Export of ferritin-bound iron in CD63⁺ vesicles is enhanced by iron. (A) In an iron-poor cell, translation of CD63 as well as ferritin H and L subunits (represented in the figure as ferritin) is inhibited by iron regulatory proteins (IRPs). Iron-containing ferritin in the cell is directed by the cargo receptor NCOA4 to the lysosome for degradation, a process termed ferritinophagy.³ Ferritinophagy liberates iron contained within ferritin, enabling cellular use of iron for essential processes. (B) In an iron-replete cell, IRPs are inactivated, and translation of both CD63 and ferritin subunits is increased. Ferritin associates with NCOA4 and is directed to CD63⁺ vesicles by an unclear mechanism. CD63⁺ vesicles are shown in multivesicular bodies (MVBs) based on work by Truman-Rosentsvit et al² and Brown et al.⁴ Ferritin and its associated iron within CD63⁺ vesicles are ultimately exported out of the cell. Professional illustration by Patrick Lane, ScEYEnce Studios.