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A novel inhibitor of human La protein with anti-HBV activity discovered by structure-based virtual screening and in vitro evaluation.

ABSTRACT: BACKGROUND: Over 350 million people worldwide are infected with hepatitis B virus (HBV), a major cause of liver failure and hepatocellular carcinoma. Current therapeutic agents are highly effective, but are also associated with development of viral resistance. Therefore, strategies for identifying other anti-HBV agents with specific, but distinctive mechanisms of action are needed. The human La (hLa) protein, which forms a stabilizing complex with HBV RNA ribonucleoprotein to promote HBV replication, is a promising target of molecular therapy. AIMS: This study aimed to discover novel inhibitors of hLa that could inhibit HBV replication and expression. METHODS: A multistage molecular docking approach was used to screen a Specs database and an in-house library against hLa binding sites. Sequential in vitro evaluations were performed to detect potential compounds with high scores in HepG2.2.15 cells. RESULTS: Of the 26 potential compounds with high scores chosen for experimental verification, 12 had HBV DNA inhibition ratios of less than 50% with P<0.05. Six had significant inhibition of HBV e antigen (HBeAg) levels, and 13 had significant inhibition of HBV surface antigen (HBsAg) levels by in vitro assays. Compounds HBSC-11, HBSC-15 and HBSC-34 (HBSC is system prefix for active compounds screened by the library) were selected for evaluation. HBSC-11 was found to have an obvious inhibitory effect on hLa transcription and expression. CONCLUSIONS: Our findings suggest that anti-HBV activity of HBSC-11 may be mediated by a reduction in hLa levels. In addition, our data suggest the potential clinical use of hLa inhibitors, such as HBSC-11, for treating HBV infection.

SUBMITTER: Tang J

PROVIDER: S-EPMC3338670 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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A novel inhibitor of human La protein with anti-HBV activity discovered by structure-based virtual screening and in vitro evaluation.

Tang Jing J Huang Zhi-Min ZM Chen Ying-Yi YY Zhang Zhao-Hui ZH Liu Gao-Lin GL Zhang Jian J

PloS one 20120427 4

<h4>Background</h4>Over 350 million people worldwide are infected with hepatitis B virus (HBV), a major cause of liver failure and hepatocellular carcinoma. Current therapeutic agents are highly effective, but are also associated with development of viral resistance. Therefore, strategies for identifying other anti-HBV agents with specific, but distinctive mechanisms of action are needed. The human La (hLa) protein, which forms a stabilizing complex with HBV RNA ribonucleoprotein to promote HBV ...[more]

PMID: 22558448

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Project description:In the past decade, the spleen tyrosine kinase (Syk) has shown a high potential for the discovery of new treatments for inflammatory and autoimmune disorders. Pharmacological inhibitors of Syk catalytic site bearing therapeutic potential have been developed, with however limited specificity towards Syk. To address this topic, we opted for the design of drug-like compounds that could impede the interaction of Syk with its cellular partners while maintaining an active kinase protein. To achieve this challenging task, we used the powerful potential of intracellular antibodies for the modulation of cellular functions in vivo, combined to structure-based in silico screening. In our previous studies, we reported the anti-allergic properties of the intracellular antibody G4G11. With the aim of finding functional mimics of G4G11, we developed an Antibody Displacement Assay and we isolated the drug-like compound C-13, with promising in vivo anti-allergic activity. The likely binding cavity of this compound is located at the close vicinity of G4G11 epitope, far away from the catalytic site of Syk. Here we report the virtual screen of a collection of 500,000 molecules against this new cavity, which led to the isolation of 1000 compounds subsequently evaluated for their in vitro inhibitory effects using the Antibody Displacement Assay. Eighty five compounds were selected and evaluated for their ability to inhibit the liberation of allergic mediators from mast cells. Among them, 10 compounds inhibited degranulation with IC?? values ? 10 µM. The most bioactive compounds combine biological activity, significant inhibition of antibody binding and strong affinity for Syk. Moreover, these molecules show a good potential for oral bioavailability and are not kinase catalytic site inhibitors. These bioactive compounds could be used as starting points for the development of new classes of non-enzymatic inhibitors of Syk and for drug discovery endeavour in the field of inflammation related disorders.

Project description:A multi-step cascade strategy using integrated ligand- and target-based virtual screening methods was developed to select a small number of compounds from the ZINC database to be evaluated for trypanocidal activity. Winnowing the database to 23 selected compounds, 12 non-covalent binding cruzain inhibitors with affinity values (K i) in the low micromolar range (3-60 µM) acting through a competitive inhibition mechanism were identified. This mechanism has been confirmed by determining the binding mode of the cruzain inhibitor Nequimed176 through X-ray crystallographic studies. Cruzain, a validated therapeutic target for new chemotherapy for Chagas disease, also shares high similarity with the mammalian homolog cathepsin L. Because increased activity of cathepsin L is related to invasive properties and has been linked to metastatic cancer cells, cruzain inhibitors from the same library were assayed against it. Affinity values were in a similar range (4-80 µM), yielding poor selectivity towards cruzain but raising the possibility of investigating such inhibitors for their effect on cell proliferation. In order to select the most promising enzyme inhibitors retaining trypanocidal activity for structure-activity relationship (SAR) studies, the most potent cruzain inhibitors were assayed against T. cruzi-infected cells. Two compounds were found to have trypanocidal activity. Using compound Nequimed42 as precursor, an SAR was established in which the 2-acetamidothiophene-3-carboxamide group was identified as essential for enzyme and parasite inhibition activities. The IC50 value for compound Nequimed42 acting against the trypomastigote form of the Tulahuen lacZ strain was found to be 10.6±0.1 µM, tenfold lower than that obtained for benznidazole, which was taken as positive control. In addition, by employing the strategy of molecular simplification, a smaller compound derived from Nequimed42 with a ligand efficiency (LE) of 0.33 kcal mol(-1) atom(-1) (compound Nequimed176) is highlighted as a novel non-peptidic, non-covalent cruzain inhibitor as a trypanocidal agent candidate for optimization.

Project description:AimTo discover novel ligands of estrogen receptor (ER) β using pharmacophore mapping and structure-based screening.MethodsA computer-aided strategy combining pharmacophore mapping and structure-based screening was used to screen the Maybridge and Enamine databases. Yeast two-hybrid (Y2H) assay was used to detect the activity and selectivity of the chosen compounds. The transcriptional activities of the chosen compounds were demonstrated with luciferase reporter assays. The anti-proliferative effects of ER antagonists against MCF-7 and MDA-MB-231 breast cancer cells were examined using MTT assay, and the mechanisms of action were analyzed with flow cytometry analysis and Western blotting.ResultsThrough in silico screen, 95 compounds were chosen for testing in Y2H assay, which led to 20 potent ligands, including 10 agonists, 8 antagonists and 2 partial agonists with EC50 or IC50 values at μmol/L. Furthermore, 6 agonists exhibited absolute selectivity for ERβ, and 3 agonists showed higher selectivity for ERβ. The agonists 1g and 1h (10, 25, and 50 μmol/L) dose-dependently increased ER transcriptional activities, whereas the antagonists 2a and 2d (10, 25, and 50 μmol/L) caused dose-dependent inhibition on the activities. The antagonists and partial agonists at 100 μmol/L suppressed the proliferation of ERα positive MCF-7 cells and ERβ positive MDA-MB-231 cells, but were more effective against MDA-MB-231 cells. Treatment of MDA-MB-231 cells with antagonists 2a and 2d (25 and 50 μmol/L) dose-dependently increased the population of cells in the S phase. Both 2a and 2d treatment dose-dependently decreased the expression levels of cyclin A and CDK2. Meanwhile, the downregulation of cyclin E was only caused by 2d, while 2a treatment did not cause significant changes in the protein levels of cyclin E.ConclusionThe selective ligands discovered in this study are promising drug candidates to be used as molecular probes to explore the differences between ERα and ERβ.

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A novel inhibitor of human La protein with anti-HBV activity discovered by structure-based virtual screening and in vitro evaluation.

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A novel inhibitor of human La protein with anti-HBV activity discovered by structure-based virtual screening and in vitro evaluation.

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