Ectopic expression of Nramp1 in COS-1 cells modulates iron accumulation.

Nramp1 (natural resistance-associated macrophage protein) controls innate immunity and encodes a transporter of unknown function. Here we describe an antibody to Nramp1 displaying immunoreactivity towards a mature heavily glycosylated polypeptide of 90-100 kDa and a precursor form of 45 kDa in macrophages. Ectopic expression of the Nramp1 cDNA in COS-1 cells demonstrates that Nramp1 modulates cellular iron levels following loading with low molecular weight iron chelates. Surprisingly, Nramp1 does not enhance iron uptake, but expression is associated with reduced cellular iron loads. We propose Nramp1 may play a role in a salvage pathway of iron recycling.