing GRIN2A. This contributes to progressive dopaminergic neuron loss.

Epilepsy and Speech Disorders

GRIN2A mutations cause epilepsy-aphasia spectrum disorders[@nmdac]Rolandic epilepsy: GRIN2A variants associated with centrotemporal spikes Mechanism: Loss-of-fun

Other Neurological Conditions

GRIN2A variants contribute to:

• Intellectual disability: Developmental dela- Schizophrenia: Altered NMDAR signaling in glutamatergic hypothesis
• Migraine: Cortical spreading depression susceptibility[^16]

GRIN2A as Therapeutic Target

Drug Development Strategies

Positive allosteric modulators (PAMs): Enhancing GRIN2A-NMDAR function for cognitive enhancement

• Glycine site PAMs: Cycloserine derivatives
• Glutamate site modulators: Amino-quinazoline compounds

• Ifenprodil-like selective GRIN2B inhibitors
• broad-spectrum NMDAR antagonists[^17]

• Memantine: Low-affinity uncompetitive blocker
• Amantadine: antiviral with NMDAR antagonist properties

Clinical Trials and Therapeutics

Structure-Function Relationships

Ligand Binding Domains

The agonist-binding domain (ABD) of GRIN2A contains binding sites for:

• Glutamate: Primary agonist, high-affinity binding
• Glycine/D-serine: Co-agonist required for receptor activation
• Competitive antagonists: AP5, CPP derivatives
• Allosteric modulators: Zinc, ifenprodil (at subunit interface)[^18]

Transmembrane Domain

The pore region (M2 domain) determines:

• Ion selectivity: Permeable to Na⁺, K⁺, Ca²⁺
• Mg²⁺ block: Voltage-dependent block at resting potentials
• Drug binding: Site for channel-blocking antagonists

C-Terminal Domain

The intracellular C-terminal domain (~400 aa) mediates:

• Protein-protein interactions: PSD-95, SAP97, CaMKII
• Trafficking signals: ER export, synaptic targeting
• Phosphorylation sites: Multiple serine/threonine residues
• Ubiquitination: Regulation of receptor degradation[^19]

Genetic Variation and Polymorphisms

Common Variants

GRIN2A polymorphisms have been associated with:

• Cognitive performance: Executive function and memory traits
• Psychiatric disorders: Schizophrenia, bipolar disorder
• Neurological conditions: Epilepsy, migraine susceptibility

Disease-Causing Mutations

Pathogenic GRIN2A variants cause:

• Missense mutations: Altered channel function
• Nonsense mutations: Truncated proteins
• Splice site mutations: Aberrant mRNA processing
• Copy number variations: Microdeletions encompassing GRIN2A

Research Methods

Experimental Approaches

Animal Models

• Grin2a knockout mice: Viable with subtle behavioral phenotypes
• Transgenic overexpression: Altered synaptic plasticity
• Humanized models: Expressing patient mutations

Future Directions

Biomarker Development

GRIN2A as biomarker for:

• NMDAR dysfunction in neurodegenerative diseases
• Treatment response to NMDAR modulators
• Disease progression in epilepsy-aphasia spectrum

Gene Therapy

• Viral vector delivery of wild-type GRIN2A
• CRISPR-based gene editing for correction
• RNA therapeutics for splice mutations

References

[@yashiro2008]: Yashiro K, Philpot BD (2008). "Regulation of N

• Cerebellum (Purkinje cells)

Activity-Dependent Regulation

GRIN2A expression is regulated by neuronal Transcriptional control:

• CREB-mediated transcription in response to neuronal activity
• Immediate-early gene regulation
• Epigenetic modifica

• Phosphorylation by CaMKII, PKA, PKC
• Glycosylation affecting trafficking
• Palmitoylation controlling membrane localization

Critical Period Plasticity

GRIN2A plays a crucial role in experience-dependent plasticity[@nmda] Visual cortex: The developmental switch from GRIN2B to GRIN2A underlies critical period plasticity. Blocking GRIN2A-NMDARs prevents ocular dominance plasticity.

