Explore the vast range of titles available.

The orexin system regulates sleep and arousal in humans, with orexin receptor antagonists becoming promising therapeutics for insomnia; now, the X-ray crystal structure of the human OX 2 receptor in the presence of the insomnia drug suvorexant is solved. Antagonst-bound orexin receptor structures The orexin(hypocretin) system regulates sleep and arousal in humans, and orexin receptor antagonists are seen as promising therapeutics for insomnia. Here the authors solve the X-ray crystal structure of the human OX 2 orexin receptor in the presence of the suvorexant, a dual-orexin receptor antagonist anti-insomnia drug. The structure provides a molecular framework for understanding dual-orexin receptor antagonist binding. The authors use two different docking programs to predict how three other antagonists with different core structures may bind to this G-protein-coupled receptor. The orexin (also known as hypocretin) G protein-coupled receptors (GPCRs) respond to orexin neuropeptides in the central nervous system to regulate sleep and other behavioural functions in humans 1 . Defects in orexin signalling are responsible for the human diseases of narcolepsy and cataplexy; inhibition of orexin receptors is an effective therapy for insomnia 2 . The human OX 2 receptor (OX 2 R) belongs to the β branch of the rhodopsin family of GPCRs 3 , and can bind to diverse compounds including the native agonist peptides orexin-A and orexin-B and the potent therapeutic inhibitor suvorexant 4 . Here, using lipid-mediated crystallization and protein engineering with a novel fusion chimaera, we solved the structure of the human OX 2 R bound to suvorexant at 2.5 Å resolution. The structure reveals how suvorexant adopts a π-stacked horseshoe-like conformation and binds to the receptor deep in the orthosteric pocket, stabilizing a network of extracellular salt bridges and blocking transmembrane helix motions necessary for activation. Computational docking suggests how other classes of synthetic antagonists may interact with the receptor at a similar position in an analogous π-stacked fashion. Elucidation of the molecular architecture of the human OX 2 R expands our understanding of peptidergic GPCR ligand recognition and will aid further efforts to modulate orexin signalling for therapeutic ends.

Alkenyl oxindoles have been characterized as autophagosome-tethering compounds (ATTECs), which can target mutant huntingtin protein (mHTT) for lysosomal degradation. In order to expand the application of alkenyl oxindoles for targeted protein degradation, we designed and synthesized a series of heterobifunctional compounds by conjugating different alkenyl oxindoles with bromodomain-containing protein 4 (BRD4) inhibitor JQ1. Through structure-activity relationship study, we successfully developed JQ1-alkenyl oxindole conjugates that potently degrade BRD4. Unexpectedly, we found that these molecules degrade BRD4 through the ubiquitin-proteasome system, rather than the autophagy-lysosomal pathway. Using pooled CRISPR interference (CRISPRi) screening, we revealed that JQ1-alkenyl oxindole conjugates recruit the E3 ubiquitin ligase complex CRL4 DCAF11 for substrate degradation. Furthermore, we validated the most potent heterobifunctional molecule HL435 as a promising drug-like lead compound to exert antitumor activity both in vitro and in a mouse xenograft tumor model. Our research provides new employable proteolysis targeting chimera (PROTAC) moieties for targeted protein degradation, providing new possibilities for drug discovery.

Narcolepsy type 1 (NT1) is a chronic neurological disorder that impairs the brain’s ability to control sleep-wake cycles. Current therapies are limited to the management of symptoms with modest effectiveness and substantial adverse effects. Agonists of the orexin receptor 2 (OX 2 R) have shown promise as novel therapeutics that directly target the pathophysiology of the disease. However, identification of drug-like OX 2 R agonists has proven difficult. Here we report cryo-electron microscopy structures of active-state OX 2 R bound to an endogenous peptide agonist and a small-molecule agonist. The extended carboxy-terminal segment of the peptide reaches into the core of OX 2 R to stabilize an active conformation, while the small-molecule agonist binds deep inside the orthosteric pocket, making similar key interactions. Comparison with antagonist-bound OX 2 R suggests a molecular mechanism that rationalizes both receptor activation and inhibition. Our results enable structure-based discovery of therapeutic orexin agonists for the treatment of NT1 and other hypersomnia disorders. Agonists of the orexin receptor 2 (OX 2 R) show promise in the treatment of narcolepsy. Cryo-EM structures of active-state OX 2 R bound to an endogenous peptide agonist and a small-molecule agonist suggest a molecular mechanism that rationalizes both receptor activation and inhibition.

