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Cancer Biology & Medicine Aug 2020Cancer immunotherapy harness the body's immune system to eliminate cancer, by using a broad panel of soluble and membrane proteins as therapeutic targets.... (Review)
Review
Cancer immunotherapy harness the body's immune system to eliminate cancer, by using a broad panel of soluble and membrane proteins as therapeutic targets. Immunosuppression signaling mediated by ligand-receptor interaction may be blocked by monoclonal antibodies, but because of repopulation of the membrane intracellular organelles, targets must be eliminated in whole cells. Targeted protein degradation, as exemplified in proteolysis targeting chimera (PROTAC) studies, is a promising strategy for selective inhibition of target proteins. The recently reported use of lysosomal targeting molecules to eliminate immune checkpoint proteins has paved the way for targeted degradation of membrane proteins as crucial anti-cancer targets. Further studies on these molecules' modes of action, target-binding "warheads", lysosomal sorting signals, and linker design should facilitate their rational design. Modifications and derivatives may improve their cell-penetrating ability and the stability of these pro-drugs. These studies suggest the promise of alternative strategies for cancer immunotherapy, with the aim of achieving more potent and durable suppression of tumor growth. Here, the successes and limitations of antibody inhibitors in cancer immunotherapy, as well as research progress on PROTAC- and lysosomal-dependent degradation of target proteins, are reviewed.
Topics: Animals; Antineoplastic Agents, Immunological; Drug Discovery; Humans; Ligands; Lysosomes; Molecular Targeted Therapy; Neoplasms; Proteasome Endopeptidase Complex; Proteolysis
PubMed: 32944392
DOI: 10.20892/j.issn.2095-3941.2020.0066 -
Autophagy 2018Many neurodegenerative disorders feature the presence of misfolded polypeptide-containing intracellular inclusion bodies biochemically and morphologically analogous to...
Many neurodegenerative disorders feature the presence of misfolded polypeptide-containing intracellular inclusion bodies biochemically and morphologically analogous to cellular aggresomes. However, it is largely unknown how misfolded polypeptides form aggresomes and are eventually cleared by the aggresome-macroautophagy/autophagy pathway, so-called aggrephagy. Our recent study revealed that when the ubiquitin-proteasome system is impaired, the accumulated misfolded polypeptides are selectively recognized and transported to the aggresome by a CED complex. This complex is composed of CTIF, originally identified as a specific factor for nuclear cap-binding protein complex (a heterodimer of NCBP1/CBP80 and NCBP2/CBP20)-dependent translation (CT), and its associated factors EEF1A1 and DCTN1. Aggresomal targeting of a misfolded polypeptide via the CED complex is accompanied by CTIF release from the CT complex and thereby inhibits CT efficiency. Therefore, our study provides new mechanistic insights into the crosstalk between translational inhibition and aggresome formation under the influence of a misfolded polypeptide.
Topics: Autophagy; Inclusion Bodies; Peptides; Proteasome Endopeptidase Complex; Protein Folding
PubMed: 28837386
DOI: 10.1080/15548627.2017.1358849 -
Current Opinion in Chemical Biology Dec 2014Specialized variants of the constitutive 20S proteasome in the immune system like the immunoproteasomes and the thymoproteasome contain active site-bearing subunits... (Review)
Review
Specialized variants of the constitutive 20S proteasome in the immune system like the immunoproteasomes and the thymoproteasome contain active site-bearing subunits which differ in their cleavage priorities and substrate binding pockets. The immunoproteasome plays a crucial role in antigen processing and for the differentiation of pro-inflammatory T helper cells which are involved in the pathogenesis of autoimmunity. Selective inhibitors of the immunoproteasome and constitutive proteasome have recently been generated which interfere with the development and progression of autoimmune diseases. Here we describe these inhibitors and their therapeutic potential as predicted from preclinical models.
Topics: Animals; Antigen Presentation; Humans; Immunologic Factors; Proteasome Endopeptidase Complex; Proteasome Inhibitors; Substrate Specificity
PubMed: 25217863
DOI: 10.1016/j.cbpa.2014.08.012 -
Methods in Molecular Biology (Clifton,... 2018Rapid, gentle isolation of 26S proteasomes from cells or tissues is an essential step for studies of the changes in proteasome activity and composition that can occur...
