Cleavage of huntingtin by apopain, a proapoptotic cysteine protease, is modulated by the polyglutamine tract.
Apoptosis has recently been recognized as a mode of cell death in Huntington disease (HD). Apopain, a human counterpart of the nematode cysteine protease death-gene product, CED-3, has a key role in proteolytic events leading to apoptosis. Here we show that apoptotic extracts and apopain itself specifically cleave the HD gene product, huntingtin. The rate of cleavage increases with the length of the huntingtin polyglutamine tract, providing an explanation for the gain-of-function associated with CAG expansion. Our results show that huntingtin is cleaved by cysteine proteases and suggest that HD might be a disorder of inappropriate apoptosis.
Goldberg
Y P
YP
Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada.
Nicholson
D W
DW
Rasper
D M
DM
Kalchman
M A
MA
Koide
H B
HB
Graham
R K
RK
Bromm
M
M
Kazemi-Esfarjani
P
P
Thornberry
N A
NA
Vaillancourt
J P
JP
Hayden
M R
MR
D000818:Animals; D017209:Apoptosis; D053148:Caspase 3; D020169:Caspases; D002460:Cell Line; D002522:Chlorocebus aethiops; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D006801:Humans; D000071058:Huntingtin Protein; D006816:Huntington Disease / Q000503:physiopathology; D007700:Kinetics; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry; D011994:Recombinant Proteins; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D014162:Transfection; D018911:Trinucleotide Repeats
C086055:HTT protein, human; D000071058:Huntingtin Protein; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D010455:Peptides; D011994:Recombinant Proteins; C097188:polyglutamine; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D003546:Cysteine Endopeptidases