Proteasome degrades soluble expanded polyglutamine completely and efficiently

To date, nine progressive neurodegenerative diseases are caused by expansion of the CAG repeat coding for polyglutamine, including Huntington's disease and several forms of spinocerebellar ataxia. Expanded polyglutamine causes dominant toxic gain-of-function related to its ability to aggregate. Polyglutamine aggregates inhibit the proteasome, suggesting that reduced degradation of misfolded proteins might contribute to polyglutamine toxicity. Moreover, several observations indicate that soluble proteins harboring expanded polyglutamine display altered turnover. To examine whether soluble polyglutamine interfered with proteasome-mediated degradation, we analyzed degradation of model proteasome substrates carrying either 103 or 25 glutamines in transfected cells. Expanded and normal size polyglutamine were degraded to completion and with similar efficiency. Moreover, targeting of expanded polyglutamine for proteasome-mediated degradation did not compromise proteasome activity. Thus, we propose that polyglutamine-containing disease proteins can be readily digested by the proteasome if they carried a degradation signal.

[1]  H. Paulson,et al.  Analysis of the Role of Heat Shock Protein (Hsp) Molecular Chaperones in Polyglutamine Disease , 1999, The Journal of Neuroscience.

[2]  E A Zemskov,et al.  Altered proteasomal function due to the expression of polyglutamine-expanded truncated N-terminal huntingtin induces apoptosis by caspase activation through mitochondrial cytochrome c release. , 2001, Human molecular genetics.

[3]  M. Perutz,et al.  Incorporation of glutamine repeats makes protein oligomerize: implications for neurodegenerative diseases. , 1995, Proceedings of the National Academy of Sciences of the United States of America.

[4]  T. Hashikawa,et al.  Intra- and Intermolecular β-Pleated Sheet Formation in Glutamine-repeat Inserted Myoglobin as a Model for Polyglutamine Diseases* , 2001, The Journal of Biological Chemistry.

[5]  M. Perutz,et al.  Glutamine repeats and inherited neurodegenerative diseases: molecular aspects. , 1996, Current opinion in structural biology.

[6]  J. Keller,et al.  Proteasomes and proteasome inhibition in the central nervous system. , 2001, Free radical biology & medicine.

[7]  S. A. Ross,et al.  A linear lattice model for polyglutamine in CAG-expansion diseases , 2002, Proceedings of the National Academy of Sciences of the United States of America.

[8]  A. Varshavsky.  The N-end rule , 1992, Cell.

[9]  K. Lindsten,et al.  Short-lived green fluorescent proteins for quantifying ubiquitin/proteasome-dependent proteolysis in living cells , 2000, Nature Biotechnology.

[10]  I. Kanazawa,et al.  Formic acid dissolves aggregates of an N-terminal huntingtin fragment containing an expanded polyglutamine tract: applying to quantification of protein components of the aggregates. , 2000, Biochemical and biophysical research communications.

[11]  H. Zoghbi,et al.  Glutamine repeats and neurodegeneration. , 2000, Annual review of neuroscience.

[12]  Harry T Orr,et al.  Mutation of the E6-AP Ubiquitin Ligase Reduces Nuclear Inclusion Frequency While Accelerating Polyglutamine-Induced Pathology in SCA1 Mice , 1999, Neuron.

[13]  A. Goldberg,et al.  Cellular Defenses against Unfolded Proteins A Cell Biologist Thinks about Neurodegenerative Diseases , 2001, Neuron.

[14]  R. Kopito,et al.  Impairment of the ubiquitin-proteasome system by protein aggregation. , 2001, Science.

[15]  C A Ross,et al.  When more is less: Pathogenesis of glutamine repeat neurodegenerative diseases , 1995, Neuron.

[16]  J T Finch,et al.  Glutamine repeats as polar zippers: their possible role in inherited neurodegenerative diseases. , 1994, Proceedings of the National Academy of Sciences of the United States of America.

[17]  M. F. Perutz,et al.  Cause of neural death in neurodegenerative diseases attributable to expansion of glutamine repeats , 2001, Nature.

