title: Inhibition of Proteasome Activity Induces Formation of Alternative Proteasome Complexes.
abstract: The proteasome is an intracellular protease complex consisting of the 20S catalytic core and its associated regulators, including the 19S complex, PA28αβ, PA28γ, PA200, and PI31. Inhibition of the proteasome induces autoregulatory de novo formation of 20S and 26S proteasome complexes. Formation of alternative proteasome complexes, however, has not been investigated so far. We here show that catalytic proteasome inhibition results in fast recruitment of PA28γ and PA200 to 20S and 26S proteasomes within 2-6 h. Rapid formation of alternative proteasome complexes did not involve transcriptional activation of PA28γ and PA200 but rather recruitment of preexisting activators to 20S and 26S proteasome complexes. Recruitment of proteasomal activators depended on the extent of active site inhibition of the proteasome with inhibition of β5 active sites being sufficient for inducing recruitment. Moreover, specific inhibition of 26S proteasome activity via siRNA-mediated knockdown of the 19S subunit RPN6 induced recruitment of only PA200 to 20S proteasomes, whereas PA28γ was not mobilized. Here, formation of alternative PA200 complexes involved transcriptional activation of the activator. Alternative proteasome complexes persisted when cells had regained proteasome activity after pulse exposure to proteasome inhibitors. Knockdown of PA28γ sensitized cells to proteasome inhibitor-mediated growth arrest. Thus, formation of alternative proteasome complexes appears to be a formerly unrecognized but integral part of the cellular response to impaired proteasome function and altered proteostasis.
authors.affiliation: From the Comprehensive Pneumology Center (CPC), University Hospital, Ludwig-Maximilians University, Helmholtz Zentrum München, Member of the German Center for Lung Research (DZL), 81377 Munich, Germany.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Welk
authors.affiliation: the Centre de Recherche de Biochimie Macromoléculaire (CRBM-CNRS UMR 5237), Université de Montpellier, 34293 Montpellier, France, and.
authors.forename: Olivier
authors.initials: O
authors.lastname: Coux
authors.affiliation: From the Comprehensive Pneumology Center (CPC), University Hospital, Ludwig-Maximilians University, Helmholtz Zentrum München, Member of the German Center for Lung Research (DZL), 81377 Munich, Germany.
authors.forename: Vera
authors.initials: V
authors.lastname: Kleene
authors.affiliation: the Centre de Recherche de Biochimie Macromoléculaire (CRBM-CNRS UMR 5237), Université de Montpellier, 34293 Montpellier, France, and.
authors.forename: Claire
authors.initials: C
authors.lastname: Abeza
authors.affiliation: the Institute of Developmental Genetics, Helmholtz Zentrum München, 85764 Neuherberg, Germany.
authors.forename: Dietrich
authors.initials: D
authors.lastname: Trümbach
authors.affiliation: From the Comprehensive Pneumology Center (CPC), University Hospital, Ludwig-Maximilians University, Helmholtz Zentrum München, Member of the German Center for Lung Research (DZL), 81377 Munich, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Eickelberg
authors.affiliation: From the Comprehensive Pneumology Center (CPC), University Hospital, Ludwig-Maximilians University, Helmholtz Zentrum München, Member of the German Center for Lung Research (DZL), 81377 Munich, Germany, silke.meiners@helmholtz-muenchen.de.
authors.forename: Silke
authors.initials: S
authors.lastname: Meiners
mesh_terms: D001324:Autoantigens / Q000378:metabolism; D000069286:Bortezomib / Q000494:pharmacology; D002478:Cells, Cultured; D055785:Gene Knockdown Techniques; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism; D009842:Oligopeptides / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D061988:Proteasome Inhibitors / Q000494:pharmacology; D055503:Protein Multimerization; D014158:Transcription, Genetic
chemical_list: D001324:Autoantigens; D000069286:Bortezomib; D009687:Nuclear Proteins; D009842:Oligopeptides; D046988:Proteasome Endopeptidase Complex; D061988:Proteasome Inhibitors; C099558:Ki antigen; C554738:ONX 0912; C521188:PSME4 protein, human
keywords: PA200; PA28γ; enzyme inhibitor; proteasome; protein degradation; proteolysis; proteostasis