title: Chaperone activities of the 26S and 20S proteasome.
abstract: The accumulation of misfolded or damaged proteins causes the failure of normal cell structure and functions necessary for growth and viability. To abort this adverse development, defective proteins must be rapidly repaired by molecular chaperones or destroyed by energy-dependent cytoplasmic proteases. A balance among these processes ultimately maintains cellular homeostasis. In eukaryotes, the 26S proteasome, a protease/chaperone complex, is a central component in the protein triage decision process. The 26S proteasome generally acts as a ubiquitination system, though it also selectively degrades structurally abnormal proteins in an ubiquitin-independent manner. In either case, all substrate proteins must undergo structural changes and stabilization necessary for their rapid degradation. It has, therefore, often been suggested that several chaperone functions are closely related to the stimulation of proteasomal degradation. This review summarizes recent discoveries pertaining to chaperone activities in the proteasomal degradation pathway, and to their regulation of protein breakdown mediated by the proteasome.
authors.affiliation: Division of Enzyme Chemistry, Institute for Enzyme Research, The University of Tokushima, Tokushima 770-8503, Japan. yano@ier.tokushima-u.ac.jp
authors.forename: Mihiro
authors.initials: M
authors.lastname: Yano
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Kanesaki
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Koumoto
authors.forename: Masahiro
authors.initials: M
authors.lastname: Inoue
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kido
mesh_terms: D000818:Animals; D006801:Humans; D018832:Molecular Chaperones; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism*
chemical_list: D018832:Molecular Chaperones; D011506:Proteins; D025801:Ubiquitin; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease