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Michael L. Schilsky - One of the best experts on this subject based on the ideXlab platform.
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Wilson Disease and the Kidney
Genetic Diseases of the Kidney, 2020Co-Authors: Michael L. Schilsky, Pramod K. MistryAbstract:Publisher Summary Wilson Disease is a disorder of copper metabolism due to defective intracellular copper transport in hepatocytes. The mutant gene in Wilson Disease encodes a copper-transporting ATPase known as ATP7B that is mainly expressed in hepatocytes. Mutations that cause reduced function or absence of ATP7B reduce hepatic biliary copper excretion and cause hepatic copper accumulation. Nephrolithiasis may be found in some patients with Wilson Disease. This is most likely present in patients with tubular defects in acidification or resultant changes in the urinary excretion of substrates that augment stone formation. In the setting of either acute or severe chronic liver failure due to Wilson Disease, hepatorenal syndrome may develop. This entity is defined by the development of oliguria in association with reduced renal clearance and a low urine sodium excretion of ‹10 mEq/l that is unresponsive to volume expansion. Patients with acute liver failure due to Wilson Disease have a higher incidence of renal dysfunction compared to other etiologies of liver failure. Renal injury may occur not only from copper, but also from some of the treatments for Wilson Disease. Most commonly, the copper-chelating drug, d-penicillamine, may cause acute or later-onset renal toxicity. A syndrome with lupus nephritis may occur early on, associated with the appearance of cellular elements in the urinary sediment and renal injury. Proteinuria of varying degrees may occur even years following the initiation of therapy with d-penicillamine. Within the first 2 years of therapy, low-molecular-weight proteins are found in the urine, suggesting tubular injury.
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Patient support groups in the management of Wilson Disease.
Handbook of Clinical Neurology, 2020Co-Authors: Mary L. Graper, Michael L. SchilskyAbstract:Patient support groups serve an important function for those affected by a Disease but especially for people with a rare Disease. Because of the complexity of Wilson Disease there are some unique and difficult problems faced by groups that advocate for these patients. We give a comparative overview of the differences between groups that support people with more common Diseases and groups that serve the rare Disease population. The history and current status of the Wilson Disease Association and other worldwide Wilson Disease groups are described and information about other organizations that support Wilson Disease in additional ways is explained. The specific challenges faced in the support of Wilson Disease patients are outlined and possible solutions proposed. Drawing from experience in speaking with many patients, we discuss some of the most common questions that are asked by patients who are seeking a possible diagnosis or are already on treatment. There are many options for improving patient advocacy efforts in the future that we hope will be accomplished.
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Wilson Disease diagnosis treatment and follow up
Clinics in Liver Disease, 2017Co-Authors: Michael L. SchilskyAbstract:: Consideration of a diagnosis of Wilson Disease is still the critical factor in testing for and establishing Disease diagnosis. In association with other clinical and biochemical tests, liver biopsy results and molecular genetic testing can also be used to generate a score for diagnosing Wilson Disease. Medical therapy is effective for most patients; liver transplant can rescue those with acute liver failure or those with advanced liver Disease who fail to respond to or discontinue medical therapy. Treatment monitoring must be done at regular intervals and includes clinical evaluation, liver tests and blood counts, and copper metabolic parameters.
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Wilson Disease pathogenesis and clinical considerations in diagnosis and treatment
Seminars in Liver Disease, 2011Co-Authors: Richard Rosencrantz, Michael L. SchilskyAbstract:: Nearly a century after Dr. Samuel Alexander Kinnier Wilson composed his doctoral thesis on the pathologic findings of "lenticular degeneration" in the brain associated with cirrhosis of the liver we know that the underlying molecular basis for this autosomal recessive inherited disorder that now bears his name is mutation of a copper transporting ATPase, ATP7B, an intracellular copper transporter mainly expressed in hepatocytes. Loss of ATP7B function is the basis for reduced hepatic biliary copper excretion and reduced incorporation of copper into ceruloplasmin. During the intervening years, there was recognition of the clinical signs, histologic, biochemical features, and mutation analysis of ATP7B that characterize and enable diagnosis of this disorder. These include the presence of signs of liver or neurologic Disease and detection of Kayser-Fleischer rings, low ceruloplasmin, elevated urine and hepatic copper, and associated histologic changes in the liver. Medical therapies and liver transplantation can effectively treat patients with this once uniformly fatal disorder. The earlier detection of the Disease led to the initiation of treatment to prevent Disease progression and reverse pathologic findings if present, and family screening to detect the disorder in first-degree relatives is warranted. Gene therapy and hepatocyte cell transplantation for Wilson Disease has only been tested in animal models but represent future areas for study. Despite all the advances we still have to consider the diagnosis of Wilson Disease to test patients for this disorder and properly establish the diagnosis before committing to life-long treatment.
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liver transplantation for children with Wilson Disease comparison of outcomes between children and adults
Clinical Transplantation, 2011Co-Authors: Michael L. Schilsky, Ronen Arnon, Rachel A Annunziato, Tamir Miloh, Asha Willis, Mark Sturdevant, Arnond SakworawichAbstract:Arnon R, Annunziato R, Schilsky M, Miloh T, Willis A, Sturdevant M, Sakworawich A, Suchy F, Kerkar N. Liver transplantation for children with Wilson Disease: comparison of outcomes between children and adults. Clin Transplant 2011: 25: E52–E60. © 2010 John Wiley & Sons A/S. Abstract: Liver transplantation (LT) is lifesaving for patients with Wilson Disease (WD) presenting with fulminant hepatic failure (FHF) or chronic liver Disease (CLD) unresponsive to treatment. Aim: To determine the outcome of LT in pediatric and adult patients with WD. Methods: United Network for Organ Sharing data on LT from 1987 to 2008 were analyzed. Outcomes were compared for patients requiring LT for FHF and CLD after 2002. Multivariate logistic regression was used to determine risk factors for death and graft loss. Results: Of 90 867 patients transplanted between 1987 and 2008, 170 children and 400 adults had WD. The one- and five-yr patient survival of children was 90.1% and 89% compared to 88.3% and 86% for adults, p = 0.53, 0.34. After 2002, 103 (41 children) were transplanted for FHF and 67 (10 children) for CLD. One- and five-yr patient survival was higher in children transplanted for CLD compared to FHF; 100%, 100% vs. 90%, 87.5% respectively, p = 0.30, 0.32. One- and five-yr patient survival was higher in adults transplanted for CLD compared to FHF; 94.7%, 90.1% vs. 90.3%, 89.7%, respectively, p = 0.36, 0.88. Encephalopathy, partial graft, and ventilator use were risk factors for death by logistic regression. Conclusion: LT is an excellent treatment option for patients with WD. Patients transplanted for CLD had higher patient survival rates than patients with FHF.
Svetlana Lutsenko - One of the best experts on this subject based on the ideXlab platform.
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human copper transporter atp7b Wilson Disease protein forms stable dimers in vitro and in cells
Journal of Biological Chemistry, 2017Co-Authors: Samuel Jayakanthan, Lelita T Braiterman, Nesrin M Hasan, Vinzenz M Unger, Svetlana LutsenkoAbstract:Abstract ATP7B is a copper-transporting P1B-type ATPase (Cu-ATPase) with an essential role in human physiology. Mutations in ATP7B cause the potentially fatal Wilson Disease, and changes in ATP7B expression are observed in several cancers. Despite its physiologic importance, the biochemical information about ATP7B remains limited because of a complex multidomain organization of the protein. By analogy with the better characterized prokaryotic Cu-ATPases, ATP7B is assumed to be a single-chain monomer. We show that in eukaryotic cells, human ATP7B forms dimers that can be purified following solubilization. Deletion of the four N-terminal metal-binding domains, characteristic for human ATP7B, does not disrupt dimerization, i.e. the dimer interface is formed by the domains that are conserved among Cu-ATPases. Unlike the full-length ATP7B, which is targeted to the trans-Golgi network, 1–4ΔMBD-7B is targeted primarily to vesicles. This result and the analysis of differentially tagged ATP7B variants indicate that the dimeric structure is retained during ATP7B trafficking between the intracellular compartments. Purified dimeric species of 1–4ΔMBD-7B were characterized by a negative stain electron microscopy in the presence of ADP/MgCl2. Single-particle analysis yielded a low-resolution 3D model that provides the first insight into an overall architecture of a human Cu-ATPase, positions of the main domains, and a dimer interface.
