NT5E Protein
Introduction
CD73 (Cluster of Differentiation 73), also known as Ecto-5'-Nucleotidase (NT5E), is a glycosylphosphatidylinositol (GPI)-anchored cell surface enzyme that catalyzes the hydrolysis of extracellular nucleotides to adenosine. As the rate-limiting enzyme in adenosine production, CD73 plays pivotal roles in purinergic signaling, immune regulation, neuroprotection, and cellular energy balance. This protein is widely expressed in the central nervous system (CNS), where it modulates synaptic transmission, neuroinflammation, and blood-brain barrier (BBB) function.
--- [@adenosine]
title: NT5E Protein [@receptors]
description: Protein page for CD73 / Ecto-5'-Nucleotidase [@neuroinflammation]
--- [@structure]
<div class="infobox infobox-protein"> [@adenosinea]
| | | [@stroke]
|---|---| [@targeting]
| Protein Name | CD73 / Ecto-5'-Nucleotidase |
| Gene | [NT5E](/proteins/nt5e-protein) |
| UniProt ID | [P21589](https://www.uniprot.org/uniprot/P21589) |
| PDB ID | 6A75, 4H2O |
| Molecular Weight | 70 kDa (dimer) |
| Subcellular Localization | Cell surface (GPI-anchored), cytoplasm |
| Protein Family | Ecto-nucleotidases, 5'-nucleotidase family |
| Expression | Broad: neurons, astrocytes, microglia, endothelial cells, immune cells |
</div>
Overview
...NT5E Protein
Introduction
CD73 (Cluster of Differentiation 73), also known as Ecto-5'-Nucleotidase (NT5E), is a glycosylphosphatidylinositol (GPI)-anchored cell surface enzyme that catalyzes the hydrolysis of extracellular nucleotides to adenosine. As the rate-limiting enzyme in adenosine production, CD73 plays pivotal roles in purinergic signaling, immune regulation, neuroprotection, and cellular energy balance. This protein is widely expressed in the central nervous system (CNS), where it modulates synaptic transmission, neuroinflammation, and blood-brain barrier (BBB) function.
--- [@adenosine]
title: NT5E Protein [@receptors]
description: Protein page for CD73 / Ecto-5'-Nucleotidase [@neuroinflammation]
--- [@structure]
<div class="infobox infobox-protein"> [@adenosinea]
| | | [@stroke]
|---|---| [@targeting]
| Protein Name | CD73 / Ecto-5'-Nucleotidase |
| Gene | [NT5E](/proteins/nt5e-protein) |
| UniProt ID | [P21589](https://www.uniprot.org/uniprot/P21589) |
| PDB ID | 6A75, 4H2O |
| Molecular Weight | 70 kDa (dimer) |
| Subcellular Localization | Cell surface (GPI-anchored), cytoplasm |
| Protein Family | Ecto-nucleotidases, 5'-nucleotidase family |
| Expression | Broad: neurons, astrocytes, microglia, endothelial cells, immune cells |
</div>
Overview
Mermaid diagram (expand to render)
CD73 is a glycosylphosphatidylinositol (GPI)-anchored enzyme that converts extracellular AMP to adenosine. As the rate-limiting enzyme in adenosine production, CD73 plays critical roles in purinergic signaling, immune regulation, neuroprotection, and synaptic transmission. CD73 hydrolyzes extracellular AMP to adenosine, producing the majority of extracellular adenosine in tissues. This adenosine signals through purinergic receptors (A1, A2A, A2B, A3) to modulate synaptic transmission, neuronal excitability, and glial function. CD73 is essential for astrocyte-neuron metabolic coupling, microglial surveillance, and blood-brain barrier regulation.
Protein Structure
Domain Architecture
CD73 is a homodimeric enzyme with each subunit containing:
- N-terminal domain (~320 aa): Catalytic site with metal-binding motifs
- C-terminal domain (~280 aa): Dimerization and substrate binding
- GPI anchor: C-terminal attachment to plasma membrane
Catalytic Mechanism
- Requires zinc ions (Zn²⁺) for activity
- Two-step hydrolysis: AMP → adenosine + phosphate
- Rate-limiting step in adenosine production
- Allosteric regulation by nucleotides
Post-Translational Modifications
| Modification | Site | Functional Impact |
|--------------|------|-------------------|
| N-glycosylation | Multiple sites | Protein stability, localization |
| GPI anchor | C-terminus | Membrane attachment |
| Disulfide bonds | 8 cysteines | Structural stability |
Normal Function
Purinergic Signaling
CD73 is the primary source of extracellular adenosine:
- Hydrolyzes AMP to adenosine
- Regulates purinergic receptor activation
- Modulates synaptic plasticity
- Controls neuronal excitability
Adenosine Receptor Signaling
| Receptor | Distribution | Function |
|----------|--------------|----------|
| A1 | Wide ([hippocampus](/brain-regions/hippocampus), cortex) | Inhibitory, neuroprotection |
| A2A | Striatum, immune cells | Pro-inflammatory, motor control |
| A2B | Low basal, induced | Vascular, inflammatory |
| A3 | Variable | Complex, tissue-specific |
Neurophysiological Roles
- Synaptic transmission: Modulates glutamate and GABA release
- Metabolic coupling: Astrocyte-neuron adenosine signaling
- Sleep-wake cycle: Adenosine accumulation promotes sleep
- Microglial surveillance: Basal adenosine tone
Immune Regulation
- Inhibits T cell activation
- Promotes regulatory T cell function
- Modulates macrophage polarization
- Anti-inflammatory in chronic disease
Expression in the CNS
Cell Type Distribution
| Cell Type | Expression Level | Key Functions |
|-----------|-----------------|---------------|
| [Astrocytes](/cell-types/astrocytes) | High | Metabolic coupling, K⁺ clearance |
| [Neurons](/cell-types/neurons) | Moderate | Synaptic modulation |
| [Microglia](/cell-types/microglia) | Low-Moderate | Immune surveillance |
| Endothelial Cells | High | [BBB](/entities/blood-brain-barrier) function |
| Oligodendrocytes | Low | Myelin maintenance |
Role in Disease
Alzheimer's Disease
In [Alzheimer's disease](/diseases/alzheimers-disease):
- Reduced CD73 activity in AD brains
- Adenosine deficiency contributes to cognitive impairment
- [Aβ](/proteins/amyloid-beta) affects CD73 expression on glia
- Therapeutic potential of CD73 modulation
Parkinson's Disease
In [Parkinson's disease](/diseases/parkinsons-disease):
- A2A receptor antagonists (caffeine) reduce PD risk
- CD73 modulates dopaminergic neuron survival
- Adenosine signaling in basal ganglia
- Therapeutic target for motor symptoms
Multiple Sclerosis
In [multiple sclerosis](/diseases/multiple-sclerosis):
- CD73 deficiency on T cells
- Immune tolerance via adenosine
- Demyelination and remyelination
- Therapeutic target
Stroke and Ischemia
Following cerebral ischemia:
- CD73-derived adenosine is neuroprotective
- A1 receptor activation reduces infarct size
- Post-ischemic inflammation modulation
Cancer
- Overexpression in many tumors
- Immunosuppressive adenosine production
- Target for cancer immunotherapy
Therapeutic Implications
Drug Development
| Drug/Compound | Target | Status |
|---------------|--------|--------|
| CD73 inhibitors | Enzymatic activity | Cancer clinical trials |
| A2A antagonists | A2A receptor | Parkinson's trials |
| A2A agonists | A2A receptor | Neuroprotection |
Potential Neurodegeneration Applications
- Adenosine enhancement strategies
- A2A receptor modulation
- BBB-penetrant compounds
Antibodies
- Anti-CD73 (CD39/CD73 panel)
- Functional blocking antibodies
- Flow cytometry panels
Mouse Models
- NT5E knockout mice
- Conditional deletion in CNS
- Transgenic overexpression
Assays
- Enzyme activity (colorimetric, fluorometric)
- Adenosine measurement (HPLC, mass spec)
- Receptor binding studies
See Also
- [Proteins Index](/proteins)
- [NT5E Gene](/proteins/nt5e-protein)
- [Purinergic Signaling Pathway](/mechanisms/purigenic-signaling-pathway)
- [Adenosine Signaling](/mechanisms/adenosine-signaling)
- [Neuroinflammation Pathway](/mechanisms/neuroinflammation-pathway)
- [Astrocytes](/cell-types/astrocytes)
- [Microglia](/cell-types/microglia)
Background
The study of Nt5E Protein has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
External Links
- [UniProt - NT5E](https://www.uniprot.org/uniprot/P21589)
- [PDB - CD73](https://www.rcsb.org/structure/6A75)
- [NCBI Protein - NT5E](https://www.ncbi.nlm.nih.gov/protein)
- [GeneCards - NT5E](https://www.genecards.org/cgi-bin/carddisp.pl?gene=NT5E)
References
[Unknown, - CD73 in neural function (n.d.)](https://pubmed.ncbi.nlm.nih.gov/23479634/)
[Unknown, - CD73 and adenosine in Alzheimer's disease (n.d.)](https://pubmed.ncbi.nlm.nih.gov/28947065/)
[Unknown, - A2A receptors in Parkinson's disease (n.d.)](https://pubmed.ncbi.nlm.nih.gov/28455230/)
[Unknown, - CD73 in neuroinflammation and multiple sclerosis (n.d.)](https://pubmed.ncbi.nlm.nih.gov/31270389/)
[Unknown, - CD73 structure and mechanism (n.d.)](https://pubmed.ncbi.nlm.nih.gov/29843652/)
[Unknown, - Adenosine signaling in the CNS (n.d.)](https://pubmed.ncbi.nlm.nih.gov/26700745/)
[Unknown, - CD73 in stroke and ischemia (n.d.)](https://pubmed.ncbi.nlm.nih.gov/32513884/)
[Unknown, - Targeting CD73 in cancer (n.d.)](https://pubmed.ncbi.nlm.nih.gov/33649903/)Pathway Diagram
The following diagram shows the key molecular relationships involving NT5E Protein discovered through SciDEX knowledge graph analysis:
Mermaid diagram (expand to render)