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Leaf color is a key ornamental characteristic of cultivated caladium (Caladium × hortulanum Birdsey), a plant with diverse leaf colors. However, the genetic improvement of leaf color in cultivated caladium is hindered by the limited understanding of leaf color diversity and regulation. In this study, the chlorophyll and anthocyanin content of 137 germplasm resources were measured to explore the diversity and mechanism of leaf color formation in cultivated caladium. Association analysis of EST-SSR markers and pigment traits was performed, as well as metabolomics and transcriptomics analysis of a red leaf variety and its white leaf mutant. We found significant differences in chlorophyll and anthocyanin content among different color groups of cultivated caladium, and identified three, eight, three, and seven EST-SSR loci significantly associated with chlorophyll-a, chlorophyll-b, total chlorophyll and total anthocyanins content, respectively. The results further revealed that the white leaf mutation was caused by the down-regulation of various anthocyanins (such as cyanidin-3-O-rutinoside, quercetin-3-O-glucoside, and others). This change in concentration is likely due to the down-regulation of key genes (four PAL, four CHS, six CHI, eight F3H, one F3′H, one FLS, one LAR, four DFR, one ANS and two UFGT) involved in anthocyanin biosynthesis. Concurrently, the up-regulation of certain genes (one FLS and one LAR) that divert the anthocyanin precursors to other pathways was noted. Additionally, a significant change in the expression of numerous transcription factors (12 NAC, 12 bZIP, 23 ERF, 23 bHLH, 19 MYB_related, etc.) was observed. These results revealed the genetic and metabolic basis of leaf color diversity and change in cultivated caladium, and provided valuable information for molecular marker-assisted selection and breeding of leaf color in this ornamental plant. [ABSTRACT FROM AUTHOR]

β-Secretase (β-site amyloid precursor protein-cleaving enzyme 1; BACE1) is a transmembrane aspartic protease that cleaves the β-amyloid precursor protein en route to generation of the amyloid β-peptide (Aβ) that is believed to be responsible for the Alzheimer's disease amyloid cascade. It is thus a prime target for the development of inhibitors which may serve as drugs in the treatment and/or prevention of Alzheimer's disease. In the following determination of the crystal structures of both apo and complexed BACE1, structural analysis of all crystal structures of BACE1 deposited in the PDB and molecular dynamics (MD) simulations of monomeric and `dimeric' BACE1 were used to study conformational changes in the active-site region of the enzyme. It was observed that a flap able to cover the active site is the most flexible region, adopting multiple conformational states in the various crystal structures. Both the presence or absence of an inhibitor within the active site and the crystal packing are shown to influence the flap's conformation. An open conformation of the flap is mostly observed in the apo structures, while direct hydrogen-bonding interaction between main-chain atoms of the flap and the inhibitor is a prerequisite for the flap to adopt a closed conformation in the crystal structures of complexes. Thus, a systematic study of the conformational flexibility of the enzyme may not only contribute to structure-based drug design of BACE1 inhibitors and of other targets with flexible conformations, but may also help to better understand the mechanistic events associated with the binding of substrates and inhibitors to the enzyme. [ABSTRACT FROM AUTHOR]

A combination of fluorescence spectroscopy and molecular dynamics (MD) is applied to assess the conformational dynamics of a peptide making up the outermost ring of the nicotinic acetylcholine receptor (AChR) transmembrane region and the effect of membrane thickness and cholesterol on the hydrophobic matching of this peptide. The fluorescence studies exploit the intrinsic fluorescence of the only tryptophan residue in a synthetic peptide corresponding to the fourth transmembrane domain of the AChR γ subunit (γM4-Trp 6 ) reconstituted in lipid bilayers of varying thickness, and combine this information with quenching studies using depth-sensitive phosphatidylcholine spin-labeled probes and acrylamide, polarization of fluorescence, and generalized polarization of Laurdan. A direct correlation was found between bilayer width and the depth of insertion of Trp 6 . We further extend our recent MD study of the conformational dynamics of the AChR channel to focus on the crosstalk between M4 and the lipid-belt region. The isolated γM4 peptide is shown to possess considerable orientational flexibility while maintaining a linear α-helical structure, and to vary its tilt depending on bilayer width and cholesterol (Chol) content. MD studies also show that γM4 also establishes contacts with the other TM peptides on its inner face, stabilizing a shorter TM length that is still highly sensitive to the lipid environment. In the native membrane the topology of the M4 ring is likely to exhibit a similar behavior, dynamically modifying its tilt to match the hydrophobic thickness of the bilayer. [ABSTRACT FROM AUTHOR]

The nicotinic acetyicholine receptor (AChR) is the paradigm of ligand-gated ion channels, integral membrane proteins that mediate fast intercellular communication in response to neurotransmitters. A 35-ns molecular dynamics simulation has been performed to explore the conformational dynamics of the entire membrane-spanning region, including the ion channel pore of the AChR. In the simulation, the 20 trans- membrane (TM) segments that comprise the whole TM domain of the receptor were inserted into a large dipalmitoylphosphatidylcholine (DPPC) bilayer. The dynamic behavior of individual TM segments and their corresponding AChR subunit helix bundles was examined in order to assess the contribution of each to the conformational transitions of the whole channel. Asymmetrical and asynchronous motions of the M1-M3 TM segments of each subunit were revealed. In addition, the outermost ring of five M4 TM helices was found to convey the effects exerted by the lipid molecules to the central channel domain. Remarkably, a closed-to-open conformational shift was found to occur in one of the channel ring positions in the time scale of the present simulations, the possible physiological significance of which is discussed. [ABSTRACT FROM AUTHOR]

Curcuma alismatifolia is a significant cut flower, but its postharvest preservation remains challenging. 6-benzylaminopurine (6-BA) can effectively delay senescence in various horticultural plants. This study demonstrated that soaking and spraying 6-BA significantly extended the vase life of four C. alismatifolia varieties, particularly 'Siam Shadow', which had the longest vase life extension of 5.1 days by spraying and 3.7 days by soaking. Further analyses of physiological, biochemical, and transcriptomic indicators were conducted on the bracts of 'Siam Shadow' under 50 mg/L 6-BA spraying treatment and control at three senescence stages: S1 (4th day), S2 (8th day), and S3 (12th day) after vase placement. The results indicated that 6-BA spraying increased superoxide dismutase (SOD) and catalase (CAT) activities in S1 and S2 while increasing peroxidase (POD) and decreasing jasmonic acid (JA) contents in all stages. Orthogonal Partial Least Squares-Discriminant Analysis (OPLS-DA) identified JA content as the key differential indicator of 6-BA treatment. Transcriptome analysis revealed that 6-BA treatment upregulated 102 antioxidant-related genes and downregulated 27 JA biosynthesis-related genes and 16 JA signal transduction-related genes in all stages. Among them, the gene families of POD , LOX , and JAZ , which are involved in peroxidase activity, JA biosynthesis, and JA signal transduction, respectively, may play major roles in delaying C. alismatifolia bract senescence. Moreover, correlation network analysis showed that 198 senescence-related transcription factors (WRKYs, NACs, etc.) were significantly correlated with 77 antioxidant-related genes, 22 JA biosynthesis-related genes, and 12 JA signal transduction-related genes. These findings suggest that 6-BA is a potential preservative for C. alismatifolia cut flowers and that it may primarily affect the expression of genes related to senescence-associated transcription factors, JA biosynthesis and signal transduction, and antioxidant enzymes, thereby reducing JA content and enhancing antioxidant enzyme activities, consequently delaying C. alismatifolia bract senescence. • 6-BA treatment at 50 mg/L by soaking or spraying prolonged vase life of four C. alismatifolia cut flowers. • 6-BA spray at 50 mg/L enhanced the level of protein and some antioxidant enzymes activities, and reduced the level of salicylic acid and jasmonic acid in C. alismatifolia bracts compared to the control. • 6-BA spray at 50 mg/L altered the expression of antioxidant, JA biosynthesis and signal transduction, and senescence-associated transcription factor genes in C. alismatifolia bracts. [ABSTRACT FROM AUTHOR]

G protein-coupled receptors represent the largest family of human membrane proteins and are modulated by a variety of drugs and endogenous ligands. Molecular modeling techniques, especially enhanced sampling methods, have provided significant insight into the mechanism of GPCR–ligand recognition. Notably, the crucial role of the membrane in the ligand-receptor association process has earned much attention. Additionally, docking, together with more accurate free energy calculation methods, is playing an important role in the design of novel compounds targeting GPCRs. Here, we summarize the recent progress in the computational studies focusing on the above issues. In the future, with continuous improvement in both computational hardware and algorithms, molecular modeling would serve as an indispensable tool in a wider scope of the research concerning GPCR–ligand recognition as well as drug design targeting GPCRs. [ABSTRACT FROM AUTHOR]

The ongoing COVID-19 pandemic caused by SARS-CoV-2 has raised global concern for public health and economy. The development of therapeutics and vaccines to combat this virus is continuously progressing. Multi-omics approaches, including genomics, transcriptomics, proteomics, metabolomics, epigenomics and metallomics, have helped understand the structural and molecular features of the virus, thereby assisting in the design of potential therapeutics and accelerating vaccine development for COVID-19. Here, we provide an up-to-date overview of the latest applications of multi-omics technologies in strategies addressing COVID-19, in order to provide suggestions towards the development of highly effective knowledge-based therapeutics and vaccines. [ABSTRACT FROM AUTHOR]

The papain-like protease (PLpro) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) plays a critical role in the proteolytic processing of viral polyproteins and the dysregulation of the host immune response, providing a promising therapeutic target. Here, we report the structure-guide design of novel peptidomimetic inhibitors covalently targeting SARS-CoV-2 PLpro. The resulting inhibitors demonstrate submicromolar potency in the enzymatic assay (IC50 = 0.23 μM) and significant inhibition of SARS-CoV-2 PLpro in the HEK293T cells using a cell-based protease assay (EC50 = 3.61 μM). Moreover, an X-ray crystal structure of SARS-CoV-2 PLpro in complex with compound 2 confirms the covalent binding of the inhibitor to the catalytic residue cysteine 111 (C111) and emphasizes the importance of interactions with tyrosine 268 (Y268). Together, our findings reveal a new scaffold of SARS-CoV-2 PLpro inhibitors and provide an attractive starting point for further optimization. [ABSTRACT FROM AUTHOR]

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has forced the development of direct-acting antiviral drugs due to the coronavirus disease 2019 (COVID-19) pandemic. The main protease of SARS-CoV-2 is a crucial enzyme that breaks down polyproteins synthesized from the viral RNA, making it a validated target for the development of SARS-CoV-2 therapeutics. New chemical phenotypes are frequently discovered in natural goods. In the current study, we used a fluorogenic assay to test a variety of natural products for their ability to inhibit SARS-CoV-2 Mpro. Several compounds were discovered to inhibit Mpro at low micromolar concentrations. It was possible to crystallize robinetin together with SARS-CoV-2 Mpro, and the X-ray structure revealed covalent interaction with the protease's catalytic Cys145 site. Selected potent molecules also exhibited antiviral properties without cytotoxicity. Some of these powerful inhibitors might be utilized as lead compounds for future COVID-19 research. [ABSTRACT FROM AUTHOR]

Targeting the interaction between the spike protein receptor binding domain (S-RBD) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and angiotensin-converting enzyme 2 (ACE2) is a potential therapeutic strategy for treating coronavirus disease 2019 (COVID-19). However, we still lack small-molecule drug candidates for this target due to the missing knowledge in the hot spots for the protein-protein interaction. Here, we used NanoBiT technology to identify three Ginkgolic acids from an in-house traditional Chinese medicine (TCM) library, and they interfere with the S-RBD/ACE2 interplay. Our pseudovirus assay showed that one of the compounds, Ginkgolic acid C17:1 (GA171), significantly inhibits the entry of original SARS-CoV-2 and its variants into the ACE2-overexpressed HEK293T cells. We investigated and proposed the binding sites of GA171 on S-RBD by combining molecular docking and molecular dynamics simulations. Site-directed mutagenesis and surface plasmon resonance revealed that GA171 specifically binds to the pocket near R403 and Y505, critical residues of S-RBD for S-RBD interacting with ACE2. Thus, we provide structural insights into developing new small-molecule inhibitors and vaccines against the proposed S-RBD binding site. [Display omitted] [ABSTRACT FROM AUTHOR]

Caladium (Caladium × Hortulanum Birdsey) is a popular ornamental plant with a wide range of vibrant leaf color among Araceae. Even after years of breeding, creating new caladium leaf color variations is extremely difficult. Molecular marker‐assisted selection is an effective approach for accelerating breeding, but few studies on the molecular markers associated with caladium traits have been performed. In the current study, 144 caladium accessions were used to examine 12 phenotypic characteristics. The coefficient of variation for four numerical characters ranged from 23.94% to 43.22%, and the Shannon–Wiener indexes for eight descriptive characters ranged from 0.13 to 1.52. Based on L*, a*, b*, C, h° values determined by a colorimeter and hierarchical cluster analysis, the leaf color can be divided into four groups: pale green, green, light pink, and red. Furthermore, 7708 new SSR loci were identified by transcriptome sequencing, and 26 SSR markers with high polymorphism and reproducibility were screened. Genetic structure, NJ clustering, and PCoA analysis revealed that 144 accessions could be divided into three clusters, with genetic structure being closely related to germplasm origin. An association analysis revealed that the SSR markers 2, 1, 1, 1, 1, and 1 were mainly associated with petiole color, main vein color, blade upperside glossiness, and C, b*, and L* of leaf color (p < 0.01). These findings will serve as a valuable reference for evaluating germplasm resources and caladium molecular marker‐assisted breeding. [ABSTRACT FROM AUTHOR]

The coronavirus papain‐like protease (PLpro) plays an important role in the proteolytic processing of viral polyproteins and the dysregulation of the host immune response, providing a promising therapeutic target. However, the development of inhibitors against severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) PLpro is challenging owing to the restricted S1/S2 sites in the substrate binding pocket. Here we report the discovery of two activators of SARS‐CoV‐2 PLpro and the identification of the unique residue, cysteine 270 (C270), as an allosteric and covalent regulatory site for the activators. This site is also specifically modified by glutathione, resulting in protease activation. Furthermore, a compound was found to allosterically inhibit the protease activity by covalent binding to C270. Together, these results elucidate an unrevealed molecular mechanism for allosteric modulation of SARS‐CoV‐2 PLpro and provid a novel site for allosteric inhibitors design. [ABSTRACT FROM AUTHOR]

The coronavirus papain‐like protease (PLpro) plays an important role in the proteolytic processing of viral polyproteins and the dysregulation of the host immune response, providing a promising therapeutic target. However, the development of inhibitors against severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) PLpro is challenging owing to the restricted S1/S2 sites in the substrate binding pocket. Here we report the discovery of two activators of SARS‐CoV‐2 PLpro and the identification of the unique residue, cysteine 270 (C270), as an allosteric and covalent regulatory site for the activators. This site is also specifically modified by glutathione, resulting in protease activation. Furthermore, a compound was found to allosterically inhibit the protease activity by covalent binding to C270. Together, these results elucidate an unrevealed molecular mechanism for allosteric modulation of SARS‐CoV‐2 PLpro and provid a novel site for allosteric inhibitors design. [ABSTRACT FROM AUTHOR]

Caladiums are promising colorful foliage plants due to their dazzling colors of the leaves, veins, stripes, and patches, which are often cultivated in pots or gardens as decorations. Four wild species, including C. bicolor, C. humboldtii, C. praetermissum, and C. lindenii, were employed in this study, where their chloroplast (cp) genomes were sequenced, assembled, and annotated via high-throughput sequencing. The whole cp genome size ranged from 162,776 bp to 168,888 bp, and the GC contents ranged from 35.09% to 35.91%. Compared with the single large copy (LSC) and single small copy (SSC) regions, more conserved sequences were identified in the inverted repeat regions (IR). We further analyzed the different region borders of nine species of Araceae and found the expansion or contraction of IR/SSC regions might account for the cp genome size variation. Totally, 131 genes were annotated in the cp genomes, including 86 protein-coding genes (PCGs), 37 tRNAs, and eight rRNAs. The effective number of codons (ENC) values and neutrality plot analyses provided the foundation that the natural selection pressure could greatly affect the codon preference. The GC3 content was significantly lower than that of GC1 and GC2, and codons ending with A/U had higher usage preferences. Finally, we conducted phylogenetic relationship analysis based on the chloroplast genomes of twelve species of Araceae, in which C. bicolor and C. humboldtii were grouped together, and C. lindenii was furthest from the other three Caladium species occupying a separate branch. These results will provide a basis for the identification, development, and utilization of Caladium germplasm. [ABSTRACT FROM AUTHOR]

Nineteen new derivatives based on the structure of marine natural product tasiamide B were designed, synthesized, and evaluated for their inhibitory activity against BACE1, a potential therapeutic target for Alzheimer’s disease. The hydrophobic substituents Val at P 3 position, Leu at P 1 ′ position, Ala at P 2 ′ position, and Phe at P 3 ′ position were found to significantly affect the inhibition. Free carboxylic acid at C-terminus was also found to be important to the activity. In addition, the structure–activity relationships (SARs) were supported by molecular docking simulation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Betulinic acid derivatives show significant inhibitory activity against SARS-CoV-2 3CLpro. • The oxidation of the hydroxyl group at C-3 and esterification of the carboxylate group at C-28 can improve the inhibitory activity. • The inhibition rates of BA02 and BA05 are 78.1% and 82.5%, respectively. During the coronavirus reproduction process, 3-chymotrypsin-like protease (3CLpro) and papain-like protease (PLpro) are accountable for the fragmentation of two polyprotein precursors (pp1a/pp1ab) into substructural proteins. These two proteins are vital for the replication and transcription of the viral genome. Therefore, 3CLpro is a key protein and target for the design of coronavirus inhibitors. In previous studies, we found that betulinic acid has an inhibitory effect on 3CLpro, with 51.5 % inhibition of 3CLpro at 20 µM. Then, series of betulinic acid derivatives were designed, synthesized, and evaluated for their inhibition activities. The results showed that BA02 and BA05 showed significant inhibitory activity on 3CLpro with inhibitory rates of 78.1 % and 82.5 % at 20 µM, respectively. Further evaluation of these two compounds shows that their IC 50 values are 7.22 ± 0.14 μM and 6.40 ± 0.14 μM, respectively. [ABSTRACT FROM AUTHOR]

Sepsis, characterized with high risk of life‐threatening organ dysfunction, represents a major cause of health loss and the World Health Organization (WHO) labelled sepsis as the most urgent unmet medical need in 2017. The emerging biological understanding of the role of RIPK1 in sepsis has opened up an exciting opportunity to explore potent and selective RIPK1 inhibitors as an effective therapeutic strategy for SIRS and sepsis therapy. Herein, we have synthesized a class of highly potent dual‐mode RIPK1 inhibitors occupying both the allosteric and the ATP binding pockets, exemplified by compound 21 (ZB‐R‐55) which is about 10‐fold more potent than GSK2982772, and exhibits excellent kinase selectivity, good oral pharmacokinetics and good therapeutic effects in the LPS‐induced sepsis model, suggesting that compound ZB‐R‐55 is a highly promising preclinical candidate. [ABSTRACT FROM AUTHOR]

Sepsis, characterized with high risk of life‐threatening organ dysfunction, represents a major cause of health loss and the World Health Organization (WHO) labelled sepsis as the most urgent unmet medical need in 2017. The emerging biological understanding of the role of RIPK1 in sepsis has opened up an exciting opportunity to explore potent and selective RIPK1 inhibitors as an effective therapeutic strategy for SIRS and sepsis therapy. Herein, we have synthesized a class of highly potent dual‐mode RIPK1 inhibitors occupying both the allosteric and the ATP binding pockets, exemplified by compound 21 (ZB‐R‐55) which is about 10‐fold more potent than GSK2982772, and exhibits excellent kinase selectivity, good oral pharmacokinetics and good therapeutic effects in the LPS‐induced sepsis model, suggesting that compound ZB‐R‐55 is a highly promising preclinical candidate. [ABSTRACT FROM AUTHOR]

Arctigenin, derived from Arctium lappa L., has multiple pharmacological activities, including immunoregulatory, anti-diabetic, anti-tumor, and neuroprotective effects. Nevertheless, the potential therapeutic target of arctigenin in modulating inflammation remains undefined. In the present study, we identified that arctigenin was a phosphodiesterase-4 (PDE4) selective inhibitor for the first time. Further investigations were performed to fully uncover the effects and mechanism of arctigenin on experimental murine psoriasis model. Crystal structure determination, PDEs enzyme assay, and isothermal titration calorimetry were included to illustrate the binding specialty, inhibitory effects, and selectivity of arctigenin on PDE4D. The anti-inflammatory effects were conducted in LPS-activated human peripheral blood mononuclear cells (PBMCs) and RAW264.7 cells. Imiquimod-induced murine psoriasis was performed to uncover the therapeutic effects and mechanism of arctigenin in vivo. Arctigenin could bind to the catalytic domain of PDE4D via formation of hydrogen bonds as well as π-π stacking interactions between the dibenzyl butyrolactone of arctigenin and several residues of PDE4D. Accordingly, arctigenin showed prominent anti-inflammation in human PBMCs and murine RAW264.7 cells. PDE4 inhibition by arctigenin resulted in elevation of intracellular cyclic adenosine monophosphate (cAMP) and phosphorylation of cAMP-response element binding protein (CREB), which were largely blocked through intervention of protein kinase A (PKA) activity by H89 treatment or reduction of protein expression by siRNA transfection. Moreover, we first identified that a topical application of arctigenin ameliorated experimental psoriatic manifestations in imiquimod-induced murine psoriasis model by decreasing adhesion and chemotaxis of several inflammatory cells. Further proteomics analysis revealed that arctigenin could rectify the immune dysfunction and hyperactivation of keratinocytes in the inflamed skin microenvironments, which might be largely related to the expression of Keratins. The research provided credible clew that inhibition of PDE4 by arctigenin might function as the potential therapeutic approach for the treatment of psoriasis. [ABSTRACT FROM AUTHOR]

Deubiquitinase USP28 plays a crucial role in tumorigenesis by enhancing the stabilities of multiple cancer‐related proteins including c‐Myc, Notch1, and LSD1, and has become an attractive target for anticancer drug development. However, to date, only a few of USP28‐targeted active compounds have been developed, and the active compound‐binding pocket in USP28 has not been experimentally revealed yet. In this study, bioassay‐based high‐throughput screening was applied to discover USP28‐targeted inhibitors from the commercially available drug library. Vismodegib, an inhibitor of Hedgehog signaling pathway and FDA‐approved drug for the treatment of basal cell carcinoma, was found to exhibit inhibition activity against USP28 (IC50: 4.41 ± 1.08 μm). Multiple biophysical and biochemical techniques including NMR, ITC, thermal shift assay, HDX‐MS, and site‐directed mutagenesis analysis were then used to characterize the interaction between Vismodegib and USP28. The binding pocket in USP28 for Vismodegib, which is mainly composed of two helical structures spanning D255‐N278 and N286‐Y293, was revealed. According to the possible binding pose generated by HDX‐MS data‐defined molecular docking, the binding cavity occupied by Vismodegib in USP28 aligns well with one of the reported‐binding pockets in USP7 for its inhibitors. Furthermore, cellular assays were conducted to confirm that Vismodegib could interact with the evolutionarily related deubiquitinases USP28 and USP25 and downregulate the levels of the two enzymes' substrate proteins c‐Myc, Notch1, and Tankyrase‐1/2. [ABSTRACT FROM AUTHOR]

Fatty-acid binding protein 4 (FABP4) presents an attractive target for therapeutic intervention in metabolic and inflammatory diseases in recent years. However, highly similar three-dimensional structures and fatty acid binding ability of multiple FABP family members pose a significant challenge in design of FABP4-selective inhibitors. Particularly, inhibition of FABP3 raises safety concerns such as cardiac dysfunction and exercise intolerance. Here, we reported the discovery of new FABP4 inhibitors with high selectivity over FABP3 by exploiting the little structural difference in the ligand binding pockets of FABP4 and FABP3. On the basis of our previously reported FABP4 inhibitors with nanomolar potency, different substituents were further introduced to perfectly occupy two sub-pockets of FABP4 that are distinct from those of FABP3. Remarkably, a single methyl group introduction leads to the discovery of compound C3 that impressively exhibits a 601-fold selectivity over FABP3 when maintained nanomolar binding affinity for FABP4. Moreover, C3 also shows good metabolic stability and potent cellular anti-inflammatory activity, making it a promising inhibitor for further development. Therefore, the present study highlights the utility of the structure-based rational design strategy for seeking highly selective and potent inhibitors of FABP4 and the importance of identifying the appropriate subsite as well as substituent for gaining the desired selectivity. [Display omitted] • Highly selective FABP4 inhibitors were yielded by introducing a methyl group. • C3 displayed a remarkable 601-fold selectivity towards FABP4 over FABP3. • C3 exhibited good metabolic stability and potent anti-inflammatory activity. [ABSTRACT FROM AUTHOR]

Phosphodiesterase-4 (PDE4) and PDE5 responsible for the hydrolysis of intracellular cAMP and cGMP, respectively, are promising targets for therapeutic intervention in a wide variety of diseases. Here, we report the discovery of novel, drug-like PDE4 inhibitors by performing a high-throughput drug repurposing screening of 2560 approved drugs and drug candidates in clinical trial studies. It allowed us to identify eight potent PDE4 inhibitors with IC 50 values ranging from 0.41 to 2.46 μM. Crystal structures of PDE4 in complex with four compounds, namely ethaverine hydrochloride (EH), benzbromarone (BBR), CX-4945, and CVT-313, were further solved to elucidate molecular mechanisms of action of these new inhibitors, providing a solid foundation for optimizing the inhibitors to improve their potency as well as selectivity. Unexpectedly, selectivity profiling of other PDE subfamilies followed by crystal structure determination revealed that CVT-313 was also a potent PDE5 inhibitor with a binding mode similar to that of tadalafil, a marketed PDE5 inhibitor, but distinctively different from the binding mode of CVT-313 with PDE4. Structure-guided modification of CVT-313 led to the discovery of a new inhibitor, compound 2 , with significantly improved inhibitory activity as well as selectivity towards PDE5 over PDE4. Together, these results highlight the utility of the drug repurposing in combination with structure-based drug design in identifying novel inhibitors of PDE4 and PDE5, which provides a prime example for efficient discovery of drug-like hits towards a given target protein. [Display omitted] • 8 new drug-like PDE4 inhibitors were identified by drug repurposing screening. • The binding mode of the hits and PDE4 were validated by X-ray crystallography. • CVT-313 was revealed to be a potent inhibitor of PDE4 and PDE5. • Structure-guided optimization of CVT-313 resulted in compound 2. • Compound 2 showed increased potency and selectivity toward PDE5 over PDE4. [ABSTRACT FROM AUTHOR]

[Display omitted] • Baicalein and baicalin were identified as new inhibitors of cGAS. • Crystal structures determination revealed different binding modes of baicalein and baicalin to cGAS. • A more potent cGAS inhibitor was yielded through virtual screening based on the crystal structures of cGAS in complex with the flavonoids. Cyclic GMP-AMP synthase (cGAS) plays an important role in the inflammatory response. It has been reported that aberrant activation of cGAS is associated with a variety of immune-mediated inflammatory disorders. The development of small molecule inhibitors of cGAS has been considered as a promising therapeutic strategy for the diseases. Flavonoids, a typical class of natural products, are known for their anti-inflammatory activities. Although cGAS is closely associated with inflammation, the potential effects of natural flavonoid compounds on cGAS have been rarely studied. Therefore, we screened an in-house natural flavonoid library by pyrophosphatase (PP i ase) coupling assay and identified novel cGAS inhibitors baicalein and baicalin. Subsequently, crystal structures of the two natural flavonoids in complex with human cGAS were determined, which provide mechanistic insight into the anti-inflammatory activities of baicalein and baicalin at the molecular level. After that, a virtual screening based on the crystal structures of baicalein and baicalin in complex with human cGAS was performed. As a result, compound C20 was identified to inhibit both human and mouse cGAS with IC 50 values of 2.28 and 1.44 μM, respectively, and its detailed interactions with human cGAS were further revealed by the X-ray crystal structure determination. These results demonstrate the potential of natural products used as hits in drug discovery and provide valuable hints for further development of cGAS inhibitors. [ABSTRACT FROM AUTHOR]

The pandemic of coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has become a global crisis. Replication of SARS-CoV-2 requires the viral RNA-dependent RNA polymerase (RdRp) enzyme, a target of the antiviral drug remdesivir. Here we report the cryo–electron microscopy structure of the SARS-CoV-2 RdRp, both in the apo form at 2.8-angstrom resolution and in complex with a 50-base template-primer RNA and remdesivir at 2.5-angstrom resolution. The complex structure reveals that the partial double-stranded RNA template is inserted into the central channel of the RdRp, where remdesivir is covalently incorporated into the primer strand at the first replicated base pair, and terminates chain elongation. Our structures provide insights into the mechanism of viral RNA replication and a rational template for drug design to combat the viral infection. [ABSTRACT FROM AUTHOR]

A series of peptidomimetic compounds containing benzothiazolyl ketone and [2.2.1] azabicyclic ring was designed, synthesized and evaluated in the hope of obtaining potent oral 3CLpro inhibitors with improved pharmacokinetic properties. Among the target compounds, 11b had the best enzymatic potency (IC 50 = 0.110 μM) and 11e had the best microsomal stability (t 1/2 > 120 min) and good enzyme activity (IC 50 = 0.868 μM). Therefore, compounds 11b and 11e were chosen for further evaluation of pharmacokinetics in ICR mice. The results exhibited that the AUC (0-t) of 11e was 5143 h*ng/mL following single-dose oral administration of 20 mg/kg, and the F was 67.98%. Further structural modification was made to obtain compounds 11g - 11j based on 11e. Among them, 11j exhibited the best enzyme inhibition activity against SARS-CoV-2 3CLpro (IC 50 = 1.646 μM), the AUC (0-t) was 32473 h*ng/mL (20 mg/kg, po), and the F was 48.1%. In addition, 11j displayed significant anti-SARS-CoV-2 activity (EC 50 = 0.18 μM) and low cytotoxicity (CC 50 > 50 μM) in Vero E6 cells. All of the above results suggested that compound 11j was a promising lead compound in the development of oral 3CLpro inhibitors and deserved further research. [Display omitted] • Peptidomimetics 11j showed inhibitory activity against SARS-CoV-2 3CLpro (IC 50 = 1.646 μM). • 11j exhibited high oral plasma exposure and favorable oral bioavailability (F = 48.1%) in ICR mice. • 11j displayed excellent anti-SARS-CoV-2 activity in Vero E6 cells (EC 50 = 0.18 μM). • 11j was recognized as a promising lead compound for the treatment of COVID-19 and deserved further research. [ABSTRACT FROM AUTHOR]

[Display omitted] • A series of peptidomimetic SARS-CoV-2 3CLpro inhibitors were synthesized and evaluated. • Potent compounds were discovered by changing the P 2 and P 4 position. • Compounds 1a and 2b showed excellent enzyme inhibitory potency and significant antiviral activity. • The metabolic stability of 1a and 2b in liver microsomes was significantly improved. In this paper, a series of peptidomimetic SARS-CoV-2 3CL protease inhibitors with new P 2 and P 4 positions were synthesized and evaluated. Among these compounds, 1a and 2b exhibited obvious 3CLpro inhibitory activities with IC 50 of 18.06 nM and 22.42 nM, respectively. 1a and 2b also showed excellent antiviral activities against SARS-CoV-2 in vitro with EC 50 of 313.0 nM and 170.2 nM, respectively, the antiviral activities of 1a and 2b were 2- and 4-fold better than that of nirmatrelvir, respectively. In vitro studies revealed that these two compounds had no significant cytotoxicity. Further metabolic stability tests and pharmacokinetic studies showed that the metabolic stability of 1a and 2b in liver microsomes was significantly improved, and 2b had similar pharmacokinetic parameters to that of nirmatrelvir in mice. [ABSTRACT FROM AUTHOR]

[Display omitted] • A series of peptidomimetic SARS-CoV-2 3CLpro inhibitors were synthesized and evaluated. • Potent compounds were discovered by changing the P 2 and P 4 position. • Compounds 1a and 2b showed excellent enzyme inhibitory potency and significant antiviral activity. • The metabolic stability of 1a and 2b in liver microsomes was significantly improved. In this paper, a series of peptidomimetic SARS-CoV-2 3CL protease inhibitors with new P 2 and P 4 positions were synthesized and evaluated. Among these compounds, 1a and 2b exhibited obvious 3CLpro inhibitory activities with IC 50 of 18.06 nM and 22.42 nM, respectively. 1a and 2b also showed excellent antiviral activities against SARS-CoV-2 in vitro with EC 50 of 313.0 nM and 170.2 nM, respectively, the antiviral activities of 1a and 2b were 2- and 4-fold better than that of nirmatrelvir, respectively. In vitro studies revealed that these two compounds had no significant cytotoxicity. Further metabolic stability tests and pharmacokinetic studies showed that the metabolic stability of 1a and 2b in liver microsomes was significantly improved, and 2b had similar pharmacokinetic parameters to that of nirmatrelvir in mice. [ABSTRACT FROM AUTHOR]

Fibroblast growth factor receptors (FGFRs), a subfamily of receptor tyrosine kinases, are aberrant in various cancer types, and considered to be promising targets for cancer therapy. We started with a weak-active compound that was identified from our internal hepatocyte growth factor receptor (also called c-Met) inhibitor project, and optimized it with the guidance of a co-crystal structure of compound 8 with FGFR1. Through rational design, synthesis, and the biological evaluation of a series of 5H-pyrrolo[2,3-b]pyrazine derivatives, we discovered several potent FGFR kinase inhibitors. Among them, compound 13 displayed high selectivity and favorable metabolic properties, demonstrating a promising lead for further development. [ABSTRACT FROM AUTHOR]

The nuclear protein poly(ADP-ribose) polymerases-1/2 (PARP-1/2) are involved in DNA repair damaged by endogenous or exogenous process. And PARP-1/2 inhibitors have been proved to be clinically efficacious for DNA repair deficient tumors in the past decade. We have developed a series of 4,5,6,7-tetrahydrothienopyridin-2-yl benzimidazole carboxamides as novel and potent PARP-1/2 inhibitors. The best compound resulted from this series is compound 27 which displays excellent PARP-1 and PARP-2 inhibitory activity with IC 50 of 18 nM and 42 nM, respectively. Furthermore, it can selectively kill BRCA2 deficient V-C8 cells with a CC 50 of 920 nM. In the MDA-MB-436 (BRCA-1 mutant) xenograft model, this compound was well tolerated and showed single-agent activity. Based on the results above, compound 27 has been selected as a lead candidate targeting PARP-1/2 and its preclinical characterization is also underway. [ABSTRACT FROM AUTHOR]

The c-Met kinase has emerged as an attractive target for developing antitumor agents because of its close relationship with the development of many human cancers, poor clinical outcomes and even drug resistance. A series of novel c-Met kinase inhibitors have been identified with multiple workflow in this work, including virtual screening, X-ray crystallography, biological evaluation and structural optimization. The experimentally determined crystal structure of the best hit compound HL-11 in c-Met kinase domain was highly consistent with the computational prediction. Comparison of the hit compounds with different c-Met kinase inhibitory activity by molecular dynamics simulations suggested the key protein-ligand interactions for structural optimization. Based on these, structural optimization produced compound 11e with better c-Met kinase inhibitory activity and improved anti-proliferative activity. These experimental findings proved the reliability and efficiency of our in silico methods. This strategy will facilitate further lead discovery and optimization for novel c-Met kinase inhibitors. [ABSTRACT FROM AUTHOR]

The 3C-like protease (3CLpro) is essential for the replication and transcription of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), making it a promising target for the treatment of corona virus disease 2019 (COVID-19). In this study, a series of 2,3,5-substituted [1,2,4]-thiadiazole analogs were discovered to be able to inhibit 3CLpro as non-peptidomimetic covalent binders at submicromolar levels, with IC 50 values ranging from 0.118 to 0.582 μM. Interestingly, these compounds were also shown to inhibit PLpro with the same level of IC 50 values, but had negligible effect on proteases such as chymotrypsin, cathepsin B, and cathepsin L. Subsequently, the antiviral abilities of these compounds were evaluated in cell-based assays, and compound 6g showed potent antiviral activity with an EC 50 value of 7.249 μM. It was proposed that these compounds covalently bind to the catalytic cysteine 145 via a ring-opening metathesis reaction mechanism. To understand this covalent-binding reaction, we chose compound 6a , one of the identified hit compounds, as a representative to investigate the reaction mechanism in detail by combing several computational predictions and experimental validation. The process of ring-opening metathesis was theoretically studied using quantum chemistry calculations according to the transition state theory. Our study revealed that the 2,3,5-substituted [1,2,4]-thiadiazole group could covalently modify the catalytic cysteine in the binding pocket of 3CLpro as a potential warhead. Moreover, 6a was a known GPCR modulator, and our study is also a successful computational method-based drug-repurposing study. 2,3,5-substituted [1,2,4]-thiadiazoles as potent inhibitors targeting 3C-Like protease were proposed to covalently bind with the catalytic cysteine via a ring-opening metathesis reaction mechanism. [Display omitted] • Discovery of a new type of non-peptidomimetic covalent inhibitor against 3CLpro of SARS-CoV-2 with inhibition as strong as sub-micromolar level. • A molecular mechanism of the ring-opening metathesis was explored by combining types of computational and experimental technologies. • A multi-technologies integrated research paradigm for lead identification, validation and molecular mechanism study was explored. [ABSTRACT FROM AUTHOR]

[Display omitted] Molecular chaperone HSP90 has been considered as a promising target for anti-cancer drug development for years. However, due to the heat shock response induced by the ATP competitive inhibitors against HSP90, the therapeutic efficacies of the compounds are compromised, which consequently restricts the clinical use of HSP90-targeted inhibitors. Therefore, there is a need to discover novel HSP90-targeted modulators which exhibit acceptable inhibition activity against the chaperone and do not induce significant heat shock response in the meantime. Here in this study, we firstly developed a tip-based affinity selection-mass spectrometry platform with optimized experimental conditions/parameters for HSP90-targeted active compound screening, and then applied it to fish out inhibitors against HSP90 from a collection of 2,395 compounds composed of FDA-approved drugs and drug candidates. Dipyridamole, which acts as an anti-thrombotic agent by modulating multiple targets and has a long history of safe use, was identified to interact with HSP90′s N -terminal domain. The following conducted biophysical and biochemical experiments demonstrated that Dipyridamole could bind to HSP90′s ATP binding pocket and function as an ATP competitive inhibitor of the chaperone. Finally, cellular-based assays including CESTA, cell viability assessment and proteomic analysis etc. were performed to evaluate whether the interaction between HSP90 and Dipyridamole contributes to the anti-tumor effects of the compound. We then found that Dipyridamole inhibits the growth and proliferation of human cancer cells by downregulating cell cycle regulators and upregulating apoptotic cell signaling, which are potentially mediated by the binding of Dipyridamole to HSP90 and to PDEs (phosphodiesterases), respectively. [ABSTRACT FROM AUTHOR]

FB2001 is a drug candidate that targets the main protease of SARS-CoV-2 via covalently binding to cysteine 145. In this study, we evaluated the inhibitory activities of FB2001 against several SARS-CoV-2 variants in vitro and in vivo (in mice), and we also evaluated the histopathological analysis and immunostaining of FB2001 on lung and brain which have been rarely reported. The results showed that FB2001 exhibited potent antiviral efficacy against several current SARS-CoV-2 variants in Vero E6 cells, namely, B.1.1.7 (Alpha): EC 50 = 0.39 ± 0.01 μM, EC 90 = 0.75 ± 0.01 μM; B.1.351 (Beta): EC 50 = 0.28 ± 0.11 μM, EC 90 = 0.57 ± 0.21 μM; B.1.617.2 (Delta): EC 50 = 0.27 ± 0.05 μM, EC 90 = 0.81 ± 0.20 μM; B.1.1.529 (Omicron): EC 50 = 0.26 ± 0.06 μM and EC 50 = 0.042 ± 0.007 μM (in the presence of a P-glycoprotein inhibitor). FB2001 remained potent against SARS-CoV-2 replication in the presence of high concentrations of human serum, which indicating that human serum had no significant effect on the in vitro inhibitory activity. Additionally, this inhibitor exhibited an additive effect against SARS-CoV-2 when combined with Remdesivir. Furthermore, FB2001 significantly reduced the SARS-CoV-2 copy numbers and titers in the lungs and brains in vivo , and alleviated the pathological symptoms. In addition, FB2001 could alleviated local bleeding, erythrocyte overflow, edema, and inflammatory cell infiltration in brain tissue, and inhibitors reducing viral titers and improving inflammation in the brain have been rarely reported. A physiologically based pharmacokinetic model was established and verified to predict the FB2001 concentration in human lungs. When FB2001 was administered at 200 mg twice a day for 5 days, the observed C trough ss in plasma and predicted C trough ss of lung total concentration were 0.163 and 2.5 μg/mL, which were approximately 9 and 132-fold higher than the EC 50 of 0.019 μg/mL (0.042 μM) against Omicron variant. Taken together, our study suggests that FB2001 is a promising therapeutic agent in COVID-19 treatment and can be combined with remdesivir to achieve improved clinical outcomes. Owing to its good safety and tolerability in healthy human (NCT05197179 and NCT04766931), FB2001 has been approved for Phase II/III clinical trial (NCT05445934). [Display omitted] • FB2001 exhibited potent antiviral efficacy against several SARS-CoV-2 variants, such as Alpha, Beta, Delta and Omicron. • FB2001 exhibited an additive effect against SARS-CoV-2 when combined with remdesivir. • FB2001 reduced the SARS-CoV-2 load in the lungs and brains, and alleviated the pathological symptoms in mice. • FB2001 showed good safety and tolerability in humans. • FB2001 has been approved for Phase II/III clinical trials. [ABSTRACT FROM AUTHOR]

[Display omitted] • A fragment-based hit screening resulted in several fragment inhibitors of the ZIKV NS2B/NS3 protease. • Crystal structures of the ZIKV NS2B/NS3 protease in complex with a tetrapeptide and a fragment were determined, revealing the detailed but distinct protease-inhibitor interaction patterns. • A novel inhibitor with a higher ligand-binding efficiency was designed based on two complex structures. Zika virus (ZIKV) has been a serious public health problem, and there is no vaccine or drug approved for the prevention or treatment of ZIKV yet. The ZIKV NS2B/NS3 protease plays an important role in processing the virus precursor polyprotein and is thus a promising target for antiviral drugs development. In order to discover novel inhibitors of this protease, we carried out a fragment-based hit screening and characterized protein-inhibitor interactions using the X-ray crystallography together with isothermal titration calorimetry. We reported two high-resolution crystal structures of the protease (bZiProC143S) in complex with an active fragment as well as a tetrapeptide, revealing that there is domain swapping in the protein structures and two ligands only occupy the substrate-binding pocket of one copy in a symmetric unit. Based on the detailed binding modes of two ligands revealed by crystal structures, we designed a novel inhibitor which inhibits the NS2B/NS3 protease with a higher potency than the fragment and possesses a higher ligand-binding efficiency and a comparable IC 50 compared to the tetrapeptide. These results thus provide a structural basis and valuable hint for development of more potent inhibitors of the ZIKV NS2B/NS3 protease. [ABSTRACT FROM AUTHOR]

The coronavirus papain‐like protease (PLpro) plays an important role in the proteolytic processing of viral polyproteins and the dysregulation of the host immune response, providing a promising therapeutic target. However, the development of inhibitors against severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) PLpro is challenging owing to the restricted S1/S2 sites in the substrate binding pocket. Here we report the discovery of two activators of SARS‐CoV‐2 PLpro and the identification of the unique residue, cysteine 270 (C270), as an allosteric and covalent regulatory site for the activators. This site is also specifically modified by glutathione, resulting in protease activation. Furthermore, a compound was found to allosterically inhibit the protease activity by covalent binding to C270. Together, these results elucidate an unrevealed molecular mechanism for allosteric modulation of SARS‐CoV‐2 PLpro and provid a novel site for allosteric inhibitors design. [ABSTRACT FROM AUTHOR]

c-Met/HGF overexpression has been detected in many human malignancies including tumors which are resistant to anticancer therapy. Disrupting the aberrant c-Met/HGF axis has enjoyed significant progress in both preclinical and clinical antitumor campaign. To eliminate the OCH 2 -related metabolic deficiency of our previously reported triazolotriazine 2 , we synthesized a series of CH 2 -/CF 2 -linked triazolotriazines and assessed their c-Met activities, leading to the highly potent compound 23 with IC 50 values of 0.24 nM of enzymatic activity in c-Met and 0.85 nM of cellular activity in EBC-1 cancer cell line, as well as with complete tumor regression in EBC-1 xenograft mice model at dose of 25 mg/kg via oral administration. Based on its potent anti-proliferative activities and favorable pharmacokinetic properties, 23 has been selected as a drug candidate for preclinical investigation. [ABSTRACT FROM AUTHOR]

Lipoprotein-associated phospholipase A2 (Lp-PLA2) represents a promising therapeutic target for atherosclerosis and Alzheimer's disease. Here we reported the first crystal structures of Lp-PLA2 bound with reversible inhibitors and the thermodynamic characterization of complexes. High rigidity of Lp-PLA2 structure and similar binding modes of inhibitors with completely different scaffolds are revealed. It not only provides the molecular basis for inhibitory activity but also sheds light on the essential features of Lp-PLA2 recognition with reversible inhibitors. [ABSTRACT FROM AUTHOR]

Bacterial porins are water-filled β-barrel channels that allow translocation of solutes across the outer membrane. They feature a constriction zone, contributed by the plunging of extracellular loop 3 (L3) into the channel lumen. Porins are generally in the open state, but undergo gating in response to external voltages. To date the underlying mechanism is unclear. Here we report results from molecular dynamics simulations on the two porins of Providenica stuartii, Omp-Pst1 and Omp-Pst2, which display distinct voltage sensitivities. Voltage gating was observed in Omp-Pst2, where the binding of cations in-between L3 and the barrel wall results in exposing a conserved aromatic residue in the channel lumen, thereby halting ion permeation. Comparison of Omp-Pst1 and Omp-Pst2 structures and trajectories suggests that their sensitivity to voltage is encoded in the hydrogen-bonding network anchoring L3 onto the barrel wall, as we observed that it is the strength of this network that governs the probability of cations binding behind L3. That Omp-Pst2 gating is observed only when ions flow against the electrostatic potential gradient of the channel furthermore suggests a possible role for this porin in the regulation of charge distribution across the outer membrane and bacterial homeostasis. [ABSTRACT FROM AUTHOR]

The signal transduction of acetylatedhistone can be processedthrough a recognition module, bromodomain. Several inhibitors targetingBRD4, one of the bromodomain members, are in clinical trials as anticancerdrugs. Hereby, we report our efforts on discovery and optimizationof a new series of 2-thiazolidinones as BRD4 inhibitors along ourprevious study. In this work, guided by crystal structure analysis,we reversed the sulfonamide group and identified a new binding mode.A structure–activity relationship study on this new seriesled to several potent BRD4 inhibitors with IC50of about0.05–0.1 μM in FP binding assay and GI50of0.1–0.3 μM in cell based assays. To complete the lead-likeassessment of this series, we further checked its effects on BRD4downstream protein c-Myc, investigated its selectivity among fivedifferent bromodomain proteins, as well as the metabolic stabilitytest, and reinforced the utility of 2-thiazolidinone scaffold as BETbromodomain inhibitors in novel anticancer drug development. [ABSTRACT FROM AUTHOR]

Fatty acid binding protein 4 (FABP4) is a potential drug target for diabetes and atherosclerosis. For discovering new chemical entities as FABP4 inhibitors, structure-based virtual screening (VS) was performed, bioassay demonstrated that 16 of 251 tested compounds are FABP4 inhibitors, among which compound m1 are more active than endogenous ligand linoleic acid (LA). Based on the structure of m1 , new derivatives were designed and prepared, leading to the discovery of two more potent inhibitors, compounds 9 and 10 . To further explore the binding mechanisms of these new inhibitors, we determined the X-ray structures of the complexes of FABP4- 9 and FABP4- 10 , which revealed similar binding conformations of the two compounds. Residue Ser53 and Arg126 formed direct hydrogen bonding with the ligands. We also found that 10 could significantly reduce the levels of lipolysis on mouse 3T3-L1 adipocytes. Taken together, in silico , in vitro and crystallographic data provide useful hints for future development of novel inhibitors against FABP4. [ABSTRACT FROM AUTHOR]

HSP90 is ubiquitously overexpressed in a broad spectrum of human cancers and has been recognized as an attractive target for cancer treatment. Here, we described the fragment screening, synthesis and structure-activity relationship studies of small molecule inhibitors with 4,5-diarylisoxazole scaffold targeting HSP90. Among them, the compound N -(3-(2,4-dihydroxy-5-isopropylphenyl)-4-(4-((4-morpholinopiperidin-1-yl)methyl)phenyl)isoxazol-5-yl)cyclopropanecarboxamide ( 108 ) showed high affinity for binding to HSP90 (FP binding assay, IC 50 = 0.030 μM) and inhibited the proliferation of various human cancer cell lines with averaging GI 50 about 88 nM. Compound 108 exhibited its functional inhibition of HSP90 by depleting key signaling pathways and concomitantly elevating of HSP70 and HSP27 in U-87MG cells. Further in vivo studies showed that compound 108 strongly suppressed the tumor growth of human glioblastoma xenograft model U-87MG with T/C = 18.35% at 50 mg/kg q3w/2.5w. Moreover, compound 108 also exhibited good pharmacokinetic properties. Together, our study implicates that compound 108 is a promising candidate of HSP90 inhibitor and is currently advanced to preclinical study. [ABSTRACT FROM AUTHOR]

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) 3CL protease (3CLpro) has been regarded as an extremely promising antiviral target for the treatment of coronavirus disease 2019 (COVID-19). Here, we carried out a virtual screening based on commercial compounds database to find novel covalent non-peptidomimetic inhibitors of this protease. It allowed us to identify 3 hit compounds with potential covalent binding modes, which were evaluated through an enzymatic activity assay of the SARS-CoV-2 3CLpro. Moreover, an X-ray crystal structure of the SARS-CoV-2 3CLpro in complex with compound 8 , the most potent hit with an IC 50 value of 8.50 μM, confirmed the covalent binding of the predicted warhead to the catalytic residue C145, as well as portrayed interactions of the compound with S1' and S2 subsites at the ligand binding pocket. Overall, the present work not merely provided an experiment-validated covalent hit targeting the SARS-CoV-2 3CLpro, but also displayed a prime example to seeking new covalent small molecules by a feasible and effective computational approach. [Display omitted] • 3 hits against the SARS-CoV-2 3CLpro identified by a virtual screening followed by covalent docking. • The most potent hit exhibited low micromolar binding potency. • The covalent binding pose of the hit validated by X-ray protein crystallography. • 2 hits demonstrated moderate reactivities through a glutathione assay. • An efficient and feasible strategy for discovery of novel covalent binders. [ABSTRACT FROM AUTHOR]

• A native mass spectrometry-based affinity-selection coupled with a natural compound identification procedure was developed. • With the optimized method, compounds that bind to SARS-CoV-2 3CLpro were screened out from complex mixtures. • Protein-ligand complexes and stoichiometric numbers could be visualized and alerts could be given for nonspecific binding. • The binding affinity between protein and compound could be easily determined by mass spectrometry. [Display omitted] A native MS-based affinity-selection method was developed to screen compounds that target SARS-CoV-2 3CLpro from TCMs crude extracts. The 3C-like protease (3CLpro) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is essential to the virus life cycle and is supposed to be a potential target for the treatment of coronaviral infection. Traditional Chinese medicines (TCMs) have played an impressive role in the treatment of COVID-19 in China. The effectiveness of TCM formulations prompts scientists to take continuous effort on searching for bioactive small molecules from the ancient resources. Herein, we developed a native mass spectrometry-based affinity-selection method for rapid screening of active small molecules from crude herbal extracts applied for COVID-19 therapy. Six common herbs named Lonicera japonica, Scutellaria baicalensis, Forsythia suspensa, Glycyrrhiza uralensis, Cirsium japonicum, and Andrographis paniculata were investigated. After preliminary separation of the crude extracts, the fractions were incubated with 3CLpro. A native MS-based affinity screening assay was then conducted to search for the protein-ligand complexes. A UHPLC-Q/TOF-MS with UNIFI data acquisition and data processing software was applied to identify the hit compounds. Standard compounds were used to verify the outcomes. Among the 16 hits, three flavonoids, baicalein, scutellarein and ganhuangenin, were identified as potential noncovalent inhibitors against 3CLpro with IC 50 values of 0.94, 3.02, and 0.84 μM, respectively. Their binding affinities were further characterized by native MS, with K d values being 1.43, 3.85, and 1.09 μM, respectively. Overall, we established an efficient native MS-based strategy for discovering 3CLpro ligands from crude mixtures, which supplies a potential strategy of small molecule lead discovery from TCMs. [ABSTRACT FROM AUTHOR]

