Cleavage at the caspase-6 site is required for neuronal dysfunction and degeneration due to mutant huntingtin |
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Authors: | Graham Rona K Deng Yu Slow Elizabeth J Haigh Brendan Bissada Nagat Lu Ge Pearson Jacqueline Shehadeh Jacqueline Bertram Lisa Murphy Zoe Warby Simon C Doty Crystal N Roy Sophie Wellington Cheryl L Leavitt Blair R Raymond Lynn A Nicholson Donald W Hayden Michael R |
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Institution: | Department of Medical Genetics, Centre for Molecular Medicine and Therapeutics, University of British Columbia, Vancouver, BC V5Z 4H4, Canada. |
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Abstract: | 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. |
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