TY - JOUR
T1 - N-terminal proteolysis of full-length mutant huntingtin in an inducible PC12 cell model of Huntington's disease
AU - Ratovitski, Tamara
AU - Nakamura, Masayuki
AU - D'Ambola, James
AU - Chighladze, Ekaterine
AU - Liang, Yideng
AU - Wang, Wenfei
AU - Graham, Rona
AU - Hayden, Michael R.
AU - Borchelt, David R.
AU - Hirschhorn, Ricky R.
AU - Ross, Christopher A.
N1 - Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.
PY - 2007/12/1
Y1 - 2007/12/1
N2 - Proteolytic cleavage of mutant huntingtin may play a key role in the pathogenesis of Huntington's disease; however the steps in huntingtin proteolysis are not fully understood. Huntingtin was shown to be cleaved by caspases and calpains within a region between 460-600 amino acids from the N-terminus. Two smaller N-terminal fragments produced by unknown protease have been previously described as cp-A and cp-B. To further investigate the huntingtin proteolytic pathway, we used an inducible PC12 cell model expressing full-length huntingtin with either normal or expanded polyglutamine. This cell model recapitulates several steps of huntingtin proteolysis: proteolysis mediated by caspases within the region previously mapped for caspase cleavage, and cleavage generating two novel N-terminal fragments (cp-1 approximately 90-105 residues long and cp-2 extending beyond 115-129 epitope of huntingtin). Interestingly, the deletion of amino acids 105-114 (mapped previously as a cleavage site for cp-A) failed to affect the production of cp-1 or cp-2. Therefore, we conclude that these new fragments are distinct from previously described cp-A and cp-B. We demonstrate that cp-1 and cp-2 fragments are produced and accumulate within nuclear and cytoplasmic inclusions prior to huntingtin-induced cell toxicity, and these fragments can be formed by caspase-independent proteolytic cleavage of huntingtin in PC12 cells. In addition, inhibition of calpains leads to decreased subsequent degradation of cp-1 and cp-2 fragments, and accelerated formation of inclusions. Further delineation of huntingtin cleavage events may lead to novel therapeutic targets for HD.
AB - Proteolytic cleavage of mutant huntingtin may play a key role in the pathogenesis of Huntington's disease; however the steps in huntingtin proteolysis are not fully understood. Huntingtin was shown to be cleaved by caspases and calpains within a region between 460-600 amino acids from the N-terminus. Two smaller N-terminal fragments produced by unknown protease have been previously described as cp-A and cp-B. To further investigate the huntingtin proteolytic pathway, we used an inducible PC12 cell model expressing full-length huntingtin with either normal or expanded polyglutamine. This cell model recapitulates several steps of huntingtin proteolysis: proteolysis mediated by caspases within the region previously mapped for caspase cleavage, and cleavage generating two novel N-terminal fragments (cp-1 approximately 90-105 residues long and cp-2 extending beyond 115-129 epitope of huntingtin). Interestingly, the deletion of amino acids 105-114 (mapped previously as a cleavage site for cp-A) failed to affect the production of cp-1 or cp-2. Therefore, we conclude that these new fragments are distinct from previously described cp-A and cp-B. We demonstrate that cp-1 and cp-2 fragments are produced and accumulate within nuclear and cytoplasmic inclusions prior to huntingtin-induced cell toxicity, and these fragments can be formed by caspase-independent proteolytic cleavage of huntingtin in PC12 cells. In addition, inhibition of calpains leads to decreased subsequent degradation of cp-1 and cp-2 fragments, and accelerated formation of inclusions. Further delineation of huntingtin cleavage events may lead to novel therapeutic targets for HD.
KW - Calpains
KW - Caspases
KW - Huntington's disease mechanism
KW - Protein degradation
KW - Proteolysis
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U2 - 10.4161/cc.6.23.4992
DO - 10.4161/cc.6.23.4992
M3 - Article
C2 - 18156806
AN - SCOPUS:37549065909
SN - 1538-4101
VL - 6
SP - 2970
EP - 2981
JO - Cell Cycle
JF - Cell Cycle
IS - 23
ER -