Decreased protein synthesis of Hsp27 associated with cellular toxicity in a cell model of Machado-Joseph disease.
Machado-Joseph disease is an autosomal dominant spinocerebellar degeneration caused by the expansion of a polyglutamine tract within the gene product, ataxin-3. We have previously shown that increased oxidative stress and decreased expression of Hsp27 may be contributory factors to the disease progression. In this study, we utilized neuroblastoma SK-N-SH cells stably transfected with full-length expanded ataxin-3 to further investigate the mechanism(s) resulting in the decreased expression of Hsp27. Results from 35S-methionine pulse-chase labeling and protein degradation assays revealed that decreased Hsp27 in mutant MJD cells is due to defects in protein synthesis. Our results further demonstrated that Hsp27 degradation is independent of the proteasome degradation pathway. In addition, we showed that overexpression of Hsp27 desensitizes mutant MJD cells to apoptotic stress. Taken together, these findings provide the first evidence that expanded ataxin-3 interferes with Hsp27 synthesis, which may contribute to the impairment of the cells' ability to respond to stresses and trigger the progression of this late-onset disease.
Department of Life Science, Tunghai University, Taichung, Taiwan, ROC.
Wei-Hsiu
WH
Chang
Chih-Liang
CL
Tien
Tzu-Jung
TJ
Chen
Nobuyuki
N
Nukina
Mingli
M
Hsieh
D000818:Animals; D000067699:Ataxin-3; D015153:Blotting, Western; D019556:COS Cells; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D015870:Gene Expression; D055551:HSP27 Heat-Shock Proteins / Q000096:biosynthesis*; D006360:Heat-Shock Proteins; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology; D017827:Machado-Joseph Disease / Q000378:metabolism*; D018832:Molecular Chaperones; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010455:Peptides; D012333:RNA, Messenger / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013312:Stress, Physiological; D014162:Transfection
D015853:Cysteine Proteinase Inhibitors; D055551:HSP27 Heat-Shock Proteins; C057725:HSPB1 protein, human; D006360:Heat-Shock Proteins; D007976:Leupeptins; D018832:Molecular Chaperones; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D010455:Peptides; D012333:RNA, Messenger; D012097:Repressor Proteins; C063261:acetylleucyl-leucyl-norleucinal; C097188:polyglutamine; C092341:ATXN3 protein, human; D000067699:Ataxin-3; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde