p45, an ATPase subunit of the 19S proteasome, targets the polyglutamine disease protein ataxin-3 to the proteasome.
Machado-Joseph disease (MJD) is an autosomal dominant neurodegenerative disorder caused by an expansion of the polyglutamine tract near the C-terminus of the MJD-1 gene product, ataxin-3. Ataxin-3 is degraded by the proteasome. However, the precise mechanism of ataxin-3 degradation remains to be elucidated. In this study, we show direct links between ataxin-3 and the proteasome. p45, an ATPase subunit of the 19S proteasome, interacts with ataxin-3 in vitro and stimulates the degradation of ataxin-3 in an in vitro reconstituted degradation assay system. The effect of p45 on ataxin-3 degradation is blocked by MG132, a proteasome inhibitor. In N2a or 293 cells, overexpression of p45 strikingly enhances the clearance of both normal and expanded ataxin-3, but not alpha synuclein or SOD1, implying a functional specificity of p45 in this proteolytic process. The N-terminus of ataxin-3, which serves as a recognition site by p45, is necessary for the proteolytic process of ataxin-3. We also show that other three ATPases of the 19S proteasome, MSS1, p48, and p56 have no effect on ataxin-3 degradation. These data provide evidence that p45 plays an important role in regulating ataxin-3 degradation by the proteasome.
Wang
Hongfeng
H
Hefei National Laboratory for Physical Sciences at Microscale and Department of Neurobiology, School of Life Sciences, University of Science & Technology of China, PR China.
Jia
Nali
N
Fei
Erkang
E
Wang
Zhiming
Z
Liu
Chao
C
Zhang
Tao
T
Fan
Jun
J
Wu
Mian
M
Chen
Lin
L
Nukina
Nobuyuki
N
Zhou
Jiangning
J
Wang
Guanghui
G
D000818:Animals; D000067699:Ataxin-3; D002460:Cell Line; D045744:Cell Line, Tumor; D006801:Humans; D047468:Immunoprecipitation; D007976:Leupeptins / Q000494:pharmacology; D017827:Machado-Joseph Disease / Q000378:metabolism; D051379:Mice; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D061988:Proteasome Inhibitors; D012097:Repressor Proteins / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism
D007976:Leupeptins; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D010455:Peptides; D061988:Proteasome Inhibitors; D012097:Repressor Proteins; D025801:Ubiquitin; C097188:polyglutamine; C092341:ATXN3 protein, human; D000067699:Ataxin-3; D046988:Proteasome Endopeptidase Complex; C119011:26S proteasome non-ATPase regulatory subunit 13; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde