Glycosaminoglycans (GAGs) are complex carbohydrate chains attached to core proteins, forming proteoglycans that are essential components of the extracellular matrix and cell surfaces in the brain. These molecules play critical roles in neuronal development, synaptic function, and cellular homeostasis. Dysregulation of glycosaminoglycan metabolism—particularly heparan sulfate (HS) and chondroitin sulfate (CS)—is increasingly recognized as a significant contributor to neurodegenerative disease pathogenesis through effects on protein aggregation, neuroinflammation, and impaired cellular clearance mechanisms[1].
HSPGs are expressed throughout the brain and serve multiple essential functions:
CSPGs are particularly abundant in the perineuronal nets that surround neurons:
Heparan sulfate proteoglycans colocalize extensively with amyloid plaques in AD brain[2]. The interaction between HSPGs and amyloid-beta (Aβ) has several important consequences:
Beyond Aβ, heparan sulfate also modulates tau protein aggregation and spread:
Several therapeutic strategies targeting GAGs are being explored for AD:
| Approach | Mechanism | Status |
|---|---|---|
| Heparan sulfate mimetics | Block Aβ-HS interaction | Preclinical[3] |
| Sulfation pattern modulation | Alter GAG function | Research |
| Perineuronal net degradation | Enhance plasticity | Research |
| Enzyme-based approaches | Modify HS structure | Preclinical |
Heparan sulfate plays a significant role in alpha-synuclein pathology in Parkinson's disease[4][5]:
Sanfilippo syndrome represents a direct genetic link between GAG metabolism and neurodegeneration[6]:
| Protein/Enzyme | Function | Neurodegeneration Role |
|---|---|---|
| NAGLU | α-N-acetylglucosaminidase | MPS IIIB (Sanfilippo B) |
| SGSH | N-sulfoglucosamine sulfohydrolase | MPS IIIA |
| HGSNAT | Heparan-α-glucosaminide N-acetyltransferase | MPS IIIC |
| GNS | N-acetylglucosamine-6-sulfatase | MPS IIID |
| Heparan sulfate | Proteoglycan component | Binds Aβ and α-syn, affects clearance |
| CSPG | Proteoglycan component | Perineuronal nets, glial scars |
| AGRIN | HSPG in synaptic structures | Synapse formation and maintenance |
| PERLECAN | HSPG in basement membrane | BBB function, vascular amyloid |
Recombinant enzymes for mucopolysaccharidoses:
| Treatment | Target | Status | Indication |
|---|---|---|---|
| Laronidase | α-L-iduronidase | Approved | MPS I |
| Idursulfase | Iduronate-2-sulfatase | Approved | MPS II |
| Vestronidase | β-glucuronidase | Approved | MPS VII |
| Gene therapy | NAGLU | Phase 1/2 | MPS IIIB |
Zhang L, et al. "Glycosaminoglycans in neurodegeneration: mechanisms and therapeutic potential". Cellular and Molecular Life Sciences. 2022. ↩︎
Snow AD, et al. "Heparan sulfate proteoglycans in the extracellular matrix of Alzheimer's disease brain". American Journal of Pathology. 1990. ↩︎
Scholefield G, et al. "Heparan sulfate mimetics as therapeutic agents for Alzheimer's disease". Brain. 2022. ↩︎
Brafman DA, et al. "Heparan sulfate modulates tau aggregation in Parkinson's disease". Journal of Neuroscience Research. 2004. ↩︎
Van V, et al. "Heparan sulfate proteoglycans and alpha-synuclein aggregation". Journal of Biological Chemistry. 2004. ↩︎
Fedele AO. "Sanfilippo syndrome: pathogenesis and clinical features". Journal of Inherited Metabolic Disorders. 2015. ↩︎
Pitkin J, et al. "Chondroitinase ABC promotes functional recovery after spinal cord injury". Experimental Neurology. 2023. ↩︎