CHIP Protects from the Neurotoxicity of Expanded and Wild-type Ataxin-1 and Promotes Their Ubiquitination and Degradation

Abstract

CHIP (C terminus of Hsc-70 interacting protein) is an E3 ligase that links the protein folding machinery with the ubiquitin-proteasome system and has been implicated in disorders characterized by protein misfolding and aggregation. Here we investigate the role of CHIP in protecting from ataxin-1-induced neurodegeneration. Ataxin-1 is a polyglutamine protein whose expansion causes spinocerebellar ataxia type-1 (SCA1) and triggers the formation of nuclear inclusions (NIs). We find that CHIP and ataxin-1 proteins directly interact and co-localize in NIs both in cell culture and SCA1 postmortem neurons. CHIP promotes ubiquitination of expanded ataxin-1 both in vitro and in cell culture. The Hsp70 chaperone increases CHIP-mediated ubiquitination of ataxin-1 in vitro, and the tetratricopeptide repeat domain, which mediates CHIP interactions with chaperones, is required for ataxin-1 ubitiquination in cell culture. Interestingly, CHIP also interacts with and ubiquitinates unexpanded ataxin-1. Overexpression of CHIP in a Drosophila model of SCA1 decreases the protein steady-state levels of both expanded and unexpanded ataxin-1 and suppresses their toxicity. Finally we investigate the ability of CHIP to protect against toxicity caused by expanded polyglutamine tracts in different protein contexts. We find that CHIP is not effective in suppressing the toxicity caused by a bare 127Q tract with only a short hemaglutinin tag, but it is very efficient in suppressing toxicity caused by a 128Q tract in the context of an N-terminal huntingtin backbone. These data underscore the importance of the protein framework for modulating the effects of polyglutamine-induced neurodegeneration. CHIP (C terminus of Hsc-70 interacting protein) is an E3 ligase that links the protein folding machinery with the ubiquitin-proteasome system and has been implicated in disorders characterized by protein misfolding and aggregation. Here we investigate the role of CHIP in protecting from ataxin-1-induced neurodegeneration. Ataxin-1 is a polyglutamine protein whose expansion causes spinocerebellar ataxia type-1 (SCA1) and triggers the formation of nuclear inclusions (NIs). We find that CHIP and ataxin-1 proteins directly interact and co-localize in NIs both in cell culture and SCA1 postmortem neurons. CHIP promotes ubiquitination of expanded ataxin-1 both in vitro and in cell culture. The Hsp70 chaperone increases CHIP-mediated ubiquitination of ataxin-1 in vitro, and the tetratricopeptide repeat domain, which mediates CHIP interactions with chaperones, is required for ataxin-1 ubitiquination in cell culture. Interestingly, CHIP also interacts with and ubiquitinates unexpanded ataxin-1. Overexpression of CHIP in a Drosophila model of SCA1 decreases the protein steady-state levels of both expanded and unexpanded ataxin-1 and suppresses their toxicity. Finally we investigate the ability of CHIP to protect against toxicity caused by expanded polyglutamine tracts in different protein contexts. We find that CHIP is not effective in suppressing the toxicity caused by a bare 127Q tract with only a short hemaglutinin tag, but it is very efficient in suppressing toxicity caused by a 128Q tract in the context of an N-terminal huntingtin backbone. These data underscore the importance of the protein framework for modulating the effects of polyglutamine-induced neurodegeneration. Polyglutamine (poly-Q) 4The abbreviations used are: poly-Q, poly-glutamine; E1, ubiquitin-activating enzyme; E2, ubiquitin carrier protein; E3, ubiquitin protein ligase; Ub, ubiquitin; HA, hemaglutinin; SCA1, spinocerebellar ataxia type 1; SCA1nQ, gene coding for ataxin-1 [nQ] protein; NI, nuclear inclusion; CHIP, C-terminus of Hsc-70 interacting protein; TPR, tetratricopeptide repeat; GFP, green fluorescent protein; RT, reverse transcriptase; F-ataxin-1, FLAG-tagged ataxin-1; SEM, scanning electron microscopy; EID, eye imaginal disc; 127Q-HA, hemaglutinin-tagged glutamine 127; NT-Htt[128Q], glutamine 128-expanded N-terminal huntingtin; co-IP, co-immunoprecipitation; MOPS, 4-morpholinepropanesulfonic acid; PBS, phosphate-buffered saline. diseases are a group of neurodegenerative disorders caused by expansion of glutamine-encoding (CAG)n repeats in genes whose sequence is otherwise unrelated (1Zoghbi H.Y. Orr H.T. Annu. Rev. Neurosci. 2000; 23: 217-247Crossref PubMed Scopus (1103) Google Scholar, 2Gatchel J.R. Zoghbi H.Y. Nat. Rev. Genet. 2005; 6: 743-755Crossref PubMed Scopus (633) Google Scholar). One such protein is ataxin-1, where expansion of its N terminus glutamine repeat triggers spinocerebellar ataxia type 1. SCA1 is an adult-onset disorder characterized by loss of motor coordination and balance, which progresses to affect vital brain functions such as breathing and swallowing. Brain dysfunction is in part due to degeneration of cerebellar Purkinje cells, brainstem neurons, and the spinocerebellar tracts. Strong evidence supports the idea of a gain of function mechanism triggered by the poly-Q expansion in ataxin-1 (1Zoghbi H.Y. Orr H.T. Annu. Rev. Neurosci. 2000; 23: 217-247Crossref PubMed Scopus (1103) Google Scholar, 3Tsuda H. Jafar-Nejad H. Patel A.J. Sun Y. Chen H.K. Rose M.F. Venken K.J. Botas J. Orr H.T. Bellen H.J. Zoghbi H.Y. Cell. 2005; 122: 633-644Abstract Full Text Full Text PDF PubMed Scopus (160) Google Scholar, 4Klement I.A. Skinner P.J. Kaytor M.D. Yi H. Hersch S.M. Clark H.B. Zoghbi H.Y. Orr H.T. Cell. 1998; 95: 41-53Abstract Full Text Full Text PDF PubMed Scopus (890) Google Scholar, 5Matilla A. Roberson E.D. Banfi S. Morales J. Armstrong D.L. Burright E.N. Orr H.T. Sweatt J.D. Zoghbi H.Y. Matzuk M.M. J. Neurosci. 1998; 18: 5508-5516Crossref PubMed Google Scholar). One pathological hallmark of poly-Q disorders is the presence of neuronal aggregates (nuclear or cytoplasmic) that contain the poly-Q-expanded protein. These aggregates are found as nuclear inclusions (NIs) in SCA1 neurons, and in addition to aggregated mutant ataxin-1, they also contain components of the protein quality control machinery, e.g. ubiquitin, proteasome subunits, and chaperones. Such quality control proteins are key players in the toxicity of ataxin-1 and other proteins involved in poly-Q diseases (6Ciechanover A. Brundin P. Neuron. 2003; 40: 427-446Abstract Full Text Full Text PDF PubMed Scopus (817) Google Scholar, 7Cummings C.J. Mancini M.A. Antalffy B. DeFranco D.B. Orr H.T. Zoghbi H.Y. Nat. Genet. 1998; 19: 148-154Crossref PubMed Scopus (752) Google Scholar, 8Cummings C.J. Reinstein E. Sun Y. Antalffy B. Jiang Y. Ciechanover A. Orr H.T. Beaudet A.L. Zoghbi H.Y. Neuron. 1999; 24: 879-892Abstract Full Text Full Text PDF PubMed Scopus (446) Google Scholar, 9Cummings C.J. Sun Y. Opal P. Antalffy B. Mestril R. Orr H.T. Dillmann W.H. Zoghbi H.Y. Hum. Mol. Genet. 2001; 10: 1511-1518Crossref PubMed Scopus (423) Google Scholar). Interestingly, high levels of unexpanded ataxin-1 form NIs and cause degenerative phenotypes similar to, but milder than, the phenotypes induced by expanded ataxin-1 both in Drosophila and mouse SCA1 models (10Fernandez-Funez P. Nino-Rosales M.L. de Gouyon B. She W.C. Luchak J.M. Martinez P. Turiegano E. Benito J. Capovilla M. Skinner P.J. McCall A. Canal I. Orr H.T. Zoghbi H.Y. Botas J. Nature. 2000; 408: 101-106Crossref PubMed Scopus (549) Google Scholar). Overexpression of either a human ataxin-1 deletion construct lacking the poly-Q repeat or dAtx1 (the Drosophila ataxin-1 orthologue, which also lacks the N-terminal poly-Q tract) have been found to cause toxicity in two different fly models (3Tsuda H. Jafar-Nejad H. Patel A.J. Sun Y. Chen H.K. Rose M.F. Venken K.J. Botas J. Orr H.T. Bellen H.J. Zoghbi H.Y. Cell. 2005; 122: 633-644Abstract Full Text Full Text PDF PubMed Scopus (160) Google Scholar, 11Mizutani A. Wang L. Rajan H. Vig P.J. Alaynick W.A. Thaler J.P. Tsai C.C. EMBO J. 2005; 24: 3339-3351Crossref PubMed Scopus (68) Google Scholar). Taken together these observations suggest that poly-Q expansion favors a toxic and aggregation-prone conformation in ataxin-1 that the protein backbone may already have a tendency to adopt. Chaperones and the ubiquitin proteasome system are responsible for maintaining the cell environment free of toxic misfolded proteins (12Ma Y. Hendershot L.M. Cell. 2001; 107: 827-830Abstract Full Text Full Text PDF PubMed Scopus (348) Google Scholar, 13Wickner S. Maurizi M.R. Gottesman S. Science. 1999; 286: 1888-1893Crossref PubMed Scopus (916) Google Scholar). Although not well understood, there is a tight regulatory mechanism that decides when a protein is refolded and when it needs to be degraded. One link that connects chaperones and the ubiquitin-proteasome machinery, possibly acting as a regulator, is the co-chaperone CHIP (C terminus of Hsc70 interacting protein) (14Cyr D.M. Hohfeld J. Patterson C. Trends Biochem. Sci. 2002; 27: 368-375Abstract Full Text Full Text PDF PubMed Scopus (294) Google Scholar, 15Wiederkehr T. Bukau B. Buchberger A. Curr. Biol. 2002; 12: R26-R28Abstract Full Text Full Text PDF PubMed Scopus (68) Google Scholar). CHIP has three tetratricopeptide repeat (TPR) domains that allow it to interact with chaperones (16Ballinger P. Y. Patterson C. Mol. Cell. Biol. 1999; 19: PubMed Scopus Google as well as a that co-chaperone with an E3 ubiquitin ligase J. Y. D.M. Hohfeld J. Patterson C. J. Biol. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar). CHIP has been to in the protein quality control machinery different the of misfolded proteins (14Cyr D.M. Hohfeld J. Patterson C. Trends Biochem. Sci. 2002; 27: 368-375Abstract Full Text Full Text PDF PubMed Scopus (294) Google Scholar, 15Wiederkehr T. Bukau B. Buchberger A. Curr. Biol. 2002; 12: R26-R28Abstract Full Text Full Text PDF PubMed Scopus (68) Google Scholar, S. T. J. Biochem. Biol. 2003; PubMed Scopus Google Scholar, S. M. M. PubMed Scopus Google Scholar). CHIP also cause of proteins in an B. Patterson C. Mol. Cell. Biol. 2003; 23: PubMed Scopus Google and the in C. Y. H. L. Patterson C. EMBO J. 2003; PubMed Scopus Google Scholar). CHIP is to interact with aggregation-prone proteins implicated in degenerative diseases protecting against their toxicity. these proteins are poly-Q-expanded poly-Q-expanded N-terminal and M. J. M. S. S. R. J. PubMed Scopus Google Scholar, Y. J. Patterson C. P.J. J. Biol. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar, H. J. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar, L. J. H. A. M. E. J. J. Dillmann W.H. A. R. Y. B. J. M. Hum. Mol. Genet. PubMed Scopus Google Scholar, A. E. M.R. J. Neurosci. 2005; PubMed Scopus Google Scholar, P. A. S. S. J. Biol. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar, S. M. T. M. E. R. A. J. PubMed Scopus Google Scholar, S. H. Biochem. PubMed Scopus Google Scholar). the ability of CHIP to and protect against we its ability to ataxin-1-induced and used it as a to investigate the toxicity in unexpanded ataxin-1. Here we CHIP is to interact with both expanded and unexpanded ataxin-1 proteins and for by their CHIP to ataxin-1 NIs in and human SCA1 neurons. CHIP suppresses triggered by either expanded or unexpanded ataxin-1 by their steady-state levels in a Drosophila model of Finally we investigate the importance of the protein backbone for CHIP We find that CHIP has against the toxicity caused by a poly-Q tract