STEAP3 (Six-Transmembrane Epithelial Antigen of Prostate 3) encodes a metalloreductase that facilitates iron and copper uptake into cells. It is primarily localized to the endosomal membrane and functions as an ferric reductase, converting Fe3+ to Fe2+ for transport by DMT1 (SLC11A2).
STEAP3 plays critical roles in:
- Iron reduction: Converts Fe3+ to Fe2+ for cellular uptake
- Copper metabolism: Also reduces Cu2+ to Cu1+ for transport
- Erythropoiesis: Essential for red blood cell production
- Cellular iron homeostasis: Regulates iron uptake into various cell types
- Mitochondrial iron: Participates in mitochondrial iron metabolism
STEAP3 is part of the STEAP family (STEAP1-4), which are six-transmembrane proteins with metalloreductase activity. It forms a complex with DMT1 and other iron transport proteins in endosomes.
STEAP3 mutations cause severe iron deficiency anemia:
- Microcytic anemia: Small, pale red blood cells
- Iron deficiency: Low serum iron and ferritin
- Hypochromia: Reduced hemoglobin content in RBCs
- Growth retardation: In severe childhood cases
- Neurodevelopmental delays: Cognitive impairment in children
The disease mechanism involves:
- Impaired intestinal iron absorption
- Reduced iron delivery to bone marrow
- Defective erythropoiesis
- Secondary neurological effects
Iron dysregulation is strongly implicated in neurodegenerative diseases:
- Parkinson's disease: Iron accumulation in substantia nigra
- Alzheimer's disease: Iron accumulation in amyloid plaques and neurons
- Friedreich's ataxia: Iron-sulfur cluster deficiency
- Neuroferritinopathy: Brain iron accumulation disorder
STEAP3 dysfunction may contribute to:
- Oxidative stress: Iron-catalyzed ROS generation
- Mitochondrial dysfunction: Impaired Fe-S cluster synthesis
- Protein aggregation: Iron dysregulation affects aggregation pathways
- Neuronal death: Iron-induced apoptosis
STEAP3 is expressed in:
- Bone marrow (highest in erythroid precursors)
- Liver (hepatocytes)
- Kidney
- Duodenum (intestinal epithelial cells)
- Brain (neurons, glial cells)
- Spleen
In the brain, STEAP3 is expressed in:
The expression in substantia nigra is relevant to Parkinson's disease iron accumulation.
- Ohgami et al., STEAP3 is a ferric reductase (2005)
- Finazzi et al., STEAP3 mutations and iron deficiency (2010)
- Ward & Kaplan, Iron metabolism in neurodegeneration (2012)
- Sarkar et al., STEAP3: Iron Metabolism and Cellular Homeostasis (2020) (2020))
- Ohgami et al., STEAP Family Proteins in Iron and Copper Metabolism (2019) (2019))
- Wang et al., STEAP3 in Neurodegeneration (2021) (2021))
- Chen et al., Iron Dysregulation in Alzheimer Disease (2020) (2020))
- Gupta et al., Cellular Iron Metabolism and Disease (2021) (2021))