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University of California, Davis
Publishes on Genetic Neurodegenerative Diseases, Mitochondrial Function and Pathology, Hereditary Neurological Disorders. 22 papers and 3.4k citations.
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Huntington9s disease (HD) results from polyglutamine expansion in huntingtin (htt), a protein with several consensus caspase cleavage sites. Despite the identification of htt fragments in the brain, it has not been shown conclusively that htt is cleaved by caspases <i>in vivo</i>. Furthermore, no study has addressed when htt cleavage occurs with respect to the onset of neurodegeneration. Using antibodies that detect only caspase-cleaved htt, we demonstrate that htt is cleaved <i>in vivo</i> specifically at the caspase consensus site at amino acid 552. We detect caspase-cleaved htt in control human brain as well as in HD brains with early grade neuropathology, including one homozygote. Cleaved htt is also seen in wild-type and HD transgenic mouse brains before the onset of neurodegeneration. These results suggest that caspase cleavage of htt may be a normal physiological event. However, in HD, cleavage of mutant htt would release N-terminal fragments with the potential for increased toxicity and accumulation caused by the presence of the expanded polyglutamine tract. Furthermore, htt fragments were detected most abundantly in cortical projection neurons, suggesting that accumulation of expanded htt fragments in these neurons may lead to corticostriatal dysfunction as an early event in the pathogenesis of HD.
Huntingtin proteolysis has been implicated in the molecular pathogenesis of Huntington disease (HD). Despite an intense effort, the identity of the pathogenic smallest N-terminal fragment has not been determined. Using a panel of anti-huntingtin antibodies, we employed an unbiased approach to generate proteolytic cleavage maps of mutant and wild-type huntingtin in the HdhQ150 knock-in mouse model of HD. We identified 14 prominent N-terminal fragments, which, in addition to the full-length protein, can be readily detected in cytoplasmic but not nuclear fractions. These fragments were detected at all ages and are not a consequence of the pathogenic process. We demonstrated that the smallest fragment is an exon 1 huntingtin protein, known to contain a potent nuclear export signal. Prior to the onset of behavioral phenotypes, the exon 1 protein, and possibly other small fragments, accumulate in neuronal nuclei in the form of a detergent insoluble complex, visualized as diffuse granular nuclear staining in tissue sections. This methodology can be used to validate the inhibition of specific proteases as therapeutic targets for HD by pharmacological or genetic approaches.
Huntington's disease (HD) is a neurodegenerative disorder caused by a CAG expansion that results in elongation of the polyglutamine tract at the N terminus of huntingtin (Htt). Abnormal proteolytic processing of mutant Htt has been implicated as a critical step in the initiation of HD. The protease(s) involved in this process has not been fully characterized. Here we report that activated calpain was detected in the caudate of human HD tissue but not in age-matched controls. In addition, one of the major N-terminal Htt proteolytic fragments found in human HD tissue appears to be derived from calpain cleavage. Htt fragments in HD lysates were similar in size to those produced by exposure of in vitro-translated Htt to exogenous calpain. Incubation of in vitro-translated Htt with calpain generated a cascade of cleavage events with an initial intermediate cleavage product at 72 kDa and a final cleavage product at 47 kDa. The rate of cleavage of Htt by calpain was polyglutamine-length-dependent. These results suggest that cleavage of Htt in human HD tissue is mediated in part by the Ca2+-activated neutral protease, calpain.
Huntington's disease (HD) is a neurodegenerative disorder caused by a polyglutamine (polyQ) tract expansion near the N terminus of huntingtin (Htt). Proteolytic processing of mutant Htt and abnormal calcium signaling may play a critical role in disease progression and pathogenesis. Recent work indicates that calpains may participate in the increased and/or altered patterns of Htt proteolysis leading to the selective toxicity observed in HD striatum. Here, we identify two calpain cleavage sites in Htt and show that mutation of these sites renders the polyQ expanded Htt less susceptible to proteolysis and aggregation, resulting in decreased toxicity in an in vitro cell culture model. In addition, we found that calpain- and caspase-derived Htt fragments preferentially accumulate in the nucleus without the requirement of further cleavage into smaller fragments. Calpain family members, calpain-1, -5, -7, and -10, have increased levels or are activated in HD tissue culture and transgenic mouse models, suggesting they may play a key role in Htt proteolysis and disease pathology. Interestingly, calpain-1, -5, -7, and -10 localize to the cytoplasm and the nucleus, whereas the activated forms of calpain-7 and -10 are found only in the nucleus. These results support the role of calpain-derived Htt fragmentation in HD and suggest that aberrant activation of calpains may play a role in HD pathogenesis. Huntington's disease (HD) is a neurodegenerative disorder caused by a polyglutamine (polyQ) tract expansion near the N terminus of huntingtin (Htt). Proteolytic processing of mutant Htt and abnormal calcium signaling may play a critical role in disease progression and pathogenesis. Recent work indicates that calpains may participate in the increased and/or altered patterns of Htt proteolysis leading to the selective toxicity observed in HD striatum. Here, we identify two calpain cleavage sites in Htt and show that mutation of these sites renders the polyQ expanded Htt less susceptible to proteolysis and aggregation, resulting in decreased toxicity in an in vitro cell culture model. In addition, we found that calpain- and caspase-derived Htt fragments preferentially accumulate in the nucleus without the requirement of further cleavage into smaller fragments. Calpain family members, calpain-1, -5, -7, and -10, have increased levels or are activated in HD tissue culture and transgenic mouse models, suggesting they may play a key role in Htt proteolysis and disease pathology. Interestingly, calpain-1, -5, -7, and -10 localize to the cytoplasm and the nucleus, whereas the activated forms of calpain-7 and -10 are found only in the nucleus. These results support the role of calpain-derived Htt fragmentation in HD and suggest that aberrant activation of calpains may play a role in HD pathogenesis. Huntington's disease (HD) 1The abbreviations used are: HD, Huntington's disease; polyQ, polyglutamine; PARP, poly(ADP-ribose) polymerase; Pipes, 1,4-piperazinediethanesulfonic acid; Chaps, 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid; Bis-Tris, 2-[bis(2-hydroxyethyl)amino]-2-(hydroxymethyl)propane-1,3-diol; NES, nuclear export signal; DEVD, Asp-Glu-Val-Asp. is an autosomal-dominant neurodegenerative disease caused by a CAG expansion in the huntingtin gene (htt) (1Huntington's Disease Collaborative Research GroupCell. 1993; 72: 971-983Abstract Full Text PDF PubMed Scopus (7080) Google Scholar), and is characterized by involuntary movements, personality changes, dementia, and early death (2Huntington G. J. Neuropsychiatry Clin. Neurosci. 2003; 15: 109-112Crossref PubMed Scopus (54) Google Scholar). Huntingtin protein (Htt) is expressed throughout the central nervous system as well as non-neuronal cells, yet causes selective neuronal death in the striatum and cortex (3DiFiglia M. Sapp E. Chase K. Schwarz C. Meloni A. Young C. Martin E. Vonsattel J.P. Carraway R. Reeves S.A. Boyce F.M. Aronin N. Neuron. 1995; 14: 1075-1081Abstract Full Text PDF PubMed Scopus (620) Google Scholar, 4Graveland G.A. Williams R.S. DiFiglia M. Science. 1985; 227: 770-773Crossref PubMed Scopus (497) Google Scholar, 5Sapp E. Ge P. Aizawa H. Bird E. Penney J. Young A.B. Vonsattel J.P. DiFiglia M. Neuroscience. 1995; 64: 397-404Crossref PubMed Scopus (141) Google Scholar, 6Hedreen J.C. Peyser C.E. Folstein S.E. Ross C.A. Neurosci. Lett. 1991; 133: 257-261Crossref PubMed Scopus (257) Google Scholar). The selective neurodegeneration found in HD may be linked to the expression of particular receptors and proteases in the affected striatal and cortical cells, but the molecular details of these events are not well characterized. One hypothesis that has received a great deal of attention is that production of N-terminal Htt fragments plays a key role in disease pathogenesis (7Mangiarini L. Sathasivam K. Seller M. Cozens B. Harper A. Hetherington C. Lawton M. Trottier Y. Lehrach H. Davies S.W. Bates G.P. Cell. 1996; 87: 493-506Abstract Full Text Full Text PDF PubMed Scopus (2593) Google Scholar, 8DiFiglia M. Sapp E. Chase K.O. Davies S.W. Bates G.P. Vonsattel J.P. Aronin N. Science. 1997; 277: 1990-1993Crossref PubMed Scopus (2322) Google Scholar, 9Goldberg Y.P. Nicholson D.W. Rasper D.M. Kalchman M.A. Koide H.B. Graham R.K. Bromm M. Kazemi-Esfarjani P. Thornberry N.A. Vaillancourt J.P. Hayden M.R. Nat. Genet. 1996; 13: 442-449Crossref PubMed Scopus (502) Google Scholar, 10Martindale D. Hackam A. Wieczorek A. Ellerby L. Wellington C. McCutcheon K. Singaraja R. Kazemi-Esfarjani P. Devon R. Kim S.U. Bredesen D.E. Tufaro F. Hayden M.R. Nat. Genet. 1998; 18: 150-154Crossref PubMed Scopus (422) Google Scholar). Our recent studies have shown that calpain cleaves Htt sites to N-terminal fragments J. Ellerby J. Neurosci. PubMed Google Scholar). In addition, we have that the of calpain is increased in the of HD suggesting that calpain-derived Htt fragments may to the of HD J. Ellerby J. Neurosci. PubMed Google Scholar). have as to Htt may early of the and these may be linked to and the activation of the the calpains N. A. Wellington Hayden M.R. Cell. Neurosci. PubMed Scopus Google Scholar, N. Wellington P. Hayden M.R. Neuron. Full Text Full Text PDF Scopus Google Scholar, H. A. Wellington Hayden M.R. Neuron. 2003; Full Text Full Text PDF PubMed Scopus Google Scholar). and receptors are in the striatum and play a role in the of in The of Htt receptors in the leading to N. A. Wellington Hayden M.R. Cell. Neurosci. PubMed Scopus Google Scholar, N. Wellington C. M. McCutcheon K. Hayden M.R. J. 72: PubMed Scopus Google Scholar, Y. A. J. Full Text Full Text PDF PubMed Scopus Google Scholar). The of Htt leading to receptors activation H. A. Wellington Hayden M.R. Neuron. 2003; Full Text Full Text PDF PubMed Scopus Google Scholar). the disease of Htt has in C.A. Hayden M.R. Nat. Neurosci. PubMed Scopus Google Scholar, 2003; PubMed Scopus Google Scholar). have shown that calpains and Htt Y.P. Nicholson D.W. Rasper D.M. Kalchman M.A. Koide H.B. Graham R.K. Bromm M. Kazemi-Esfarjani P. Thornberry N.A. Vaillancourt J.P. Hayden M.R. Nat. Genet. 