Molecular and cellular mechanisms underlying iron transport deficiency in microcytic anemia

• Published in: Blood Vol. 104; no. 5; pp. 1526 - 1533
• Main Authors: Touret, Nicolas, Martin-Orozco, Natalia, Paroutis, Paul, Furuya, Wendy, Lam-Yuk-Tseung, Steven, Forbes, John, Gros, Philippe, Grinstein, Sergio
• Format: Journal Article
• Language: English
• Published: Washington, DC Elsevier Inc 01.09.2004; The Americain Society of Hematology
• Subjects: Anemia - genetics; Anemia - metabolism; Anemias. Hemoglobinopathies; Animals; Biological and medical sciences; Biological Transport - physiology; Cation Transport Proteins - chemistry; Cation Transport Proteins - genetics; Cation Transport Proteins - metabolism; Cell Membrane - metabolism; CHO Cells; Cricetinae; Cysteine Endopeptidases - metabolism; Diseases of red blood cells; Epithelial Cells - cytology; Epithelial Cells - metabolism; Hematologic and hematopoietic diseases; Iron - metabolism; Iron-Binding Proteins - chemistry; Iron-Binding Proteins - genetics; Iron-Binding Proteins - metabolism; LLC-PK1 Cells; Lysosomes - metabolism; Medical sciences; Multienzyme Complexes - metabolism; Mutagenesis; Point Mutation; Proteasome Endopeptidase Complex; Protein Folding; Swine; Human; Pathogenesis; Iron deficiency anemia; Biological transport; Metabolic diseases; Hemopathy; Iron; Inorganic element; Gene; Genetics; Mutation; Divalent transporter 1; Sideropenia
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2004-02-0731

A mutation of the iron transporter Nramp2 (DMT1, Slc11a2) causes microcytic anemia inmkmice and inBelgraderats by impairing iron absorption in the duodenum and in erythroid cells, causing severe iron deficiency. BothmkandBelgradeanimals display a glycine-to-arginine substitution at position 185 (G185R) in the fourth predicted transmembrane domain of Nramp2. To study the molecular basis for the loss of function of Nramp2G185R, we established cell lines stably expressing extracellularly tagged versions of wild-type (WT) or mutated transporters. Like WT Nramp2, the G185R mutant was able to reach the plasmalemma and endosomal compartments, but with reduced efficiency. Instead, a large fraction of Nramp2G185Rwas detected in the endoplasmic reticulum, where it was unstable and was rapidly degraded by a proteasome-dependent mechanism. Moreover, the stability of the mutant protein that reached the plasma membrane was greatly reduced, further diminishing its surface density at steady state. Last, the specific metal transport activity of plasmalemmal Nramp2G185Rwas found to be significantly depressed, compared with its WT counterpart. Thus, a singlepoint mutation results in multiple biosynthetic and functional defects that combine to produce the impaired iron deficiency that results in microcytic anemia.