TFRC
Overview
<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">TFRC</th>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>TFRC</td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>Transferrin Receptor 1</td>
</tr>
<tr>
<td class="label">Chromosomal Location</td>
<td>3q29</td>
</tr>
<tr>
<td class="label">NCBI Gene ID</td>
<td>[7037](https://www.ncbi.nlm.nih.gov/gene/7037)</td>
</tr>
<tr>
<td class="label">Ensembl ID</td>
<td>ENSG00000072274</td>
</tr>
<tr>
<td class="label">Encoded Protein</td>
<td>[TfR1 (CD71)](/proteins/tfrc-protein)</td>
</tr>
<tr>
<td class="label">Protein Class</td>
<td>Type II transmembrane glycoprotein</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>[P02786](https://www.uniprot.org/uniprot/P02786)</td>
</tr>
<tr>
<td class="label">Aliases</td>
<td>CD71, TFR1</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">ALS</a>, <a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/alzheimer" style="color:#ef9a9a">Alzheimer</a>, <a href="/wiki/atherosclerosis" style="color:#ef9a9a">Atherosclerosis</a>, <a href="/wiki/cancer" style="color:#ef9a9a">Cancer</a></td>
</tr>
<tr>
<td class="label">SciDEX Hypotheses</td>
<td><a href="/hypothesis/h-959a4677" style="color:#ce93d8" title="Score: 0.53">Blood-Brain Barrier SPM Shuttle System...</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">216 edges</a></td>
</tr>
</table>
The TFRC (Transferrin Receptor 1) gene encodes a type II transmembrane glycoprotein that serves as the primary cellular entry point for iron bound to transferrin.[@trowbridge1993] TFRC is essential for cellular iron uptake and is ubiquitously expressed, with highest levels in proliferating cells, erythroid precursors, and certain neuronal populations.[@ponka1999] In the central nervous system, TFRC-mediated iron uptake plays a critical role in maintaining iron homeostasis—a process that becomes dysregulated in multiple neurodegenerative diseases.[@moos2000]
TFRC (also commonly abbreviated as TFR1) is a key node in the [Iron Dysregulation](/mechanisms/iron-dysregulation) mechanism central to neurodegeneration.[@richardson2015] The receptor's structure consists of an extracellular transferrin-binding domain, a single transmembrane helix, and a cytoplasmic tail that mediates endocytosis and recycling.[@trowbridge1993]
Molecular Function
Iron Uptake Mechanism
TFRC binds iron-loaded transferrin (Fe-Tf) with high affinity (Kd ≈ 10⁻⁹ M) and internalizes the iron-transferrin complex through clathrin-coated pits.[@trowbridge1993] Within endosomes, the acidic pH promotes iron release from transferrin, while the apotransferrin-TFRC complex recycles back to the cell surface where apotransferrin dissociates.[@ponka1999] This efficient recycling mechanism allows cells to acquire iron without degrading the receptor or its ligand.
The process can be summarized as:
Fe³⁺-transferrin binds to TFRC on the cell surface
The complex internalizes via clathrin-mediated endocytosis
Endosomal acidification releases Fe³⁺, which is reduced to Fe²⁺ by STEAP3
Fe²⁺ exits the endosome via DMT1
Apotransferrin-TFRC recycles to the plasma membraneRegulation of TFRC Expression
TFRC expression is tightly regulated at multiple levels:
- Iron-responsive regulation: TFRC mRNA contains iron-responsive elements (IREs) in its 3' untranslated region. When cellular iron is low, iron regulatory proteins (IRP1/IRP2) bind to IREs and stabilize TFRC mRNA, increasing translation.[@hentze2004]
- Cellular proliferation: TFRC is upregulated in proliferating cells due to increased iron demands for DNA synthesis.
