title: A mutant ataxin-3 fragment results from processing at a site N-terminal to amino acid 190 in brain of Machado-Joseph disease-like transgenic mice.
abstract: Machado-Joseph disease also called spinocerebellar ataxia type 3 (MJD/SCA3) is a hereditary and neurodegenerative movement disorder caused by ataxin-3 with a polyglutamine expansion (mutant ataxin-3). Neuronal loss in MJD/SCA3 is associated with a mutant ataxin-3 toxic fragment. Defining mutant ataxin-3 proteolytic site(s) could facilitate the identification of the corresponding enzyme(s). Previously, we reported a mutant ataxin-3 mjd1a fragment in the brain of transgenic mice (Q71) that contained epitopes C-terminal to amino acid 220. In this study, we generated and characterized neuroblastoma cells and transgenic mice expressing mutant ataxin-3 mjd1a lacking amino acids 190-220 (deltaQ71). Less deltaQ71 than Q71 fragments were detected in the cell but not mouse model. The transgenic mice developed an MJD/SCA3-like phenotype and their brain homogenates had a fragment containing epitopes C-terminal to amino acid 220. Our results support the toxic fragment hypothesis and narrow the mutant ataxin-3 cleavage site to the N-terminus of amino acid 190.
authors.affiliation: Department of Psychiatry, Johns Hopkins University School of Medicine, 600 N. Wolfe Street, Meyer Research Building, Room 4-158, Baltimore, MD 21287, USA. vcolomer@jhu.edu
authors.forename: Veronica F
authors.initials: VF
authors.lastname: Colomer Gould
authors.forename: Daniel
authors.initials: D
authors.lastname: Goti
authors.forename: Donna
authors.initials: D
authors.lastname: Pearce
authors.forename: Guillermo A
authors.initials: GA
authors.lastname: Gonzalez
authors.forename: Hong
authors.initials: H
authors.lastname: Gao
authors.forename: Mario
authors.initials: M
authors.lastname: Bermudez de Leon
authors.forename: Nancy A
authors.initials: NA
authors.lastname: Jenkins
authors.forename: Neal G
authors.initials: NG
authors.lastname: Copeland
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Ross
authors.forename: Dale R
authors.initials: DR
authors.lastname: Brown
mesh_terms: D000818:Animals; D000067699:Ataxin-3; D015153:Blotting, Western; D001921:Brain / Q000378:metabolism*; D004195:Disease Models, Animal; D006801:Humans; D017827:Machado-Joseph Disease / Q000235:genetics* / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism*; D014162:Transfection
chemical_list: D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D010446:Peptide Fragments; D012097:Repressor Proteins; C092341:ATXN3 protein, human; D000067699:Ataxin-3