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Acta Pharmacologica Sinica Jan 2021Tumor cells form immune escape and subsequently obtain unlimited proliferation ability due to the abnormal immune surveillance mediated by immune checkpoints. Among this... (Review)
Review
Tumor cells form immune escape and subsequently obtain unlimited proliferation ability due to the abnormal immune surveillance mediated by immune checkpoints. Among this class of immune checkpoints, PD-1/PD-L1 was recognized as an anticancer drug target for many years, and so far, several monoclonal antibodies have achieved encouraging outcome in cancer treatment by targeting the PD-1/PD-L1 signaling pathway. Due to the inherent limitations of antibodies, the development of small molecule inhibitors based on PD-1/PD-L1 signaling pathway is gradually reviving in decades. In this review, we summarized a number of small molecule inhibitors based on three different therapeutic approaches interfering PD-1/PD-L1 signaling pathway: (1) blocking direct interaction between PD-1 and PD-L1; (2) inhibiting transcription and translation of PD-L1; and (3) promoting degradation of PD-L1 protein. The development of these small molecule inhibitors opens a new avenue for tumor immunotherapy based on PD-1/PD-L1 signaling pathway.
Topics: Amino Acid Sequence; Animals; Antineoplastic Agents; B7-H1 Antigen; Humans; Immune Checkpoint Inhibitors; Neoplasms; Programmed Cell Death 1 Receptor; Proteolysis; Signal Transduction
PubMed: 32152439
DOI: 10.1038/s41401-020-0366-x -
Molecular Cell Dec 2019Protein silencing represents an essential tool in biomedical research. Targeted protein degradation (TPD) strategies exemplified by PROTACs are rapidly emerging as...
Protein silencing represents an essential tool in biomedical research. Targeted protein degradation (TPD) strategies exemplified by PROTACs are rapidly emerging as modalities in drug discovery. However, the scope of current TPD techniques is limited because many intracellular materials are not substrates of proteasomal clearance. Here, we described a novel targeted-clearance strategy (autophagy-targeting chimera [AUTAC]) that contains a degradation tag (guanine derivatives) and a warhead to provide target specificity. As expected from the substrate scope of autophagy, AUTAC degraded fragmented mitochondria as well as proteins. Mitochondria-targeted AUTAC accelerated both the removal of dysfunctional fragmented mitochondria and the biogenesis of functionally normal mitochondria in patient-derived fibroblast cells. Cytoprotective effects against acute mitochondrial injuries were also seen. Canonical autophagy is viewed as a nonselective bulk decomposition system, and none of the available autophagy-inducing agents exhibit useful cargo selectivity. With its target specificity, AUTAC provides a new modality for research on autophagy-based drugs.
Topics: Autophagy; Autophagy-Related Proteins; Cell Line; Guanine; Humans; Mitochondria; Mitophagy; Protein Engineering; Protein Kinases; Protein Stability; Proteolysis
PubMed: 31606272
DOI: 10.1016/j.molcel.2019.09.009 -
Cell Chemical Biology Jul 2021Induced protein degradation accomplishes elimination, rather than inhibition, of pathological proteins. Key to the success of this novel therapeutic modality is the... (Review)
Review
Induced protein degradation accomplishes elimination, rather than inhibition, of pathological proteins. Key to the success of this novel therapeutic modality is the modification of proteins with ubiquitin chains, which is brought about by molecular glues or bivalent compounds that induce proximity between the target protein and an E3 ligase. The human genome encodes ∼600 E3 ligases that differ widely in their structures, catalytic mechanisms, modes of regulation, and physiological roles. While many of these enzymes hold great promise for drug discovery, few have been successfully engaged by small-molecule degraders. Here, we review E3 ligases that are being used for induced protein degradation. Based on these prior successes and our growing understanding of the biology and biochemistry of E3 ligases, we propose new ubiquitylation enzymes that can be harnessed for drug discovery to firmly establish induced protein degradation as a specific and efficient therapeutic approach.
Topics: Enzyme Inhibitors; Humans; Proteolysis; Small Molecule Libraries; Ubiquitin-Protein Ligases
PubMed: 33891901
DOI: 10.1016/j.chembiol.2021.04.002 -
Chemical Society Reviews Jul 2022Proteolysis Targeting Chimeras (PROTACs), an emerging therapeutic entity designed to degrade target proteins by hijacking the ubiquitin-proteasome system, have the... (Review)
Review
Proteolysis Targeting Chimeras (PROTACs), an emerging therapeutic entity designed to degrade target proteins by hijacking the ubiquitin-proteasome system, have the potential to revolutionize the healthcare industry. The broad applicability of this protein degradation strategy has been verified with a few E3 ligases and a variety of distinct targets through the construction of modular chimeric structures. Despite recent efforts to promote the use of PROTACs for clinical applications, most PROTACs do not make it beyond the preclinical stage of drug development. There are several reasons that prevent PROTACs from reaching the market, and the inadequate delivery to the target site is one of the most challenging hurdles. With the increasing need for accelerating the translational process, combining the concepts of PROTACs and delivery systems has been explored to enhance the performance of PROTACs. These improved delivery strategies can eliminate unfavorable physicochemical properties of PROTACs, improve their targetability, and decrease their off-target side effects. The integration of powerful PROTACs and versatile delivery systems will inaugurate a burgeoning orientation for the field of targeted protein degradation. In this review, we will survey the latest progress in improving the degradation efficacy of PROTACs through delivery strategies, outline design principles for PROTAC-based delivery systems, discuss the current challenges with PROTACs, and outlook future opportunities in this field.
Topics: Drug Discovery; Proteolysis; Ubiquitin-Protein Ligases
PubMed: 35713468
DOI: 10.1039/d1cs00762a -
Nature Chemical Biology Mar 2023Targeted protein degradation is a novel pharmacology established by drugs that recruit target proteins to E3 ubiquitin ligases. Based on the structure of the degrader...
Targeted protein degradation is a novel pharmacology established by drugs that recruit target proteins to E3 ubiquitin ligases. Based on the structure of the degrader and the target, different E3 interfaces are critically involved, thus forming defined 'functional hotspots'. Understanding disruptive mutations in functional hotspots informs on the architecture of the assembly, and highlights residues susceptible to acquire resistance phenotypes. Here we employ haploid genetics to show that hotspot mutations cluster in substrate receptors of hijacked ligases, where mutation type and frequency correlate with gene essentiality. Intersection with deep mutational scanning revealed hotspots that are conserved or specific for chemically distinct degraders and targets. Biophysical and structural validation suggests that hotspot mutations frequently converge on altered ternary complex assembly. Moreover, we validated hotspots mutated in patients that relapse from degrader treatment. In sum, we present a fast and widely accessible methodology to characterize small-molecule degraders and associated resistance mechanisms.
Topics: Ubiquitin-Protein Ligases; Proteolysis; Carrier Proteins
PubMed: 36329119
DOI: 10.1038/s41589-022-01177-2 -
Science Advances Jan 2023Despite the rapid utilization of immunotherapy, emerging challenges to the current immune checkpoint blockade need to be resolved. Here, we report that elevation of CD73...
Despite the rapid utilization of immunotherapy, emerging challenges to the current immune checkpoint blockade need to be resolved. Here, we report that elevation of CD73 levels due to its aberrant turnover is correlated with poor prognosis in immune-cold triple-negative breast cancers (TNBCs). We have identified TRIM21 as an E3 ligase that governs CD73 destruction. Disruption of TRIM21 stabilizes CD73 that in turn enhances CD73-catalyzed production of adenosine, resulting in the suppression of CD8 T cell function. Replacement of lysine 133, 208, 262, and 321 residues by arginine on CD73 attenuated CD73 ubiquitylation and degradation. Diminishing of CD73 ubiquitylation remarkably promotes tumor growth and impedes antitumor immunity. In addition, a TRIM21/CD73 signature in a subgroup of human breast malignancies was associated with a favorable immune profile. Collectively, our findings uncover a mechanism that governs CD73 proteolysis and point to a new therapeutic strategy by modulating CD73 ubiquitylation.
Topics: Humans; Immunotherapy; Triple Negative Breast Neoplasms; CD8-Positive T-Lymphocytes; Proteolysis; Ubiquitin-Protein Ligases
PubMed: 36608132
DOI: 10.1126/sciadv.add6626 -
Cell Chemical Biology Oct 2022Proteolysis-targeting chimeras (PROTACs) bring a protein of interest (POI) into spatial proximity of an E3 ubiquitin ligase, promoting POI ubiquitylation and proteasomal...
Proteolysis-targeting chimeras (PROTACs) bring a protein of interest (POI) into spatial proximity of an E3 ubiquitin ligase, promoting POI ubiquitylation and proteasomal degradation. PROTACs rely on endogenous cellular machinery to mediate POI degradation, therefore the subcellular location of the POI and access to the E3 ligase being recruited potentially impacts PROTAC efficacy. To interrogate whether the subcellular context of the POI influences PROTAC-mediated degradation, we expressed either Halo or FKBP12 (dTAG) constructs consisting of varying localization signals and tested the efficacy of their degradation by von Hippel-Lindau (VHL)- or cereblon (CRBN)-recruiting PROTACs targeting either Halo or dTAG. POIs were localized to the nucleus, cytoplasm, outer mitochondrial membrane, endoplasmic reticulum, Golgi, peroxisome or lysosome. Differentially localized Halo or FKBP12 proteins displayed varying levels of degradation using the same respective PROTACs, suggesting therefore that the subcellular context of the POI can influence the efficacy of PROTAC-mediated POI degradation.
