title: UCH-L1 aggresome formation in response to proteasome impairment indicates a role in inclusion formation in Parkinson's disease.
abstract: Aggresomes are associated with many neurodegenerative disorders, including Parkinson's disease, and polyglutamine disorders such as Huntington's disease. These inclusions commonly contain ubiquitylated proteins. The stage at which these proteins are ubiquitylated remains unclear. A malfunction of the ubiquitin/proteasome system (UPS) may be associated with their formation. Conversely, it may reflect an unsuccessful attempt by the cell to remove them. Previously, we demonstrated that overexpression of Parkin, a ubiquitin-protein ligase associated with autosomal recessive juvenile Parkinsonism, generates aggresome-like inclusions in UPS compromised cells. Mutations in the de-ubiquitylating enzyme, UCH-L1, cause a rare form of Parkinsonism. We now demonstrate that overexpression of UCH-L1 also forms ribbon-like aggresomes in response to proteasomal inhibition. Disease-associated mutations, which affect enzymatic activities, significantly increased the number of inclusions. UCH-L1 aggresomes co-localized with ubiquitylated proteins, HSP70, gamma-tubulin and, to a lesser extent, the 20S proteasome and the chaperone BiP. Similar to Parkin inclusions, we found UCH-L1 aggresomes to be surrounded by a tubulin rather than a vimentin cage-like structure. Furthermore, UCH-L1 aggregates with Parkin and alpha-synuclein in some, but not all inclusions, suggesting the heterogeneous nature of these inclusion bodies. This study provides additional evidence that aggregation-prone proteins are likely to recruit UPS components in an attempt to clear proteins from failing proteasomes. Furthermore, UCH-L1 accumulation is likely to play a pathological role in inclusion formation in Parkinson's disease.
authors.affiliation: Molecular Medicine Unit, University of Leeds, Clinical Sciences Building, St. James's University Hospital, Leeds, UK. h.c.ardley@leeds.ac.uk
authors.forename: Helen C
authors.initials: HC
authors.lastname: Ardley
authors.forename: Gina B
authors.initials: GB
authors.lastname: Scott
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Rose
authors.forename: Nancy G S
authors.initials: NG
authors.lastname: Tan
authors.forename: Philip A
authors.initials: PA
authors.lastname: Robinson
mesh_terms: D000818:Animals; D019556:COS Cells; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D002522:Chlorocebus aethiops; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D000091342:Endoplasmic Reticulum Chaperone BiP; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D002479:Inclusion Bodies / Q000737:chemistry / Q000378:metabolism* / Q000473:pathology; D016631:Lewy Bodies / Q000378:metabolism / Q000473:pathology; D046911:Macromolecular Substances; D018832:Molecular Chaperones / Q000378:metabolism; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009474:Neurons / Q000378:metabolism* / Q000473:pathology; D010300:Parkinson Disease / Q000235:genetics* / Q000378:metabolism; D011233:Precipitin Tests; D046988:Proteasome Endopeptidase Complex; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012995:Solubility; D051843:Synucleins; D014162:Transfection; D014404:Tubulin / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism; D043222:Ubiquitin Thiolesterase / Q000235:genetics* / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D051844:alpha-Synuclein
chemical_list: D002352:Carrier Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; D004791:Enzyme Inhibitors; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D046911:Macromolecular Substances; D018832:Molecular Chaperones; D009097:Multienzyme Complexes; D009419:Nerve Tissue Proteins; D011993:Recombinant Fusion Proteins; C497604:SNCA protein, human; D051843:Synucleins; D014404:Tubulin; C482860:UCHL1 protein, human; D025801:Ubiquitin; D051844:alpha-Synuclein; D044767:Ubiquitin-Protein Ligases; C111567:parkin protein; D043222:Ubiquitin Thiolesterase; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex