Regulation Mechanisms for Phospholipase Enzymes

The effect of hydrophobicity on susceptibility of phosphatidylcholine derivatives to PLA2 attack was studied by synthesising two series of compounds, the saturated symmetrically distributed derivatives and compounds with one long acyl-chain in the first position and a selected short-chain in the second position. The first series were used to investigate the effect of substrate morphology over the range from free monomer substrates through micelle to bilayer forms, the second series were used to examine the region of the micelle/bilayer transition at higher resolution. The symmetric substrates showed the expected properties with susceptibility increasing with hydrophobicity in the free monomer series and a sharp transition seen at the CMC for the shorter chain substrates. No such change was seen for longer chain substrates with any of these enzymes and the concept of a hydrophobic anchor increasing the rate of attack on condensed rather than monomeric substrates was questioned. These compounds were used to study the action of enzyme activated by treatment with oleoyl-imidazolide. The biggest activation factors were seen for asymmetric bilayer-forming substrates in propanolic solution, but the physico-chemical form of the substrates under these conditions was not established. Fatty acyl activation was found to alter the response to calcium activation and suggested a two-calcium site model. Studies of calcium activation showed very strong evidence for two kinetically important sites. Metal ion inhibition showed that barium and large cations were competitive inhibitors for calcium, but zinc and cadmium were not and appeared to inhibit a component of activation only found at high calcium activation. This lead to the proposal that zinc and barium bind to the enzyme at different calcium binding sites. Hydrolysis curves were shown to vary in shape depending on calcium concentration and the anomalous shape was associated with the presence of calcium at a single binding site. Addition of zinc removed the anomalous shape and without giving further enzyme activation whilst addition of calcium changes the curve shape and was activating. Some evidence was presented to suggest that the presence of a metal ion in the second (zinc) site was important for modulating the activation of the enzyme with surfaces. The use of the conductimetric assay was extended to the purification and characterisation of PLD enzymes acting as both transferases and hydrolases The transferase activity was used to generate phosphatidyl alcohols from DiC8PC and the methanol derivative was shown to be better substrate than the PC equivalent but to posess chartacteristics of the monomeric form. Polar phosphatidic acid compounds which should have high CMC values sould enable the relationship between structure, morphology and susceptibility to PLA2 to be examined in detail

A fully automated procedure for the parallel, multidimensional purification and nucleotide loading of the human GTPases KRas, Rac1 and RalB

Small GTPases regulate many key cellular processes and their role in human disease validates many proteins in this class as desirable targets for therapeutic intervention. Reliable recombinant production of GTPases, often in the active GTP loaded state, is a prerequisite for the prosecution of drug discovery efforts. The preparation of these active forms can be complex and often constricts the supply to the reagent intensive techniques used in structure base drug discovery. We have established a fully automated, multidimensional protein purification strategy for the parallel production of the catalytic G-domains of KRas, Rac1 and RalB GTPases in the active form. This method incorporates a four step chromatography purification with TEV protease-mediated affinity tag cleavage and a conditioning step that achieves the activation of the GTPase by exchanging GDP for the non-hydrolyzable GTP analogue GMPPnP. We also demonstrate that an automated method is efficient at loading of KRas with mantGDP for application in a SOS1 catalysed fluorescent nucleotide exchange assay. In comparison to more conventional manual workflows the automated method offers marked advantages in method run time and operator workload. This reduces the bottleneck in protein production while generating products that are highly purified and effectively loaded with nucleotide analogues

The Meisenheimer complex as a paradigm in drug discovery: reversible covalent inhibition through C67 of the ATP binding site of PLK1

The polo kinase family are important oncology targets that act in regulating entry into and progression through mitosis. Structure-guided discovery of a new class of inhibitors of Polo-like kinase 1 (PLK1) catalytic activity that interact with Cys67 of the ATP binding site is described. Compounds containing the benzothiazole N-oxide scaffold not only bind covalently to this residue, but are reversible inhibitors through the formation of Meisenheimer complexes. This mechanism of kinase inhibition results in compounds that can target PLK1 with high selectivity, while avoiding issues with irreversible covalent binding and interaction with other thiol-containing molecules in the cell. Due to renewed interest in covalent drugs and the plethora of potential drug targets, these represent prototypes for the design of kinase inhibitory compounds that achieve high specificity through covalent interaction and yet still bind reversibly to the ATP cleft, a strategy that could be applied to avoid issues with conventional covalent binders

