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Intestinal and placental zinc transport pathways

Lookup NU author(s): Professor Dianne Ford

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Abstract

Mammalian members of the cation diffusion facilitator (CDF) and zrt-, irt-like protein (ZIP) families of Zn transporters, initially identified in Saccharomyces cerevisiae and Arabidopsis thalania, have been cloned during the last 8 years and have been classified as families SLC30 and SLC39 respectively. The cloning of human Zn transporters ZnT-like transporter 1 (hZTL1)/ZnT5 (SLC30A5) and hZIP4 (SLC39A4) were major advances in the understanding of the molecular mechanisms of dietary Zn absorption. Both transporters are localised at the enterocyte apical membrane and are, therefore, potentially of fundamental importance in dietary Zn uptake. hZTL1 mediates Zn uptake when expressed in Xenopus laevis oocytes and hZIP4 is mutated in most cases of the inherited Zn deficiency disease acrodermatitis enteropathica. Localisation of hZTL1/ZnT5 at the apical membrane of the placental syncytiotrophoblast indicates a fundamental role in the transfer of Zn to the foetus. Observations in rodent models indicate that in the intestine increased Zn availability increases expression of Slc30 Zn transporters. Human intestinal Caco-2 cells show a similar response to increasing the Zn2+ concentration of the nutrient medium in relation to the expression of mRNA corresponding to several Zn transporters and that of ZnT1 (SLC30A1) and hZTL1/ZnT5 proteins. In the human placental cell line JAR, however, expression at the mRNA level of a number of Zn transporters is not modified by Zn availability, whilst ZnT1 and hZTL1/ZnT5 proteins are reduced under Zn-supplemented conditions. These differences between Caco-2 and JAR cells in Zn transporter gene responses to Zn supply may reflect the different extracellular Zn concentrations encountered by the corresponding cell types in vitro.


Publication metadata

Author(s): Ford D

Publication type: Article

Publication status: Published

Journal: Proceedings of the Nutrition Society

Year: 2004

Volume: 63

Issue: 1

Pages: 21-29

ISSN (print): 0029-6651

ISSN (electronic): 1475-2719

Publisher: Cambridge University Press

URL: http://dx.doi.org/10.1079/PNS2003320

DOI: 10.1079/PNS2003320

PubMed id: 15070437

Notes: Paper presented at the Summer Meeting of the Nutrition Society: Symposium on ‘New insights into the molecular regulation of trace element metabolism’, held at King's College, London, on 7-10 July 2003.


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Funding

Funder referenceFunder name
D18271Biotechnology and Biological Sciences Research Council

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