Thienoquinolines as novel disruptors of the PKCε/RACK2 protein-protein interaction

Chemistry of Thieno [2,3-h]-/[3,2-h] Quinoline and Thieno [2,3-f]-/[3,2-f] Quinoline Derivatives Part (x), Reactivities, and Biological Activities

Abstract:

Several thieno [2,3-h] /[3,2-h] quinolines and thieno [2,3-f] /[3,2-f] quinolines (TQs) are discussed in this review from a few perspectives, including various preparation and processing methods employing cutting-edge machinery. The preparation of (TQs), from 4-(5)aminobenzothiophene, 2(3)chloromethylthiophene, 2(3)thienylboric acid, and other chemical reagents is illustrated via a number of chemical procedures in this review. The formation of (TQs) was clarified using the Michael addition, Photocyclization, Skraup reaction, Ullmann-Fetvadjian process, Suzuki-Miyaura and Sonogashira reaction, aza-Diels-Alder reaction, and Friedel-Crafts reaction.

PKCε inhibition prevents ischemia‑induced dendritic spine impairment in cultured primary neurons

Brain ischemia is an independent risk factor for Alzheimer's disease (AD); however, the mechanisms underlining ischemic stroke and AD remain unclear. The present study aimed to investigate the function of the ε isoform of protein kinase C (PKCε) in brain ischemia-induced dendritic spine dysfunction to elucidate how brain ischemia causes AD. In the present study, primary hippocampus and cortical neurons were cultured while an oxygen-glucose deprivation (OGD) model was used to simulate brain ischemia. In the OGD cell model, in vitro kinase activity assay was performed to investigate whether the PKCε kinase activity changed after OGD treatment. Confocal microscopy was performed to investigate whether inhibiting PKCε kinase activity protects dendritic spine morphology and function. G-LISA was used to investigate whether small GTPases worked downstream of PKCε. The results showed that PKCε kinase activity was significantly increased following OGD treatment in primary neurons, leading to dendritic spine dysfunction. Pre-treatment with PKCε-inhibiting peptide, which blocks PKCε activity, significantly rescued dendritic spine function following OGD treatment. Furthermore, PKCε could activate Ras homolog gene family member A (RhoA) as a downstream molecule, which mediated OGD-induced dendritic spine morphology changes and caused dendritic spine dysfunction. In conclusion, the present study demonstrated that the PKCε/RhoA signalling pathway is a novel mechanism mediating brain ischemia-induced dendritic spine dysfunction. Developing therapeutic targets for this pathway may protect against and prevent brain ischemia-induced cognitive impairment and AD.

Access to Thienopyridine and Thienoquinoline Derivatives via Site-Selective C-H Bond Functionalization and Annulation

To develop of an effective synthetic methodology for biologically relevant thienopyridines, a concise and efficient protocol is described for the synthesis of a series of substituted thienopyridine and thienoquinoline derivatives with high selectivity using EtOCS₂K as the sulfur source. The reaction proceeds via metal-free, site-selective C-H bond thiolation and cyclization of the alkynylpyridine and alkynylquinoline substrates.

Mo-Catalyzed One-Pot Synthesis of N-Polyheterocycles from Nitroarenes and Glycols with Recycling of the Waste Reduction Byproduct. Substituent-Tuned Photophysical Properties

A catalytic domino reduction-imine formation-intramolecular cyclization-oxidation for the general synthesis of a wide variety of biologically relevant N-polyheterocycles, such as quinoxaline- and quinoline-fused derivatives, and phenanthridines, is reported. A simple, easily available, and environmentally friendly dioxomolybdenum(VI) complex has proven to be a highly efficient and versatile catalyst for transforming a broad range of starting nitroarenes involving several redox processes. Not only is this a sustainable, step-economical as well as air- and moisture-tolerant method, but also it is worth highlighting that the waste byproduct generated in the first step of the sequence is recycled and incorporated in the final target molecule, improving the overall synthetic efficiency. Moreover, selected indoloquinoxalines have been photophysically characterized in cyclohexane and toluene with exceptional fluorescence quantum yields above 0.7 for the alkyl derivatives.

Targeting Kinase Interaction Networks: A New Paradigm in PPI Based Design of Kinase Inhibitors

BACKGROUND

Kinases are key modulators in regulating diverse range of cellular activities and are an essential part of the protein-protein interactome. Understanding the interaction of kinases with different substrates and other proteins is vital to decode the cell signaling machinery as well as causative mechanism for disease onset and progression.

