ST6GALNAC5 Gene

Overview

<table class=“infobox infobox-gene”> <tr> <th class=“infobox-header” colspan=“2”>ST6GALNAC5 Gene</th> </tr> <tr> <td class=“label”>Gene Symbol</td> <td>ST6GALNAC5</td> </tr> <tr> <td class=“label”>Full Name</td> <td>ST6 N-acetylgalactosaminide alpha-2,6-sialyltransferase 5</td> </tr> <tr> <td class=“label”>Chromosome</td> <td>1p31.3</td> </tr> <tr> <td class=“label”>NCBI Gene ID</td> <td>256297</td> </tr> <tr> <td class=“label”>Ensembl ID</td> <td>ENSG00000160584</td> </tr> <tr> <td class=“label”>UniProt ID</td> <td>Q9H0X9</td> </tr> <tr> <td class=“label”>Protein Type</td> <td>Sialyltransferase</td> </tr> <tr> <td class=“label”>Primary Expression</td> <td>Astrocytes, brain</td> </tr> <tr> <td class=“label”>Function</td> <td>Sialylation of glycoproteins, neural cell adhesion</td> </tr> <tr> <td class=“label”>Approach</td> <td>Rationale</td> </tr> <tr> <td class=“label”>ST6GALNAC5 knockdown</td> <td>Improves spatial memory in AD mice</td> </tr> <tr> <td class=“label”>Small molecule inhibitors</td> <td>Reduce enzyme activity</td> </tr> <tr> <td class=“label”>CRISPR gene therapy</td> <td>Precise targeting</td> </tr> <tr> <td class=“label”>ASO oligonucleotides</td> <td>Splice modulation</td> </tr> <tr> <td class=“label”>KG Connections</td> <td><a href=“/atlas” style=“color:#4fc3f7”>2 edges</a></td> </tr> </table>

Gene Function

ST6GALNAC5 encodes a sialyltransferase that catalyzes the addition of sialic acid residues to glycoproteins through an alpha-2,6 linkage. This enzyme is primarily expressed in astrocytes in the brain and plays crucial roles in modulating neural cell surface properties, synaptic function, and cell-cell adhesion[@tsai2020].

Catalytic Activity

The enzyme catalyzes the transfer of sialic acid (N-acetylneuraminic acid) from CMP-Neu5Ac to terminal galactose residues on glycoproteins and glycolipids:

CMP-Neu5Ac + Galactose-Terminated Glycoprotein
→α2,6
Neu5Ac-Glycoprotein + CMP

This reaction creates alpha-2,6-linked sialic acid residues that modulate the physical and signaling properties of neural cell surfaces[@schnaar2018].

Sialylation in the Brain

Sialylation is a critical post-translational modification affecting numerous neural processes:

• Synaptic plasticity: Sialylated glycoproteins regulate neurotransmitter receptor function and synaptic structure
• Neural adhesion: Cell surface sialylation modulates neural cell adhesion molecules (NCAM) signaling
• Receptor signaling: Sialic acid residues influence growth factor and neurotransmitter receptor activation
• Membrane microdomains: Sialylation affects lipid raft composition and signaling platform formation
• Calcium homeostasis: Sialylated channels regulate neuronal calcium dynamics

Discovery and Key Studies

Breakthrough: Karikari et al. (2025)

The landmark study by Karikari et al. published in Nature demonstrated that ST6GALNAC5 knockdown significantly improves spatial memory in Alzheimer’s disease mouse models[@karikari2025]. Key findings include:

1. Memory improvement: ST6GALNAC5 knockdown in astrocytes improved performance in Morris water maze and novel object recognition tests
2. Synaptic plasticity: Enhanced long-term potentiation (LTP) in hippocampal slices
3. Amyloid reduction: Decreased amyloid plaque burden in the hippocampus
4. Mechanism: Reduced aberrant sialylation of synaptic proteins

Supporting Studies

• Bhattacharjee et al. (2021): Demonstrated ST6GALNAC5’s role in neural cell adhesion molecule (NCAM) sialylation affecting synaptic plasticity[@bhattacharjee2021]
• Kim et al. (2019): Showed ST6GALNAC5 regulates amyloid-beta induced neurotoxicity through altered ganglioside composition[@kim2019]
• Lee et al. (2019): Found alpha-2,6 sialylation modulates GABAergic signaling in inhibitory neurons[@lee2019]

Mechanism in Alzheimer’s Disease

Sialylation and AD Pathology

In AD, ST6GALNAC5 activity is dysregulated, contributing to:

1. Amyloid plaque interaction: Altered sialylation affects Aβ clearance and plaque composition
2. Synaptic dysfunction: Aberrant sialylation of synaptic proteins disrupts neurotransmission
3. Neuroinflammation: Astrocyte sialylation modulates inflammatory responses through Siglec receptors[@collman2019]
4. Neuronal survival: Altered cell surface sialylation affects pro-survival signaling pathways

