Related Experiment Video
Updated: Apr 18, 2026
Chemical Inactivation of the E3 Ubiquitin Ligase Cereblon by Pomalidomide-based Homo-PROTACs
Published on: May 15, 2019
Bortezomib-resistant mutant proteasomes: structural and biochemical evaluation with carfilzomib and ONX 0914
Eva M Huber1, Wolfgang Heinemeyer1, Michael Groll1
1Center for Integrated Protein Science at the Department Chemie, Lehrstuhl für Biochemie, Technische Universität München, Lichtenbergstraße 4, 85747 Garching, Germany.
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.
Insights
Proteasome mutations conferring resistance to bortezomib and other inhibitors were systematically studied. These mutations decrease cell proliferation and proteolytic activity, impacting cancer therapy efficacy.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- Bortezomib (Velcade) is a proteasome inhibitor used in blood cancer therapy.
- Emerging drug resistance, often due to mutations in the proteasome's β5-subunit, limits therapeutic efficacy.
- Understanding these resistance mechanisms is crucial for developing more effective treatments.
Purpose of the Study:
- To systematically evaluate the impact of specific mutations in the proteasome's β5-subunit on drug resistance.
- To elucidate the molecular mechanisms underlying resistance to proteasome inhibitors.
- To assess the efficacy of different proteasome inhibitors against mutated proteasomes.
Main Methods:
- Cell growth analysis of yeast mutants.
- Proteasome inhibition assays.
- X-ray crystallography of proteasome mutants and drug complexes.
Main Results:
- Eleven examined β5-subunit mutants showed decreased proliferation and impaired proteolytic activity.
- Mutants exhibited resistance to bortezomib, carfilzomib (Kyprolis), and ONX 0914.
- Carfilzomib demonstrated the least impact among the tested inhibitors.
- 49 proteasome X-ray structures revealed three molecular mechanisms hindering drug binding and substrate turnover.
Conclusions:
- Proteasome mutations can confer resistance to multiple inhibitors by affecting drug binding and substrate processing.
- These resistance mechanisms allow cell survival despite impaired proteasome function.
- Structural insights provide a basis for designing next-generation proteasome inhibitors that overcome resistance.
Related Concept Videos
02:18The Proteasome
In this pathway, the target proteins are first tagged with small proteins called ubiquitin. A series of enzymes carry out the ubiquitination of the target proteins - E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3...
02:56Treatment Resistent Cancers
01:17The Proteasome Structure
The proteasome is an...