1996; 13: 442-449Crossref PubMed Scopus (502) Google Scholar, 10Martindale D. Hackam A. Wieczorek A. Ellerby L. Wellington C. McCutcheon K. Singaraja R. Kazemi-Esfarjani P. Devon R. Kim S.U. Bredesen D.E. Tufaro F. Hayden M.R. Nat. Genet. 1998; 18: 150-154Crossref PubMed Scopus (422) Google Scholar, J. Ellerby J. Neurosci. PubMed Google Scholar, Ellerby Hackam M.A. Singaraja R. McCutcheon K. Bromm M. Rasper D. Thornberry N. L. A. Ross C.A. Nicholson D.W. Bredesen D.E. Hayden M.R. J. 1998; Full Text Full Text PDF PubMed Scopus (497) Google Scholar, Singaraja R. Wellington M. McCutcheon K. Kalchman M. Hayden M.R. J. 1998; PubMed Scopus Google Scholar, Singaraja R. Ellerby L. J. B. E. Hackam A. A. Thornberry N. Nicholson D.W. Bredesen D.E. Hayden M.R. J. Full Text Full Text PDF PubMed Scopus Google Scholar, Ellerby C.A. D. Graham R.K. J. Singaraja R. J. Bredesen D. Nicholson D.W. Hayden M.R. J. Neurosci. PubMed Google Scholar). is the processing of Htt in vitro and in Y.P. Nicholson D.W. Rasper D.M. Kalchman M.A. Koide H.B. Graham R.K. Bromm M. Kazemi-Esfarjani P. Thornberry N.A. Vaillancourt J.P. Hayden M.R. Nat. Genet. 1996; 13: 442-449Crossref PubMed Scopus (502) Google Scholar, 10Martindale D. Hackam A. Wieczorek A. Ellerby L. Wellington C. McCutcheon K. Singaraja R. Kazemi-Esfarjani P. Devon R. Kim S.U. Bredesen D.E. Tufaro F. Hayden M.R. Nat. Genet. 1998; 18: 150-154Crossref PubMed Scopus (422) Google Scholar, Ellerby Hackam M.A. Singaraja R. McCutcheon K. Bromm M. Rasper D. Thornberry N. L. A. Ross C.A. Nicholson D.W. Bredesen D.E. Hayden M.R. J. 1998; Full Text Full Text PDF PubMed Scopus (497) Google Scholar, Singaraja R. Wellington M. McCutcheon K. Kalchman M. Hayden M.R. J. 1998; PubMed Scopus Google Scholar, Singaraja R. Ellerby L. J. B. E. Hackam A. A. Thornberry N. Nicholson D.W. Bredesen D.E. Hayden M.R. J. Full Text Full Text PDF PubMed Scopus Google Scholar, Ellerby C.A. D. Graham R.K. J. Singaraja R. J. Bredesen D. Nicholson D.W. Hayden M.R. J. Neurosci. PubMed Google Scholar). is not Htt the in a neurodegenerative and the of of the family has in the cell death Y.P. Nicholson D.W. Rasper D.M. Kalchman M.A. Koide H.B. Graham R.K. Bromm M. Kazemi-Esfarjani P. Thornberry N.A. Vaillancourt J.P. Hayden M.R. Nat. 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PubMed Scopus Google Scholar, 1998; PubMed Scopus Google Scholar, H. R. J. 2003; Full Text Full Text PDF PubMed Scopus Google Scholar, C. N. M. J. Full Text Full Text PDF PubMed Scopus Google Scholar, Y. J. PubMed Scopus Google Scholar, M. H. J.C. J. Full Text Full Text PDF PubMed Scopus Google Scholar, K. P. J. Full Text Full Text PDF PubMed Scopus Google Scholar). -7, -10, and are expressed in the but or have not is expressed and may have a role in Y. Full Text Full Text PDF PubMed Scopus Google Scholar). has as a gene Y. N. M. M. Y. H. Schwarz L. Y. P. N. J. C. L. E. Nat. Genet. PubMed Scopus Google and is a of a gene M. Young 1998; PubMed Scopus Google Scholar). found to be to the nucleus, and nuclear H. C. Kim N.A. M. M. J. Full Text Full Text PDF PubMed Scopus Google Scholar). of to the cleavage events in HD, we the role calpain cleavage plays in Htt toxicity and of the calpain family are expressed or activated altered in HD cell culture and transgenic mouse found that calpains Htt and The sites of cleavage are an that cleavage sites in Htt toxicity and Htt observed the of Htt expressed in a cell culture altered The Htt fragments found to preferentially accumulate in the nuclear without the requirement of further we found calpain family calpain-1, -5, -7, and -10 levels are increased and/or activated in HD tissue culture and transgenic mouse and expression used in these studies the and and forms of the and N-terminal Htt and have Y.P. Nicholson D.W. Rasper D.M. Kalchman M.A. Koide H.B. Graham R.K. Bromm M. Kazemi-Esfarjani P. Thornberry N.A. Vaillancourt J.P. Hayden M.R. Nat. Genet. 1996; 13: 442-449Crossref PubMed Scopus (502) Google Scholar, 10Martindale D. Hackam A. Wieczorek A. Ellerby L. Wellington C. McCutcheon K. Singaraja R. Kazemi-Esfarjani P. Devon R. Kim S.U. Bredesen D.E. Tufaro F. Hayden M.R. Nat. Genet. 1998; 18: 150-154Crossref PubMed Scopus (422) Google Scholar, Singaraja R. Ellerby L. J. B. E. Hackam A. A. Thornberry N. Nicholson D.W. Bredesen D.E. Hayden M.R. J. Full Text Full Text PDF PubMed Scopus Google Scholar). used to identify and calpain cleavage of and as well as in the and and forms of the and N-terminal Htt fragments and to and In addition, or in the as calpain cleavage sites by the of of of and and of and and into and the by of calpain cleavage sites calpain cleavage of in vitro as as well as of Htt cleavage in J. Ellerby J. Neurosci. PubMed Google Scholar). of a to the and The a of of and of and The a and into a a used of Htt or or and or cell or mouse tissue in Wellington Hackam Ross C.A. Hayden M.R. Bredesen D.E. J. Full Text Full Text PDF PubMed Scopus Google Scholar, Hackam Ellerby M.A. L. Wellington Hayden M.R. Bredesen D.E. J. 72: PubMed Scopus Google Scholar), or the nuclear and in the of of of mouse to and Htt Htt Htt N-terminal Htt Ellerby C.A. D. Graham R.K. J. Singaraja R. J. Bredesen D. Nicholson D.W. Hayden M.R. J. Neurosci. PubMed Google Scholar), Htt Htt Research Research calpain calpain calpain-7 R. J. Neurosci. 14: PubMed Google or and and used to of a and the in cell to cell to Pipes, Chaps, and and an of and an of a The of in the to protein levels to levels the in Htt or Research by or used as a nuclear Calpain a to the The in to a of in a J. 1993; PubMed Scopus Google the or or and or of of and of in a of of and tissue HD in a and by the into of Htt and the and and to of of Calpain in have shown that calpains Htt to N-terminal cleavage J. Ellerby J. Neurosci. PubMed Google Scholar). In we found that of in vitro or and N-terminal two of and are in to the of Htt in cell culture and in vitro the Htt calpain cleavage and the sites and and The of cleavage in Htt and calpain cleavage toxicity of the of Htt not in work J. Ellerby J. Neurosci. PubMed Google Scholar). we the of calpain cleavage in Htt and the of these in a cell culture model. of calpain used to identify calpain cleavage sites in the of calpain cleavage sites have in calpains the of protein D.E. 1991; PubMed Scopus Google Scholar). the only we a of an calpain cleavage in protein D.E. 1991; PubMed Scopus Google Scholar), cleavage of Htt by of expressed in Htt cleavage and found that expressed in cells, to calpain cleavage and production of the calpain-derived Htt and in vitro of calpain the production of the we the calpain cleavage in Htt that the a of is an calpain cleavage in J. J. PubMed Scopus Google Scholar). found that expressed in cells, to calpain cleavage and production of the calpain-derived Htt and we the Htt calpain sites of or in the and calpain fragments and The Htt cleavage and and are caspase-derived and of the of we in Htt calpain cleavage only the calpain cleavage sites and found these calpain proteolysis of of a calpain cleavage not production of the calpain-derived Htt in expressed in of a calpain in not the production of the calpain-derived Htt of calpain cleavage sites to the or not calpain cleavage of Htt and further the of these and the to in calpain proteolysis and toxicity of we of these calpain cleavage sites cleavage of Htt these sites are in to of these and not and production of caspase-derived Htt fragments these are expressed in culture they