ApoER2 Protein

ApoER2 (LRP8) Protein

<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">ApoER2 Protein</th>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>LRP8</td>
</tr>
<tr>
<td class="label">Protein Name</td>
<td>Apolipoprotein E Receptor 2 (ApoER2)</td>
</tr>
<tr>
<td class="label">Molecular Weight</td>
<td>~110 kDa (full-length), 85 kDa (truncated)</td>
</tr>
<tr>
<td class="label">Structure</td>
<td>963 amino acids</td>
</tr>
<tr>
<td class="label">Aliases</td>
<td>LDLRR, LR8, APOER2</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>Q9UBJ2</td>
</tr>
<tr>
<td class="label">Tissue Expression</td>
<td>Brain (neurons), testis, platelets</td>
</tr>
<tr>
<td class="label">Partner</td>
<td>Interaction Type</td>
</tr>
<tr>
<td class="label">Reelin</td>
<td>Ligand binding</td>
</tr>
<tr>
<td class="label">VLDLR</td>
<td>Co-receptor</td>
</tr>
<tr>
<td class="label">Dab1</td>
<td>Adaptor protein</td>
</tr>
<tr>
<td class="label">APOE</td>
<td>Ligand binding</td>
</tr>
<tr>
<td class="label">[NMDA Receptor](/entities/nmda-receptor)</td>
<td>Physical association</td>
</tr>
<tr>
<td class="label">PSD-95</td>
<td>Scaffold interaction</td>
</tr>
<tr>
<td class="label">Approach</td>
<td>Status</td>
</tr>
<tr>
<td class="label">Reelin mimetics</td>
<td>Preclinical</td>
</tr>
<tr>
<td class="label">Dab1 stabilizers</td>
<td>Discovery</td>
</tr>
<tr>

...

ApoER2 (LRP8) Protein

<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">ApoER2 Protein</th>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>LRP8</td>
</tr>
<tr>
<td class="label">Protein Name</td>
<td>Apolipoprotein E Receptor 2 (ApoER2)</td>
</tr>
<tr>
<td class="label">Molecular Weight</td>
<td>~110 kDa (full-length), 85 kDa (truncated)</td>
</tr>
<tr>
<td class="label">Structure</td>
<td>963 amino acids</td>
</tr>
<tr>
<td class="label">Aliases</td>
<td>LDLRR, LR8, APOER2</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>Q9UBJ2</td>
</tr>
<tr>
<td class="label">Tissue Expression</td>
<td>Brain (neurons), testis, platelets</td>
</tr>
<tr>
<td class="label">Partner</td>
<td>Interaction Type</td>
</tr>
<tr>
<td class="label">Reelin</td>
<td>Ligand binding</td>
</tr>
<tr>
<td class="label">VLDLR</td>
<td>Co-receptor</td>
</tr>
<tr>
<td class="label">Dab1</td>
<td>Adaptor protein</td>
</tr>
<tr>
<td class="label">APOE</td>
<td>Ligand binding</td>
</tr>
<tr>
<td class="label">[NMDA Receptor](/entities/nmda-receptor)</td>
<td>Physical association</td>
</tr>
<tr>
<td class="label">PSD-95</td>
<td>Scaffold interaction</td>
</tr>
<tr>
<td class="label">Approach</td>
<td>Status</td>
</tr>
<tr>
<td class="label">Reelin mimetics</td>
<td>Preclinical</td>
</tr>
<tr>
<td class="label">Dab1 stabilizers</td>
<td>Discovery</td>
</tr>
<tr>
<td class="label">Small molecule modulators</td>
<td>Preclinical</td>
</tr>
</table>

Introduction

Apoer2 Protein is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.

Overview

ApoER2 ([Apolipoprotein E](/proteins/apoe) Receptor 2), also known as LRP8, is a member of the Low-Density Lipoprotein Receptor family. It is primarily expressed in the brain and plays critical roles in synaptic function, neuronal development, and lipid metabolism. ApoER2 is a key receptor for both Reelin signaling and apolipoprotein E (APOE)-containing lipoproteins, making it a crucial nexus between lipid metabolism and neuronal function. The receptor is expressed predominantly in neurons throughout the brain, with highest levels in the hippocampus, cortex, and cerebellum. [@herz2006]

Protein Information

Structure

ApoER2 is a type I transmembrane glycoprotein with multiple functional domains:

Extracellular Domain

• Ligand-Binding Repeats (8): Cys-rich repeats that bind Reelin and APOE
• EGF-Like Repeats (3): Required for pH-dependent ligand release
• Truncated Isoforms: Brain-expressed isoforms lack some repeats

Transmembrane Domain

• Single alpha-helical transmembrane segment
• Links extracellular and intracellular domains

Cytoplasmic Tail

• NPXY Internalization Signals: Two NPXY motifs for endocytosis
• Tyrosine Phosphorylation Sites: Critical for downstream signaling
• Dileucine Motif: Additional sorting signal

Molecular Function

Reelin Signaling

ApoER2 is the primary Reelin receptor in neurons:

Reelin binds to ApoER2 (and VLDLR) with high affinity

Triggers Dab1 phosphorylation cascade

Inhibits glycogen synthase kinase-3β (GSK-3β)

Promotes microtubule stabilization

Enhances NMDA receptor function

Facilitates synaptic plasticity

Lipoprotein Receptor Function

• Binds APOE-containing lipoproteins (primarily APOE4 isoform)
• Mediates neuronal cholesterol uptake
• Participates in brain lipid homeostasis
• Regulates synaptic membrane composition

NMDA Receptor Modulation

• Co-localizes with NMDA receptors at synapses
• Enhances NMDA receptor phosphorylation
• Potentiates NMDA-mediated calcium influx
• Critical for [LTP](/mechanisms/long-term-potentiation) and memory formation

Expression Pattern

Brain Regional Distribution

• [Hippocampus](/brain-regions/hippocampus): Highest expression in CA1 pyramidal neurons
• Cerebral [Cortex](/brain-regions/cortex): Layer-specific expression patterns
• Cerebellum: Purkinje cells and granule cells
• Basal Ganglia: Moderate expression

Cell Type Specificity

• [Neurons](/entities/neurons): Primary expression site
• [Astrocytes](/entities/astrocytes): Low expression
• [Microglia](/entities/microglia): Minimal expression
• Endothelial Cells: Vascular expression

Developmental Regulation

• Highest expression during embryonic development
• Continues in adult brain
• Regulated by neuronal activity

Disease Implications

Alzheimer's Disease

• Genetic Variants: LRP8 polymorphisms modify AD risk
• Aβ Metabolism: Affects [amyloid-beta](/proteins/amyloid-beta) clearance
• APOE4 Interaction: APOE4-ApoER2 signaling is impaired
• Synaptic Dysfunction: Contributes to memory deficits
• Therapeutic Target: Reelin/ApoER2 signaling enhancement

Neurodevelopmental Disorders

• Mutations cause autosomal recessive intellectual disability
• Impaired Reelin signaling disrupts neuronal migration
• Associated with cortical malformations
• Comorbidities: epilepsy, motor deficits

Stroke and Cerebrovascular Disease

• LRP8 polymorphisms modulate stroke risk
• May affect cerebral vascular integrity
• APOE4-ApoER2 interaction in vascular dementia
• Potential for cerebrovascular therapeutics

Atherosclerosis

• Expressed in vascular smooth muscle cells
• May affect systemic lipid metabolism
• Interaction with circulating lipoproteins

Molecular Mechanisms

Reelin Signaling Cascade

Reelin binds to ApoER2/VLDLR receptor complex

Src family kinases phosphorylate Dab1

Dab1 recruits PI3K and downstream effectors

Akt/PKB activation inhibits [GSK-3β](/entities/gsk3-beta)

Reduced [tau](/proteins/tau) phosphorylation

Enhanced synaptic plasticity

Interaction Network

Therapeutic Targeting

Current Strategies

Emerging Approaches

• Gene therapy for LRP8 mutations
• AAV-mediated Reelin delivery
• Peptide agonists for ApoER2
• Combination with APOE-targeting therapies

Animal Models

• ApoER2 Knockout Mice: Mild neurological phenotype, enhanced [LTP](/mechanisms/long-term-potentiation) deficits with APOE4
• Conditional Knockouts: Region-specific deletion studies
• Transgenic Overexpression: Rescue of synaptic deficits

Research Directions

• Defining isoform-specific functions
• Developing brain-penetrant small molecules
• Understanding APOE4-ApoER2 interaction in AD
• Biomarker potential: soluble ApoER2 as marker

Background

The study of Apoer2 Protein has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.

Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.

See Also

• LRP8 Gene
• Reelin Signaling
• [Synaptic Plasticity](/mechanisms/synaptic-plasticity)
• Apolipoprotein E
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [VLDLR Protein](/proteins/vldlr-protein)

External Links

• [LRP8 Protein - NCBI](https://www.ncbi.nlm.nih.gov/protein/NP_001018807)
• [UniProt: Q9UBJ2](https://www.uniprot.org/uniprot/Q9UBJ2)
• [LRP8 - GeneCards](https://www.genecards.org/cgi-bin/carddisp.pl?gene=LRP8)

References

[Trommsdorff et al., 1999, Reelin and ApoER2 in neuronal migration (1999)](https://pubmed.ncbi.nlm.nih.gov/10436159/)

[Unknown, Herz and Chen, 2006. LRP8 in neurodegeneration. Nat Rev Neurosci (2006)](https://pubmed.ncbi.nlm.nih.gov/16641937/)

[Lane-Donovan et al., 2014, Lipoprotein receptors in brain function (2014)](https://pubmed.ncbi.nlm.nih.gov/25148686/)

[Beffert et al., 2005, ApoER2 and Reelin in synaptic plasticity (2005)](https://pubmed.ncbi.nlm.nih.gov/15953421/)

[D'Arcangelo et al., 2009, Reelin signaling in neuropsychiatric disease (2009)](https://pubmed.ncbi.nlm.nih.gov/19680242/)

[Chen et al., 2010, LRP8 and Alzheimer's disease (2010)](https://pubmed.ncbi.nlm.nih.gov/20463221/)

[Hiesberger et al., 1999, Direct binding of Reelin to ApoER2 (1999)](https://pubmed.ncbi.nlm.nih.gov/10436158/)

[Bal et al., 2013, ApoER2 and NMDA receptor function (2013)](https://pubmed.ncbi.nlm.nih.gov/24162653/)