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distinct phenotype of a Wilson Disease mutation reveals a novel trafficking determinant in the copper transporter atp7b
Proceedings of the National Academy of Sciences of the United States of America, 2014Co-Authors: Lelita T Braiterman, Svetlana Lutsenko, Samuel Jayakanthan, Amrutha Murthy, Lydia Nyasae, Eric Tzeng, Grazyna Gromadzka, Thomas B Woolf, Ann Louise HubbardAbstract:Wilson Disease (WD) is a monogenic autosomal-recessive disorder of copper accumulation that leads to liver failure and/or neurological deficits. WD is caused by mutations in ATP7B, a transporter that loads Cu(I) onto newly synthesized cupro-enzymes in the trans-Golgi network (TGN) and exports excess copper out of cells by trafficking from the TGN to the plasma membrane. To date, most WD mutations have been shown to disrupt ATP7B activity and/or stability. Using a multidisciplinary approach, including clinical analysis of patients, cell-based assays, and computational studies, we characterized a patient mutation, ATP7BS653Y, which is stable, does not disrupt Cu(I) transport, yet renders the protein unable to exit the TGN. Bulky or charged substitutions at position 653 mimic the phenotype of the patient mutation. Molecular modeling and dynamic simulation suggest that the S653Y mutation induces local distortions within the transmembrane (TM) domain 1 and alter TM1 interaction with TM2. S653Y abolishes the trafficking-stimulating effects of a secondary mutation in the N-terminal apical targeting domain. This result indicates a role for TM1/TM2 in regulating conformations of cytosolic domains involved in ATP7B trafficking. Taken together, our experiments revealed an unexpected role for TM1/TM2 in copper-regulated trafficking of ATP7B and defined a unique class of WD mutants that are transport-competent but trafficking-defective. Understanding the precise consequences of WD-causing mutations will facilitate the development of advanced mutation-specific therapies.
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near infrared fluorescent sensor for in vivo copper imaging in a murine Wilson Disease model
Proceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: Tasuku Hirayama, Svetlana Lutsenko, Genevieve C Van De Bittner, Lawrence W Gray, Christopher J ChangAbstract:Copper is an essential metal nutrient that is tightly regulated in the body because loss of its homeostasis is connected to severe Diseases such as Menkes and Wilson Diseases, Alzheimer’s Disease, prion disorders, and amyotrophic lateral sclerosis. The complex relationships between copper status and various stages of health and Disease remain challenging to elucidate, in part due to a lack of methods for monitoring dynamic changes in copper pools in whole living organisms. Here we present the synthesis, spectroscopy, and in vivo imaging applications of Coppersensor 790, a first-generation fluorescent sensor for visualizing labile copper pools in living animals. Coppersensor 790 combines a near-infrared emitting cyanine dye with a sulfur-rich receptor to provide a selective and sensitive turn-on response to copper. This probe is capable of monitoring fluctuations in exchangeable copper stores in living cells and mice under basal conditions, as well as in situations of copper overload or deficiency. Moreover, we demonstrate the utility of this unique chemical tool to detect aberrant increases in labile copper levels in a murine model of Wilson Disease, a genetic disorder that is characterized by accumulation of excess copper. The ability to monitor real-time copper fluxes in living animals offers potentially rich opportunities to examine copper physiology in health and Disease.
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cellular copper levels determine the phenotype of the arg875 variant of atp7b Wilson Disease protein
Proceedings of the National Academy of Sciences of the United States of America, 2011Co-Authors: Arnab Gupta, Oleg Y Dmitriev, Lelita T Braiterman, Ashima Bhattacharjee, Sergiy Nokhrin, Ann Louise Hubbard, Svetlana LutsenkoAbstract:In human disorders, the genotype-phenotype relationships are often complex and influenced by genetic and/or environmental factors. Wilson Disease (WD) is a monogenic disorder caused by mutations in the copper-transporting P-type ATPase ATP7B. WD shows significant phenotypic diversity even in patients carrying identical mutations; the basis for such diverse manifestations is unknown. We demonstrate that the 2623A/G polymorphism (producing the Gly875→Arg substitution in the A-domain of ATP7B) drastically alters the intracellular properties of ATP7B, whereas copper reverses the effects. Under basal conditions, the common Gly875 variant of ATP7B is targeted to the trans-Golgi network (TGN) and transports copper into the TGN lumen. In contrast, the Arg875 variant is located in the endoplasmic reticulum (ER) and does not deliver copper to the TGN. Elevated copper corrects the ATP7B-Arg875 phenotype. Addition of only 0.5–5 μM copper triggers the exit of ATP7B-Arg875 from the ER and restores copper delivery to the TGN. Analysis of the recombinant A-domains by NMR suggests that the ER retention of ATP7B-Arg875 is attributable to increased unfolding of the Arg875-containing A-domain. Copper is not required for the folding of ATP7B-Arg875 during biosynthesis, but it stabilizes protein and stimulates its activity. A chemotherapeutical drug, cisplatin, that mimics a copper-bound state of ATP7B also corrects the “Disease-like” phenotype of ATP7B-Arg875 and promotes its TGN targeting and transport function. We conclude that in populations harboring the Arg875 polymorphism, the levels of bioavailable copper may play a vital role in the manifestations of WD.
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Wilson Disease at a single cell level intracellular copper trafficking activates compartment specific responses in hepatocytes
Journal of Biological Chemistry, 2010Co-Authors: Martina Ralle, Dominik Huster, Jason L Burkhead, Lawrence W Gray, Stefan Vogt, Wiebke Schirrmeister, Tony R Capps, Edward B Maryon, Svetlana LutsenkoAbstract:Wilson Disease (WD) is a severe hepato-neurologic disorder that affects primarily children and young adults. WD is caused by mutations in ATP7B and subsequent copper overload. However, copper levels alone do not predict severity of the Disease. We demonstrate that temporal and spatial distribution of copper in hepatocytes may play an important role in WD pathology. High resolution synchrotron-based x-ray fluorescence imaging in situ indicates that copper does not continuously accumulate in Atp7b−/− hepatocytes, but reaches a limit at 90–300 fmol. The lack of further accumulation is associated with the loss of copper transporter Ctr1 from the plasma membrane and the appearance of copper-loaded lymphocytes and extracellular copper deposits. The WD progression is characterized by changes in subcellular copper localization and transcriptome remodeling. The synchrotron-based x-ray fluorescence imaging and mRNA profiling both point to the key role of nucleus in the initial response to copper overload and suggest time-dependent sequestration of copper in deposits as a protective mechanism. The metabolic pathways, up-regulated in response to copper, show compartmentalization that parallels changes in subcellular copper concentration. In contrast, significant down-regulation of lipid metabolism is observed at all stages of WD irrespective of copper distribution. These observations suggest new stage-specific as well as general biomarkers for WD. The model for the dynamic role of copper in WD is proposed.
John R Forbes - One of the best experts on this subject based on the ideXlab platform.
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copper dependent trafficking of Wilson Disease mutant atp7b proteins
Human Molecular Genetics, 2000Co-Authors: John R ForbesAbstract:: We have previously developed a functional assay in yeast for the copper transporter, ATP7B, defective in Wilson Disease (WND). Analysis of WND variant ATP7B proteins revealed that several were able to completely, or nearly completely, complement a mutant yeast strain in which the ATP7B ortholog CCC2 was disrupted, indicating that these ATP7B proteins retained copper transport activity. We analyzed the intracellular localization of these active WND ATP7B variant proteins using transient transfection of Chinese hamster ovary cells and triple-label immunofluorescence microscopy, as a second possible aspect of defective function. Two ATP7B variants, Asp765Asn and Leu776Val, which have normal copper transport activity in yeast, retained partial normal Golgi network localization, but were predominantly mislocalized throughout the cell. Asp765Asn and Leu776Val proteins were capable of only partial copper-dependent redistribution. WND variant protein Arg778Leu, which has defective function in yeast, was extensively mislocalized, presumably to the endoplasmic reticulum. ATP7B variant proteins Gly943Ser, which has nearly normal function in yeast, and CysProCys/Ser (mutation of the conserved CysProCys motif to SerProSer), inactive in yeast, were localized normally but were unable to redistribute in response to copper. Localization data from this study, combined with functional data from our yeast studies, provide a biochemical mechanism that can explain in part the variable biochemical features of WND, in particular the normal holo-ceruloplasmin levels observed in some patients. Our data have direct implications for WND diagnosis, indicating that decreased serum ceruloplasmin concentration is not likely to be observed with certain genetic variants of WND.
