Induction of Nramp2 in activated mouse macrophages is dissociated from regulation of the Nramp1, classical inflammatory genes, and genes involved in iron metabolism.

Nramp2 is a widely expressed metal-ion transporter that is involved in dietary iron absorption in the duodenum and iron uptake from transferrin in peripheral tissues. Nramp1 is a related gene involved in regulation of host pathogen interaction. Nramp2 has at least two alternatively spliced isoforms, one of which contains an iron-responsive element in its 3'-untranslated region. In this study, we investigated the regulation of both isoforms of Nramp2 in activated primary macrophages from mouse strains with wild-type (Bcg(r)) or mutant (Bcg(s)) alleles. The Nramp2-IRE and/or -nonIRE transcripts were up-regulated in all mouse strains analyzed after treatment with interferon-gamma and lipopolysaccharide. cDNA microarray analysis revealed that Nramp2 regulation is controlled discordantly from other iron-regulated genes and classical macrophage-activation genes in different mouse strains. We suggest that Nramp2 is regulated independently of known iron-responsive genes in macrophages, and its function in host defense is unrelated to Nramp1.