TFRC

Overview

TFRC
Gene Symbol	TFRC
Full Name	Transferrin Receptor 1
Chromosomal Location	3q29
NCBI Gene ID	[7037](https://www.ncbi.nlm.nih.gov/gene/7037)
Ensembl ID	ENSG00000072274
Encoded Protein	[TfR1 (CD71)](/proteins/tfrc-protein)
Protein Class	Type II transmembrane glycoprotein
UniProt ID	[P02786](https://www.uniprot.org/uniprot/P02786)
Aliases	CD71, TFR1
Associated Diseases	ALS, Als, Alzheimer, Atherosclerosis, Cancer
SciDEX Hypotheses	Blood-Brain Barrier SPM Shuttle System...
KG Connections	216 edges

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.^{1Structure and function of the human transferrin receptor1993 · Annu Rev Nutr · PMID 8464428Open reference} TFRC is essential for cellular iron uptake and is ubiquitously expressed, with highest levels in proliferating cells, erythroid precursors, and certain neuronal populations.^{2The transferrin receptor: role in health and disease1999 · Int J Biochem Cell Biol · PMID 10408627Open reference} 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.^{3Cellular distribution of iron in the normal rat brain and in models of iron deficiency and iron overload2000 · J Neurosci Res · PMID 10699563Open reference}

TFRC (also commonly abbreviated as TFR1) is a key node in the Iron Dysregulation mechanism central to neurodegeneration.^{4More than just iron: new concepts in cellular iron homeostasis2015 · Nat Rev Gastroenterol Hepatol · PMID 26024654Open reference} The receptor’s structure consists of an extracellular transferrin-binding domain, a single transmembrane helix, and a cytoplasmic tail that mediates endocytosis and recycling.^{1Structure and function of the human transferrin receptor1993 · Annu Rev Nutr · PMID 8464428Open reference}

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.^{1Structure and function of the human transferrin receptor1993 · Annu Rev Nutr · PMID 8464428Open reference} Within endosomes, the acidic pH promotes iron release from transferrin, while the apotransferrin-TFRC complex recycles back to the cell surface where apotransferrin dissociates.^{2The transferrin receptor: role in health and disease1999 · Int J Biochem Cell Biol · PMID 10408627Open reference} This efficient recycling mechanism allows cells to acquire iron without degrading the receptor or its ligand.

The process can be summarized as:

1. Fe³⁺-transferrin binds to TFRC on the cell surface

2. The complex internalizes via clathrin-mediated endocytosis

3. Endosomal acidification releases Fe³⁺, which is reduced to Fe²⁺ by STEAP3

4. Fe²⁺ exits the endosome via DMT1

5. Apotransferrin-TFRC recycles to the plasma membrane

Regulation 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.^{5Ferritin and iron: the ferritin iron responsive element2004 · Cell · PMID 14711056Open reference}

• 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.^{6Transferrin receptor induction by hypoxia1996 · J Biol Chem · PMID 8640784Open reference}

TFRC in Neuronal Iron Homeostasis

Brain Iron Acquisition

The brain requires precise iron regulation because both iron deficiency and iron excess are neurotoxic. Neurons obtain iron primarily through TFRC-mediated uptake of transferrin-bound iron from the cerebrospinal fluid (CSF) and interstitial fluid.^{3Cellular distribution of iron in the normal rat brain and in models of iron deficiency and iron overload2000 · J Neurosci Res · PMID 10699563Open reference} Unlike other cell types, neurons also express additional iron transporters including DMT1 and ZIP8, creating redundancy in iron acquisition pathways.^{2The transferrin receptor: role in health and disease1999 · Int J Biochem Cell Biol · PMID 10408627Open reference}0

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^{2The transferrin receptor: role in health and disease1999 · Int J Biochem Cell Biol · PMID 10408627Open reference}1

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.^{2The transferrin receptor: role in health and disease1999 · Int J Biochem Cell Biol · PMID 10408627Open reference}2

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^{2The transferrin receptor: role in health and disease1999 · Int J Biochem Cell Biol · PMID 10408627Open reference}3

• Iron accumulation in dopaminergic neurons correlates with disease severity

• TFRC polymorphisms have been associated with PD risk in some populations^{2The transferrin receptor: role in health and disease1999 · Int J Biochem Cell Biol · PMID 10408627Open reference}4

