Dual-Specificity Phosphatase CDC25B Was Inhibited by Natural Product HB-21 Through Covalently Binding to the Active Site

Centrosomes and associated proteins in pathogenesis and treatment of breast cancer

Breast cancer is the most prevalent malignancy among women worldwide. Despite significant advances in treatment, it remains one of the leading causes of female mortality. The inability to effectively treat advanced and/or treatment-resistant breast cancer demonstrates the need to develop novel treatment strategies and targeted therapies. Centrosomes and their associated proteins have been shown to play key roles in the pathogenesis of breast cancer and thus represent promising targets for drug and biomarker development. Centrosomes are fundamental cellular structures in the mammalian cell that are responsible for error-free execution of cell division. Centrosome amplification and aberrant expression of its associated proteins such as Polo-like kinases (PLKs), Aurora kinases (AURKs) and Cyclin-dependent kinases (CDKs) have been observed in various cancers, including breast cancer. These aberrations in breast cancer are thought to cause improper chromosomal segregation during mitosis, leading to chromosomal instability and uncontrolled cell division, allowing cancer cells to acquire new genetic changes that result in evasion of cell death and the promotion of tumor formation. Various chemical compounds developed against PLKs and AURKs have shown meaningful antitumorigenic effects in breast cancer cells in vitro and in vivo. The mechanism of action of these inhibitors is likely related to exacerbation of numerical genomic instability, such as aneuploidy or polyploidy. Furthermore, growing evidence demonstrates enhanced antitumorigenic effects when inhibitors specific to centrosome-associated proteins are used in combination with either radiation or chemotherapy drugs in breast cancer. This review focuses on the current knowledge regarding the roles of centrosome and centrosome-associated proteins in breast cancer pathogenesis and their utility as novel targets for breast cancer treatment.

Molecular Docking Analysis of Selected Urtica dioica Constituents As Human Carbonic Anhydrase II (hCA-II), Human 11 Beta-Hydroxysteroid Dehydrogenases Type 1 (h11beta-HSD1), and Human Dual Specificity Phosphatase (hCDC25B) Inhibitory Agents

Background Urtica dioica (Stinging nettle)has been reported to exhibit various pharmacological activities. In the present study, we aimed to evaluate 24 selected constituents of U. dioica as potent inhibitory agents of human carbonic anhydrase II (hCA-II), human 11 beta-hydroxysteroid dehydrogenases type 1 (h11beta-HSD1), and human dual specificity phosphatase (hCDC25B) using in silico method. Methodology The 24 selected constituents of U. dioica (Stinging nettle) were studied on the docking behavior of hCA-II, h11beta-HSD1, and hCDC25B by using the Webina docking method. In addition to docking, toxicity analysis was also performed using the pkCSM free web server, respectively. Results Toxicity analysis has shown that six ligands (25%) of U. dioica (Stinging nettle) are predicted to have hERG II (Human ether-a-go-go-related gene) inhibition activity. The docking analysis showed that afzelin, stigmastane-3, 6-diol, and astragalin of U. dioica have shown the maximum binding energy (-7.2, -9.5, and -8.5 kcal/mol) with the hCA-II, h11beta-HSD1 and hCDC25B, respectively. Conclusions Thus, the current finding provides new knowledge about the 24 selected ligands of U. dioica (Stinging nettle) as potent inhibitory agents of human carbonic anhydrase II (hCA-II), human 11 beta-hydroxysteroid dehydrogenases type 1 (h11beta-HSD1) and human dual specificity phosphatase (hCDC25B).

1,3,4-Oxadiazole Contained Sesquiterpene Derivatives: Synthesis and Microbiocidal Activity for Plant Disease

A series of 1,3,4-oxadiazole contained sesquiterpene derivatives were synthesized, and the activity of the target compounds against Xanthomonas oryzae pv. oryzae (Xoo), Xanthomonas axonopodis pv. citri (Xac), and tobacco mosaic virus (TMV) were evaluated. The biological activity results showed that the EC₅₀ values of compounds H4, H8, H11, H12, H14, H16, and H19 for Xac inhibitory activity were 33.3, 42.7, 56.1, 74.5, 37.8, 43.8, and 38.4 μg/ml, respectively. Compounds H4, H8, H15, H19, H22, and H23 had inhibitory effects on Xoo, with EC₅₀ values of 51.0, 43.3, 43.4, 50.5, 74.6, and 51.4 μg/ml, respectively. In particular, the curative and protective activities of compound H8 against Xoo in vivo were 51.9 and 49.3%, respectively. In addition, the EC₅₀ values of the inactivation activity of compounds H4, H5, H9, H10, and H16 against TMV were 69.6, 58.9, 69.4, 43.9, and 60.5 μg/ml, respectively. The results of molecular docking indicated that compound H10 exhibited a strong affinity for TMV-coat protein, with a binding energy of −8.88 kcal/mol. It may inhibit the self-assembly and replication of TMV particles and have an anti-TMV effect, which supports its potential usefulness as an antiviral agent.

Molecular dynamics study of CDC25BR492L mutant causing the activity decrease of CDC25B

Cell division cycle 25B (CDC25B) was responsible for regulating the various stages of cell division in the cell cycle. R492L was one of the common types of CDC25B mutants. Researches showed that compared to CDC25B^WT, CDC25B^R492L mutant had a ∼100-fold reduction in the rate constant for forming phosphatase intermediate (k₂). However, the molecular basis of how the CDC25B^R492L mutant influenced the process of binding between CDC25B and CDK2/CyclinA was not yet known. Therefore, the optimizations of three-dimensional structure of the CDC25B^WT-CDK2/CyclinA system and the CDC25B^R492L-CDK2/CyclinA system were constructed by ZDOCK and RDOCK, and five methods were employed to verify the reasonability of the docking structure. Then the molecular dynamics simulations on the two systems were performed to explore the reason why CDC25B^R492L mutant caused the weak interactions between CDC25B^R492L and CDK2/CyclinA, respectively. The remote docking site (Arg488-Tyr497) and the second active site (Lys538-Arg544) of CDC25B were observed to have high fluctuations in the CDC25B^R492L-CDK2/CyclinA system with post-analysis, where the high fluctuation of these two regions resulted in weak interactions between CD25B and CDK2. In addition, Asp38-Glu42 and Asp206-Asp210 of CDK2 showed the slightly descending fluctuation, and CDK2 revealed an enhanced the self-interaction, which made CDK2 keep a relatively stable state in the CDC25B^R492L-CDK2/CyclinA system. Finally, Leu492 of CDC25B was speculated to be the key residue, which had great effects on the binding between CDC25B^R492L and CDK2 in the CDC25B^R492L-CDK2/CyclinA system. Consequently, overall analyses appeared in this study ultimately offered a helpful understanding of the weak interactions between CDC25B^R492L and CDK2.

In Silico Identification of Small Molecules as New Cdc25 Inhibitors through the Correlation between Chemosensitivity and Protein Expression Pattern

The cell division cycle 25 (Cdc25) protein family plays a crucial role in controlling cell proliferation, making it an excellent target for cancer therapy. In this work, a set of small molecules were identified as Cdc25 modulators by applying a mixed ligand-structure-based approach and taking advantage of the correlation between the chemosensitivity of selected structures and the protein expression pattern of the proposed target. In the first step of the in silico protocol, a set of molecules acting as Cdc25 inhibitors were identified through a new ligand-based protocol and the evaluation of a large database of molecular structures. Subsequently, induced-fit docking (IFD) studies allowed us to further reduce the number of compounds biologically screened. In vitro antiproliferative and enzymatic inhibition assays on the selected compounds led to the identification of new structurally heterogeneous inhibitors of Cdc25 proteins. Among them, J3955, the most active inhibitor, showed concentration-dependent antiproliferative activity against HepG2 cells, with GI₅₀ in the low micromolar range. When J3955 was tested in cell-cycle perturbation experiments, it caused mitotic failure by G2/M-phase cell-cycle arrest. Finally, Western blotting analysis showed an increment of phosphorylated Cdk1 levels in cells exposed to J3955, indicating its specific influence in cellular pathways involving Cdc25 proteins.

Mechanism of protein-guided folding of the active site U2/U6 RNA during spliceosome activation

Spliceosome activation involves extensive protein and RNA rearrangements that lead to formation of a catalytically active U2/U6 RNA structure. At present, little is known about the assembly pathway of the latter and the mechanism whereby proteins aid its proper folding. Here, we report the cryo-electron microscopy structures of two human, activated spliceosome precursors (that is, pre-B^act complexes) at core resolutions of 3.9 and 4.2 angstroms. These structures elucidate the order of the numerous protein exchanges that occur during activation, the mutually exclusive interactions that ensure the correct order of ribonucleoprotein rearrangements needed to form the U2/U6 catalytic RNA, and the stepwise folding pathway of the latter. Structural comparisons with mature B^act complexes reveal the molecular mechanism whereby a conformational change in the scaffold protein PRP8 facilitates final three-dimensional folding of the U2/U6 catalytic RNA.

Medicinal chemistry insights into novel CDC25 inhibitors

Cell division cycle 25 (CDC25) phosphatases, a kind of cell cycle regulators, have become an attractive target for drug discovery, as they have been found to be over-expressed in various human cancer cells. Several CDC25 inhibitors have achieved significant attention in clinical trials with possible mechanistic actions. Prompted by the significance of CDC25 inhibitors with medicinal chemistry prospect, it is an apt time to review the various drug discovery methods involved in CDC25 drug discovery including high throughput screening (HTS), virtual screening (VS), fragment-based drug design, substitution decorating approach, structural simplification approach and scaffold hopping method to seek trends and identify promising new avenues of CDC25 drug discovery.