E6-AP promotes misfolded polyglutamine proteins for proteasomal degradation and suppresses polyglutamine protein aggregation and toxicity.
The accumulation of intracellular protein deposits as inclusion bodies is the common pathological hallmark of most age-related neurodegenerative disorders including polyglutamine diseases. Appearance of aggregates of the misfolded mutant disease proteins suggest that cells are unable to efficiently degrade them, and failure of clearance leads to the severe disturbances of the cellular quality control system. Recently, the quality control ubiquitin ligase CHIP has been shown to suppress the polyglutamine protein aggregation and toxicity. Here we have identified another ubiquitin ligase, called E6-AP, which is able to promote the proteasomal degradation of misfolded polyglutamine proteins and suppress the polyglutamine protein aggregation and polyglutamine protein-induced cell death. E6-AP interacts with the soluble misfolded polyglutamine protein and associates with their aggregates in both cellular and transgenic mouse models. Partial knockdown of E6-AP enhances the rate of aggregate formation and cell death mediated by the polyglutamine protein. Finally, we have demonstrated the up-regulation of E6-AP in the expanded polyglutamine protein-expressing cells as well as cells exposed to proteasomal stress. These findings suggest that E6-AP is a critical mediator of the neuronal response to misfolded polyglutamine proteins and represents a potential therapeutic target in the polyglutamine diseases.
Mishra
Amit
A
Cellular and Molecular Neuroscience Laboratory, National Brain Research Centre, Manesar, Gurgaon-122 050.
Dikshit
Priyanka
P
Purkayastha
Sudarshana
S
Sharma
Jaiprakash
J
Nukina
Nobuyuki
N
Jana
Nihar Ranjan
NR
D000818:Animals; D019556:COS Cells; D016923:Cell Death / Q000235:genetics; D002522:Chlorocebus aethiops; D004195:Disease Models, Animal; D006801:Humans; D006816:Huntington Disease / Q000201:enzymology / Q000235:genetics; D051379:Mice; D008822:Mice, Transgenic; D020966:Muscular Disorders, Atrophic / Q000201:enzymology / Q000235:genetics; D010455:Peptides / Q000235:genetics / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism*; D017510:Protein Folding; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
D010455:Peptides; C097188:polyglutamine; C471639:UBE3A protein, human; C467728:STUB1 protein, human; C492951:Stub1 protein, mouse; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex