| UniProt ID | [Q99971](https://www.uniprot.org/uniprotkb/Q99971) |
| Gene | [SDC3](/genes/sdc3) |
| MW | ~44 kDa (core) |
| Location | Neuronal cell surface, synaptic membranes |
| Structure | HSPG with heparan sulfate chains |
Syndecan-3 Protein is a protein that in the healthy brain, syndecan-3 has several important functions:[1]. This page describes its structure, normal nervous system function, role in neurodegenerative disease, and potential as a therapeutic target.
Syndecan-3 (SDC3, also known as Neuroglycan C or N-syndecan) is a neuronal heparan sulfate proteoglycan (HSPG) that serves as a critical mediator of pathological protein binding, spreading, and neurodegeneration. As the largest member of the syndecan family, it plays essential roles in both normal neuronal function and disease pathology.[2]
Syndecan-3 is a type I transmembrane proteoglycan with distinct domains:[3]
The extracellular domain carries multiple heparan sulfate chains that confer binding capacity for diverse ligands including growth factors, extracellular matrix components, and pathological proteins.
In the healthy brain, Syndecan-3 has several important functions:[1:1]
The heparan sulfate chains on Syndecan-3 enable binding to diverse ligands through electrostatic interactions with negatively charged sulfate groups:[4]
Syndecan-3 has emerged as a key mediator of tau propagation in Alzheimer's disease and related tauopathies:[5]
The binding is primarily mediated by the heparan sulfate chains, which interact with basic residues in the tau microtubule-binding domain. Removal of heparan sulfate chains by heparinase treatment dramatically reduces tau uptake.
Syndecan-3 also contributes to alpha-synuclein pathology in Parkinson's disease:[6]
In Alzheimer's disease, Syndecan-3 influences amyloid-β pathology:[7]
Targeting Syndecan-3-heparan sulfate interactions represents a potential therapeutic strategy:
| Approach | Mechanism | Status |
|---|---|---|
| Heparin mimetics | Compete for fibril binding | Preclinical |
| Heparanase treatment | Remove HS chains | Research tool |
| Antibodies against SDC3 | Block receptor function | Early research |
| Small molecule inhibitors | Disrupt HS-protein interaction | Conceptual |
| Interacting Partner | Type | Function |
|---|---|---|
| Tau fibrils | Pathological | Disease spreading |
| Alpha-synuclein fibrils | Pathological | Disease spreading |
| BDNF | Physiological | Synaptic plasticity |
| Pleiotrophin | Physiological | Neurite outgrowth |
| FGF family | Physiological | Neurotrophic support |
Reizes O, et al. Transgenic expression of syndecan-3 in neurons affects feeding behavior and body weight. J Neurosci. 2008;28(43):10982-10991. doi:. 10.1523/JNEUROSCI.2966-08.2008. 2008. ↩︎ ↩︎
Carey DJ, et al. Syndecan-3 (N-syndecan) is a neuronal heparan sulfate proteoglycan. J Biol Chem. 1997;272(10):6521-6527. doi:. 10.1074/jbc.272.10.6521. 1997. ↩︎
Bass MD, et al. Cytoplasmic domain interactions of syndecan-3 and syndecan-4. J Biol Chem. 2007;282(42):30703-30713. doi:. 10.1074/jbc.M703489200. 2007. ↩︎
Bishop JR, et al. Heparan sulphate proteoglycans fine-tune mammalian physiology. Nature. 2007;446(7139):1030-1037. doi:. 10.1038/nature05817. 2007. ↩︎
Holmes BB, et al. Heparan sulfate proteoglycans mediate internalization and propagation of specific proteopathic seeds. Proc Natl Acad Sci USA. 2013;110(33):E3138-3147. doi:. 10.1073/pnas.1301440110. 2013. ↩︎
Ihse E, et al. Cellular internalization of alpha-synuclein aggregates is facilitated by heparan sulfate proteoglycans. Acta Neuropathol. 2017;134(4):625-626. doi:. 10.1007/s00401-017-1746-6. 2017. ↩︎
Sandwall E, et al. Heparan sulfate mediates amyloid-beta internalization and cytotoxicity. Glycobiology. 2010;20(5):533-540. doi:. 10.1093/glycob/cwp201. 2010. ↩︎