Human SLC11A2 (Natural resistance-associated macrophage protein 2) ELISA Kit

Background: Divalent metal-ion transporter 1 (DMT1) may transport copper, but studies to date on this topic have been equivocal. Previously, an ex vivo experiment showed that intestinal copper transport was impaired in Dmt1-mutant Belgrade rats. Objective: In this study, we tested the hypothesis that intestinal DMT1 transports copper in vivo. Methods: Intestine-specific Dmt1 knockout (Dmt1(int/int)) mice and normal (control) littermates (Dmt1(fl/fl)) were used. In study 1, intestinal copper absorption was assessed in 7-wk-old mice of both sexes and genotypes by oral-intragastric gavage of Cu-64 under normal and iron-deficiency anemia (IDA) conditions. In study 2, both sexes and genotypes of 8-wk-old mice were fed diets with adequate iron concentrations [72 parts per million (ppm)] plus adequate (9 ppm) or excessive (183 ppm) copper concentrations for 4 wk. Iron-and copper-related physiologic variables were subsequently assessed. Results: Study 1 showed that intestinal copper transport was enhanced in normal (similar to 11% increase in males, 35% in females) and anemic (similar to 42% increase in males, 35% in females) Dmt1(int/int) mice. Study 2 showed that, with adequate copper intakes, serum ceruloplasmin (Cp) activity was decreased (by similar to 29% in males and 20% in females) and spleens were enlarged (by 3-fold in both sexes) in Dmt1(int/int) mice. Higher dietary copper increased hepatic copper concentrations (by similar to 3.3-fold in males and 1.5-fold in females), restored serum Cp activity, and mitigated the noted splenomegaly in Dmt1(int/int) mice. Conclusions: Copper homeostasis was disrupted in Dmt1(int/int) mice, particularly during IDA, despite the noted increases in intestinal copper transport. This was exemplified by the fact that extra dietary copper was required to restore serum Cp activity (a biomarker of copper status) and reduce the severity of the noted splenomegaly (which could reflect changes in erythropoietic demand) in Dmt1(int/int) mice. Collectively, these observations show that intestinal DMT1 is essential for the assimilation of sufficient quantities of dietary copper to maintain systemic copper homeostasis during IDA.

TRPML1 ( mucolipin 1, also known as MCOLN1) is predicted to be an intracellular late endosomal and lysosomal ion channel protein that belongs to the mucolipin subfamily of transient receptor potential ( TRP) proteins(1-3). Mutations in the human TRPML1 gene cause mucolipidosis type IV disease ( ML4)4,5.ML4 patients have motor impairment, mental retardation, retinal degeneration and iron- deficiency anaemia. Because aberrant iron metabolism may cause neural and retinal degeneration(6,7), it may be a primary cause of ML4 phenotypes. In most mammalian cells, release of iron from endosomes and lysosomes after iron uptake by endocytosis of Fe(3+)- bound transferrin receptors(6), or after lysosomal degradation of ferritin - iron complexes and autophagic ingestion of iron-containing macromolecules(6,8), is the chief source of cellular iron. The divalent metal transporter protein DMT1 ( also known as SLC11A2) is the only endosomal Fe(2+) transporter known at present and it is highly expressed in erythroid precursors(6,9). Genetic studies, however, suggest the existence of a DMT1-independent endosomal and lysosomal Fe(2+) transport protein(9). By measuring radiolabelled iron uptake, by monitoring the levels of cytosolic and intralysosomal iron and by directly patch- clamping the late endosomal and lysosomal membrane, here we show that TRPML1 functions as a Fe(2+) permeable channel in late endosomes and lysosomes. ML4 mutations are shown to impair the ability of TRPML1 to permeate Fe(2+) at varying degrees, which correlate well with the disease severity. A comparison of TRPML1(-/-) ML4 and control human skin fibroblasts showed a reduction in cytosolic Fe(2+) levels, an increase in intralysosomal Fe(2+) levels and an accumulation of lipofuscin- like molecules in TRPML1(-/-) cells. We propose that TRPML1 mediates a mechanism by which Fe(2+) is released from late endosomes and lysosomes. Our results indicate that impaired iron transportmay contribute to both haematological and degenerative symptoms of ML4 patients.