LRP2 Protein - Megalin

LRP2 Protein (Megalin)

Pathway Diagram

```mermaid
flowchart TD
LRP2["LRP2<br/>(Low-density lipoprotein<br/>receptor-related protein 2)"]

%% Direct regulatory targets
MAP1LC3B["MAP1LC3B<br/>(Autophagy marker<br/>LC3B)"]
MYC["MYC<br/>(Oncogene<br/>transcription factor)"]

%% Pathological processes
Neurodegeneration["Neurodegeneration<br/>(Progressive neuron<br/>loss)"]
ALS["ALS<br/>(Amyotrophic lateral<br/>sclerosis)"]
FTD["FTD<br/>(Frontotemporal<br/>dementia)"]

%% Inflammatory and immune responses
Inflammation["Inflammation<br/>(Immune response<br/>activation)"]
Autoimmune["Autoimmune<br/>(Self-reactive<br/>immunity)"]

%% Vascular pathology
Ischemia["Ischemia<br/>(Reduced blood<br/>flow)"]
Stroke["Stroke<br/>(Cerebrovascular<br/>accident)"]
Atherosclerosis["Atherosclerosis<br/>(Arterial plaque<br/>formation)"]

%% Metabolic dysfunction
MetabolicSyndrome["Metabolic Syndrome<br/>(Insulin resistance<br/>and dyslipidemia)"]

%% Outcomes
Aging["Aging<br/>(Cellular<br/>senescence)"]

%% Connections
LRP2 -->|"regulates"| MAP1LC3B
LRP2 -->|"regulates"| MYC
LRP2 -->|"activates"| Neurodegeneration
LRP2 -->|"activates"| ALS
LRP2 -->|"associated_with"| FTD
LRP2 -->|"activates"| Inflammation
LRP2 -->|"activates"| Autoimmune
LRP2 -->|"regulates"| Ischemia
LRP2 -->|"associated_with"| Stroke
LRP2 -->|"associated_with"| Atherosclerosis
LRP2 -->|"activates"| MetabolicSyndrome
LRP2 -->|"associated_with"| Aging

%% Cross-p

LRP2 Protein (Megalin)

Pathway Diagram

Introduction

Lrp2 Protein Megalin is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.

<div class="infobox infobox-protein"> [@camezind2022]
<table> [@zlatic2021]
<tr><th colspan="2" style="background:#f0f0f0;">LRP2 Protein (Megalin)</th></tr> [@bell2020]
<tr><td><b>Protein Name</b></td><td>Megalin</td></tr> [@carro2019]
<tr><td><b>Gene</b></td><td>[LRP2](/genes/lrp2)</td></tr> [@dietrich2018]
<tr><td><b>UniProt</b></td><td><a href="https://www.uniprot.org/uniprot/P98164" target="_blank">P98164</a></td></tr> [@gajera2017]
<tr><td><b>Molecular Weight</b></td><td>~600 kDa</td></tr> [@nagai2021]
<tr><td><b>Length</b></td><td>4,630 amino acids</td></tr>
<tr><td><b>Cellular Location</b></td><td>Apical plasma membrane, Endosomes, Lysosomes</td></tr>
<tr><td><b>Expression</b></td><td>Kidney proximal tubules, Choroid plexus, Brain endothelium, Retina, Lung</td></tr>
<tr><td><b>Aliases</b></td><td>Megalin, GP330, LRP-2</td></tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/ad" style="color:#ef9a9a">AD</a>, <a href="/wiki/adh" style="color:#ef9a9a">ADH</a>, <a href="/wiki/als" style="color:#ef9a9a">ALS</a>, <a href="/wiki/ami" style="color:#ef9a9a">AMI</a>, <a href="/wiki/aging" style="color:#ef9a9a">Aging</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">182 edges</a></td>
</tr>
</table>
</div>

Overview

LRP2, also known as Megalin, is one of the largest cell surface receptors in the human genome and belongs to the low-density lipoprotein receptor (LDLR) family. This multi-ligand scavenger receptor plays critical roles in endocytic uptake of diverse cargo molecules, including vitamins, lipids, hormones, and proteins. In the brain, Megalin is expressed primarily at the choroid plexus and brain microvascular endothelial cells, where it participates in blood-cerebrospinal fluid barrier (BCSFB) and blood-brain barrier (BBB) function. Recent research has implicated Megalin in the pathogenesis of neurodegenerative diseases, particularly Alzheimer's disease and Parkinson's disease, through its role in protein clearance and lipid metabolism.

Structure

Megalin is a type I transmembrane protein with an extraordinarily complex domain architecture:

• Ligand-Binding Repeats (30 domains): The extracellular region contains 30 complement-type ligand-binding repeats organized into five clusters, each capable of binding multiple ligands including apolipoproteins, vitamin-binding proteins, and matrix proteins.
• EGF-like Domains (31 domains): Epidermal growth factor-like domains interspersed between ligand-binding repeats, providing structural flexibility and pH-dependent ligand release.
• Transmembrane Domain: A single pass transmembrane helix anchors the receptor in the plasma membrane.
• Cytoplasmic Tail (213 aa): Contains multiple NPXY motifs that mediate clathrin-mediated endocytosis through interaction with disabled-2 (Dab2) and ARH adaptors. The tail also contains serine/threonine residues subject to regulatory phosphorylation.

Normal Function

Endocytic Reuptake

• Albumin and transferrin
• Vitamin D-binding protein and retinol-binding protein
• Apolipoproteins (ApoE, ApoJ/Clusterin)
• LRP2 ligands and various hormones

Blood-Cerebrospinal Fluid Barrier Function

• Receptor-mediated transcytosis of vitamin D and vitamin A across the BCSFB
• Clearance of [amyloid-beta](/proteins/amyloid-beta) (Aβ) from the CSF
• Removal of toxic proteins and metabolites

Lipid Metabolism

Role in Neurodegenerative Diseases

Alzheimer's Disease

Multiple lines of evidence support a role for LRP2/Megalin in Alzheimer's disease pathogenesis:

Parkinson's Disease

LRP2 has also been implicated in Parkinson's disease:

Other Neurodegenerative Conditions

• Amyotrophic Lateral Sclerosis (ALS): Altered LRP2 expression has been reported in ALS patient brains and in models of motor neuron degeneration.
• Multiple Sclerosis: Megalin autoantibodies have been detected in some MS patients, suggesting a potential role in disease pathogenesis.

Therapeutic Implications

The strategic position of LRP2 at the blood-brain interfaces makes it an attractive target for therapeutic intervention:

Key Interactions

| Protein/Pathway | Interaction Type | Functional Consequence |
|-----------------|-----------------|----------------------|
| ApoE | Receptor-ligand | Lipid transport, Aβ clearance |
| Amyloid-beta | Receptor-mediated endocytosis | Aβ clearance from brain |
| Transferrin | Receptor-ligand | Iron homeostasis |
| Clusterin (ApoJ) | Receptor-ligand | Chaperone, Aβ clearance |
| Dab2 | Adaptor protein | Clathrin-mediated endocytosis |
| ARH | Adaptor protein | Clathrin-mediated endocytosis |

See Also

• [LRP2 Gene](/genes/lrp2)
• [Blood-Brain Barrier](/entities/blood-brain-barrier)
• [Choroid Plexus](/cell-types/choroid-plexus)
• [Amyloid Cascade Hypothesis](/mechanisms/amyloid-cascade-pathway)
• [Alpha-Synuclein Pathway](/mechanisms/alpha-synuclein-aggregation-pathway)
• [Neuroinflammation in AD](/mechanisms/neuroinflammation-alzheimers)

External Links

• [UniProt: P98164](https://www.uniprot.org/uniprot/P98164)
• [Wikipedia: LRP2](https://en.wikipedia.org/wiki/LRP2)
• [NCBI Gene: 4033](https://www.ncbi.nlm.nih.gov/gene/4033)
• [Allen Brain Atlas: LRP2](https://human.brain-map.org/microarray/search/show?search_term=LRP2)

Background

The study of Lrp2 Protein Megalin 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.

References