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the Wilson Disease gene spectrum of mutations and their consequences
Nature Genetics, 1995Co-Authors: Gordon R Thomas, John R Forbes, Eve A Roberts, John M. WalsheAbstract:We have previously reported the cloning of a gene that encodes a copper transporting P–type ATPase (ATP7B) which is defective in Wilson Disease. We have now identified in 58 WND patients, 20 new mutations as well as three of five previously published mutations: 11 small insertions and deletions, seven missense, two nonsense and three splice site mutations. Two of the mutations are relatively frequent, representing 38% of the mutations in patients of European origin. Our findings suggest a wider spectrum of age of onset than is considered typical of Wilson Disease: mutations that completely disrupt the gene can produce liver Disease in early childhood when Wilson Disease may not typically considered in the differential diagnosis. The mutations identified provide an explanation for at least part of the wide phenotypic variation observed in Wilson Disease.
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the lec rat has a deletion in the copper transporting atpase gene homologous to the Wilson Disease gene
Nature Genetics, 1994Co-Authors: Jingshi Wu, John R Forbes, Hai Shiene ChenAbstract:The Long–Evans Cinnamon (LEC) rat shows similarity to Wilson Disease in many clinical and biochemical features. We have cloned cDNAs for the rat gene (Atp7b) homologous to the human Wilson Disease gene (ATP7B) and have used them to identify a partial deletion in the Atp7b gene in the LEC rat. The deletion removes at least 900 bp of the coding region at the 3′ end, includes the crucial ATP binding domain and extends downstream of the gene. Our results provide convincing evidence for defining the LEC rat as an animal model for Wilson Disease. This model will be important for studying liver pathophysiology, for developing therapy for Wilson Disease and for studying the pathway of copper transport and its possible interaction with other heavy metals.
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The Wilson Disease gene is a putative copper transporting P–type ATPase similar to the Menkes gene
Nature Genetics, 1993Co-Authors: Peter C. Bull, Gordon R Thomas, Johanna M. Rommens, John R ForbesAbstract:Wilson Disease (WD) is an autosomal recessive disorder of copper transport, resulting in copper accumulation and toxicity to the liver and brain. The gene ( WD ) has been mapped to chromosome 13 q14.3. On yeast artificial chromosomes from this region we have identified a sequence, similar to that coding for the proposed copper binding regions of the putative ATPase gene ( MNK ) defective in Menkes Disease. We show that this sequence forms part of a P–type ATPase gene (referred to here as Wc1 ) that is very similar to MNK , with six putative metal binding regions similar to those found in prokaryotic heavy metal transporters. The gene, expressed in liver and kidney, lies within a 300 kb region likely to include the WD locus. Two WD patients were found to be homozygous for a seven base deletion within the coding region of Wc1 . Wc1 is proposed as the gene for WD.
Dominik Huster - One of the best experts on this subject based on the ideXlab platform.
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activation of liver x receptor retinoid x receptor pathway ameliorates liver Disease in atp7b Wilson Disease mice
Hepatology, 2016Co-Authors: James P Hamilton, Uta Merle, Dominik Huster, Lahari Koganti, Abigael Muchenditsi, Venkata S Pendyala, David L Huso, Joseph A Hankin, Robert C Murphy, Christopher MangelsAbstract:UNLABELLED: Wilson Disease (WD) is a hepatoneurological disorder caused by mutations in the copper-transporter, ATP7B. Copper accumulation in the liver is a hallmark of WD. Current therapy is based on copper chelation, which decreases the manifestations of liver Disease, but often worsens neurological symptoms. We demonstrate that in Atp7b(-/-) mice, an animal model of WD, liver function can be significantly improved without copper chelation. Analysis of transcriptional and metabolic changes in samples from WD patients and Atp7b(-/-) mice identified dysregulation of nuclear receptors (NRs), especially the liver X receptor (LXR)/retinoid X receptor heterodimer, as an important event in WD pathogenesis. Treating Atp7b(-/-) mice with the LXR agonist, T0901317, ameliorated Disease manifestations despite significant copper overload. Genetic markers of liver fibrosis and inflammatory cytokines were significantly decreased, lipid profiles normalized, and liver function and histology were improved. CONCLUSIONS: The results demonstrate the major role of an altered NR function in the pathogenesis of WD and suggest that modulation of NR activity should be explored as a supplementary approach to improving liver function in WD. (Hepatology 2016;63:1828-1841).
