Abstract 951: CB-5083 is a novel first in class p97 inhibitor that disrupts cellular protein homeostasis and demonstrates anti-tumor activity in solid and hematological models

Proteasomes are central regulators of protein homeostasis in eukaryotes. Proteasome function is vulnerable to environmental insults, cellular protein imbalance and targeted pharmaceuticals. Yet, mechanisms that cells deploy to counteract inhibition of this central regulator are little understood. To find such mechanisms, we reduced flux through the proteasome to the point of toxicity with specific inhibitors and performed genome-wide screens for mutations that allowed cells to survive. Counter to expectation, reducing expression of individual subunits of the proteasome's 19S regulatory complex increased survival. Strong 19S reduction was cytotoxic but modest reduction protected cells from inhibitors. Protection was accompanied by an increased ratio of 20S to 26S proteasomes, preservation of protein degradation capacity and reduced proteotoxic stress. While compromise of 19S function can have a fitness cost under basal conditions, it provided a powerful survival advantage when proteasome function was impaired. This means of rebalancing proteostasis is conserved from yeast to humans.

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ER stress causes widespread protein aggregation and prion formation

The Journal of Cell Biology ◽

10.1083/jcb.201612165 ◽

2017 ◽

Vol 216 (8) ◽

pp. 2295-2304 ◽

Cited By ~ 28

Author(s):

Norfadilah Hamdan ◽

Paraskevi Kritsiligkou ◽

Chris M. Grant

Keyword(s):

Protein Aggregation ◽

Er Stress ◽

Secretory Pathway ◽

Cellular Protein ◽

Protein Homeostasis ◽

Er Quality Control ◽

Unfolded Protein ◽

The Unfolded Protein Response ◽

Protein Response ◽

Er Homeostasis

Disturbances in endoplasmic reticulum (ER) homeostasis create a condition termed ER stress. This activates the unfolded protein response (UPR), which alters the expression of many genes involved in ER quality control. We show here that ER stress causes the aggregation of proteins, most of which are not ER or secretory pathway proteins. Proteomic analysis of the aggregated proteins revealed enrichment for intrinsically aggregation-prone proteins rather than proteins which are affected in a stress-specific manner. Aggregation does not arise because of overwhelming proteasome-mediated degradation but because of a general disruption of cellular protein homeostasis. We further show that overexpression of certain chaperones abrogates protein aggregation and protects a UPR mutant against ER stress conditions. The onset of ER stress is known to correlate with various disease processes, and our data indicate that widespread amorphous and amyloid protein aggregation is an unanticipated outcome of such stress.

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Chaperones and Proteostasis: Role in Parkinson’s Disease

Diseases ◽

10.3390/diseases8020024 ◽

2020 ◽

Vol 8 (2) ◽

pp. 24 ◽

Cited By ~ 1

Author(s):

Neha Joshi ◽

Atchaya Raveendran ◽

Shirisha Nagotu

Keyword(s):

Parkinson’S Disease ◽

Parkinson's Disease ◽

Three Dimensional ◽

Cellular Protein ◽

The Body ◽

Dimensional Structure ◽

Protein Homeostasis ◽

Altered Expression ◽

And Function ◽

Related Proteins

Proper folding to attain a defined three-dimensional structure is a prerequisite for the functionality of a protein. Improper folding that eventually leads to formation of protein aggregates is a hallmark of several neurodegenerative disorders. Loss of protein homeostasis triggered by cellular stress conditions is a major contributing factor for the formation of these toxic aggregates. A conserved class of proteins called chaperones and co-chaperones is implicated in maintaining the cellular protein homeostasis. Expanding the body of evidence highlights the role of chaperones as central mediators in the formation, de-aggregation and degradation of the aggregates. Altered expression and function of chaperones is associated with many neurodegenerative diseases including Parkinson’s disease. Several studies indicate that chaperones are at the center of the cause and effect cycle of this disease. An overview of the various chaperones that are associated with homeostasis of Parkinson’s disease-related proteins and their role in pathogenicity will be discussed in this review.

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Proteasome inhibitor-induced modulation reveals the spliceosome as a specific therapeutic vulnerability in multiple myeloma

10.1101/508549 ◽

2018 ◽

Author(s):

Hector H. Huang ◽

Ian D. Ferguson ◽

Alexis M. Thornton ◽

Christine Lam ◽

Yu-Hsiu T. Lin ◽

...

Keyword(s):

Therapeutic Strategy ◽

Intron Retention ◽

Proteasome Inhibitors ◽

Protein Homeostasis ◽

New Approach ◽

Major Interest ◽

Specific Alternative ◽

Specific Vulnerability ◽

Related Proteins ◽

Anti Tumor Activity

AbstractEnhancing the efficacy of proteasome inhibitors is a central goal in myeloma therapy. We proposed that signaling-level responses after PI would reveal new mechanisms of action that could be therapeutically exploited. Unbiased phosphoproteomics after the PI carfilzomib surprisingly demonstrated the most prominent phosphorylation changes on splicing related proteins. Spliceosome modulation was invisible to RNA or protein abundance alone. Transcriptome analysis after PI demonstrated broad-scale intron retention, suggestive of spliceosome interference, as well as specific alternative splicing of protein homeostasis machinery components. These findings led us to evaluate direct spliceosome inhibition in myeloma, which synergized with carfilzomib and showed potent anti-tumor activity. Functional genomics and exome sequencing further supported the spliceosome as a specific vulnerability in myeloma. Our results propose splicing interference as an unrecognized modality of PI mechanism, reveal additional modes of spliceosome modulation, and suggest spliceosome targeting as a promising therapeutic strategy in myeloma.SignificanceNew ways to enhance PI efficacy are of major interest. We combine systems-level analyses to discover that PIs specifically interfere with splicing and that myeloma is selectively vulnerable to spliceosome inhibition. We reveal a new approach to advance myeloma therapy and uncover broader roles of splicing modulation in cancer.

