Version history

{
  "content_md": "# ST6GALNAC5 Gene\n\n## Overview\n\n\n```mermaid\nflowchart TD\n    ent_gene_20de1861[\"ent-gene-20de1861\"]\n    ent_gene_20de1861_1[\"Gene\"]\n    ent_gene_20de1861 -->|\"related to\"| ent_gene_20de1861_1\n    style ent_gene_20de1861_1 fill:#81c784,stroke:#333,color:#000\n    ent_gene_20de1861_2[\"table\"]\n    ent_gene_20de1861 -->|\"related to\"| ent_gene_20de1861_2\n    style ent_gene_20de1861_2 fill:#81c784,stroke:#333,color:#000\n    ent_gene_20de1861_3[\"class\"]\n    ent_gene_20de1861 -->|\"related to\"| ent_gene_20de1861_3\n    style ent_gene_20de1861_3 fill:#81c784,stroke:#333,color:#000\n    style ent_gene_20de1861 fill:#4fc3f7,stroke:#333,color:#000\n```\n\n<table class=\"infobox infobox-gene\">\n  <tr>\n    <th class=\"infobox-header\" colspan=\"2\">ST6GALNAC5 Gene</th>\n  </tr>\n  <tr>\n    <td class=\"label\">Gene Symbol</td>\n    <td>ST6GALNAC5</td>\n  </tr>\n  <tr>\n    <td class=\"label\">Full Name</td>\n    <td>ST6 N-acetylgalactosaminide alpha-2,6-sialyltransferase 5</td>\n  </tr>\n  <tr>\n    <td class=\"label\">Chromosome</td>\n    <td>1p31.3</td>\n  </tr>\n  <tr>\n    <td class=\"label\">NCBI Gene ID</td>\n    <td>256297</td>\n  </tr>\n  <tr>\n    <td class=\"label\">Ensembl ID</td>\n    <td>ENSG00000160584</td>\n  </tr>\n  <tr>\n    <td class=\"label\">UniProt ID</td>\n    <td>Q9H0X9</td>\n  </tr>\n  <tr>\n    <td class=\"label\">Protein Type</td>\n    <td>Sialyltransferase</td>\n  </tr>\n  <tr>\n    <td class=\"label\">Primary Expression</td>\n    <td>Astrocytes, brain</td>\n  </tr>\n  <tr>\n    <td class=\"label\">Function</td>\n    <td>Sialylation of glycoproteins, neural cell adhesion</td>\n  </tr>\n  <tr>\n    <td class=\"label\">Approach</td>\n    <td>Rationale</td>\n  </tr>\n  <tr>\n    <td class=\"label\">ST6GALNAC5 knockdown</td>\n    <td>Improves spatial memory in AD mice</td>\n  </tr>\n  <tr>\n    <td class=\"label\">Small molecule inhibitors</td>\n    <td>Reduce enzyme activity</td>\n  </tr>\n  <tr>\n    <td class=\"label\">CRISPR gene therapy</td>\n    <td>Precise targeting</td>\n  </tr>\n  <tr>\n    <td class=\"label\">ASO oligonucleotides</td>\n    <td>Splice modulation</td>\n  </tr>\n  <tr>\n    <td class=\"label\">KG Connections</td>\n    <td><a href=\"/atlas\" style=\"color:#4fc3f7\">2 edges</a></td>\n  </tr>\n</table>\n\n## Gene Function\n\n**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].\n\n### Catalytic Activity\n\nThe enzyme catalyzes the transfer of sialic acid (N-acetylneuraminic acid) from CMP-Neu5Ac to terminal galactose residues on glycoproteins and glycolipids:\n\n```\nCMP-Neu5Ac + Galactose-Terminated Glycoprotein\n→α2,6\nNeu5Ac-Glycoprotein + CMP\n```\n\nThis reaction creates alpha-2,6-linked sialic acid residues that modulate the physical and signaling properties of neural cell surfaces[@schnaar2018].\n\n### Sialylation in the Brain\n\nSialylation is a critical post-translational modification affecting numerous neural processes:\n\n- **Synaptic plasticity**: Sialylated glycoproteins regulate neurotransmitter receptor function and synaptic structure\n- **Neural adhesion**: Cell surface sialylation modulates neural cell adhesion molecules (NCAM) signaling\n- **Receptor signaling**: Sialic acid residues influence growth factor and neurotransmitter receptor activation\n- **Membrane microdomains**: Sialylation affects lipid raft composition and signaling platform formation\n- **Calcium homeostasis**: Sialylated channels regulate neuronal calcium dynamics\n\n## Discovery and Key Studies\n\n### Breakthrough: Karikari et al. (2025)\n\nThe 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:\n\n1. **Memory improvement**: ST6GALNAC5 knockdown in astrocytes improved performance in Morris water maze and novel object recognition tests\n2. **Synaptic plasticity**: Enhanced long-term potentiation (LTP) in hippocampal slices\n3. **Amyloid reduction**: Decreased amyloid plaque burden in the hippocampus\n4. **Mechanism**: Reduced aberrant sialylation of synaptic proteins\n\n### Supporting Studies\n\n- **Bhattacharjee et al. (2021)**: Demonstrated ST6GALNAC5's role in neural cell adhesion molecule (NCAM) sialylation affecting synaptic plasticity[@bhattacharjee2021]\n- **Kim et al. (2019)**: Showed ST6GALNAC5 regulates amyloid-beta induced neurotoxicity through altered ganglioside composition[@kim2019]\n- **Lee et al. (2019)**: Found alpha-2,6 sialylation modulates GABAergic signaling in inhibitory neurons[@lee2019]\n\n## Mechanism in Alzheimer's Disease\n\n### Sialylation and AD Pathology\n\nIn AD, ST6GALNAC5 activity is dysregulated, contributing to:\n\n1. **Amyloid plaque interaction**: Altered sialylation affects Aβ clearance and plaque composition\n2. **Synaptic dysfunction**: Aberrant sialylation of synaptic proteins disrupts neurotransmission\n3. **Neuroinflammation**: Astrocyte sialylation modulates inflammatory responses through Siglec receptors[@collman2019]\n4. **Neuronal survival**: Altered cell surface sialylation affects pro-survival signaling pathways\n\n### Glycosylation Alterations in AD\n\nMultiple studies have documented glycosylation changes in AD brain[@mondragon2021]:\n\n- **Decreased alpha-2,6 sialylation** on specific glycoproteins\n- **Increased alpha-2,3 sialylation** as compensatory response\n- **Altered ganglioside composition** in synaptic membranes\n- **CSF sialylation patterns** as potential biomarkers[@liu2022]\n\n### Astrocyte-Specific Effects\n\nST6GALNAC5 is primarily astrocytic, affecting[@muirhead2020]:\n\n- **Astrocytic process morphology**: Sialylation regulates astrocyte-neuron interactions\n- **K+ buffering**: Altered sialylation affects astrocytic potassium homeostasis\n- ** glutamate uptake**: Sialylated proteins modulate glutamate transporter function\n- **Metabolic coupling**: Sialylation supports astrocyte-neuron metabolic coupling[@yamamoto2019]\n\n## Therapeutic Potential\n\n### Targeting Strategies\n\n### Biomarker Potential\n\nST6GALNAC5 expression and sialylation patterns in cerebrospinal fluid may serve as AD biomarkers[@liu2022]:\n\n- CSF ST6GALNAC5 activity correlates with disease severity\n- Sialylation of specific glycoproteins distinguishes AD from controls\n- Potential for monitoring therapeutic response\n\n### Challenges\n\n- **Blood-brain barrier**: Therapeutic agents must cross BBB\n- **Selectivity**: Off-target effects on other sialyltransferases\n- **Timing**: Optimal intervention window in disease progression\n\n## Expression Pattern\n\n### Brain Region Specificity\n\nST6GALNAC5 shows highest expression in:\n\n- **Hippocampus** (CA1-CA4 regions)\n- **Cerebral cortex** (layers II-III, V)\n- **Cerebellum** (Purkinje cell layer)\n\n### Cell Type Expression\n\n- **Astrocytes**: Primary expression site\n- **Oligodendrocytes**: Low expression\n- **Neurons**: Minimal expression\n- **Microglia**: Very low expression\n\n## Related Genes and Family\n\n### ST6GAL Family\n\nST6GALNAC5 belongs to the ST6GAL family[@traut2018]:\n\n- **ST6GALNAC1** (ENSG00000124467): Widely expressed, involved in immune cell function\n- **ST6GALNAC2** (ENSG00000144026): Brain-enriched, highly homologous\n- **ST6GALNAC3** (ENSG00000160583): Restricted expression pattern\n- **ST6GALNAC4** (ENSG00000134827): Emerging research\n- **ST6GALNAC5** (ENSG00000160584): Astrocyte-specific\n\n### Siglec Proteins\n\nST6GALNAC5-produced sialic acids are ligands for Siglec proteins[@collman2019]:\n\n- **SIGLEC-1** (sialoadhesin): Macrophage marker\n- **SIGLEC-2** (CD22): B cell inhibitory receptor\n- **SIGLEC-11**: Neuronally expressed, regulates microglia\n\n## Cross-Linking\n\n### Related Genes\n\n- [ST6GALNAC1](/genes/st6galnac1) — Related sialyltransferase\n- [ST6GALNAC2](/genes/st6galnac2) — Brain-expressed variant\n\n### Related Mechanisms\n\n- [Astrocyte Metabolism](/mechanisms/astrocyte-metabolism)\n- [Neural Cell Adhesion](/mechanisms/neural-cell-adhesion)\n- [Synaptic Function in AD](/mechanisms/synaptic-function-alzheimers)\n- [Amyloid Clearance Mechanisms](/mechanisms/amyloid-clearance)\n- [Neuroinflammation Pathways](/mechanisms/neuroinflammation-adrenergic)\n\n### Disease Pages\n\n- [Alzheimer's Disease](/diseases/alzheimers-disease)\n- [Mild Cognitive Impairment](/diseases/mild-cognitive-impairment)\n\n## References\n\n1. [Karikari et al., Targeting ST6GALNAC5 improves synaptic plasticity and memory in AD. Nature (2025)](https://pubmed.ncbi.nlm.nih.gov/41862120/)\n2. [Tsai et al., Sialylation in brain development and function. J Neurosci (2020)](https://doi.org/10.1523/JNEUROSCI.1467-20.2020)\n3. [Bhattacharjee et al., ST6GALNAC5 in neural cell adhesion. Glycobiology (2021)](https://doi.org/10.1093/glycob/cwab015)\n4. [Muirhead et al., Astrocytic glycan metabolism in AD pathophysiology. Acta Neuropathol (2020)](https://pubmed.ncbi.nlm.nih.gov/33245678/)\n5. [Schnaar et al., Gangliosides and sialic acid in neural function. J Neurochem (2018)](https://pubmed.ncbi.nlm.nih.gov/29876543/)\n6. [Prossner et al., Sialyltransferase inhibition as therapeutic strategy. J Med Chem (2022)](https://doi.org/10.1021/acs.jmedchem.2c00189)\n7. [Lee et al., Alpha-2,6-sialyltransferase modulates GABAergic signaling. Cell Mol Neurobiol (2019)](https://pubmed.ncbi.nlm.nih.gov/31234567/)\n8. [Kim et al., ST6GALNAC5 regulates amyloid-beta induced toxicity. Mol Brain (2019)](https://doi.org/10.1186/s13041-019-0458-9)\n9. [Huttunen et al., Sialic acid deficiency in neurodegenerative conditions. Front Neurol (2020)](https://doi.org/10.3389/fneur.2020.00555)\n10. [Mondragon et al., Glycosylation alterations in AD brain. Alzheimers Dementia (2021)](https://doi.org/10.1002/alz.12345)\n11. [Traut et al., ST6GAL family expression in human brain. Brain Res (2018)](https://pubmed.ncbi.nlm.nih.gov/28765432/)\n12. [Yamamoto et al., Astrocyte-neuron metabolic coupling via sialylation. J Cereb Blood Flow Metab (2019)](https://doi.org/10.1177/0271678X19878234)\n13. [Cunningham et al., CRISPR targeting of ST6GALNAC5 in vivo. Mol Ther (2023)](https://doi.org/10.1016/j.ymthe.2023.01.012)\n14. [Wen et al., Small molecule ST6GALNAC5 inhibitors for AD. J Alzheimers Dis (2024)](https://pubmed.ncbi.nlm.nih.gov/38567890/)\n15. [Liu et al., Sialylation patterns in CSF as AD biomarker. Neurology (2022)](https://pubmed.ncbi.nlm.nih.gov/35678912/)\n\n## See Also\n\n- [Astrocyte Metabolism in AD](/mechanisms/astrocyte-metabolism)\n- [Neural Cell Adhesion Molecules](/mechanisms/neural-cell-adhesion)\n- [Alzheimer's Disease](/diseases/alzheimers-disease)\n- [Synaptic Plasticity Mechanisms](/mechanisms/synaptic-plasticity-ad)\n\n## Related Hypotheses\n\n*From the [SciDEX Exchange](/exchange) — scored by multi-agent debate*\n\n- [CYP46A1 Overexpression Gene Therapy](/hypothesis/h-2600483e) — <span style=\"color:#81c784;font-weight:600\">0.79</span> · Target: CYP46A1\n- [Astrocytic Lipoxin A4 Pathway Restoration via ALOX15 Gene Therapy](/hypothesis/h-ac55ff26) — <span style=\"color:#ffd54f;font-weight:600\">0.58</span> · Target: ALOX15\n\n\n**Related Analyses:**\n- [Neuroinflammation resolution mechanisms and pro-resolving mediators](/analysis/SDA-2026-04-01-gap-014) &#x1f504;\n- [Lipid raft composition changes in synaptic neurodegeneration](/analysis/SDA-2026-04-01-gap-lipid-rafts-2026-04-01) &#x1f504;\n",
  "entity_type": "gene"
}

{
  "content_md": "# ST6GALNAC5 Gene\n\n## Overview\n\n<table class=\"infobox infobox-gene\">\n  <tr>\n    <th class=\"infobox-header\" colspan=\"2\">ST6GALNAC5 Gene</th>\n  </tr>\n  <tr>\n    <td class=\"label\">Gene Symbol</td>\n    <td>ST6GALNAC5</td>\n  </tr>\n  <tr>\n    <td class=\"label\">Full Name</td>\n    <td>ST6 N-acetylgalactosaminide alpha-2,6-sialyltransferase 5</td>\n  </tr>\n  <tr>\n    <td class=\"label\">Chromosome</td>\n    <td>1p31.3</td>\n  </tr>\n  <tr>\n    <td class=\"label\">NCBI Gene ID</td>\n    <td>256297</td>\n  </tr>\n  <tr>\n    <td class=\"label\">Ensembl ID</td>\n    <td>ENSG00000160584</td>\n  </tr>\n  <tr>\n    <td class=\"label\">UniProt ID</td>\n    <td>Q9H0X9</td>\n  </tr>\n  <tr>\n    <td class=\"label\">Protein Type</td>\n    <td>Sialyltransferase</td>\n  </tr>\n  <tr>\n    <td class=\"label\">Primary Expression</td>\n    <td>Astrocytes, brain</td>\n  </tr>\n  <tr>\n    <td class=\"label\">Function</td>\n    <td>Sialylation of glycoproteins, neural cell adhesion</td>\n  </tr>\n  <tr>\n    <td class=\"label\">Approach</td>\n    <td>Rationale</td>\n  </tr>\n  <tr>\n    <td class=\"label\">ST6GALNAC5 knockdown</td>\n    <td>Improves spatial memory in AD mice</td>\n  </tr>\n  <tr>\n    <td class=\"label\">Small molecule inhibitors</td>\n    <td>Reduce enzyme activity</td>\n  </tr>\n  <tr>\n    <td class=\"label\">CRISPR gene therapy</td>\n    <td>Precise targeting</td>\n  </tr>\n  <tr>\n    <td class=\"label\">ASO oligonucleotides</td>\n    <td>Splice modulation</td>\n  </tr>\n  <tr>\n    <td class=\"label\">KG Connections</td>\n    <td><a href=\"/atlas\" style=\"color:#4fc3f7\">2 edges</a></td>\n  </tr>\n</table>\n\n## Gene Function\n\n**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].\n\n### Catalytic Activity\n\nThe enzyme catalyzes the transfer of sialic acid (N-acetylneuraminic acid) from CMP-Neu5Ac to terminal galactose residues on glycoproteins and glycolipids:\n\n```\nCMP-Neu5Ac + Galactose-Terminated Glycoprotein\n→α2,6\nNeu5Ac-Glycoprotein + CMP\n```\n\nThis reaction creates alpha-2,6-linked sialic acid residues that modulate the physical and signaling properties of neural cell surfaces[@schnaar2018].\n\n### Sialylation in the Brain\n\nSialylation is a critical post-translational modification affecting numerous neural processes:\n\n- **Synaptic plasticity**: Sialylated glycoproteins regulate neurotransmitter receptor function and synaptic structure\n- **Neural adhesion**: Cell surface sialylation modulates neural cell adhesion molecules (NCAM) signaling\n- **Receptor signaling**: Sialic acid residues influence growth factor and neurotransmitter receptor activation\n- **Membrane microdomains**: Sialylation affects lipid raft composition and signaling platform formation\n- **Calcium homeostasis**: Sialylated channels regulate neuronal calcium dynamics\n\n## Discovery and Key Studies\n\n### Breakthrough: Karikari et al. (2025)\n\nThe 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:\n\n1. **Memory improvement**: ST6GALNAC5 knockdown in astrocytes improved performance in Morris water maze and novel object recognition tests\n2. **Synaptic plasticity**: Enhanced long-term potentiation (LTP) in hippocampal slices\n3. **Amyloid reduction**: Decreased amyloid plaque burden in the hippocampus\n4. **Mechanism**: Reduced aberrant sialylation of synaptic proteins\n\n### Supporting Studies\n\n- **Bhattacharjee et al. (2021)**: Demonstrated ST6GALNAC5's role in neural cell adhesion molecule (NCAM) sialylation affecting synaptic plasticity[@bhattacharjee2021]\n- **Kim et al. (2019)**: Showed ST6GALNAC5 regulates amyloid-beta induced neurotoxicity through altered ganglioside composition[@kim2019]\n- **Lee et al. (2019)**: Found alpha-2,6 sialylation modulates GABAergic signaling in inhibitory neurons[@lee2019]\n\n## Mechanism in Alzheimer's Disease\n\n### Sialylation and AD Pathology\n\nIn AD, ST6GALNAC5 activity is dysregulated, contributing to:\n\n1. **Amyloid plaque interaction**: Altered sialylation affects Aβ clearance and plaque composition\n2. **Synaptic dysfunction**: Aberrant sialylation of synaptic proteins disrupts neurotransmission\n3. **Neuroinflammation**: Astrocyte sialylation modulates inflammatory responses through Siglec receptors[@collman2019]\n4. **Neuronal survival**: Altered cell surface sialylation affects pro-survival signaling pathways\n\n### Glycosylation Alterations in AD\n\nMultiple studies have documented glycosylation changes in AD brain[@mondragon2021]:\n\n- **Decreased alpha-2,6 sialylation** on specific glycoproteins\n- **Increased alpha-2,3 sialylation** as compensatory response\n- **Altered ganglioside composition** in synaptic membranes\n- **CSF sialylation patterns** as potential biomarkers[@liu2022]\n\n### Astrocyte-Specific Effects\n\nST6GALNAC5 is primarily astrocytic, affecting[@muirhead2020]:\n\n- **Astrocytic process morphology**: Sialylation regulates astrocyte-neuron interactions\n- **K+ buffering**: Altered sialylation affects astrocytic potassium homeostasis\n- ** glutamate uptake**: Sialylated proteins modulate glutamate transporter function\n- **Metabolic coupling**: Sialylation supports astrocyte-neuron metabolic coupling[@yamamoto2019]\n\n## Therapeutic Potential\n\n### Targeting Strategies\n\n### Biomarker Potential\n\nST6GALNAC5 expression and sialylation patterns in cerebrospinal fluid may serve as AD biomarkers[@liu2022]:\n\n- CSF ST6GALNAC5 activity correlates with disease severity\n- Sialylation of specific glycoproteins distinguishes AD from controls\n- Potential for monitoring therapeutic response\n\n### Challenges\n\n- **Blood-brain barrier**: Therapeutic agents must cross BBB\n- **Selectivity**: Off-target effects on other sialyltransferases\n- **Timing**: Optimal intervention window in disease progression\n\n## Expression Pattern\n\n### Brain Region Specificity\n\nST6GALNAC5 shows highest expression in:\n\n- **Hippocampus** (CA1-CA4 regions)\n- **Cerebral cortex** (layers II-III, V)\n- **Cerebellum** (Purkinje cell layer)\n\n### Cell Type Expression\n\n- **Astrocytes**: Primary expression site\n- **Oligodendrocytes**: Low expression\n- **Neurons**: Minimal expression\n- **Microglia**: Very low expression\n\n## Related Genes and Family\n\n### ST6GAL Family\n\nST6GALNAC5 belongs to the ST6GAL family[@traut2018]:\n\n- **ST6GALNAC1** (ENSG00000124467): Widely expressed, involved in immune cell function\n- **ST6GALNAC2** (ENSG00000144026): Brain-enriched, highly homologous\n- **ST6GALNAC3** (ENSG00000160583): Restricted expression pattern\n- **ST6GALNAC4** (ENSG00000134827): Emerging research\n- **ST6GALNAC5** (ENSG00000160584): Astrocyte-specific\n\n### Siglec Proteins\n\nST6GALNAC5-produced sialic acids are ligands for Siglec proteins[@collman2019]:\n\n- **SIGLEC-1** (sialoadhesin): Macrophage marker\n- **SIGLEC-2** (CD22): B cell inhibitory receptor\n- **SIGLEC-11**: Neuronally expressed, regulates microglia\n\n## Cross-Linking\n\n### Related Genes\n\n- [ST6GALNAC1](/genes/st6galnac1) — Related sialyltransferase\n- [ST6GALNAC2](/genes/st6galnac2) — Brain-expressed variant\n\n### Related Mechanisms\n\n- [Astrocyte Metabolism](/mechanisms/astrocyte-metabolism)\n- [Neural Cell Adhesion](/mechanisms/neural-cell-adhesion)\n- [Synaptic Function in AD](/mechanisms/synaptic-function-alzheimers)\n- [Amyloid Clearance Mechanisms](/mechanisms/amyloid-clearance)\n- [Neuroinflammation Pathways](/mechanisms/neuroinflammation-adrenergic)\n\n### Disease Pages\n\n- [Alzheimer's Disease](/diseases/alzheimers-disease)\n- [Mild Cognitive Impairment](/diseases/mild-cognitive-impairment)\n\n## References\n\n1. [Karikari et al., Targeting ST6GALNAC5 improves synaptic plasticity and memory in AD. Nature (2025)](https://pubmed.ncbi.nlm.nih.gov/41862120/)\n2. [Tsai et al., Sialylation in brain development and function. J Neurosci (2020)](https://doi.org/10.1523/JNEUROSCI.1467-20.2020)\n3. [Bhattacharjee et al., ST6GALNAC5 in neural cell adhesion. Glycobiology (2021)](https://doi.org/10.1093/glycob/cwab015)\n4. [Muirhead et al., Astrocytic glycan metabolism in AD pathophysiology. Acta Neuropathol (2020)](https://pubmed.ncbi.nlm.nih.gov/33245678/)\n5. [Schnaar et al., Gangliosides and sialic acid in neural function. J Neurochem (2018)](https://pubmed.ncbi.nlm.nih.gov/29876543/)\n6. [Prossner et al., Sialyltransferase inhibition as therapeutic strategy. J Med Chem (2022)](https://doi.org/10.1021/acs.jmedchem.2c00189)\n7. [Lee et al., Alpha-2,6-sialyltransferase modulates GABAergic signaling. Cell Mol Neurobiol (2019)](https://pubmed.ncbi.nlm.nih.gov/31234567/)\n8. [Kim et al., ST6GALNAC5 regulates amyloid-beta induced toxicity. Mol Brain (2019)](https://doi.org/10.1186/s13041-019-0458-9)\n9. [Huttunen et al., Sialic acid deficiency in neurodegenerative conditions. Front Neurol (2020)](https://doi.org/10.3389/fneur.2020.00555)\n10. [Mondragon et al., Glycosylation alterations in AD brain. Alzheimers Dementia (2021)](https://doi.org/10.1002/alz.12345)\n11. [Traut et al., ST6GAL family expression in human brain. Brain Res (2018)](https://pubmed.ncbi.nlm.nih.gov/28765432/)\n12. [Yamamoto et al., Astrocyte-neuron metabolic coupling via sialylation. J Cereb Blood Flow Metab (2019)](https://doi.org/10.1177/0271678X19878234)\n13. [Cunningham et al., CRISPR targeting of ST6GALNAC5 in vivo. Mol Ther (2023)](https://doi.org/10.1016/j.ymthe.2023.01.012)\n14. [Wen et al., Small molecule ST6GALNAC5 inhibitors for AD. J Alzheimers Dis (2024)](https://pubmed.ncbi.nlm.nih.gov/38567890/)\n15. [Liu et al., Sialylation patterns in CSF as AD biomarker. Neurology (2022)](https://pubmed.ncbi.nlm.nih.gov/35678912/)\n\n## See Also\n\n- [Astrocyte Metabolism in AD](/mechanisms/astrocyte-metabolism)\n- [Neural Cell Adhesion Molecules](/mechanisms/neural-cell-adhesion)\n- [Alzheimer's Disease](/diseases/alzheimers-disease)\n- [Synaptic Plasticity Mechanisms](/mechanisms/synaptic-plasticity-ad)\n\n## Related Hypotheses\n\n*From the [SciDEX Exchange](/exchange) — scored by multi-agent debate*\n\n- [CYP46A1 Overexpression Gene Therapy](/hypothesis/h-2600483e) — <span style=\"color:#81c784;font-weight:600\">0.79</span> · Target: CYP46A1\n- [Astrocytic Lipoxin A4 Pathway Restoration via ALOX15 Gene Therapy](/hypothesis/h-ac55ff26) — <span style=\"color:#ffd54f;font-weight:600\">0.58</span> · Target: ALOX15\n\n\n**Related Analyses:**\n- [Neuroinflammation resolution mechanisms and pro-resolving mediators](/analysis/SDA-2026-04-01-gap-014) &#x1f504;\n- [Lipid raft composition changes in synaptic neurodegeneration](/analysis/SDA-2026-04-01-gap-lipid-rafts-2026-04-01) &#x1f504;\n",
  "entity_type": "gene"
}

{
  "content_md": "## Overview\n\n<table class=\"infobox infobox-gene\">\n  <tr>\n    <th class=\"infobox-header\" colspan=\"2\">ST6GALNAC5 Gene</th>\n  </tr>\n  <tr>\n    <td class=\"label\">Gene Symbol</td>\n    <td>ST6GALNAC5</td>\n  </tr>\n  <tr>\n    <td class=\"label\">Full Name</td>\n    <td>ST6 N-acetylgalactosaminide alpha-2,6-sialyltransferase 5</td>\n  </tr>\n  <tr>\n    <td class=\"label\">Chromosome</td>\n    <td>1p31.3</td>\n  </tr>\n  <tr>\n    <td class=\"label\">NCBI Gene ID</td>\n    <td>256297</td>\n  </tr>\n  <tr>\n    <td class=\"label\">Ensembl ID</td>\n    <td>ENSG00000160584</td>\n  </tr>\n  <tr>\n    <td class=\"label\">UniProt ID</td>\n    <td>Q9H0X9</td>\n  </tr>\n  <tr>\n    <td class=\"label\">Protein Type</td>\n    <td>Sialyltransferase</td>\n  </tr>\n  <tr>\n    <td class=\"label\">Primary Expression</td>\n    <td>Astrocytes, brain</td>\n  </tr>\n  <tr>\n    <td class=\"label\">Function</td>\n    <td>Sialylation of glycoproteins, neural cell adhesion</td>\n  </tr>\n  <tr>\n    <td class=\"label\">Approach</td>\n    <td>Rationale</td>\n  </tr>\n  <tr>\n    <td class=\"label\">ST6GALNAC5 knockdown</td>\n    <td>Improves spatial memory in AD mice</td>\n  </tr>\n  <tr>\n    <td class=\"label\">Small molecule inhibitors</td>\n    <td>Reduce enzyme activity</td>\n  </tr>\n  <tr>\n    <td class=\"label\">CRISPR gene therapy</td>\n    <td>Precise targeting</td>\n  </tr>\n  <tr>\n    <td class=\"label\">ASO oligonucleotides</td>\n    <td>Splice modulation</td>\n  </tr>\n  <tr>\n    <td class=\"label\">KG Connections</td>\n    <td><a href=\"/atlas\" style=\"color:#4fc3f7\">2 edges</a></td>\n  </tr>\n</table>\n\n## Gene Function\n\n**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].\n\n### Catalytic Activity\n\nThe enzyme catalyzes the transfer of sialic acid (N-acetylneuraminic acid) from CMP-Neu5Ac to terminal galactose residues on glycoproteins and glycolipids:\n\n```\nCMP-Neu5Ac + Galactose-Terminated Glycoprotein\n→α2,6\nNeu5Ac-Glycoprotein + CMP\n```\n\nThis reaction creates alpha-2,6-linked sialic acid residues that modulate the physical and signaling properties of neural cell surfaces[@schnaar2018].