DMT1, a physiologically relevant apical Cu1+ transporter of intestinal cells

Abstract

Despite important advances in the under-standing of copper secretion and excretion, the molecular components of intestinal copper absorption remain a mys-tery. DMT1, also known as Nramp2 and DCT1, is the trans-porter responsible for intestinal iron uptake. Electrophysio-logical evidence suggests that DMT1 can also be a copper transporter. Thus we examined the potential role of DMT1 as a copper transporter in intestinal Caco-2 cells. Treatment of cells with a DMT1 antisense oligonucleotide resulted in 80 and 48% inhibition of iron and copper uptake, respectively. Cells incorporated considerable amounts of copper as Cu1+, whereas Cu2+ transport was about 10-fold lower. Cu1+ inhibited apical Fe2+ transport. Fe2+, but not Fe3+, effectively inhibited Cu1+ uptake. The iron content of the cells influ enced both copper and iron uptake. Cells with low iron content transported fourfold more iron and threefold more copper than cells with high iron content. These results demonstrate that DMT1 is a