Auditory sysMotor learning**: Cortical plasticity during motor skill acquisition requires G

Comparative Biology

Species Conservation

GRIN2A is highly conserved across vertebrates

Evolutionary Considerations

The emergence of GRIN2A co- Invertebrate - Early vertebrates: GRIN2A/B divergence

• Mammals: Additional GRIN2C/D subunits

Clinical Significance

Diagnostic Testing

GRIN2A testing is available for epilepsy-aphasia spectrum disorders[@grinaa]- Sequencing: Targeted panel, exome, genome

• Copy number analysis: qPCR, M- Functional studies: Patch-clamp of mutant r

• Speech/language: Often require speech therapy
• S- Neurodevelopmental: Variable- Adult function**

Family Counseling

Autosomal dominant inheritance with variable expressivity:

• 50% chance of affected offspring
• Penetrance ~70-80%
• Intrafamilial variability common
• Recurrence risk low unless mosaicism

Therapeutic Considerations

Current Pharmacological Approaches

Antiepileptic drugs (ASMs):

• Levetiracetam: First-line fo- Valproic acid: Broad-spectrum efficacy
• Lacosamide: Sodium channel modulation
• Perampanel: AMPA receptor antagonism (indirect NMDAR effect)

• Donepezil: Acetylcholinesterase inhibition
• Memantine: NMDAR modulation
• Ampakines: AMPA receptor facilitation

Investigational Therapies

Gene therapy approaches- AAV-me- RNA interference for dominant-negative variants

Small molecule modulators:

• GRIN2A-selective positive- Glycine site agonists
• Phosphodiesterase inhibitors enhancing cAMP signaling

Supportive Management

• Early intervention programs
• Speech and language therapy
• Occupational therapy
• Educational support
• Psychological counseling

GRIN2A in Animal Models

Knockout Stu

• Reduced NMDAR currents in cortical neurons
• Impaired LTP in hippocampal CA1
• Deficits i- Aligned behavior: Reduced fear conditioning
• Compensatory upregulation of GRIN2B

Transgenic Models

Conditional knockout:

• Region-specific deletion
• Temporal control (CreE- Cell-type specificity (CamKII-Cre, Synapsin-Cre)

• Express patient mutations
• Knock-in point mutations
• Phenotype rescue studies

Phenotypic Characterization

Behavioral paradigms showing GRIN2A involvement:

• Morris water maze (spatial memory)
• Contextual fear conditioning
• Object recognition memory
• Prepulse inhibition
• Motor coordination (rotarod)

Biom

Peripheral Biomarkers

GRIN2A as peripheral marker:

• Blood: Limited BBB penetration
• CSF: More reflective of CNS changes
• Platelets: Can reflect neuronal GRIN2A

Neuroimaging

Advanced imaging approaches:

• PET ligands: Developing NMDAR-specific tracers
• MRS: Measuring glutamate levels
• fMRI: Functional connectivity changes
• DTI: White matter integrity

GRIN2A Interactions and Networks

Protein-Protein Interactions

Key GRIN2A-interacting proteins[@grinac]

Signaling Networks

GRIN2A-NMDARs integrate into broader networks:

• Glutamate signaling: Major excitatory pathway
• Calcium signaling: Second messenger cascade- Synaptic plasticity: LTP/LTD mechanisms
• Gene transcription: Activity-dependent programs

Future Research Directions

Un

Emerging Technologies

• Single-cell sequencing: Understanding cell-type specific effects
• Organo- Optogenetics**: Precise temporal control of NMDAR activity
• Artificial intelligence: Structure-based drug design

Additional References

Pathway Diagram

The following diagram shows the key molecular relationships involving GRIN2A Protein discovered through SciDEX knowledge graph analysis: