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Combined treatment of human multiple myeloma cells with bortezomib and doxorubicin alters the interactome of 20S proteasomes.

ABSTRACT: The proteasome is the key player in targeted degradation of cellular proteins and serves as a therapeutic target for treating several blood malignancies. Although in general, degradation of proteins via the proteasome requires their ubiquitination, a subset of proteins can be degraded independently of their ubiquitination by direct interaction with subunits of the 20S proteasome core. Thus, investigation of the proteasome-associated proteins may help identify novel targets of proteasome degradation and provide important insights into the mechanisms of malignant cell proteostasis. Here, using biochemical purification of proteasomes from multiple myeloma (MM) cells followed by mass-spectrometry we have uncovered 77 proteins in total that specifically interacted with the 20S proteasome via its PSMA3 subunit. Our GST pull-down assays followed by western blots validated the interactions identified by mass-spectrometry. Eleven proteins were confirmed to bind PSMA3 only upon apoptotic conditions induced by a combined treatment with the proteasome inhibitor, bortezomib, and genotoxic drug, doxorubicin. Nine of these eleven proteins contained bioinformatically predicted intrinsically disordered regions thus making them susceptible to ubiquitin-independent degradation. Importantly, among those proteins five interacted with the ubiquitin binding affinity matrix suggesting that these proteins may also be ubiquitinylated and hence degraded via the ubiquitin-dependent pathway. Collectively, these PSMA3-interacting proteins represent novel potential substrates for 20S proteasomes upon apoptosis. Furthermore, these data may shed light on the molecular mechanisms of cellular response to chemotherapy. ABBREVIATIONS:BD: bortezomib/doxorubicin treatment; CDK: cyclin-dependent kinases; CHCA: ?-cyanohydroxycinnamic acid; IDP: intrinsically disordered proteins; IDR: intrinsically disordered regions; IPG: immobilized pI gradient; MALDI TOF/TOF: matrix-assisted laser desorption/ionization time-of-flight tandem mass-spectrometry; MM: multiple myeloma; ODC: ornithine decarboxylase; PI: proteasomal inhibitors; PSMA: alpha-type 20S proteasome subunits; PTMs: post-translational modifications; SDS-PAGE: sodium dodecylsulphate polyacrylamide gel electrophoresis; UIP: ubiquitin-independent proteasomal proteolysis.

SUBMITTER: Mittenberg AG

PROVIDER: S-EPMC6133333 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Combined treatment of human multiple myeloma cells with bortezomib and doxorubicin alters the interactome of 20S proteasomes.

Mittenberg Alexey G AG Kuzyk Valeria O VO Shabelnikov Sergey V SV Gorbach Daria P DP Shatrova Alla N AN Fedorova Olga A OA Barlev Nickolai A NA

Cell cycle (Georgetown, Tex.) 20180801 14

The proteasome is the key player in targeted degradation of cellular proteins and serves as a therapeutic target for treating several blood malignancies. Although in general, degradation of proteins via the proteasome requires their ubiquitination, a subset of proteins can be degraded independently of their ubiquitination by direct interaction with subunits of the 20S proteasome core. Thus, investigation of the proteasome-associated proteins may help identify novel targets of proteasome degradat ...[more]

PMID: 30009671

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Project description:Previous results from an interim analysis of an open-label, randomized, phase 3 study demonstrated that bortezomib combined with pegylated liposomal doxorubicin (PLD) was superior to bortezomib monotherapy in patients with relapsed/refractory multiple myeloma who had previously received one or more lines of therapy. Protocol-defined final survival data from that study are provided here.Patients were randomized (1:1) to receive either bortezomib alone (1.3 mg/m(2) intravenously on days 1, 4, 8, and 11 of every 21-day cycle) or bortezomib-PLD (bortezomib plus PLD 30 mg/m(2) intravenously on day 4). The primary endpoint was the time to progression. Secondary efficacy endpoints included overall survival (OS), progression-free survival, and the overall response rate.In total, 646 patients (bortezomib-PLD, n = 324; bortezomib alone, n = 322) were randomized between December, 2004, and March, 2006. On the clinical cutoff date (May 16, 2014) for the final survival analysis, at a median follow-up of 103 months, 79% of patients had died (bortezomib-PLD group: 253 of 324 patients; 78%; bortezomib alone group: 257 of 322 patients; 80%). The median OS in the bortezomib-PLD group was 33 months (95% confidence interval [CI], 28.9-37.1) versus 30.8 months (95% CI, 25.2-36.5) in the bortezomib alone group (hazard ratio, 1.047; 95% CI, 0.879-1.246; P = .6068). Salvage therapies included conventional and novel drugs, which were well balanced between the two treatment groups.Despite inducing a superior time to progression, long-term follow-up revealed that PLD-bortezomib did not improve OS compared with bortezomib alone in patients with relapsed/refractory multiple myeloma. The inability to sustain the early observed survival advantage may have been caused by the effects of subsequent lines of therapy, and underscores the need for long-term follow-up of phase 3 trials while recognizing the challenge of having adequate power to detect long-term differences in OS. Cancer 2016;122:2050-6. © 2016 American Cancer Society.

Dataset Information

Combined treatment of human multiple myeloma cells with bortezomib and doxorubicin alters the interactome of 20S proteasomes.

Publications

Combined treatment of human multiple myeloma cells with bortezomib and doxorubicin alters the interactome of 20S proteasomes.

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