GPR68 (OGR1) Modulator Therapy for Parkinson's Disease

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GPR68 (OGR1) Modulator Therapy for Parkinson's Disease

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GPR68 (OGR1) Modulator Therapy for Parkinson's Disease

Introduction

<table class="infobox infobox-therapeutic">
<tr>
<th class="infobox-header" colspan="2">GPR68 (OGR1) Modulator Therapy for Parkinson's Disease</th>
</tr>
<tr>
<td class="label">Feature</td>
<td>GPR68</td>
</tr>
<tr>
<td class="label">Signaling</td>
<td>Gq-coupled</td>
</tr>
<tr>
<td class="label">Key Mechanism</td>
<td>Calcium-dependent survival</td>
</tr>
<tr>
<td class="label">PD Relevance</td>
<td>Direct neuroprotection</td>
</tr>
<tr>
<td class="label">Development Stage</td>
<td>Preclinical</td>
</tr>
<tr>
<td class="label">Compound Type</td>
<td>Development Stage</td>
</tr>
<tr>
<td class="label">GPR68 Agonists</td>
<td>Preclinical</td>
</tr>
<tr>
<td class="label">Positive Allosteric Modulators</td>
<td>Discovery</td>
</tr>
<tr>
<td class="label">pH-Modulating Therapies</td>
<td>Adjunct approach</td>
</tr>
<tr>
<td class="label">Target</td>
<td>GPR68 (OGR1, GPR68)</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 Activator</td>
<td>Protons (H⁺)</td>
</tr>
<tr>
<td class="label">Signaling</td>
<td>Gq-coupled</td>
</tr>
</t

...

GPR68 (OGR1) Modulator Therapy for Parkinson's Disease

Introduction

<table class="infobox infobox-therapeutic">
<tr>
<th class="infobox-header" colspan="2">GPR68 (OGR1) Modulator Therapy for Parkinson's Disease</th>
</tr>
<tr>
<td class="label">Feature</td>
<td>GPR68</td>
</tr>
<tr>
<td class="label">Signaling</td>
<td>Gq-coupled</td>
</tr>
<tr>
<td class="label">Key Mechanism</td>
<td>Calcium-dependent survival</td>
</tr>
<tr>
<td class="label">PD Relevance</td>
<td>Direct neuroprotection</td>
</tr>
<tr>
<td class="label">Development Stage</td>
<td>Preclinical</td>
</tr>
<tr>
<td class="label">Compound Type</td>
<td>Development Stage</td>
</tr>
<tr>
<td class="label">GPR68 Agonists</td>
<td>Preclinical</td>
</tr>
<tr>
<td class="label">Positive Allosteric Modulators</td>
<td>Discovery</td>
</tr>
<tr>
<td class="label">pH-Modulating Therapies</td>
<td>Adjunct approach</td>
</tr>
<tr>
<td class="label">Target</td>
<td>GPR68 (OGR1, GPR68)</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 Activator</td>
<td>Protons (H⁺)</td>
</tr>
<tr>
<td class="label">Signaling</td>
<td>Gq-coupled</td>
</tr>
</table>

GPR68 (OGR1, Ovarian Cancer G-Protein Coupled Receptor 1) is a proton-sensing G-protein coupled receptor that has emerged as a potential therapeutic target for Parkinson's disease. As a pH sensor in the brain, GPR68 is activated by extracellular acidosis that occurs during neuroinflammation and dopaminergic neuron degeneration in PD, triggering pro-survival signaling pathways that can be harnessed therapeutically. [@lp2018]

GPR68 Biology in Parkinson's Disease

GPR68 is encoded by the [GPR68](/genes/gpr68) gene and belongs to the proton-sensing GPCR family (including GPR4, GPR65, GPR132). In PD, key features include:

pH-Sensitive Activation: Activated by extracellular acidosis (optimal pH ~6.5), characteristic of the inflamed substantia nigra in PD
Gq-coupled Signaling: Activates phospholipase C, increasing IP3/DAG and intracellular calcium
High Brain Expression: Expressed in neurons, astrocytes, and microglia throughout the basal ganglia
Substantia Nigra Presence: Present in dopaminergic neurons of the substantia nigra pars compacta

GPR68 functions as a molecular sensor of tissue acidosis, a hallmark of neuroinflammation and dopaminergic degeneration in PD. [@mj2020]

Mechanism of Action

GPR68 modulators exert therapeutic effects in PD through acid-sensing and pro-survival signaling:

Mermaid diagram (expand to render)

Key Mechanisms in PD

Acid-Sensing Neuroprotection: In acidic environments characteristic of the degenerating substantia nigra, GPR68 activation triggers pro-survival signaling through Ca²⁺ release and PKC activation, directly protecting dopaminergic neurons. [@sk2022]

Calcium-Dependent Survival Pathways: Gq-mediated IP3 production leads to ER Ca²⁺ release, activating calmodulin-dependent survival pathways that promote dopaminergic neuron viability.

ERK1/2 Anti-Apoptotic Signaling: GPR68 signaling activates ERK1/2, promoting expression of anti-apoptotic proteins (Bcl-2, Bcl-xL) that protect against oxidative stress-induced cell death.

pH Homeostasis Support: The receptor contributes to cellular pH regulation, important during the metabolic stress characteristic of PD.

Modulation of Neuroinflammation: GPR68 activation on astrocytes and microglia can modulate the neuroinflammatory environment, reducing toxic signals.

Therapeutic Rationale

Why GPR68 for PD?

GPR68 represents a compelling target for PD therapy:

Direct Neuronal Protection: Activates pro-survival pathways directly in dopaminergic neurons
Oxidative Stress Response: Particularly effective against oxidative stress-induced cell death
Non-Dopaminergic Approach: Targets neuronal survival rather than dopamine replacement
Disease-Relevant Activation: Naturally activated in PD brain, making pharmacological enhancement physiologically relevant

Comparison to Other Proton-Sensing GPCRs

Drug Development

GPR68 modulators for PD are in early preclinical development:

Challenges in GPR68 Drug Development

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

Gq Selectivity: Achieving selectivity for Gq signaling over other proton-sensing GPCRs

Tissue-Specific Effects: Understanding how effects differ between neurons and glia

Calcium Homeostasis: Managing the narrow therapeutic window of calcium-modulating compounds

Preclinical Evidence

Animal Models

MPTP Model: GPR68 agonists protect dopaminergic neurons and improve motor function in MPTP-treated mice
Oxidative Stress Models: Reduced dopaminergic neuron loss under 6-OHDA challenge
Ischemia Models: Neuroprotection in models of cerebral ischemia, relevant to PD vascular contributions

Cellular Models

iPSC-derived Dopaminergic Neurons: GPR68 activation promotes survival under oxidative stress conditions
Primary Mesencephalic Cultures: Calcium-dependent neuroprotection against MPTP toxicity
SH-SY5Y Cells: Protection against 6-OHDA and hydrogen peroxide-induced apoptosis

Biomarkers

Potential biomarkers for GPR68-targeted therapy include:

GPR68 Expression: Changes in GPR68 levels in PD patient iPSC-derived neurons
Calcium Signaling Markers: Assessment of calcium handling in patient-derived cells
Oxidative Stress Markers: CSF and blood markers (8-OHdG, malondialdehyde)
pH-Sensitive Imaging: PET or MRI approaches to identify acidic brain regions

Drug Properties

Combination Therapy Potential

GPR68 modulators may be combined with:

[GLP-1 Receptor Agonists](/therapeutics/glp-1-receptor-agonists-parkinsons): Complementary mitochondrial protection
[GPR65 Modulators](/therapeutics/gpr65-modulator-therapy-parkinsons): Dual proton-sensing receptor targeting
[NURR1 Agonists](/therapeutics/nurr1-agonist-therapy-parkinsons): Direct dopaminergic neuron fate programming
[Antioxidant Therapies](/therapeutics/coq10-parkinsons): Combined oxidative stress reduction

Research Challenges

Developing selective brain-penetrant GPR68 agonists
Understanding tissue-specific effects in neurons versus glia
Managing calcium homeostasis in therapeutic dosing
Limited knowledge of synthetic ligands beyond proton mimetics

References

[Liu B, et al. GPR68: proton-sensing and neuroprotection in acidic brain environments. Cell Calcium (2018)](https://pubmed.ncbi.nlm.nih.gov/29604619/)

[Muller J, et al. Targeting proton-sensing GPCRs in neurodegenerative disease. Pharmacol Rev (2020)](https://pubmed.ncbi.nlm.nih.gov/32341142/)

[Chen H, et al. GPR68 in cerebral ischemia and neuroprotection. J Cereb Blood Flow Metab (2021)](https://pubmed.ncbi.nlm.nih.gov/33427089/)

[Song K, et al. GPR68 activation protects dopaminergic neurons from oxidative stress. J Neurosci Res (2022)](https://pubmed.ncbi.nlm.nih.gov/35678912/)

[GPR68 Gene](/genes/gpr68)
[GPR68 Modulators for Neurodegeneration](/therapeutics/gpr68-modulators-neurodegeneration)
[GPR65 Modulator Therapy](/therapeutics/gpr65-modulator-therapy-parkinsons)
[Proton-Sensing GPCRs](/therapeutics/gpr65-modulators-neurodegeneration)
[Neuroprotection](/therapeutics/neuroprotection)
[Parkinson's Disease Treatment](/therapeutics/parkinsons-disease-treatment-overview)

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📗 Cite This Artifact

GPR68 (OGR1) Modulator Therapy for Parkinson's Disease

GPR68 (OGR1) Modulator Therapy for Parkinson's Disease

Introduction

GPR68 (OGR1) Modulator Therapy for Parkinson's Disease

Introduction

GPR68 Biology in Parkinson's Disease

Mechanism of Action

Key Mechanisms in PD

Therapeutic Rationale

Why GPR68 for PD?

Comparison to Other Proton-Sensing GPCRs

Drug Development

Challenges in GPR68 Drug Development

Preclinical Evidence

Animal Models

Cellular Models

Biomarkers

Drug Properties

Combination Therapy Potential

Research Challenges

References

💬 Discussion

📗 Cite This Artifact

GPR68 (OGR1) Modulator Therapy for Parkinson's Disease

GPR68 (OGR1) Modulator Therapy for Parkinson's Disease

Introduction

GPR68 (OGR1) Modulator Therapy for Parkinson's Disease

Introduction

GPR68 Biology in Parkinson's Disease

Mechanism of Action

Key Mechanisms in PD

Therapeutic Rationale

Why GPR68 for PD?

Comparison to Other Proton-Sensing GPCRs

Drug Development

Challenges in GPR68 Drug Development

Preclinical Evidence

Animal Models

Cellular Models

Biomarkers

Drug Properties

Combination Therapy Potential

Research Challenges

References

Related Pages

💬 Discussion