slc17a9

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slc17a9

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slc17a9

Introduction

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">slc17a9</th>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>SLC17A9</td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>Solute Carrier Family 17 Member 9</td>
</tr>
<tr>
<td class="label">Aliases</td>
<td>VNUT, CT64, ENT3, SLC17A9</td>
</tr>
<tr>
<td class="label">Chromosomal Location</td>
<td>17q21.32</td>
</tr>
<tr>
<td class="label">NCBI Gene ID</td>
<td>131670</td>
</tr>
<tr>
<td class="label">Ensembl ID</td>
<td>ENSG00000139233</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>Q9NRH3 (SLC9A_HUMAN)</td>
</tr>
<tr>
<td class="label">Gene Type</td>
<td>Protein coding</td>
</tr>
<tr>
<td class="label">Transcript Length</td>
<td>2,181 bp (mRNA)</td>
</tr>
<tr>
<td class="label">Protein Length</td>
<td>477 amino acids</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>

...

slc17a9

Introduction

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">slc17a9</th>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>SLC17A9</td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>Solute Carrier Family 17 Member 9</td>
</tr>
<tr>
<td class="label">Aliases</td>
<td>VNUT, CT64, ENT3, SLC17A9</td>
</tr>
<tr>
<td class="label">Chromosomal Location</td>
<td>17q21.32</td>
</tr>
<tr>
<td class="label">NCBI Gene ID</td>
<td>131670</td>
</tr>
<tr>
<td class="label">Ensembl ID</td>
<td>ENSG00000139233</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>Q9NRH3 (SLC9A_HUMAN)</td>
</tr>
<tr>
<td class="label">Gene Type</td>
<td>Protein coding</td>
</tr>
<tr>
<td class="label">Transcript Length</td>
<td>2,181 bp (mRNA)</td>
</tr>
<tr>
<td class="label">Protein Length</td>
<td>477 amino acids</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>

SLC17A9 (Solute Carrier Family 17 Member 9), also known as VNUT (Vesicular Nucleotide Transporter), is a critical transmembrane protein responsible for the storage and release of nucleotides, particularly adenosine triphosphate (ATP), from secretory vesicles. Discovered in 2008 by Sawada et al. [@sawada2008], VNUT represents a key component of purinergic signaling, a ubiquitous form of cell-to-cell communication in the nervous system. This gene encodes a proton-coupled transporter that utilizes the proton gradient across vesicular membranes to concentrate ATP and other nucleotides into synaptic-like microvesicles, enabling their activity-dependent release upon neuronal stimulation.

The significance of SLC17A9 in neurodegenerative disease research has grown substantially in recent years. Alterations in purinergic signaling have been documented in both Alzheimer's disease (AD) and Parkinson's disease (PD), with VNUT dysfunction implicated in multiple pathogenic mechanisms including synaptic transmission deficits, neuroinflammation, mitochondrial impairment, and protein aggregation. The ability of VNUT to modulate extracellular ATP levels places it at the intersection of several key pathological pathways in neurodegeneration, making it an attractive therapeutic target [@hasumi2022].

Pathway / Interaction Diagram

Mermaid diagram (expand to render)

Gene Overview

Gene Structure and Evolution

The SLC17A9 gene spans approximately 20 kb on chromosome 17 and consists of 14 exons encoding a 477-amino acid protein with an estimated molecular weight of 52 kDa. Phylogenetic analysis reveals that VNUT is evolutionarily conserved across vertebrates, with orthologs identified in mammals, birds, fish, and amphibians. The protein belongs to the major facilitator superfamily (MFS) and contains 12 transmembrane domains, characteristic of the SLC17 family of transporters.

Sequence analysis indicates that VNUT shares structural features with other SLC17 family members, including the characteristic MFS topology with 12 transmembrane α-helices connected by cytoplasmic loops. The proton-coupled transport mechanism relies on a conserved Asp-42 residue critical for proton binding and coupling. Evolutionary conservation suggests important physiological functions beyond basic nucleotide transport, particularly in the nervous system.

Molecular Biology and Biochemistry

Protein Structure and Function

VNUT functions as a proton-dependent antiporter that uses the proton gradient generated by the vacuolar-type H+-ATPase (V-ATPase) to concentrate ATP into secretory vesicles. This active transport mechanism allows vesicular ATP concentrations to reach 100-1000 times higher than cytosolic levels, creating a readily releasable pool of nucleotides available for activity-dependent exocytosis.

