Related signaling pathways include the HIF-1-alpha transcription factor network and vesicle-mediated transport. Cellular uptake of iron occurs through receptor-mediated endocytosis of the ligand-occupied transferrin receptor into specialized endosomes. Endosomal acidification leads to iron release. The apotransferrin-receptor complex is then returned to the cell surface with the return to neutral pH and concomitant loss of affinity of apotransferrin for its receptor.
The transferrin receptor is necessary for erythrocyte and nervous system development. A second ligand, the heditary hemochromatosis protein HFE, competes with transferrin for binding at an overlapping C-terminal binding site. Positively regulates proliferation of T and B cells through iron uptake. Acts as a lipid sensor that regulates mitochondrial fusion by controlling activation of the JNK pathway. When dietary stearate concentration is low, it promotes activation of JNK pathway, leading to HUWE1-mediated ubiquitination and subsequent degradation of mitofusin MFN2 and inhibition of mitochondrial fusion. At high levels of stearate (C18:0) in the diet, stearoylation of TFRC inhibits activation of the JNK pathway and consequent degradation of mitofusin MFN2.