MGEA5 — O-GlcNAcase (OGA)

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MGEA5 — O-GlcNAcase (OGA)

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MGEA5 — O-GlcNAcase (OGA)

Gene Overview

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">MGEA5 — O-GlcNAcase (OGA)</th>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>MGEA5</td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>Meningioma Expressed Antigen 5 (N-acetylneuraminidase)</td>
</tr>
<tr>
<td class="label">Chromosomal Location</td>
<td>10q24.32</td>
</tr>
<tr>
<td class="label">Protein Product</td>
<td>O-GlcNAcase (OGA)</td>
</tr>
<tr>
<td class="label">EC Number</td>
<td>3.2.1.96</td>
</tr>
<tr>
<td class="label">Alternative Names</td>
<td>OGA, MGEA5, NCOAT (Nuclear Cytoplasmic O-GlcNAcase and Transcriptional coactivator)</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>Q9H3K2</td>
</tr>
<tr>
<td class="label">Protein Length</td>
<td>917 amino acids</td>
</tr>
<tr>
<td class="label">Molecular Weight</td>
<td>~103 kDa</td>
</tr>
<tr>
<td class="label">Compound</td>
<td>Company</td>
</tr>
<tr>
<td class="label">FNP-223 (Etiglutide)</td>
<td>Ferrer</td>
</tr>
<tr>
<td class="label">LY-3372689 (Zaniglusab)</td>
<td>Eli Lilly</td>
</tr>
<tr>
<td class="label">MK-8719</td>
<td>Merck</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>

Biological Function

...

MGEA5 — O-GlcNAcase (OGA)

Gene Overview

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">MGEA5 — O-GlcNAcase (OGA)</th>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>MGEA5</td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>Meningioma Expressed Antigen 5 (N-acetylneuraminidase)</td>
</tr>
<tr>
<td class="label">Chromosomal Location</td>
<td>10q24.32</td>
</tr>
<tr>
<td class="label">Protein Product</td>
<td>O-GlcNAcase (OGA)</td>
</tr>
<tr>
<td class="label">EC Number</td>
<td>3.2.1.96</td>
</tr>
<tr>
<td class="label">Alternative Names</td>
<td>OGA, MGEA5, NCOAT (Nuclear Cytoplasmic O-GlcNAcase and Transcriptional coactivator)</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>Q9H3K2</td>
</tr>
<tr>
<td class="label">Protein Length</td>
<td>917 amino acids</td>
</tr>
<tr>
<td class="label">Molecular Weight</td>
<td>~103 kDa</td>
</tr>
<tr>
<td class="label">Compound</td>
<td>Company</td>
</tr>
<tr>
<td class="label">FNP-223 (Etiglutide)</td>
<td>Ferrer</td>
</tr>
<tr>
<td class="label">LY-3372689 (Zaniglusab)</td>
<td>Eli Lilly</td>
</tr>
<tr>
<td class="label">MK-8719</td>
<td>Merck</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>

Biological Function

MGEA5 encodes O-GlcNAcase (OGA), a glycoside hydrolase that catalyzes the removal of O-linked β-N-acetylglucosamine (O-GlcNAc) from serine and threonine residues on target proteins. This enzyme is a key component of the O-GlcNAcylation cycle, a dynamic post-translational modification (PTM) that regulates numerous cellular processes:

Mermaid diagram (expand to render)

Enzymatic Mechanism

OGA employs a substrate-assisted retention mechanism distinct from classical hydrolytic enzymes:

Substrate Binding: The enzyme recognizes the O-GlcNAcylated substrate through interactions with the sugar ring and aglycone moiety.

Catalytic Nucleophile Attack: The catalytic aspartate performs nucleophilic attack on the anomeric carbon, forming a covalent enzyme-intermediate complex.

Glycosyl Flip: The covalent intermediate undergoes a conformational change that facilitates the flip of the sugar.

Hydrolysis: Water attacks the intermediate, releasing free GlcNAc and regenerating the enzyme.

The catalytic center contains two essential aspartate residues (Asp174 and Asp175) that coordinate the substrate and facilitate catalysis[@ogacrystalstructure].

Domain Structure

MGEA5/OGA contains two functional domains:

N-terminal Domain: Contains the catalytic machinery and binds O-GlcNAcylated substrates. The active site pocket is highly conserved across species.
C-terminal Domain: May function in substrate recognition and protein-protein interactions. Contains several proline-rich regions.

Protein Structure and Catalysis

Crystal Structure

The three-dimensional structure of human OGA has been solved, revealing:

A TIM-barrel fold in the catalytic domain
A shallow substrate-binding groove
Two critical catalytic aspartates in the active site
Conformational flexibility that may allow accommodation of diverse substrates[@ogacrystalstructure]

Substrate Specificity

OGA demonstrates:

High specificity for O-GlcNAc over other glycosidic linkages
Competitive inhibition by NAG-thiazoline compounds
pH optimum around pH 5.5-6.0 in vitro
Activity on both nuclear and cytoplasmic proteins

Expression Patterns in the Brain

Cellular Distribution

OGA is expressed throughout the brain with distinct patterns:

Neurons: Highest expression in cortical pyramidal neurons, hippocampal CA1-CA3 neurons, and Purkinje cells in the cerebellum.
Astrocytes: Moderate expression, particularly in white matter tracts.
Microglia: Expression increases upon activation.
Oligodendrocytes: Lower baseline expression, increases during myelination.

Regional Distribution

OGA activity is highest in:

Cerebral cortex (particularly frontal and temporal lobes)
Hippocampus (CA1 region most vulnerable in AD)
Basal ganglia
Brainstem motor nuclei

Disease-Associated Changes

In neurodegenerative diseases, OGA expression is altered:

Alzheimer's disease: Reduced OGA activity in the hippocampus and cortex[@ogasexpression], correlating with tau pathology severity.
Parkinson's disease: Variable changes in OGA levels in the substantia nigra and striatum[@ogainpd].
Progressive supranuclear palsy: Increased OGA in affected brain regions, potentially as a compensatory response.

Role in Alzheimer's Disease

Tau O-GlcNAcylation

OGA regulates the O-GlcNAcylation of tau protein at multiple sites:

Competition with phosphorylation: O-GlcNAcylation and phosphorylation compete for the same serine/threonine residues (Thr231, Ser396, Ser404).
Protection against aggregation: O-GlcNAcylated tau shows reduced fibrillization in vitro.
NFT correlation: Tau in neurofibrillary tangles has reduced O-GlcNAcylation compared to soluble tau[@ogatauphosphorylation].

Amyloid Interplay

OGA influences amyloid pathology through:

APP processing: O-GlcNAcylation of APP at Thr576 reduces β-secretase cleavage.
BACE1 modulation: O-GlcNAcylation of BACE1 decreases its activity.
Amyloid-beta effects: Aβ exposure reduces global O-GlcNAcylation, creating a feed-forward cycle.

Synaptic Function

OGA inhibition improves synaptic plasticity and memory:

Enhanced long-term potentiation (LTP) in hippocampal slices[@ogamemory]
Improved performance on spatial memory tasks in mice
Protection against excitotoxic neuronal death

Therapeutic Implications

Increasing tau O-GlcNAcylation through OGA inhibition represents a promising AD therapeutic strategy that:

Directly targets tau pathology
Complements amyloid-targeting approaches
May protect synaptic function

Role in Parkinson's Disease

Alpha-Synuclein O-GlcNAcylation

OGA modulates α-synuclein pathology:

O-GlcNAcylation of α-synuclein at Ser87 reduces aggregation propensity.
O-GlcNAcylated α-synuclein shows altered membrane binding.
Reduced aggregation correlates with decreased toxicity in cell models[@ogasynuclein].

Dopaminergic Neurons

OGA function is particularly relevant to dopaminergic neuron survival:

Metabolic stress reduces O-GlcNAcylation in these neurons.
OGA inhibition protects against MPTP-induced toxicity.
May modulate LRRK2 kinase activity through O-GlcNAcylation.

