title: Aggregation properties of the small nuclear ribonucleoprotein U1-70K in Alzheimer disease.
abstract: Recent evidence indicates that U1-70K and other U1 small nuclear ribonucleoproteins are Sarkosyl-insoluble and associate with Tau neurofibrillary tangles selectively in Alzheimer disease (AD). Currently, the mechanisms underlying the conversion of soluble nuclear U1 small nuclear ribonucleoproteins into insoluble cytoplasmic aggregates remain elusive. Based on the biochemical and subcellular distribution properties of U1-70K in AD, we hypothesized that aggregated U1-70K itself or other biopolymers (e.g. proteins or nucleic acids) interact with and sequester natively folded soluble U1-70K into insoluble aggregates. Here, we demonstrate that total homogenates from AD brain induce soluble U1-70K from control brain or recombinant U1-70K to become Sarkosyl-insoluble. This effect was not dependent on RNA and did not correlate with detergent-insoluble Tau levels as AD homogenates with reduced levels of these components were still capable of inducing U1-70K aggregation. In contrast, proteinase K-treated AD homogenates and Sarkosyl-soluble AD fractions were unable to induce U1-70K aggregation, indicating that aggregated proteins in AD brain are responsible for inducing soluble U1-70K aggregation. It was determined that the C terminus of U1-70K, which harbors two disordered low complexity (LC) domains, is necessary for U1-70K aggregation. Moreover, both LC1 and LC2 domains were sufficient for aggregation. Finally, protein cross-linking and mass spectrometry studies demonstrated that a U1-70K fragment harboring the LC1 domain directly interacts with aggregated U1-70K in AD brain. Our results support a hypothesis that aberrant forms of U1-70K in AD can directly sequester soluble forms of U1-70K into insoluble aggregates.
authors.affiliation: From the Departments of Biochemistry and the Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, Georgia 30322.
authors.forename: Ian
authors.initials: I
authors.lastname: Diner
authors.affiliation: the Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, Georgia 30322 Neurology.
authors.forename: Chadwick M
authors.initials: CM
authors.lastname: Hales
authors.affiliation: From the Departments of Biochemistry and the Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, Georgia 30322.
authors.forename: Isaac
authors.initials: I
authors.lastname: Bishof
authors.affiliation: From the Departments of Biochemistry and the Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, Georgia 30322.
authors.forename: Lake
authors.initials: L
authors.lastname: Rabenold
authors.affiliation: From the Departments of Biochemistry and the Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, Georgia 30322.
authors.forename: Duc M
authors.initials: DM
authors.lastname: Duong
authors.affiliation: Emory University School of Medicine, Atlanta, Georgia 30322 Robert P. Apkarian Integrated Electron Microscopy Core.
authors.forename: Hong
authors.initials: H
authors.lastname: Yi
authors.affiliation: Emory University School of Medicine, Atlanta, Georgia 30322 Division of Microbiology, and Yerkes Research Center, Emory University, Atlanta, Georgia 30322.
authors.forename: Oskar
authors.initials: O
authors.lastname: Laur
authors.affiliation: the Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, Georgia 30322 the Departments of Experimental Pathology and.
authors.forename: Marla
authors.initials: M
authors.lastname: Gearing
authors.affiliation: Pathology and Neurology, Johns Hopkins School of Medicine, Baltimore, Maryland 21205.
authors.forename: Juan
authors.initials: J
authors.lastname: Troncoso
authors.affiliation: the NIA, National Institutes of Health, Baltimore, Maryland 21224, and.
authors.forename: Madhav
authors.initials: M
authors.lastname: Thambisetty
authors.affiliation: the Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, Georgia 30322 Neurology.
authors.forename: James J
authors.initials: JJ
authors.lastname: Lah
authors.affiliation: the Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, Georgia 30322 Neurology.
authors.forename: Allan I
authors.initials: AI
authors.lastname: Levey
authors.affiliation: From the Departments of Biochemistry and the Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, Georgia 30322 Neurology, nseyfri@emory.edu.
authors.forename: Nicholas T
authors.initials: NT
authors.lastname: Seyfried
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000378:metabolism*; D001344:Autopsy; D015153:Blotting, Western; D001921:Brain / Q000378:metabolism* / Q000473:pathology / Q000648:ultrastructure; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D013058:Mass Spectrometry; D016253:Microscopy, Immunoelectron; D008875:Middle Aged; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D017412:Ribonucleoprotein, U1 Small Nuclear / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D012521:Sarcosine / Q000031:analogs & derivatives / Q000737:chemistry; D012995:Solubility
chemical_list: D010446:Peptide Fragments; D011994:Recombinant Proteins; D017412:Ribonucleoprotein, U1 Small Nuclear; C490688:SNRNP70 protein, human; C025231:sarkosyl; D012521:Sarcosine
keywords: Neurodegenerative Disease; Protein Aggregation; RNA; Spliceosome; Tau Protein (Tau)