PROTAC® (proteolysis-targeting chimera) molecules induce proximity between an E3 ligase and protein-of-interest (POI) to target the POI for ubiquitin-mediated degradation. Cooperative E3-PROTAC-POI complexes have potential to achieve neo-substrate selectivity beyond that established by POI binding to the ligand alone. Here, we extend the collection of ubiquitin ligases employable for cooperative ternary complex formation to include the C-degron E3 KLHDC2. Ligands were identified that engage the C-degron binding site in KLHDC2, subjected to structure-based improvement, and linked to JQ1 for BET-family neo-substrate recruitment. Consideration of the exit vector emanating from the ligand engaged in KLHDC2’s U-shaped degron-binding pocket enabled generation of SJ46421, which drives formation of a remarkably cooperative, paralog-selective ternary complex with BRD3 BD2 . Meanwhile, screening pro-drug variants enabled surmounting cell permeability limitations imposed by acidic moieties resembling the KLHDC2-binding C-degron. Selectivity for BRD3 compared to other BET-family members is further manifested in ubiquitylation in vitro, and prodrug version SJ46420-mediated degradation in cells. Selectivity is also achieved for the ubiquitin ligase, overcoming E3 auto-inhibition to engage KLHDC2, but not the related KLHDC1, KLHDC3, or KLHDC10 E3s. In sum, our study establishes neo-substrate-specific targeted protein degradation via KLHDC2, and provides a framework for developing selective PROTAC protein degraders employing C-degron E3 ligases. KLHDC2 is a promising E3 ligase for targeted protein degradation (TPD). In this study, the authors demonstrate that heterobifunctional degraders induce cooperative ternary complexes with KLHDC2 and BRD3. They highlight exit vector, neo-substrate, E3 ligase selectivity, and prodrug choice can effectively leverage C-degron E3s for TPD.

Inhibition of deubiquitinase (DUB) activity is a promising strategy for cancer therapy. VLX1570 is an inhibitor of proteasome DUB activity currently in clinical trials for relapsed multiple myeloma. Here we show that VLX1570 binds to and inhibits the activity of ubiquitin-specific protease-14 (USP14) in vitro, with comparatively weaker inhibitory activity towards UCHL5 (ubiquitin-C-terminal hydrolase-5). Exposure of multiple myeloma cells to VLX1570 resulted in thermostabilization of USP14 at therapeutically relevant concentrations. Transient knockdown of USP14 or UCHL5 expression by electroporation of siRNA reduced the viability of multiple myeloma cells. Treatment of multiple myeloma cells with VLX1570 induced the accumulation of proteasome-bound high molecular weight polyubiquitin conjugates and an apoptotic response. Sensitivity to VLX1570 was moderately affected by altered drug uptake, but was unaffected by overexpression of BCL2-family proteins or inhibitors of caspase activity. Finally, treatment with VLX1570 was found to lead to extended survival in xenograft models of multiple myeloma. Our findings demonstrate promising antiproliferative activity of VLX1570 in multiple myeloma, primarily associated with inhibition of USP14 activity.

Securinega alkaloids possess a distinctive tetracyclic scaffold and are pharmaceutically relevant, yet their biosynthesis in Flueggea suffruticosa remains unresolved. Here, we combine chemical logic with stable-isotope-labeled feeding experiments and single-cell transcriptomics to elucidate the core biosynthetic pathway. We identify a reductase, FsMS , that reduces premenisdaurilide to menisdaurilide, which then conjugates with 1-piperideine to generate the [2.2.2]-bicyclic neosecurinanes, (–)-virosine A and (–)-virosine B. We also identify two sulfotransferases, FsNSST1 and FsNSST2 , that O -sulfate these neosecurinanes; the resulting sulfate esters undergo a spontaneous 1,2-amine shift to yield the [3.2.1]-bicyclic securinanes, allosecurinine and securinine. This transformation reveals an unexpected biosynthetic role of sulfotransferases, not as conventional tailoring enzymes, but as key mediators of scaffold remodeling. The newly identified biosynthetic genes are co-expressed within a specific vasculature-associated cell type, enabling prioritization of additional pathway candidates. These findings highlight the power of chemically guided single-cell transcriptomics in unraveling complex biosynthetic pathways. Securinega alkaloids, comprising a distinctive tetracyclic scaffold, have long been studied, but their biosynthesis has remained largely unknown. Here, the authors employ chemical insights with single-cell transcriptomics to reveal key biosynthetic steps of securinega alkaloids in Flueggea suffruticosa .

