mGluR3 Protein — Glutamate Metabotropic Receptor 3

mGluR3 Protein

<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">mGluR3 Protein — Glutamate Metabotropic Receptor 3</th>
</tr>
<tr>
<td class="label">Protein Name</td>
<td>Metabotropic Glutamate Receptor 3</td>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>GRM3</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>Q14832</td>
</tr>
<tr>
<td class="label">Molecular Weight</td>
<td>98 kDa (879 aa)</td>
</tr>
<tr>
<td class="label">Structure</td>
<td>Class C GPCR: VFT, cysteine-rich, 7-TM domains</td>
</tr>
<tr>
<td class="label">Expression</td>
<td>Brain ([cortex](/brain-regions/cortex), [hippocampus](/brain-regions/hippocampus), basal ganglia), glial cells</td>
</tr>
<tr>
<td class="label">Subcellular Localization</td>
<td>Presynaptic membrane, postsynaptic density</td>
</tr>
<tr>
<td class="label">Approach</td>
<td>Mechanism</td>
</tr>
<tr>
<td class="label">mGluR3 PAMs</td>
<td>Enhance receptor activity</td>
</tr>
<tr>
<td class="label">mGluR3 NAMs</td>
<td>Block receptor activity</td>
</tr>
<tr>
<td class="label">Gene Therapy</td>
<td>Restore expression</td>
</tr>
<tr>
<td class="label">Symptomatic Relief</td>
<td>Adjunct to antipsychotics</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">ALS</a>, <a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/alzheimer" style="color:#ef9a9a

...

mGluR3 Protein

<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">mGluR3 Protein — Glutamate Metabotropic Receptor 3</th>
</tr>
<tr>
<td class="label">Protein Name</td>
<td>Metabotropic Glutamate Receptor 3</td>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>GRM3</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>Q14832</td>
</tr>
<tr>
<td class="label">Molecular Weight</td>
<td>98 kDa (879 aa)</td>
</tr>
<tr>
<td class="label">Structure</td>
<td>Class C GPCR: VFT, cysteine-rich, 7-TM domains</td>
</tr>
<tr>
<td class="label">Expression</td>
<td>Brain ([cortex](/brain-regions/cortex), [hippocampus](/brain-regions/hippocampus), basal ganglia), glial cells</td>
</tr>
<tr>
<td class="label">Subcellular Localization</td>
<td>Presynaptic membrane, postsynaptic density</td>
</tr>
<tr>
<td class="label">Approach</td>
<td>Mechanism</td>
</tr>
<tr>
<td class="label">mGluR3 PAMs</td>
<td>Enhance receptor activity</td>
</tr>
<tr>
<td class="label">mGluR3 NAMs</td>
<td>Block receptor activity</td>
</tr>
<tr>
<td class="label">Gene Therapy</td>
<td>Restore expression</td>
</tr>
<tr>
<td class="label">Symptomatic Relief</td>
<td>Adjunct to antipsychotics</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">ALS</a>, <a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/alzheimer" style="color:#ef9a9a">Alzheimer</a>, <a href="/wiki/bipolar" style="color:#ef9a9a">Bipolar</a>, <a href="/wiki/depression" style="color:#ef9a9a">Depression</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">70 edges</a></td>
</tr>
</table>

Introduction

Mglur3 Protein — Glutamate Metabotropic Receptor 3 is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.

Overview

mGluR3 (Metabotropic Glutamate Receptor 3) is a G protein-coupled receptor that modulates both glutamatergic and GABAergic neurotransmission, playing important roles in neuroprotection, synaptic plasticity, and cognitive function[@nicoletti2011]. As a Group II metabotropic glutamate receptor (along with mGluR2), mGluR3 primarily couples to Gi/o proteins, inhibiting adenylate cyclase and reducing cAMP production.

Structure

mGluR3 shares the typical Class C GPCR architecture with distinct domains[@pin2003]:

Extracellular Domains

• Venus Fly Trap (VFT) Domain: Large extracellular glutamate-binding domain (approximately 560 aa), forms homodimers
• Cysteine-Rich Domain (CRD): Approximately 80 aa, connects VFT to transmembrane region, essential for signal transduction

Transmembrane Domains

• 7-TM Domain: Seven transmembrane helices that form the classic GPCR bundle
• Intracellular Loops: Three intracellular loops involved in G protein coupling

Intracellular Domains

• C-terminal Tail: Intracellular C-terminal tail (~100 aa) involved in signaling, trafficking, and protein interactions

The dimeric architecture of mGluR3 (and other Class C receptors) is essential for function - each protomer can bind glutamate, and the CRD transduces ligand binding to the transmembrane domain.

Normal Function

Neurotransmission Modulation[@schoepp2001]

mGluR3 serves crucial modulatory roles in synaptic transmission:

• Presynaptic Autoreceptor Function: Located on presynaptic terminals, mGluR3 senses extracellular glutamate and inhibits further glutamate release
• Presynaptic Heteroreceptor: Can also regulate release of other neurotransmitters including GABA
• Postsynaptic Signaling: Modulates [NMDA](/entities/nmda-receptor) receptor function and dendritic excitability
• Gi/o Coupling: Inhibits adenylate cyclase, reduces cAMP, activates GIRK channels

Neuroprotection

mGluR3 activation provides neuroprotective effects through multiple mechanisms:

• Anti-apoptotic Signaling: Activates PI3K/Akt pathway, promoting neuronal survival
• Excitotoxicity Reduction: Reduces excessive glutamate release, limiting excitotoxic damage
• Glial Modulation: Regulates astrocyte and microglial function
• Neurotrophic Factor Expression: Increases BDNF and GDNF expression

