title: Mutant ubiquitin found in Alzheimer's disease causes neuritic beading of mitochondria in association with neuronal degeneration.
abstract: A dinucleotide deletion in human ubiquitin (Ub) B messenger RNA leads to formation of polyubiquitin (UbB)+1, which has been implicated in neuronal cell death in Alzheimer's and other neurodegenerative diseases. Previous studies demonstrate that UbB+1 protein causes proteasome dysfunction. However, the molecular mechanism of UbB+1-mediated neuronal degeneration remains unknown. We now report that UbB+1 causes neuritic beading, impairment of mitochondrial movements, mitochondrial stress and neuronal degeneration in primary neurons. Transfection of UbB+1 induced a buildup of mitochondria in neurites and dysregulation of mitochondrial motor proteins, in particular, through detachment of P74, the dynein intermediate chain, from mitochondria and decreased mitochondria-microtubule interactions. Altered distribution of mitochondria was associated with activation of both the mitochondrial stress and p53 cell death pathways. These results support the hypothesis that neuritic clogging of mitochondria by UbB+1 triggers a cascade of events characterized by local activation of mitochondrial stress followed by global cell death. Furthermore, UbB+1 small interfering RNA efficiently blocked expression of UbB+1 protein, attenuated neuritic beading and preserved cellular morphology, suggesting a potential neuroprotective strategy for certain neurodegenerative disorders.
authors.affiliation: Department of Neurology, University of California, Irvine, CA 92697, USA. tanz@uci.edu
authors.forename: Z
authors.initials: Z
authors.lastname: Tan
authors.forename: X
authors.initials: X
authors.lastname: Sun
authors.forename: F-S
authors.initials: FS
authors.lastname: Hou
authors.forename: H-W
authors.initials: HW
authors.lastname: Oh
authors.forename: L G W
authors.initials: LG
authors.lastname: Hilgenberg
authors.forename: E M
authors.initials: EM
authors.lastname: Hol
authors.forename: F W
authors.initials: FW
authors.lastname: van Leeuwen
authors.forename: M A
authors.initials: MA
authors.lastname: Smith
authors.forename: D K
authors.initials: DK
authors.lastname: O'Dowd
authors.forename: S S
authors.initials: SS
authors.lastname: Schreiber
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism* / Q000473:pathology; D000818:Animals; D001483:Base Sequence; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D008870:Microtubules / Q000502:physiology / Q000648:ultrastructure; D008928:Mitochondria / Q000473:pathology* / Q000502:physiology; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D009410:Nerve Degeneration / Q000473:pathology* / Q000503:physiopathology; D009474:Neurons / Q000473:pathology* / Q000502:physiology; D011247:Pregnancy; D046988:Proteasome Endopeptidase Complex / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D025801:Ubiquitin / Q000235:genetics* / Q000378:metabolism*
chemical_list: D012333:RNA, Messenger; D034741:RNA, Small Interfering; D016159:Tumor Suppressor Protein p53; D025801:Ubiquitin; D046988:Proteasome Endopeptidase Complex