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)

Copper is an essential trace element that requires tightly regulated homeostatic mechanisms to ensure adequate supplies without any toxic effects because of the ability of the metal ion to catalyze the formation of free radicals. The Cu-ATPases, ATP7A and ATP7B, play an important role in the physiological regulation of copper. Adequate supplies of copper are particularly important in developing animals, and in humans this is illustrated by mutations of ATP7A that cause the copper deficiency condition Menkes disease, which is fatal in early childhood. In contrast, mutations in ATP7B result in the genetic toxicosis, Wilson disease. We propose that the physiological regulation of copper is accomplished mainly by the intracellular copper-regulated trafficking of the Cu-ATPases. This process allows the overall copper status in the body to be maintained when levels of copper in the diet alter. A study of the defects in mouse models of Menkes and Wilson diseases has demonstrated that both ATPases play an important role in supplying copper to the developing fetus and neonate.
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PMID:Molecular and cellular aspects of copper transport in developing mammals. 1273 Apr 48

Genetic defects in copper metabolism highlight the delicate balance mammalian systems have developed to maintain normal copper homeostasis. Menkes disease, the mottled mouse, the Atox-1-deficient mouse and the ctr1 knockout mouse reveal the importance of adequate copper intake during embryogenesis and early development, especially in the central nervous system. The toxicity associated with excess copper as manifest in Wilson disease, the toxic milk mouse, the LEC rat and copper toxicosis in the Bedlington terrier demonstrate the profound cellular susceptibility to copper overload, in particular, in the brain and liver. Ceruloplasmin (Cp) contains 95% of the copper found in human serum, and inherited loss of this protein results in diabetes, retinal degeneration and neurodegeneration. Despite normal copper metabolism, aceruloplasminemic patients and the Cp knockout mouse have disturbed iron homeostasis and mild hepatic copper retention. These genetic disorders of copper metabolism provide valuable insight into the mechanisms regulating copper homeostasis and models to further dissect the role of this essential metal in health and disease.
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PMID:Genetic defects in copper metabolism. 1273 Apr 58

Copper is essential for many copper-dependent processes, including mitochondrial oxidative phosphorylation, free-radical detoxification, pigmentation, neurotransmitter synthesis, and iron metabolism. The identification of proteins for high affinity copper uptake and export has greatly expanded our understanding of cellular copper homeostasis. Copper export in human cells is mediated by the ATP7A and ATP7B P-type ATPases, which are, respectively, affected in the genetic disorders of copper metabolism, Menkes disease and Wilson disease. A different class of transporter known as the SLC31 or Ctr family of proteins mediates cellular copper uptake. These high-affinity copper transporters exist in all eukaryotes and their discovery has provided new insights into how cells acquire and regulate this essential nutrient. The following is a brief overview of the SLC31 copper transporter family with a focus on the human hCtr1 protein.
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PMID:The SLC31 (Ctr) copper transporter family. 1282 56

The trace metal copper is an essential cofactor for a number of biological processes, including mitochondrial oxidative phosphorylation, free-radical eradication, neurotransmitter synthesis and maturation, and iron metabolism. Consequently, copper transport at the cell surface and the delivery of copper to intracellular proteins are critical events in normal cellular homeostasis. Four genes have been reported to influence the cellular uptake and the delivery of copper to specific cell compartments and proteins. These include hCTR1, which regulates cellular copper uptake; HAH1, which mediates the transfer of copper to the Menkes and Wilson disease transporters; CCS, which is related to the transfer of copper to superoxide dismutase; and hCOX17, which directs trafficking of copper to mitochondrial cytochrome-c oxidase. At present, no genetic disorders have been associated with defects in these four copper transporter genes. In this study, we test the possibility that defective copper uptake or intracellular translocation represents the basic defect in three categories of candidate phenotypes among 22 patients: ethylmalonic encephalopathy; mitochondriopathies of unknown aetiology; and neurodevelopmental abnormalities with clinical and chemical evidence of copper deficiency. Mutation analyses of the copper uptake protein, hCTR1, and the three copper chaperones were performed by direct sequencing of the whole coding regions. No causative mutations were identified for the four copper transporter genes in 22 patients. A heterozygous polymorphism (847G>A) for CCS was detected in 7 patients. For the distinct disease entity ethylmalonic encephalopathy, we additionally show normal mRNA levels for each of the four genes. The negative results notwithstanding, we encourage ongoing study of additional patients with candidate phenotypes. Further, our results are consistent with the notion that other unknown copper-related transporters could be involved in diseases.
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PMID:Mutation analysis of copper transporter genes in patients with ethylmalonic encephalopathy, mitochondriopathies and copper deficiency phenotypes. 1287 41

