title: Bortezomib-resistant mutant proteasomes: structural and biochemical evaluation with carfilzomib and ONX 0914.
abstract: Inhibition of the 20S proteasome by bortezomib (Velcade) constitutes a successfully applied therapy for blood cancer. However, emerging resistance restricts its medicinal use. For example, mutations in the proteolytically active β5-subunit of the proteasome, the main target of inhibitors, were reported to impair drug binding and thus to reduce therapeutic efficacy. Using yeast as a model system, we describe here a systematic evaluation of these mutations by cell growth analysis, proteasome inhibition assays, and X-ray crystallography. The 11 mutants examined display decreased proliferation rates, impaired proteolytic activity, and marked resistance to bortezomib as well as the α',β'-epoxyketone inhibitors carfilzomib (Kyprolis) and ONX 0914, while the second-generation compound carfilzomib was the least affected. In total, 49 proteasome X-ray structures, including structural data on proteasome-carfilzomib complexes, reveal three distinct molecular mechanisms that hamper both drug binding and natural substrate turnover to an extent that is still compatible with cell survival.
authors.affiliation: Center for Integrated Protein Science at the Department Chemie, Lehrstuhl für Biochemie, Technische Universität München, Lichtenbergstraße 4, 85747 Garching, Germany. Electronic address: eva.huber@mytum.de.
authors.forename: Eva M
authors.initials: EM
authors.lastname: Huber
authors.affiliation: Center for Integrated Protein Science at the Department Chemie, Lehrstuhl für Biochemie, Technische Universität München, Lichtenbergstraße 4, 85747 Garching, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Heinemeyer
authors.affiliation: Center for Integrated Protein Science at the Department Chemie, Lehrstuhl für Biochemie, Technische Universität München, Lichtenbergstraße 4, 85747 Garching, Germany. Electronic address: michael.groll@tum.de.
authors.forename: Michael
authors.initials: M
authors.lastname: Groll
mesh_terms: D001897:Boronic Acids / Q000378:metabolism / Q000494:pharmacology*; D000069286:Bortezomib; D020134:Catalytic Domain / Q000235:genetics; D018360:Crystallography, X-Ray; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D008958:Models, Molecular; D015394:Molecular Structure; D016296:Mutagenesis; D009154:Mutation / Q000235:genetics; D009842:Oligopeptides / Q000737:chemistry*; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D011719:Pyrazines / Q000378:metabolism / Q000494:pharmacology*; D014961:X-Ray Diffraction; D015003:Yeasts
chemical_list: D001897:Boronic Acids; D009842:Oligopeptides; C542291:PR-957; D011719:Pyrazines; D000069286:Bortezomib; C524865:carfilzomib; D046988:Proteasome Endopeptidase Complex