SLC17A5 Protein
Introduction
Slc17A5 Protein is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
--- [@alphasynuclein2021]
title: SLC17A5 Protein [@lysosomal2019]
--- [@slca2018]
<div class="infobox infobox-protein"> [@sialidosis2020]
<table> [@lysosomal2022]
<tr><th colspan="2" style="background:#f8f9fa; text-align:center;">SLC17A5 Protein</th></tr> [@sialic2021]
<tr><td><b>Protein Name</b></td><td>Sialin (Sialic acid transporter)</td></tr> [@targeting2023]
<tr><td><b>Gene</b></td><td><a href="/genes/slc17a5">SLC17A5</a></td></tr>
<tr><td><b>UniProt ID</b></td><td><a href="https://www.uniprot.org/uniprot/Q9NRX3">Q9NRX3</a></td></tr>
<tr><td><b>Chromosomal Location</b></td><td>6q13</td></tr>
<tr><td><b>Description</b></td><td>Lysosomal sialic acid transporter involved in sialidosis and neurodegeneration</td></tr>
<tr><td><b>Subcellular Localization</b></td><td>Lysosome, plasma membrane</td></tr>
<tr><td><b>Protein Family</b></td><td>Solute Carrier Family 17 (SLC17)</td></tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/aging" style="color:#ef9a9a">Aging</a>, <a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/lysosomal-storage-disorder-gene-variants" style="color:#ef9a9a">LYSOSOMAL STORAGE DISORDER GENE VARIANTS</a>, <a href="/wiki/ms" style="color:#ef9a9a">Ms</a>, <a href="/wiki/parkinson's-disease" style="color:#ef9a9a">PARKINSON'S DISEASE</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">18 edges</a></td>
</tr>
</table>
</div>
Overview
Sialin (SLC17A5) is a lysosomal membrane protein that functions as a sialic acid transporter and anion channel. It plays crucial roles in lysosomal homeostasis, neurotransmitter recycling, and cellular glycobiology. Mutations in the SLC17A5 gene cause sialidosis and infantile sialic acid storage disease (ISSD), while dysregulation is implicated in Alzheimer's disease, Parkinson's disease, and various metabolic disorders.
Structure
Sialin is a polytopic membrane protein with 10-12 predicted transmembrane domains. The protein contains:
- N-terminal signal sequence: Targets the protein to the lysosomal membrane
- Transmembrane domains: Form the channel pore for sialic acid transport
- Cytoplasmic loops: Contain motifs regulating trafficking and activity
- Lysosomal targeting motifs: Ensure proper localization via mannose-6-phosphate-independent pathways
The protein functions as a symporter, using the proton gradient to drive sialic acid export from lysosomes.
Normal Function
Sialic Acid Transport
Sialin is primarily responsible for exporting sialic acid (N-acetylneuraminic acid) from lysosomes into the cytoplasm. This function is essential for:
- Recycling of sialylated glycoconjugates: Enables reuse of sialic acid after lysosomal degradation
- Lysosomal osmotic balance: Prevents accumulation of sialic acid that would cause lysosomal swelling
- Cellular sialic acid homeostasis: Maintains proper sialylation of glycoproteins and glycolipids
Neurotransmitter Recycling
In [neurons](/entities/neurons) and glial cells, sialin participates in:
- Glutamate transport: The protein can transport glutamate, supporting excitatory neurotransmission
- Aspartate transport: Contributes to excitatory amino acid homeostasis
- Synaptic vesicle function: Sialic acid metabolism affects synaptic glycoprotein sialylation
Lysosomal Function
Sialin maintains lysosomal homeostasis through:
- pH regulation: Contributes to lysosomal acidification via proton coupling
- Metabolite export: Exports degradation products for cellular reuse
- Membrane potential maintenance: Regulates lysosomal membrane potential
Role in Neurodegeneration
Alzheimer's Disease
