The selenoprotein P/ApoER2 axis facilitates selenium accumulation in selenoprotein P-accepting cells and confers prolonged resistance to ferroptosis

The essential trace element selenium (Se) plays a significant role in redox homeostasis, while Se is very reactive and has a potent toxicity. Understanding the molecular machinery that supports Se metabolism is important for the both physiological and pathophysiological context. Incorporated Se is translated/transformed in the liver into selenoprotein P (SeP; encoded by Selenop), an extracellular Se carrier protein that effectively transports Se to the cells via the binding to its receptor apolipoprotein E receptor 2 (ApoER2), which is taken up by cells. The present study shows that SeP is a source of Se that accumulates intracellularly and can be utilized for prolonged periods under Se-deficient conditions. In cultured cells (RD and SH-SY5Y), glutathione peroxidase (GPX) expression induced by Se supply via the SeP/ApoER2 pathway was maintained longer during Se deficiency than inorganic Se, which was promoted by ApoER2 overexpression. SeP-deficient mice showed a faster decline in brain Se levels when fed a Se-deficient diet. Preserved GPX expression induced by this SeP/ApoER2 axis contributed to oxidative stress and ferroptosis resistance, suggesting that this redundant Se metabolism contributes to prolonged Se utilization and cytoprotection.