Abstract: Heat shock protein 90 (HSP90) is a molecular chaperone to fold and maintain the proper conformation of many signaling proteins, especially some oncogenic proteins and mutated unstable proteins. Inhibition of HSP90 was recognized as an effective approach to simultaneously suppress several aberrant signaling pathways, and therefore it was considered as a novel target for cancer therapy. Here, by integrating several techniques including the fragment-based drug discovery method, fragment merging, computer aided inhibitor optimization, and structure-based drug design, we were able to identify a series of HSP90 inhibitors. Among them, inhibitors 13, 32, 36 and 40 can inhibit HSP90 with IC50 about 20–40nM, which is at least 200-fold more potent than initial fragments in the protein binding assay. These new HSP90 inhibitors not only explore interactions with an under-studied subpocket, also offer new chemotypes for the development of novel HSP90 inhibitors as anticancer drugs. [Copyright &y& Elsevier]

Thesignificance of halogen bonding in protein–ligand interactionshas been recognized recently. We present here the first comprehensivethermodynamic and structural characterization of halogen bonding inPDE5–inhibitor interactions. ITC studies reveal that bindingstrength of the halogen bonding between chlorine, bromine, and iodineof inhibitor and the protein is −1.57, −3.09, and −5.59kJ/mol, respectively. The halogens interact with the designed residueY612 and an unexpected buried water molecule. [ABSTRACT FROM AUTHOR]

Abstract: We recently discovered and reported dual inhibitor 5 of AChE and BACE1 with N-benzylpiperidine ethyl as C-terminus. Compound 5 showed potent inhibitory activities for BACE1, and could reduce endogenous Aβ1–40 production in APP transgenic mice. In present work, we rapidly identified substituted triazole as the C-terminus of compound 5 by replacing the benzylpiperidine ethyl group with click chemistry and tested these synthesized compounds by in situ screening assay. As revealed by the crystal structures of BACE1 in complex with our triazole compound 12, we found that Pro70 and Thr72 located in the flap region were the critical components for binding with these inhibitors. With the aid of the crystal structure, a new series of five-membered heterocyclic compounds was prepared in order to explore the structure–activity relationship (SAR) of this class of molecules. From these efforts, pyrazole was discovered as a novel C-terminus of BACE1 inhibitors. After further modification of pyrazole with variable substituents, compound 37 exhibited good potency in enzyme inhibition assay (IC50 = 0.025 μM) and compound 33 showed moderate inhibition effects on Aβ production of APP transfected HEK293 cells. Moreover, these pyrazole derivatives demonstrated good selectivity versus cathepsin D. Our results indicated that the vicinity of Pro70 and Thr72 might be utilized as a subsite, and the discovered pyrazole derivatives might provide useful hints for developing novel BACE1 inhibitors as anti-AD drugs. [Copyright &y& Elsevier]

Abstract: The substituents both at the 6-position of the 5-bromopyrimidinone ring and at the 5′-position of the phenyl ring of 5-bromopyrimidin-4(3H)-ones were explored. 5-Bromo-6-isopropyl-2-(2-propoxy-phenyl)pyrimidin-4(3H)-one was identified as a new scaffold for potent PDE5 inhibitors. The crystal structures of PDE5/2e and PDE5/10a complexes provided a structural basis for the inhibition of 5-bromopyrimidinones to PDE5. In addition, it was also found that there is a great tolerance for the substitution at the 5′-position of the phenyl ring of 5-bormopyrimidinones and the resulted compound 13a has the highest inhibition activity to PDE5 (IC50, 1.7nM). [Copyright &y& Elsevier]

The genus Curcuma is widely recognized for its diversity of medicinal and culinary uses yet metabolomic differences among Curcuma species are largely unknown, due to the lack of broadly targeted analytical studies. Here, Ultra-Performance Liquid Chromatography-Mass Spectrometry/Mass Spectrometry (UPLC-MS/MS) analysis was employed to interrogate the metabolomes of five Curcuma species which are commonly used in Chinese herbal medicine (C. aromatica , C. elata , C. longa , C. caesia and C. phaeocaulis). By processing these results through a pathway enrichment analysis, 432 metabolites (some associated with the curcumin pathway) were identified that varied by species. The quantity of curcuminoids in C. longa were found to be higher than that in the other four Curcuma species analyzed in this study. In addition, C. longa was found to have a greater diversity of phenolic acids, amino acid derivatives, and flavonoids associated with the curcumin biosynthesis pathway. However, medicinal compounds such as 6-gingerol were found in lower quantities in C. longa compared to all other species in this study. This study provides new insights into Curcuma phytochemical pathways and allows for the development of functional foods tailored to specific needs from these species. • UPLC-MS/MS analysis was employed to interrogate the metabolomes of five Curcuma species. • 432 metabolites were identified that varied by five Curcuma species. • C. longa was the most diverse in phenolic acids, amino acid derivatives, and flavonoids. • The flavonoids were associated with the curcumin biosynthesis pathway. [ABSTRACT FROM AUTHOR]

Previous researches suggested that polysaccharides from brown algae had anti-virus activity. We hypothesized that nature polysaccharide from marine plants might have the effect on anti-SARS-CoV-2 activity. By high throughput screening to target 3CLpro enzyme using polysaccharides library, we discover a crude polysaccharide 375 from seaweed Ecklonia kurome blocked 3CLpro enzymatic activity and shows good anti-SARS-CoV-2 infection activity in cell. Further, we show that homogeneous polysaccharide 37502 from the 375 may bind to 3CLpro well and disturb spike protein binding to ACE2 receptor. The structure characterization uncovers that 37502 is alginate. These results imply that the bioactivities of 375 on SARS-CoV-2 may target multiple key molecules implicated in the virus infection and replication. The above results suggest that 375 may be a potential drug candidate against SARS-CoV-2. [Display omitted] [ABSTRACT FROM AUTHOR]

A seriesof benzo[de][1,7]naphthyridin-7(8H)-ones possessing a functionalized long-chain appendagehave been designed and evaluated as novel PARP1 inhibitors. The initialeffort led to the first-generation PARP1 inhibitor 26bearing a terminal phthalazin-1(2H)-one frameworkand showing remarkably high PARP1 inhibitory activity (0.31 nM) butonly moderate potency in the cell. Further effort generated the second-generationlead 41, showing high potency against both the PARP1enzyme and BRCA-deficient cells, especially for the BRCA1-deficient MDA-MB-436 cells (CC50< 0.26nM). Mechanistic studies revealed that the new PARP1 inhibitors significantlyinhibited H2O2-triggered PARylation in SKOV3cells, induced cellular accumulation of DNA double-strand breaks,and impaired cell-cycle progression in BRCA2-deficientcells. Significant potentiation on the cytotoxicity of Temozolomidewas also observed. The unique structural character and exceptionallyhigh potency of 41made it stand out as a promising drugcandidate worthy for further evaluation. [ABSTRACT FROM AUTHOR]