1. The Multiple Faces of the Metal Transporter ZIP14 (SLC39A14).
- Author
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Aydemir TB and Cousins RJ
- Subjects
- Adipose Tissue chemistry, Adipose Tissue physiology, Animals, Biological Transport physiology, Bone and Bones chemistry, Bone and Bones physiology, Brain physiology, Cation Transport Proteins analysis, Cation Transport Proteins genetics, Endotoxemia etiology, Endotoxemia metabolism, Interleukin-6 blood, Intestines physiology, Iron blood, Liver metabolism, Liver physiology, Manganese analysis, Manganese blood, Mice, Mice, Knockout, Neoplasms metabolism, Nitric Oxide physiology, Pancreas chemistry, Pancreas physiology, Tissue Distribution, Zinc blood, Zinc metabolism, Cation Transport Proteins physiology
- Abstract
The SLC39A family of metal transporters was identified through homologies with the Zrt- and Irt-like (ZIP) proteins from yeast and plants. Of all the ZIP transporters, ZIP14 is arguably the most robustly characterized in terms of function at the integrative level. Mice with a global knockout of Zip14 are viable, thus providing the opportunity to conduct physiologic experiments. In mice, Zip14 expression is highly tissue specific, with the greatest abundance in the jejunum > liver > heart > kidney > white adipose tissue > skeletal muscle > spleen > pancreas. A unique feature of Zip14 is its upregulation by proinflammatory conditions, particularly increased interleukin 6 (IL-6) and nitric oxide. The transcription factors AP-1, ATF4, and ATF6α are involved in Zip14 regulation. ZIP14 does not appear to be zinc-regulated. The Zip14 knockout phenotype shows multiple sites of ZIP14 function, including the liver, adipose tissue, brain, pancreas, and bone. A prominent feature of the Zip14 ablation is a reduction in intestinal barrier function and onset of metabolic endotoxemia. Many aspects of the phenotype are accentuated with age and accompany increased circulating IL-6. Studies with 65Zn, 59Fe [nontransferrin-bound iron (NTBI)] and 54Mn show that ZIP14 transports these metals. At a steady state, the plasma concentrations of zinc, NTBI, and manganese are such that zinc ions are the major substrate available for ZIP14 at the cell surface. Upregulation of ZIP14 accounts for the hypozincemia and hepatic zinc accumulation associated with acute inflammation and sepsis and is required for liver regeneration and resistance to endoplasmic reticulum (ER) stress. Zip14 ablation in mice produces a defect in manganese excretion that leads to excess manganese accumulation in the brain that produces characteristics of Parkinsonism.
- Published
- 2018
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