Transferrin Receptor 1 (TFRC)

Transferrin Receptor 1 (TFRC)

<div class="infobox">
<table>
<tr><td><strong>Gene</strong></td><td>TFRC</td></tr>
<tr><td><strong>UniProt</strong></td><td>[P02786](https://www.uniprot.org/uniprot/P02786)</td></tr>
<tr><td><strong>Molecular Weight</strong></td><td>84-90 kDa (monomer), 180 kDa (dimer)</td></tr>
<tr><td><strong>Subcellular Localization</strong></td><td>Plasma membrane, Endosomes</td></tr>
<tr><td><strong>PDB Structures</strong></td><td>[1SUV](https://www.rcsb.org/structure/1SUV), [1DE4](https://www.rcsb.org/structure/1DE4)</td></tr>
<tr><td><strong>Aliases</strong></td><td>TfR, TfR1, CD71, p90</td></tr>
</table>
</div>

Overview

Transferrin Receptor 1 (TFRC, also known as TfR, TfR1, or CD71) is a transmembrane glycoprotein that mediates cellular iron uptake by binding and internalizing iron-loaded transferrin. As the primary gateway for iron entry into most cells, TFRC plays a critical role in regulating iron homeostasis and is increasingly recognized for its involvement in neurodegenerative diseases characterized by iron dysregulation.[@gomme2005]

Structure and Domains

TFRC is a type II transmembrane protein that functions as a homodimer:[@cheng2004]

Domain organization:

• Cytoplasmic domain (61 residues): Contains the YTRF internalization motif for clathrin-mediated endocytosis
• Transmembrane domain (26 residues): Single alpha-helix anchoring the receptor
• Extracellular domain (672 residues): Binds transferrin with high affinity
• Dimerization interface: The functional receptor is a disulfide-linked homodimer

Transferrin Receptor 1 (TFRC)

<div class="infobox">
<table>
<tr><td><strong>Gene</strong></td><td>TFRC</td></tr>
<tr><td><strong>UniProt</strong></td><td>[P02786](https://www.uniprot.org/uniprot/P02786)</td></tr>
<tr><td><strong>Molecular Weight</strong></td><td>84-90 kDa (monomer), 180 kDa (dimer)</td></tr>
<tr><td><strong>Subcellular Localization</strong></td><td>Plasma membrane, Endosomes</td></tr>
<tr><td><strong>PDB Structures</strong></td><td>[1SUV](https://www.rcsb.org/structure/1SUV), [1DE4](https://www.rcsb.org/structure/1DE4)</td></tr>
<tr><td><strong>Aliases</strong></td><td>TfR, TfR1, CD71, p90</td></tr>
</table>
</div>

Overview

Transferrin Receptor 1 (TFRC, also known as TfR, TfR1, or CD71) is a transmembrane glycoprotein that mediates cellular iron uptake by binding and internalizing iron-loaded transferrin. As the primary gateway for iron entry into most cells, TFRC plays a critical role in regulating iron homeostasis and is increasingly recognized for its involvement in neurodegenerative diseases characterized by iron dysregulation.[@gomme2005]

Structure and Domains

TFRC is a type II transmembrane protein that functions as a homodimer:[@cheng2004]

Domain organization:

• Cytoplasmic domain (61 residues): Contains the YTRF internalization motif for clathrin-mediated endocytosis
• Transmembrane domain (26 residues): Single alpha-helix anchoring the receptor
• Extracellular domain (672 residues): Binds transferrin with high affinity
• Dimerization interface: The functional receptor is a disulfide-linked homodimer

• Protease-like domain: Structurally similar to carboxypeptidases
• Helical domain: Contains the transferrin binding site
• Apical domain: Modulates transferrin binding affinity

Normal Function

TFRC is the primary mechanism for cellular iron acquisition:[@richardson1997]

• Holo-transferrin (iron-loaded) binds to TFRC at the cell surface
• The TFRC-transferrin complex is internalized via clathrin-mediated endocytosis
• Endosomal acidification (pH ~5.5) releases iron from transferrin
• Iron is reduced by STEAP3 and exported to cytosol via DMT1
• Apo-transferrin remains bound and is recycled to the surface

• TFRC expression is regulated by iron-responsive elements (IREs) in its 3' UTR
• Under low iron, IRP proteins bind IREs to stabilize TFRC mRNA
• Under high iron, IRPs dissociate, leading to mRNA degradation

• TFRC is highly expressed in rapidly dividing cells
• Required for DNA synthesis and cell growth
• Upregulated in many cancers

Role in Neurodegeneration

Iron Accumulation and Neurodegeneration

TFRC-mediated iron uptake is implicated in several neurodegenerative diseases:[^4]

Parkinson's Disease:

• TFRC expression is elevated in the substantia nigra of PD patients
• Dopaminergic [neurons](/entities/neurons) show increased iron accumulation via TFRC
• Iron promotes [α-synuclein](/proteins/alpha-synuclein) aggregation and oxidative stress
• TFRC polymorphisms are associated with PD risk[@mochizuki2021]

• TFRC expression is altered in AD brain, particularly in neurons with neurofibrillary tangles
• [Aβ](/proteins/amyloid-beta) can interact with TFRC to modulate iron uptake
• Iron accumulates in amyloid plaques
• The [APOE](/proteins/apoe) ε4 allele is associated with altered iron metabolism via TFRC[@ayton2020]

• Several NBIA disorders involve TFRC-mediated iron uptake dysregulation
• Aceruloplasminemia results in increased TFRC expression
• Friedreich's ataxia shows altered TFRC regulation

Molecular Mechanisms

Iron-Induced Toxicity:
TFRC ↑ → Iron uptake ↑ → Fenton chemistry → ROS ↑ → Lipid peroxidation → Cell death

α-Synuclein Interaction:

• α-Synuclein can bind to TFRC and affect its internalization
• Iron promotes α-synuclein aggregation
• TFRC upregulation creates a feed-forward loop of toxicity[@davies2021]

• Hypotransferrinemia increases TFRC expression
• CSF transferrin saturation is altered in AD and PD

Therapeutic Targeting

Iron Chelation

Targeting TFRC-mediated iron uptake for neuroprotection:[@devos2014]

| Strategy | Mechanism | Status |
|----------|-----------|--------|
| Deferiprone | Chelates labile iron, crosses [BBB](/entities/blood-brain-barrier) | Phase II/III trials (PD) |
| Deferoxamine | Iron chelation, limited BBB penetration | Preclinical |
| Deferasirox | Oral chelator | Preclinical |
| Ferritin-based chelators | Targeted delivery | Research |

TFRC Modulation

• Antisense oligonucleotides: Reduce TFRC expression
• Small molecule inhibitors: Block transferrin binding
• Monoclonal antibodies: Target TFRC for imaging or therapy

Challenges

• Systemic TFRC inhibition causes anemia
• Brain-specific delivery required
• Balance between iron deficiency and iron overload

Protein Interactions

| Interacting Partner | Function | Relevance |
|---------------------|----------|-----------|
| Transferrin | Iron transport protein | Primary ligand |
| DMT1 | Endosomal iron exporter | Sequential transport |
| HFE | Iron regulation | Competitive binding |
| IRP1/IRP2 | Post-transcriptional regulation | mRNA stability |
| Clathrin | Endocytosis | Receptor internalization |

Key Publications

See Also

• [Ferritin Heavy Chain](/proteins/ferritin-h)
• [Ceruloplasmin](/proteins/ceruloplasmin)
• [DMT1](/proteins/dmt1)
• [Ferroportin](/proteins/ferroportin)
• [Iron Metabolism in Neurodegeneration](/mechanisms/iron-metabolism-neurodegeneration)
• [Ferroptosis](/mechanisms/ferroptosis)

References

Related Hypotheses

From the [SciDEX Exchange](/exchange) — scored by multi-agent debate

• [Blood-Brain Barrier SPM Shuttle System](/hypothesis/h-959a4677) — <span style="color:#81c784;font-weight:600">0.75</span> · Target: TFRC