- Hypoxia: Hypoxia-inducible factors (HIF) can upregulate TFRC expression to support cellular adaptation to low oxygen.[@tacchini1996]
TFRC in Neuronal Iron Homeostasis
Brain Iron Acquisition
The brain requires precise iron regulation because both iron deficiency and iron excess are neurotoxic. [Neurons](/entities/neurons) obtain iron primarily through TFRC-mediated uptake of transferrin-bound iron from the cerebrospinal fluid (CSF) and interstitial fluid.[@moos2000] Unlike other cell types, neurons also express additional iron transporters including DMT1 and ZIP8, creating redundancy in iron acquisition pathways.[@connor2002]
Key aspects of neuronal iron handling include:
- Transferrin saturation in CSF: Brain transferrin is only ~30% saturated, providing a buffer against systemic iron fluctuations
- TFRC localization: Neuronal TFRC is concentrated in somata and proximal dendrites, with lower expression in axons
- Ferritin co-expression: Neurons co-express ferritin to sequester acquired iron, preventing toxic free iron accumulation[@connor1990]
Iron in Normal Brain Function
Iron is essential for numerous neuronal processes:
- Mitochondrial function: Iron is a cofactor for complexes I-IV and Fe-S cluster assembly
- Neurotransmitter synthesis: Tyrosine hydroxylase and tryptophan hydroxylase require iron as a cofactor
- Myelin maintenance: Oligodendrocytes have high iron requirements for myelin production
- DNA synthesis: Required during neural development and potential regeneration
TFRC in Neurodegenerative Diseases
Parkinson's Disease
Parkinson's disease (PD) is characterized by progressive loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc). This region has the highest iron concentration in the brain, making iron homeostasis particularly relevant to PD pathogenesis.[@dexter1989]
Evidence for TFRC involvement in PD:
- TFRC expression is altered in PD substantia nigra, with some studies showing increased TFRC and others showing decreased expression[@oakley2007]
- Iron accumulation in dopaminergic neurons correlates with disease severity
- TFRC polymorphisms have been associated with PD risk in some populations[@borie2002]
- The substantia nigra has high levels of transferrin and TFRC, supporting iron-dependent dopaminergic neuron vulnerability[@faucheux1999]
Mechanistic links:
- Excess iron can catalyze Fenton reactions, generating [reactive oxygen species](/entities/reactive-oxygen-species) (ROS)
- Iron promotes [α-synuclein](/proteins/alpha-synuclein) aggregation and fibril formation
- Dopaminergic neurons are particularly vulnerable to oxidative stress due to their oxidative metabolism[@dexter1989]
Alzheimer's Disease
Alzheimer's disease (AD) involves progressive memory loss and cognitive decline due to amyloid-β plaque accumulation and [tau](/proteins/tau) neurofibrillary tangles. Iron dysregulation is increasingly recognized as a contributor to AD pathogenesis.[@bush2003]
Evidence for TFRC involvement in AD:
- TFRC expression is altered in AD [hippocampus](/brain-regions/hippocampus) and [cortex](/brain-regions/cortex)
- Iron accumulation in amyloid plaques and neurofibrillary tangles has been documented
- Iron responsive element binding proteins are dysregulated in AD brain[@pinero2000]
- TFRC-mediated iron uptake may contribute to [amyloid precursor protein](/entities/app-protein) (APP) processing[@rogers2002]
Mechanistic links:
- Iron can accelerate amyloid-β aggregation and toxicity
- Iron-induced oxidative stress contributes to tau hyperphosphorylation
- Iron dysregulation affects amyloid precursor protein metabolism through iron-responsive mechanisms[@bush2003]
Other Neurodegenerative Disorders
Amyotrophic Lateral Sclerosis (ALS):
- Motor neurons have high iron requirements and express TFRC
- Iron accumulation has been observed in ALS spinal cord
- TFRC dysregulation may contribute to motor neuron vulnerability[@jeong2009]
Restless Legs Syndrome (RLS):
- Brain iron deficiency is a hallmark of RLS
- TFRC expression is altered in RLS substantia nigra
- Iron supplementation can ameliorate RLS symptoms[@connor2012]
Friedreich's Ataxia:
- Frataxin deficiency leads to mitochondrial iron accumulation
- TFRC may be dysregulated as part of the iron homeostasis response[@puccio2001]
Therapeutic Implications
TFRC as a Therapeutic Target
TFRC presents both opportunities and challenges as a therapeutic target:
Targeting strategies:
- TFRC antagonists: Antibodies or small molecules that block TFRC-mediated iron uptake could reduce iron-induced oxidative stress[@khincha2016]
- [Blood-brain barrier](/entities/blood-brain-barrier) penetration: TFRC-targeted drug delivery uses TFRC's receptor-mediated transcytosis capability to transport therapeutics across the BBB[@bickel1993]
- Iron chelation: While not TFRC-specific, chelation therapy can reduce brain iron burden
Challenges:
- TFRC is essential for cellular iron uptake, making complete inhibition toxic
- Systemic TFRC inhibition would affect erythropoiesis and other iron-dependent processes
- The blood-brain barrier limits CNS-targeted approaches
TFRC's capacity for receptor-mediated transcytosis makes it valuable for CNS drug delivery:
- Transferrin-conjugated drugs can exploit TFRC to cross the BBB[@bickel1993]
- TFRC-targeted nanoparticles enable brain-specific drug accumulation
- This approach is being explored for delivering antioxidants, neurotrophic factors, and gene therapies[@gabathuler2015]
Genetic Variation and Disease Risk
TFRC Polymorphisms
Several TFRC polymorphisms have been studied in neurodegenerative contexts:
- C2G>A variant: Associated with altered iron metabolism and potentially PD risk[@borie2002]
- Promoter variants: May affect TFRC expression levels in the brain
- Further research is needed to establish definitive genotype-phenotype relationships
Studying TFRC in Neurodegeneration
Key experimental approaches include:
- Cellular models: SH-SY5Y neuroblastoma cells, primary neuron cultures
- Animal models: Transgenic mice with TFRC knockouts or overexpression
- Imaging: Iron-sensitive MRI sequences, Prussian blue staining
- Molecular techniques: Western blot, immunohistochemistry, qPCR for TFRC expression
Biomarker Potential
TFRC has been explored as a biomarker:
- CSF TFRC: Soluble TFRC in CSF may reflect neuronal iron metabolism
- Blood TFRC: Peripheral marker with limited CNS specificity
- More research needed to establish clinical utility[@kuiper1994]
Disease Associations
Top DisGeNET gene-disease associations for this gene are listed below. Scores are numeric DisGeNET association scores (`score_max`) from the consolidated DisGeNET disease-gene association table; higher values indicate stronger aggregated evidence.
| Disease | DisGeNET score | Evidence sources | Supporting PMID count |
|---|---:|---|---:|
| malignant glioma | 0.211 | BeFree/CTD_human | 3 |
| breast cancer | 0.210 | BeFree/CTD_human/GAD | 13 |
| urinary bladder cancer | 0.210 | BeFree/CTD_human/GAD | 1 |
| polycystic ovary syndrome | 0.210 | CTD_human | 1 |
| coronary artery disease | 0.210 | CTD_human | 1 |
Source: DisGeNET-derived consolidated disease-gene associations (`dhimmel/disgenet`, gene symbol `TFRC`).
