Abstract
Two P-type ATPases, MNK and WND were recently shown to be defective in the human disorders of copper transport, Menkes disease and Wilson disease respectively. These proteins are important in copper homeostasis but their full physiological function has not been established. This study uses the human breast carcinoma line, PMC42, to investigate copper transport in the mammary gland. Northern blot analysis indicated that both MNK and WND mRNA are expressed in these cells. Western blot analysis with an MNK-specific antibody demonstrated a band of approx. 178 kDa, close to the expected size of 163 kDa. Treatment of PMC42 cells with lactational hormones (oestrogen and progesterone for 3 days followed by dexamethasone, insulin and prolactin for a further 3 days) did not produce an obvious increase in MNK expression as measured by Northern and Western blots. By using indirect immunofluorescence with the MNK antibody, the intracellular distribution of MNK was found to be predominantly perinuclear, consistent with Golgi localization. Punctate staining was also seen in a smaller proportion of cells, suggesting that some MNK is associated with endosomes. Treatment of PMC42 cells with lactational hormones increased the intensity of the perinuclear and punctate fluorescence. Exposure of cells to 100 mM copper resulted in the dispersion of the fluorescence towards the periphery of the cell. The results suggest a role for MNK in the secretion of copper into milk and that PMC42 cells are a valuable model for investigating the detailed cellular function of MNK and WND.
Full Text
The Full Text of this article is available as a PDF (392.0 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Bull P. C., Thomas G. R., Rommens J. M., Forbes J. R., Cox D. W. The Wilson disease gene is a putative copper transporting P-type ATPase similar to the Menkes gene. Nat Genet. 1993 Dec;5(4):327–337. doi: 10.1038/ng1293-327. [DOI] [PubMed] [Google Scholar]
- Camakaris J., Petris M. J., Bailey L., Shen P., Lockhart P., Glover T. W., Barcroft C., Patton J., Mercer J. F. Gene amplification of the Menkes (MNK; ATP7A) P-type ATPase gene of CHO cells is associated with copper resistance and enhanced copper efflux. Hum Mol Genet. 1995 Nov;4(11):2117–2123. doi: 10.1093/hmg/4.11.2117. [DOI] [PubMed] [Google Scholar]
- Casey C. E., Hambidge K. M., Neville M. C. Studies in human lactation: zinc, copper, manganese and chromium in human milk in the first month of lactation. Am J Clin Nutr. 1985 Jun;41(6):1193–1200. doi: 10.1093/ajcn/41.6.1193. [DOI] [PubMed] [Google Scholar]
- Chelly J., Tümer Z., Tønnesen T., Petterson A., Ishikawa-Brush Y., Tommerup N., Horn N., Monaco A. P. Isolation of a candidate gene for Menkes disease that encodes a potential heavy metal binding protein. Nat Genet. 1993 Jan;3(1):14–19. doi: 10.1038/ng0193-14. [DOI] [PubMed] [Google Scholar]
- Mercer J. F., Livingston J., Hall B., Paynter J. A., Begy C., Chandrasekharappa S., Lockhart P., Grimes A., Bhave M., Siemieniak D. Isolation of a partial candidate gene for Menkes disease by positional cloning. Nat Genet. 1993 Jan;3(1):20–25. doi: 10.1038/ng0193-20. [DOI] [PubMed] [Google Scholar]
- Paynter J. A., Grimes A., Lockhart P., Mercer J. F. Expression of the Menkes gene homologue in mouse tissues lack of effect of copper on the mRNA levels. FEBS Lett. 1994 Sep 5;351(2):186–190. doi: 10.1016/0014-5793(94)00868-x. [DOI] [PubMed] [Google Scholar]
- Petris M. J., Mercer J. F., Culvenor J. G., Lockhart P., Gleeson P. A., Camakaris J. Ligand-regulated transport of the Menkes copper P-type ATPase efflux pump from the Golgi apparatus to the plasma membrane: a novel mechanism of regulated trafficking. EMBO J. 1996 Nov 15;15(22):6084–6095. [PMC free article] [PubMed] [Google Scholar]
- Piechaczyk M., Blanchard J. M., Marty L., Dani C., Panabieres F., El Sabouty S., Fort P., Jeanteur P. Post-transcriptional regulation of glyceraldehyde-3-phosphate-dehydrogenase gene expression in rat tissues. Nucleic Acids Res. 1984 Sep 25;12(18):6951–6963. doi: 10.1093/nar/12.18.6951. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Rauch H. Toxic milk, a new mutation affecting cooper metabolism in the mouse. J Hered. 1983 May-Jun;74(3):141–144. doi: 10.1093/oxfordjournals.jhered.a109751. [DOI] [PubMed] [Google Scholar]
- Tanzi R. E., Petrukhin K., Chernov I., Pellequer J. L., Wasco W., Ross B., Romano D. M., Parano E., Pavone L., Brzustowicz L. M. The Wilson disease gene is a copper transporting ATPase with homology to the Menkes disease gene. Nat Genet. 1993 Dec;5(4):344–350. doi: 10.1038/ng1293-344. [DOI] [PubMed] [Google Scholar]
- Theophilos M. B., Cox D. W., Mercer J. F. The toxic milk mouse is a murine model of Wilson disease. Hum Mol Genet. 1996 Oct;5(10):1619–1624. doi: 10.1093/hmg/5.10.1619. [DOI] [PubMed] [Google Scholar]
- Vulpe C., Levinson B., Whitney S., Packman S., Gitschier J. Isolation of a candidate gene for Menkes disease and evidence that it encodes a copper-transporting ATPase. Nat Genet. 1993 Jan;3(1):7–13. doi: 10.1038/ng0193-7. [DOI] [PubMed] [Google Scholar]
- Whitehead R. H., Bertoncello I., Webber L. M., Pedersen J. S. A new human breast carcinoma cell line (PMC42) with stem cell characteristics. I. Morphologic characterization. J Natl Cancer Inst. 1983 Apr;70(4):649–661. [PubMed] [Google Scholar]
- Whitehead R. H., Monaghan P., Webber L. M., Bertoncello I., Vitali A. A. A new human breast carcinoma cell line (PMC42) with stem cell characteristics. II. Characterization of cells growing as organoids. J Natl Cancer Inst. 1983 Dec;71(6):1193–1203. [PubMed] [Google Scholar]
- Whitehead R. H., Quirk S. J., Vitali A. A., Funder J. W., Sutherland R. L., Murphy L. C. A new human breast carcinoma cell line (PMC42) with stem cell characteristics. III. Hormone receptor status and responsiveness. J Natl Cancer Inst. 1984 Sep;73(3):643–648. [PubMed] [Google Scholar]
- Yamaguchi Y., Heiny M. E., Gitlin J. D. Isolation and characterization of a human liver cDNA as a candidate gene for Wilson disease. Biochem Biophys Res Commun. 1993 Nov 30;197(1):271–277. doi: 10.1006/bbrc.1993.2471. [DOI] [PubMed] [Google Scholar]