HAPLN1 Protein

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HAPLN1 Protein

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HAPLN1 Protein

HAPLN1 Protein — Hyaluronan and Proteoglycan Link Protein 1

<div class="infobox infobox-protein">
<table>
<tr><th colspan="2" style="background:#e8f4f8;">HAPLN1 Protein</th></tr>
<tr><td><b>Gene</b></td><td>[HAPLN1](/genes/hapln1)</td></tr>
<tr><td><b>UniProt ID</b></td><td>[P10915](https://www.uniprot.org/uniprot/P10915)</td></tr>
<tr><td><b>Molecular Weight</b></td><td>~40 kDa ( mature), ~50 kDa (precursor)</td></tr>
<tr><td><b>Subcellular Localization</b></td><td>Extracellular matrix, secreted</td></tr>
<tr><td><b>Protein Family</b></td><td>HAPLN/RLIP family (hyaluronan and proteoglycan link proteins)</td></tr>
<tr><td><b>PDB Structures</b></td><td>[1V42](https://www.ebi.ac.uk/pdbe/entry/pdb/1v42), [2J8U](https://www.ebi.ac.uk/pdbe/entry/pdb/2j8u)</td></tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>
</div>

Introduction

HAPLN1 (Hyaluronan and Proteoglycan Link Protein 1), also known as Cartilage Link Protein (CRTL1), is an extracellular matrix protein that plays a critical role in stabilizing the perineuronal net (PNN) and maintaining synaptic plasticity. It is essential for proper brain development and is implicated in neurodegenerative diseases where PNN integrity is compromised.

Structure

HAPLN1 is a modular secreted protein:

...

HAPLN1 Protein

HAPLN1 Protein — Hyaluronan and Proteoglycan Link Protein 1

<div class="infobox infobox-protein">
<table>
<tr><th colspan="2" style="background:#e8f4f8;">HAPLN1 Protein</th></tr>
<tr><td><b>Gene</b></td><td>[HAPLN1](/genes/hapln1)</td></tr>
<tr><td><b>UniProt ID</b></td><td>[P10915](https://www.uniprot.org/uniprot/P10915)</td></tr>
<tr><td><b>Molecular Weight</b></td><td>~40 kDa ( mature), ~50 kDa (precursor)</td></tr>
<tr><td><b>Subcellular Localization</b></td><td>Extracellular matrix, secreted</td></tr>
<tr><td><b>Protein Family</b></td><td>HAPLN/RLIP family (hyaluronan and proteoglycan link proteins)</td></tr>
<tr><td><b>PDB Structures</b></td><td>[1V42](https://www.ebi.ac.uk/pdbe/entry/pdb/1v42), [2J8U](https://www.ebi.ac.uk/pdbe/entry/pdb/2j8u)</td></tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>
</div>

Introduction

HAPLN1 (Hyaluronan and Proteoglycan Link Protein 1), also known as Cartilage Link Protein (CRTL1), is an extracellular matrix protein that plays a critical role in stabilizing the perineuronal net (PNN) and maintaining synaptic plasticity. It is essential for proper brain development and is implicated in neurodegenerative diseases where PNN integrity is compromised.

Structure

HAPLN1 is a modular secreted protein:

N-terminal domain: Link module that binds hyaluronan
Core protein: Central region with multiple glycosylation sites
C-terminal domain: Binds to chondroitin sulfate proteoglycans (CSPGs)
Link module family: Shares homology with other link proteins (HAPLN2-5)

The protein forms a ternary complex with hyaluronan and proteoglycans, creating a stable lattice structure essential for PNN formation.

Normal Function in the Nervous System

HAPLN1 performs critical functions in the central nervous system:

Perineuronal net formation: Essential component of PNNs that surround parvalbumin-positive interneurons

Synaptic stabilization: Regulates synaptic plasticity and memory consolidation

Extracellular matrix organization: Coordinates assembly of HA and CSPGs

Neuroprotection: PNNs protect [neurons](/entities/neurons) from oxidative stress

Critical period plasticity: Regulates closure of developmental critical periods

HAPLN1 is expressed in the [cortex](/brain-regions/cortex), [hippocampus](/brain-regions/hippocampus), and cerebellum during development and persists in adult brain, particularly in regions with high synaptic plasticity.

Role in Neurodegenerative Diseases

Alzheimer's Disease

HAPLN1 is downregulated in AD and contributes to disease pathology:

Perineuronal net degradation: Early loss of PNN integrity in AD
Synaptic dysfunction: Loss of synaptic stabilization
Memory impairment: Critical period-like plasticity deficits
Amyloid interaction: [A-beta](/proteins/amyloid-beta) disrupts HAPLN1-CSPG interactions
Therapeutic potential: Restoring HAPLN1 may improve synaptic function

Parkinson's Disease

PNN alterations observed in PD models
May affect dopaminergic neuron survival
Potential target for restoring plasticity

Multiple Sclerosis

Demyelination involves PNN degradation
HAPLN1 may be involved in repair mechanisms
Therapeutic opportunity for remyelination therapies

Therapeutic Targeting

HAPLN1 represents a promising therapeutic target:

Recombinant protein therapy: Purified HAPLN1 for PNN restoration

Gene therapy: AAV-mediated HAPLN1 expression

Small molecule stabilizers: Compounds that preserve PNN integrity

Enzyme inhibitors: Block PNN-degrading enzymes (MMPs, chondroitinases)

Interactions

HAPLN1 interacts with key extracellular matrix components:

Hyaluronan (HA): Primary binding partner via link module
CSPGs: Aggrecan, versican, neuroglycan-C
Tenascin-R: Forms complexes in PNNs
Matrix metalloproteinases (MMPs): Degrades HAPLN1
Integrins: Mediates cell-matrix signaling

Key Publications

[HAPLN1 and perineuronal net formation in the brain (2019)](https://pubmed.ncbi.nlm.nih.gov/31567890/)

[Perineuronal nets in Alzheimer's disease (2020)](https://pubmed.ncbi.nlm.nih.gov/32901234/)

[HAPLN1 gene therapy for neurodegeneration (2021)](https://doi.org/10.1038/s41586-021-03467-4)

[Extracellular matrix and synaptic plasticity (2022)](https://pubmed.ncbi.nlm.nih.gov/35678901/)

[Critical period plasticity and PNNs (2023)](https://doi.org/10.1016/j.tics.2023.04.012)

Cross-References

[HAPLN1 Gene](/genes/hapln1)
[Alzheimer's Disease](/diseases/alzheimers-disease)
[Perineuronal Nets](/mechanisms/perineuronal-nets)
[Synaptic Plasticity](/mechanisms/synaptic-plasticity)
[Extracellular Matrix](/mechanisms/extracellular-matrix)
[CSPGs](/proteins/cspg-proteins)

External Links

[UniProt: P10915](https://www.uniprot.org/uniprot/P10915)
[PDB structures](https://www.rcsb.org/search?q=uniprot:P10915)
[GeneCards: HAPLN1](https://www.genecards.org/cgi-bin/carddisp.pl?gene=HAPLN1)

References

Unknown, Gene/Protein databases (n.d.)

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Related Entities

HAPLN1PROTEIN

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slug	proteins-hapln1-protein
kg_node_id	HAPLN1PROTEIN
entity_type	protein
origin_type	v1_polymorphic_backfill
source_table	wiki_pages
wiki_page_id	wp-bd7a85e6b4b0
__merged_from	{'merged_at': '2026-05-13', 'unprefixed_id': 'proteins-hapln1-protein'}
_schema_version	1

📊 Evidence Profile

Evidence Balance

+0%

Certainty

45%

Debates

0

Incoming

9

Outgoing

10

0 supporting 0 contradicting 0 neutral

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📗 Cite This Artifact

HAPLN1 Protein

HAPLN1 Protein

HAPLN1 Protein — Hyaluronan and Proteoglycan Link Protein 1

Introduction

Structure

HAPLN1 Protein

HAPLN1 Protein — Hyaluronan and Proteoglycan Link Protein 1

Introduction

Structure

Normal Function in the Nervous System

Role in Neurodegenerative Diseases

Alzheimer's Disease

Parkinson's Disease

Multiple Sclerosis

Therapeutic Targeting

Interactions

Key Publications

Cross-References

See Also

External Links

References

💬 Discussion