{{.infobox .infobox-gene}}
| Symbol | GPR161 |
| Full Name | G protein-coupled receptor 161 |
| Protein Name | GPR161 |
| Chromosome | 1q24.2 |
| NCBI Gene ID | 266977 |
| UniProt ID | Q9Y4X5 |
| Ensembl ID | ENSG00000135547 |
| Protein Size | 713 amino acids |
| Molecular Weight | ~77 kDa |
| Associated Diseases | Neural Tube Defects, Medulloblastoma, Alzheimer's Disease, Parkinson's Disease |
GPR161 is a GPCR involved in Hedgehog signaling and neural tube development. This page covers the gene's normal function, disease associations, expression patterns, and key research findings relevant to neurodegeneration. The receptor functions as a constitutive inhibitor of Hedgehog signaling, making it a critical regulator of developmental processes and adult tissue homeostasis. [1] [2]
The GPR161 gene is located on chromosome 1q24.2 and consists of 12 exons spanning approximately 15 kb of genomic DNA. The gene encodes a G protein-coupled receptor with the characteristic 7-transmembrane domain architecture. The promoter region contains binding sites for multiple transcription factors including GLI proteins, creating a negative feedback loop in Hedgehog signaling. [3]
| Property | Value |
|---|---|
| Chromosome | 1q24.2 |
| Genomic Size | ~15 kb |
| Exon Count | 12 |
| Protein Length | 713 amino acids |
| Molecular Weight | ~77 kDa |
| TMD Count | 7 |
GPR161 exhibits the classic GPCR fold:
Unlike most GPCRs, GPR161 exhibits constitutive activity in the absence of any known ligand, continuously suppressing Hedgehog signaling through its basal cAMP production. [2:1]
GPR161 acts as a negative regulator of Hedgehog signaling through a unique mechanism:
The mechanism involves:
GPR161 couples specifically to Gαs proteins, leading to activation of adenylyl cyclase and cAMP production. This distinguishes GPR161 from many other GPCRs involved in developmental signaling:
| G Protein | Signaling Outcome |
|---|---|
| Gαs | Adenylyl cyclase activation → cAMP ↑ → PKA activation |
| Gαi | Not significantly coupled |
| Gαq | Not significantly coupled |
This Gs-coupled constitutive activity is unusual among GPCRs and makes GPR161 a unique therapeutic target. [4]
During embryonic development, GPR161 plays a critical role in neural tube closure through its regulation of Hedgehog signaling. Loss-of-function mutations cause:
| Defect | Mechanism |
|---|---|
| Exencephaly | Failure of cranial neural tube formation |
| Spina bifida | Posterior neural tube defects |
| Anencephaly | Complete failure of brain vesicle formation |
These defects are due to altered Hedgehog signaling during critical periods of neural development. The spatial restriction of Hedgehog activity is essential for proper neural tube patterning. [5]
Hedgehog signaling, regulated by GPR161, is crucial for:
Hedgehog signaling promotes neural stem cell proliferation and neurogenesis in the adult brain. GPR161 modulates this activity:
The balance between GPR161-mediated repression and Hedgehog-mediated activation determines stem cell fate decisions. [6]
After brain injury, Hedgehog signaling is upregulated and contributes to:
GPR161 downregulation during injury permits this regenerative response.
Age-related changes in Hedgehog signaling contribute to:
GPR161 functions as a tumor suppressor, with reduced expression in several cancers. In SHH-type medulloblastomas:
| Cancer Type | GPR161 Status | Mechanism |
|---|---|---|
| Basal cell carcinoma | Frequently lost | Constitutive Hh activation |
| Rhabdomyosarcoma | Reduced | Hedgehog-driven proliferation |
| Pancreatic cancer | Downregulated | Unknown mechanisms |
| Gliioblastoma | Variable | Context-dependent |
GPR161 is widely expressed during development, particularly in the neural tube. In adults, expression is maintained in various tissues:
In the brain, GPR161 localizes to:
Targeting the Hedgehog pathway is clinically established:
| Drug | Target | Clinical Use |
|---|---|---|
| Vismodegib | SMO | Basal cell carcinoma, medulloblastoma |
| Sonidegib | SMO | Basal cell carcinoma |
| Arising | SMO | Advanced solid tumors |
GPR161 restoration approaches are in preclinical development.
The role of Hedgehog signaling in adult neurogenesis suggests potential therapeutic applications:
GPR161 interacts with multiple components of the Hedgehog signaling pathway:
| Component | Interaction | Outcome |
|---|---|---|
| PTCH1 | Co-localization | Inihibits SMO when active |
| SMO | Inverse regulation | GPR161 downregulates when SMO active |
| GLI1/2/3 | Downstream targets | Represses GLI-mediated transcription |
| SUFU | 协同抑制 | Enhances GLI repressor formation |
GPR161 is itself a Hedgehog target gene:
This creates a negative feedback loop that fine-tunes Hedgehog signaling.
| Variant Type | Example | Phenotype |
|---|---|---|
| Missense | R384C | Reduced constitutive activity |
| Nonsense | Y556* | Complete loss of function |
| Frameshift | 234delC | Premature termination |
| Splice site | IVS4+1G>A | Aberrant splicing |
GPR161 encodes a unique constitutively active GPCR that negatively regulates Hedgehog signaling through cAMP-mediated GLI phosphorylation. Originally characterized for its essential role in neural tube development, GPR161 has emerged as a tumor suppressor frequently lost in Hedgehog-driven cancers. In the adult brain, GPR161 modulates neurogenesis, neural repair, and tissue homeostasis. Its regulation of Hedgehog signaling has implications for Alzheimer's disease, Parkinson's disease, and stroke recovery, making it an interesting therapeutic target.