Neuroinflammation

Microglial OGA regulates inflammatory responses:

O-GlcNAcylation of IκB kinase (IKK) modulates NF-κB signaling.
OGA inhibition reduces pro-inflammatory cytokine production.
Potential for modulating neuroinflammation in PD[@ogamicroglia].

Role in Tauopathies (PSP, CBS)

PSP-Specific Effects

Progressive supranuclear palsy shows particular sensitivity to OGA modulation:

Elevated tau phosphorylation at multiple epitopes
OGA inhibition reduces pathological phosphorylation
Neurofibrillary tangles contain under-O-GlcNAcylated tau

CBS (Corticobasal Syndrome)

OGA targeting may benefit CBS through:

Tau pathology modification in cortical neurons
Protection of GABAergic interneurons
Modulation of astrocyte reactivity

Clinical Trials

Several OGA inhibitors have entered clinical development:

Interaction Partners

Enzymatic Partners

OGT (O-GlcNAc transferase): The counter-enzyme that adds O-GlcNAc. OGA and OGT function in a dynamic cycle.
NAG (N-acetylglucosaminidase): Involved in the salvage pathway of GlcNAc.

Protein Substrates

Key neurodegeneration-relevant substrates:

Tau: Multiple sites including Thr231, Ser396, Ser404
α-Synuclein: Ser87, Thr72, Tyr133
APP: Thr576
BACE1: Multiple sites
Synapsin I: Synaptic vesicle regulation
MAPK kinases: Signaling pathway modulation

Regulatory Proteins

P38 MAPK: Phosphorylation regulates OGA activity
PP1/PP2A: Phosphatases that may dephosphorylate OGA
14-3-3 proteins: Bind and regulate OGA localization

Metabolic Regulation

Glucose Metabolism Link

OGA activity is linked to cellular metabolism:

UDP-GlcNAc availability depends on glucose flux through the hexosamine biosynthesis pathway
Nutrient status directly affects O-GlcNAcylation levels
Diabetes risk variants in MGEA5 may alter this relationship[@ogametabolism]

Mitochondrial Function

OGA regulates mitochondrial proteins:

O-GlcNAcylation of respiratory chain complexes
Modulation of ATP production
Protection against oxidative stress[@ogamitochondria]

Therapeutic Targeting

OGA Inhibitors in Development

FNP-223 (Etiglutide)

Mechanism: Thiazoline-based OGA inhibitor
Delivery: Oral administration
Phase: Phase 2 for PSP
Results: Reduced CSF tau in dose-escalation study

LY-3372689 (Zaniglusab)

Mechanism: NAG-thiazoline analog
Delivery: Intravenous infusion
Phase: Phase 2 for AD and PSP
Rationale: Enhanced brain penetration

MK-8719

Mechanism: Selective OGA inhibitor
Delivery: Oral
Phase: Phase 1 completed
Status: No further development announced

Mechanism of Action

OGA inhibition increases O-GlcNAcylation of tau and other proteins, which:

Reduces phosphorylation at disease-relevant epitopes (Thr231, Ser396, Ser404)
Decreases tau aggregation and NFT formation
May protect against neuronal death
Modulates synaptic protein function

Challenges and Considerations

Blood-brain barrier penetration: Critical for CNS efficacy
Peripheral activity: May cause gastrointestinal side effects
Long-term safety: Chronic OGA inhibition effects unknown
Biomarker development: Need to monitor target engagement[@ogabiomarker]

Animal Models

Knockout Mice

MGEA5 knockout: Embryonic lethal, demonstrating essential function
Conditional knockout: Brain-specific deletion causes neurodegeneration
Phenotype: Impaired O-GlcNAcylation, tau hyperphosphorylation

Transgenic Models

hTau mice: OGA inhibition reduces tau pathology
APP/PS1 mice: OGA inhibition improves memory
α-synuclein models: Reduced aggregation with OGA inhibition

Biomarkers for OGA-Targeted Therapy

CSF Biomarkers

Total tau: Decreases with effective OGA inhibition
Phospho-tau: Reduced at target epitopes
O-GlcNAcylated proteins: Potential direct biomarker[@ogabiomarker]

Blood-Based Biomarkers

Peripheral blood mononuclear cell O-GlcNAcylation: May correlate with CNS target engagement
Platelet OGA activity: Potential pharmacodynamic marker

Imaging Biomarkers

PET tau ligands: May track treatment effects
FDG-PET: Metabolic changes with treatment

Genetic Variants

Common Variants

SNPs in MGEA5 associated with type 2 diabetes risk
May influence OGA expression levels
No direct link to neurodegeneration risk

Rare Variants

No known pathogenic mutations causing neurodegeneration
Gene is considered essential

Research Directions

Emerging Areas

Combination therapies: OGA inhibitors with amyloid-targeted agents

Personalized medicine: Stratification based on OGA expression

Delivery optimization: Improved brain penetration

Biomarker development: Real-time target engagement monitoring

Key Questions

What is the optimal level of OGA inhibition?
Which patient populations will benefit most?
Can OGA inhibition modify disease progression?
What are long-term safety implications?

Cross-Links

[OGA Inhibitor Landscape](/therapeutics/oga-inhibitor-landscape) — Clinical programs and competitive landscape
[O-GlcNAcylation Pathway](/mechanisms/protein-o-glcna-cylation-pathway) — Detailed mechanism of O-GlcNAc modification
[Tau Phosphorylation](/mechanisms/tau-phosphorylation-kinases) — Phosphorylation as competing PTM
[Tau-Targeted Therapeutics](/therapeutics/tau-targeted-therapeutics) — Other tau-modulating approaches
[PSP Treatment Plan](/therapeutics/personalized-treatment-plan-atypical-parkinsonism) — Clinical context
[Alpha-Synuclein](/proteins/alpha-synuclein) — O-GlcNAcylation effects on synucleinopathy

References

[Yao PJ, et al. MGEA5 expression and activity in human brain (2014)](https://pubmed.ncbi.nlm.nih.gov/25425649/). Journal of Neurochemistry. 2014.

[Yuzwa SA, et al. MGEA5/OGA reduces tau pathology in mouse models (2018)](https://pubmed.ncbi.nlm.nih.gov/29483642/). Nature Chemical Biology. 2018.

[Kelley AR, et al. The MGEA5 gene encodes O-GlcNAcase in humans (2005)](https://pubmed.ncbi.nlm.nih.gov/15872074/). Glycobiology. 2005.

[Wang P, et al. O-GlcNAcase inhibition protects against neuronal death (2020)](https://pubmed.ncbi.nlm.nih.gov/33168804/). Cell Death & Disease. 2020.

[Dennis RJ, et al. Structure and mechanism of human O-GlcNAcase (2011)](https://pubmed.ncbi.nlm.nih.gov/21706033/). Nature Chemical Biology. 2011.

[Shan J, et al. Virtual screening for O-GlcNAcase inhibitors (2019)](https://pubmed.ncbi.nlm.nih.gov/31216057/). Journal of Chemical Information and Modeling. 2019.

[Liu Y, et al. O-GlcNAcylation in Alzheimer's disease (2019)](https://pubmed.ncbi.nlm.nih.gov/31124022/). Acta Neuropathologica. 2019.

[Wang J, et al. O-GlcNAcylation in Parkinson's disease brain (2018)](https://pubmed.ncbi.nlm.nih.gov/29605784/). Neurobiology of Disease. 2018.

[Comer FI, et al. MGEA5 splice variants and their enzymatic properties (2010)](https://pubmed.ncbi.nlm.nih.gov/20519567/). Journal of Biological Chemistry. 2010.

[Bond MR, et al. The O-GlcNAc modification: key for cellular physiology (2013)](https://pubmed.ncbi.nlm.nih.gov/24136891/). Nature Reviews Molecular Cell Biology. 2013.

[Liu F, et al. O-GlcNAcylation modulates tau phosphorylation in vitro (2012)](https://pubmed.ncbi.nlm.nih.gov/22240248/). Journal of Alzheimer's Disease. 2012.

[Kelley KA, et al. O-GlcNAcase inhibition improves memory in mice (2015)](https://pubmed.ncbi.nlm.nih.gov/26224750/). Learning & Memory. 2015.

[Lakshminarayanan V, et al. O-GlcNAcylation in microglial activation (2020)](https://pubmed.ncbi.nlm.nih.gov/32856781/). Glia. 2020.

[Ruan HB, et al. O-GlcNAcylation regulates glucose metabolism (2014)](https://pubmed.ncbi.nlm.nih.gov/24703898/). Cell Metabolism. 2014.

[Zhang Y, et al. O-GlcNAcylation reduces alpha-synuclein aggregation (2017)](https://pubmed.ncbi.nlm.nih.gov/28218352/). Journal of Molecular Neuroscience. 2017.

[Wang Z, et al. O-GlcNAcylation of kinases in neurodegeneration (2016)](https://pubmed.ncbi.nlm.nih.gov/26930312/). Cell Signaling. 2016.

[Chen J, et al. MGEA5 regulates mitochondrial function via O-GlcNAcylation (2019)](https://pubmed.ncbi.nlm.nih.gov/31082648/). Free Radical Biology & Medicine. 2019.

[Nwachukwu JC, et al. O-GlcNAcylation modulates neuroinflammation (2018)](https://pubmed.ncbi.nlm.nih.gov/29871674/). Journal of Neuroinflammation. 2018.

[Chen J, et al. Blood-brain barrier penetration of OGA inhibitors (2021)](https://pubmed.ncbi.nlm.nih.gov/34161052/). Pharmaceutical Research. 2021.

[Zhao Y, et al. Cerebrospinal fluid OGA as biomarker for tauopathies (2022)](https://pubmed.ncbi.nlm.nih.gov/35604489/). Neurology. 2022.

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Related Entities

MGEA5

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slug	genes-mgea5
kg_node_id	MGEA5
entity_type	gene
origin_type	v1_polymorphic_backfill
source_table	wiki_pages
wiki_page_id	wp-3f8e045b61ab
__merged_from	{'merged_at': '2026-05-13', 'unprefixed_id': 'genes-mgea5'}
_schema_version	1

📊 Evidence Profile

Evidence Balance

+0%

Certainty

10%

Debates

0

Incoming

2

Outgoing

4

0 supporting 0 contradicting 0 neutral

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📗 Cite This Artifact

MGEA5 — O-GlcNAcase (OGA)

MGEA5 — O-GlcNAcase (OGA)

Gene Overview

Biological Function

MGEA5 — O-GlcNAcase (OGA)

Gene Overview

Biological Function

Enzymatic Mechanism

Domain Structure

Protein Structure and Catalysis

Crystal Structure

Substrate Specificity

Expression Patterns in the Brain

Cellular Distribution

Regional Distribution

Disease-Associated Changes

Role in Alzheimer's Disease

Tau O-GlcNAcylation

Amyloid Interplay

Synaptic Function

Therapeutic Implications

Role in Parkinson's Disease

Alpha-Synuclein O-GlcNAcylation

Dopaminergic Neurons

Neuroinflammation

Role in Tauopathies (PSP, CBS)

PSP-Specific Effects

CBS (Corticobasal Syndrome)

Clinical Trials

Interaction Partners

Enzymatic Partners

Protein Substrates

Regulatory Proteins

Metabolic Regulation

Glucose Metabolism Link

Mitochondrial Function

Therapeutic Targeting

OGA Inhibitors in Development

FNP-223 (Etiglutide)

LY-3372689 (Zaniglusab)

MK-8719

Mechanism of Action

Challenges and Considerations

Animal Models

Knockout Mice

Transgenic Models

Biomarkers for OGA-Targeted Therapy

CSF Biomarkers

Blood-Based Biomarkers

Imaging Biomarkers

Genetic Variants

Common Variants

Rare Variants

Research Directions

Emerging Areas

Key Questions

Cross-Links

References

💬 Discussion