Cop9 signalosome (CSN) regulates the function of cullin—RING E3 ubiquitin ligases (CRLs) by deconjugating the ubiquitin-like protein NEDD8 from the cullin subunit. To understand the physiological impact of CSN function on the CRL network and cell proliferation, we combined quantitative mass spectrometry and genome-wide CRISPR interference (CRISPRi) and CRISPR activation (CRISPRa) screens to identify factors that modulate cell viability upon inhibition of CSN by the small molecule CSN5i-3. CRL components and regulators strongly modulated the antiproliferative effects of CSN5i-3, and in addition we found two pathways involved in genome integrity, SCFFBXO5—APC/C—GMNN and CUL4DTL—SETD8, that contribute substantially to the toxicity of CSN inhibition. Our data highlight the importance of CSN-mediated NEDD8 deconjugation and adaptive exchange of CRL substrate receptors in sustaining CRL function and suggest approaches for leveraging CSN inhibition for the treatment of cancer.

Neuroblastoma is a severe childhood disease, accounting for ~10% of all infant cancers. The amplification of the MYCN gene, coding for the N-Myc transcription factor, is an essential marker correlated with tumor progression and poor prognosis. In neuroblastoma cells, the mitotic kinase Aurora-A (AURKA), also frequently overexpressed in cancer, prevents N-Myc degradation by directly binding to a highly conserved N-Myc region. As a result, elevated levels of N-Myc are observed. During recent years, it has been demonstrated that some ATP competitive inhibitors of AURKA also cause essential conformational changes in the structure of the activation loop of the kinase that prevents N-Myc binding, thus impairing the formation of the AURKA/N-Myc complex. In this study, starting from a screening of crystal structures of AURKA in complexes with known inhibitors, we identified additional compounds affecting the conformation of the kinase activation loop. We assessed the ability of such compounds to disrupt the interaction between AURKA and N-Myc in vitro, using Surface Plasmon Resonance competition assays, and in tumor cell lines overexpressing MYCN, by performing Proximity Ligation Assays. Finally, their effects on N-Myc cellular levels and cell viability were investigated. Our results identify PHA-680626 as an amphosteric inhibitor both in vitro and in MYCN overexpressing cell lines, thus expanding the repertoire of known conformational disrupting inhibitors of the AURKA/N-Myc complex and confirming that altering the conformation of the activation loop of AURKA with a small molecule is an effective strategy to destabilize the AURKA/N-Myc interaction in neuroblastoma cancer cells.

PurposeLaurocapram (Azone) was broadly examined as a representative enhancer of skin penetration in the 1980s. However, it was not approved for treatment because it caused skin irritation following its penetration into the epidermis through the stratum corneum. In the present study, a so-called ante-enhancer with an Azone-mimic structure was designed based on an ante-drug with negligible systemic toxic effects following its permeation through the skin.MethodsThe ante-enhancer was designed using ionic liquid technology: an ionic liquid-type ante-enhancer (IL-Azone) with an Azone-mimic structure was prepared from ε-caprolactam and myristic acid as cationic and anionic substances, respectively. The enhancing effects of IL-Azone on the permeation by the following model drugs through pig skin were examined: isosorbide 5-mononitrate (ISMN), antipyrine (ANP), and fluorescein isothiocyanate dextran (FD-4). Skin irritation by IL-Azone was assessed using the Draize method.ResultsThe primary irritation index (P.I.I.) of IL-Azone by the Draize method was markedly lower than that of Azone (6.9). Although the ability of IL-Azone to enhance skin penetration was not as high as Azone, IL-Azone moderately increased skin permeation by the model compounds tested (ISMN: 4.7 fold, ANP: 4.5 fold, FD-4: 4.0 fold).ConclusionsThese results suggest the usefulness of designing a skin penetration enhancer using ionic liquid technology. Further trials on the ionic liquid design with an Azone-mimic structure using other cations and anions may lead to the development of better ante-enhancers.

Chemical manipulations performed on the histone H3 lysine 9 methyltransferases (G9a/GLP) inhibitor BIX-01294 afforded novel desmethoxyquinazolines able to inhibit the DNA methyltransferase DNMT3A at low micromolar levels without any significant inhibition of DNMT1 and G9a. In KG-1 cells such compounds, when tested at sub-toxic doses, induced the luciferase re-expression in a stable construct controlled by a cytomegalovirus (CMV) promoter silenced by methylation (CMV-luc assay). Finally, in human lymphoma U-937 and RAJI cells, the N-(1-benzylpiperidin-4-yl)-2-(4-phenylpiperazin-1-yl)quinazolin-4-amine induced the highest proliferation arrest and cell death induction starting from 10 µM, in agreement with its DNMT3A inhibitory potency.