Menkes Copper ATPase (Atp7a) is a novel metal-responsive gene in rat duodenum, and immunoreactive protein is present on brush-border and basolateral membrane domains

Jennifer J. Ravia, Renu M. Stephen, Fayez K Ghishan, James F. Collins

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Abstract

We previously noted strong induction of genes related to intestinal copper homeostasis (Menkes Copper ATPase (Atp7a) and metallothionein) in the duodenal epithelium of iron-deficient rats across several stages of postnatal development (Collins, J. F., Franck, C. A., Kowdley, K. V., and Ghishan, F. K. (2005) Am. J. Physiol., 288, G964-G971). We now report significant copper loading in the livers and intestines of iron-deficient rats. These findings are consistent with the hypothesis that there is increased intestinal copper transport during iron deficiency. We additionally found that hepatic Atp7b gene expression does not change with iron deficiency, suggesting that liver copper excretion is not altered. We have developed polyclonal antibodies against rat ATP7A, and we demonstrate the specificity of the immunogenic reaction. We show that the ATP7A protein is present on apical domains of duodenal enterocytes in control rats and on brush-border and basolateral membrane domains in iron-deprived rats. This localization is surprising, as previous in vitro studies have suggested that ATP7A traffics between the trans-Golgi network and the basolateral membrane. We further demonstrate that ATP7A protein levels are dramatically increased in brush-border and basolateral membrane vesicles isolated from iron-deficient rats. Other experiments show that iron refeeding partially corrects the hematological abnormalities seen in iron-deficient rats but that it does not ameliorate ATP7A protein induction, suggesting that Atp7a does not respond to intracellular iron levels. We conclude that ATP7A is involved in copper loading observed during iron deficiency and that increased intestinal copper transport is of physiological relevance, as copper plays important roles in overall body iron homeostasis.

Original languageEnglish (US)
Pages (from-to)36221-36227
Number of pages7
JournalJournal of Biological Chemistry
Volume280
Issue number43
DOIs
StatePublished - Oct 28 2005

Fingerprint

Brushes
Microvilli
Duodenum
Adenosine Triphosphatases
Rats
Copper
Iron
Genes
Metals
Membranes
Proteins
Liver
Homeostasis
Rat control
trans-Golgi Network
Enterocytes
Metallothionein
Gene expression
Intestines
Epithelium

ASJC Scopus subject areas

  • Biochemistry

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Menkes Copper ATPase (Atp7a) is a novel metal-responsive gene in rat duodenum, and immunoreactive protein is present on brush-border and basolateral membrane domains. / Ravia, Jennifer J.; Stephen, Renu M.; Ghishan, Fayez K; Collins, James F.

In: Journal of Biological Chemistry, Vol. 280, No. 43, 28.10.2005, p. 36221-36227.

Research output: Contribution to journalArticle

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abstract = "We previously noted strong induction of genes related to intestinal copper homeostasis (Menkes Copper ATPase (Atp7a) and metallothionein) in the duodenal epithelium of iron-deficient rats across several stages of postnatal development (Collins, J. F., Franck, C. A., Kowdley, K. V., and Ghishan, F. K. (2005) Am. J. Physiol., 288, G964-G971). We now report significant copper loading in the livers and intestines of iron-deficient rats. These findings are consistent with the hypothesis that there is increased intestinal copper transport during iron deficiency. We additionally found that hepatic Atp7b gene expression does not change with iron deficiency, suggesting that liver copper excretion is not altered. We have developed polyclonal antibodies against rat ATP7A, and we demonstrate the specificity of the immunogenic reaction. We show that the ATP7A protein is present on apical domains of duodenal enterocytes in control rats and on brush-border and basolateral membrane domains in iron-deprived rats. This localization is surprising, as previous in vitro studies have suggested that ATP7A traffics between the trans-Golgi network and the basolateral membrane. We further demonstrate that ATP7A protein levels are dramatically increased in brush-border and basolateral membrane vesicles isolated from iron-deficient rats. Other experiments show that iron refeeding partially corrects the hematological abnormalities seen in iron-deficient rats but that it does not ameliorate ATP7A protein induction, suggesting that Atp7a does not respond to intracellular iron levels. We conclude that ATP7A is involved in copper loading observed during iron deficiency and that increased intestinal copper transport is of physiological relevance, as copper plays important roles in overall body iron homeostasis.",
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