OBJECTIVE

The objective of this review is to present all studies on the structure and function of few important kinases and highlight the protein-protein interaction (PPI) mechanism of kinases and the kinase specific interactome databases and how such studies could be utilized to develop anticancer drugs.

METHODS

The article is a review of the detailed description of the various domains in kinases that are involved in protein-protein interactions and specific inhibitors developed targeting these PPI domains.

RESULTS

The review has surfaced in depth the interacting domains in key kinases and their features and the roles of PPI in the human kinome and the various signaling cascades that are involved in certain types of cancer.

CONCLUSION

The insight availed into the mechanism of existing peptide inhibitors and peptidomimetics against kinases will pave way for the design and generation of domain specific peptide inhibitors with better productivity and efficiency and the various software and servers available can be of great use for the identification and analysis of protein-protein interactions.

Drug Repositioning Inferred from E2F1-Coregulator Interactions Studies for the Prevention and Treatment of Metastatic Cancers

Metastasis management remains a long-standing challenge. High abundance of E2F1 triggers tumor progression by developing protein-protein interactions (PPI) with coregulators that enhance its potential to activate a network of prometastatic transcriptional targets.

Methods: To identify E2F1-coregulators, we integrated high-throughput Co-immunoprecipitation (IP)/mass spectometry, GST-pull-down assays, and structure modeling. Potential inhibitors of PPI discovered were found by bioinformatics-based pharmacophore modeling, and transcriptome profiling was conducted to screen for coregulated downstream targets. Expression and target gene regulation was validated using qRT-PCR, immunoblotting, chromatin IP, and luciferase assays. Finally, the impact of the E2F1-coregulator complex and its inhibiting drug on metastasis was investigated in vitro in different cancer entities and two mouse metastasis models.

Results: We unveiled that E2F1 forms coactivator complexes with metastasis-associated protein 1 (MTA1) which, in turn, is directly upregulated by E2F1. The E2F1:MTA1 complex potentiates hyaluronan synthase 2 (HAS2) expression, increases hyaluronan production and promotes cell motility. Disruption of this prometastatic E2F1:MTA1 interaction reduces hyaluronan synthesis and infiltration of tumor-associated macrophages in the tumor microenvironment, thereby suppressing metastasis. We further demonstrate that E2F1:MTA1 assembly is abrogated by small-molecule, FDA-approved drugs. Treatment of E2F1/MTA1-positive, highly aggressive, circulating melanoma cells and orthotopic pancreatic tumors with argatroban prevents metastasis and cancer relapses in vivo through perturbation of the E2F1:MTA1/HAS2 axis.

Conclusion: Our results propose argatroban as an innovative, E2F-coregulator-based, antimetastatic drug. Cancer patients with the infaust E2F1/MTA1/HAS2 signature will likely benefit from drug repositioning.

Oxidative stress associated with aging activates protein kinase Cε, leading to cilia slowing

Older people are four times more likely to develop pneumonia than younger people. As we age, many components of pulmonary innate immunity are impaired, including slowing of mucociliary clearance. Ciliary beat frequency (CBF) is a major determinant of mucociliary clearance, and it slows as we age. We hypothesized that CBF is slowed in aging because of increased oxidative stress, which activates PKCε signaling. We pharmacologically inhibited PKCε in ex vivo mouse models of aging. We measured a slowing of CBF with aging that was reversed with inhibition using the novel PKC inhibitor, Ro-31-8220, as well as the PKCε inhibitor, PKCe141. Inhibition of PKCε using siRNA in mouse trachea also returned CBF to normal. In addition, antioxidants decrease PKCε activity and speed cilia. We also aged wild-type and PKCε KO mice and measured CBF. The PKCε KO mice were spared from the CBF slowing of aging. Using human airway epithelial cells from younger and older donors at air-liquid interface (ALI), we inhibited PKCε with siRNA. We measured a slowing of CBF with aging that was reversed with siRNA inhibition of PKCε. In addition, we measured bead clearance speeds in human ALI, which demonstrated a decrease in bead velocity with aging and a return to baseline after inhibition of PKCε. In summary, in human and mouse models, aging is associated with increased oxidant stress, which activates PKCε and slows CBF.

Characterisation of peptide interactions that regulate PKCε activation

Targeting the interaction between PKC isoforms and their anchoring proteins can specifically regulate kinase activity. εV1-2 and pseudoεRACK peptides, derived from the PKCε C2 domain, modulate its association with receptor for activated C-kinase 2 (RACK2) and thus its function. Details of these interactions remain obscure, and we therefore investigated binding of these peptides using biophysical techniques. Surface plasmon resonance (SPR) indicated that the inhibitory εV1-2 peptide bound to RACK2, and inhibited PKCε binding as expected. In contrast, SPR and NMR demonstrated that the activating pseudoεRACK peptide and related sequences did not bind to PKCε, indicating that their mechanisms of action do not involve binding to the kinase as previously proposed. Our results clarify which interactions could be targeted in developing new therapeutics that inhibit PKCε-RACK2 interaction.