[18]  S. W. Davies,et al.  Aggregation of huntingtin in neuronal intranuclear inclusions and dystrophic neurites in brain. , 1997, Science.

[19]  R. Albin,et al.  Ectopically Expressed CAG Repeats Cause Intranuclear Inclusions and a Progressive Late Onset Neurological Phenotype in the Mouse , 1997, Cell.

[20]  Martin Rechsteiner,et al.  Recognition of the polyubiquitin proteolytic signal , 2000, The EMBO journal.

[21]  Y. Agid,et al.  Polyglutamine expansion as a pathological epitope in Huntington's disease and four dominant cerebellar ataxias , 1995, Nature.

[22]  Aaron Ciechanover,et al.  The ubiquitin–proteasome pathway: on protein death and cell life , 1998, The EMBO journal.

[23]  K. Lindsten,et al.  Aggregate formation inhibits proteasomal degradation of polyglutamine proteins. , 2002, Human molecular genetics.

[24]  C. Olanow,et al.  Proteasome inhibition causes nigral degeneration with inclusion bodies in rats , 2002, Neuroreport.

[25]  Harry T Orr,et al.  SCA1 transgenic mice: A model for neurodegeneration caused by an expanded CAG trinucleotide repeat , 1995, Cell.

[26]  Mark Turmaine,et al.  Formation of Neuronal Intranuclear Inclusions Underlies the Neurological Dysfunction in Mice Transgenic for the HD Mutation , 1997, Cell.

[27]  Max F. Perutz,et al.  Glutamine repeats and neurodegenerative diseases: molecular aspects. , 1999, Trends in biochemical sciences.

[28]  E. Altschuler,et al.  Random coil conformation for extended polyglutamine stretches in aqueous soluble monomeric peptides. , 2009, The journal of peptide research : official journal of the American Peptide Society.

[29]  D. Housman,et al.  Insoluble detergent-resistant aggregates form between pathological and nonpathological lengths of polyglutamine in mammalian cells. , 1999, Proceedings of the National Academy of Sciences of the United States of America.

[30]  A. Matouschek,et al.  ATP-dependent proteases degrade their substrates by processively unraveling them from the degradation signal. , 2001, Molecular cell.

[31]  H. Paulson.  Toward an Understanding of Polyglutamine Neurodegeneration , 2000, Brain pathology.

[32]  Ronald Wetzel,et al.  Amyloid-like features of polyglutamine aggregates and their assembly kinetics. , 2002, Biochemistry.

[33]  A. Varshavsky,et al.  In vivo half-life of a protein is a function of its amino-terminal residue. , 1986, Science.

[34]  M. MacDonald,et al.  Mutant Huntingtin Forms in Vivo Complexes with Distinct Context-Dependent Conformations of the Polyglutamine Segment , 1999, Neurobiology of Disease.

[35]  S. Narumiya,et al.  Expanded polyglutamine in the Machado–Joseph disease protein induces cell death in vitro and in vivo , 1996, Nature Genetics.

[36]  A. Goldberg,et al.  Proteins are unfolded on the surface of the ATPase ring before transport into the proteasome. , 2001, Molecular cell.

[37]  René Hen,et al.  Reversal of Neuropathology and Motor Dysfunction in a Conditional Model of Huntington's Disease , 2000, Cell.

[38]  Ronald Wetzel,et al.  Huntington's disease age-of-onset linked to polyglutamine aggregation nucleation , 2002, Proceedings of the National Academy of Sciences of the United States of America.

[39]  Annalisa Pastore,et al.  Solution structure of polyglutamine tracts in GST‐polyglutamine fusion proteins , 2002, FEBS letters.

[40]  K. Fischbeck,et al.  Intranuclear Inclusions of Expanded Polyglutamine Protein in Spinocerebellar Ataxia Type 3 , 1997, Neuron.

[41]  Hans Lehrach,et al.  Huntingtin-Encoded Polyglutamine Expansions Form Amyloid-like Protein Aggregates In Vitro and In Vivo , 1997, Cell.