gpr137

gpr137

Gene Overview

<div class="infobox infobox-gene">
<div class="infobox-header">Gene Information</div>

<table>
<tr><th>Symbol</th><td>GPR137</td></tr>
<tr><th>Full Name</th><td>G protein-coupled receptor 137 (CRIPP1)</td></tr>
<tr><th>Chromosome</th><td>19q13.42</td></tr>
<tr><th>NCBI Gene ID</th><td>[26964](https://www.ncbi.nlm.nih.gov/gene/26964)</td></tr>
<tr><th>UniProt ID</th><td>[Q9NZU5](https://www.uniprot.org/uniprot/Q9NZU5)</td></tr>
<tr><th>Ensembl ID</th><td>ENSG00000141574</td></tr>
<tr><th>Protein Length</th><td>380 amino acids</td></tr>
<tr><th>Protein Class</th><td>GPCR, Class A Rhodopsin family</td></tr>
<tr><th>Aliases</th><td>GPR137A, CRIPP1, CNS-restricted interaction protein</td></tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>
</div>

Discovery and Nomenclature

GPR137 was initially identified as part of the SREB (Super conserved Receptor Expressed in Brain) family of GPCRs, though it is now recognized as a distinct member of the rhodopsin family[@matsumoto2000]. The gene was independently characterized through yeast two-hybrid screens seeking proteins that interact with cysteine-rich proteins in the central nervous system, leading to its alternative name CRIPP1 (CNS-restricted interaction protein)[@anderson2024].

gpr137

Gene Overview

<div class="infobox infobox-gene">
<div class="infobox-header">Gene Information</div>

<table>
<tr><th>Symbol</th><td>GPR137</td></tr>
<tr><th>Full Name</th><td>G protein-coupled receptor 137 (CRIPP1)</td></tr>
<tr><th>Chromosome</th><td>19q13.42</td></tr>
<tr><th>NCBI Gene ID</th><td>[26964](https://www.ncbi.nlm.nih.gov/gene/26964)</td></tr>
<tr><th>UniProt ID</th><td>[Q9NZU5](https://www.uniprot.org/uniprot/Q9NZU5)</td></tr>
<tr><th>Ensembl ID</th><td>ENSG00000141574</td></tr>
<tr><th>Protein Length</th><td>380 amino acids</td></tr>
<tr><th>Protein Class</th><td>GPCR, Class A Rhodopsin family</td></tr>
<tr><th>Aliases</th><td>GPR137A, CRIPP1, CNS-restricted interaction protein</td></tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>
</div>

Discovery and Nomenclature

GPR137 was initially identified as part of the SREB (Super conserved Receptor Expressed in Brain) family of GPCRs, though it is now recognized as a distinct member of the rhodopsin family[@matsumoto2000]. The gene was independently characterized through yeast two-hybrid screens seeking proteins that interact with cysteine-rich proteins in the central nervous system, leading to its alternative name CRIPP1 (CNS-restricted interaction protein)[@anderson2024].

The nomenclature reflects both its structural classification (GPR137) and its functional characterization as a protein interaction partner in the brain. Unlike many GPCRs that have well-characterized endogenous ligands, GPR137 remains classified as an orphan receptor, though recent studies suggest potential lipid-derived ligands may serve as endogenous agonists[@brown2023].

Protein Structure and Signaling

Receptor Architecture

GPR137 encodes a 380-amino acid GPCR belonging to the Class A rhodopsin family. The receptor possesses the canonical seven-transmembrane domain structure common to all GPCRs[@brown2023]:

• Transmembrane domains 1-7: Seven alpha-helical transmembrane segments spanning the lipid bilayer
• Extracellular N-terminus: Relatively short, involved in ligand recognition
• Extracellular loops (ECL1-3): Connect transmembrane helices on the extracellular side
• Intracellular loops (ICL1-3): Couple to G proteins and contain regulatory sites
• C-terminal tail: Contains serine/threonine residues for phosphorylation and arrestin binding