Design, synthesis and anticancer studies of novel aminobenzazolyl pyrimidines as tyrosine kinase inhibitors

Abnormal signalling from the Protein tyrosine kinases (PTKs) like receptor tyrosine kinases and intracellular tyrosine kinases can lead to diseases such as cancer especially non-small cell lung cancer, chronic myeloid leukaemia and gastrointestinal stromal tumours. Various Protein tyrosine kinase inhibitors are available but face poor bioavailability, severe toxicities and recent cases of drug-resistant cancers prompts for development of better drug molecules. In this study we report the design and development of a novel Protein Tyrosine Kinase (PTK) inhibitor on the basis of pharmacophore modelling. Compound 2-(benzo[d]oxazol-2-ylamino)-N-(2-chloro-4-fluorophenyl)-4-methyl-6-(3-nitrophenyl) pyrimidine-5-carboxamide 31 was obtained containing essential pharmacophore structural features. This compound exhibited highest activity against leukaemia cell line (RPMI-8226) at 0.7244 µM, renal cancer cell line (A498) at 0.8511 µM and prostate cancer cell line (PC-3) at 0.7932 µM on the NCI five dose assay test. The PTK assay provides promising activity at IC₅₀ of 0.07 µM in the human breast cancer cell line MDA-MB-468. Compound 31 had good intermolecular interaction with PTK in the molecular docking studies, this ligand-enzyme complex was found to stable in the MM-PBSA study over 100 ns. It had 54.22% oral bioavailability with T_max of 0.60 h which is higher compared to the dasatinib with bioavailability and T_max of 14-34% and 1-1.42 h respectively. Anticancer action of 31 was found to be impressive in pharmacokinetic studies making it a potential lead molecule.

Synthesis and anti-tubercular activity of fused thieno-/furo-quinoline compounds

Simple two step synthesis of fused thieno-/furo-quinoline (or [1,8]-naphthyridine) compounds by sequential application of Suzuki coupling and modified Pictet–Spengler synthesis.

State-of-the-art strategies for targeting protein-protein interactions by small-molecule inhibitors

Targeting protein-protein interactions (PPIs) has emerged as a viable approach in modern drug discovery. However, the identification of small molecules enabling us to effectively interrupt their interactions presents significant challenges. In the recent past, significant advances have been made in the development of new biological and chemical strategies to facilitate the discovery process of small-molecule PPI inhibitors. This review aims to highlight the state-of-the-art technologies and the achievements made recently in this field. The "hot spots" of PPIs have been proved to be critical for small molecules to bind. Three strategies including screening, designing, and synthetic approaches have been explored for discovering PPI inhibitors by targeting the "hot spots". Although the classic high throughput screening approach can be used, fragment screening, fragment-based drug design and newly improved virtual screening are demonstrated to be more effective in the discovery of PPI inhibitors. In addition to screening approaches, design strategies including anchor-based and small molecule mimetics of secondary structures involved in PPIs have become powerful tools as well. Finally, constructing new chemically spaced libraries with high diversity and complexity is becoming an important area of interest for PPI inhibitors. The successful cases from the recent five year studies are used to illustrate how these approaches are implemented to uncover and optimize small molecule PPI inhibitors and notably some of them have become promising therapeutics.

Hierarchical virtual screening approaches in small molecule drug discovery

Virtual screening has played a significant role in the discovery of small molecule inhibitors of therapeutic targets in last two decades. Various ligand and structure-based virtual screening approaches are employed to identify small molecule ligands for proteins of interest. These approaches are often combined in either hierarchical or parallel manner to take advantage of the strength and avoid the limitations associated with individual methods. Hierarchical combination of ligand and structure-based virtual screening approaches has received noteworthy success in numerous drug discovery campaigns. In hierarchical virtual screening, several filters using ligand and structure-based approaches are sequentially applied to reduce a large screening library to a number small enough for experimental testing. In this review, we focus on different hierarchical virtual screening strategies and their application in the discovery of small molecule modulators of important drug targets. Several virtual screening studies are discussed to demonstrate the successful application of hierarchical virtual screening in small molecule drug discovery.

Rational design of protein–protein interaction inhibitors

Low molecular weight compound competing for the binding of the p53 tumor suppressor to the MDM2 oncoprotein.