Synaptic Plasticity

• Modulates both [LTP](/mechanisms/long-term-potentiation) and LTD in hippocampus and cortex
• Involved in working memory and executive function
• Regulates AMPA receptor trafficking

Cognitive Function

• Critical for working memory processes
• Role in executive function and decision-making
• Modulates prefrontal cortical activity

Role in Neurodegenerative Diseases

Schizophrenia

mGluR3 is a significant therapeutic target for schizophrenia[@conn2014]:

• Genetic Risk: GRM3 variants associated with schizophrenia risk
• Expression Changes: Altered mGluR3 expression in prefrontal cortex of schizophrenic patients
• Cognitive Deficits: mGluR3 dysfunction contributes to cognitive impairment
• Therapeutic Approaches: mGluR3 positive allosteric modulators (PAMs) in development

Alzheimer's Disease

• Expression Reduction: mGluR3 expression decreased in AD brains
• Amyloid Interaction: [Aβ](/proteins/amyloid-beta) oligomers may affect mGluR3 signaling
• Neuroprotective Potential: mGluR3 agonists could protect against [Aβ](/proteins/amyloid-beta) toxicity
• Memory Function: Role in hippocampal synaptic plasticity affected in AD

Parkinson's Disease

• Dopamine-Glutamate Interaction: mGluR3 modulates dopaminergic signaling
• Levodopa-induced Dyskinesias: mGluR3 antagonists may reduce dyskinesias
• Neuroprotection: Potential to protect dopaminergic [neurons](/entities/neurons)

Depression and Anxiety

• mGluR3 Blockade: Shows antidepressant-like effects in animal models
• Mood Regulation: Involved in mood and anxiety disorders
• Fast-acting Antidepressants: mGluR2/3 antagonists (like ketamine metabolites) may contribute to rapid antidepressant effects

Amyotrophic Lateral Sclerosis

• Motor Neuron Protection: mGluR3 activation may protect motor neurons
• Glial Dysfunction: Altered mGluR3 signaling in ALS [astrocytes](/entities/astrocytes)
• Therapeutic Potential: Being investigated as a neuroprotective target

Signaling Pathways

mGluR3 activates several downstream signaling cascades:

Gi/o-cAMP Pathway: Inhibits adenylate cyclase, reduces cAMP

PI3K/Akt Pathway: Pro-survival signaling, neuroprotection

MAPK/ERK Pathway: Regulates gene expression and plasticity

[NF-κB](/entities/nf-kb) Pathway: Modulates inflammatory responses

PLC Inhibition: Reduces IP₃ and DAG production

Therapeutic Targeting

Clinical Trials

• mGluR2/3 modulators investigated for schizophrenia
• mGluR3-targeted approaches for depression
• Adjunctive therapy in AD

Animal Models

• GRM3 Knockout Mice: Show altered glutamate signaling, cognitive deficits
• Transgenic Overexpression: Protective in models of excitotoxicity
• Conditional Deletion: Reveals region-specific functions

Biomarkers

• Peripheral blood mononuclear cell GRM3 expression
• CSF mGluR3 levels as potential biomarker
• Genetic variants for patient stratification

Research Directions

Current research focuses on[@foster2017]:

• Developing selective mGluR3 modulators for CNS disorders
• Understanding mGluR2/3 heteromer pharmacology
• Biomarker development for patient selection
• Gene therapy approaches
• Understanding role in glial cells

Key Publications

Conn PJ, et al. (2009). Pharmacology and functions of metabotropic glutamate receptors. Annu Rev Pharmacol Toxicol. PMID: 18928405(https://pubmed.ncbi.nlm.nih.gov/18928405/)

Corti C, et al. (2007). Metabotropic glutamate receptors as therapeutic targets. Neuropharmacology. PMID: 17217965(https://pubmed.ncbi.nlm.nih.gov/17217965/)

Background

The study of Mglur3 Protein — Glutamate Metabotropic Receptor 3 has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.

Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.

See Also

• GRM3 Gene
• [Glutamate Receptors](/mechanisms/glutamatergic-signaling)
• [Excitotoxicity](/mechanisms/excitotoxicity-neurodegeneration)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)
• [Schizophrenia](/diseases/schizophrenia)
• [Synaptic Plasticity Pathway](/mechanisms/synaptic-dysfunction)

External Links

• [UniProt: Q14832](https://www.uniprot.org/uniprot/Q14832)
• [IUPHAR: mGluR3](https://www.guidetopharmacology.org/GRAC/LigandDisplayForward?ligandId=2975)
• [PDB: 5CGC](https://www.rcsb.org/structure/5CGC)
• [GTEx: GRM3 Expression](https://gtexportal.org/home/gene/GRM3)

References

[Nicoletti F, et al, Metabotropic glutamate receptors: from the structure to the pathophysiology of the central nervous system (2011)](https://pubmed.ncbi.nlm.nih.gov/21723945/)

[Pin JP, et al, Organization and functional expression of the family C G-protein-coupled glutamate receptors (2003)](https://pubmed.ncbi.nlm.nih.gov/12773627/)

[Schoepp DD, Unveiling the functions of presynaptic metabotropic glutamate receptors in the central nervous system (2001)](https://pubmed.ncbi.nlm.nih.gov/11561060/)

[Conn PJ, et al, Metabotropic glutamate receptors for neuropsychiatric treatment (2014)](https://pubmed.ncbi.nlm.nih.gov/23924867/)

[Foster DJ, et al, mGluR2/3 and mGluR5 as therapeutic targets for neuropsychiatric disorders (2017)](https://pubmed.ncbi.nlm.nih.gov/27543326/)