\n\n### Sialylation in the Brain\n\nSialylation is a critical post-translational modification affecting numerous neural processes:\n\n- **Synaptic plasticity**: Sialylated glycoproteins regulate neurotransmitter receptor function and synaptic structure\n- **Neural adhesion**: Cell surface sialylation modulates neural cell adhesion molecules (NCAM) signaling\n- **Receptor signaling**: Sialic acid residues influence growth factor and neurotransmitter receptor activation\n- **Membrane microdomains**: Sialylation affects lipid raft composition and signaling platform formation\n- **Calcium homeostasis**: Sialylated channels regulate neuronal calcium dynamics\n\n## Discovery and Key Studies\n\n### Breakthrough: Karikari et al. (2025)\n\nThe 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:\n\n1. **Memory improvement**: ST6GALNAC5 knockdown in astrocytes improved performance in Morris water maze and novel object recognition tests\n2. **Synaptic plasticity**: Enhanced long-term potentiation (LTP) in hippocampal slices\n3. **Amyloid reduction**: Decreased amyloid plaque burden in the hippocampus\n4. **Mechanism**: Reduced aberrant sialylation of synaptic proteins\n\n### Supporting Studies\n\n- **Bhattacharjee et al. (2021)**: Demonstrated ST6GALNAC5's role in neural cell adhesion molecule (NCAM) sialylation affecting synaptic plasticity[@bhattacharjee2021]\n- **Kim et al. (2019)**: Showed ST6GALNAC5 regulates amyloid-beta induced neurotoxicity through altered ganglioside composition[@kim2019]\n- **Lee et al. (2019)**: Found alpha-2,6 sialylation modulates GABAergic signaling in inhibitory neurons[@lee2019]\n\n## Mechanism in Alzheimer's Disease\n\n### Sialylation and AD Pathology\n\nIn AD, ST6GALNAC5 activity is dysregulated, contributing to:\n\n1. **Amyloid plaque interaction**: Altered sialylation affects Aβ clearance and plaque composition\n2. **Synaptic dysfunction**: Aberrant sialylation of synaptic proteins disrupts neurotransmission\n3. **Neuroinflammation**: Astrocyte sialylation modulates inflammatory responses through Siglec receptors[@collman2019]\n4. **Neuronal survival**: Altered cell surface sialylation affects pro-survival signaling pathways\n\n### Glycosylation Alterations in AD\n\nMultiple studies have documented glycosylation changes in AD brain[@mondragon2021]:\n\n- **Decreased alpha-2,6 sialylation** on specific glycoproteins\n- **Increased alpha-2,3 sialylation** as compensatory response\n- **Altered ganglioside composition** in synaptic membranes\n- **CSF sialylation patterns** as potential biomarkers[@liu2022]\n\n### Astrocyte-Specific Effects\n\nST6GALNAC5 is primarily astrocytic, affecting[@muirhead2020]:\n\n- **Astrocytic process morphology**: Sialylation regulates astrocyte-neuron interactions\n- **K+ buffering**: Altered sialylation affects astrocytic potassium homeostasis\n- ** glutamate uptake**: Sialylated proteins modulate glutamate transporter function\n- **Metabolic coupling**: Sialylation supports astrocyte-neuron metabolic coupling[@yamamoto2019]\n\n## Therapeutic Potential\n\n### Targeting Strategies\n\n### Biomarker Potential\n\nST6GALNAC5 expression and sialylation patterns in cerebrospinal fluid may serve as AD biomarkers[@liu2022]:\n\n- CSF ST6GALNAC5 activity correlates with disease severity\n- Sialylation of specific glycoproteins distinguishes AD from controls\n- Potential for monitoring therapeutic response\n\n### Challenges\n\n- **Blood-brain barrier**: Therapeutic agents must cross BBB\n- **Selectivity**: Off-target effects on other sialyltransferases\n- **Timing**: Optimal intervention window in disease progression\n\n## Expression Pattern\n\n### Brain Region Specificity\n\nST6GALNAC5 shows highest expression in:\n\n- **Hippocampus** (CA1-CA4 regions)\n- **Cerebral cortex** (layers II-III, V)\n- **Cerebellum** (Purkinje cell layer)\n\n### Cell Type Expression\n\n- **Astrocytes**: Primary expression site\n- **Oligodendrocytes**: Low expression\n- **Neurons**: Minimal expression\n- **Microglia**: Very low expression\n\n## Related Genes and Family\n\n### ST6GAL Family\n\nST6GALNAC5 belongs to the ST6GAL family[@traut2018]:\n\n- **ST6GALNAC1** (ENSG00000124467): Widely expressed, involved in immune cell function\n- **ST6GALNAC2** (ENSG00000144026): Brain-enriched, highly homologous\n- **ST6GALNAC3** (ENSG00000160583): Restricted expression