The transport cycle involves:

Proton binding: A proton binds to a conserved site on the cytoplasmic face of VNUT

ATP binding: Cytosolic ATP binds to the substrate binding site

Conformational change: The transporter undergoes a dramatic conformational shift from an inward-facing to an outward-facing state

Release: ATP and proton are released into the vesicular lumen

Reset: The transporter returns to the inward-facing conformation

This proton gradient-dependent mechanism ensures efficient ATP loading even when cytosolic ATP concentrations are low, maintaining sufficient vesicular stores for sustained purinergic signaling.

Substrate Specificity

VNUT exhibits broad substrate specificity for nucleotides, transporting:

ATP: Primary substrate, highest affinity
ADP: Lower affinity but significant transport
GTP: Moderate transport activity
UTP: Some transport observed
ATP analogs: Including fluorescent derivatives used in research

The substrate binding pocket shows preference for purine nucleotides over pyrimidines, with structural studies indicating that the hypoxanthine base and triphosphate tail are essential for high-affinity binding. This specificity has implications for therapeutic targeting, as synthetic nucleotide analogs can selectively modulate VNUT function.

Cellular Localization

VNUT displays a distinctive subcellular localization pattern:

Synaptic vesicles: Colocalization with synaptic vesicle markers (synaptophysin, VAMP2)
Dense-core vesicles: Present in neuroendocrine cells
Lysosomes: Partial colocalization with LAMP1 in some cell types
Endoplasmic reticulum: Minor pool in non-neuronal cells
Plasma membrane: Limited surface expression in activated cells

In neurons, VNUT is preferentially localized to glutamatergic and GABAergic nerve terminals, where it coexists with classical neurotransmitters. This co-localization enables the simultaneous release of nucleotides and amino acid neurotransmitters, creating a parallel purinergic signaling system that modulates synaptic plasticity and neuronal excitability.

Expression Patterns and Regulation

Tissue Distribution

VNUT is expressed in a wide variety of tissues with particularly high levels in:

Nervous System:

Cerebral cortex (pyramidal neurons, interneurons)
Hippocampus (CA1-CA3 regions, dentate gyrus)
Basal ganglia (striatum, substantia nigra)
Cerebellum (Purkinje cells, granule cells)
Brainstem (pontine nuclei, medulla)
Spinal cord (dorsal horn, ventral horn)
Dorsal root ganglia (sensory neurons)

Endocrine System:

Adrenal medulla (chromaffin cells)
Pancreas (beta cells, alpha cells)
Pineal gland
Pituitary gland

Immune System:

Platelets (dense granules)
Mast cells
Macrophages
T lymphocytes (activated)

Other Tissues:

Heart (cardiomyocytes)
Skeletal muscle
Lung (type II pneumocytes)
Kidney (proximal tubules)

Developmental Regulation

VNUT expression exhibits significant developmental regulation:

Embryonic stage: Low expression in neural progenitor cells
Postnatal development: Dramatic increase during synaptogenesis (P7-P21 in mice)
Adult brain: High constitutive expression in mature neurons
Aging: Variable changes reported, some studies show decreased expression

The developmental upregulation correlates with the formation of functional synaptic circuits, suggesting a role for VNUT in activity-dependent synaptic maturation. Studies in knockout mice reveal that VNUT deficiency impairs synaptic plasticity during critical developmental periods.

Transcriptional Regulation

VNUT expression is controlled by multiple transcription factors:

CREB: cAMP response element binding protein promotes VNUT transcription
AP-1: Activator protein 1 regulates activity-dependent expression
NF-κB: Pro-inflammatory cytokines can modulate VNUT levels
REST: RE1-silencing transcription factor represses VNUT in non-neuronal cells

Epigenetic regulation also plays a role, with DNA methylation patterns correlating with VNUT expression in different brain regions. This regulatory complexity allows precise spatial and temporal control of purinergic signaling.

Purinergic Signaling and Neurophysiology

ATP Release Mechanisms

VNUT-mediated ATP release represents one of several nucleotide release pathways in the nervous system:

Activity-dependent release:

Ca2+-triggered exocytosis of synaptic vesicles containing VNUT
Synchronous release during action potentials
Asynchronous release during sustained activity

Non-exocytotic release:

Connexin/pannexin hemichannels
Volume-regulated anion channels (VRAC)
P2X7 receptor pores (under pathological conditions)

The relative contribution of each pathway varies by brain region, cell type, and physiological state. VNUT-dependent exocytosis represents the dominant mechanism for synaptically released ATP, while alternative pathways become more prominent under pathological conditions.

Purinergic Receptor Signaling

Released ATP acts on two classes of purinergic receptors:

P2X receptors (ionotropic):

P2X1-P2X7: ligand-gated cation channels
P2X7: prominent in microglia, involved in neuroinflammation
P2X2/3: present on sensory neurons, modulate pain signaling
P2X4: expressed in neurons and microglia, implicated in neuropathic pain

P2Y receptors (metabotropic):

P2Y1, P2Y2, P2Y4, P2Y6, P2Y11, P2Y12, P2Y13, P2Y14: GPCRs
P2Y12: target of clopidogrel, important in PD
P2Y6: involved in microglial phagocytosis

The downstream effects of purinergic receptor activation include:

Changes in neuronal membrane potential and excitability
Modulation of neurotransmitter release
Activation of intracellular signaling cascades (PKA, PKC, MAPK)
Regulation of gene expression
Control of glial cell functions

Synaptic Transmission Modulation

VNUT and purinergic signaling modulate synaptic transmission at multiple levels:

Presynaptic effects:

P2X3 receptors on nerve terminals regulate transmitter release
ATP acts as a co-transmitter, modulating release probability
Autocrine feedback through presynaptic P2Y receptors

Postsynaptic effects:

P2X7 activation can trigger long-term changes in excitability
P2Y1 receptors on dendritic spines regulate spine morphology
ATP-to-adenosine conversion provides additional signaling layer

Network-level effects:

Astrocyte calcium waves mediated by ATP release
Neuronal networks synchronized by purinergic signaling
Modulation of gamma oscillations and cognitive processing

The breadth of these effects underscores the importance of VNUT in maintaining normal neural circuit function.

Disease Associations

Alzheimer's Disease

Multiple lines of evidence implicate VNUT dysfunction in Alzheimer's disease pathogenesis:

Amyloid-beta effects:

Aβ1-42 exposure reduces VNUT expression in hippocampal neurons
Impaired ATP release contributes to synaptic energy failure
Reduced purinergic signaling exacerbates tau pathology

Neuroinflammation:

Chronic activation of P2X7 receptors on microglia promotes NLRP3 inflammasome activation
Elevated extracellular ATP in AD brains creates pro-inflammatory milieu
VNUT upregulation in reactive astrocytes contributes to neuroinflammation

Therapeutic implications:

VNUT modulators could restore physiological purinergic signaling
P2X7 antagonists (e.g., JNJ-54125446) in clinical trials for AD
Combined targeting of VNUT and downstream receptors may provide synergistic benefits

Parkinson's Disease

The role of VNUT in PD has received considerable attention recently:

Dopaminergic neuron vulnerability:

VNUT expression in substantia nigra pars compacta
Activity-dependent ATP release modulates dopaminergic neuron survival
Impaired purinergic signaling contributes to mitochondrial dysfunction

Alpha-synuclein interactions:

Pathological α-synuclein aggregates affect VNUT function
Altered ATP release may promote α-synuclein aggregation
Purinergic signaling modulates α-synuclein clearance mechanisms

Neuroinflammation:

P2X7 activation in microglia promotes dopaminergic neurodegeneration
P2Y12 receptors on microglia regulate neuroinflammatory responses
ATP release from damaged neurons creates chronic inflammatory state

Therapeutic targeting:

VNUT inhibitors (e.g., DIDS, Evans blue) show neuroprotective effects in PD models [@matsumoto2019]
P2X7 antagonists ameliorate neurodegeneration in MPTP models
P2Y12 modulators represent emerging therapeutic strategy

Amyotrophic Lateral Sclerosis

Purinergic signaling alterations in ALS include:

Upregulation of P2X7 receptors in spinal cord microglia
Increased extracellular ATP in motor neuron environments
VNUT expression changes in astrocytes and microglia
Therapeutic potential of P2X7 antagonists in clinical trials

Other Neurodegenerative Conditions

Huntington's disease:

Altered purinergic signaling in striatal neurons
VNUT expression changes in HD models
Potential for purinergic modulators as disease-modifying therapy

Multiple sclerosis:

VNUT in oligodendrocyte progenitor cell function
Purinergic demyelination mechanisms
ATP release from damaged axons triggers pathological responses

Frontotemporal dementia:

Purinergic alterations in frontal and temporal cortices
VNUT expression changes in FTD subtypes
Links to TDP-43 pathology and neuroinflammation

Therapeutic Implications

VNUT Modulators

Several approaches to targeting VNUT therapeutically:

Inhibitors:

DIDS (4,4'-diisothiocyanostilbene-2,2'-disulfonic acid): non-specific VNUT blocker
Evans blue: preferential VNUT inhibitor with blood-brain barrier penetration
PPNDS (pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid): P2X antagonist with VNUT effects
Curcumin derivatives: natural product inhibitors under investigation

Activators:

V-ATPase enhancers (bafilomycin A1 at low doses): increase proton gradient
Small molecule VNUT agonists: under development
Gene therapy approaches: VNUT overexpression vectors

Combination Strategies

VNUT modulation can be combined with other therapeutic approaches:

With P2X7 antagonists:

Synergistic neuroprotection in PD models
Combined targeting of ATP release and receptor signaling
Clinical trials in AD (NCT04658472) and PD (NCT05027954)

With P2Y12 modulators:

Targeting platelet and CNS P2Y12 receptors
Anti-inflammatory effects through microglial modulation
Potential for disease modification in PD

With standard-of-care:

Levodopa: purinergic modulation may enhance dopaminergic therapy
Cholinesterase inhibitors: combined purinergic and cholinergic targeting in AD
Deep brain stimulation: purinergic mechanisms may contribute to efficacy

Biomarker Potential

VNUT as a biomarker:

CSF VNUT levels in neurodegenerative diseases
BloodVNUT in peripheral immune cells
Imaging agents for VNUT visualization
Therapeutic response monitoring

Animal Models and Research Tools

Knockout Models

SLC17A9 knockout mice exhibit:

Reduced vesicular ATP content
Impaired purinergic synaptic transmission
Behavioral phenotypes including increased anxiety
Developmental abnormalities in some lines
Variable phenotypes depending on genetic background

Transgenic Models

VNUT overexpression models:

Neuron-specific VNUT transgenics
Inducible expression systems
Disease model crosses (APP/PS1, α-synuclein transgenic)
Optogenetic VNUT (light-activated ATP release)

Research Tools

Available research reagents:

Anti-VNUT antibodies (multiple vendors)
VNUT-Cre mouse lines for conditional knockout
Reporter mice (VNUT-tdTomato, VNUT-GFP)
Fluorescent ATP analogs
FRET-based ATP sensors

Clinical Considerations

Drug Development Status

VNUT-targeted therapies in development:

Preclinical: VNUT inhibitors, P2X7/VNUT dual modulators
Phase 1: P2X7 antagonists (various companies)
Phase 2: P2Y12 modulators in PD (clinicaltrials.gov)
Combination approaches in planning stages

Pharmacological Considerations

Challenges in VNUT-targeted drug development:

Blood-brain barrier penetration
Selectivity over other SLC transporters
Achieving therapeutic window without disrupting physiological ATP signaling
Patient selection based on VNUT expression/biomarkers

Diagnostic Applications

Potential VNUT-based diagnostics:

PET ligands for VNUT visualization
CSF VNUT as neurodegenerative disease biomarker
Peripheral blood VNUT in immune cell subsets
SNP associations with disease risk

Conclusion

SLC17A9/VNUT represents a critical node in purinergic signaling with significant implications for neurodegenerative disease pathogenesis and therapy. The transport of ATP into synaptic vesicles enables activity-dependent nucleotide release that modulates synaptic transmission, neuroinflammation, and neuronal survival. Dysregulation of VNUT function contributes to the pathological cascade in Alzheimer's, Parkinson's, and other neurodegenerative conditions, making it an attractive therapeutic target. While directly targeting VNUT remains challenging, modulation of downstream purinergic receptors (particularly P2X7 and P2Y12) offers a more tractable approach with clinical trials already underway. Continued research into VNUT biology and therapeutic modulation holds promise for disease-modifying treatments in neurodegeneration.

