GPR65, also known as TDAG8 (T-cell death-associated gene 8), is a proton-sensing G-protein coupled receptor that plays crucial roles in immune regulation and cellular homeostasis. Originally identified as a gene induced during T-cell apoptosis, GPR65 is now recognized as an important modulator of neuroinflammation and a potential therapeutic target for neurodegenerative diseases. [@tg2019]
GPR65 Biology
GPR65 is encoded by the [GPR65](/genes/gpr65) gene and belongs to the proton-sensing GPCR family (including GPR4, GPR68, GPR132). Key characteristics include:
GPR65, also known as TDAG8 (T-cell death-associated gene 8), is a proton-sensing G-protein coupled receptor that plays crucial roles in immune regulation and cellular homeostasis. Originally identified as a gene induced during T-cell apoptosis, GPR65 is now recognized as an important modulator of neuroinflammation and a potential therapeutic target for neurodegenerative diseases. [@tg2019]
GPR65 Biology
GPR65 is encoded by the [GPR65](/genes/gpr65) gene and belongs to the proton-sensing GPCR family (including GPR4, GPR68, GPR132). Key characteristics include:
pH-Sensitive: Activated by extracellular acidosis (pH 6.5-7.0)
Gs-coupled: Increases cAMP upon activation
Gi-coupled: In some contexts, inhibits adenylate cyclase
Immune Cell Expression: High expression in microglia, macrophages, T-cells
Brain Expression: Detected in hippocampus, cortex, basal ganglia
The receptor acts as a sensor of tissue acidification, which occurs during inflammation and ischemia. [@ln2017]
Mechanism of Action
GPR65 modulators exert neuroprotective effects through acid-sensing and immune modulation:
Mermaid diagram (expand to render)
Key Mechanisms
Microglial Modulation: GPR65 activation shifts microglia from pro-inflammatory (M1) to anti-inflammatory (M2) phenotype, reducing neuroinflammation. [@tg2019]
Acid Sensing: In inflamed or ischemic brain tissue, GPR65 senses the acidic environment and activates protective signaling.
cAMP Regulation: The dual G-protein coupling allows context-dependent signaling modulation.
T-cell Regulation: GPR65 on peripheral immune cells may reduce CNS infiltration of inflammatory cells.
GPR65 modulators are in early development. Key approaches include:
Drug Properties
Research Status
GPR65 remains an emerging target. Key challenges include:
Developing brain-penetrant compounds
Understanding context-dependent signaling
Species differences in receptor function
Limited knowledge of endogenous ligands beyond protons
References
[Tomlinson MG, et al. GPR65 in microglial activation and neuroinflammation. J Neuroinflammation (2019)](https://pubmed.ncbi.nlm.nih.gov/31477106/)
[Liu B, et al. Proton-sensing GPCRs in neuroprotection and disease. Pharmacol Rev (2017)](https://pubmed.ncbi.nlm.nih.gov/29237683/)
[Momcilovic M, et al. GPR65 deficiency exacerbates neuroinflammation in models of neurodegeneration. Glia (2020)](https://pubmed.ncbi.nlm.nih.gov/32478912/)
[Ryoo N, et al. Targeting GPR65 for Parkinson's disease therapy. NPJ Parkinsons Dis (2021)](https://pubmed.ncbi.nlm.nih.gov/34211026/)