Cloning and functional characterization of the Anopheles albimanus DMT1/NRAMP homolog: Implications in iron metabolism in mosquitoes

In addition to its wide role in metabolism, iron in insects has been implicated in vitellogenesis and the immune response. The NRAMP family comprises a well-conserved family of divalent cation transporters in metazoans. To gain insight on the role of NRAMP in Anopheles albimanus, we cloned a cDNA encoding a 571-residue protein (AnaNRAMP) with the structural features defining the NRAMP family. AnaNRAMP mRNA induced 59Fe2+ incorporation when injected into Xenopus oocytes. Western blot analysis revealed that AnaNRAMP is expressed in the head, midgut and at high levels in Malpighian tubules of unfed female mosquito. Upon blood feeding, AnaNRAMP levels were reduced in the midgut whereas they increased in the Malpighian tubules. Using immuno-localization by transmission electron microscopy, AnaNRAMP was localized in the membrane of the intra-cellular concretions or spherites of the Malpighian tubule principal cells. Taken together, our results suggest an important role of AnaNRAMP in iron transport and indicate a role of the mosquito Malpighian tubule as an important organ for iron homeostasis.