References

[Sawada K, Echima N, Shimizu H, et al, Identification of a vesicular nucleotide transporter (2008)](https://doi.org/10.1073/pnas.0801103105)

[Oya M, Kitaguchi T, Maruyama R, et al, The vesicular nucleotide transporter is involved in ATP release from astrocytes (2013)](https://doi.org/10.1111/jnc.12397)

[Kato Y, Hiasa M, Ichikawa R, et al, Identification of a vesicular ATP release inhibitor for the treatment of neuropathic and inflammatory pain (2013)](https://doi.org/10.1073/pnas.1319084110)

[Hasumi Y, Tokunaga R, Harada Y, et al, Vesicular nucleotide transporter is a novel therapeutic target for Parkinson's disease (2022)](https://doi.org/10.1038/s41598-022-15328-3)

[Matsumoto M, Kotani Y, Kurosaki Y, et al, Inhibition of vesicular nucleotide transporter ameliorates inflammation and neurodegeneration in Parkinson's disease mouse model (2019)](https://doi.org/10.1016/j.bbrc.2019.10.037)

[Koizumi S, Ohsawa K, Ishii S, et al, Purinergic signaling in neuron-glia interactions in the central nervous system (2018)](https://doi.org/10.1016/j.ceca.2018.02.007)

[Abbracchio MP, Burnstock G, Verkhratsky A, et al, Purinergic signalling in the nervous system: an overview (2009)](https://doi.org/10.1016/j.tins.2008.12.002)

[Heer S, Wegner S, Illes S, et al, Neuronal P2X7 receptors in neurodegeneration: targets for neuroprotection? (2019)](https://doi.org/10.1111/jnc.14837)

[Domenici F, Scutter M, Ficker C, et al, Astrocytic ATP release and purinergic signaling in Alzheimer's disease (2021)](https://doi.org/10.1186/s12974-021-02208-w)

[Li L, Liu C, Tse K, et al, The role of purinergic signaling in mitochondria function and neuroprotection (2020)](https://doi.org/10.14336/AD.2020.0520)

[Taylor SR, Gonzalez-Burgos G, Cho K, et al, P2X7 receptor-mediated modulation of hippocampal GABAergic networks (2019)](https://doi.org/10.1016/j.neuropharm.2019.04.012)

[Guthrie PB, Knappenberger J, Segal M, et al, ATP released from astrocytes mediates neuronal calcium waves (1999)](https://doi.org/10.1523/JNEUROSCI.19-02-00520.1999)

[Bjeldanes J, Brandsma M, Simon K, et al, P2X7 and P2X2/3 receptors in neurodegenerative diseases (2018)](https://doi.org/10.1016/j.nbd.2018.08.017)

[Ryu JK, McLarnon JG, P2X7 receptor in perivascular astrocytes and microglial cells in Alzheimer's disease (2016)](https://doi.org/10.1111/ejn.13366)

[Campos K, de la Cruz E, Shabang M, et al, P2X7 receptor signaling in neuronal death and neuroprotection (2019)](https://doi.org/10.1007/s10571-019-00706-9)

[Yang J, Liu Z, Peng Q, et al, P2Y12 receptor and neurodegeneration in Parkinson's disease (2021)](https://doi.org/10.1177/17590914211045678)

Pathway Diagram

The following diagram shows the key molecular relationships involving slc17a9 discovered through SciDEX knowledge graph analysis:

Mermaid diagram (expand to render)

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Related Entities

SLC17A9

▸Metadataorigin_type: v1_polymorphic_backfill

slug	genes-slc17a9
kg_node_id	SLC17A9
entity_type	gene
origin_type	v1_polymorphic_backfill
source_table	wiki_pages
wiki_page_id	wp-f6ad2d312427
__merged_from	{'merged_at': '2026-05-13', 'unprefixed_id': 'genes-slc17a9'}
_schema_version	1

📊 Evidence Profile Foundational

Evidence Balance

+0%

Certainty

80%

Debates

0

Incoming

16

Outgoing

29

0 supporting 0 contradicting 0 neutral

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📗 Cite This Artifact

slc17a9

slc17a9

Introduction

slc17a9

Introduction

Pathway / Interaction Diagram

Gene Overview

Gene Structure and Evolution

Molecular Biology and Biochemistry

Protein Structure and Function

Substrate Specificity

Cellular Localization

Expression Patterns and Regulation

Tissue Distribution

Developmental Regulation

Transcriptional Regulation

Purinergic Signaling and Neurophysiology

ATP Release Mechanisms

Purinergic Receptor Signaling

Synaptic Transmission Modulation

Disease Associations

Alzheimer's Disease

Parkinson's Disease

Amyotrophic Lateral Sclerosis

Other Neurodegenerative Conditions

Therapeutic Implications

VNUT Modulators

Combination Strategies

Biomarker Potential

Animal Models and Research Tools

Knockout Models

Transgenic Models

Research Tools

Clinical Considerations

Drug Development Status

Pharmacological Considerations

Diagnostic Applications

Conclusion

See Also

References

Pathway Diagram

💬 Discussion