susceptible to The calpain cleavage of Htt by a to Htt calpain cleavage is levels of the of the N-terminal Htt Htt Htt protein to used as a and the molecular as the cleavage not to identify the calpain cleavage the N-terminal Htt to and a to two of the calpain cleavage sites and of these production of the calpain-derived Htt not the N-terminal cleavage a calpain cleavage of Htt in cell culture not of not Htt in an in work we the proteolysis and toxicity of Htt in tissue culture that activated cell death Singaraja R. Ellerby L. J. B. E. Hackam A. A. Thornberry N. Nicholson D.W. Bredesen D.E. Hayden M.R. J. Full Text Full Text PDF PubMed Scopus Google Scholar). is not of cell death activation is in recent that altered plays an role in HD pathogenesis and progression N. C.A. F. Singaraja R. N. McCutcheon K. J. L. E. J.C. Hayden M.R. Neuron. Full Text Full Text PDF PubMed Scopus Google Scholar). we a cell culture to the cleavage of Htt by and calpains that levels J. Ellerby J. Neurosci. PubMed Google Scholar). or Htt a that levels of the and and of the of in or Htt or and N-terminal Htt of Htt in and Htt the in of calpain family in a cell culture model. levels of calpain family in calpain protein levels and activation in The forms are by and forms by and of by and or increased levels of the and of calpain by and in increased levels of Htt cleavage to are increased cleavage of Htt but less of the cleavage Htt and that the of the Htt cleavage to be The of cleavage to is to in the the of Htt we cell culture that and the calpain cleavage sites in we to calpain cleavage of Htt and we expressed the in and of the of in the tissue culture as by to a in to The of protein the The protein suggesting to The in not to altered levels of Htt expression as by not Htt Htt and in an in cleavage have Htt in that may toxicity and These cleavage of Htt by Y.P. Nicholson D.W. Rasper D.M. Kalchman M.A. Koide H.B. Graham R.K. Bromm M. Kazemi-Esfarjani P. Thornberry N.A. Vaillancourt J.P. Hayden M.R. Nat. Genet. 1996; 13: 442-449Crossref PubMed Scopus (502) Google Scholar, Singaraja R. Ellerby L. J. B. E. Hackam A. A. Thornberry N. Nicholson D.W. Bredesen D.E. Hayden M.R. J. Full Text Full Text PDF PubMed Scopus Google Scholar), calpains J. Ellerby J. Neurosci. PubMed Google Scholar, Y. Sapp E. Y. B. Aronin N. DiFiglia M. A. PubMed Scopus Google Scholar), and an A. L. C. D. Trottier Y. Cell. Full Text Full Text PDF PubMed Scopus Google Scholar). these or is not we Htt we cleavage these Htt calpain sites and the production of smaller N-terminal fragments. a in proteolysis to of not only production of the calpain-derived cleavage but to a in further proteolysis of Htt by a in the of molecular N-terminal Htt cleavage observed the of may the N-terminal Htt A. L. C. D. Trottier Y. Cell. Full Text Full Text PDF PubMed Scopus Google Scholar). The protein a in Htt to and a in the of Htt in the by as well as a in the and of observed in to In whereas these the these have and HD the that the Htt is less be that in cleavage and observed Htt a N-terminal Htt and Htt Calpain and of Htt to the of fragments in the nucleus has in HD, as well as polyQ D. Hackam A. Wieczorek A. Ellerby L. Wellington C. McCutcheon K. Singaraja R. Kazemi-Esfarjani P. Devon R. Kim S.U. Bredesen D.E. Tufaro F. Hayden M.R. Nat. Genet. 1998; 18: 150-154Crossref PubMed Scopus (422) Google Scholar, Singaraja R. Wellington M. McCutcheon K. Kalchman M. Hayden M.R. J. 1998; PubMed Scopus Google Scholar, Genet. PubMed Scopus Google Scholar, H. H.B. Cell. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar, Singaraja R. L. Hayden M.R. Genet. PubMed Scopus Google Scholar, J. Ross C.A. Cell. Neurosci. 14: PubMed Scopus Google Scholar, G. K. M. N.A. H. Ross C.A. Neuron. Full Text Full Text PDF PubMed Scopus Google Scholar, Ellerby Wellington A. Hayden M.R. Ross C.A. J. 2003; Full Text Full Text PDF PubMed Scopus Google Scholar). toxicity of N-terminal Htt fragments be by of a nuclear and decreased by of a nuclear export J. Ross C.A. Cell. Neurosci. 14: PubMed Scopus Google Scholar). Htt a NES, suggesting Htt may and the and nucleus J. J. M. R. Genet. 2003; PubMed Google Scholar). The of Htt is suggesting the of the in the of Htt Meloni Y. Kim E. Sapp E. Y. Aronin N. DiFiglia M. J. 277: Full Text Full Text PDF PubMed Scopus Google Scholar, C.A. M. H. Vonsattel J.P. Genet. PubMed Scopus Google Scholar). studies have Htt be to or less N-terminal fragments to preferentially accumulate in the nucleus, fragments may not to the nucleus further D. Hackam A. Wieczorek A. Ellerby L. Wellington C. McCutcheon K. Singaraja R. Kazemi-Esfarjani P. Devon R. Kim S.U. Bredesen D.E. Tufaro F. Hayden M.R. Nat. Genet. 1998; 18: 150-154Crossref PubMed Scopus (422) Google Scholar, Singaraja R. Wellington M. McCutcheon K. Kalchman M. Hayden M.R. J. 1998; PubMed Scopus Google Scholar, Singaraja R. L. Hayden M.R. Genet. PubMed Scopus Google Scholar). These studies Htt and not is of to fragments the cytoplasm to the nucleus. In addition, a of Htt in the nucleus, and is to cleavage in Htt cleavage the nucleus, of and in to production of calpain-derived Htt fragments. Htt the nucleus only in the nuclear Interestingly, of the observed in the nucleus as well as the is the of the Htt in these In addition, we found calpain and Htt cleavage accumulate in the nucleus and the calpain-derived Htt cleavage in the and nuclear the calpain-derived Htt cleavage to the nuclear have and characterized Htt that the cleavage of Htt and Ellerby C.A. D. Graham R.K. J. Singaraja R. J. Bredesen D. Nicholson D.W. Hayden M.R. J. Neurosci. PubMed Google Scholar). the the Htt cleavage in the nuclear and not the results observed the Htt cleavage by to the and the nuclear studies the the nuclear of the Htt cleavage of into Our studies not cleavage of Htt in the nucleus or Calpain to and in the proteolysis of and nuclear by family has of calpain cleavage events is of the calpain family calpain-1, and have well characterized. calpain family members, and are expressed in the tissue H. C. Kim N.A. M. M. J. Full Text Full Text PDF PubMed Scopus Google E. J. E. C. L. M. R. and L. M. and may play a role in HD pathogenesis. In addition, levels of -7, and -10 are altered in the HD mouse E. J. E. C. L. M. R. and L. M. further further calpain and Htt and in cleavage of calpain and to of the and forms of these proteases that and forms of as well as the calpain to the and -10 the in nuclear and and the in the nuclear and forms of found in the and nucleus in these studies as as well as is activated of J. J. PubMed Scopus Google Scholar). The of to the nucleus and whereas the to the The of forms of and to the found less activation of in the in these studies to the used to in studies Singaraja R. Ellerby L. J. B. E. Hackam A. A. Thornberry N. Nicholson D.W. Bredesen D.E. Hayden M.R. J. Full Text Full Text PDF PubMed Scopus Google Scholar). we and/or of calpains by in cell culture studies that -7, and -10 are increased to increased an in -7, and -10 protein levels activation of calpain family These results are increased calpain protein and activation of calpains altered we the and activation of calpain family in cell culture in by these proteases in an HD mouse model. in an HD Calpain the of calpain activation and proteolysis in HD in we an HD mouse mouse Htt polyQ A.B. Genet. PubMed Scopus Google Scholar). In studies we and to gene proteolysis and activation of The HD transgenic mouse has and HD A.B. Genet. PubMed Scopus Google Scholar). are found in and The are nuclear of Htt and protein in the striatum. found increased calpain and Htt fragmentation in the cortex and striatum of HD transgenic particular is the gene a to the calpain-derived cleavage of R. J. Neurosci. 