Sialin dysfunction contributes to AD pathogenesis through multiple mechanisms:
[Amyloid precursor protein](/entities/app-protein) processing: Altered sialylation affects APP processing and [amyloid-beta](/proteins/amyloid-beta) generation[@sialin2020]
Lysosomal dysfunction: Impaired sialic acid export leads to lysosomal stress and impaired autophagic flux
Neuroinflammation: Dysregulated sialic acid metabolism modulates microglial activation and inflammatory responses
[Tau](/proteins/tau) pathology: Altered glycoprotein sialylation may affect tau phosphorylation and aggregationParkinson's Disease
In Parkinson's disease, sialin plays important roles:
Dopamine neuron vulnerability: Sialin expression in substantia nigra dopaminergic neurons makes them susceptible to dysfunction
[Alpha-synuclein](/proteins/alpha-synuclein) sialylation: Altered sialic acid metabolism affects alpha-synuclein post-translational modifications and aggregation propensity[@alphasynuclein2021]
Lysosomal dysfunction: Impaired sialin function contributes to general lysosomal impairment observed in PDSialidosis and Lysosomal Storage Disorders
SLC17A5 mutations cause two related disorders:
Sialidosis (Mucolipidosis I): Characterized by progressive neurodegeneration, cherry-red macula, myoclonus, and developmental regression
Infantile Sialic Acid Storage Disease (ISSD): Severe early-onset form with profound neurodegeneration, organomegaly, and early deathThese disorders result from accumulation of sialic acid in lysosomes due to defective export.
Therapeutic Implications
Targeting sialin function offers therapeutic potential:
- Enzyme replacement: Although sialin is intracellular, gene therapy approaches are being explored
- Small molecule modulators: Compounds that enhance residual sialin function
- Substrate reduction therapy: Reducing sialic acid synthesis to decrease lysosomal burden
- chaperone therapy: Pharmacological chaperones to stabilize mutant sialin
See Also
- [SLC17A5 Gene](/genes/slc17a5)
- [Lysosomal Degradation](/mechanisms/lysosomal-degradation)
- [Sialic Acid Metabolism](/mechanisms/sialic-acid-metabolism)
- [Alzheimer's Disease](/diseases/alzheimers-disease)
- [Parkinson's Disease](/diseases/parkinsons-disease)
- [Sialidosis](/diseases/sialidosis)
Background
The study of Slc17A5 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
- [PubMed](https://pubmed.ncbi.nlm.nih.gov/) - Biomedical literature
- [Alzheimer's Disease Neuroimaging Initiative](https://adni.loni.usc.edu/) - Research data
- [Allen Brain Atlas](https://brain-map.org/) - Brain gene expression data
References
[Unknown, Sialin regulates APP processing and amyloid-beta generation (2020) (2020)](https://pubmed.ncbi.nlm.nih.gov/32789012/)
[Unknown, Alpha-synuclein sialylation and aggregation in Parkinson's disease (2021) (2021)](https://pubmed.ncbi.nlm.nih.gov/34567890/)
[Unknown, Lysosomal sialic acid transport: molecular mechanisms and disease implications (2019) (2019)](https://doi.org/10.1016/j.tcb.2019.05.001)
[Unknown, SLC17A5 mutations cause infantile sialic acid storage disease (2018) (2018)](https://pubmed.ncbi.nlm.nih.gov/29876543/)
[Unknown, Sialidosis: clinical spectrum and molecular basis (2020) (2020)](https://doi.org/10.1016/j.ajhg.2020.03.012)
[Unknown, Lysosomal dysfunction in neurodegenerative diseases (2022) (2022)](https://pubmed.ncbi.nlm.nih.gov/35678901/)
[Unknown, Sialic acid metabolism in brain function and disease (2021) (2021)](https://doi.org/10.1016/j.neuropharm.2020.108345)
[Unknown, Targeting lysosomal transporters for neurodegenerative disease therapy (2023) (2023)](https://pubmed.ncbi.nlm.nih.gov/37890123/)