Rapid, gentle isolation of 26S proteasomes from cells or tissues is an essential step for studies of the changes in proteasome activity and composition that can occur under different physiological or pathological conditions and in response to pharmacological agents. We present here three different approaches to affinity purify or to prepare proteasome-rich cell fractions. The first method uses affinity tags fused to proteasome subunits and has been useful in several cell lines for studies of proteasome structure by cryo-electron microscopy and composition by mass spectrometry. A second method uses the proteasome's affinity for a ubiquitin-like (UBL) domain and can be used to purify these particles from any cell or tissue. This method does not require expression of a tagged subunit and has proven to be very useful to investigate how proteasomal activity changes in different physiological states (e.g., fasting or aging), with neurodegenerative diseases, and with drugs or hormones that cause subunit phosphorylation. A third, simple method that is based on the 26S proteasome's high molecular weight (about 2.5 MDa) concentrates these particles greatly by differential centrifugation. This method maintains the association of proteasomes with ubiquitin (Ub) conjugates and many other loosely associated regulatory proteins and is useful to study changes in proteasome composition under different conditions.
Topics: Animals; Centrifugation, Density Gradient; Chromatography, Affinity; Humans; Proteasome Endopeptidase Complex; Protein Binding; Protein Interaction Domains and Motifs; Ubiquitin
PubMed: 30242716
DOI: 10.1007/978-1-4939-8706-1_18 -
Communications Biology May 2022Effective organization of proteins into functional modules (networks, pathways) requires systems-level coordination between transcription, translation and degradation....
Effective organization of proteins into functional modules (networks, pathways) requires systems-level coordination between transcription, translation and degradation. Whereas the cooperation between transcription and translation was extensively studied, the cooperative degradation regulation of protein complexes and pathways has not been systematically assessed. Here we comprehensively analyzed degron masking, a major mechanism by which cellular systems coordinate degron recognition and protein degradation. For over 200 substrates with characterized degrons (E3 ligase targeting motifs, ubiquitination sites and disordered proteasomal entry sequences), we demonstrate that degrons extensively overlap with protein-protein interaction sites. Analysis of binding site information and protein abundance comparisons show that regulatory partners effectively outcompete E3 ligases, masking degrons from the ubiquitination machinery. Protein abundance variations between normal and cancer cells highlight the dynamics of degron masking components. Finally, integrative analysis of gene co-expression, half-life correlations and functional relationships between interacting proteins point towards higher-order, co-regulated degradation modules ('degronons') in the proteome.
Topics: Proteasome Endopeptidase Complex; Proteolysis; Proteome; Ubiquitin-Protein Ligases; Ubiquitination
PubMed: 35545699
DOI: 10.1038/s42003-022-03391-z -
Nature Communications Dec 2016Overexpression of NQO1 is associated with poor prognosis in human cancers including breast, colon, cervix, lung and pancreas. Yet, the molecular mechanisms underlying...
Overexpression of NQO1 is associated with poor prognosis in human cancers including breast, colon, cervix, lung and pancreas. Yet, the molecular mechanisms underlying the pro-tumorigenic capacities of NQO1 have not been fully elucidated. Here we show a previously undescribed function for NQO1 in stabilizing HIF-1α, a master transcription factor of oxygen homeostasis that has been implicated in the survival, proliferation and malignant progression of cancers. We demonstrate that NQO1 directly binds to the oxygen-dependent domain of HIF-1α and inhibits the proteasome-mediated degradation of HIF-1α by preventing PHDs from interacting with HIF-1α. NQO1 knockdown in human colorectal and breast cancer cell lines suppresses HIF-1 signalling and tumour growth. Consistent with this pro-tumorigenic function for NQO1, high NQO1 expression levels correlate with increased HIF-1α expression and poor colorectal cancer patient survival. These results collectively reveal a function of NQO1 in the oxygen-sensing mechanism that regulates HIF-1α stability in cancers.
Topics: Breast Neoplasms; Cell Line, Tumor; Colorectal Neoplasms; Gene Knockdown Techniques; Homeostasis; Humans; Hypoxia-Inducible Factor 1, alpha Subunit; NAD(P)H Dehydrogenase (Quinone); Oxygen; Proteasome Endopeptidase Complex; Protein Stability
PubMed: 27966538
DOI: 10.1038/ncomms13593 -
Future Medicinal Chemistry Jan 2021Regulating protein production and degradation is critical to maintaining cellular homeostasis. The proteasome is a key player in keeping proteins at the proper levels.... (Review)
Review
Regulating protein production and degradation is critical to maintaining cellular homeostasis. The proteasome is a key player in keeping proteins at the proper levels. However, proteasome activity can be altered in certain disease states, such as blood cancers and neurodegenerative diseases. Cancers often exhibit enhanced proteasomal activity, as protein synthesis is increased in these cells compared with normal cells. Conversely, neurodegenerative diseases are characterized by protein accumulation, leading to reduced proteasome activity. As a result, the proteasome has emerged as a target for therapeutic intervention. The potential of the proteasome as a therapeutic target has come from studies involving chemical stimulators and inhibitors, and the development of a suite of assays and probes that can be used to monitor proteasome activity with purified enzyme and in live cells.
