Transferrin Receptor 2

Overview

Transferrin Receptor 2 is a protein. This page describes its structure, normal nervous system function, role in neurodegenerative disease, and potential as a therapeutic target.

Transferrin receptor 2 (TFR2) is a transmembrane protein that mediates cellular iron uptake and plays a critical role in systemic iron homeostasis. Unlike the ubiquitously expressed transferrin receptor 1 (TFR1), TFR2 has a more restricted tissue distribution and serves primarily as an iron sensor that regulates hepcidin expression.

Structure and Function

Molecular Architecture

TFR2 is a type II transmembrane glycoprotein composed of^{1Molecular cloning of transferrin receptor 21999 · Journal of Biological Chemistry · PMID 10636724Open reference}:

• 801 amino acids in humans

• Large extracellular domain: Contains the transferrin-binding site

• Single transmembrane domain: Anchors the protein to the membrane

• Short cytoplasmic tail: Contains internalization signals

TFR2 shares approximately 45% sequence homology with TFR1 but has distinct functional properties^{2Structure of transferrin receptor 2 and implications for hemochromatosis2000 · Proceedings of the National Academy of Sciences · PMID 11162978Open reference}.

Transferrin Binding

TFR2 binds holo-transferrin (iron-loaded transferrin) with lower affinity than TFR1^{3Expression of transferrin receptor 2 in normal and neoplastic hematopoietic cells2004 · Blood · PMID 15201106Open reference}:

• TFR1: Kd ~1 nM (high affinity)

• TFR2: Kd ~30 nM (lower affinity)

• This difference allows TFR2 to function as an iron sensor

• Only activates at higher transferrin saturation levels

Iron Sensing Function

TFR2 acts as a sensor of systemic iron status^{4Transferrin receptor 2: a new player in iron sensing and hemochromatosis2013 · Cell Metabolism · PMID 23719327Open reference}:

1. Holo-transferrin binding: Occurs when circulating iron is high

2. Signaling cascade: Activates ERK/MAPK pathway

3. Hepcidin induction: Increases hepcidin expression

4. Homeostatic response: Reduces iron absorption

Role in Liver Iron Regulation

Hepatocyte Expression

TFR2 is predominantly expressed in hepatocytes and is essential for hepcidin regulation^{5Combined deletion of Hfe and transferrin receptor 2 in mice leads to marked dysregulation of hepcidin and iron overload2007 · Hepatology · PMID 17959927Open reference}:

• Forms a complex with HFE (hereditary hemochromatosis protein)

• HFE-TFR2 complex senses holo-transferrin

• Activates BMP/SMAD signaling pathway

• Induces hepcidin transcription

Hemochromatosis Type 3

Mutations in TFR2 cause hereditary hemochromatosis type 3^{6The gene TFR2 is mutated in a new type of haemochromatosis mapping to 7q222000 · Nature Genetics · PMID 10854245Open reference}:

• Autosomal recessive inheritance

• Reduced hepcidin expression

• Increased iron absorption

• Iron overload in liver and other organs

Role in Neurodegeneration

Brain Expression

TFR2 is expressed in the brain, including^{7Age-dependent and iron-independent localization of iron regulatory proteins 1 and 2 in the brains of Belgrade rats2006 · Neuroscience · PMID 16473185Open reference}:

• Neurons in specific regions

• Astrocytes and microglia

• Brain endothelial cells

Iron Homeostasis in the Brain

TFR2 contributes to brain iron regulation^{8Iron metabolism in the central nervous system and neurodegenerative disorders2013 · Current Opinion in Neurobiology · PMID 23719329Open reference}:

• Modulates iron sensing in glial cells

• May affect blood-brain barrier iron transport

• Interacts with other iron regulatory proteins

Neurodegenerative Disease Associations

Alzheimer’s Disease

In Alzheimer’s disease, altered TFR2 expression has been reported^{9Hepcidin, ferroportin and brain iron homeostasis2013 · Neurobiology of Disease · PMID 24424461Open reference}:

• Changes in TFR2 levels in affected brain regions

• May contribute to iron accumulation around amyloid plaques

• Potential role in iron-mediated oxidative stress

Parkinson’s Disease

In Parkinson’s disease^{10Brain iron is associated with accelerated cognitive decline in people with Alzheimer pathology2018 · Molecular Psychiatry · PMID 28842895Open reference}:

• TFR2 expression altered in substantia nigra

• Iron accumulation may involve TFR2 dysregulation

• Potential contribution to dopaminergic neuron vulnerability

Friedreich’s Ataxia

TFR2 polymorphisms have been studied in Friedreich’s ataxia^{2Structure of transferrin receptor 2 and implications for hemochromatosis2000 · Proceedings of the National Academy of Sciences · PMID 11162978Open reference}0:

• May modify disease severity

• Iron chelation therapy responses may vary

• Potential biomarker for treatment stratification

Interaction with Other Proteins

Therapeutic Implications

Targeting TFR2-Hepcidin Axis

Modulating TFR2 signaling may have therapeutic potential^{2Structure of transferrin receptor 2 and implications for hemochromatosis2000 · Proceedings of the National Academy of Sciences · PMID 11162978Open reference}1:

• Small molecules enhancing TFR2 signaling

• Increasing hepcidin to reduce iron absorption

• May benefit disorders of iron overload

• Potential applications in neurodegeneration

Iron Chelation Synergy

TFR2 status may predict iron chelation responses^{2Structure of transferrin receptor 2 and implications for hemochromatosis2000 · Proceedings of the National Academy of Sciences · PMID 11162978Open reference}2:

• Patients with TFR2 dysfunction may respond differently

• Biomarker for personalized iron chelation therapy

• May guide deferiprone dosing

Research Directions

Current research focuses on^{2Structure of transferrin receptor 2 and implications for hemochromatosis2000 · Proceedings of the National Academy of Sciences · PMID 11162978Open reference}3:

1. TFR2 signaling mechanisms in brain cells

2. TFR2 as a therapeutic target for iron disorders

3. Biomarker development for iron status

4. Role in neuroinflammation

5. Interaction with ferroptosis pathways

Pathway & Interaction Diagram

Interactive diagram showing TRANSFERRIN RECEPTOR 2’s key relationships in the SciDEX knowledge graph (7 connections shown).

flowchart TD
    TRANSFERRIN_RECEPTOR_2["TRANSFERRIN RECEPTOR 2"]
    TRANSFERRIN["TRANSFERRIN"]
    IRON_METABOLISM["IRON METABOLISM"]
    HEMOCHROMATOSIS["HEMOCHROMATOSIS"]
    HEPATOCYTE["HEPATOCYTE"]
    ERYTHROID_PRECURSOR["ERYTHROID PRECURSOR"]
    ERYTHROPOIESIS["ERYTHROPOIESIS"]
    IRON_TRANSPORT["IRON TRANSPORT"]

    TRANSFERRIN_RECEPTOR_2 -->|"binds to"| TRANSFERRIN
    TRANSFERRIN_RECEPTOR_2 -->|"involved in"| IRON_METABOLISM
    TRANSFERRIN_RECEPTOR_2 -->|"associated with"| HEMOCHROMATOSIS
    TRANSFERRIN_RECEPTOR_2 -->|"expressed in"| HEPATOCYTE
    TRANSFERRIN_RECEPTOR_2 -->|"expressed in"| ERYTHROID_PRECURSOR
    TRANSFERRIN_RECEPTOR_2 -->|"regulates"| ERYTHROPOIESIS
    TRANSFERRIN_RECEPTOR_2 -->|"involved in"| IRON_TRANSPORT

    style TRANSFERRIN_RECEPTOR_2 fill:#1a237e,stroke:#4fc3f7,stroke-width:3px,color:#fff

See Also

• Alzheimer’s disease

• Parkinson’s disease

• Friedreich’s ataxia

• ferroptosis

External Links

• PubMed

• KEGG Pathways