title: Effect of Cysteamine on Mutant ASL Proteins with Cysteine for Arginine Substitutions.
abstract: BACKGROUND
  Cysteamine is used to treat cystinosis via the modification of cysteine residues substituting arginine in mutant proteins.
  
  
  OBJECTIVE
  We investigated the effect of cysteamine on mutant argininosuccinate lyase (ASL), the second most common defect in the urea cycle.
  
  
  METHODS
  In an established mammalian expression system, 293T cell lysates were produced after transfection with all known cysteine for arginine mutations in the ASL gene (p.Arg94Cys, p.Arg95Cys, p.Arg168Cys, p.Arg379Cys, and p.Arg385Cys), allowing testing of the effect of cysteamine over 48 h in the culture medium as well as for 1 h immediately prior to the enzyme assay.
  
  
  RESULTS
  Cysteamine at low concentrations showed no effect on 293T cell viability, ASL protein expression, or ASL activity when applied during cell culture. However, incubation of transfected cells with 0.05 mM cysteamine immediately before the enzyme assay resulted in increased ASL activity of p.Arg94Cys, p.Arg379Cys, and p.Arg385Cys by 64, 20, and 197 %, respectively, and this result was significant (p < 0.01). Cell lysates carrying p.Arg385Cys and treated with cysteamine recover enzyme activity that is similar to the untreated designed mutation p.Arg385Lys, providing circumstantial evidence for the assumed cysteamine-induced change of a cysteine to a lysine analogue.
  
  
  CONCLUSIONS
  Since 12 % of all known genotypes in ASL deficiency are affected by a cysteine for arginine mutation, we conclude that the potential of cysteamine or of related substances as remedy for this disease should be investigated further.
authors.affiliation: Division of Metabolism and Children's Research Centre (CRC), University Children's Hospital Zürich, Steinwiesstr. 75, 8032, Zurich, Switzerland.
authors.forename: Corinne
authors.initials: C
authors.lastname: Inauen
authors.affiliation: Division of Metabolism and Children's Research Centre (CRC), University Children's Hospital Zürich, Steinwiesstr. 75, 8032, Zurich, Switzerland.
authors.forename: Véronique
authors.initials: V
authors.lastname: Rüfenacht
authors.affiliation: Pediatric Endocrinology, University Children's Hospital and Department of Clinical Research, University of Bern, Bern, Switzerland.
authors.forename: Amit V
authors.initials: AV
authors.lastname: Pandey
authors.affiliation: Division of Metabolism and Children's Research Centre (CRC), University Children's Hospital Zürich, Steinwiesstr. 75, 8032, Zurich, Switzerland.|Affiliated with the Neuroscience Center Zürich (ZNZ), Zurich, Switzerland.
authors.forename: Liyan
authors.initials: L
authors.lastname: Hu
authors.affiliation: Department of General Pediatrics, Adolescent Medicine and Neonatology, University Medical Centre Freiburg, Freiburg, Germany.
authors.forename: Henk
authors.initials: H
authors.lastname: Blom
authors.affiliation: University Institute of Clinical Chemistry, University of Bern, Bern, Switzerland.|University Children's Hospital, University of Bern, Bern, Switzerland.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Nuoffer
authors.affiliation: Division of Metabolism and Children's Research Centre (CRC), University Children's Hospital Zürich, Steinwiesstr. 75, 8032, Zurich, Switzerland. johannes.haeberle@kispi.uzh.ch.|Affiliated with the Neuroscience Center Zürich (ZNZ), Zurich, Switzerland. johannes.haeberle@kispi.uzh.ch.|Affiliated with the Zürich Center for Integrative Human Physiology (ZIHP), Zurich, Switzerland. johannes.haeberle@kispi.uzh.ch.
authors.forename: Johannes
authors.initials: J
authors.lastname: Häberle
mesh_terms: D019943:Amino Acid Substitution / Q000187:drug effects*; D001120:Arginine / Q000378:metabolism*; D001123:Argininosuccinate Lyase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D003543:Cysteamine / Q000494:pharmacology*; D003545:Cysteine / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D057809:HEK293 Cells; D006801:Humans; D008239:Lysine / Q000378:metabolism; D008958:Models, Molecular; D062105:Molecular Docking Simulation
chemical_list: D003543:Cysteamine; D001120:Arginine; D001123:Argininosuccinate Lyase; D008239:Lysine; D003545:Cysteine