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New Insights into the Pathogenesis of Alcohol-Induced ER Stress and Liver Diseases

International Journal of Hepatology ◽

10.1155/2014/513787 ◽

2014 ◽

Vol 2014 ◽

pp. 1-11 ◽

Cited By ~ 44

Author(s):

Cheng Ji

Keyword(s):

Liver Disease ◽

Alcohol Consumption ◽

Er Stress ◽

Liver Diseases ◽

Cell Cycle Progression ◽

Alcohol Exposure ◽

Cellular Protein ◽

Protein Homeostasis ◽

Lipid Species

Alcohol-induced liver disease increasingly contributes to human mortality worldwide. Alcohol-induced endoplasmic reticulum (ER) stress and disruption of cellular protein homeostasis have recently been established as a significant mechanism contributing to liver diseases. The alcohol-induced ER stress occurs not only in cultured hepatocytes but also in vivo in the livers of several species including mouse, rat, minipigs, zebrafish, and humans. Identified causes for the ER stress include acetaldehyde, oxidative stress, impaired one carbon metabolism, toxic lipid species, insulin resistance, disrupted calcium homeostasis, and aberrant epigenetic modifications. Importance of each of the causes in alcohol-induced liver injury depends on doses, duration and patterns of alcohol exposure, genetic disposition, environmental factors, cross-talks with other pathogenic pathways, and stages of liver disease. The ER stress may occur more or less all the time during alcohol consumption, which interferes with hepatic protein homeostasis, proliferation, and cell cycle progression promoting development of advanced liver diseases. Emerging evidence indicates that long-term alcohol consumption and ER stress may directly be involved in hepatocellular carcinogenesis (HCC). Dissecting ER stress signaling pathways leading to tumorigenesis will uncover potential therapeutic targets for intervention and treatment of human alcoholics with liver cancer.

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Ribosome collision sensor Hel2 recognizes mistargeting secretory ribosome-nascent chain complexes

10.1101/2020.12.28.424499 ◽

2020 ◽

Author(s):

Yoshitaka Matsuo ◽

Toshifumi Inada

Keyword(s):

Secretory Pathway ◽

Signal Recognition Particle ◽

Physiological Role ◽

Cellular Protein ◽

Ribosome Profiling ◽

Secretory Proteins ◽

Protein Homeostasis ◽

Chain Complexes ◽

Nascent Chain ◽

Endogenous Substrates

SummaryRibosome collision due to translational stalling is recognized as a problematic event in translation by E3 ubiquitin ligase Hel2, leading to non-canonical subunit dissociation followed by targeting of the faulty nascent peptides for degradation. Although Hel2-mediated quality control greatly contributes to maintaining cellular protein homeostasis, its physiological role in dealing with endogenous substrates remains unclear. This study utilized genome-wide analysis, based on selective ribosome profiling, to survey the endogenous substrates for Hel2. This survey revealed that Hel2 preferentially binds to the pre-engaged secretory ribosome-nascent-chain complexes (RNCs), which translate upstream of targeting signals. Notably, Hel2 recruitment into secretory RNCs was elevated under signal recognition particle (SRP)-deficient conditions. Moreover, the mitochondrial defects caused by insufficient SRP were enhanced by hel2 deletion, along with the mistargeting of secretory proteins into mitochondria. Collectively, these findings provide novel insights into risk management in the secretory pathway that maintains cellular protein homeostasis.

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Hsp70 machinery vs protein aggregation: the role of chaperones in cellular protein homeostasis

10.33612/diss.95000243 ◽

2019 ◽

Author(s):

Despina Serlidaki

Keyword(s):

Protein Aggregation ◽

Cellular Protein ◽

Protein Homeostasis

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How to design an optimal sensor network for the unfolded protein response

Molecular Biology of the Cell ◽

10.1091/mbc.e18-01-0060 ◽

2018 ◽

Vol 29 (25) ◽

pp. 3052-3062 ◽

Cited By ~ 3

Author(s):

Wylie Stroberg ◽

Hadar Aktin ◽

Yonatan Savir ◽

Santiago Schnell

Keyword(s):

Er Stress ◽

Unfolded Protein Response ◽

Cellular Protein ◽

Protein Accumulation ◽

Protein Homeostasis ◽

Unfolded Protein ◽

Stress Sensing ◽

Coarse Model ◽

The Unfolded Protein Response ◽

Protein Response

Cellular protein homeostasis requires continuous monitoring of stress in the endoplasmic reticulum (ER). Stress-detection networks control protein homeostasis by mitigating the deleterious effects of protein accumulation, such as aggregation and misfolding, with precise modulation of chaperone production. Here, we develop a coarse model of the unfolded protein response in yeast and use multi-objective optimization to determine which sensing and activation strategies optimally balance the trade-off between unfolded protein accumulation and chaperone production. By comparing a stress-sensing mechanism that responds directly to the level of unfolded protein in the ER to a mechanism that is negatively regulated by unbound chaperones, we show that chaperone-mediated sensors are more efficient than sensors that detect unfolded proteins directly. This results from the chaperone-mediated sensor having separate thresholds for activation and deactivation. Finally, we demonstrate that a sensor responsive to both unfolded protein and unbound chaperone does not further optimize homeostatic control. Our results suggest a strategy for designing stress sensors and may explain why BiP-mitigated ER stress-sensing networks have evolved.

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