Pyrimidinone-peptoid hybrid molecules with distinct effects on molecular chaperone function and cell proliferation

Computational Screening of Natural Compounds for Identification of Potential Anti-Cancer Agents Targeting MCM7 Protein

Minichromosome maintenance complex component 7 (MCM7) is involved in replicative licensing and the synthesis of DNA, and its overexpression is a fascinating biomarker for various cancer types. There is currently no effective agent that can prevent the development of cancer caused by the MCM7 protein. However, on the molecular level, inhibiting MCM7 lowers cancer-related cellular growth. With this purpose, this study screened 452 biogenic compounds extracted from the UEFS Natural Products dataset against MCM protein by using the in silico art of technique. The hit compounds UEFS99, UEFS137, and UEFS428 showed good binding with the MCM7 protein with binding energy values of −9.95, −8.92, and −8.71 kcal/mol, which was comparatively higher than that of the control compound ciprofloxacin (−6.50). The hit (UEFS99) with the minimum binding energy was picked for molecular dynamics (MD) simulation investigation, and it demonstrated stability at 30 ns. Computational prediction of physicochemical property evaluation revealed that these hits are non-toxic and have good drug-likeness features. It is suggested that hit compounds UEFS99, UEFS137, and UEFS428 pave the way for further bench work validation in novel inhibitor development against MCM7 to fight the cancers.

Synthesis, crystal structure and antibacterial studies of dihydropyrimidines and their regioselectively oxidized products

The syntheses and investigations of new biologically active derivatives of dihydropyrimidines by Biginelli reaction in the presence of copper triflate are reported. Due to the fact that salicylaldehyde and its derivatives under Biginelli reaction conditions can lead to the formation of 2 types of dihydropyrimidines, the influence of copper triflate on product formation was also investigated. In addition to this, regioselective oxidation of dihydropyrimidines was performed in the presence of cerium ammonium nitrate and novel oxidized dihydropyrimidines were obtained. Single crystals of some of them were obtained and as a result, the structures of them were investigated by X-ray diffraction method, which allows determining the presence of hydrogen bonds in their structures. In addition to this, the presence of hydrogen bonds in their structures affects the formation of the corresponding tautomer during oxidizing of dihydropyrimidines. Since dihydropyrimidines are claimed to be biologically active compounds, activities of the synthesized compounds were studied against Acinetobacter baumanii, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae and Staphylococcus aureus bacteria.

Antiproliferative effect, alteration of cancer cell cycle progression and potential MET kinase inhibition induced by 3,4-dihydropyrimidin-2(1H)-one C5 amide derivatives

Cancer continues to be the second leading cause of death worldwide. Discovery of novel therapeutic agents has crucial importance for improvement of our medical management capabilities. Dysregulation of the MET receptor tyrosine kinase pathway plays an important role in cancer progression, making this receptor an attractive molecular target for anticancer drug discovery. In this study, twenty-seven 3,4-dihydropyrimidin-2(1H)-one C5 amide derivatives were synthesized and their cancer cell growth inhibitory activity was examined against MCF-7, HT-29 and MOLT-4 cells and also NIH/3T3 non-cancer cells by MTT assay. The antiproliferative effect of the most potent derivatives were tested against MET-dependent EBC-1 and MKN-45, lung and gastric cancer cell lines, respectively. MET kinase inhibition was measured by a Homogenous Time Resolved Fluorescence (HTRF) Assay. The influence of the test compounds on cell cycle was examined by RNase/PI flow cytometric assay. A number of compounds exhibited considerable antiproliferative effects against breast and colon cancer and leukemia cell lines, relatively sparing non-cancer cells. Some derivatives bearing benzothiazolyl carboxamide moiety at C5 position (15, 21, 23, 31, and 37) showed the highest activities with IC₅₀ values as low as 10.9 μM. These compounds showed antiproliferative effects also against MET-amplified cells and dose-dependently inhibited MET kinase activity. They also induced G0/G1 cell cycle arrest at lower doses and apoptosis at higher doses. Molecular docking and dynamics simulation studies confirmed the interaction of compound 23 with the active site of the MET receptor. These findings demonstrate that 3,4-dihydropyrimidin-2(1H)-one analogues may represent promising targeted anticancer agents.

