title: Oxidative modification of proteasome: identification of an oxidation-sensitive subunit in 26 S proteasome.
abstract: Reactive oxygen species (ROS) have the potential to damage cellular components, such as protein, resulting in loss of function and structural alteration of proteins. The oxidative process affects a variety of side amino acid groups, some of which are converted to carbonyl compounds. We have previously shown that a prostaglandin D2 metabolite, 15-deoxy-delta(12,14)-prostaglandin J2 (15d-PGJ2), is the potent inducer of intracellular oxidative stress on human neuroblastoma SH-SY5Y cells [Kondo, M., Oya-Ito, T., Kumagai, T., Osawa, T., and Uchida, K. (2001) Cyclopentenone prostaglandins as potential inducers of intracellular oxidative stress, J. Biol. Chem. 276, 12076-12083]. In the present study, to elucidate the molecular mechanism underlying the oxidative stress-mediated cell degeneration, we analyzed the protein carbonylation on SH-SY5Y cells when these cells were submitted to an endogenous inducer of ROS production. Upon exposure of SH-SY5Y cells to this endogenous electrophile, we observed significant accumulation of protein carbonyls within the cells. Proteomic analysis of oxidation-sensitive proteins showed that the major intracellular target of protein carbonylation was one of the regulatory subunits in 26 S proteasome, S6 ATPase. Accompanied by a dramatic increase in protein carbonyls within S6 ATPase, the electrophile-induced oxidative stress exerted a significant decrease in the S6 ATPase activities and a decreased ability of the 26 S proteasome to degrade substrates. Moreover, in vitro oxidation of 26 S proteasome with a metal-catalyzed oxidation system also confirmed that S6 ATPase represents the most oxidation-sensitive subunit in the proteasome. These and the observation that down-regulation of S6 ATPase by RNA interference resulted in the enhanced accumulation of ubiquitinated proteins suggest that S6 ATPase is a molecular target of ROS under conditions of electrophile-induced oxidative stress and that oxidative modification of this regulatory subunit of proteasome may be functionally associated with the altered recognition and degradation of proteasomal substrates in the cells.
authors.affiliation: Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Ishii
authors.forename: Toyo
authors.initials: T
authors.lastname: Sakurai
authors.forename: Hiroko
authors.initials: H
authors.lastname: Usami
authors.forename: Koji
authors.initials: K
authors.lastname: Uchida
mesh_terms: D000595:Amino Acid Sequence; D045744:Cell Line, Tumor; D006801:Humans; D008969:Molecular Sequence Data; D018384:Oxidative Stress; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry / Q000378:metabolism*; D034622:RNA Interference; D017382:Reactive Oxygen Species
chemical_list: D017382:Reactive Oxygen Species; D046988:Proteasome Endopeptidase Complex