title: Mutations in PNKD causing paroxysmal dyskinesia alters protein cleavage and stability.
abstract: Paroxysmal non-kinesigenic dyskinesia (PNKD) is a rare autosomal dominant movement disorder triggered by stress, fatigue or consumption of either alcohol or caffeine. Attacks last 1-4 h and consist of dramatic dystonia and choreoathetosis in the limbs, trunk and face. The disease is associated with single amino acid changes (A7V or A9V) in PNKD, a protein of unknown function. Here we studied the stability, cellular localization and enzymatic activity of the PNKD protein in cultured cells and transgenic animals. The N-terminus of the wild-type (WT) long PNKD isoform (PNKD-L) undergoes a cleavage event in vitro, resistance to which is conferred by disease-associated mutations. Mutant PNKD-L protein is degraded faster than the WT protein. These results suggest that the disease mutations underlying PNKD may disrupt protein processing in vivo, a hypothesis supported by our observation of decreased cortical Pnkd-L levels in mutant transgenic mice. Pnkd is homologous to a superfamily of enzymes with conserved β-lactamase domains. It shares highest homology with glyoxalase II but does not catalyze the same reaction. Lower glutathione levels were found in cortex lysates from Pnkd knockout mice versus WT littermates. Taken together, our results suggest an important role for the Pnkd protein in maintaining cellular redox status.
authors.affiliation: Department of Neurology, University of California at San Francisco, San Francisco, CA 94158, USA.
authors.forename: Yiguo
authors.initials: Y
authors.lastname: Shen
authors.forename: Hsien-Yang
authors.initials: HY
authors.lastname: Lee
authors.forename: Joel
authors.initials: J
authors.lastname: Rawson
authors.forename: Sunil
authors.initials: S
authors.lastname: Ojha
authors.forename: Patricia
authors.initials: P
authors.lastname: Babbitt
authors.forename: Ying-Hui
authors.initials: YH
authors.lastname: Fu
authors.forename: Louis J
authors.initials: LJ
authors.lastname: Ptácek
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D002819:Chorea / Q000235:genetics*; D004330:Drosophila; D005455:Fluorescent Antibody Technique; D047468:Immunoprecipitation; D008156:Luciferases; D051379:Mice; D008822:Mice, Transgenic; D009124:Muscle Proteins / Q000235:genetics* / Q000378:metabolism*; D020125:Mutation, Missense / Q000235:genetics; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D001618:beta-Lactamases / Q000235:genetics
chemical_list: D009124:Muscle Proteins; C495444:PNKD protein, human; D008156:Luciferases; D001618:beta-Lactamases