Dihydropyrimidinones Scaffold as a Promising Nucleus for Synthetic Profile and Various Therapeutic Targets: A Review

BACKGROUND

This review elaborates the updated synthetic and pharmacological approaches of a known group of dihydropyrimidinones/thiones from the multi-component reaction like Biginelli reaction, which was named Pietro Biginelli in 1891. This review consists of the reaction of an aromatic aldehyde, urea and ethyl acetoacetate leading to dihydropyrimidinone/thione. Currently, the scientific movement to develop economically viable green methods using compounds that are reusable, non-volatile, easily obtained, etc. Objective: This review covers the recent synthesis and pharmacological advancement of dihydropyrimidinones/ thiones moiety, along with covering the structure-activity relationship of the most potent compounds, which may prove to become better, more efficacious and safer agents. Thus, this review may help the researchers in drug designing and development of new Dihydropyrimidinones entities.

CONCLUSION

This review focuses on the wide application of dihydropyrimidinone/thione review reports the design, synthesis and pharmacological activities of nitrogen-sulphur containing dihydropyrimidinone moiety by using multi-component reaction. Dihydropyrimidinones (DHPM) pharmacophore is an important heterocyclic ring in medicinal chemistry. It is derived from multi-component reactions, "Biginelli reaction" and plays a critical role as anticancer, antioxidant, antimicrobial, anti-inflammatory, anti-HIV-1, antimalarial, anti-inflammatory, antihypertensive and anti-tubercular agents. Exhaustive research has led to its vast biological profile, with a wide range of therapeutic application.

Dihydropyrimidinones: efficient one-pot green synthesis using Montmorillonite-KSF and evaluation of their cytotoxic activity

A simple, efficient, cost-effective, recyclable and green approach has been developed for the synthesis of new dihydropyrimidinone analogs via the Biginelli reaction. The methodology involves a multicomponent reaction catalyzed by “HPA-Montmorillonite-KSF” as a reusable and heterogeneous catalyst. This method gives an efficient and much improved modification of the original Biginelli reaction, in terms of yield and short reaction times under solvent free conditions. All the derivatives were subjected to cytotoxicity screening against a panel of four different human cancer cell lines viz. colon (Colo-205), prostate (PC-3), leukemia (THP-1) and lung (A549) to check their effect on percentage growth. MTT [3-(4,5-dimethylthiazol-yl)-diphenyl tetrazoliumbromide] cytotoxicity assay was employed to check IC₅₀ values. Of the synthesized analogs, 16a showed the best activity with IC₅₀ of 7.1 ± 0.8, 13.1 ± 1.4, 13.8 ± 0.9 and 14.7 ± 1.1 μM against lung (A549), leukemia (THP-1), prostate (PC-3) and colon (Colo-205) cancer lines, respectively. The 16a analog was further checked for its effect on cancer cell properties through clonogenic (colony formation) and scratch motility (wound healing) assays and thereby was found that it reduced both the colony formation and migratory properties of the lung cancer cell line (A549). Further, molecular docking studies were performed with 16a to show its binding mode.

The general method for the preparation of DHPM analogs; cytotoxic activity and binding mode of the most active derivative against PI3Kγ and CDK2 targets.

Hsp70 and the Unfolded Protein Response as a Challenging Drug Target and an Inspiration for Probe Molecule Development

The unfolded protein response (UPR) is a cellular stress response mechanism that is critical for cell survival. Pharmacological modulation of the ATPase activity of the chaperone Hsp70 can trigger UPR-mediated cell death, thus removing pathogenic cells in human malignancies, or, alternatively, stimulate survival, thereby preventing apoptosis in neuronal cells and slowing the progress of inflammation, neurodegeneration, and aging. This Viewpoint highlights the complexity of the protein homeostasis network and discusses different approaches for modulating Hsp70 activity, including the use of a chemical reaction development-inspired library of Hsp70 agonists and antagonists.

