Bortezomib-resistant mutant proteasomes: structural and biochemical evaluation with carfilzomib and ONX 0914

Structure. 2015 Feb 3;23(2):407-17. doi: 10.1016/j.str.2014.11.019. Epub 2015 Jan 15.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Boronic Acids / metabolism
  • Boronic Acids / pharmacology*
  • Bortezomib
  • Catalytic Domain / genetics
  • Crystallography, X-Ray
  • Drug Resistance, Neoplasm / genetics*
  • Models, Molecular*
  • Molecular Structure
  • Mutagenesis
  • Mutation / genetics
  • Oligopeptides / chemistry*
  • Proteasome Endopeptidase Complex / chemistry*
  • Proteasome Endopeptidase Complex / genetics
  • Proteasome Endopeptidase Complex / metabolism
  • Protein Conformation
  • Pyrazines / metabolism
  • Pyrazines / pharmacology*
  • X-Ray Diffraction
  • Yeasts


  • Boronic Acids
  • Oligopeptides
  • PR-957
  • Pyrazines
  • Bortezomib
  • carfilzomib
  • Proteasome Endopeptidase Complex