Topics: Proteolysis; Tacrolimus Binding Protein 1A; Ubiquitin-Protein Ligases
PubMed: 36075213
DOI: 10.1016/j.chembiol.2022.08.004 -
Angewandte Chemie (International Ed. in... Dec 2021Targeting cereblon (CRBN) is currently one of the most frequently reported proteolysis-targeting chimera (PROTAC) approaches, owing to favorable drug-like properties of...
Targeting cereblon (CRBN) is currently one of the most frequently reported proteolysis-targeting chimera (PROTAC) approaches, owing to favorable drug-like properties of CRBN ligands, immunomodulatory imide drugs (IMiDs). However, IMiDs are known to be inherently unstable, readily undergoing hydrolysis in body fluids. Here we show that IMiDs and IMiD-based PROTACs rapidly hydrolyze in commonly utilized cell media, which significantly affects their cell efficacy. We designed novel CRBN binders, phenyl glutarimide (PG) analogues, and showed that they retained affinity for CRBN with high ligand efficiency (LE >0.48) and displayed improved chemical stability. Our efforts led to the discovery of PG PROTAC 4 c (SJ995973), a uniquely potent degrader of bromodomain and extra-terminal (BET) proteins that inhibited the viability of human acute myeloid leukemia MV4-11 cells at low picomolar concentrations (IC =3 pM; BRD4 DC =0.87 nM). These findings strongly support the utility of PG derivatives in the design of CRBN-directed PROTACs.
Topics: Adaptor Proteins, Signal Transducing; Humans; Hydrolysis; Piperidones; Proteolysis; Ubiquitin-Protein Ligases
PubMed: 34614283
DOI: 10.1002/anie.202108848 -
Nature Chemical Biology Nov 2021Bivalent proteolysis-targeting chimeras (PROTACs) drive protein degradation by simultaneously binding a target protein and an E3 ligase and forming a productive ternary...
Bivalent proteolysis-targeting chimeras (PROTACs) drive protein degradation by simultaneously binding a target protein and an E3 ligase and forming a productive ternary complex. We hypothesized that increasing binding valency within a PROTAC could enhance degradation. Here, we designed trivalent PROTACs consisting of a bivalent bromo and extra terminal (BET) inhibitor and an E3 ligand tethered via a branched linker. We identified von Hippel-Lindau (VHL)-based SIM1 as a low picomolar BET degrader with preference for bromodomain containing 2 (BRD2). Compared to bivalent PROTACs, SIM1 showed more sustained and higher degradation efficacy, which led to more potent anticancer activity. Mechanistically, SIM1 simultaneously engages with high avidity both BET bromodomains in a cis intramolecular fashion and forms a 1:1:1 ternary complex with VHL, exhibiting positive cooperativity and high cellular stability with prolonged residence time. Collectively, our data along with favorable in vivo pharmacokinetics demonstrate that augmenting the binding valency of proximity-induced modalities can be an enabling strategy for advancing functional outcomes.
Topics: Humans; Proteolysis; Ubiquitin-Protein Ligases
PubMed: 34675414
DOI: 10.1038/s41589-021-00878-4 -
Trends in Pharmacological Sciences Nov 2023Targeted protein degradation (TPD) is an emerging modality for research and therapeutics. Most TPD approaches harness cellular ubiquitin-dependent proteolytic pathways.... (Review)
Review
Targeted protein degradation (TPD) is an emerging modality for research and therapeutics. Most TPD approaches harness cellular ubiquitin-dependent proteolytic pathways. Proteolysis-targeting chimeras (PROTACs) and molecular glue (MG) degraders (MGDs) represent the most advanced TPD approaches, with some already used in clinical settings. Despite these advances, TPD still faces many challenges, pertaining to both the development of effective, selective, and tissue-penetrant degraders and understanding their mode of action. In this review, we focus on progress made in addressing these challenges. In particular, we discuss the utility and application of recent proteomic approaches as indispensable tools to enable insights into degrader development, including target engagement, degradation selectivity, efficacy, safety, and mode of action.
Topics: Humans; Proteolysis; Proteomics; Proteolysis Targeting Chimera; Ubiquitin-Protein Ligases
PubMed: 37778939
DOI: 10.1016/j.tips.2023.08.007