Neutral analogs of the heat shock protein 70 (Hsp70) inhibitor, JG-98

The heat shock protein 70 (Hsp70) family of molecular chaperones are highly expressed in tumors. Inhibitors containing a pyridinium-modified benzothiazole, such as JG-98, bind to a conserved, allosteric site in Hsp70, showing promising anti-proliferative activity in cancer cells. When bound to Hsp70, the charged pyridinium makes favorable contacts; however, this moiety also increases the inhibitor's fluorescence, giving rise to undesirable interference in biochemical and cell-based assays. Here, we explore whether the pyridinium can be replaced with a neutral pyridine. We report that pyridine-modified benzothiazoles, such as compound 17h (JG2-38), have reduced fluorescence, yet retain promising anti-proliferative activity (EC₅₀ values ~0.1 to 0.07 µM) in breast and prostate cancer cell lines. These chemical probes are expected to be useful in exploring the roles of Hsp70s in tumorigenesis and cell survival.

Hsp70 inhibitors: Implications for the treatment of colorectal cancer

Colorectal cancer (CRC) is one of the most common malignancies in the world. Despite intensive advances in diagnosis and treatment of CRC, it is yet one of the leading cause of cancer related morbidity and mortality. Therefore, there is an urgent medical need for alternative therapeutic approaches to treat CRC. The 70 kDa heat shock proteins (Hsp70s) are a family of evolutionary conserved heat shock proteins, which play an important role in cell homeostasis and survival. They overexpress in various types of malignancy including CRC and are typically accompanied with poor prognosis. Hence, inhibition of Hsp70 may be considered as a striking chemotherapeutic avenue. This review summarizes the current knowledge on the progress made so far to discover compounds, which target the Hsp70 family, with particular emphasis on their efficacy in treatment of CRC. We also briefly explain the induction of Hsp70 as a strategy to prevent CRC.

Design, synthesis and evaluation of cytotoxic, antimicrobial, and anti-HIV-1 activities of new 1,2,3,4-tetrahydropyrimidine derivatives

A series of new 1,2,3,4-tetrahydropyrimidine (THPM) derivatives were designed and synthesized within a one-pot three component Biginelli reaction. The structures of compounds were characterized by FT-IR, 1HNMR, mass spectroscopy, and elemental analysis. All synthesized derivatives were screened for their cytotoxic, antimicrobial, and anti-HIV activities. Due to significant cytotoxic and antimicrobial effects of 1,2,3,4-THPM scaffold, in this study, cytotoxic and antimicrobial activities of synthesized derivatives were evaluated on two cell lines and four bacterial strains. Compounds 4e and 4k showed highest cytotoxic activity against HeLa and MCF-7 cell lines. In addition, 4c and 4d were most active against MCF-7 and HeLa cell lines, respectively. Among the compounds, 4e revealed high antimicrobial activity against four strains. According to the results, 4e possessing m-bromophenyl group at C-4 position of THPM exhibited the highest cytotoxic and antimicrobial effects. Also, all the newly synthesized compounds were evaluated for their anti-HIV-1 assay. Compounds 4l and 4a indicated remarkable anti-HIV-1 activity. It is concluded from cytotoxic, antimicrobial, and anti-HIV-1 activities that the 1,2,3,4-tertahydropyrimidines may serve as hit compounds for development of new anticancer small-molecules.

Synthesis and evaluation of esterified Hsp70 agonists in cellular models of protein aggregation and folding

Over-expression of the Hsp70 molecular chaperone prevents protein aggregation and ameliorates neurodegenerative disease phenotypes in model systems. We identified an Hsp70 activator, MAL1-271, that reduces α-synuclein aggregation in a Parkinson's Disease model. We now report that MAL1-271 directly increases the ATPase activity of a eukaryotic Hsp70. Next, twelve MAL1-271 derivatives were synthesized and examined in a refined α-synuclein aggregation model as well as in an assay that monitors maturation of a disease-causing Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) mutant, which is also linked to Hsp70 function. Compared to the control, MAL1-271 significantly increased the number of cells lacking α-synuclein inclusions and increased the steady-state levels of the CFTR mutant. We also found that a nitrile-containing MAL1-271 analog exhibited similar effects in both assays. None of the derivatives exhibited cellular toxicity at concentrations up to 100 μm, nor were cellular stress response pathways induced. These data serve as a gateway for the continued development of a new class of Hsp70 agonists with efficacy in these and potentially other disease models.

