title: Diverse functional properties of Wilson disease ATP7B variants.
abstract: OBJECTIVE
  Wilson disease is a severe disorder of copper metabolism caused by mutations in ATP7B, which encodes a copper-transporting adenosine triphosphatase. The disease presents with a variable phenotype that complicates the diagnostic process and treatment. Little is known about the mechanisms that contribute to the different phenotypes of the disease.
  
  
  METHODS
  We analyzed 28 variants of ATP7B from patients with Wilson disease that affected different functional domains; the gene products were expressed using the baculovirus expression system in Sf9 cells. Protein function was analyzed by measuring catalytic activity and copper ((64)Cu) transport into vesicles. We studied intracellular localization of variants of ATP7B that had measurable transport activities and were tagged with green fluorescent protein in mammalian cells using confocal laser scanning microscopy.
  
  
  RESULTS
  Properties of ATP7B variants with pathogenic amino-acid substitution varied greatly even if substitutions were in the same functional domain. Some variants had complete loss of catalytic and transport activity, whereas others lost transport activity but retained phosphor-intermediate formation or had partial losses of activity. In mammalian cells, transport-competent variants differed in stability and subcellular localization.
  
  
  CONCLUSIONS
  Variants in ATP7B associated with Wilson disease disrupt the protein's transport activity, result in its mislocalization, and reduce its stability. Single assays are insufficient to accurately predict the effects of ATP7B variants the function of its product and development of Wilson disease. These findings will contribute to our understanding of genotype-phenotype correlation and mechanisms of disease pathogenesis.
authors.affiliation: Department of Medicine, Dermatology and Neurology, Division of Gastroenterology and Rheumatology, University of Leipzig, Leipzig, Germany. dominik.huster@diako-leipzig.de;
authors.forename: Dominik
authors.initials: D
authors.lastname: Huster
authors.forename: Angelika
authors.initials: A
authors.lastname: Kühne
authors.forename: Ashima
authors.initials: A
authors.lastname: Bhattacharjee
authors.forename: Lily
authors.initials: L
authors.lastname: Raines
authors.forename: Vanessa
authors.initials: V
authors.lastname: Jantsch
authors.forename: Johannes
authors.initials: J
authors.lastname: Noe
authors.forename: Wiebke
authors.initials: W
authors.lastname: Schirrmeister
authors.forename: Ines
authors.initials: I
authors.lastname: Sommerer
authors.forename: Osama
authors.initials: O
authors.lastname: Sabri
authors.forename: Frieder
authors.initials: F
authors.lastname: Berr
authors.forename: Joachim
authors.initials: J
authors.lastname: Mössner
authors.forename: Bruno
authors.initials: B
authors.lastname: Stieger
authors.forename: Karel
authors.initials: K
authors.lastname: Caca
authors.forename: Svetlana
authors.initials: S
authors.lastname: Lutsenko
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D016367:Baculoviridae / Q000201:enzymology / Q000235:genetics; D020134:Catalytic Domain; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D003300:Copper / Q000378:metabolism; D000073840:Copper-Transporting ATPases; D004795:Enzyme Stability; D020022:Genetic Predisposition to Disease; D005822:Genetic Vectors; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006527:Hepatolenticular Degeneration / Q000201:enzymology* / Q000235:genetics; D006801:Humans; D017136:Ion Transport; D007700:Kinetics; D018613:Microscopy, Confocal; D008958:Models, Molecular; D009154:Mutation; D010641:Phenotype; D010766:Phosphorylation; D011487:Protein Conformation; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship; D014162:Transfection
chemical_list: D027682:Cation Transport Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D003300:Copper; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; C000612464:ATP7B protein, human; D000073840:Copper-Transporting ATPases