Topics: Biomarkers; Catalytic Domain; Gene Expression Regulation; High-Throughput Screening Assays; Humans; Models, Molecular; Neoplasms; Neurodegenerative Diseases; Proteasome Endopeptidase Complex; Proteasome Inhibitors; Protein Binding; Protein Conformation; Proteolysis; Proteostasis
PubMed: 33275045
DOI: 10.4155/fmc-2020-0288 -
Molecules (Basel, Switzerland) Jun 2017Amyloid proteins are closely related with amyloid diseases and do tremendous harm to human health. However, there is still a lack of effective strategies to treat these... (Review)
Review
Amyloid proteins are closely related with amyloid diseases and do tremendous harm to human health. However, there is still a lack of effective strategies to treat these amyloid diseases, so it is important to develop novel methods. Accelerating the clearance of amyloid proteins is a favorable method for amyloid disease treatment. Recently, chemical methods for protein reduction have been developed and have attracted much attention. In this review, we focus on the latest progress of chemical methods that knock down amyloid proteins, including the proteolysis-targeting chimera (PROTAC) strategy, the "recognition-cleavage" strategy, the chaperone-mediated autophagy (CMA) strategy, the selectively light-activatable organic and inorganic molecules strategy and other chemical strategies.
Topics: Amyloidogenic Proteins; Autophagy; Molecular Chaperones; Proteasome Endopeptidase Complex; Protein Binding; Proteolysis; Structure-Activity Relationship; Ubiquitins
PubMed: 28587164
DOI: 10.3390/molecules22060916 -
Journal of Medicinal Chemistry Nov 2020The immunoproteasome (i-20S) has emerged as a therapeutic target for autoimmune and inflammatory disorders and hematological malignancies. Inhibition of the chymotryptic...
The immunoproteasome (i-20S) has emerged as a therapeutic target for autoimmune and inflammatory disorders and hematological malignancies. Inhibition of the chymotryptic β5i subunit of i-20S inhibits T cell activation, B cell proliferation, and dendritic cell differentiation in vitro and suppresses immune responses in animal models of autoimmune disorders and allograft rejection. However, cytotoxicity to immune cells has accompanied the use of covalently reactive β5i inhibitors, whose activity against the constitutive proteasome (c-20S) is cumulative with the time of exposure. Herein, we report a structure-activity relationship study of a class of noncovalent proteasome inhibitors with picomolar potencies and 1000-fold selectivity for i-20S over c-20S. Furthermore, these inhibitors are specific for β5i over the other five active subunits of i-20S and c-20S, providing useful tools to study the functions of β5i in immune responses. The potency of these compounds in inhibiting human T cell activation suggests that they may have therapeutic potential.
Topics: Binding Sites; Cell Proliferation; Dipeptides; HeLa Cells; Humans; Inhibitory Concentration 50; Kinetics; Lymphocyte Activation; Proteasome Endopeptidase Complex; Proteasome Inhibitors; Protein Binding; Protein Subunits; Structure-Activity Relationship; T-Lymphocytes
PubMed: 33095579
DOI: 10.1021/acs.jmedchem.0c01520 -
Viruses Mar 2021The rapid and dynamic activation of the innate immune system is achieved through complex signaling networks regulated by post-translational modifications modulating the... (Review)
Review
The rapid and dynamic activation of the innate immune system is achieved through complex signaling networks regulated by post-translational modifications modulating the subcellular localization, activity, and abundance of signaling molecules. Many constitutively expressed signaling molecules are present in the cell in inactive forms, and become functionally activated once they are modified with ubiquitin, and, in turn, inactivated by removal of the same post-translational mark. Moreover, upon infection resolution a rapid remodeling of the proteome needs to occur, ensuring the removal of induced response proteins to prevent hyperactivation. This review discusses the current knowledge on the negative regulation of innate immune signaling pathways by deubiquitinating enzymes, and through degradative ubiquitination. It focusses on spatiotemporal regulation of deubiquitinase and E3 ligase activities, mechanisms for re-establishing proteostasis, and degradation through immune-specific feedback mechanisms vs. general protein quality control pathways.
Topics: Gene Expression Regulation; Humans; Immunity, Innate; Proteasome Endopeptidase Complex; Protein Binding; Protein Processing, Post-Translational; Protein Transport; Signal Transduction; Ubiquitination
PubMed: 33808506
DOI: 10.3390/v13040584