Proteasome inhibitor b-AP15 induces enhanced proteotoxicity by inhibiting cytoprotective aggresome formation

Hillert, Ellin-Kristina; Brnjic, Slavica; Zhang, Xiaonan; Mazurkiewicz, Magdalena; Saei, Amir Ata; Mofers, Arjan; Selvaraju, Karthik; Zubarev, Roman A.; Linder, Stig; D’Arcy, Pádraig

doi:10.1016/j.canlet.2019.02.003

Cited by 24 publications

(27 citation statements)

References 261 publications

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“…This pattern is distinct from that observed during treatment with VXL1570, where decreases in heavy polysomes were preferentially observed. We nevertheless considered the possibility of functional chaperone depletion considering previous findings of proteasome deubiquitinase inhibitors inducing high levels of proteotoxic stress [27,28,41,42]. We did not, however, observe decreases in HSC70/HSP70 proteins on translating ribosomes in ALL cells, but rather increased association of chaperones to polysomes.…”

Section: Discussionmentioning

confidence: 75%

“…Proteasome deubiquitinase inhibitors induce high levels of expression of Hsp70 mRNA transcripts, particularly the highly inducible isoform HSPA6 [ 27 , 28 , 41 , 42 ]. We found that Hsp70B′ (encoded by the HSPA6 gene) did not increase in a dose-dependent manner in MOLT-4 and SUP-B15 cells ( Figure 5 B).…”

Section: Resultsmentioning

confidence: 99%

“…of cycloheximide during the preparation of lysates from VLX1570-treated cells had no detectable effect on polysome profiles ( Figure 5A). Proteasome deubiquitinase inhibitors induce high levels of expression of Hsp70 mRNA transcripts, particularly the highly inducible isoform HSPA6 [27,28,41,42]. We found that Hsp70B′ (encoded by the HSPA6 gene) did not increase in a dose-dependent manner in MOLT-4 and SUP-B15 cells ( Figure 5B).…”

Section: Evidence For Elongational Block By Vlx1570 Treatmentmentioning

confidence: 85%

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Induction of ER Stress in Acute Lymphoblastic Leukemia Cells by the Deubiquitinase Inhibitor VLX1570

Pellegrini

Selvaraju

Faustini

et al. 2020

IJMS

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The proteasome is a validated target of cancer therapeutics. Inhibition of proteasome activity results in the activation of the unfolded protein response (UPR) characterized by phosphorylation of eukaryotic initiation factor 2α (eIF2α), global translational arrest, and increased expression of the proapoptotic CHOP (C/EBP homologous protein) protein. Defects in the UPR response has been reported to result in altered sensitivity of tumor cells to proteasome inhibitors. Here, we characterized the effects of the deubiquitinase (DUB) inhibitor VLX1570 on protein homeostasis, both at the level of the UPR and on protein translation, in acute lymphoblastic leukemia (ALL). Similar to the 20S inhibitor bortezomib, VLX1570 induced accumulation of polyubiquitinated proteins and increased expression of the chaperone Grp78/Bip in ALL cells. Both compounds induced cleavage of PARP (Poly (ADP-ribose) polymerase) in ALL cells, consistent with induction of apoptosis. However, and in contrast to bortezomib, VLX1570 treatment resulted in limited induction of the proapoptotic CHOP protein. Translational inhibition was observed by both bortezomib and VLX1570. We report that in distinction to bortezomib, suppression of translation by VXL1570 occurred at the level of elongation. Increased levels of Hsc70/Hsp70 proteins were observed on polysomes following exposure to VLX1570, possibly suggesting defects in nascent protein folding. Our findings demonstrate apoptosis induction in ALL cells that appears to be uncoupled from CHOP induction, and show that VLX1570 suppresses protein translation by a mechanism distinct from that of bortezomib.

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Section: Discussionmentioning

confidence: 75%

Section: Resultsmentioning

confidence: 99%

Section: Evidence For Elongational Block By Vlx1570 Treatmentmentioning

confidence: 85%

See 1 more Smart Citation

Induction of ER Stress in Acute Lymphoblastic Leukemia Cells by the Deubiquitinase Inhibitor VLX1570

Pellegrini

Selvaraju

Faustini

et al. 2020

IJMS

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“…Gene expression signatures of b-AP15 from the connectivity map database suggested that b-AP15 shared similarities with other potent proteasome inhibitors, such as BTZ. However, b-AP15 and BTZ target different subunits of proteasome, and due to the different inhibition of the proteasome, b-AP15 is able to disrupt the protect mechanism of forming aggresomes in cancer cells exposed to BTZ [228]. Additionally, the data showed that b-AP15 induced a dose-dependent aggregation of conjugated ubiquitin, suggesting inhibition of the degradation activity of the DUBs [131].…”

Section: B-ap15mentioning

confidence: 97%

Drug Development Targeting the Ubiquitin–Proteasome System (UPS) for the Treatment of Human Cancers

Zhang

Linder

Bazzaro

2020

Cancers

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Cancer cells are characterized by a higher rate of protein turnover and greater demand for protein homeostasis compared to normal cells. In this scenario, the ubiquitin-proteasome system (UPS), which is responsible for the degradation of over 80% of cellular proteins within mammalian cells, becomes vital to cancer cells, making the UPS a critical target for the discovery of novel cancer therapeutics. This review systematically categorizes all current reported small molecule inhibitors of the various essential components of the UPS, including ubiquitin-activating enzymes (E1s), ubiquitin-conjugating enzymes (E2s), ubiquitin ligases (E3s), the 20S proteasome catalytic core particle (20S CP) and the 19S proteasome regulatory particles (19S RP), as well as their mechanism/s of action and limitations. We also discuss the immunoproteasome which is considered as a prospective therapeutic target of the next generation of proteasome inhibitors in cancer therapies.Cancers 2020, 12, 902 2 of 34 core component of the nucleosome, which is critical for transcription and cell cycle, is recognized and linked by Lysine Residue 48 (K48) and further degraded by the proteasome [17,18]; DbpB (also named Y-box protein 1), a transcription factor, is reported to selectively recognize the Y-box promoter element. Studies showed that its terminal 105-amino-acid-long fragment is removed after a specific proteolytic cleavage by the proteasome complex [19,20]; NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) is located outside the nucleus and is reported to be involved in DNA transcription as well as cell survival [21,22]. The NF-κB p105 is the precursor of NF-κB p50. It is evident that NF-κB p105 is cleaved and selectively degraded at the C-terminus by proteasome, generating the active form of NF-κB p50 [23]. Products of UPS degradation can also be further degraded into single amino acids by aminopeptidases [24]. Aminopeptidases are the class of enzymes that catalyze the final steps in the ubiquitin-proteasome pathway by breaking down shorter peptides (<5 residues) into even smaller fragments [25]. Many, but not all, of aminopeptidases, are zinc metalloenzymes, such as leucine aminopeptidases (lAPs) and methionine aminopeptidases (metAPs) [26,27]. Studies showed that blocking the activity of the aminopeptidases by inhibitor of bestatin could generate a major accumulation of peptides which are ∼2-5 residues long [28].The 26S proteasome contains one/two 19S regulatory particles (19S RP) which mainly regulate the translocation of ubiquitinated proteins to the 20S CP and one 20S core particle (20S CP) in which proteolysis finally occurs [29,30]. In general, two main processes are associated with the process of degradation of proteins by the UPS: (1) tagging the to-be-degraded proteins by polyubiquitination (normally more than four ubiquitins), and (2) proteolytic degradation of the polyubiquitinated protein by the 26S proteasome complex [31,32]. Each step incorporates an intricate and complex spectrum of protein interaction...

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“…These observations suggested that proteasomal degradation is disrupted in Bmf-deficient cells. When proteasomal degradation is inhibited, the accumulated proteins are confined in inclusion bodies as aggregates to decrease their cell toxicity (Hillert, Brnjic et al, 2019, Takahashi, Kitaura et al, 2018. Therefore, we investigated whether bmf +/-MAECs present with accumulation of proteins in the "insoluble fraction" that is solubilized only with high concentrations of SDS and DDT.…”

Section: Bmf Enhances Proteasomal Degradationmentioning

confidence: 99%

Bmf Facilitates Protein Degradation and Reduces Beclin1 Ubiquitination to Inhibit Autophagy Independent of mTOR

Delgado-Vergas

Fort

Tassew

et al. 2020

Preprint

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Previous observations suggested that Bcl-2 modifying factor (Bmf) affects autophagy but the underlying mechanisms were unknown. The present studies show that Bmf inhibited the initiation and flux of autophagy in a manner that is independent of the mTOR pathway and inhibition of mTOR increased Bmf expression to temper the autophagic cell death. In mice, emphysema was observed in Bmf-deficient mice, suggesting that Bmf suppresses autophagic cell death of alveolar type II cells. Bmf deficiency increased ubiquitination of Beclin1 with K63 chains and released Beclin1 from Bcl-2. However, Bmf deficiency also increased the levels of polyubiquitinated proteins in general. In mice, Bmf-deficiency robustly increased p62 levels in all tissues analyzed, but LC3-II levels were reduced only in the hearts of old mice. Also, Bmfdeficiency caused persistent mucous cell metaplasia in mice exposed to allergen and increased levels of polyubiquitinated Muc5ac in differentiated airway epithelial cells. The reduction of ubiquitinated proteins was mediated by the BH3-and dynein binding-domains of Bmf.Together, these findings show that the primary role of Bmf is to reduce protein levels and affects K63-and K48-ubiqutination.

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Proteasome inhibitor b-AP15 induces enhanced proteotoxicity by inhibiting cytoprotective aggresome formation

Cited by 24 publications

References 261 publications

Induction of ER Stress in Acute Lymphoblastic Leukemia Cells by the Deubiquitinase Inhibitor VLX1570

Induction of ER Stress in Acute Lymphoblastic Leukemia Cells by the Deubiquitinase Inhibitor VLX1570

Drug Development Targeting the Ubiquitin–Proteasome System (UPS) for the Treatment of Human Cancers

Bmf Facilitates Protein Degradation and Reduces Beclin1 Ubiquitination to Inhibit Autophagy Independent of mTOR

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