• The substantia nigra has high levels of transferrin and TFRC, supporting iron-dependent dopaminergic neuron vulnerability^{2The transferrin receptor: role in health and disease1999 · Int J Biochem Cell Biol · PMID 10408627Open reference}5

Mechanistic links:

• Excess iron can catalyze Fenton reactions, generating reactive oxygen species (ROS)

• Iron promotes α-synuclein aggregation and fibril formation

• Dopaminergic neurons are particularly vulnerable to oxidative stress due to their oxidative metabolism^{2The transferrin receptor: role in health and disease1999 · Int J Biochem Cell Biol · PMID 10408627Open reference}6

Alzheimer’s Disease

Alzheimer’s disease (AD) involves progressive memory loss and cognitive decline due to amyloid-β plaque accumulation and tau neurofibrillary tangles. Iron dysregulation is increasingly recognized as a contributor to AD pathogenesis.^{2The transferrin receptor: role in health and disease1999 · Int J Biochem Cell Biol · PMID 10408627Open reference}7

Evidence for TFRC involvement in AD:

• TFRC expression is altered in AD hippocampus and cortex

• Iron accumulation in amyloid plaques and neurofibrillary tangles has been documented

• Iron responsive element binding proteins are dysregulated in AD brain^{2The transferrin receptor: role in health and disease1999 · Int J Biochem Cell Biol · PMID 10408627Open reference}8

• TFRC-mediated iron uptake may contribute to amyloid precursor protein (APP) processing^{2The transferrin receptor: role in health and disease1999 · Int J Biochem Cell Biol · PMID 10408627Open reference}9

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^{3Cellular distribution of iron in the normal rat brain and in models of iron deficiency and iron overload2000 · J Neurosci Res · PMID 10699563Open reference}0

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^{3Cellular distribution of iron in the normal rat brain and in models of iron deficiency and iron overload2000 · J Neurosci Res · PMID 10699563Open reference}1

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^{3Cellular distribution of iron in the normal rat brain and in models of iron deficiency and iron overload2000 · J Neurosci Res · PMID 10699563Open reference}2

Friedreich’s Ataxia:

• Frataxin deficiency leads to mitochondrial iron accumulation

• TFRC may be dysregulated as part of the iron homeostasis response^{3Cellular distribution of iron in the normal rat brain and in models of iron deficiency and iron overload2000 · J Neurosci Res · PMID 10699563Open reference}3

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^{3Cellular distribution of iron in the normal rat brain and in models of iron deficiency and iron overload2000 · J Neurosci Res · PMID 10699563Open reference}4

• Blood-brain barrier penetration: TFRC-targeted drug delivery uses TFRC’s receptor-mediated transcytosis capability to transport therapeutics across the BBB^{3Cellular distribution of iron in the normal rat brain and in models of iron deficiency and iron overload2000 · J Neurosci Res · PMID 10699563Open reference}5

• 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-Mediated Drug Delivery

TFRC’s capacity for receptor-mediated transcytosis makes it valuable for CNS drug delivery:

• Transferrin-conjugated drugs can exploit TFRC to cross the BBB^{3Cellular distribution of iron in the normal rat brain and in models of iron deficiency and iron overload2000 · J Neurosci Res · PMID 10699563Open reference}6

• TFRC-targeted nanoparticles enable brain-specific drug accumulation

• This approach is being explored for delivering antioxidants, neurotrophic factors, and gene therapies^{3Cellular distribution of iron in the normal rat brain and in models of iron deficiency and iron overload2000 · J Neurosci Res · PMID 10699563Open reference}7

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^{3Cellular distribution of iron in the normal rat brain and in models of iron deficiency and iron overload2000 · J Neurosci Res · PMID 10699563Open reference}8

• Promoter variants: May affect TFRC expression levels in the brain

• Further research is needed to establish definitive genotype-phenotype relationships

Research Methods and Tools

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^{3Cellular distribution of iron in the normal rat brain and in models of iron deficiency and iron overload2000 · J Neurosci Res · PMID 10699563Open reference}9

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

• Iron Dysregulation

• Parkinson’s Disease

• Alzheimer’s Disease

• Mitochondrial Dysfunction

• Oxidative Stress

• DMT1 Gene

• Ferritin

External Links

• NCBI Gene: tfrc

• PubMed: tfrc