LDL Receptor Protein

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LDL Receptor Protein

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LDL Receptor Protein (LDLR)

<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">LDL Receptor Protein</th>
</tr>
<tr>
<td class="label">Symbol</td>
<td><strong>LDL-RECEPTOR</strong></td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>LDL Receptor</td>
</tr>
<tr>
<td class="label">Type</td>
<td>Protein</td>
</tr>
<tr>
<td class="label">UniProt</td>
<td><a href="https://www.uniprot.org/uniprot/?query=LDL-RECEPTOR" target="_blank">Search UniProt</a></td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/ad" style="color:#ef9a9a">AD</a>, <a href="/wiki/ali" style="color:#ef9a9a">ALI</a>, <a href="/wiki/als" style="color:#ef9a9a">ALS</a>, <a href="/wiki/alzheimer" style="color:#ef9a9a">ALZHEIMER</a>, <a href="/wiki/alzheimer's-disease" style="color:#ef9a9a">ALZHEIMER'S DISEASE</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">435 edges</a></td>
</tr>
</table>

Overview

The LDL Receptor (LDLR) is a cell surface receptor essential for cholesterol homeostasis. It mediates the uptake of circulating low-density lipoprotein (LDL) particles by cells through receptor-mediated endocytosis [@goldstein2005]. Beyond its well-established role in cardiovascular disease, the LDL receptor has emerged as an important player in [Alzheimer's disease](/diseases/alzheimers-disease) and other neurodegenerative conditions [@katsouri2020].

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LDL Receptor Protein (LDLR)

<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">LDL Receptor Protein</th>
</tr>
<tr>
<td class="label">Symbol</td>
<td><strong>LDL-RECEPTOR</strong></td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>LDL Receptor</td>
</tr>
<tr>
<td class="label">Type</td>
<td>Protein</td>
</tr>
<tr>
<td class="label">UniProt</td>
<td><a href="https://www.uniprot.org/uniprot/?query=LDL-RECEPTOR" target="_blank">Search UniProt</a></td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/ad" style="color:#ef9a9a">AD</a>, <a href="/wiki/ali" style="color:#ef9a9a">ALI</a>, <a href="/wiki/als" style="color:#ef9a9a">ALS</a>, <a href="/wiki/alzheimer" style="color:#ef9a9a">ALZHEIMER</a>, <a href="/wiki/alzheimer's-disease" style="color:#ef9a9a">ALZHEIMER'S DISEASE</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">435 edges</a></td>
</tr>
</table>

Overview

The LDL Receptor (LDLR) is a cell surface receptor essential for cholesterol homeostasis. It mediates the uptake of circulating low-density lipoprotein (LDL) particles by cells through receptor-mediated endocytosis [@goldstein2005]. Beyond its well-established role in cardiovascular disease, the LDL receptor has emerged as an important player in [Alzheimer's disease](/diseases/alzheimers-disease) and other neurodegenerative conditions [@katsouri2020].

In the brain, the LDL receptor participates in lipid metabolism, amyloid precursor protein (APP) processing, and the clearance of neurotoxic proteins. The receptor is expressed on neurons, astrocytes, and microglial cells, where it participates in various aspects of brain lipid homeostasis and neuronal function [@pitas2000]. Its role in [cerebral amyloid angiopathy](/diseases/cerebral-amyloid-angiopathy) (CAA) is particularly relevant to neurodegenerative disease, as it helps clear amyloid-beta from the brain vasculature.

Structure and Molecular Architecture

The LDL receptor is a type I transmembrane glycoprotein with a complex multi-domain structure:

Extracellular Domains

Ligand-binding repeats (LA repeats): Seven repeats of approximately 40 amino acids each, containing negatively charged amino acids that interact with positively charged residues on apolipoproteins
EGF-like domains: Three epidermal growth factor precursor homology domains
O-linked sugar domain: A region with O-linked glycosylation
Transmembrane domain: Single pass transmembrane helix (22 amino acids)
Cytoplasmic tail: Contains an NPXY internalization signal and a di-leucine sorting motif

Key Structural Features

LA repeats 1-4: Primary binding site for LDL and VLDL

LA repeats 5-7: Bind apoE-rich lipoproteins (HDL, chylomicron remnants)

EGF precursor homology domain: Required for dissociation of ligand at low pH

NPXY motif: Mediates clathrin-mediated endocytosis via adaptor proteins

The receptor undergoes conformational changes that are pH-dependent, enabling efficient ligand release in endosomes [@rudenko2002].

LDLR: Classic LDL receptor
LDLR-related protein 1 (LRP1): Larger relative with broader ligand specificity
LRP2 (Megalin): Expressed in epithelial cells
LRP1B: Brain-enriched isoform with distinct trafficking
ApoER2 (LRP8): Neuron-specific LDL receptor family member

Biological Functions

Cholesterol Homeostasis

The primary function of LDLR is regulating plasma cholesterol levels:

LDL uptake: LDLR binds LDL particles circulating in blood

Receptor-mediated endocytosis: Clathrin-coated pits internalize the receptor-ligand complex

Endosomal trafficking: Acidic pH triggers ligand release

Recycling: The receptor returns to the cell surface for multiple rounds of uptake

Degradation: Ligands are delivered to lysosomes for degradation

This pathway controls approximately 70% of LDL clearance from plasma [@hobbs1990].

Lipoprotein Processing in Brain

In the central nervous system, LDLR participates in:

ApoE-lipoprotein clearance: LDLR binds apoE-containing lipoproteins in brain interstitial fluid
Cholesterol efflux: Facilitates removal of excess cholesterol from neurons
Myelin maintenance: Supports lipid metabolism required for myelin synthesis
Synaptic function: Lipid homeostasis is essential for synaptic vesicle dynamics

Amyloid Clearance

LDLR has emerged as an important receptor for amyloid-beta clearance:

ApoE-dependent clearance: LDLR, particularly the ApoE2 isoform, facilitates amyloid-beta clearance when bound to apoE lipoproteins

Cerebral amyloid angiopathy: LDLR-mediated clearance of vascular amyloid is critical for preventing CAA

Transcytosis: LDLR may mediate transcytosis of amyloid-beta across the blood-brain barrier

Role in Neurodegenerative Diseases

Alzheimer's Disease

LDLR dysfunction contributes to [Alzheimer's disease](/diseases/alzheimers-disease) through multiple mechanisms:

Amyloid clearance impairment: Reduced LDLR expression in AD brain correlates with decreased amyloid clearance

ApoE metabolism: LDLR regulates apoE levels; LDLR variants affect AD risk through apoE-dependent mechanisms

Cholesterol dysregulation: Altered neuronal cholesterol homeostasis affects APP processing and amyloid production

Synaptic dysfunction: Lipid dysregulation impairs synaptic function and plasticity

Genetic studies have identified LDLR variants that modify AD risk, particularly in interaction with APOE alleles [@zerbinatti2006].

Cerebral Amyloid Angiopathy

In [cerebral amyloid angiopathy](/diseases/cerebral-amyloid-angiopathy):

Vascular amyloid deposition: LDLR dysfunction impairs clearance of amyloid-beta from cerebral vessels

Hemorrhagic risk: Accumulated vascular amyloid increases risk of lobar hemorrhages

Cerebral amyloid angiopathy subtypes: CAA often accompanies AD but can occur independently

Therapeutic target: Enhancing LDLR function may reduce vascular amyloid burden

Parkinson's Disease

In [Parkinson's disease](/diseases/parkinsons-disease):

Lipid metabolism: Altered lipid metabolism is increasingly recognized in PD pathogenesis

Alpha-synuclein interaction: LDLR may influence alpha-synuclein clearance pathways

Neuroinflammation: LDLR affects microglial function and neuroinflammation

Energy metabolism: Cholesterol homeostasis affects mitochondrial function in dopaminergic neurons

Atherosclerosis and Stroke

LDLR has well-established roles in:

Familial hypercholesterolemia: LDLR mutations cause autosomal dominant hypercholesterolemia

Atherosclerosis: Elevated LDL accelerates plaque formation

Ischemic stroke: Large artery atherosclerosis is a major cause of stroke

Small vessel disease: LDLR dysfunction may contribute to small vessel pathology

Therapeutic Implications

Targeting LDLR in Neurodegeneration

Enhancing LDLR function may benefit neurodegenerative disease:

Statins: LDL-lowering drugs that indirectly upregulate LDLR expression

LDLR agonists: Small molecules that directly enhance LDLR function

Gene therapy: Viral delivery to increase LDLR expression in brain

ApoE-targeted approaches: Modulate the LDLR-apoE interaction

Combination Strategies

LDLR-targeted approaches may be combined with:

[Amyloid clearance](/mechanisms/amyloid-clearance-pathways) agents
[Lipid metabolism](/mechanisms/brain-lipid-metabolism) modulators
[Neuroinflammation](/mechanisms/neuroinflammation) reduction strategies

Protein Interactions

Ligands and Lipoproteins

LDL: Primary ligand, contains cholesteryl esters
VLDL: Very low-density lipoprotein
IDL: Intermediate-density lipoprotein
HDL: High-density lipoprotein (apoE-rich)
ApoB-100: Structural protein of LDL/VLDL
ApoE: Apolipoprotein that mediates binding to LDLR

Adaptor Proteins

LDLRAP1 (ARH): Adaptor protein required for LDLR internalization
Clathrin: Coat protein for endocytosis
Dynamin: GTPase that pinches off endocytic vesicles
PCSK9: Proprotein convertase that promotes LDLR degradation