Chemistry and Pharmacological Activities of Biginelli Product- A Brief Overview

Dihydropyrimidinones are extremely advantageous small sized molecules owning adaptable pharmaceutical properties. With a molecular formula C₄H₆N₂O, they hold a wide range of biological activities. It is a heterocyclic moiety having two N-atoms at positions 1 and 3. They are derivatives of pyrimidine containing an additional ketone group. They have inspired development of a wide range of synthetic methods for preparation and chemical transformations. Taking into consideration their structural similarity and involvement with DNA and RNA, they have become very imperative in the world of synthetic organic chemistry. Aryl substituted moieties and their derivatives are significant class of substances in medicinal and organic chemistry. Many alkaloids from natural marine sources comprising dihydropyrimidinones core have been isolated which possess fascinating biological properties. Intensive explorations have been carried out on these compounds because they possess close similitude to clinically used nifedipine, nicardipine etc. which are also Biginelli product analogues. Due to the interesting pharmacological properties associated with the privileged DHPM structures, the Biginelli reaction and related procedures have received increasing attention in recent years.

Biological activity of dihydropyrimidinone (DHPM) derivatives: A systematic review

Dihydropyrimidinones are heterocycles with a pyrimidine moiety in the ring nucleus, which, in recent decades, have aroused interest in medicinal chemistry due to alleged versatile biological activity. In this systematic review, we describe the currently published activities of dihydropyrimidinone derivatives. Between 1990 and December 31st, 2016, 115 articles outlined biological activities or toxicity of DHPM derivatives, 12 of those involved in vivo experiments. The main activities associated with this class of compounds are antitumoral (43 articles), anti-inflammatory (12 articles), antibacterial (20 articles) and calcium channel antagonism/inhibition (14 articles). Antitumoral activity is the main biological property evaluated, since the main representative compound of this class (monastrol) is a known Eg5 kinesin inhibitor. This review depicts a variety of other pharmacological activities associated with DHPM derivatives, but the main findings are essentially in vitro characteristics of the substances. This review presents the current state of the art of DHPM biological activities and demonstrates that there is still a need for further in vivo studies to better delineate the pharmacological potential of this class of substances.

Targeting Cancer Stem Cells with Novel 4-(4-Substituted phenyl)-5-(3,4,5-trimethoxy/3,4-dimethoxy)-benzoyl-3,4-dihydropyrimidine-2(1H)-one/thiones

Novel 4-(4-substituted phenyl)-5-(3,4,5-trimethoxy/3,4-dimethoxy)-benzoyl-3,4-dihydropyrimidine-2(1H)-one/thione derivatives (DHP1–9) were designed, synthesized, characterized and evaluated for antitumor activity against cancer stem cells. The compounds were synthesized in one pot. Enaminones E1 and E2 were reacted with substituted benzaldehydes and urea/thiourea in the presence of glacial acetic acid. The synthesized compounds were characterized by spectral analysis. The compounds were screened in vitro against colon cancer cell line (LOVO) colon cancer stem cells. Most of the compounds were found to be active against side population cancer stem cells with an inhibition of >50% at a 10 μM concentration. Compounds DHP-1, DHP-7 and DHP-9 were found to be inactive. Compound DHP-5 exhibited an in vitro anti-proliferative effect and arrested cancer cells at the Gap 2 phase (G2) checkpoint and demonstrated an inhibitory effect on tumor growth for a LOVO xenograft in a nude mouse experiment.

The conserved core enzymatic activities and the distinct dynamics of polyomavirus large T antigens

Several human polyomaviruses including JCV, BKV and TSV are associated with diseases, particularly in immunosuppressed patients. While the large T antigen (LT) encoded by the monkey polyomavirus SV40 is well studied, and possesses intrinsic ATPase and DNA helicase activities, the LTs of the human polyomaviruses are relatively uncharacterized. In order to evaluate whether these enzymatic activities, which are required for viral DNA replication, are conserved between polyomaviruses, we performed a comparative study using the LTs from JCV, TSV and SV40. The ATPase and DNA helicase activities and the interaction with the cellular tumor suppressor p53 were assayed for the purified Zn-ATPase domains of the three LTs. We found that all Zn-ATPases were active ATPases. The Zn-ATPase domains also functioned as DNA helicases, although the measured kinetic constants differed among the three proteins. In addition, when tested against four small molecule ATPase inhibitors, the Zn-ATPase domains of TSV was more resistant than that of SV40 and JCV. Our results show that, while LTs from JCV and TSV share the core ATPase and DNA helicase activities, they possess important functional differences that might translate into their respective abilities to infect and replicate in hosts.

