Casein kinase 1ε and 1α as novel players in polycystic kidney disease and mechanistic targets for (R)-roscovitine and (S)-CR8.

Following the discovery of (R)-roscovitine's beneficial effects in three polycystic kidney disease (PKD) mouse models, cyclin-dependent kinases (CDKs) inhibitors have been investigated as potential treatments. We have used various affinity chromatography approaches to identify the molecular targets of roscovitine and its more potent analog (S)-CR8 in human and murine polycystic kidneys. These methods revealed casein kinases 1 (CK1) as additional targets of the two drugs. CK1ε expression at the mRNA and protein levels is enhanced in polycystic kidneys of 11 different PKD mouse models as well as in human polycystic kidneys. A shift in the pattern of CK1α isoforms is observed in all PKD mouse models. Furthermore, the catalytic activities of both CK1ε and CK1α are increased in mouse polycystic kidneys. Inhibition of CK1ε and CK1α may thus contribute to the long-lasting attenuating effects of roscovitine and (S)-CR8 on cyst development. CDKs and CK1s may constitute a dual therapeutic target to develop kinase inhibitory PKD drug candidates.

TRPC6 channel translocation into phagosomal membrane augments phagosomal function.

Defects in the innate immune system in the lung with attendant bacterial infections contribute to lung tissue damage, respiratory insufficiency, and ultimately death in the pathogenesis of cystic fibrosis (CF). Professional phagocytes, including alveolar macrophages (AMs), have specialized pathways that ensure efficient killing of pathogens in phagosomes. Phagosomal acidification facilitates the optimal functioning of degradative enzymes, ultimately contributing to bacterial killing. Generation of low organellar pH is primarily driven by the V-ATPases, proton pumps that use cytoplasmic ATP to load H(+) into the organelle. Critical to phagosomal acidification are various channels derived from the plasma membrane, including the anion channel cystic fibrosis transmembrane conductance regulator, which shunt the transmembrane potential generated by movement of protons. Here we show that the transient receptor potential canonical-6 (TRPC6) calcium-permeable channel in the AM also functions to shunt the transmembrane potential generated by proton pumping and is capable of restoring microbicidal function to compromised AMs in CF and enhancement of function in non-CF cells. TRPC6 channel activity is enhanced via translocation to the cell surface (and then ultimately to the phagosome during phagocytosis) in response to G-protein signaling activated by the small molecule (R)-roscovitine and its derivatives. These data show that enhancing vesicular insertion of the TRPC6 channel to the plasma membrane may represent a general mechanism for restoring phagosome activity in conditions, where it is lost or impaired.

From Drug Screening to Target Deconvolution: a Target-Based Drug Discovery Pipeline Using Leishmania Casein Kinase 1 Isoform 2 To Identify Compounds with Antileishmanial Activity.

Existing therapies for leishmaniases present significant limitations, such as toxic side effects, and are rendered inefficient by parasite resistance. It is of utmost importance to develop novel drugs targeting Leishmania that take these two limitations into consideration. We thus chose a target-based approach using an exoprotein kinase, Leishmania casein kinase 1.2 (LmCK1.2) that was recently shown to be essential for intracellular parasite survival and infectivity. We developed a four-step pipeline to identify novel selective antileishmanial compounds. In step 1, we screened 5,018 compounds from kinase-biased libraries with Leishmania and mammalian CK1 in order to identify hit compounds and assess their specificity. For step 2, we selected 88 compounds among those with the lowest 50% inhibitory concentration to test their biological activity on host-free parasites using a resazurin reduction assay and on intramacrophagic amastigotes using a high content phenotypic assay. Only 75 compounds showed antileishmanial activity and were retained for step 3 to evaluate their toxicity against mouse macrophages and human cell lines. The four compounds that displayed a selectivity index above 10 were then assessed for their affinity to LmCK1.2 using a target deconvolution strategy in step 4. Finally, we retained two compounds, PP2 and compound 42, for which LmCK1.2 seems to be the primary target. Using this four-step pipeline, we identify from several thousand molecules, two lead compounds with a selective antileishmanial activity.

Antitumoral effects of cyclin-dependent kinases inhibitors CR8 and MR4 on chronic myeloid leukemia cell lines.