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diverse functional properties of Wilson Disease atp7b variants
Gastroenterology, 2012Co-Authors: Dominik Huster, Wiebke Schirrmeister, Ashima Bhattacharjee, Angelika Kuhne, Lily Raines, Vanessa Jantsch, Ines SommererAbstract:Wilson Disease (WD) is a hereditary Disease due to mutations of the copper-transporting P-type adenosine triphosphatase (ATPase) ATP7B. WD is associated with copper accumulation resulting in liver damage and/or neurologic symptoms.1,2 The manifestations of liver Disease vary from clinically asymptomatic with only biochemical abnormalities, to acute liver failure.3 Similarly, the spectrum of neurologic manifestations ranges from normal or mild disturbances to a rapid and severe progression of neurologic disability.4 The mechanisms behind this variability are likely to be complex because even monozygotic twins can have different Disease manifestations.5 Genetic studies showed some association between several mutations and the age of onset/Disease severity6–9; however, robust genotype–phenotype correlation in the case of missense mutations has not been found so far, although complete loss of protein expression due to non–sense mutations is expected to result in a more severe phenotype. This study focuses on one potential source of phenotypic variability—the effect of mutations in ATP7B on the function of the corresponding Cu-transporting Wilson ATPase. To date, >500 different mutations associated with WD are known (http://www.WilsonDisease.med.ualberta.ca/database.asp).10 The high prevalence of compound heterozygosity prevents a clear correlation between genotype and phenotype in affected individuals. A large fraction of mutations are missense mutations producing a single amino-acid change in Wilson ATPase ATP7B. ATP7B is a large membrane protein located in the trans-Golgi network (TGN). In normal liver, ATP7B has these 2 functions: it transports copper into the TGN for incorporation into ceruloplasmin and exports excess copper by sequestering metal in vesicles for subsequent biliary excretion. The second function requires ATP7B trafficking from TGN to endocytic vesicles in response to elevation of intracellular copper concentration. The ATP7B-mediated transport of copper involves several steps. First, ATP7B binds copper via its cytosolic N-terminal domain and ATP via the nucleotide-binding domain. ATP is then hydrolyzed, and ATP7B becomes transiently phosphorylated at the residue D1027 located in the P-domain (catalytic phosphorylation). Subsequent dephosphorylation releases energy necessary to transfer copper across membrane (transport step) (Figure 1A and B). Each of these steps can be affected by WD-causing mutations.11 The effect could be severe, resulting in complete loss of ATP7B function, if mutated residues are critical for binding of ATP or copper and/or conformational transitions during catalysis. The inactivation of ATP7B could also be partial if mutations diminish affinity for substrates, slow down conformational transitions, or interfere with precise protein targeting to TGN or vesicles. Understanding of phenotypic diversity in WD requires knowledge of how causative mutations alter protein stability, activity, and localization in the cell. Figure 1 (A) Catalytic cycle of ATP7B (the dotted frame highlights partial reactions, relevant for this study). (B) Transmembrane organization of ATP7B and representation of mutants and variants examined in this study. The 6 metal-binding sites in the N-terminal ... Presently, for most of the WD-causing mutations, such detailed information is not available. Yeast complementation assay was used to segregate ATP7B mutants into severe and mild categories based on their ability to restore the growth of yeast strain that lacks the endogenous copper transporter.12–14 Studies in mammalian cells revealed decreased protein levels and mislocalization for several mutants,15–17 with a surprisingly small effect on copper transport, which was evaluated indirectly.17 So far, no studies have directly assessed the transport or catalytic activity of Disease-causing mutants. Such information is necessary for future mechanism-based attempts to correct the ATP7B function. Here, we directly measured catalytic and transport activity of 28 ATP7B variants representing all protein domains (Table 1, Figure 1B) and tested the intracellular localization for mutants, for which transport activity was observed. The mutants and variants were chosen based on clinical findings (see WD database10) and recent literature; gene variants found in the population with no WD symptoms were also characterized. Table 1 Copper Transport and Phosphorylation Activity of Wild-Type, Mutant, and Variant ATP7B
