Inhibiting caspase cleavage of huntingtin reduces toxicity and aggregate formation in neuronal and nonneuronal cells.
Huntington's disease is a neurodegenerative disorder caused by CAG expansion that results in expansion of a polyglutamine tract at the extreme N terminus of huntingtin (htt). htt with polyglutamine expansion is proapoptotic in different cell types. Here, we show that caspase inhibitors diminish the toxicity of htt. Additionally, we define htt itself as an important caspase substrate by generating a site-directed htt mutant that is resistant to caspase-3 cleavage at positions 513 and 530 and to caspase-6 cleavage at position 586. In contrast to cleavable htt, caspase-resistant htt with an expanded polyglutamine tract has reduced toxicity in apoptotically stressed neuronal and nonneuronal cells and forms aggregates at a much reduced frequency. These results suggest that inhibiting caspase cleavage of htt may therefore be of potential therapeutic benefit in Huntington's disease.
Wellington
C L
CL
Centre for Molecular Medicine and Therapeutics, University of British Columbia, Vancouver, British Columbia V5Z 4H4, Canada.
Singaraja
R
R
Ellerby
L
L
Savill
J
J
Roy
S
S
Leavitt
B
B
Cattaneo
E
E
Hackam
A
A
Sharp
A
A
Thornberry
N
N
Nicholson
D W
DW
Bredesen
D E
DE
Hayden
M R
MR
D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D001665:Binding Sites; D015153:Blotting, Western; D002273:Carcinogens / Q000494:pharmacology; D053148:Caspase 3; D053178:Caspase 6; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D002460:Cell Line; D004789:Enzyme Activation / Q000235:genetics; D005455:Fluorescent Antibody Technique; D006801:Humans; D000071058:Huntingtin Protein; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism* / Q000633:toxicity; D009474:Neurons / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism* / Q000633:toxicity; D010455:Peptides / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D051381:Rats; D013629:Tamoxifen / Q000494:pharmacology; D013997:Time Factors; D014162:Transfection
D002273:Carcinogens; D061945:Caspase Inhibitors; C086055:HTT protein, human; C499524:Htt protein, rat; D000071058:Huntingtin Protein; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D010455:Peptides; D013629:Tamoxifen; C097188:polyglutamine; C505407:CASP3 protein, human; C505514:CASP6 protein, human; C505410:Casp3 protein, rat; C505518:Casp6 protein, rat; D053148:Caspase 3; D053178:Caspase 6; D020169:Caspases