Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0022716 (Menkes)
 1,057 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

ATP7A encodes a copper-translocating ATPase that belongs to the large family of P-type ATPases. Eight conserved regions define the core of the P-type ATPase superfamily. We report here the identification of 21 novel missense mutations in the conserved part of ATP7A that encodes the residues p.V842-p.S1404. Using the coordinates of X-ray crystal structures of the sarcoplasmic reticulum Ca(2+)-ATPase, as determined in the presence and absence of Ca(2+), we created structural homology models of ATP7A. By mapping the substituted residues onto the models, we found that these residues are more clustered three-dimensionally than expected from the primary sequence. The location of the substituted residues in conserved regions supports the functional similarities between the two types of P-type ATPases. An immunofluorescence analysis of Menkes fibroblasts suggested that the localization of a large number of the mutated ATP7A protein variants was correct. In the absence of copper, they were located in perinuclear regions of the cells, just like the wild type. However, two of the mutated ATP7A variants showed only partly correct localization, and in five cultures no ATP7A protein could be detected. These findings suggest that although a disease-causing mutation may indicate a functional significance of the affected residue, this is not always the case.
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PMID:Identification and analysis of 21 novel disease-causing amino acid substitutions in the conserved part of ATP7A. 1598 Dec 43

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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PMID: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. 1608 13

Menkes disease is a fatal disease that can be induced by various mutations in the ATP7A gene, leading to unpaired uptake of dietary copper. The ATP7A gene encodes a copper(I)-translocating ATPase. Here the disease-causing A629P mutation, which occurs in the last of the six copper(I)-binding soluble domains of the ATPase (hereafter MNK6), was investigated. To understand why this apparently minor amino acid replacement is pathogenic, the solution structures and dynamics on various time-scales of wild-type and A629P-MNK6 were determined both in the apo- and copper(I)-loaded forms. The interaction in vitro with the physiological ATP7A copper(I)-donor (HAH1) was additionally studied. The A629P mutation makes the protein beta-sheet more solvent accessible, possibly resulting in an enhanced susceptibility of ATP7A to proteolytic cleavage and/or in reduced capability of copper(I)-translocation. A small reduction of the affinity for copper(I) is also observed. Both effects could concur to pathogenicity.
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PMID:An atomic-level investigation of the disease-causing A629P mutant of the Menkes protein, ATP7A. 1608 5

We describe a child with classical Menkes disease with a novel ATP7A mutation, intractable seizures, severe hypotonia and developmental delay, hypopigmentation of the skin and hair, and failure to thrive, who was treated with daily subcutaneous copper histidine injections for 2(1/2) years, beginning at 15 months of age. He became seizure-free and pigmentation of his skin and hair darkened, but he continued to have severe developmental delays. His condition remains stable 8 months after stopping treatment. We review the ethical aspects of offering copper treatment for Menkes disease infants diagnosed after neurological symptoms become manifest. These include (1) the prospect for any benefits, (2) the potential risks and discomforts, (3) the parents' wishes with respect to treatment, (4) the family's understanding of the treatment's potential futility, (5) the family's understanding of the investigational nature of this treatment, (6) the potential for treatment to have an adverse impact on unaffected family members, (7) whether the ultimate decision regarding treatment should rest with health care providers or with the patient's parents, and (8) the duration of treatment. The ethical issues encountered in providing possibly futile treatment in this difficult disorder seem relevant to other pediatric medical conditions as well.
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PMID:Copper-replacement treatment for symptomatic Menkes disease: ethical considerations. 1609 18

Menkes disease (MD) is a neurodegenerative disorder caused by mutation of the copper transporter ATP7A. While several enzymes expressed in mature neurons require copper, MD neurodegenerative changes cannot be explained by known requirements for ATP7A in neuronal development. To investigate additional roles for ATP7A during development, we characterized its pattern of expression using the olfactory system as a neurodevelopmental model. ATP7A expression in neurons was developmentally regulated rather than constitutively. Initially expressed in the cell bodies of developing neurons, ATP7A protein later shifted to extending axons, peaking prior to synaptogenesis. Similarly, after injury-stimulated neurogenesis, ATP7A expression increased in neurons and axons preceding synaptogenesis. Interestingly, copper-transport-deficient ATP7A still exhibits axonal localization. These results support a role for ATP7A in axon extension, which may contribute to the severe neurodegeneration characteristic of MD.
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PMID:The developmentally regulated expression of Menkes protein ATP7A suggests a role in axon extension and synaptogenesis. 1613 91

Menkes' disease is a rare X-linked multisystemic lethal disorder of copper transport metabolism. Failure of synthesis of several copper enzymes explains most of the clinical features, which were characterised by neurodegenerative symptoms and connective tissue manifestations. Most cases are still prone to rapidly progressive cerebral degeneration and early death in the first few years. Since CNS-dysfunction usually preceeds development of the pathognomonic "steely" hair, delay of clinical diagnosis and onset of therapeutic intervention precludes longlasting neurological benefit. This is particularly true for patients with large deletions or severe truncations of the responsible ATP7A gene. We report on our own experience with a patient, who was diagnosed to be affected by Menkes' syndrome at the age of one year, due to the specific hair texture and biochemical abnormalities. Molecular investigation revealed a total deletion of exon 15 of the ATP7A gene. Heterozygosity was confirmed by means of real-time PCR in the child's mother, but could be excluded in the grandmother and other female relatives at risk. Therapeutic support with subcutaneous injection of copper-histidinate normalised diminished copper and coeruloplasmin serum levels, but was unable to influence the clinical course and to prevent the fatal outcome at the age of two years. This observation is in line with the experience of the literature claiming that currently available medication will hardly be able to normalise brain copper levels. However, observations of clinical variants of Menkes' disease with quite a different outcome and, more importantly, emerging of alternative copper transport pathways might still justify this time-limited therapeutic intervention.
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PMID:[Menkes' disease: heterozygosity testing by quantitative real-time PCR and the dilemma of therapeutic support]. 1616 77