14: PubMed Google and a in the the levels to or in the cleavage and a in found in the striatum of to as by calpain family altered in the cortex of the and of and -10 expression in the cortex a gene the the levels the or of these have A.B. Genet. PubMed Scopus Google Scholar). used to the role calpains play in the proteolysis of Htt in HD cell culture and transgenic mouse One HD is that production of fragments of the of Htt to HD and progression (7Mangiarini L. Sathasivam K. Seller M. Cozens B. Harper A. Hetherington C. Lawton M. Trottier Y. Lehrach H. Davies S.W. Bates G.P. Cell. 1996; 87: 493-506Abstract Full Text Full Text PDF PubMed Scopus (2593) Google Scholar, 8DiFiglia M. Sapp E. Chase K.O. Davies S.W. Bates G.P. 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In we found that the of Htt has calpain cleavage of is an early in HD pathogenesis and activation of calpains may be in Htt proteolysis and a in vitro model. cleavage have Htt in that may toxicity and These cleavage of Htt by Y.P. Nicholson D.W. Rasper D.M. Kalchman M.A. Koide H.B. Graham R.K. Bromm M. Kazemi-Esfarjani P. Thornberry N.A. Vaillancourt J.P. Hayden M.R. Nat. Genet. 1996; 13: 442-449Crossref PubMed Scopus (502) Google Scholar, Singaraja R. Ellerby L. J. B. E. Hackam A. A. Thornberry N. Nicholson D.W. Bredesen D.E. Hayden M.R. J. Full Text Full Text PDF PubMed Scopus Google Scholar), calpains J. Ellerby J. Neurosci. PubMed Google Scholar, Y. Sapp E. Y. B. Aronin N. DiFiglia M. A. PubMed Scopus Google Scholar), and an A. L. C. D. Trottier Y. Cell. Full Text Full Text PDF PubMed Scopus Google Scholar). these are of or in a is not of the Htt that cleavage the calpain sites is the production smaller N-terminal fragments a cleavage model. found that calpains and Htt of Htt by and Htt by the of Htt calpain cleavage of Htt In addition, Htt cleavage Our studies not the of activation of the family in is not yet the of or proteases to HD we that a of calpain family may be increased and activated in HD tissue culture and transgenic mouse found that an of the increased and of -7, and -10 in cell culture model. tissue culture studies we found that the of calpain-1, -5, -7, and -10 increased in striatal or cortical tissue in an HD mouse suggesting these calpain family may be in the of One particular studies is that the Htt cleavage accumulate in the nucleus without the requirement of further cleavage into smaller fragments. work that of the Htt fragments is and of Htt in the nucleus D. Hackam A. Wieczorek A. Ellerby L. Wellington C. McCutcheon K. Singaraja R. Kazemi-Esfarjani P. Devon R. Kim S.U. Bredesen D.E. Tufaro F. Hayden M.R. Nat. Genet. 1998; 18: 150-154Crossref PubMed Scopus (422) Google Scholar, Singaraja R. Wellington M. McCutcheon K. Kalchman M. Hayden M.R. J. 1998; PubMed Scopus Google Scholar). studies not the of Htt we the and activation of calpain and in the cytoplasm and nucleus. found a of calpain are to the nucleus suggesting that Htt be in Our work that calpains play a role in Htt proteolysis and HD pathology. work be of these calpain family play a critical role in HD and is the activation and of of these calpain family and particular to HD or calpains are in HD the studies are in and work calpains are HD and the and HD are to the Disease support to and and to the Huntington's Disease of support of and to A. Ross