Ferritin, cellular iron storage and regulation.

Ferritin is considered the major iron storage protein which maintains a large iron core in its cavity and has ferroxidase activity. There are many types of ferritin particularly in prokaryotes that include the canonical 24-mer FTN molecules, the heme-containing BFR, the smaller 12-mer DPS and the newly recognized EncFtn of encapsulin that forms a very large iron storage compartment. Recent studies show that ferritin function is more dynamic than previous depicted and new mechanisms of ferritin iron recycling are emerging. They participate to the regulation of cellular iron homeostasis as those of ferritin biosynthesis, cooperating also with the iron-dependent mechanism of cellular iron secretion. Some of these basic processes are in common between unicellular and animal cells, and this review aims at discussing the findings on the connections between iron storage, cellular iron regulation and ferritin iron recycling that have been explored in unicellular organisms and in animals.