but is very effective in protecting against a similar poly-Q tract in the context of a protein backbone. ataxin-1 or in CHIP, ubiquitin in MOPS, for Hsp70 with and to with and in in with of FLAG-tagged ataxin-1 and human CHIP in and and to with for ataxin-1 ubiquitination in in with FLAG-tagged ataxin-1 human CHIP mutant and mutant hemaglutinin-tagged ubiquitin the with for and and to with with and by and by with The used as and mouse and of FLAG-tagged ataxin-1 and human CHIP in by with in culture as in 7Cummings C.J. Mancini M.A. Antalffy B. DeFranco D.B. Orr H.T. Zoghbi H.Y. Nat. Genet. 1998; 19: 148-154Crossref PubMed Scopus (752) Google with either or in and by Drosophila by a coding for human CHIP in the Drosophila PubMed Google Scholar). Drosophila by construct in and have been (10Fernandez-Funez P. Nino-Rosales M.L. de Gouyon B. She W.C. Luchak J.M. Martinez P. Turiegano E. Benito J. Capovilla M. Skinner P.J. McCall A. Canal I. Orr H.T. Zoghbi H.Y. Botas J. Nature. 2000; 408: 101-106Crossref PubMed Scopus (549) Google Scholar). a by P. other from the from eye imaginal from in in of and a and in the with and mouse or a and Drosophila imaginal from different in and with for or the we used and H.K. P. Kaytor M.D. A. Orr H.T. Botas J. Zoghbi H.Y. Cell. 2003; Full Text Full Text PDF PubMed Scopus Google Scholar). of Brain from a SCA1 and a control in and in from the of both and to CHIP used as a in the used for and of Drosophila for scanning electron and (10Fernandez-Funez P. Nino-Rosales M.L. de Gouyon B. She W.C. Luchak J.M. Martinez P. Turiegano E. Benito J. Capovilla M. Skinner P.J. McCall A. Canal I. Orr H.T. Zoghbi H.Y. Botas J. Nature. 2000; 408: 101-106Crossref PubMed Scopus (549) Google Scholar). with in of and in and to with an to a from the imaginal eye of different the and with and for with from the The of to allow a of of SCA1 with for which as an The used are as SCA1, and and and and CHIP with and Ataxin-1 in CHIP and expanded ataxin-1 we in of ataxin-1 Overexpression of unexpanded ataxin-1 to neurodegenerative phenotypes in Drosophila and mouse models that are similar to, but milder than, the degeneration caused by ataxin-1 (10Fernandez-Funez P. Nino-Rosales M.L. de Gouyon B. She W.C. Luchak J.M. Martinez P. Turiegano E. Benito J. Capovilla M. Skinner P.J. McCall A. Canal I. Orr H.T. Zoghbi H.Y. Botas J. Nature. 2000; 408: 101-106Crossref PubMed Scopus (549) Google Scholar). by we CHIP is to interact with a ataxin-1 protein the poly-Q We a with CHIP and an ataxin-1 protein with only human ataxin-1 has in that ataxin-1 also The that CHIP interacts with the ataxin-1 protein backbone supports the idea that unexpanded ataxin-1 has a tendency to The CHIP and ataxin-1 may be or by chaperones that are to interact with both CHIP and ataxin-1 in and other C.J. Mancini M.A. Antalffy B. DeFranco D.B. Orr H.T. Zoghbi H.Y. Nat. Genet. 1998; 19: 148-154Crossref PubMed Scopus (752) Google Scholar, P. Nino-Rosales M.L. de Gouyon B. She W.C. Luchak J.M. Martinez P. Turiegano E. Benito J. Capovilla M. Skinner P.J. McCall A. Canal I. Orr H.T. Zoghbi H.Y. Botas J. Nature. 2000; 408: 101-106Crossref PubMed Scopus (549) Google Scholar, P. Y. Patterson C. Mol. Cell. Biol. 1999; 19: PubMed Scopus Google Scholar, J. Y. D.M. Hohfeld J. Patterson C. J. Biol. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar, S. M. M. PubMed Scopus Google Scholar, H.K. P. Kaytor M.D. A. Orr H.T. Botas J. Zoghbi H.Y. Cell. 2003; Full Text Full Text PDF PubMed Scopus Google Scholar). CHIP to Ataxin-1 in and from SCA1 used to CHIP and ataxin-1 co-localize in CHIP and expanded ataxin-1. in CHIP in ataxin-1 NIs in that CHIP may have a role in the of aggregated mutant ataxin-1 in CHIP also to unexpanded ataxin-1 NIs the idea that unexpanded ataxin-1 investigate the interactions are for SCA1 we the of human CHIP from a SCA1 or control brain CHIP to the in of control and is not in the CHIP in of the NIs in the SCA1 brain that we of CHIP to the NIs in SCA1 a role for CHIP in the of expanded ataxin-1 in CHIP and Ataxin-1 in interactions ataxin-1 and CHIP suggest that CHIP may ataxin-1 ubiquitination and it for we in vitro ubiquitination ataxin-1 or ataxin-1 with the ubiquitination machinery components CHIP as the E3 We found that CHIP promotes ubiquitination of both expanded and unexpanded ataxin-1 proteins that unexpanded ataxin-1 an conformation in the of the poly-Q CHIP not a control protein as in 1. Hsp70 CHIP-mediated Ataxin-1 in Hsp70 ataxin-1 toxicity and is also to interact with CHIP C.J. Mancini M.A. Antalffy B. DeFranco D.B. Orr H.T. Zoghbi H.Y. Nat. Genet. 1998; 19: 148-154Crossref PubMed Scopus (752) Google Scholar, 9Cummings C.J. Sun Y. Opal P. Antalffy B. Mestril R. Orr H.T. Dillmann W.H. Zoghbi H.Y. Hum. Mol. Genet. 2001; 10: 1511-1518Crossref PubMed Scopus (423) Google Scholar, P. Nino-Rosales M.L. de Gouyon B. She W.C. Luchak J.M. Martinez P. Turiegano E. Benito J. Capovilla M. Skinner P.J. McCall A. Canal I. Orr H.T. Zoghbi H.Y. Botas J. Nature. 2000; 408: 101-106Crossref PubMed Scopus (549) Google Scholar, P. Y. Patterson C. Mol. Cell. Biol. 1999; 19: PubMed Scopus Google we the of Hsp70 CHIP-mediated ataxin-1 Hsp70 to the in vitro ubiquitination The addition of Hsp70 in ubiquitination of ataxin-1 when with CHIP similar for ataxin-1 Hsp70 interacts with misfolded these the idea that a of unexpanded ataxin-1 an CHIP Ataxin-1 in and a ataxin-1 ubiquitination is with the proteasome and The levels of ataxin-1 are in and CHIP investigate the in CHIP is for ataxin-1 ubiquitination in we used a mutant CHIP with a and to an in ataxin-1 ubiquitination when with These in vitro that CHIP is to ataxin-1 for in and are in with the role of the in an for interactions with the ubiquitin M. M. S.M. M. P. C. Mol. Cell. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar). domains in CHIP have been to interact with chaperones (16Ballinger P. Y. Patterson C. Mol. Cell. Biol. 1999; 19: PubMed Scopus Google Scholar). We ataxin-1 ubiquitination in and a CHIP construct with a from these to ataxin-1 ubiquitination when with from that interactions with chaperones are required for CHIP-mediated ataxin-1 ubiquitination in CHIP the of Ataxin-1 in a Drosophila of ubiquitination of ataxin-1 by CHIP and its in NIs in both cell culture and SCA1 suggest that CHIP may protect against ataxin-1-induced we used a well characterized model of We have that in the Drosophila eye causes a degenerative (10Fernandez-Funez P. Nino-Rosales M.L. de Gouyon B. She W.C. Luchak J.M. Martinez P. Turiegano E. Benito J. Capovilla M. Skinner P.J. McCall A. Canal I. Orr H.T. Zoghbi H.Y. Botas J. Nature. 2000; 408: 101-106Crossref PubMed Scopus (549) Google Scholar). The fly a CHIP for which are we the eye of and a control with the of together with human CHIP CHIP used for and to as and the of CHIP protein and a eye characterized by and as well as loss and these degeneration by in the of the and CHIP and a of the and as well as phenotypes and The of is the of CHIP protein with ataxin-1 as the effects of with the steady-state levels of expanded ataxin-1 in the levels of in the eye fly the levels of CHIP in in with and mouse as a the levels of ataxin-1 in eye imaginal from of the by with and mouse as a ataxin-1 in control ataxin-1 levels of and a in the and of ataxin-1 levels when with either or in the of and different levels of and ataxin-1 that from the to the part of the of either or with causes a in the of the ataxin-1 with and and in causes a in the ataxin-1 with and I. for and for by of the the of with the control with and and in of the of CHIP not cause a in the of the SCA1 used as