Drosophila ZIP13 is posttranslationally regulated by iron-mediated stabilization

Drosophila ZIP13 (dZIP13, CG7816/ZIP99C) belongs to the SLC39A family and is connected to iron homeostasis in the fruit fly. In this study, we show that dZIP13 level is strongly regulated by iron. In addition to a mild response to iron at the mRNA level, dZIP13 is strongly regulated at the protein level. This posttranslational regulation by iron also happens when dZIP13 is expressed in the yeast Saccharomyces cerevisiae. Iron functions to stabilize dZIP13. Domain-swapping experiments between dZIP7 (CG10449/ Catsup) and dZIP13 suggest that the N-terminus of dZIP13 is necessary to mediate this iron regulatory process. Phylogenetic sequence comparison and structural modeling reveal potential iron-binding residues, confirmed by in vitro iron binding assays. Mutations of these potential iron binding sites at the N-terminus, as well as a likely iron binding site at the C-terminus of dZIP13, completely abolish the iron-dependent upregulation in the yeast and the fruit fly. Iron responsiveness of dZIP13 is consistent with its key role in iron homeostasis. We speculate that this process of dZIP13 regulation, and that of IRE/IRP-controlled ferritin production, work together to better cope with iron repletion in the fly.