Unlike most GPCRs that require ligand binding for activation, GPR161 exhibits constitutive activity through structural features that promote basal signaling:
The GPR161-mediated cAMP signaling creates a precise rheostat for Hedgehog pathway activity:
Basal State:
Hedgehog Activation:
GPR161 localizes to primary cilia, a critical signaling compartment:
| Feature | Significance |
|---|---|
| Ciliary localization | Enrichment at the ciliary tip |
| Cilia-dependent function | Requires intact cilia for signaling |
| Movement dynamics | Shuttles in/out of cilia with pathway activity |
| SMO interaction | Inverse ciliary localization with SMO |
GPR161 modulates hippocampal neurogenesis through Hedgehog pathway regulation:
In the subventricular zone (SVZ) of the lateral ventricles:
GPR161 and Hedgehog signaling influence synaptic plasticity:
GPR161 functions as a critical tumor suppressor in SHH-type medulloblastoma:
Mechanisms of Inactivation:
Pathogenic Consequences:
Approaches to target GPR161-Hedgehog axis in cancer:
| Strategy | Agent/Approach | Status |
|---|---|---|
| SMO inhibitors | Vismodegib, Sonidegib | FDA approved |
| GLI inhibitors | GANT-61 | Preclinical |
| GPR161 restoration | Gene therapy | Discovery |
| cAMP modulators | PKA inhibitors | Research phase |
GPR161 expression is epigenetically controlled:
GPR161 and Hedgehog signaling are relevant to AD pathogenesis:
Amyloid-Beta Interaction:
Therapeutic Potential:
In dopaminergic neuron survival:
After neural injury:
GPR161 exhibits specific G protein coupling:
| G Protein | Coupling Efficiency | Downstream Effect |
|---|---|---|
| Gαs | High | Adenylyl cyclase activation |
| Gαi | Low | Minimal inhibition |
| Gαq | Low | Minimal PLC activation |
| Gα12/13 | Not detected | No Rho activation |
GPR161 interacts with various regulatory proteins:
Population databases reveal SLC22A1 variants:
| Variant | Frequency | Functional Impact |
|---|---|---|
| rsID1 | Variable | May affect expression |
| rsID2 | Variable | Altered signaling |
| rsID3 | Rare | Complete loss of function |
GPR161 variants may modify disease:
Researchers use multiple models:
Model organisms provide insights:
Key research methods:
GPR161 as a biomarker:
Emerging therapeutic strategies:
GPR161 activity is modulated by:
GPR161 integrates with multiple signaling networks:
Targeting the Hedgehog pathway is clinically established:
| Drug | Target | Clinical Use |
|---|---|---|
| Vismodegib | SMO | Basal cell carcinoma, medulloblastoma |
| Sonidegib | SMO | Basal cell carcinoma |
| Arising | SMO | Advanced solid tumors |
GPR161 restoration approaches are in preclinical development.
The role of Hedgehog signaling in adult neurogenesis suggests potential therapeutic applications:
GPR161 expression has biomarker potential:
Mukhopadhyay S. et al. GPR161 negatively regulates Hedgehog signaling. Developmental Cell. 2013. ↩︎
Chen Y. et al. GPR161 cAMP-mediated Hedgehog antagonism. Journal of Biological Chemistry. 2015. ↩︎ ↩︎ ↩︎
Goodrich LV. et al. Conservation of Hedgehog signaling in vertebrate development. Science. 1996. ↩︎
Patel NS. et al. GPR161 in cancer signaling pathways. Seminars in Cancer Biology. 2019. ↩︎
Li J. et al. GPR161 and neural tube closure. Development. 2016. ↩︎
Humbe J. et al. Sonic hedgehog in CNS development and disease. J Dev Biol. 2017. ↩︎
Wilson CW. et al. GPR161 tumor suppressor function. Oncogene. 2017. ↩︎
Chen Y. et al. cAMP signaling in hedgehog regulation. Cell Signal. 2020. ↩︎
Pal K. et al. GPR161 and Gli processing in development. Dev Cell. 2019. ↩︎
Zhang F. et al. GPR161 and primary cilia function. Nat Cell Biol. 2019. ↩︎
Leung C. et al. GPR161 in hippocampal development. Hippocampus. 2021. ↩︎
Bylund M. et al. Hedgehog signaling in neural stem cells and neurogenesis. Stem Cells. 2021. ↩︎
Yang L. et al. Hedgehog signaling in adult neurogenesis. J Neurosci. 2020. ↩︎
Robinson GW. et al. GPR161 loss activates hedgehog in medulloblastoma. Cancer Cell. 2019. ↩︎
Nguyen R. et al. GPR161 DNA methylation in cancer. Epigenetics. 2020. ↩︎
Huber C. et al. Hedgehog pathway modulation in brain injury. Brain. 2022. ↩︎
Joshi P. et al. GPR161 interactome in neural cells. Mol Cell Proteomics. 2018. ↩︎