Novel hybrid DHPM-fatty acids: synthesis and activity against glioma cell growth in vitro

We described the first synthesis of fatty acid 3,4-dihydropyrimidinones (DHPM-fatty acids) using the Biginelli multicomponent reaction. Antiproliferative activity on two glioma cell lines (C6 rat and U-138-MG human) was also reported. The novel DHPM-fatty acids reduced glioma cell viability relative to temozolomide. Hybrid oxo-monastrol-palmitic acid was the most potent, reducing U-138-MG human cell viability by ca. 50% at 10 μM. In addition, the DHPM-fatty acids showed a large safety range to neural cells, represented by the organotypic hippocampal culture. These results suggest that the increased lipophilicity of DHPM-fatty acids offer a promising approach to overcoming resistance to chemotherapy and may play an important role in the development of new antitumor drugs.

A mini-review on Biginelli adducts with notable pharmacological properties

Since the disclosure of Biginelli reaction by the chemist Pietro Biginelli, functionalized 3,4-dihydropyrimidin-2(1H)-ones/thiones (DHPMs) have emerged as prototypes for the design of compounds with a broad variety of biological activities. This mini-review describes over 100 Biginelli adducts demonstrated to be promising anticancer, inhibitors of calcium channel, anti-inflammatory, antimicrobial and antioxidant agents. Thus, this compilation presents the most notable in vitro and in vivo results for such fascinating class of organic compounds.

Inhibition of large T antigen ATPase activity as a potential strategy to develop anti-polyomavirus JC drugs

INTRODUCTION

This study evaluates polyomavirus JC (JCV) large T antigen (LTA) as a potential target for drug development. LTA is a hexameric protein with a helicase activity that is powered by ATP binding and hydrolysis. The helicase and ATPase function is critical for viral replication.

METHODS

Recombinant JCV LTA was produced in an Escherichia coli based expression plasmid. ATPase activity was measured using the malachite green assay. A high throughput screen was completed using a brain-biased library of 75,000 drug-like compounds selected for physicochemical properties consistent with blood-brain barrier permeability.

RESULTS

Five compounds showed non-competitive inhibition of ATPase activity with an EC50 ⩽ 15 μM. Modest antiviral activity was demonstrated in an immunofluorescence assay for JCV VP-1 expression in COS7 cells (EC50 15, 18, 20, 27, and 52 μM respectively). The compounds also inhibited viral replication in a real time PCR assay at comparable concentrations. LD50 in the MTS96 and Cell TiterGlo assays was >100 μM for all compounds in COS7 as well as HEK293 cells. However, two compounds inhibited cell proliferation in culture with IC50 values of 43 and 34 μM respectively. Despite substantial amino acid similarity between polyomavirus JC, BK and SV40 proteins, these compounds differ from those previously reported to inhibit SV40 LTA ATPase in chemical structure as well as a non-competitive mechanism of inhibition.

CONCLUSION

LTA ATPase is a valid target for discovery. Additional screening and chemical optimization is needed to develop clinically useful compounds with less toxicity, which should be measured by metabolic as well as cell proliferation assays.

