Colomer Gould Veronica F, Goti Daniel, Pearce Donna, Gonzalez Guillermo A, Gao Hong, Bermudez de Leon Mario, Jenkins Nancy A, Copeland Neal G, Ross Christopher A, Brown Dale R
Department of Psychiatry, Johns Hopkins University School of Medicine, 600 N. Wolfe Street, Meyer Research Building, Room 4-158, Baltimore, MD 21287, USA.
Neurobiol Dis. 2007 Sep;27(3):362-9. doi: 10.1016/j.nbd.2007.06.005. Epub 2007 Jun 13.
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.
马查多 - 约瑟夫病又称3型脊髓小脑共济失调（MJD/SCA3），是一种由ataxin - 3多聚谷氨酰胺扩增（突变型ataxin - 3）引起的遗传性神经退行性运动障碍。MJD/SCA3中的神经元丢失与突变型ataxin - 3毒性片段有关。确定突变型ataxin - 3的蛋白水解位点可能有助于鉴定相应的酶。此前，我们在转基因小鼠（Q71）的大脑中报道了一个突变型ataxin - 3 mjd1a片段，该片段包含220位氨基酸C端的表位。在本研究中，我们构建并鉴定了表达缺失190 - 220位氨基酸的突变型ataxin - 3 mjd1a（deltaQ71）的神经母细胞瘤细胞和转基因小鼠。在细胞模型而非小鼠模型中检测到的deltaQ71片段比Q71片段少。转基因小鼠出现了类似MJD/SCA3的表型，其脑匀浆中有一个包含220位氨基酸C端表位的片段。我们的结果支持毒性片段假说，并将突变型ataxin - 3的切割位点缩小到190位氨基酸的N端。