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Wilson Disease at a single cell level intracellular copper trafficking activates compartment specific responses in hepatocytes
Journal of Biological Chemistry, 2010Co-Authors: Martina Ralle, Dominik Huster, Jason L Burkhead, Lawrence W Gray, Stefan Vogt, Wiebke Schirrmeister, Tony R Capps, Edward B Maryon, Svetlana LutsenkoAbstract:Wilson Disease (WD) is a severe hepato-neurologic disorder that affects primarily children and young adults. WD is caused by mutations in ATP7B and subsequent copper overload. However, copper levels alone do not predict severity of the Disease. We demonstrate that temporal and spatial distribution of copper in hepatocytes may play an important role in WD pathology. High resolution synchrotron-based x-ray fluorescence imaging in situ indicates that copper does not continuously accumulate in Atp7b−/− hepatocytes, but reaches a limit at 90–300 fmol. The lack of further accumulation is associated with the loss of copper transporter Ctr1 from the plasma membrane and the appearance of copper-loaded lymphocytes and extracellular copper deposits. The WD progression is characterized by changes in subcellular copper localization and transcriptome remodeling. The synchrotron-based x-ray fluorescence imaging and mRNA profiling both point to the key role of nucleus in the initial response to copper overload and suggest time-dependent sequestration of copper in deposits as a protective mechanism. The metabolic pathways, up-regulated in response to copper, show compartmentalization that parallels changes in subcellular copper concentration. In contrast, significant down-regulation of lipid metabolism is observed at all stages of WD irrespective of copper distribution. These observations suggest new stage-specific as well as general biomarkers for WD. The model for the dynamic role of copper in WD is proposed.
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high copper selectively alters lipid metabolism and cell cycle machinery in the mouse model of Wilson Disease
Journal of Biological Chemistry, 2007Co-Authors: Dominik Huster, Jason L Burkhead, Tina Purnat, Martina Ralle, Oliver Fiehn, Franziska Stuckert, Erik N Olson, Daniel Teupser, Svetlana LutsenkoAbstract:Abstract Copper is essential for human physiology, but in excess it causes the severe metabolic disorder Wilson Disease. Elevated copper is thought to induce pathological changes in tissues by stimulating the production of reactive oxygen species that damage multiple cell targets. To better understand the molecular basis of this Disease, we performed genome-wide mRNA profiling as well as protein and metabolite analysis for Atp7b-/- mice, an animal model of Wilson Disease. We found that at the presymptomatic stages of the Disease, copper-induced changes are inconsistent with widespread radical-mediated damage, which is likely due to the sequestration of cytosolic copper by metallothioneins that are markedly up-regulated in Atp7b-/- livers. Instead, copper selectively up-regulates molecular machinery associated with the cell cycle and chromatin structure and down-regulates lipid metabolism, particularly cholesterol biosynthesis. Specific changes in the transcriptome are accompanied by distinct metabolic changes. Biochemical and mass spectroscopy measurements revealed a 3.6-fold decrease of very low density lipoprotein cholesterol in serum and a 33% decrease of liver cholesterol, indicative of a marked decrease in cholesterol biosynthesis. Consistent with low cholesterol levels, the amount of activated sterol regulatory-binding protein 2 (SREBP-2) is increased in Atp7b-/- nuclei. However, the SREBP-2 target genes are dysregulated suggesting that elevated copper alters SREBP-2 function rather than its processing or re-localization. Thus, in Atp7b-/- mice elevated copper affects specific cellular targets at the transcription and/or translation levels and has distinct effects on liver metabolic function, prior to appearance of histopathological changes. The identification of the network of specific copper-responsive targets facilitates further mechanistic analysis of human disorders of copper misbalance.
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consequences of copper accumulation in the livers of the atp7b Wilson Disease gene knockout mice
American Journal of Pathology, 2006Co-Authors: Dominik Huster, Milton J Finegold, Clinton T Morgan, Jason L Burkhead, Randal R Nixon, Scott M Vanderwerf, Conrad T Gilliam, Svetlana LutsenkoAbstract:Wilson Disease is a severe genetic disorder associated with intracellular copper overload. The affected gene, ATP7B, has been identified, but the molecular events leading to Wilson Disease remain poorly understood. Here, we demonstrate that genetically engineered Atp7b−/− mice represent a valuable model for dissecting the Disease mechanisms. These mice, like Wilson Disease patients, have intracellular copper accumulation, low-serum oxidase activity, and increased copper excretion in urine. Their liver pathology developed in stages and was determined by the time of exposure to elevated copper rather than copper concentration per se. The Disease progressed from mild necrosis and inflammation to extreme hepatocellular injury, nodular regeneration, and bile duct proliferation. Remarkably, all animals older than 9 months showed regeneration of large portions of the liver accompanied by the localized occurrence of cholangiocarcinoma arising from the proliferating bile ducts. The biochemical characterization of Atp7b−/− livers revealed copper accumulation in several cell compartments, particularly in the cytosol and nuclei. The increase in nuclear copper is accompanied by marked enlargement of the nuclei and enhanced DNA synthesis, with these changes occurring before pathology development. Our results suggest that the early effects of copper on cell genetic material contribute significantly to pathology associated with Atp7b inactivation.
Peter C. Bull - One of the best experts on this subject based on the ideXlab platform.
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Mapping of the mouse homologue of the Wilson Disease gene to mouse chromosome 8
Genomics, 1995Co-Authors: Vivienne Reed, Penny Williamson, Peter C. Bull, Yvonne BoydAbstract:ATP7B, the gene altered in Wilson Disease (WD) patients, lies in a block of homology shared between human chromosome 13q14 and the central region of mouse chromosome 14. However, we have mapped the murine homologue of ATP7B (Atp7b) to mouse chromosome 8 by somatic cell hybrid analysis. Analysis of 80 interspecific backcross offspring was used to position Atp7b close to D8Mit3 and another ATPase locus, Atp4b, on mouse chromosome 8. ATP4B lies in 13q34 and is separated from ATP7B by several loci whose mouse homologues map to mouse chromosome 14. The assignment of Atp7b to mouse chromosome 8 identifies a previously unrecognized region of homology between this chromosome and human chromosome 13. This assignment suggests a possible location for the toxic milk mutation in the mouse, which has been proposed as a homologue of WD.
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Wilson Disease and menkes Disease new handles on heavy metal transport
Trends in Genetics, 1994Co-Authors: Peter C. Bull, Diane W CoxAbstract:Abstract 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 remarkebly 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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The Wilson Disease gene is a putative copper transporting P–type ATPase similar to the Menkes gene
Nature Genetics, 1993Co-Authors: Peter C. Bull, Gordon R Thomas, Johanna M. Rommens, John R ForbesAbstract:Wilson Disease (WD) is an autosomal recessive disorder of copper transport, resulting in copper accumulation and toxicity to the liver and brain. The gene ( WD ) has been mapped to chromosome 13 q14.3. On yeast artificial chromosomes from this region we have identified a sequence, similar to that coding for the proposed copper binding regions of the putative ATPase gene ( MNK ) defective in Menkes Disease. We show that this sequence forms part of a P–type ATPase gene (referred to here as Wc1 ) that is very similar to MNK , with six putative metal binding regions similar to those found in prokaryotic heavy metal transporters. The gene, expressed in liver and kidney, lies within a 300 kb region likely to include the WD locus. Two WD patients were found to be homozygous for a seven base deletion within the coding region of Wc1 . Wc1 is proposed as the gene for WD.
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the Wilson Disease gene is a putative copper transporting p type atpase similar to the menkes gene
Nature Genetics, 1993Co-Authors: Peter C. Bull, Gordon R Thomas, Johanna M. RommensAbstract:Wilson Disease (WD) is an autosomal recessive disorder of copper transport, resulting in copper accumulation and toxicity to the liver and brain. The gene (WD) has been mapped to chromosome 13 q14.3. On yeast artificial chromosomes from this region we have identified a sequence, similar to that coding for the proposed copper binding regions of the putative ATPase gene (MNK) defective in Menkes Disease. We show that this sequence forms part of a P–type ATPase gene (referred to here as Wc1) that is very similar to MNK, with six putative metal binding regions similar to those found in prokaryotic heavy metal transporters. The gene, expressed in liver and kidney, lies within a 300 kb region likely to include the WD locus. Two WD patients were found to be homozygous for a seven base deletion within the coding region of Wc1. Wc1 is proposed as the gene for WD.
