Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Little is known at the molecular level about the homeostatic control of heavy-metal concentrations in mammals. Recently, however, two human diseases that disrupt copper transport, Menkes disease and Wilson disease, were found to be caused by mutations in two closely related genes, MNK and WND, which encode proteins belonging to the P-type ATPase family of cation transporters. The MNK and WND proteins are unique in having at their amino termini six copies of a sequence that is remarkably similar to sequences previously found in bacterial heavy-metal-resistance proteins and in a P-type ATPase that appears to form part of a bacterial copper homeostatic system. These two human ATPases are the first putative heavy-metal transporters to be discovered in eukaryotes.
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PMID:Wilson disease and Menkes disease: new handles on heavy-metal transport. 809 5

Menkes' disease is a fatal, X-linked, copper deficiency disorder that results from defective copper efflux from intestinal cells and inadequate copper delivery to other tissues, leading to deficiencies of critical copper-dependent enzymes. Wilson's disease is an autosomally inherited, copper toxicosis disorder resulting from defective biliary excretion of copper, which leads to copper accumulation in the liver. The ATP7A and ATP7B genes that are defective in patients with Menkes' and Wilson's diseases, respectively, encode transmembrane, P-type ATPase proteins (ATP7A or MNK and ATP7B or WND, respectively) that function to translocate copper across cellular membranes. In this study, the cDNAs derived from a normal human ATP7A gene and the murine ATP7B homologue, Atp7b, were separately transfected into an immortalized fibroblast cell line obtained from a Menkes' disease patient. Both MNK and WND expressed from plasmid constructs were able to correct the copper accumulation and copper retention phenotype of these cells. However, the two proteins responded differently to elevated extracellular copper levels. Although MNK showed copper-induced trafficking from the trans-Golgi network to the plasma membrane, in the same cell line the intracellular location of WND did not appear to be affected by elevated copper.
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PMID:Correction of the copper transport defect of Menkes patient fibroblasts by expression of the Menkes and Wilson ATPases. 981 47

The mutant strain Long-Evans Cinnamon (LEC) rat, which accumulates copper in the liver because of a mutation in the Atp7b gene, encoding a copper-ATPase, is a model of Wilson disease. It spontaneously develops hepatitis, and subsequently hepatocellular carcinoma and cholangiofibrosis. Excess intracellular copper has been thought to induce DNA damage through reactive oxygen species produced by Cu (II)/Cu (I) redox cycling, and also by direct interaction with DNA. We have developed lacI transgenic Wilson disease (WND-B) rats by mating LEC with Big Blue F344 rats carrying a lambda shuttle vector harboring the lacI gene. lacI mutations of the livers of C-B heterozygous (Atp7b w/m, lacI) and WND-B homozygous (Atp7b m/m, lacI) rats at 6, 24, and 40 weeks of ages were analyzed. Mutant frequencies in the WND-B rats were 2.0 +/- 0.7 x 10(-5), 5.3 +/- 0.9 x 10(-5), and 5.3 +/- 1.0 x 10(-5), respectively, significantly higher than those of C-B rats. Nucleotide sequence analysis revealed that the frequency of deletion mutations of more than two nucleotides were much higher, 15% in WND-B rats, but only 2% in C-B rats. In addition, the average size of deletion was larger in the former. Loss of oligonucleotide-repeat units was specific and relatively frequent in WND-B rats. This type of mutation might be implicated in the induction of DNA strand scissions by reactive oxygen species. These findings suggest that the increase in mutant frequencies and/or the specific type of mutation according to copper accumulation play a crucial role in hepatocarcinogenesis in LEC rats.
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PMID:Increased mutant frequency and altered mutation spectrum of the lacI transgene in Wilson disease rats with hepatitis. 1101 32

Wilson disease is an autosomal recessive copper transport disorder resulting from defective biliary excretion of copper and subsequent hepatic copper accumulation and liver failure if not treated. The disease is caused by mutations in the ATP7B (WND) gene, which is expressed predominantly in the liver and encodes a copper-transporting P-type ATPase that is structurally and functionally similar to the Menkes protein (MNK), which is defective in the X-linked copper transport disorder Menkes disease. The toxic milk (tx) mouse has a clinical phenotype similar to Wilson disease patients and, recently, the tx mutation within the murine WND homologue (WND:) of this mouse was identified, establishing it as an animal model for Wilson disease. In this study, cDNA constructs encoding the wild-type (Wnd-wt) and mutant (Wnd-tx) Wilson proteins (Wnd) were generated and expressed in Chinese hamster ovary (CHO) cells. The tx mutation disrupted the copper-induced relocalization of Wnd in CHO cells and abrogated Wnd-mediated copper resistance of transfected CHO cells. In addition, co-localization experiments demonstrated that while Wnd and MNK are located in the trans-Golgi network in basal copper conditions, with elevated copper, these proteins are sorted to different destinations within the same cell. Ultrastructural studies showed that with elevated copper levels, Wnd accumulated in large multi-vesicular structures resembling late endosomes that may represent a novel compartment for copper transport. The data presented provide further support for a relationship between copper transport activity and the copper-induced relocalization response of mammalian copper ATPases, and an explanation at a molecular level for the observed phenotype of tx mice.
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PMID:Effect of the toxic milk mutation (tx) on the function and intracellular localization of Wnd, the murine homologue of the Wilson copper ATPase. 1115 99

The Wilson protein (WND; ATP7B) is an essential component of copper homeostasis. Mutations in the ATP7B gene result in Wilson disease, which is characterised by hepatotoxicity and neurological disturbances. In this paper, we provide the first direct biochemical evidence that the WND protein functions as a copper-translocating P-type ATPase in mammalian cells. Importantly, we have shown that the mutation of the conserved Met1386 to Val, in the Atp7B for the mouse model of Wilson disease, toxic milk (tx), caused a loss of Cu-translocating activity. These investigations provide strong evidence that the toxic milk mouse is a valid model for Wilson disease and demonstrate a link between the loss of catalytic function of WND and the Wilson disease phenotype.
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PMID:Functional studies on the Wilson copper P-type ATPase and toxic milk mouse mutant. 1123 56

Copper homeostasis is achieved by a combination of regulated uptake, efflux and sequestration and is essential for animal health and viability. Transmembrane copper transport proteins of the P-type ATPase family play key roles in cellular copper efflux. Here, the transcriptional and post-translational regulation of DmATP7, the sole Drosophila melanogaster ortholog of the human MNK and WND copper transport genes, is examined. An enhancer element with sufficient regulatory information to rescue DmATP7 mutant flies to adulthood is identified. This regulatory element drives expression in all neuronal tissues examined and demonstrates copper-inducible, Mtf-1 dependent expression in the larval midgut. These results support an important functional role for copper transport in neuronal tissues and indicate that regulation of DmATP7 expression is not used to limit copper absorption in toxic copper conditions. Localisation of a functional EYFP-DmATP7 fusion protein is also examined. This fusion protein localises at or proximal to the basolateral membrane of DmATP7 expressing midgut cells supporting a role for DmATP7 in export of copper from midgut cells.
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PMID:Expression and localisation of the essential copper transporter DmATP7 in Drosophila neuronal and intestinal tissues. 1832 64