Ciprofloxacin is an inhibitor of the Mcm2-7 replicative helicase

Most currently available small molecule inhibitors of DNA replication lack enzymatic specificity, resulting in deleterious side effects during use in cancer chemotherapy and limited experimental usefulness as mechanistic tools to study DNA replication. Towards development of targeted replication inhibitors, we have focused on Mcm2-7 (minichromosome maintenance protein 2-7), a highly conserved helicase and key regulatory component of eukaryotic DNA replication. Unexpectedly we found that the fluoroquinolone antibiotic ciprofloxacin preferentially inhibits Mcm2-7. Ciprofloxacin blocks the DNA helicase activity of Mcm2-7 at concentrations that have little effect on other tested helicases and prevents the proliferation of both yeast and human cells at concentrations similar to those that inhibit DNA unwinding. Moreover, a previously characterized mcm mutant (mcm4chaos3) exhibits increased ciprofloxacin resistance. To identify more potent Mcm2-7 inhibitors, we screened molecules that are structurally related to ciprofloxacin and identified several that compromise the Mcm2-7 helicase activity at lower concentrations. Our results indicate that ciprofloxacin targets Mcm2-7 in vitro, and support the feasibility of developing specific quinolone-based inhibitors of Mcm2-7 for therapeutic and experimental applications.

Contributions of academic laboratories to the discovery and development of chemical biology tools

The academic setting provides an environment that may foster success in the discovery of certain types of small molecule tools while proving less suitable in others. For example, small molecule probes for poorly understood systems, those that exploit a specific resident expertise, and those whose commercial return is not apparent are ideally suited to be pursued in a university setting. In this review, we highlight five projects that emanated from academic research groups and generated valuable tool compounds that have been used to interrogate biological phenomena: reactive oxygen species (ROS) sensors, GPR30 agonists and antagonists, selective CB2 agonists, Hsp70 modulators, and β-amyloid PET imaging agents. By taking advantage of the unique expertise resident in university settings and the ability to pursue novel projects that may have great scientific value but with limited or no immediate commercial value, probes from academic research groups continue to provide useful tools and generate a long-term resource for biomedical researchers.

MARCKS and HSP70 interactions regulate mucin secretion by human airway epithelial cells in vitro

Myristoylated alanine-rich C kinase substrate (MARCKS) protein has been recognized as a key regulatory molecule controlling mucin secretion by airway epithelial cells in vitro and in vivo. We recently showed that two intracellular chaperones, heat shock protein 70 (HSP70) and cysteine string protein (CSP), associate with MARCKS in the secretory mechanism. To elucidate more fully MARCKS-HSP70 interactions in this process, studies were performed in well-differentiated normal human bronchial epithelial (NHBE) cells maintained in air-liquid interface culture utilizing specific pharmacological inhibition of HSP70 with pyrimidinone MAL3-101 and siRNA approaches. The results indicate that HSP70 interaction with MARCKS is enhanced after exposure of the cells to the protein kinase C activator/mucin secretagogue, phorbol 12-myristate 13-acetate (PMA). Pretreatment of NHBEs with MAL3-101 attenuated in a concentration-dependent manner PMA-stimulated mucin secretion and interactions among HSP70, MARCKS, and CSP. In additional studies, trafficking of MARCKS in living NHBE cells was investigated after transfecting cells with fluorescently tagged DNA constructs: MARCKS-yellow fluorescent protein, and/or HSP70-cyan fluorescent protein. Cells were treated with PMA 48 h posttransfection, and trafficking of the constructs was examined by confocal microscopy. MARCKS translocated rapidly from plasma membrane to cytoplasm, whereas HSP70 was observed in the cytoplasm and appeared to associate with MARCKS after PMA exposure. Pretreatment of cells with either MAL3-101 or HSP70 siRNA inhibited translocation of MARCKS. These results provide evidence of a role for HSP70 in mediating mucin secretion via interactions with MARCKS and that these interactions are critical for the cytoplasmic translocation of MARCKS upon its phosphorylation.

A screen for modulators of large T antigen's ATPase activity uncovers novel inhibitors of Simian Virus 40 and BK virus replication

New polyomaviruses are continually being identified, and it is likely that links between this virus family and disease will continue to emerge. Unfortunately, a specific treatment for polyomavirus-associated disease is lacking. Because polyomaviruses express large Tumor Antigen, TAg, we hypothesized that small molecule inhibitors of the essential ATPase activity of TAg would inhibit viral replication. Using a new screening platform, we identified inhibitors of TAg's ATPase activity. Lead compounds were moved into a secondary assay, and ultimately two FDA approved compounds, bithionol and hexachlorophene, were identified as the most potent TAg inhibitors known to date. Both compounds inhibited Simian Virus 40 replication as assessed by plaque assay and quantitative PCR. Moreover, these compounds inhibited BK virus, which causes BKV Associated Nephropathy. In neither case was host cell viability compromised at these concentrations. Our data indicate that directed screening for TAg inhibitors is a viable method to identify polyomavirus inhibitors, and that bithionol and hexachlorophene represent lead compounds that may be further modified and/or ultimately used to combat diseases associated with polyomavirus infection.

