Alternative splicing generates a novel ferroportin isoform with a shorter C-terminal and an intact iron- and hepcidin-binding property

Ferroportin (FPN) is a transmembrane protein and is the only known iron exporter that helps in maintaining iron homeostasis in vertebrates. To maintain stable iron equilibrium in the body, ferroportin works in conjunction with a peptide called hepcidin. In this study, we have identified an alternatively spliced novel isoform of the human SLC40A1 gene, which encodes for the FPN protein and is found to be expressed in different tissues. The novel transcript has an alternate last exon and encodes 31-amino acid long peptide sequence that replaces 104 amino acids at C-terminal in the novel transcript. Molecular modelling and molecular dynamics (MD) simulation studies revealed key structural features of the novel isoform (FPN-N). FPN-N was predicted to have 12 transmembrane domains similar to the reported isoform (FPN), despite being much smaller in size. FPN-N was found to interact with hepcidin, a key regulator of ferroportin activity. Also, the iron-binding sites were retained in the novel isoform as revealed by the MD simulation of FPN-N in bilipid membrane. The novel isoform identified in this study may play important role in iron homeostasis. However, further studies are required to characterize the FPN-N isoform and decipher its role inside the cell.