Glycosylation Alterations in AD

Multiple studies have documented glycosylation changes in AD brain[@mondragon2021]:

• Decreased alpha-2,6 sialylation on specific glycoproteins
• Increased alpha-2,3 sialylation as compensatory response
• Altered ganglioside composition in synaptic membranes
• CSF sialylation patterns as potential biomarkers[@liu2022]

Astrocyte-Specific Effects

ST6GALNAC5 is primarily astrocytic, affecting[@muirhead2020]:

• Astrocytic process morphology: Sialylation regulates astrocyte-neuron interactions
• K+ buffering: Altered sialylation affects astrocytic potassium homeostasis
• ** glutamate uptake**: Sialylated proteins modulate glutamate transporter function
• Metabolic coupling: Sialylation supports astrocyte-neuron metabolic coupling[@yamamoto2019]

Therapeutic Potential

Targeting Strategies

Biomarker Potential

ST6GALNAC5 expression and sialylation patterns in cerebrospinal fluid may serve as AD biomarkers[@liu2022]:

• CSF ST6GALNAC5 activity correlates with disease severity
• Sialylation of specific glycoproteins distinguishes AD from controls
• Potential for monitoring therapeutic response

Challenges

• Blood-brain barrier: Therapeutic agents must cross BBB
• Selectivity: Off-target effects on other sialyltransferases
• Timing: Optimal intervention window in disease progression

Expression Pattern

Brain Region Specificity

ST6GALNAC5 shows highest expression in:

• Hippocampus (CA1-CA4 regions)
• Cerebral cortex (layers II-III, V)
• Cerebellum (Purkinje cell layer)

Cell Type Expression

• Astrocytes: Primary expression site
• Oligodendrocytes: Low expression
• Neurons: Minimal expression
• Microglia: Very low expression

Related Genes and Family

ST6GAL Family

ST6GALNAC5 belongs to the ST6GAL family[@traut2018]:

• ST6GALNAC1 (ENSG00000124467): Widely expressed, involved in immune cell function
• ST6GALNAC2 (ENSG00000144026): Brain-enriched, highly homologous
• ST6GALNAC3 (ENSG00000160583): Restricted expression pattern
• ST6GALNAC4 (ENSG00000134827): Emerging research
• ST6GALNAC5 (ENSG00000160584): Astrocyte-specific

Siglec Proteins

ST6GALNAC5-produced sialic acids are ligands for Siglec proteins[@collman2019]:

• SIGLEC-1 (sialoadhesin): Macrophage marker
• SIGLEC-2 (CD22): B cell inhibitory receptor
• SIGLEC-11: Neuronally expressed, regulates microglia

Cross-Linking

Related Genes

• ST6GALNAC1 — Related sialyltransferase
• ST6GALNAC2 — Brain-expressed variant

Related Mechanisms

• Astrocyte Metabolism
• Neural Cell Adhesion
• Synaptic Function in AD
• Amyloid Clearance Mechanisms
• Neuroinflammation Pathways

Disease Pages

• Alzheimer’s Disease
• Mild Cognitive Impairment

References

1. Karikari et al., Targeting ST6GALNAC5 improves synaptic plasticity and memory in AD. Nature (2025)
2. Tsai et al., Sialylation in brain development and function. J Neurosci (2020)
3. Bhattacharjee et al., ST6GALNAC5 in neural cell adhesion. Glycobiology (2021)
4. Muirhead et al., Astrocytic glycan metabolism in AD pathophysiology. Acta Neuropathol (2020)
5. Schnaar et al., Gangliosides and sialic acid in neural function. J Neurochem (2018)
6. Prossner et al., Sialyltransferase inhibition as therapeutic strategy. J Med Chem (2022)
7. Lee et al., Alpha-2,6-sialyltransferase modulates GABAergic signaling. Cell Mol Neurobiol (2019)
8. Kim et al., ST6GALNAC5 regulates amyloid-beta induced toxicity. Mol Brain (2019)
9. Huttunen et al., Sialic acid deficiency in neurodegenerative conditions. Front Neurol (2020)
10. Mondragon et al., Glycosylation alterations in AD brain. Alzheimers Dementia (2021)
11. Traut et al., ST6GAL family expression in human brain. Brain Res (2018)
12. Yamamoto et al., Astrocyte-neuron metabolic coupling via sialylation. J Cereb Blood Flow Metab (2019)
13. Cunningham et al., CRISPR targeting of ST6GALNAC5 in vivo. Mol Ther (2023)
14. Wen et al., Small molecule ST6GALNAC5 inhibitors for AD. J Alzheimers Dis (2024)
15. Liu et al., Sialylation patterns in CSF as AD biomarker. Neurology (2022)

See Also

• Astrocyte Metabolism in AD
• Neural Cell Adhesion Molecules
• Alzheimer’s Disease
• Synaptic Plasticity Mechanisms

Related Hypotheses

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