title: Binding of amyloid beta protein to the 20 S proteasome.
abstract: Neurodegenerative disorders of aging are characterized by the intraneuronal accumulation of ubiquitin conjugates into tangles and inclusions. Ubiquitin conjugates are degraded by cellular particles known as proteasomes. We have previously shown that amyloid beta protein (Abeta) inhibits proteasomal activity and thereby blocks ubiquitin conjugate degradation. In the present studies, we found that Abeta binds the 20 S proteasome and forms a proteasome-Abeta complex. The complex was detected by Western blot with anti-Abeta antibodies. Using a 1.4 nm Nanogold-labeled Abeta, we visualized proteasome-Abeta complexes by scanning transmission electron microscopy (STEM). Analysis of the side-on oriented proteasome-Abeta complexes revealed a single gold particle, corresponding to one gold-labeled Abeta, in the middle portion of the proteasome. On end-on views of proteasome-Abeta complexes, gold was detected within the area delimited by the proteasome circular projection. Both STEM views are consistent with Abeta localization inside the proteasome along the peptide channel. Direct interaction of Abeta with the inner catalytic compartment of the proteasome may explain the generation of ubiquitin-containing lesions in Alzheimer's disease and other neurodegenerative disorders. In addition, detection of Nanogold-labeled peptide inside the 20 S eukaryotic proteasome suggests that conformational constraints for protein degradation in eukaryotic proteasomes are different from those in archaebacteria proteasomes.
authors.affiliation: Department of Psychiatry and Behavioral Science, School of Medicine, State University of New York, Stony Brook 11794, USA.
authors.forename: L
authors.initials: L
authors.lastname: Gregori
authors.forename: J F
authors.initials: JF
authors.lastname: Hainfeld
authors.forename: M N
authors.initials: MN
authors.lastname: Simon
authors.forename: D
authors.initials: D
authors.lastname: Goldgaber
mesh_terms: D016229:Amyloid beta-Peptides / Q000378:metabolism* / Q000648:ultrastructure; D003546:Cysteine Endopeptidases / Q000378:metabolism* / Q000648:ultrastructure; D015853:Cysteine Proteinase Inhibitors; D046911:Macromolecular Substances; D017348:Microscopy, Electron, Scanning Transmission; D009097:Multienzyme Complexes / Q000378:metabolism* / Q000648:ultrastructure; D009410:Nerve Degeneration; D046988:Proteasome Endopeptidase Complex; D011485:Protein Binding; D014452:Ubiquitins / Q000378:metabolism
chemical_list: D016229:Amyloid beta-Peptides; D015853:Cysteine Proteinase Inhibitors; D046911:Macromolecular Substances; D009097:Multienzyme Complexes; D014452:Ubiquitins; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex