PolyQ-expanded ataxin-3 interacts with full-length ataxin-3 in a polyQ length-dependent manner.
OBJECTIVE
Machado-Joseph disease (MJD), also known as spinocerebellar ataxia type 3 (SCA3), is a dominant neurodegenerative disorder caused by an expansion of the polyglutamine (polyQ) tract in MJD-1 gene product, ataxin-3 (AT3). This disease is characterized by the formation of intraneuronal inclusions, but the mechanism underlying their formation is still poorly understood. The present study is to explore the relationship between wild type (WT) AT3 and polyQ expanded AT3.


METHODS
Mouse neuroblastoma (N2a) cells or HEK293 cells were co-transfected with WT AT3 and different truncated forms of expanded AT3. The expressions of WT AT3 and the truncated forms of expanded AT3 were detected by Western blotting, and observed by an inverted fluorescent microscope. The interactions between AT3 and different truncated forms of expanded AT3 were detected by immunoprecipitation and GST pull-down assays.


RESULTS
Using fluorescent microscope, we observed that the truncated forms of expanded AT3 aggregate in transfected cells, and the full-length WT AT3 is recruited onto the aggregates. However, no aggregates were observed in cells transfected with the truncated forms of WT AT3. Immunoprecipitation and GST pull-down analyses indicate that WT AT3 interacts with the truncated AT3 in a polyQ length-dependent manner.


CONCLUSIONS
WT AT3 deposits in the aggregation that was formed by polyQ expanded AT3, which suggests that the formation of AT3 aggregation may affect the normal function of WT AT3 and increase polyQ protein toxicity in MJD.
Jia
Na-Li
NL
Laboratory of Molecular Neuropathology, Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, China.
Fei
Er-Kang
EK
Ying
Zheng
Z
Wang
Hong-Feng
HF
Wang
Guang-Hui
GH
D000818:Animals; D000067699:Ataxin-3; D015153:Blotting, Western; D002460:Cell Line; D047468:Immunoprecipitation; D017827:Machado-Joseph Disease / Q000378:metabolism; D051379:Mice; D008856:Microscopy, Fluorescence; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
D009687:Nuclear Proteins; D010455:Peptides; D014157:Transcription Factors; C097188:polyglutamine; D000067699:Ataxin-3; C511594:Atxn3 protein, mouse