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Journal of Experimental & Clinical... Sep 2023Tumors have evolved in various mechanisms to evade the immune system, hindering the antitumor immune response and facilitating tumor progression. Immunotherapy has... (Review)
Review
Tumors have evolved in various mechanisms to evade the immune system, hindering the antitumor immune response and facilitating tumor progression. Immunotherapy has become a potential treatment strategy specific to different cancer types by utilizing multifarious molecular mechanisms to enhance the immune response against tumors. Among these mechanisms, the ubiquitin-proteasome system (UPS) is a significant non-lysosomal pathway specific to protein degradation, regulated by deubiquitinating enzymes (DUBs) that counterbalance ubiquitin signaling. Ubiquitin-specific proteases (USPs), the largest DUB family with the strongest variety, play critical roles in modulating immune cell function, regulating immune response, and participating in antigen processing and presentation during tumor progression. According to recent studies, the expressions of some USP family members in tumor cells are involved in tumor immune escape and immune microenvironment. This review explores the potential of targeting USPs as a new approach for cancer immunotherapy, highlighting recent basic and preclinical studies investigating the applications of USP inhibitors. By providing insights into the structure and function of USPs in cancer immunity, this review aims at assisting in developing new therapeutic approaches for enhancing the immunotherapy efficacy.
Topics: Humans; Immunotherapy; Cytoplasm; Proteasome Endopeptidase Complex; Ubiquitin; Ubiquitin-Specific Proteases; Neoplasms
PubMed: 37658402
DOI: 10.1186/s13046-023-02805-y -
Scientific Reports Sep 2023Klotho is an antiaging protein, and its levels decline with age and chronic stress. The exogenous administration of Klotho can enhance cognitive performance in mice and...
Klotho is an antiaging protein, and its levels decline with age and chronic stress. The exogenous administration of Klotho can enhance cognitive performance in mice and negatively modulate the Insulin/IGF1/PI3K/AKT pathway in terms of metabolism. In humans, insulin sensitivity is a hallmark of healthy longevity. Therefore, this study aimed to determine if exogenous Klotho, when added to neuronal and astrocytic cell cultures, could reduce the phosphorylation levels of certain insulin signaling effectors and enhance antioxidant strategies in these cells. Primary cell cultures of cortical astrocytes and neurons from mice were exposed to 1 nM Klotho for 24 h, with or without glucose. Klotho decreased pAKT and mTOR levels. However, in astrocytes, Klotho increased FOXO-3a activity and catalase levels, shielding them from intermediate oxidative stress. In neurons, Klotho did not alter FOXO-3 phosphorylation levels but increased proteasome activity, maintaining lower levels of PFKFB3. This study offers new insights into the roles of Klotho in regulating energy metabolism and the redox state in the brain.
Topics: Animals; Humans; Mice; Antioxidants; Astrocytes; Insulin; Neurons; Phosphatidylinositol 3-Kinases; Proteasome Endopeptidase Complex; Ubiquitin
PubMed: 37699938
DOI: 10.1038/s41598-023-41166-6 -
The EMBO Journal Aug 2023UBR5 is a nuclear E3 ligase that ubiquitinates a vast range of substrates for proteasomal degradation. This HECT domain-containing ubiquitin ligase has recently been...
UBR5 is a nuclear E3 ligase that ubiquitinates a vast range of substrates for proteasomal degradation. This HECT domain-containing ubiquitin ligase has recently been identified as an important regulator of oncogenes, e.g., MYC, but little is known about its structure or mechanisms of substrate engagement and ubiquitination. Here, we present the cryo-EM structure of human UBR5, revealing an α-solenoid scaffold with numerous protein-protein interacting motifs, assembled into an antiparallel dimer that adopts further oligomeric states. Using cryo-EM processing tools, we observe the dynamic nature of the UBR5 catalytic domain, which we postulate is important for its enzymatic activity. We characterise the proteasomal nuclear import factor AKIRIN2 as an interacting protein and propose UBR5 as an efficient ubiquitin chain elongator. This preference for ubiquitinated substrates and several distinct domains for protein-protein interactions may explain how UBR5 is linked to several different signalling pathways and cancers. Together, our data expand on the limited knowledge of the structure and function of HECT E3 ligases.
Topics: Humans; Ubiquitin-Protein Ligases; Cryoelectron Microscopy; Ubiquitination; Amino Acid Motifs; Ubiquitin
PubMed: 37409633
DOI: 10.15252/embj.2022113348 -
Cancers Dec 2023Bortezomib (BTZ) is widely implemented in the treatment of multiple myeloma (MM). Its main mechanism of action is very well established. BTZ selectively and reversibly... (Review)
Review
Bortezomib (BTZ) is widely implemented in the treatment of multiple myeloma (MM). Its main mechanism of action is very well established. BTZ selectively and reversibly inhibits the 26S proteasome. More precisely, it interacts with the chymotryptic site of the 20S proteasome and therefore inhibits the degradation of proteins. This results in the intracellular accumulation of misfolded or otherwise defective proteins leading to growth inhibition and apoptosis. As well as interfering with the ubiquitin-proteasome complex, BTZ elicits various epigenetic alterations which contribute to its cytotoxic effects as well as to the development of BTZ resistance. In this review, we summarized the epigenetic alterations elicited by BTZ. We focused on modifications contributing to the mechanism of action, those mediating drug-resistance development, and epigenetic changes promoting the occurrence of peripheral neuropathy. In addition, there are therapeutic strategies which are specifically designed to target epigenetic changes. Herein, we also reviewed epigenetic agents which might enhance BTZ-related cytotoxicity or restore the sensitivity to BTZ of resistant clones. Finally, we highlighted putative future perspectives regarding the role of targeting epigenetic changes in patients exposed to BTZ.
PubMed: 38201512
DOI: 10.3390/cancers16010084 -
Nature Communications Nov 2023Targeted proteasomal and autophagic protein degradation, often employing bifunctional modalities, is a new paradigm for modulation of protein function. In an attempt to...
Targeted proteasomal and autophagic protein degradation, often employing bifunctional modalities, is a new paradigm for modulation of protein function. In an attempt to explore protein degradation by means of autophagy we combine arylidene-indolinones reported to bind the autophagy-related LC3B-protein and ligands of the PDEδ lipoprotein chaperone, the BRD2/3/4-bromodomain containing proteins and the BTK- and BLK kinases. Unexpectedly, the resulting bifunctional degraders do not induce protein degradation by means of macroautophagy, but instead direct their targets to the ubiquitin-proteasome system. Target and mechanism identification reveal that the arylidene-indolinones covalently bind DCAF11, a substrate receptor in the CUL4A/B-RBX1-DDB1-DCAF11 E3 ligase. The tempered α, β-unsaturated indolinone electrophiles define a drug-like DCAF11-ligand class that enables exploration of this E3 ligase in chemical biology and medicinal chemistry programs. The arylidene-indolinone scaffold frequently occurs in natural products which raises the question whether E3 ligand classes can be found more widely among natural products and related compounds.
Topics: Oxindoles; Ligands; Cullin Proteins; Ubiquitin-Protein Ligases; Proteolysis; Proteasome Endopeptidase Complex; Biological Products; Ubiquitination
PubMed: 38036533
DOI: 10.1038/s41467-023-43657-6 -
PLoS Biology Sep 2023During aging, proteostasis capacity declines and distinct proteins become unstable and can accumulate as protein aggregates inside and outside of cells. Both in disease...
During aging, proteostasis capacity declines and distinct proteins become unstable and can accumulate as protein aggregates inside and outside of cells. Both in disease and during aging, proteins selectively aggregate in certain tissues and not others. Yet, tissue-specific regulation of cytoplasmic protein aggregation remains poorly understood. Surprisingly, we found that the inhibition of 3 core protein quality control systems, namely chaperones, the proteasome, and macroautophagy, leads to lower levels of age-dependent protein aggregation in Caenorhabditis elegans pharyngeal muscles, but higher levels in body-wall muscles. We describe a novel safety mechanism that selectively targets newly synthesized proteins to suppress their aggregation and associated proteotoxicity. The safety mechanism relies on macroautophagy-independent lysosomal degradation and involves several previously uncharacterized components of the intracellular pathogen response (IPR). We propose that this protective mechanism engages an anti-aggregation machinery targeting aggregating proteins for lysosomal degradation.
Topics: Animals; Caenorhabditis elegans; Protein Aggregates; Aging; Proteasome Endopeptidase Complex; Proteostasis
PubMed: 37708127
DOI: 10.1371/journal.pbio.3002284 -
ELife Oct 2023Recent work has revealed an increasingly important role for mRNA translation in maintaining proteostasis. Here, we use chemical inhibitors targeting discrete steps of...
Recent work has revealed an increasingly important role for mRNA translation in maintaining proteostasis. Here, we use chemical inhibitors targeting discrete steps of translation to compare how lowering the concentration of all or only translation initiation-dependent proteins rescues from proteotoxic stress. We systematically challenge proteostasis and show that pharmacologically inhibiting translation initiation or elongation elicits a distinct protective profile. Inhibiting elongation protects from heat and proteasome dysfunction independently from HSF-1 but does not protect from age-associated protein aggregation. Conversely, inhibition of initiation protects from heat and age-associated protein aggregation and increases lifespan, dependent on , but does not protect from proteotoxicity caused by proteasome dysfunction. Surprisingly, we find that the ability of the translation initiation machinery to control the concentration of newly synthesized proteins depends on HSF-1. Inhibition of translation initiation in wild-type animals reduces the concentration of newly synthesized proteins but increases it in mutants. Our findings suggest that the HSF-1 pathway is not only a downstream target of translation but also directly cooperates with the translation initiation machinery to control the concentration of newly synthesized proteins to restore proteostasis.
Topics: Animals; Caenorhabditis elegans Proteins; Transcription Factors; Proteostasis; Protein Aggregates; Proteasome Endopeptidase Complex; Caenorhabditis elegans; Heat Shock Transcription Factors
PubMed: 37795690
DOI: 10.7554/eLife.76465 -
Molecular Cell Apr 2024Most eukaryotic proteins are degraded by the 26S proteasome after modification with a polyubiquitin chain. Substrates lacking unstructured segments cannot be degraded...
Most eukaryotic proteins are degraded by the 26S proteasome after modification with a polyubiquitin chain. Substrates lacking unstructured segments cannot be degraded directly and require prior unfolding by the Cdc48 ATPase (p97 or VCP in mammals) in complex with its ubiquitin-binding partner Ufd1-Npl4 (UN). Here, we use purified yeast components to reconstitute Cdc48-dependent degradation of well-folded model substrates by the proteasome. We show that a minimal system consists of the 26S proteasome, the Cdc48-UN ATPase complex, the proteasome cofactor Rad23, and the Cdc48 cofactors Ubx5 and Shp1. Rad23 and Ubx5 stimulate polyubiquitin binding to the 26S proteasome and the Cdc48-UN complex, respectively, allowing these machines to compete for substrates before and after their unfolding. Shp1 stimulates protein unfolding by the Cdc48-UN complex rather than substrate recruitment. Experiments in yeast cells confirm that many proteins undergo bidirectional substrate shuttling between the 26S proteasome and Cdc48 ATPase before being degraded.
Topics: Adenosine Triphosphatases; Cell Cycle Proteins; Polyubiquitin; Proteasome Endopeptidase Complex; Proteolysis; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Ubiquitin; Valosin Containing Protein
PubMed: 38401542
DOI: 10.1016/j.molcel.2024.01.029 -
Autophagy Jul 2023Autophagosome isolation enables the thorough investigation of structural components and engulfed materials. Recently, we introduced a novel antibody-based FACS-mediated...
Autophagosome isolation enables the thorough investigation of structural components and engulfed materials. Recently, we introduced a novel antibody-based FACS-mediated method for isolation of native macroautophagic/autophagic vesicles and confirmed the quality of the preparations. We performed phospholipidomic and proteomic analyses to characterize autophagic vesicle-associated phospholipids and protein cargoes under different autophagy conditions. Lipidomic analyses identified phosphoglycerides and sphingomyelins within autophagic vesicles and revealed that the lipid composition was unaffected by different rates of autophagosome formation. Proteomic analyses identified more than 4500 potential autophagy substrates and showed that in comparison to autophagic vesicles isolated under basal autophagy conditions, starvation only marginally affected the cargo profile. Proteasome inhibition, however, resulted in the enhanced degradation of ubiquitin-proteasome system components. Taken together, the novel isolation method enriched large quantities of autophagic vesicles and enabled detailed analyses of their lipid and cargo composition.
Topics: Autophagy; Proteasome Endopeptidase Complex; Proteomics; Autophagosomes; Lipids
PubMed: 36416088
DOI: 10.1080/15548627.2022.2151188 -
International Journal of Molecular... Nov 2023Sarcomas are heterogeneous bone and soft tissue cancers representing the second most common tumor type in children and adolescents. Histology and genetic profiling... (Review)
Review
Sarcomas are heterogeneous bone and soft tissue cancers representing the second most common tumor type in children and adolescents. Histology and genetic profiling discovered more than 100 subtypes, which are characterized by peculiar molecular vulnerabilities. However, limited therapeutic options exist beyond standard therapy and clinical benefits from targeted therapies were observed only in a minority of patients with sarcomas. The rarity of these tumors, paucity of actionable mutations, and limitations in the chemical composition of current targeted therapies hindered the use of these approaches in sarcomas. Targeted protein degradation (TPD) is an innovative pharmacological modality to directly alter protein abundance with promising clinical potential in cancer, even for undruggable proteins. TPD is based on the use of small molecules called degraders or proteolysis-targeting chimeras (PROTACs), which trigger ubiquitin-dependent degradation of protein of interest. In this review, we will discuss major features of PROTAC and PROTAC-derived genetic systems for target validation and cancer treatment and focus on the potential of these approaches to overcome major issues connected to targeted therapies in sarcomas, including drug resistance, target specificity, and undruggable targets. A deeper understanding of these strategies might provide new fuel to drive molecular and personalized medicine to sarcomas.
Topics: Adolescent; Child; Humans; Proteolysis; Sarcoma; Soft Tissue Neoplasms; Precision Medicine; Genetic Profile; Neoplasms, Second Primary; Ubiquitin-Protein Ligases; Proteasome Endopeptidase Complex
PubMed: 38003535
DOI: 10.3390/ijms242216346