St6galnac5 is a protein. This page describes its structure, normal nervous system function, role in neurodegenerative disease, and potential as a therapeutic target.
| Property | Value |
|---|---|
| Gene Name | ST6GALNAC5 |
| Full Name | ST6 N-acetylneuraminic acid alpha-2,6-sialyltransferase 5 |
| Chromosomal Location | Chromosome 9 |
| Protein Class | Sialyltransferase |
| Aliases | SIAT7B, ST6GalNAcV |
St6galnac5 (also known as SIAT7B or ST6GalNAcV) encodes a sialyltransferase enzyme that catalyzes the transfer of sialic acid (N-acetylneuraminic acid) to glycoproteins and glycolipids via an alpha-2,6 linkage. This enzyme is a member of the glycosyltransferase family and plays a critical role in protein sialylation, a fundamental post-translational modification that affects protein folding, stability, cell-cell interactions, and receptor signaling.
St6galnac5 belongs to the ST6 N-acetylneuraminic acid alpha-2,6-sialyltransferase family. The enzyme catalyzes the following reaction:
GDP-N-acetylneuraminic acid + glycoprotein → N-acetylneuraminic acid α2-6-glycoprotein + GDP
This reaction adds sialic acid residues to the terminal positions of glycoconjugates, a process known as protein sialylation. Sialylation is one of the most abundant and biologically significant post-translational modifications, affecting:
In the brain, St6galnac5 is predominantly expressed in astrocytes, where it plays a specialized role in regulating astrocyte-neuron interactions. The enzyme is localized to the Golgi apparatus where it sialylates target proteins destined for secretion or membrane presentation.
Recent research has identified St6galnac5 as a critical molecular switch driving astrocytic dysfunction in Alzheimer's disease. Using single-nucleus transcriptomic analysis of human AD brain tissue and the 3xTg-AD mouse model, studies have demonstrated that:
| Astrocyte Marker | Effect of St6galnac5 Knockdown |
|---|---|
| A1 markers (C3, Serping1, etc.) | Decreased |
| A2 markers (S100a10, Ptx3, etc.) | Increased |
| Neurotoxicity | Reduced |
Knockdown of St6galnac5 in astrocytes:
One of the most significant findings is that St6galnac5 knockdown preserves synaptic integrity in AD models. In the 3xTg-AD mouse model:
Remarkably, St6galnac5 knockdown leads to a marked reduction in both amyloid-β and tau pathologies:
This suggests that astrocyte St6galnac5 plays a role in modulating the processing or clearance of both key AD pathological proteins.
In female 3xTg-AD mice, AAV-mediated knockdown of St6galnac5 resulted in:
The findings from recent research suggest that targeted inhibition of the St6galnac5 sialylation pathway represents a viable strategy to bolster astrocytic resilience and slow disease progression. Several therapeutic approaches are being considered:
St6galnac5 is an astrocyte-expressed sialyltransferase that has emerged as a novel therapeutic target in Alzheimer's disease. By functioning as a molecular switch driving astrocytic dysfunction, St6galnac5 promotes the neurotoxic A1 astrocyte phenotype, contributes to neuroinflammation, and exacerbates both amyloid-β and tau pathologies. Remarkably, knockdown of St6galnac5 not only shifts astrocytes toward a protective A2 phenotype but also reduces amyloid and tau pathology while preserving synaptic integrity and improving cognitive function. This makes St6galnac5 one of the most promising new targets for disease-modifying therapy in AD.