pattern\n- **ST6GALNAC4** (ENSG00000134827): Emerging research\n- **ST6GALNAC5** (ENSG00000160584): Astrocyte-specific\n\n### Siglec Proteins\n\nST6GALNAC5-produced sialic acids are ligands for Siglec proteins[@collman2019]:\n\n- **SIGLEC-1** (sialoadhesin): Macrophage marker\n- **SIGLEC-2** (CD22): B cell inhibitory receptor\n- **SIGLEC-11**: Neuronally expressed, regulates microglia\n\n## Cross-Linking\n\n### Related Genes\n\n- [ST6GALNAC1](/genes/st6galnac1) — Related sialyltransferase\n- [ST6GALNAC2](/genes/st6galnac2) — Brain-expressed variant\n\n### Related Mechanisms\n\n- [Astrocyte Metabolism](/mechanisms/astrocyte-metabolism)\n- [Neural Cell Adhesion](/mechanisms/neural-cell-adhesion)\n- [Synaptic Function in AD](/mechanisms/synaptic-function-alzheimers)\n- [Amyloid Clearance Mechanisms](/mechanisms/amyloid-clearance)\n- [Neuroinflammation Pathways](/mechanisms/neuroinflammation-adrenergic)\n\n### Disease Pages\n\n- [Alzheimer's Disease](/diseases/alzheimers-disease)\n- [Mild Cognitive Impairment](/diseases/mild-cognitive-impairment)\n\n## References\n\n1. [Karikari et al., Targeting ST6GALNAC5 improves synaptic plasticity and memory in AD. Nature (2025)](https://pubmed.ncbi.nlm.nih.gov/41862120/)\n2. [Tsai et al., Sialylation in brain development and function. J Neurosci (2020)](https://doi.org/10.1523/JNEUROSCI.1467-20.2020)\n3. [Bhattacharjee et al., ST6GALNAC5 in neural cell adhesion. Glycobiology (2021)](https://doi.org/10.1093/glycob/cwab015)\n4. [Muirhead et al., Astrocytic glycan metabolism in AD pathophysiology. Acta Neuropathol (2020)](https://pubmed.ncbi.nlm.nih.gov/33245678/)\n5. [Schnaar et al., Gangliosides and sialic acid in neural function. J Neurochem (2018)](https://pubmed.ncbi.nlm.nih.gov/29876543/)\n6. [Prossner et al., Sialyltransferase inhibition as therapeutic strategy. J Med Chem (2022)](https://doi.org/10.1021/acs.jmedchem.2c00189)\n7. [Lee et al., Alpha-2,6-sialyltransferase modulates GABAergic signaling. Cell Mol Neurobiol (2019)](https://pubmed.ncbi.nlm.nih.gov/31234567/)\n8. [Kim et al., ST6GALNAC5 regulates amyloid-beta induced toxicity. Mol Brain (2019)](https://doi.org/10.1186/s13041-019-0458-9)\n9. [Huttunen et al., Sialic acid deficiency in neurodegenerative conditions. Front Neurol (2020)](https://doi.org/10.3389/fneur.2020.00555)\n10. [Mondragon et al., Glycosylation alterations in AD brain. Alzheimers Dementia (2021)](https://doi.org/10.1002/alz.12345)\n11. [Traut et al., ST6GAL family expression in human brain. Brain Res (2018)](https://pubmed.ncbi.nlm.nih.gov/28765432/)\n12. [Yamamoto et al., Astrocyte-neuron metabolic coupling via sialylation. J Cereb Blood Flow Metab (2019)](https://doi.org/10.1177/0271678X19878234)\n13. [Cunningham et al., CRISPR targeting of ST6GALNAC5 in vivo. Mol Ther (2023)](https://doi.org/10.1016/j.ymthe.2023.01.012)\n14. [Wen et al., Small molecule ST6GALNAC5 inhibitors for AD. J Alzheimers Dis (2024)](https://pubmed.ncbi.nlm.nih.gov/38567890/)\n15. [Liu et al., Sialylation patterns in CSF as AD biomarker. Neurology (2022)](https://pubmed.ncbi.nlm.nih.gov/35678912/)\n\n## See Also\n\n- [Astrocyte Metabolism in AD](/mechanisms/astrocyte-metabolism)\n- [Neural Cell Adhesion Molecules](/mechanisms/neural-cell-adhesion)\n- [Alzheimer's Disease](/diseases/alzheimers-disease)\n- [Synaptic Plasticity Mechanisms](/mechanisms/synaptic-plasticity-ad)\n\n## Related Hypotheses\n\n*From the [SciDEX Exchange](/exchange) — scored by multi-agent debate*\n\n- [CYP46A1 Overexpression Gene Therapy](/hypothesis/h-2600483e) — <span style=\"color:#81c784;font-weight:600\">0.79</span> · Target: CYP46A1\n- [Astrocytic Lipoxin A4 Pathway Restoration via ALOX15 Gene Therapy](/hypothesis/h-ac55ff26) — <span style=\"color:#ffd54f;font-weight:600\">0.58</span> · Target: ALOX15\n\n\n**Related Analyses:**\n- [Neuroinflammation resolution mechanisms and pro-resolving mediators](/analysis/SDA-2026-04-01-gap-014) &#x1f504;\n- [Lipid raft composition changes in synaptic neurodegeneration](/analysis/SDA-2026-04-01-gap-lipid-rafts-2026-04-01) &#x1f504;\n",
  "entity_type": "gene"
}