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. Author manuscript; available in PMC: 2022 Jul 1.
Published in final edited form as: Semin Hematol. 2021 Jun 27;58(3):161–174. doi: 10.1053/j.seminhematol.2021.06.001

Figure 3. Physiological functions of FPN and its mRNA isoforms in systemic iron homeostasis.

Figure 3.

FPN exports iron into the blood circulation, and it is highly expressed in enterocytes, where it enables iron absorption, in erythroblasts and macrophages, where it functions in iron recycling, and in hepatocytes for iron storage. While FPN1a isoform is ubiquitously expressed, FPN1b isoform is selectively expressed in enterocytes and erythroblasts. The existence of these two FPN isoforms enable these two cell types to express FPN protein under iron deficiency, thereby providing iron to the circulating blood where it becomes available to essential cells and tissues. FPN is also abundant in mature RBCs where it exerts a protective effect against iron-induced oxidative stress. See the main text for detail.