BACKGROUND: Although Imatinib mesylate has revolutionized the treatment of chronic myeloid leukemia, some patients develop resistance with progression of leukemia. Alternative or additional targeting of signalling pathways deregulated in Bcr-Abl-driven chronic myeloid leukemia may provide a feasible option for improving clinical response and overcoming resistance. RESULTS: In this study, we investigate ability of CR8 isomers (R-CR8 and S-CR8) and MR4, three derivatives of the cyclin-dependent kinases (CDKs) inhibitor Roscovitine, to exert anti-leukemic activities against chronic myeloid leukemia in vitro and then, we decipher their mechanisms of action. We show that these CDKs inhibitors are potent inducers of growth arrest and apoptosis of both Imatinib-sensitive and -resistant chronic myeloid leukemia cell lines. CR8 and MR4 induce dose-dependent apoptosis through mitochondrial pathway and further caspases 8/10 and 9 activation via down-regulation of short-lived survival and anti-apoptotic factors Mcl-1, XIAP and survivin which are strongly implicated in survival of Bcr-Abl transformed cells. CONCLUSIONS: These results suggest that CDK inhibitors may constitute a complementary approach to treat chronic myeloid leukemia.

Small-molecule inducers of Aß-42 peptide production share a common mechanism of action.

The pathways leading specifically to the toxic Aß42 peptide production, a key event in Alzheimer's disease (AD), are unknown. While searching for pathways that mediate pathological increases of Aß42, we identified Aftin-4, a new compound that selectively and potently increases Aß42 compared to DMSO (N2a cells: 7-fold; primary neurons: 4-fold; brain lysates: 2-fold) with an EC(50) of 30 µM. These results were confirmed by ELISA and IP-WB. Using affinity chromatography and mass spectrometry, we identified 3 proteins (VDAC1, prohibitin, and mitofilin) relevant to AD that interact with Aftin-4, but not with a structurally similar but inactive molecule. Electron microscopy studies demonstrated that Aftin-4 induces a reversible mitochondrial phenotype reminiscent of the one observed in AD brains. Sucrose gradient fractionation showed that Aftin-4 perturbs the subcellular localization of γ-secretase components and could, therefore, modify γ-secretase specificity by locally altering its membrane environment. Remarkably, Aftin-4 shares all these properties with two other "AD accelerator" compounds. In summary, treatment with three Aß42 raising agents induced similar biochemical alterations that lead to comparable cellular phenotypes in vitro, suggesting a common mechanism of action involving three structural cellular targets.

Synthesis and mechanism of action of new purine derivatives against triple negative breast cancer.

Triple negative breast cancer (TNBC) is considered to be the most difficult subtype of breast cancer to treat because of its extremely prone to metastasis and the lack of targeted therapy drugs. New purine derivatives were synthesized and evaluated in a series of kinases and cell lines. The most active compounds 3g and 3j were selected based on their antiproliferative activities, then their pharmaceutical activity and mechanism in MDA-MB-231 cells were analyzed. The results in vitro indicated that compounds 3g and 3j can induce MDA-MB-231 cells apoptosis, and inhibit its migration and angiogenesis through influencing protein expression such as Bcl-2, Bax, Bcl-xl, P38, MMP2, MMP9, AKT and EGFR. In vivo results indicate that compounds 3g and 3j can inhibit tumor growth and metastasis and reduce the expression of Ki67 and CD31 protein in TNBC xenograft models. These findings not only broaden our understanding of the anti-TNBC effects and mechanisms of compounds 3g and 3j, but also provide new ideas and reference directions for the treatment of TNBC.

Targeting low molecular weight cyclin E (LMW-E) in breast cancer.