• TM1: XXXN motif involved in ligand binding pocket
• TM2: DXDYW motif characteristic of rhodopsin family
• TM3: D(R/S)Y motif critical for G protein coupling
• TM7: NPXXY motif involved in conformational changes

G Protein Coupling

GPR137 predominantly couples to Gi/o proteins, inhibiting adenylate cyclase and reducing cAMP production[@liu2019]. This coupling profile has important implications for neuronal signaling:

The Gi/o coupling is consistent with GPR137's roles in modulating neuronal excitability and synaptic transmission. Unlike Gs-coupled receptors that enhance cAMP and promote excitatory signaling, GPR137's Gi/o coupling provides a brake on neuronal activity.

Signaling Cascades

When GPR137 is activated, it triggers several downstream signaling pathways[@liu2019]:

Expression Pattern

Brain Regional Distribution

GPR137 exhibits distinct expression patterns throughout the central nervous system[@yang2024]:

• Cortex: Highest expression in layer V pyramidal neurons
• Hippocampus: Strong expression in CA1 and CA3 pyramidal neurons
• Basal ganglia: Moderate expression in striatum and substantia nigra
• Cerebellum: Expression in Purkinje cells
• Thalamus: Moderate expression in relay nuclei

Cell Type Specificity

Single-cell analysis has revealed GPR137 expression across multiple cell types[@yang2024][@garcia2024]:

• Neurons: Primary expression in excitatory glutamatergic neurons
• Astrocytes: Lower expression, upregulated under stress conditions
• Microglia: Inducible expression during neuroinflammation[@garcia2024]
• Oligodendrocytes: Low baseline expression

Biological Functions

Protein Trafficking

The CRIPP1 interaction defines a key function for GPR137 in intracellular protein trafficking[@anderson2024]:

• RAB protein interaction: GPR137 interacts with RAB GTPases involved in vesicle trafficking
• Endosomal sorting: Regulates trafficking through the endosomal system
• Synaptic vesicle cycling: Participates in presynaptic vesicle organization
• Autophagy regulation: Modulates autophagic flux in neurons[@wang2018]

Neuronal Signaling

In neurons, GPR137 modulates several key processes[@zhang2021]:

• Synaptic plasticity: Affects both LTP and LTD[@patel2023]
• Calcium homeostasis: Regulates intracellular calcium levels
• Neurotransmitter release: Modulates vesicle release probability
• Dendritic spine morphology: Influences spine shape and density

Neuroprotection

GPR137 exhibits neuroprotective properties through multiple mechanisms[@liu2019]:

Disease Associations

Alzheimer's Disease

GPR137 is implicated in [Alzheimer's Disease](/diseases/alzheimers-disease) through several mechanisms[@chene2017]:

The receptor's modulation of autophagy is particularly relevant to AD pathogenesis, as impaired autophagy is a hallmark of the disease. GPR137's role in regulating autophagic flux could influence amyloid and tau clearance.

Parkinson's Disease

In [Parkinson's Disease](/diseases/parkinsons-disease)[@wang2018], GPR137 plays important roles:

Genetic variants in GPR137 may influence PD risk[@kim2020], suggesting the receptor could be a genetic modifier of disease susceptibility or progression.

Huntington Disease

Recent studies have identified roles for GPR137 in [Huntington Disease](/diseases/huntingtons)[@miller2024]:

Other Neurological Conditions

GPR137 has also been implicated in:

• Schizophrenia: Genetic association studies suggest possible links
• Bipolar disorder: Altered expression in limbic regions
• Major depression: Dysregulation in prefrontal cortex
• Epilepsy: May influence neuronal excitability

Therapeutic Implications

Drug Development

GPR137 represents a promising therapeutic target due to its[@brown2023]:

• Brain-specific expression profile
• Neuroprotective properties
• Modulation of autophagy pathways
• Accessibility to small molecule modulators

Agonist Development

Efforts to develop GPR137 agonists have focused on[@johnson2024]:

Agonist development is complicated by the receptor's orphan status, but recent progress in identifying potential endogenous ligands has accelerated drug discovery efforts.

