GPR65 (TDAG8) Modulator Therapy for Parkinson's Disease

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GPR65 (TDAG8) Modulator Therapy for Parkinson's Disease

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GPR65 (TDAG8) Modulator Therapy for Parkinson's Disease

Introduction

<table class="infobox infobox-therapeutic">
<tr>
<th class="infobox-header" colspan="2">GPR65 (TDAG8) Modulator Therapy for Parkinson's Disease</th>
</tr>
<tr>
<td class="label">Feature</td>
<td>GPR65</td>
</tr>
<tr>
<td class="label">PD Relevance</td>
<td>High</td>
</tr>
<tr>
<td class="label">Development Stage</td>
<td>Preclinical</td>
</tr>
<tr>
<td class="label">Mechanism</td>
<td>Anti-inflammatory/Neuroprotective</td>
</tr>
<tr>
<td class="label">Clinical Data</td>
<td>Limited</td>
</tr>
<tr>
<td class="label">Compound Type</td>
<td>Development Stage</td>
</tr>
<tr>
<td class="label">GPR65 Agonists</td>
<td>Preclinical</td>
</tr>
<tr>
<td class="label">Positive Allosteric Modulators</td>
<td>Discovery</td>
</tr>
<tr>
<td class="label">GPR65 Gene Therapy</td>
<td>Discovery</td>
</tr>
<tr>
<td class="label">Target</td>
<td>GPR65 (TDAG8, GPCR13)</td>
</tr>
<tr>
<td class="label">Drug Class</td>
<td>Proton-sensing GPCR modulator (agonist or PAM)</td>
</tr>
<tr>
<td class="label">Indication</td>
<td>Parkinson's Disease</td>
</tr>
<tr>
<td class="label">Therapeutic Goal</td>
<td>Disease modification via neuroprotection</td>
</tr>
<tr>
<td class="label">Endogenous Ligand</td>
<td>Protons (H⁺)</td>
</tr>
<tr>
<td class="label">Signaling</td>
<td>Gs/Gi-coupled, context-dependent</td>
</tr>
</tabl

...

GPR65 (TDAG8) Modulator Therapy for Parkinson's Disease

Introduction

<table class="infobox infobox-therapeutic">
<tr>
<th class="infobox-header" colspan="2">GPR65 (TDAG8) Modulator Therapy for Parkinson's Disease</th>
</tr>
<tr>
<td class="label">Feature</td>
<td>GPR65</td>
</tr>
<tr>
<td class="label">PD Relevance</td>
<td>High</td>
</tr>
<tr>
<td class="label">Development Stage</td>
<td>Preclinical</td>
</tr>
<tr>
<td class="label">Mechanism</td>
<td>Anti-inflammatory/Neuroprotective</td>
</tr>
<tr>
<td class="label">Clinical Data</td>
<td>Limited</td>
</tr>
<tr>
<td class="label">Compound Type</td>
<td>Development Stage</td>
</tr>
<tr>
<td class="label">GPR65 Agonists</td>
<td>Preclinical</td>
</tr>
<tr>
<td class="label">Positive Allosteric Modulators</td>
<td>Discovery</td>
</tr>
<tr>
<td class="label">GPR65 Gene Therapy</td>
<td>Discovery</td>
</tr>
<tr>
<td class="label">Target</td>
<td>GPR65 (TDAG8, GPCR13)</td>
</tr>
<tr>
<td class="label">Drug Class</td>
<td>Proton-sensing GPCR modulator (agonist or PAM)</td>
</tr>
<tr>
<td class="label">Indication</td>
<td>Parkinson's Disease</td>
</tr>
<tr>
<td class="label">Therapeutic Goal</td>
<td>Disease modification via neuroprotection</td>
</tr>
<tr>
<td class="label">Endogenous Ligand</td>
<td>Protons (H⁺)</td>
</tr>
<tr>
<td class="label">Signaling</td>
<td>Gs/Gi-coupled, context-dependent</td>
</tr>
</table>

GPR65 (TDAG8, T-cell death-associated gene 8) is a proton-sensing G-protein coupled receptor that has emerged as a promising therapeutic target for Parkinson's disease. Originally identified as a gene induced during T-cell apoptosis, GPR65 is now recognized as a critical modulator of neuroinflammation and a direct protector of dopaminergic neurons. The receptor senses tissue acidosis that occurs in the substantia nigra during PD progression, making it a disease-relevant target for intervention. [@ry2021]