Wilson disease is an inherited autosomal recessive disorder of hepatic copper metabolism leading to copper accumulation in hepatocytes and in extrahepatic organs such as the brain and the cornea. Originally Wilson disease was described as a neurodegerative disorder associated with cirrhosis of the liver. Later, Wilson disease was observed in children and adolescents presenting with acute or chronic liver disease without any neurologic symptoms. While diagnosis of neurologic Wilson disease is straightforward, it may be quite difficult in non-neurologic cases. Up to now, no single diagnostic test can exclude or confirm Wilson disease with 100% certainty. In 1993, the gene responsible for Wilson disease was cloned and localized on chromosome 13q14.3 (MIM277900) (1, 2). The Wilson disease gene ATP7B encodes a P-type ATPase. More than 200 disease causing mutations of this gene have been described so far (3). Most of these mutations occur in single families, only a few are more frequent (like H1069Q, 3400delC and 2299insC in Caucasian (4-6) or R778L in Japanese (7), Chinese and Korean patients). Studies of phenotype-genotype relations are hampered by the lack of standard diagnostic criteria and phenotypic classifications. To overcome this problem, a working party discussed these problems in depth at the 8th International Meeting on Wilson disease and Menkes disease in Leipzig/Germany (April 16-18, 2001). After the meeting, a preliminary draft of a consensus report was mailed to all active participants and their comments were incorporated in the final text.
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PMID:Diagnosis and phenotypic classification of Wilson disease. 1591 May 6

The genes for two copper-transporting ATPases, ATP7A and ATP7B, are defective in the heritable disorders of copper imbalance, Menkes disease (MNK) and Wilson disease (WND), respectively. A comparison of the two proteins shows extensive conservation in the signature domains, with amino acid identities outside of the conserved domains being limited. The mutation spectra of MNK and WND were compared to confirm and refine further regions critical for normal function. Mutations were found to be relatively widespread; however, the majority was concentrated within defined functional domains and membrane-spanning segments, reinforcing the importance of these regions for protein function. Of the total published point mutations in ATP7A, 23.0% are splice-site, 20.7% nonsense, 17.2% missense, and 39.1% small insertions/deletions. There is a high prevalence (58.2%) of missense mutations in ATP7B. For the other mutations in ATP7B, 7.4% are splice-site, 7.4% nonsense, and 27.0% small insertions/deletions. A region of possible importance is the intervening sequence between the last copper-binding domain and the first transmembrane helix, as this region has a high percentage of MNK mutations. Similarly, the region containing the ATP-binding domain has 24.6% of all WND mutations. The study of mutation locations is useful for defining critical regions or residues and for efficient molecular diagnosis.
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PMID:A comparison of the mutation spectra of Menkes disease and Wilson disease. 1457 50

Menkes disease (MD) is an X-linked multisystemic lethal disorder of copper metabolism dominated by neurodegenerative symptoms and connective tissue disturbances. MD results from mutations in the ATP7A gene, which encodes a membrane-bound copper transporting P-type ATPase located in the trans-Golgi network. In this study we describe screening of 383 unrelated patients affected with Menkes disease for gross deletions in ATP7A gene and finding of 57 patients. The present data suggests that gross deletion of ATP7A is the disease-causing mutation in 14.9% of the Menkes disease patients. Except for a few cases, gross gene deletions result in the classical form of Menkes disease with death in early childhood.
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PMID:Screening of 383 unrelated patients affected with Menkes disease and finding of 57 gross deletions in ATP7A. 1463 5

The Wilson disease protein (WND) is a transport ATPase involved in copper delivery to the secretory pathway. Mutations in WND and its homolog, the Menkes protein, lead to genetic disorders of copper metabolism. The WND and Menkes proteins are distinguished from other P-type ATPases by the presence of six soluble N-terminal metal-binding domains containing a conserved CXXC metal-binding motif. The exact roles of these domains are not well established, but possible functions include exchanging copper with the metallochaperone Atox1 and mediating copper-responsive cellular relocalization. Although all six domains can bind copper, genetic and biochemical studies indicate that the domains are not functionally equivalent. One way the domains could be tuned to perform different functions is by having different affinities for Cu(I). We have used isothermal titration calorimetry to measure the association constant (K(a)) and stoichiometry (n) values of Cu(I) binding to the WND metal-binding domains and to their metallochaperone Atox1. The association constants for both the chaperone and target domains are approximately 10(5) to 10(6) m(-1), suggesting that the handling of copper by Atox1 and copper transfer between Atox1 and WND are under kinetic rather than thermodynamic control. Although some differences in both n and K(a) values are observed for variant proteins containing less than the full complement of six metal-binding domains, the data for domains 1-6 were best fitted with a single site model. Thus, the individual functions of the six WND metal-binding domains are not conferred by different Cu(I) affinities but instead by fold and electrostatic surface properties.
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PMID:Binding of copper(I) by the Wilson disease protein and its copper chaperone. 1470 53

Copper is essential for brain metabolism, serving as a cofactor to superoxide dismutase, dopamine-beta-hydroxylase, amyloid precursor protein, ceruloplasmin, and other proteins required for normal brain function. The copper-transporting ATPases ATP7A and ATP7B play a central role in distribution of copper in the central nervous system; genetic mutations in ATP7A and ATP7B lead to severe neurodegenerative disorders, Menkes disease and Wilson disease, respectively. Although both ATP7A and ATP7B are required, their specific roles and regulation in the brain remain poorly understood. Using high-resolution imaging and functional assays, we demonstrate that ATP7A and ATP7B show cell-specific distribution in adult cerebellum, have distinct enzymatic characteristics, and are regulated differently during development. ATP7B is continuously expressed in Purkinje neurons (PN) where it delivers copper to the ferroxidase ceruloplasmin. ATP7A is a faster copper transporter than Wilson disease protein as evidenced by faster rates of catalytic reactions. The expression of ATP7A switches during development from PN to Bergmann glia, the cells supporting PN function in adult brain. Inactivation of ATP7B (Wilson disease protein) by gene knock-out induces a striking shift in the expression of the ATP7B target protein, ceruloplasmin, from PN to Bergmann glia, where ATP7A (Menkes disease protein) is present. The induced cell-specific change in expression restores copper delivery to ceruloplasmin via ATP7A. Overall, the results provide evidence for distinct functions of ATP7A and ATP7B in the cerebellum and illustrate a tight link between copper homeostasis in PN and Bergmann glia.
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PMID:The copper-transporting ATPases, menkes and wilson disease proteins, have distinct roles in adult and developing cerebellum. 1563 71

Wilson's disease and Menkes disease are inherited genetic disorders of copper metabolism. Each disease results from the absence or dysfunction of homologous copper-transporting ATPases present in the trans-Golgi network of cells. The Wilson ATPase transports copper into the hepatocyte secretory pathway for incorporation into ceruloplasmin and excretion into the bile. Thus, patients with Wilson's disease of the autosomal recessive trait present with signs and symptoms arising from impaired biliary copper excretion. The Menkes ATPase transports copper across the placenta, gastrointestinal tract, and blood-brain barrier, and the clinical features of this X-linked disease arise from copper deficiency. Despite striking differences in the clinical presentation of these two diseases, the respective ATPases function in precisely the same fashion within the cell. The different clinical features of each disease are the results of the tissue specific expression of these ATPases. In Wilson's disease, impaired biliary copper excretion leads to accumulation of this metal in the liver. When the capacity for hepatic storage is exceeded, cell death ensues, with copper release into the plasma resulting in hemolysis and deposition of copper in extrahepatic tissues. Affected patients usually present in the first or second decade of life with chronic hepatitis and cirrhosis or acute liver failure. Copper accumulation in the cornea results in Kayser-Fleischer rings. Neuropsychiatric symptoms are more common in adults and include dystonia, tremor, personality changes, and cognitive impairment as a results of copper accumulation in the basal ganglia and other brain regions. The diagnosis of Wilson's disease is confirmed by decreased serum ceruloplasmin, increased urinary copper, and elevated hepatic copper concentration. A large number of different mutations occur in the genes of patients with Wilson disease. Copper chelation drugs and zinc are effective in most cases. New treatment guidelines now advise physicians to start patients on zinc.
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PMID:[Genetic disorders of copper transport--diagnosis and new treatment for the patients of Wilson's disease]. 1577 21


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