a control for the are as CHIP Overexpression the of Ataxin-1 in the that CHIP against by ataxin-1 for we the of ataxin-1 protein in and different levels of we the levels of ataxin-1 by cell loss in the eye due to we used eye imaginal to ataxin-1 ataxin-1 is in eye CHIP and in The in the of ataxin-1 to the of CHIP expanded ataxin-1 only the protein we also the levels of ataxin-1 by to both the and the aggregated of ataxin-1 imaginal and CHIP a in ataxin-1 when with and the to the of CHIP protein These be CHIP with the system used to we CHIP the of from a control of by and as well as not eye and different levels of CHIP to a in the of we the that a CHIP-mediated in the of ataxin-1 protein is caused by of SCA1 We eye imaginal either and or and The of in the context of the and are similar the and data that the effects of CHIP ataxin-1 are the protein CHIP the and the of CHIP promotes ubiquitination and is ataxin-1 we it is to interact with unexpanded ataxin-1 in We the of CHIP in two different unexpanded human SCA1 and The protein the used not these causes a eye and a in similar to that caused by The protein and causes a the of suppresses both the eye and phenotypes caused by and and the of We also ataxin-1 levels in eye and or and different levels of in the of ataxin-1 CHIP to a in the of unexpanded ataxin-1 to the of CHIP for CHIP against observations that CHIP against both expanded and unexpanded suggest that the protein backbone is for by We the ability of CHIP to protect from expanded polyglutamine tracts in the context of different protein we a bare polyglutamine tract with only a short as a backbone. of the in the eye causes a P. S. Science. 2000; PubMed Scopus Google with and loss these degeneration with and of the and eye phenotypes CHIP We also of a similar 128Q tract in the context of an N-terminal of the huntingtin protein of in the eye causes not causes degeneration with with that CHIP is to the phenotypes caused by of in the The different effects of CHIP ataxin-1 NT-Htt[128Q], or may be caused by in the levels of the investigate we of these from the eye used to caused from cell loss that of the of the toxic when that 127Q-HA, the toxic is a the or the of not the of CHIP to its toxicity. The different effects of CHIP ataxin-1 NT-Htt[128Q], or a of the of these polyglutamine to the ataxin-1 and not contain a for These the importance of protein context for polyglutamine-induced neurodegeneration. CHIP a regulatory function in the protein quality control machinery of the cell (14Cyr D.M. Hohfeld J. Patterson C. Trends Biochem. Sci. 2002; 27: 368-375Abstract Full Text Full Text PDF PubMed Scopus (294) Google Scholar, 15Wiederkehr T. Bukau B. Buchberger A. Curr. Biol. 2002; 12: R26-R28Abstract Full Text Full Text PDF PubMed Scopus (68) Google and has been implicated in the of disorders characterized by protein misfolding and M. J. M. S. S. R. J. PubMed Scopus Google Scholar, Y. J. Patterson C. P.J. J. Biol. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar, H. J. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar, L. J. H. A. M. E. J. J. Dillmann W.H. A. R. Y. B. J. M. Hum. Mol. Genet. PubMed Scopus Google Scholar, A. E. M.R. J. Neurosci. 2005; PubMed Scopus Google Scholar, P. A. S. S. J. Biol. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar, S. M. T. M. E. R. A. J. PubMed Scopus Google Scholar, S. H. Biochem. PubMed Scopus Google Scholar). Here we investigate the CHIP and ataxin-1 and its for SCA1 We find that CHIP interacts with expanded ataxin-1 in and is to ataxin-1 NIs in cell culture. CHIP also to the ataxin-1 NIs in human SCA1 from CHIP ubiquitinates expanded ataxin-1 in vitro and in cell culture and Hsp70 we ataxin-1 ubiquitination with a CHIP protein a in the that is to interactions with chaperones (16Ballinger P. Y. Patterson C. Mol. Cell. Biol. 1999; 19: PubMed Scopus Google Scholar). it that chaperone is for CHIP ubiquitination function in has been that CHIP interacts with and the of other E3 Y. M. S. T. T. R. Mol. Cell. 2002; 10: Full Text Full Text PDF PubMed Scopus Google the that in ataxin-1 ubiquitination is by an E3 ligase other investigate we used a mutant lacking E3 ligase CHIP mutant to ataxin-1 ubiquitination that CHIP directly ubiquitinates ataxin-1. we of CHIP is to a neurodegenerative caused by expanded ataxin-1 in a Drosophila model of We found that CHIP decreases expanded ataxin-1-induced toxicity in the Drosophila The of is with levels of with the cell culture ubiquitination we find that of CHIP to levels of expanded ataxin-1 in Drosophila as by and Taken together these observations that CHIP a role in SCA1 by expanded ataxin-1 for in a chaperone These are with CHIP as a of other polyglutamine proteins by P. A. S. S. J. Biol. 2005; Full Text Full Text PDF PubMed Scopus Google and A. E. M.R. J. Neurosci. 2005; PubMed Scopus Google Scholar). of poly-Q tracts are to cause to of in the Chaperones and these misfolded proteins in an to to their (12Ma Y. Hendershot L.M. Cell. 2001; 107: 827-830Abstract Full Text Full Text PDF PubMed Scopus (348) Google Scholar, 13Wickner S. Maurizi M.R. Gottesman S. Science. 1999; 286: 1888-1893Crossref PubMed Scopus (916) Google Scholar). Interestingly, we find that CHIP not only interacts with expanded ataxin-1 but also with the unexpanded in that ataxin-1 a toxic conformation in the of the poly-Q addition CHIP ubiquitinates unexpanded ataxin-1, and is by to ataxin-1, CHIP to and the of expanded or huntingtin but not their unexpanded P. A. S. S. J. Biol. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar). other poly-Q ataxin-1 may a misfolded toxic conformation that is by the poly-Q of idea unexpanded ataxin-1, or aggregates and triggers when high levels (10Fernandez-Funez P. Nino-Rosales M.L. de Gouyon B. She W.C. Luchak J.M. Martinez P. Turiegano E. Benito J. Capovilla M. Skinner P.J. McCall A. Canal I. Orr H.T. Zoghbi H.Y. Botas J. Nature. 2000; 408: 101-106Crossref PubMed Scopus (549) Google Scholar). These and other observations J.R. Zoghbi H.Y. Nat. Rev. Genet. 2005; 6: 743-755Crossref PubMed Scopus (633) Google Scholar, 3Tsuda H. Jafar-Nejad H. Patel A.J. Sun Y. Chen H.K. Rose M.F. Venken K.J. Botas J. Orr H.T. Bellen H.J. Zoghbi H.Y. Cell. 2005; 122: 633-644Abstract Full Text Full Text PDF PubMed Scopus (160) Google Scholar, 11Mizutani A. Wang L. Rajan H. Vig P.J. Alaynick W.A. Thaler J.P. Tsai C.C. EMBO J. 2005; 24: 3339-3351Crossref PubMed Scopus (68) Google Scholar, C.C. H.Y. A. E. Rajan H. M. Sci. S. A. PubMed Scopus Google Scholar, Kaytor M.D. T. Zoghbi H.Y. Clark H.B. Orr H.T. Neuron. 2003; Full Text Full Text PDF PubMed Scopus Google function of ataxin-1 in SCA1 and they also suggest that protein context is for neurodegeneration. We used Drosophila to the effects of CHIP either a 127Q tract or an N-terminal huntingtin with a 128Q we not of the toxicity caused by the 127Q CHIP suppresses the The in the ability of CHIP to protect against caused by expanded poly-Q tracts the importance of the protein context in polyglutamine-induced neurodegeneration. These data be when the of poly-Q models that an protein These models may not of the human e.g. in the proteins that are required for or other mouse models of SCA1 and of the to of the neurodegenerative T. Kaytor M.D. Zoghbi H.Y. Clark H.B. Orr H.T. J. Neurosci. 24: PubMed Scopus Google Scholar, A. R. Cell. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar). These and the of of polyglutamine-induced such as CHIP the for for SCA1 and other polyglutamine diseases We the of and and B. for and the human J. for with the SEM, R. for with P. for the and the for other Drosophila with