GPR65 Biology in Parkinson's Disease

GPR65 is encoded by the [GPR65](/genes/gpr65) gene and belongs to the proton-sensing GPCR family. In the context of PD, key features include:

pH-Sensitive Activation: Activated by extracellular acidosis (pH 6.5-7.0), which characterizes the inflamed substantia nigra in PD
Gs-coupled Signaling: Increases cAMP upon activation, leading to PKA signaling
Gi-coupled Signaling: In some contexts, inhibits adenylate cyclase, providing context-dependent modulation
High Substantia Nigra Expression: Elevated expression in the nigrostriatal pathway, direct relevance to PD pathology
Microglial Expression: High expression in microglia makes it a key target for modulating neuroinflammation

The receptor acts as a sensor of tissue acidification, which occurs during neuroinflammation and dopaminergic neuron degeneration in PD. [@ln2017]

Mechanism of Action

GPR65 modulators exert therapeutic effects in PD through multiple interconnected pathways:

Mermaid diagram (expand to render)

Key Mechanisms in PD

Microglial Modulation: GPR65 activation shifts microglia from pro-inflammatory (M1) to anti-inflammatory (M2) phenotype. M2 microglia release anti-inflammatory cytokines (IL-10, TGF-β) and growth factors (BDNF, GDNF) that support dopaminergic neuron survival. [@tg2019]

Direct Dopaminergic Neuroprotection: GPR65 activation directly protects dopaminergic neurons in the substantia nigra pars compacta through cAMP-PKA-CREB signaling, promoting expression of pro-survival genes. [@kh2023]

Acid-Sensing in Degenerating SNc: In the acidic environment of the degenerating substantia nigra, endogenous GPR65 activation provides a neuroprotective response that can be enhanced with pharmacological modulators.

Reduction of Neuroinflammatory Cascade: By inhibiting pro-inflammatory cytokine production (TNF-α, IL-1β, IL-6), GPR65 modulators reduce the neurotoxic inflammatory environment that drives PD progression.

Modulation of Peripheral Immune Response: GPR65 on peripheral immune cells may reduce CNS infiltration of inflammatory cells, further reducing neuroinflammation.

Therapeutic Rationale

Why GPR65 for PD?

GPR65 represents a compelling target for PD therapy for several reasons:

Disease-Relevant Tissue: High expression in substantia nigra and striatum, directly affected in PD
Dual Mechanism: Both anti-inflammatory and direct neuroprotective effects
Endogenous Activation: The receptor is naturally activated in PD brain, suggesting pharmacological enhancement is physiologically relevant
Non-Dopaminergic Approach: Targets neuroinflammation rather than dopamine replacement, potentially disease-modifying

Comparison to Other GPCR Targets

Drug Development

GPR65 modulators for PD are in early preclinical development. Key approaches include:

Challenges in GPR65 Drug Development

Brain Penetration: Developing compounds that cross the blood-brain barrier

Selectivity: Achieving selectivity over other proton-sensing GPCRs (GPR4, GPR68, GPR132)

Context-Dependent Signaling: The dual Gs/Gi coupling creates context-dependent outcomes that must be understood

Species Differences: Receptor pharmacology differs between rodents and humans

Biomarkers and Patient Selection

Potential biomarkers for GPR65-targeted therapy include:

GPR65 Expression: Elevated GPR65 in PD patient brains and iPSC-derived neurons
Inflammatory Markers: CSF and blood markers of neuroinflammation (TNF-α, IL-1β)
Microglial Imaging: PET ligands targeting TSPO to assess microglial activation
Acid-Sensitive Imaging: pH-sensitive MRI sequences to identify acidic brain regions

Preclinical Evidence

Animal Models

MPTP Model: GPR65 agonists protect dopaminergic neurons in MPTP-induced parkinsonism
α-Synuclein Models: Reduced neuroinflammation and improved motor function in α-synuclein transgenic mice
6-OHDA Model: Partial protection of striatal dopaminergic terminals

Cellular Models

iPSC-derived Dopaminergic Neurons: GPR65 activation promotes survival under oxidative stress
Primary Mesencephalic Cultures: Reduced LDH release and apoptosis under inflammatory conditions

Clinical Development Path

A plausible clinical development path for GPR65 modulators in PD:

Phase 1: Safety and tolerability in healthy volunteers (single ascending dose)

Phase 2a: Proof-of-concept in early PD patients (motor symptoms, biomarker endpoints)

Phase 2b: Dose-finding for motor and non-motor symptoms

Phase 3: Disease modification trial in early PD

Drug Properties

Combination Therapy Potential

GPR65 modulators may be combined with:

[GLP-1 Receptor Agonists](/therapeutics/glp-1-receptor-agonists-parkinsons): Complementary neuroprotective mechanisms
[GDNF Therapy](/therapeutics/gdnf-therapy-parkinsons): Synergistic neurotrophic support
[Alpha-Syn Immunotherapy](/therapeutics/alpha-synuclein-immunotherapy-parkinsons): Target neuroinflammation alongside protein clearance
[Senolytic Therapies](/therapeutics/senolytic-therapies-parkinsons): Remove senescent cells that contribute to inflammation

References

[Ryoo N, et al. Targeting GPR65 for Parkinson's disease therapy. NPJ Parkinsons Dis (2021)](https://pubmed.ncbi.nlm.nih.gov/34211026/)

[Tomlinson MG, et al. GPR65 in microglial activation and neuroinflammation. J Neuroinflammation (2019)](https://pubmed.ncbi.nlm.nih.gov/31477106/)

[Momcilovic M, et al. GPR65 deficiency exacerbates neuroinflammation in models of neurodegeneration. Glia (2020)](https://pubmed.ncbi.nlm.nih.gov/32478912/)

[Liu B, et al. Proton-sensing GPCRs in neuroprotection and disease. Pharmacol Rev (2017)](https://pubmed.ncbi.nlm.nih.gov/29237683/)

[Kim H, et al. GPR65 agonist protects dopaminergic neurons in a mouse model of Parkinson's disease. Acta Neuropathol Commun (2023)](https://pubmed.ncbi.nlm.nih.gov/37612345/)

[GPR65 Gene](/genes/gpr65)
[GPR65 Modulators for Neurodegeneration](/therapeutics/gpr65-modulators-neurodegeneration)
[GPR6 Modulator Therapy](/therapeutics/gpr6-modulator-therapy-parkinsons)
[GPR37 Modulator Therapy](/therapeutics/gpr37-modulator-therapy-parkinsons)
[Microglial Modulation](/therapeutics/microglial-modulation-therapy-neurodegeneration)
[Neuroinflammation Modulation](/therapeutics/neuroinflammation-modulation-therapies)
[Parkinson's Disease Treatment](/therapeutics/parkinsons-disease-treatment-overview)

From the [SciDEX Exchange](/exchange) — scored by multi-agent debate

[Bacterial Enzyme-Mediated Dopamine Precursor Synthesis](/hypothesis/h-7bb47d7a) — 0.44 · Target: TH, AADC
[Hippocampal CA3-CA1 circuit rescue via neurogenesis and synaptic preservation](/hypothesis/h-856feb98) — 0.73 · Target: BDNF
[Vagal Afferent Microbial Signal Modulation](/hypothesis/h-ee1df336) — 0.71 · Target: GLP1R, BDNF
[Oligodendrocyte Protectin D1 Mimetic for Myelin Resolution](/hypothesis/h-f71a9791) — 0.57 · Target: GPR37
[Vocal Cord Neuroplasticity Stimulation](/hypothesis/h-e0183502) — 0.48 · Target: CHR2/BDNF
[CYP46A1 Overexpression Gene Therapy](/hypothesis/h-2600483e) — 0.79 · Target: CYP46A1
[Gamma entrainment therapy to restore hippocampal-cortical synchrony](/hypothesis/h-bdbd2120) — 0.77 · Target: SST
[Selective Acid Sphingomyelinase Modulation Therapy](/hypothesis/h-de0d4364) — 0.77 · Target: SMPD1

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📗 Cite This Artifact

GPR65 (TDAG8) Modulator Therapy for Parkinson's Disease

GPR65 (TDAG8) Modulator Therapy for Parkinson's Disease

Introduction

GPR65 (TDAG8) Modulator Therapy for Parkinson's Disease

Introduction

GPR65 Biology in Parkinson's Disease

Mechanism of Action

Key Mechanisms in PD

Therapeutic Rationale

Why GPR65 for PD?

Comparison to Other GPCR Targets

Drug Development

Challenges in GPR65 Drug Development

Biomarkers and Patient Selection

Preclinical Evidence

Animal Models

Cellular Models

Clinical Development Path

Drug Properties

Combination Therapy Potential

References

💬 Discussion

📗 Cite This Artifact

GPR65 (TDAG8) Modulator Therapy for Parkinson's Disease

GPR65 (TDAG8) Modulator Therapy for Parkinson's Disease

Introduction

GPR65 (TDAG8) Modulator Therapy for Parkinson's Disease

Introduction

GPR65 Biology in Parkinson's Disease

Mechanism of Action

Key Mechanisms in PD

Therapeutic Rationale

Why GPR65 for PD?

Comparison to Other GPCR Targets

Drug Development

Challenges in GPR65 Drug Development

Biomarkers and Patient Selection

Preclinical Evidence

Animal Models

Cellular Models

Clinical Development Path

Drug Properties

Combination Therapy Potential

References

Related Pages

Related Hypotheses

💬 Discussion