title: Proteasomes. A molecular census of 26S proteasomes in intact neurons.
abstract: The 26S proteasome is a key player in eukaryotic protein quality control and in the regulation of numerous cellular processes. Here, we describe quantitative in situ structural studies of this highly dynamic molecular machine in intact hippocampal neurons. We used electron cryotomography with the Volta phase plate, which allowed high fidelity and nanometer precision localization of 26S proteasomes. We undertook a molecular census of single- and double-capped proteasomes and assessed the conformational states of individual complexes. Under the conditions of the experiment—that is, in the absence of proteotoxic stress—only 20% of the 26S proteasomes were engaged in substrate processing. The remainder was in the substrate-accepting ground state. These findings suggest that in the absence of stress, the capacity of the proteasome system is not fully used.
authors.affiliation: Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, 82152 Martinsried, Germany.
authors.forename: Shoh
authors.initials: S
authors.lastname: Asano
authors.affiliation: Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, 82152 Martinsried, Germany.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Fukuda
authors.affiliation: Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, 82152 Martinsried, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Beck
authors.affiliation: Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, 82152 Martinsried, Germany.
authors.forename: Antje
authors.initials: A
authors.lastname: Aufderheide
authors.affiliation: Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, 82152 Martinsried, Germany.
authors.forename: Friedrich
authors.initials: F
authors.lastname: Förster
authors.affiliation: Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, 82152 Martinsried, Germany.
authors.forename: Radostin
authors.initials: R
authors.lastname: Danev
authors.affiliation: Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, 82152 Martinsried, Germany. baumeist@biochem.mpg.de.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Baumeister
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D006624:Hippocampus / Q000166:cytology* / Q000201:enzymology; D009474:Neurons / Q000201:enzymology* / Q000648:ultrastructure*; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry*; D011487:Protein Conformation; D051381:Rats; D013312:Stress, Physiological
chemical_list: D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease