Cd{sup 2+} versus Zn{sup 2+} uptake by the ZIP8 HCO{sub 3}{sup -}-dependent symporter: Kinetics, electrogenicity and trafficking
- Department of Environmental Health and Center for Environmental Genetics (CEG), University of Cincinnati Medical Center, P.O. Box 670056, Cincinnati, OH 45267-0056 (United States)
- Department of Internal Medicine, Division of Nephrology and Hypertension, University Cincinnati Medical Center, Cincinnati, OH 45267-0056 (United States)
The mouse Slc39a8 gene encodes the ZIP8 transporter, which has been shown to be a divalent cation/HCO{sub 3}{sup -} symporter. Using ZIP8 cRNA-injected Xenopus oocyte cultures, we show herein that: [a] ZIP8-mediated cadmium (Cd{sup 2+}) and zinc (Zn{sup 2+}) uptake have V{sub max} values of 1.8 {+-} 0.08 and 1.0 {+-} 0.08 pmol/oocyte/h, and K{sub m} values of 0.48 {+-} 0.08 and 0.26 {+-} 0.09 {mu}M, respectively; [b] ZIP8-mediated Cd{sup 2+} uptake is most inhibited by Zn{sup 2+}, second-best inhibited by Cu{sup 2+}, Pb{sup 2+} and Hg{sup 2+}, and not inhibited by Mn{sup 2+} or Fe{sup 2+}; and [c] electrogenicity studies demonstrate an influx of two HCO{sub 3}{sup -} anions per one Cd{sup 2+} (or one Zn{sup 2+}) cation, i.e. electroneutral complexes. Using Madin-Darby canine kidney (MDCK) polarized epithelial cells retrovirally infected with ZIP8 cDNA and tagged with hemagglutinin at the C-terminus, we show that-similar to ZIP4-the ZIP8 eight-transmembrane protein is largely internalized during Zn{sup 2+} homeostasis, but moves predominantly to the cell surface membrane (trafficking) under conditions of Zn{sup 2+} depletion.
- OSTI ID:
- 21043594
- Journal Information:
- Biochemical and Biophysical Research Communications, Vol. 365, Issue 4; Other Information: DOI: 10.1016/j.bbrc.2007.11.067; PII: S0006-291X(07)02459-X; Copyright (c) 2007 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0006-291X
- Country of Publication:
- United States
- Language:
- English
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