High-throughput screening identifies a bisphenol inhibitor of SV40 large T antigen ATPase activity

The authors conducted a high-throughput screening campaign for inhibitors of SV40 large T antigen ATPase activity to identify candidate antivirals that target the replication of polyomaviruses. The primary assay was adapted to 1536-well microplates and used to screen the National Institutes of Health Molecular Libraries Probe Centers Network library of 306 015 compounds. The primary screen had an Z value of ~0.68, signal/background = 3, and a high (5%) DMSO tolerance. Two counterscreens and two secondary assays were used to prioritize hits by EC(50), cytotoxicity, target specificity, and off-target effects. Hits that inhibited ATPase activity by >44% in the primary screen were tested in dose-response efficacy and eukaryotic cytotoxicity assays. After evaluation of hit cytotoxicity, drug likeness, promiscuity, and target specificity, three compounds were chosen for chemical optimization. Chemical optimization identified a class of bisphenols as the most effective biochemical inhibitors. Bisphenol A inhibited SV40 large T antigen ATPase activity with an IC(50) of 41 µM in the primary assay and 6.2 µM in a cytoprotection assay. This compound class is suitable as probes for biochemical investigation of large T antigen ATPase activity, but because of their cytotoxicity, further optimization is necessary for their use in studying polyomavirus replication in vivo.

Plasmodium falciparum encodes a single cytosolic type I Hsp40 that functionally interacts with Hsp70 and is upregulated by heat shock

Heat shock protein 70 (Hsp70) and heat shock protein 40 (Hsp40) function as molecular chaperones during the folding and trafficking of proteins within most cell types. However, the Hsp70-Hsp40 chaperone partnerships within the malaria parasite, Plasmodium falciparum, have not been elucidated. Only one of the 43 P. falciparum Hsp40s is predicted to be a cytosolic, canonical Hsp40 (termed PfHsp40) capable of interacting with the major cytosolic P. falciparum-encoded Hsp70, PfHsp70. Consistent with this hypothesis, we found that PfHsp40 is upregulated under heat shock conditions in a similar pattern to PfHsp70. In addition, PfHsp70 and PfHsp40 reside mainly in the parasite cytosol, as assessed using indirect immunofluorescence microscopy. Recombinant PfHsp40 stimulated the ATP hydrolytic rates of both PfHsp70 and human Hsp70 similar to other canonical Hsp40s of yeast (Ydj1) and human (Hdj2) origin. In contrast, the Hsp40-stimulated plasmodial and human Hsp70 ATPase activities were differentially inhibited in the presence of pyrimidinone-based small molecule modulators. To further probe the chaperone properties of PfHsp40, protein aggregation suppression assays were conducted. PfHsp40 alone suppressed protein aggregation, and cooperated with PfHsp70 to suppress aggregation. Together, these data represent the first cellular and biochemical evidence for a PfHsp70-PfHsp40 partnership in the malaria parasite, and furthermore that the plasmodial and human Hsp70-Hsp40 chaperones possess unique attributes that are differentially modulated by small molecules.

Screening for small molecule modulators of Hsp70 chaperone activity using protein aggregation suppression assays: inhibition of the plasmodial chaperone PfHsp70-1

