title: Inhibition of proteasomal activity causes inclusion formation in neuronal and non-neuronal cells overexpressing Parkin.
abstract: Association between protein inclusions and neurodegenerative diseases, including Parkinson's and Alzheimer's diseases, and polyglutamine disorders, has been widely documented. Although ubiquitin is conjugated to many of these aggregated proteins, the 26S proteasome does not efficiently degrade them. Mutations in the ubiquitin-protein ligase Parkin are associated with autosomal recessive juvenile Parkinsonism. Although Parkin-positive inclusions are not detected in brains of autosomal recessive juvenile Parkinsonism patients, Parkin is found in Lewy bodies in sporadic disease. This suggests that loss of Parkin ligase activity via mutation, or sequestration to Lewy bodies, is a contributory factor to sporadic disease onset. We now demonstrate that decreased proteasomal activity causes formation of large, noncytotoxic inclusions within the cytoplasm of both neuronal and nonneuronal cells overexpressing Parkin. This is not a general phenomenon as there is an absence of similar inclusions when HHARI, a structural homolog of Parkin, is overexpressed. The inclusions colocalize with ubiquitin and with proteasomes. Furthermore, Parkin inclusions colocalize with gamma-tubulin, acetylated alpha-tubulin, and cause redistribution of vimentin, suggesting aggresome-like properties. Our data imply that lower proteasomal activity, previously observed in brain tissue of Parkinson's disease patients, leads to Parkin accumulation and a concomitant reduction in ligase activity, thereby promoting Lewy body formation.
authors.affiliation: Molecular Medicine Unit, University of Leeds, St. James's University Hospital, Leeds LS9 7TF, United Kingdom. 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: Alexander F
authors.initials: AF
authors.lastname: Markham
authors.forename: Philip A
authors.initials: PA
authors.lastname: Robinson
mesh_terms: D000818:Animals; D019556:COS Cells; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular; D003546:Cysteine Endopeptidases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D002479:Inclusion Bodies / Q000201:enzymology* / Q000235:genetics; D007976:Leupeptins / Q000494:pharmacology; D020961:Lewy Body Disease / Q000235:genetics / Q000378:metabolism; D018613:Microscopy, Confocal; D009097:Multienzyme Complexes / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D009997:Osmotic Pressure / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects; D010300:Parkinson Disease / Q000235:genetics / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D013012:Sorbitol / Q000494:pharmacology; D014404:Tubulin / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014415:Tunicamycin / Q000494:pharmacology; D025801:Ubiquitin / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*; D014746:Vimentin / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D015853:Cysteine Proteinase Inhibitors; D007976:Leupeptins; D009097:Multienzyme Complexes; D014404:Tubulin; D025801:Ubiquitin; D014746:Vimentin; D014415:Tunicamycin; D013012:Sorbitol; D006861:Hydrogen Peroxide; C419193:ARIH1 protein, human; D044767:Ubiquitin-Protein Ligases; C111567:parkin protein; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde