Cleavage at the caspase-6 site is required for neuronal dysfunction and degeneration due to mutant huntingtin.
Cleavage of huntingtin (htt) has been characterized in vitro, and accumulation of caspase cleavage fragments represents an early pathological change in brains of Huntington's disease (HD) patients. However, the relationship between htt proteolysis and the pathogenesis of HD is unknown. To determine whether caspase cleavage of htt is a key event in the neuronal dysfunction and selective neurodegeneration in HD, we generated YAC mice expressing caspase-3- and caspase-6-resistant mutant htt. Mice expressing mutant htt, resistant to cleavage by caspase-6 but not caspase-3, maintain normal neuronal function and do not develop striatal neurodegeneration. Furthermore, caspase-6-resistant mutant htt mice are protected against neurotoxicity induced by multiple stressors including NMDA, quinolinic acid (QA), and staurosporine. These results are consistent with proteolysis of htt at the caspase-6 cleavage site being an important event in mediating neuronal dysfunction and neurodegeneration and highlight the significant role of htt proteolysis and excitotoxicity in HD.
Graham
Rona K
RK
Department of Medical Genetics, Centre for Molecular Medicine and Therapeutics, University of British Columbia, Vancouver, BC V5Z 4H4, Canada.
Deng
Yu
Y
Slow
Elizabeth J
EJ
Haigh
Brendan
B
Bissada
Nagat
N
Lu
Ge
G
Pearson
Jacqueline
J
Shehadeh
Jacqueline
J
Bertram
Lisa
L
Murphy
Zoe
Z
Warby
Simon C
SC
Doty
Crystal N
CN
Roy
Sophie
S
Wellington
Cheryl L
CL
Leavitt
Blair R
BR
Raymond
Lynn A
LA
Nicholson
Donald W
DW
Hayden
Michael R
MR
D021581:Active Transport, Cell Nucleus; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D053178:Caspase 6; D020169:Caspases / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D006801:Humans; D000071058:Huntingtin Protein; D006816:Huntington Disease / Q000378:metabolism* / Q000473:pathology; D006868:Hydrolysis; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation; D016202:N-Methylaspartate / Q000633:toxicity; D009410:Nerve Degeneration / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism* / Q000473:pathology; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D017378:Quinolinic Acid / Q000633:toxicity; D019311:Staurosporine / Q000633:toxicity
C086055:HTT protein, human; D000071058:Huntingtin Protein; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D016202:N-Methylaspartate; C505514:CASP6 protein, human; C505516:Casp6 protein, mouse; D053178:Caspase 6; D020169:Caspases; D017378:Quinolinic Acid; D019311:Staurosporine