Plasmodium falciparum heat shock protein 70 (PfHsp70-1) is thought to play an essential role in parasite survival and virulence in the human host, making it a potential antimalarial drug target. A malate dehydrogenase based aggregation suppression assay was adapted for the screening of small molecule modulators of Hsp70. A number of small molecules of natural (marine prenylated alkaloids and terrestrial plant naphthoquinones) and related synthetic origin were screened for their effects on the protein aggregation suppression activity of purified recombinant PfHsp70-1. Five compounds (malonganenone A-C, lapachol and bromo-β-lapachona) were found to inhibit the chaperone activity of PfHsp70-1 in a concentration dependent manner, with lapachol preferentially inhibiting PfHsp70-1 compared to another control Hsp70. Using growth inhibition assays on P. falciparum infected erythrocytes, all of the compounds, except for malonganenone B, were found to inhibit parasite growth with IC50 values in the low micromolar range. Overall, this study has identified two novel classes of small molecule inhibitors of PfHsp70-1, one representing a new class of antiplasmodial compounds (malonganenones). In addition to demonstrating the validity of PfHsp70-1 as a possible drug target, the compounds reported in this study will be potentially useful as molecular probes for fundamental studies on Hsp70 chaperone function.

Proteostasis: a new therapeutic paradigm for pulmonary disease

Among lung pathologies, α1AT, chronic obstructive pulmonary disease (COPD), emphysema, and asthma are diseases triggered by local environmental stress in the airway that we refer to herein collectively as airway stress diseases (ASDs). A deficiency of α-1-antitrypsin (α1AT) is an inherited genetic disorder that is a consequence of the misfolding of α1AT during protein synthesis in liver hepatocytes, reducing secretion to the plasma and delivery to the lung. Deficiency of α1AT in the lung triggers a similar pathological phenotype to other ASDs. Moreover, the loss of α1AT in the lung is a well-known environmental risk factor for COPD/emphysema. To date there are no effective therapeutic approaches to address ASDs, which reflects a general lack of understanding of their cellular basis. Herein, we propose that ASDs are disorders of proteostasis. That is, they are initiated and propagated by a common theme-a challenge to protein folding capacity maintained by the proteostasis network (PN) (see Balch et al., Science 2008;319:916-919). The PN is a network of chaperones and degradative components that generates and manages protein folding pathways responsible for normal human physiology. In ASD, we suggest that the PN system fails to respond to the increased burden of unfolded proteins due to genetic and environmental stresses, thus triggering pulmonary pathophysiology. We introduce the enabling concept of proteostasis regulators (PRs), small molecules that regulate signaling pathways that control the composition and activity of PN components, as a new and general approach for therapeutic management of ASDs.

Chemical methodology as a source of small-molecule checkpoint inhibitors and heat shock protein 70 (Hsp70) modulators

Unique chemical methodology enables the synthesis of innovative and diverse scaffolds and chemotypes and allows access to previously unexplored "chemical space." Compound collections based on such new synthetic methods can provide small-molecule probes of proteins and/or pathways whose functions are not fully understood. We describe the identification, characterization, and evolution of two such probes. In one example, a pathway-based screen for DNA damage checkpoint inhibitors identified a compound, MARPIN (ATM and ATR pathway inhibitor) that sensitizes p53-deficient cells to DNA-damaging agents. Modification of the small molecule and generation of an immobilized probe were used to selectively bind putative protein target(s) responsible for the observed activity. The second example describes a focused library approach that relied on tandem multicomponent reaction methodologies to afford a series of modulators of the heat shock protein 70 (Hsp70) molecular chaperone. The synthesis of libraries based on the structure of MAL3-101 generated a collection of chemotypes, each modulating Hsp70 function, but exhibiting divergent pharmacological activities. For example, probes that compromise the replication of a disease-associated polyomavirus were identified. These projects highlight the importance of chemical methodology development as a source of small-molecule probes and as a drug discovery starting point.

Synthesis of 6-amino-5-cyano-1,4-disubstituted-2(1H)-pyrimidinones via copper-(I)-catalyzed alkyne-azide 'click chemistry' and their reactivity

In this paper we present the room temperature synthesis of a novel serie of 1,4-disubstituted-1,2,3-triazoles 4a-l by employing the (3+2) cycloaddition reaction of pyrimidinones containing alkyne functions with different model azides in the presence of copper sulphate and sodium ascorbate. To obtain the final triazoles, we also synthesized the major precursors 6-amino-5-cyano-1,4-disubstituted-2(1H)-pyrimidinones 3a-r from ethyl 2,2-dicyanovinylcarbamate derivatives 2a-c and various primary aromatic amines containing an alkyne group. The triazoles were prepared in good to very good yields.