Low molecular weight cyclin E (LMW-E) plays an important oncogenic role in breast cancer. LMW-E, which is not found in normal tissue, can promote the formation of aggressive tumors and can lead to increased genomic instability and tumorigenesis. Additionally, breast cancer patients whose tumors express LMW-E have a very poor prognosis. Therefore, we investigated LMW-E as a potential specific target for treatment either alone or in combination therapy. We hypothesized that because LMW-E binds to CDK2 more efficiently than full length cyclin E, resulting in increased activity, CDK inhibitors could be used to target tumors with LMW-E bound to CDK2. To test the hypothesis, an inducible full length and LMW-E MCF7-Tet-On system was established. Cyclin E (full length (EL) or LMW-E) is only expressed upon induction of the transgene. The doubling times of cells were unchanged when the transgenes were induced. However, upon induction, the kinase activity associated with LMW-E was much higher than that in the EL induced cells or any of the uninduced cells. Additionally only the LMW-E induced cells underwent chromosome aberrations and increased polyploidy. By examining changes in proliferation and survival in cells with induced full length and LMW-E, CDK inhibitors alone were determined to be insufficient to specifically inhibit LMW-E expressing cells. However, in combination with doxorubicin, the CDK inhibitor, roscovitine (seliciclib, CYC202), synergistically led to increased cell death in LMW-E expressing cells. Clinically, the combination of CDK inhibitors and chemotherapy such as doxorubicin provides a viable personalized treatment strategy for those breast cancer patients whose tumors express the LMW-E.

Molecular mechanisms in Alzheimer's disease and related potential treatments such as structural target convergence of antibodies and simple organic molecules.

The amyloid cascade is the most frequently accepted hypothesis of Alzheimer's Disease (AD). According to this hypothesis, the formation of plaques precedes the appearance of fibrillary tangles. Therapeutic agents able to inhibit the formation of plaques are therefore considered as potential disease-modifying treatments (DMT) that could prevent or limit the progression of AD. Plaques are deposits formed by aggregates of amyloid-ß (Aß)-peptides. These peptides are metabolites of amyloid precursor protein (APP) first mediated by two enzymes: ß-secretase 1 (BACE1) and γ-secretase. Molecular identification of these two enzymes has stimulated the development of their inhibitors. The clinical testing of these two classes of molecules has not been successful to date. The oligomerization of Aß-peptides into plaques is now targeted by immunological approaches such as antibodies and vaccines. Structural consideration of the Aß-peptide sequence led to the launch of the antibody Aducanumab. Several other antibodies are in late clinical phases. Progress in the understanding of the effects of N-truncated Aß-peptides such as pE3-42, formed by the action of recently well characterized enzymes (aminopeptidase A, dipeptidylpeptidase-4 and glutaminyl cyclase) suggests that oligomerization can be limited either by enzyme inhibitors or antibody approaches. This strategy associating two structurally interconnected mechanisms is focused in this review.

Synthesis of conjugates of 6-aminophenanthridine and guanabenz, two structurally unrelated prion inhibitors, for the determination of their cellular targets by affinity chromatography.

The synthesis of affinity matrices for 6-aminophenanthridine (6AP) and 2,6-dichlorobenzylidenaminoguanidine (Guanabenz, GA), two unrelated prion inhibitors, is described. In both cases, the same simple spacer, epsilon-aminocaproylaminopentanol, was introduced by a Mitsunobu reaction and the choice of the anchoring position of the linker was determined by the study of the residual antiprion activity of the corresponding 6AP or GA conjugates. Very recently, these two affinity matrices were used for chromatography assays leading to the identification of ribosome (via the rRNA) as a common target of these two antiprion drugs. Here, we show, using competition experiments with Quinacrine (QC) and Chlorpromazine (CPZ), two other antiprion drugs, that QC, but not CPZ, may also directly target the rRNA.

Author Correction: A Small Compound Targeting Prohibitin with Potential Interest for Cognitive Deficit Rescue in Aging mice and Tau Pathology Treatment.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

A Small Compound Targeting Prohibitin with Potential Interest for Cognitive Deficit Rescue in Aging mice and Tau Pathology Treatment.

Neurodegenerative diseases, including Alzheimer's and Parkinson's disease, are characterized by increased protein aggregation in the brain, progressive neuronal loss, increased inflammation, and neurogenesis impairment. We analyzed the effects of a new purine derivative drug, PDD005, in attenuating mechanisms involved in the pathogenesis of neurodegenerative diseases, using both in vivo and in vitro models. We show that PDD005 is distributed to the brain and can rescue cognitive deficits associated with aging in mice. Treatment with PDD005 prevents impairment of neurogenesis by increasing sex-determining region Y-box 2, nestin, and also enhances synaptic function through upregulation of synaptophysin and postsynaptic density protein 95. PDD005 treatment also reduced neuro-inflammation by decreasing interleukin-1ß expression, activation of astrocytes, and microglia. We identified prohibitin as a potential target in mediating the therapeutic effects of PDD005 for the treatment of cognitive deficit in aging mice. Additionally, in the current study, glycogen synthase kinase appears to attenuate tau pathology.

Novel Mouse Tauopathy Model for Repetitive Mild Traumatic Brain Injury: Evaluation of Long-Term Effects on Cognition and Biomarker Levels After Therapeutic Inhibition of Tau Phosphorylation.

Traumatic brain injury (TBI) is a risk factor for a group of neurodegenerative diseases termed tauopathies, which includes Alzheimer's disease and chronic traumatic encephalopathy (CTE). Although TBI is stratified by impact severity as either mild (m), moderate or severe, mTBI is the most common and the most difficult to diagnose. Tauopathies are pathologically related by the accumulation of hyperphosphorylated tau (P-tau) and increased total tau (T-tau). Here we describe: (i) a novel human tau-expressing transgenic mouse model, TghTau/PS1, to study repetitive mild closed head injury (rmCHI), (ii) quantitative comparison of T-tau and P-tau from brain and plasma in TghTau/PS1 mice over a 12 month period following rmCHI (and sham), (iii) the usefulness of P-tau as an early- and late-stage blood-based biochemical biomarker for rmCHI, (iii) the influence of kinase-targeted therapeutic intervention on rmCHI-associated cognitive deficits using a combination of lithium chloride (LiCl) and R-roscovitine (ros), and (iv) correlation of behavioral and cognitive changes with concentrations of the brain and blood-based T-tau and P-tau. Compared to sham-treated mice, behavior changes and cognitive deficits of rmCHI-treated TghTau/PS1 mice correlated with increases in both cortex and plasma T-tau and P-tau levels over 12 months. In addition, T-tau, but more predominantly P-tau, levels were significantly reduced in the cortex and plasma by LiCl + ros approaching the biomarker levels in sham and drug-treated sham mice (the drugs had only modest effects on the T-tau and P-tau levels in sham mice) throughout the 12 month study period. Furthermore, although we also observed a reversal of the abnormal behavior and cognitive deficits in the drug-treated rmCHI mice (compared to the untreated rmCHI mice) throughout the time course, these drug-treated effects were most pronounced up until 10 and 12 months where the abnormal behavior and cognition deficits began to gradually increase. These studies describe: (a) a translational relevant animal model for TBI-linked tauopathies, and (b) utilization of T-tau and P-tau as rmCHI biomarkers in plasma to monitor novel therapeutic strategies and treatment regimens for these neurodegenerative diseases.

Structural analogues of roscovitine rescue the intracellular traffic and the function of ER-retained ABCB4 variants in cell models.

Adenosine triphosphate binding cassette transporter, subfamily B member 4 (ABCB4) is the transporter of phosphatidylcholine at the canalicular membrane of hepatocytes. ABCB4 deficiency, due to genetic variations, is responsible for progressive familial intrahepatic cholestasis type 3 (PFIC3) and other rare biliary diseases. Roscovitine is a molecule in clinical trial that was shown to correct the F508del variant of cystic fibrosis transmembrane conductance regulator (CFTR), another ABC transporter. In the present study, we hypothesized that roscovitine could act as a corrector of ABCB4 traffic-defective variants. Using HEK and HepG2 cells, we showed that roscovitine corrected the traffic and localisation at the plasma membrane of ABCB4-I541F, a prototypical intracellularly retained variant. However, roscovitine caused cytotoxicity, which urged us to synthesize non-toxic structural analogues. Roscovitine analogues were able to correct the intracellular traffic of ABCB4-I541F in HepG2 cells. Importantly, the phospholipid secretion activity of this variant was substantially rescued by three analogues (MRT2-235, MRT2-237 and MRT2-243) in HEK cells. We showed that these analogues also triggered the rescue of intracellular traffic and function of two other intracellularly retained ABCB4 variants, i.e. I490T and L556R. Our results indicate that structural analogues of roscovitine can rescue genetic variations altering the intracellular traffic of ABCB4 and should be considered as therapeutic means for severe biliary diseases caused by this class of variations.

Recent advances in the development of cyclin-dependent kinase 7 inhibitors.

Cyclin dependent kinase 7 (CDK7) plays a double role as it activates several other cyclin dependent kinases and participates to the initiation of transcription. This kinase is overexpressed in various types of tumors. Relatively few selective CDK7 inhibitors have been up to now disclosed. Most of these inhibitors belong to two chemical families: pyrazolopyrimidines and pyrazolotriazines on one side and pyrimidines on another side. They also differ by their molecular mechanism of action. Some are acting as competitive inhibitors and some others are covalent inhibitors. With these tools, the understanding of the potential therapeutic interest of CDK7 inhibitors in cancer is rapidly growing. They display antiproliferative activity against various types of tumors and leukemia and synergies have been identified. Two inhibitors are undergoing clinical testing. The most potent compounds inhibit a large number of cell-lines with IC50 < 200 nM.

A ß-glucuronidase-responsive albumin-binding prodrug for potential selective kinase inhibitor-based cancer chemotherapy.

We report on the synthesis and in vitro biological evaluations of a nanomolar protein kinase inhibitor (PKI) and its ß-glucuronidase-responsive albumin-binding prodrug. The highly potent PKI is 400-3400 times more cytotoxic than the well-known PKI Roscovitine. The prodrug is able to bind covalently to human serum albumin through Michael addition and release the cytotoxic PKI in the presence of ß-glucuronidase, an enzyme over-expressed in the microenvironment of solid tumours.

A Simple Isomerization of the Purine Scaffold of a Kinase Inhibitor, Roscovitine, Affords a Four- to Seven-Fold Enhancement of Its Affinity for Four CDKs. Could This Be Traced Back to Conjugation-Induced Stiffenings/Loosenings of Rotational Barriers?

Roscovitine is an antitumor purine inhibitor of cyclin-dependent kinase CDK5, for which it displays submicromolar affinity. It reached phase IIb clinical trials in 2007. The search for analogues with improved kinase affinities led recently to an isomer, finisterine, having a nearly 10-fold greater affinity for both CDK5 and CDK9. It solely differs by the displacement of one nitrogen atom in the purine ring, from position 6 to position 9. This has no incidence on the intermolecular interaction of either drug with the neighboring sites that anchor the ring in the recognition site. Quantum chemistry calculations combined with conformational and topological analyses of the impact of the purine ring isomerization of roscovitine and finisterine on its conformational stability show that the modified electronic conjugation, on the other hand, results in a stiffening of the rotational barrier around the extracyclic C-NH bond of finisterine, vicinal to N9, and to which an aryl ring is connected, along with a loosening of the barrier around an extracyclic C6-C bond connecting to a shorter, hydrophobic arm. The first effect is proposed to lead to a lesser hydration entropy of solvation in the case of finisterine, thus to a facilitated desolvation term in the overall energy balances.

Exploration of the imidazo[1,2-b]pyridazine scaffold as a protein kinase inhibitor.

3,6-Disubstituted imidazo[1,2-b]pyridazine derivatives were synthesized to identify new inhibitors of various eukaryotic kinases, including mammalian and protozoan kinases. Among the imidazo[1,2-b]pyridazines tested as kinase inhibitors, several derivatives were selective for DYRKs and CLKs, with IC50 < 100 nM. The characterization of the kinome of several parasites, such as Plasmodium and Leishmania, has pointed out profound divergences between protein kinases of the parasites and those of the host. This led us to investigate the activities of the prepared compounds against 11 parasitic kinases. 3,6-Disubstituted imidazo[1,2-b]pyridazines showed potent inhibition of Plasmodium falciparum CLK1 (PfCLK1). Compound 20a was found to be the most selective product against CLK1 (IC50 = 82 nM), CLK4 (IC50 = 44 nM), DYRK1A (IC50 = 50 nM), and PfCLK1 (IC50 = 32 nM). The compounds were also tested against Leishmania amazonensis. Several compounds showed anti-leishmanial activity at rather high (10 µM) concentration, but were not toxic at 1 µM or 10 µM, as judged by viability assays carried out using a neuroblastoma cell line.

