Transferrin receptor

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Transferrin receptor (TfR) is a protein on cell surfaces that helps cells take in iron. It does this by binding transferrin, the carrier of iron in the blood, and pulling the transferrin-iron complex into the cell through receptor-mediated endocytosis.

Key points:
- TfR has two main forms: TfR1 and TfR2.
- TfR1: high affinity, found in many cell types; the main route for iron uptake, especially in developing red blood cells.
- TfR2: lower affinity and more limited in where it’s expressed; less involved in iron uptake.
- Some cells may take up transferrin iron by other, less well-understood routes.
- The enzyme GAPDH can influence TfR function and may help switch between delivering iron to the cell and exporting iron.
- Iron levels regulate TfR production:
- When iron is low, iron-responsive proteins bind to an iron-responsive element (IRE) in TfR mRNA, stabilizing it and increasing TfR production.
- When iron is high, this binding decreases, lowering TfR levels and reducing iron uptake.
This regulation helps maintain cellular iron balance.