Biochem. J. (2007) 402
(241–250) (Printed in Great Britain)
Hormonal regulation of the Menkes and Wilson copper-transporting ATPases in human placental Jeg-3 cells
Belinda HARDMAN*, Agnes MICHALCZYK*, Mark GREENOUGH†, James CAMAKARIS†, Julian F. B. MERCER* and M. Leigh ACKLAND*1
*Centre for Cellular and Molecular Biology, School of Life and Environmental Sciences, Deakin University, Melbourne Campus, 221 Burwood Highway, Burwood, Victoria 3125, Australia, and †Department of Genetics, Melbourne University, Melbourne, Victoria 3010, Australia
Copper deficiency during pregnancy results in early embryonic death and foetal structural abnormalities including skeletal, pulmonary and cardiovascular defects. During pregnancy, copper is transported from the maternal circulation to the foetus by mechanisms which have not been clearly elucidated. Two copper-transporting ATPases, Menkes (ATP7A; MNK) and Wilson (ATP7B; WND), are expressed in the placenta and both are involved in placental copper transport, as copper accumulates in the placenta in both Menkes and Wilson disease. The regulatory mechanisms of MNK and WND and their exact role in the placenta are unknown. Using a differentiated polarized Jeg-3 cell culture model of placental trophoblasts, MNK and WND were shown to be expressed within these cells. Distinct roles for MNK and WND are suggested on the basis of their opposing responses to insulin. Insulin and oestrogen increased both MNK mRNA and protein levels, altered the localization of MNK towards the basolateral membrane in a copper-independent manner, and increased the transport of copper across this membrane. In contrast, levels of WND were decreased in response to insulin, and the protein was located in a tight perinuclear region, with a corresponding decrease in copper efflux across the apical membrane. These results are consistent with a model of copper transport in the placenta in which MNK delivers copper to the foetus and WND returns excess copper to the maternal circulation. Insulin and oestrogen stimulate copper transport to the foetus by increasing the expression of MNK and reducing the expression of WND. These data show for the first time that MNK and WND are differentially regulated by the hormones insulin and oestrogen in human placental cells.
Key words: Copper, insulin, Menkes disease, oestrogen, pregnancy, Wilson disease.
Abbreviations used: BCS, bathocuproinedisulfonic acid; CT, threshold cycle; EHS, Engelbreth Holm-Swarm; ERE, oestrogen response elements; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; GLUT, glucose transporter; IGF, insulin-like growth factor; IRS, insulin response sequence; MNK/ATP7A, Menkes-disease protein; PET, polyethylene terephthalate; TBS, Tris-buffered saline; TGN, trans-Golgi network; WND/ATP7B, Wilson-disease protein.
1To whom correspondence should be addressed (email leigha@deakin.edu.au).
Received 19 July 2006/10 October 2006; accepted 16 November 2006
Published as BJ Immediate Publication 16 November 2006, doi:10.1042/BJ20061099
The Biochemical Society, London ©2007
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