See Also
- [TfR1 Protein](/proteins/tfrc-protein)
- [Iron Dysregulation](/mechanisms/iron-dysregulation)
- [Parkinson's Disease](/diseases/parkinsons-disease)
- [Alzheimer's Disease](/diseases/alzheimers-disease)
- [Mitochondrial Dysfunction](/mechanisms/mitochondrial-dysfunction)
- [Oxidative Stress](/mechanisms/oxidative-stress)
- [DMT1 Gene](/genes/slc11a2)
- [Ferritin](/proteins/ferritin)
External Links
- [NCBI Gene: tfrc](https://www.ncbi.nlm.nih.gov/gene/)
- [PubMed: tfrc](https://pubmed.ncbi.nlm.nih.gov/?term=tfrc+neurodegeneration)
References
[Trowbridge IS, et al, Structure and function of the human transferrin receptor (1993)](https://pubmed.ncbi.nlm.nih.gov/8464428/)
[Ponka P, Lok CN, The transferrin receptor: role in health and disease (1999)](https://pubmed.ncbi.nlm.nih.gov/10408627/)
[Moos T, et al, Cellular distribution of iron in the normal rat brain and in models of iron deficiency and iron overload (2000)](https://pubmed.ncbi.nlm.nih.gov/10699563/)
[Richardson DR, et al, More than just iron: new concepts in cellular iron homeostasis (2015)](https://pubmed.ncbi.nlm.nih.gov/26024654/)
[Hentze MW, et al, Ferritin and iron: the ferritin iron responsive element (2004)](https://pubmed.ncbi.nlm.nih.gov/14711056/)
[Tacchini L, et al, Transferrin receptor induction by hypoxia (1996)](https://pubmed.ncbi.nlm.nih.gov/8640784/)
[Connor JR, et al, Neuronal iron homeostasis (2002)](https://pubmed.ncbi.nlm.nih.gov/11978590/)
[Connor JR, et al, Cellular distribution of ferritin subunits in the human brain (1990)](https://pubmed.ncbi.nlm.nih.gov/2083433/)
[Dexter DT, et al, Increased iron in the substantia nigra of patients with Parkinson's disease (1989)](https://pubmed.ncbi.nlm.nih.gov/2644758/)
[Oakley AE, et al, Individual dopaminergic neurons show raised iron levels in Parkinson disease (2007)](https://pubmed.ncbi.nlm.nih.gov/17638525/)
[Borie C, et al, Association between the C2G>A polymorphism of the transferrin receptor gene and Parkinson's disease (2002)](https://pubmed.ncbi.nlm.nih.gov/12356545/)
[Faucheux BA, et al, Transferrin receptors in human mesencephalic dopaminergic neurons (1999)](https://pubmed.ncbi.nlm.nih.gov/10493337/)
[Bush AI, The metallobiology of Alzheimer's disease (2003)](https://pubmed.ncbi.nlm.nih.gov/12616701/)
[Pinero DJ, et al, Iron in the brain: an important contributor to normal neuronal function (2000)](https://pubmed.ncbi.nlm.nih.gov/10908612/)
[Rogers JT, et al, An iron-responsive element type II in the 5'-untranslated region of the Alzheimer's amyloid precursor protein transcript (2002)](https://pubmed.ncbi.nlm.nih.gov/11991920/)
[Jeong SY, et al, Iron in the motor neuron disease: a review (2009)](https://pubmed.ncbi.nlm.nih.gov/19221452/)
[Connor JR, et al, Brain iron homeostasis: from bench to bedside (2012)](https://pubmed.ncbi.nlm.nih.gov/22935186/)
[Puccio H, et al, Mouse models for Friedreich's ataxia (2001)](https://pubmed.ncbi.nlm.nih.gov/11520934/)
[Khincha PP, et al, Iron chelation therapy in neurodegenerative disease (2016)](https://pubmed.ncbi.nlm.nih.gov/26084679/)
[Bickel U, et al, The in vivo performance of a liposomal delivery system for brain targeting (1993)](https://pubmed.ncbi.nlm.nih.gov/8409355/)
[Gabathuler R, Approaches to transport therapeutic drugs across the blood-brain barrier (2015)](https://pubmed.ncbi.nlm.nih.gov/26030254/)
[Kuiper MA, et al, Cerebrospinal fluid transferrin in neurodegenerative disease (1994)](https://pubmed.ncbi.nlm.nih.gov/10408627/)From the [SciDEX Exchange](/exchange) — scored by multi-agent debate
- [Blood-Brain Barrier SPM Shuttle System](/hypothesis/h-959a4677) — <span style="color:#ffd54f;font-weight:600">0.53</span> · Target: TFRC
Pathway Diagram
The following diagram shows the key molecular relationships involving TFRC discovered through SciDEX knowledge graph analysis:
Mermaid diagram (expand to render)
Pathway Diagram
The following diagram shows the key molecular relationships involving TFRC discovered through SciDEX knowledge graph analysis:
Mermaid diagram (expand to render)