Antagonist Applications

In some contexts, GPR137 antagonists may be beneficial[@brown2023]:

• Cancer therapy: Blocking GPR137 in certain tumors
• Inflammatory conditions: Modulating microglial activation

Biomarker Potential

GPR137 expression patterns may serve as diagnostic or prognostic biomarkers:

• Peripheral blood mononuclear cells: GPR137 expression as disease marker
• CSF analysis: Investigating CSF GPR137 levels
• Genetic variants: As risk modifiers for neurodegenerative disease

Research Methods

Genetic Approaches

• Genome-wide association studies (GWAS)
• Whole exome sequencing in neurodegenerative disease cohorts
• Linkage analysis in families
• CRISPR-Cas9 knockout studies

Molecular Biology Techniques

• RNA sequencing and qPCR
• Western blot and immunohistochemistry
• Co-immunoprecipitation for protein interactions
• Surface plasmon resonance for ligand binding

Functional Assays

• Calcium imaging
• Electrophysiology (patch clamp recordings)
• Autophagy flux assays
• Behavioral testing in animal models

Molecular Mechanisms

GPR137 and the Unfolded Protein Response

GPR137 has been implicated in modulating the unfolded protein response (UPR) in neurons[@lee2024]. The UPR is activated by endoplasmic reticulum stress, which is a common feature of neurodegenerative diseases.

Mechanisms:

• GPR137 activation reduces ER stress markers
• Modulates CHOP expression
• Influences caspase activation during ER stress

GPR137 in Mitochondrial Dynamics

Recent work has identified roles for GPR137 in mitochondrial function[@lee2024]:

Microglial GPR173 and Neuroinflammation

Microglial GPR137 expression is dynamically regulated[@garcia2024]:

• Inflammatory induction: LPS and IFN-γ increase GPR137 expression
• Anti-inflammatory effects: GPR137 activation reduces pro-inflammatory cytokines
• Phagocytosis modulation: Affects microglial phagocytic activity

Clinical and Translational Perspectives

Therapeutic Strategies

Several approaches for targeting GPR137 therapeutically are under investigation:

Agonist therapy: Small molecule agonists could:

• Enhance autophagy in neurodegenerative diseases
• Protect dopaminergic neurons in PD
• Improve synaptic function in AD

• GPR137 overexpression cassettes
• Modified GPR137 with enhanced signaling
• shRNA for knockdown when antagonists are needed

• Amyloid-targeting antibodies
• Tau-targeting therapies
• Alpha-synuclein clearance approaches

Biomarker Development

GPR137 has potential as a biomarker in several contexts:

• Diagnostic markers: Blood or CSF GPR137 levels
• Progression markers: Changes over disease course
• Treatment response: Pathway activation as pharmacodynamic marker

Key Research Questions

Unresolved Questions

Several key questions remain about GPR137 biology:

Emerging Research Directions

New areas of investigation include:

• Cryo-EM structural studies
• Development of biased agonists
• Clinical translation studies
• Single-cell resolution mapping

Key Publications

See Also

• [G Protein-Coupled Receptors](/entities/g-protein-coupled-receptors)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)
• [Huntington's Disease](/diseases/huntingtons)
• [SREB family signaling](/mechanisms/sreb-family-signaling)
• [Autophagy in neurodegeneration](/mechanisms/autophagy-neurodegeneration)
• [Neuroprotection pathways](/treatments/neuroprotection)

External Links

• [NCBI Gene: GPR137](https://www.ncbi.nlm.nih.gov/gene/26964)
• [UniProt: Q9NZU5](https://www.uniprot.org/uniprot/Q9NZU5)
• [Ensembl: ENSG00000141574](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000141574)
• [PubMed](https://pubmed.ncbi.nlm.nih.gov/?term=GPR137)