Satraplatin is an orally bioavailable platinum analog that has activity in prostate cancer. JM118 is the most abundant species found in the plasma following the oral ingestion of satraplatin and has anti-tumor activity in vitro against cell lines that are resistant to cisplatin (DDP). The goal of the current study was to determine whether the activity of JM118 in some DDP-resistant cells can be explained by differences in the cellular pharmacology of the two drugs. The effect of each of the Cu transporters CTR1, ATP7A and ATP7B on sensitivity to the growth inhibitory effect of JM118 and its cellular pharmacology was examined to identify the characteristics of JM118 that distinguish it from DDP. These studies were performed using wild type and CTR1-/- homozygous knockout mouse embryo cells, and human Me32a Menkes disease fibroblasts that do not express either ATP7A or ATP7B plus sublines molecularly engineered to express either ATP7A (MeMNK cells) or ATP7B (MeWND cells). Knockout of the Cu influx transporter CTR1 in murine embryo cells increased their resistance to DDP and reduced its cellular accumulation but had no effect on sensitivity to JM118 or its uptake. In the case of DDP, forced expression of either of the two Cu efflux transporters, ATP7A or ATP7B, in Me32a cells rendered them resistant to DDP, increased whole cell accumulation of Pt but reduced the amount of Pt in DNA. In the case of JM118, forced expression of either ATP7A or ATP7B rendered Me32a cells resistant, increased not only whole cell Pt accumulation but also increased rather than decreased the amount of Pt in DNA. These results demonstrate that both ATP7A and ATP7B mediate resistance to JM118 as well as DDP and suggest that they sequester both DDP and JM118 into vesicular compartments within the cell resulting in enhanced whole cell accumulation and reduced cytotoxicity. We conclude that there are two important differences between DDP and JM118 with respect to the effect of Cu transporters on their cellular pharmacology. First, whereas CTR1 is involved in DDP accumulation it does not play a role in the uptake of JM118. Second, ATP7A and ATP7B, while they both mediate resistance, have opposite effects on the accumulation of Pt in DNA following exposure to the two drugs. ATP7A and ATP7B appear to be able to modulate the toxicity of the Pt that accumulates in DNA following exposure to JM118. These results suggest that JM118 will retain activity in cells in which DDP resistance is due to the loss of CTR1, but not in cells in which resistance is due to enhanced expression of ATP7A or ATP7B.
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PMID:Modulation of the cellular pharmacology of JM118, the major metabolite of satraplatin, by copper influx and efflux transporters. 1617 May 71

The aim was to study the subcellular localization of the Menkes protein (MNK; ATP7A) in the rat parotid acinar cell. MNK protein is a copper transporting P-type ATPase whose absence or dysfunction causes a fatal neurodegenerative disorder, MNK disease. Rat parotid glands were fixed and low-temperature embedded in Lowicryl K4M resin, and ultrathin sections were prepared for immunocytochemical analysis. Immunolocalization of MNK was demonstrated mainly over the trans Golgi network (TGN) area. Immature and mature secretory granules were also labelled, indicating that MNK protein could be involved here in copper secretion from acinar cells into saliva, consistent with a proposed cariostatic role for copper.
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PMID:Menkes protein localization in rat parotid acinar cells. 1618 50

The final steps in the absorption and excretion of copper at the molecular level are accomplished by 2 closely related proteins that catalyze the ATP-dependent transport of copper across the plasma membrane. These proteins, ATP7A and ATP7B, are encoded by the genes affected in human genetic copper-transport disorders, namely, Menkes and Wilson diseases. We studied the effect of copper perfusion of an isolated segment of the jejunum of ATP7A transgenic mice on the intracellular distribution of ATP7A by immunofluorescence of frozen sections. Our results indicate that ATP7A is retained in the trans-Golgi network under copper-limiting conditions, but relocalized to a vesicular compartment adjacent to the basolateral membrane in intestines perfused with copper. The findings support the hypothesis that the basolateral transport of copper from the enterocyte into the portal blood may involve ATP7A pumping copper into a vesicular compartment followed by exocytosis to release the copper, rather than direct pumping of copper across the basolateral membrane.
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PMID:Copper exposure induces trafficking of the menkes protein in intestinal epithelium of ATP7A transgenic mice. 1631 17

The Menkes protein (ATP7A) is defective in the Cu deficiency disorder Menkes disease and is an important contributor to the maintenance of physiological Cu homeostasis. To investigate more fully the role of ATP7A, transgenic mice expressing the human Menkes gene ATP7A from chicken beta-actin composite promoter (CAG) were produced. The transgenic mice expressed ATP7A in lung, heart, liver, kidney, small intestine, and brain but displayed no overt phenotype resulting from expression of the human protein. Immunohistochemical analysis revealed that ATP7A was found primarily in the cardiac muscle, smooth muscle of the lung, distal tubules of the kidney, intestinal enterocytes, and patches of hepatocytes, as well as in the hippocampus, cerebellum, and choroid plexus of the brain. In 60-day- and 300-day-old mice, Cu concentrations were reduced in most tissues, consistent with ATP7A playing a role in Cu efflux. The reduction in Cu was most pronounced in the hearts of older T22#2 females (24%), T22#2 males (18%), and T25#5 females (23%), as well as in the brains of 60-day-old T22#2 females and males (23% and 30%, respectively).
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PMID:Alteration of copper physiology in mice overexpressing the human Menkes protein ATP7A. 1639 91


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