Brain-Specific Interactions

ApoE: Primary apolipoprotein for brain LDLR function
Amyloid-beta: Can bind to LDLR and be cleared
LRP1: Related receptor that cooperates in clearance

Expression Pattern

LDLR is widely expressed with tissue-specific patterns:

Brain Regions

Cerebral cortex: Pyramidal neurons and interneurons
Hippocampus: CA1-CA3 pyramidal neurons, dentate granule cells
Cerebellum: Purkinje cells
Basal ganglia: Striatal neurons
Substantia nigra: Dopaminergic neurons

Cell Types

Neurons: High expression, particularly in excitatory neurons
Astrocytes: Moderate expression, important for apoE metabolism
Microglia: Lower baseline, upregulated in inflammation
Endothelial cells: At the blood-brain barrier

Peripheral Tissues

Liver: Highest expression, primary site of LDL clearance
Adrenal: Steroid hormone synthesis requires cholesterol
Ovary: Cholesterol for steroidogenesis
Testis: Spermatogenesis requires cholesterol

Summary

The LDL Receptor (LDLR) is a cell surface receptor that plays critical roles in cholesterol homeostasis and lipid metabolism. While its primary function in peripheral tissues is clearance of circulating LDL particles, in the brain LDLR participates in amyloid-beta clearance, apoE metabolism, and neuronal lipid homeostasis. LDLR dysfunction contributes to Alzheimer's disease, cerebral amyloid angiopathy, and potentially other neurodegenerative conditions. The receptor represents a promising therapeutic target for preserving brain lipid metabolism and enhancing amyloid clearance.

External Links

[UniProt: P01130](https://www.uniprot.org/uniprotkb/P01130)
[NCBI Gene: 3949](https://www.ncbi.nlm.nih.gov/gene/3949)
[KEGG Pathway: Cholesterol metabolism](https://www.genome.jp/kegg/pathway/map04979)

References

[Goldstein JL, et al., LDL receptor and the cholesterol metabolism (2005) (2005)](https://pubmed.ncbi.nlm.nih.gov/15993327/)

[Katsouri L, et al., LDL receptor in Alzheimer's disease (2020) (2020)](https://pubmed.ncbi.nlm.nih.gov/32845678/)

[Pitas RE, et al., Lipoprotein receptors in the CNS (2000) (2000)](https://pubmed.ncbi.nlm.nih.gov/11016957/)

[Rudenko G, et al., Structure of the LDL receptor (2002) (2002)](https://pubmed.ncbi.nlm.nih.gov/12417541/)

[Hobbs HH, et al., Molecular genetics of the LDL receptor (1990) (1990)](https://pubmed.ncbi.nlm.nih.gov/2162946/)

[Zerbinatti CV, et al., LDL receptor family and amyloid clearance (2006) (2006)](https://pubmed.ncbi.nlm.nih.gov/16960660/)

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Related Entities

LDLRECEPTOR

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📊 Evidence Profile Foundational

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📗 Cite This Artifact

LDL Receptor Protein

LDL Receptor Protein (LDLR)

Overview

LDL Receptor Protein (LDLR)

Overview

Structure and Molecular Architecture

Extracellular Domains

Key Structural Features

Biological Functions

Cholesterol Homeostasis

Lipoprotein Processing in Brain

Amyloid Clearance

Role in Neurodegenerative Diseases

Alzheimer's Disease

Cerebral Amyloid Angiopathy

Parkinson's Disease

Atherosclerosis and Stroke

Therapeutic Implications

Targeting LDLR in Neurodegeneration

Combination Strategies

Protein Interactions

Ligands and Lipoproteins

Adaptor Proteins

Brain-Specific Interactions

Expression Pattern

Brain Regions

Cell Types

Peripheral Tissues

Summary

See Also

External Links

References

💬 Discussion

📗 Cite This Artifact

LDL Receptor Protein

LDL Receptor Protein (LDLR)

Overview

LDL Receptor Protein (LDLR)

Overview

Structure and Molecular Architecture

Extracellular Domains

Key Structural Features

Isoforms and Related Proteins

Biological Functions

Cholesterol Homeostasis

Lipoprotein Processing in Brain

Amyloid Clearance

Role in Neurodegenerative Diseases

Alzheimer's Disease

Cerebral Amyloid Angiopathy

Parkinson's Disease

Atherosclerosis and Stroke

Therapeutic Implications

Targeting LDLR in Neurodegeneration

Combination Strategies

Protein Interactions

Ligands and Lipoproteins

Adaptor Proteins

Brain-Specific Interactions

Expression Pattern

Brain Regions

Cell Types

Peripheral Tissues

Summary

See Also

External Links

References

💬 Discussion