Specific Triazine Herbicides Induce Amyloid-ß42 Production.

Proteolytic cleavage of the amyloid-ß protein precursor (AßPP) by secretases leads to extracellular release of amyloid-ß (Aß) peptides. Increased production of Aß42 over Aß40 and aggregation into oligomers and plaques constitute an Alzheimer's disease (AD) hallmark. Identifying products of the 'human chemical exposome' (HCE) able to induce Aß42 production may be a key to understanding some of the initiating causes of AD and to generate non-genetic, chemically-induced AD animal models. A cell model was used to screen HCE libraries for Aß42 inducers. Out of 3500+ compounds, six triazine herbicides were found that induced a ß- and γ-secretases-dependent, 2-10 fold increase in the production of extracellular Aß42 in various cell lines, primary neuronal cells, and neurons differentiated from human-induced pluripotent stem cells (iPSCs). Immunoprecipitation/mass spectrometry analyses show enhanced production of Aß peptides cleaved at positions 42/43, and reduced production of peptides cleaved at positions 38 and lower, a characteristic of AD. Neurons derived from iPSCs obtained from a familial AD (FAD) patient (AßPP K724N) produced more Aß42 versus Aß40 than neurons derived from healthy controls iPSCs (AßPP WT). Triazines enhanced Aß42 production in both control and AD iPSCs-derived neurons. Triazines also shifted the cleavage pattern of alcadeinα, another γ-secretase substrate, suggesting a direct effect of triazines on γ-secretase activity. In conclusion, several widely used triazines enhance the production of toxic, aggregation prone Aß42/Aß43 amyloids, suggesting the possible existence of environmental "Alzheimerogens" which may contribute to the initiation and propagation of the amyloidogenic process in late-onset AD.

Modulating Innate and Adaptive Immunity by (R)-Roscovitine: Potential Therapeutic Opportunity in Cystic Fibrosis.

(R)-Roscovitine, a pharmacological inhibitor of kinases, is currently in phase II clinical trial as a drug candidate for the treatment of cancers, Cushing's disease and rheumatoid arthritis. We here review the data that support the investigation of (R)-roscovitine as a potential therapeutic agent for the treatment of cystic fibrosis (CF). (R)-Roscovitine displays four independent properties that may favorably combine against CF: (1) it partially protects F508del-CFTR from proteolytic degradation and favors its trafficking to the plasma membrane; (2) by increasing membrane targeting of the TRPC6 ion channel, it rescues acidification in phagolysosomes of CF alveolar macrophages (which show abnormally high pH) and consequently restores their bactericidal activity; (3) its effects on neutrophils (induction of apoptosis), eosinophils (inhibition of degranulation/induction of apoptosis) and lymphocytes (modification of the Th17/Treg balance in favor of the differentiation of anti-inflammatory lymphocytes and reduced production of various interleukins, notably IL-17A) contribute to the resolution of inflammation and restoration of innate immunity, and (4) roscovitine displays analgesic properties in animal pain models. The fact that (R)-roscovitine has undergone extensive preclinical safety/pharmacology studies, and phase I and II clinical trials in cancer patients, encourages its repurposing as a CF drug candidate.

Natural product extracts of the Canadian prairie plant, Thermopsis rhombifolia, have anti-cancer activity in phenotypic cell-based assays.

Many plant species within the terrestrial ecological zones of Canada have not yet been investigated for anti-cancer activity. We examined the scientific literature describing the endemic flora from the prairie ecological zone and selected the species, Thermopsis rhombifolia, locally known as the buffalo bean, for investigation of its anti-cancer potential. We tested it in cell-based assays using phenotypic screens that feature some of the hallmarks of cancer. An ethanolic extract prepared from T. rhombifolia was cytotoxic to HT-29 (colon) and SH-SY5Y (brain) cancer cell lines, and showed little cytotoxicity to a normal human cell line (WI-38). In phenotypic assays, we identified activities in the extracts that target cell death, cell cycle and cell adhesion. These data highlight the anti-cancer potential of previously untested plants found in northern ecological zones and the feasibility of using pertinent phenotypic assays to examine the anti-cancer potential of natural product extracts.