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.
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.
Colomer Gould
Veronica F
VF
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
Goti
Daniel
D
Pearce
Donna
D
Gonzalez
Guillermo A
GA
Gao
Hong
H
Bermudez de Leon
Mario
M
Jenkins
Nancy A
NA
Copeland
Neal G
NG
Ross
Christopher A
CA
Brown
Dale R
DR
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
D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D010446:Peptide Fragments; D012097:Repressor Proteins; C092341:ATXN3 protein, human; D000067699:Ataxin-3