5-deazaflavin derivatives as inhibitors of p53 ubiquitination by HDM2

Based on previous reports of certain 5-deazaflavin derivatives being capable of activating the tumour suppressor p53 in cancer cells through inhibition of the p53-specific ubiquitin E3 ligase HDM2, we have conducted an structure–activity relationship (SAR) analysis through systematic modification of the 5-deazaflavin template. This analysis shows that HDM2-inhibitory activity depends on a combination of factors. The most active compounds (e.g., 15) contain a trifluoromethyl or chloro substituent at the deazaflavin C9 position and this activity depends to a large extent on the presence of at least one additional halogen or methyl substituent of the phenyl group at N10. Our SAR results, in combination with the HDM2 RING domain receptor recognition model we present, form the basis for the design of drug-like and potent activators of p53 for potential cancer therapy

Structure-based design, synthesis and biological evaluation of a novel series of isoquinolone and pyrazolo[4,3-c]pyridine inhibitors of fascin 1 as potential anti-metastatic agents

Fascin is an actin binding and bundling protein that is not expressed in normal epithelial tissues but overexpressed in a variety of invasive epithelial tumors. It has a critical role in cancer cell metastasis by promoting cell migration and invasion. Here we report the crystal structures of fascin in complex with a series of novel and potent inhibitors. Structure-based elaboration of these compounds enabled the development of a series with nanomolar affinities for fascin, good physicochemical properties and the ability to inhibit fascin-mediated bundling of filamentous actin. These compounds provide promising starting points for fascin-targeted anti-metastatic therapies

Discovery and Characterization of 2-Anilino-4- (Thiazol-5-yl)Pyrimidine Transcriptional CDK Inhibitors as Anticancer Agents

The main difficulty in the development of ATP antagonist kinase inhibitors is target specificity, since the ATP-binding motif is present in many proteins. We introduce a strategy that has allowed us to identify compounds from a kinase inhibitor library that block the cyclin-dependent kinases responsible for regulating transcription, i.e., CDK7 and especially CDK9. The screening cascade employs cellular phenotypic assays based on mitotic index and nuclear p53 protein accumulation. This permitted us to classify compounds into transcriptional, cell cycle, and mitotic inhibitor groups. We describe the characterization of the transcriptional inhibitor class in terms of kinase inhibition profile, cellular mode of action, and selectivity for transformed cells. A structural selectivity rationale was used to optimize potency and biopharmaceutical properties and led to the development of a transcriptional inhibitor, 3,4-dimethyl-5-[2-(4-piperazin-1-yl-phenylamino)-pyrimidin-4-yl]-3H-thiazol-2-one, with anticancer activity in animal models

A novel small molecule inhibitor of MRCK prevents radiation-driven invasion in glioblastoma

Glioblastoma (GBM) is an aggressive and incurable primary brain tumor that causes severe neurological, cognitive, and psychological symptoms. Symptoms are caused and exacerbated by the infiltrative properties of GBM cells, which enable them to pervade the healthy brain and disrupt normal function. Recent research has indicated that, while radiotherapy (RT) remains the most effective component of multimodality therapy for GBM patients, it can provoke a more infiltrative phenotype in GBM cells that survive treatment. Here we demonstrate an essential role of the actin-myosin regulatory kinase myotonic dystrophy kinase-related CDC42- binding kinase (MRCK) in mediating the pro-invasive effects of radiation. MRCK-mediated invasion occurred via downstream signaling to effector molecules MYPT1 and MLC2. MRCK was activated by clinically relevant doses per fraction of radiation, and this activation was concomitant with an increase in GBM cell motility and invasion. Furthermore, ablation of MRCK activity either by RNAi or by inhibition with the novel small molecule inhibitor BDP-9066 prevented radiation-driven increases in motility both in vitro and in a clinically relevant orthotopic xenograft model of GBM. Crucially, treatment with BDP-9066 in combination with RT significantly increased survival in this model and markedly reduced infiltration of the contralateral cerebral hemisphere

Colorectal tumors require NUAK1 for protection from oxidative stress

The authors wish to thank the staff of the CRUK Beatson Institute Biological Services Unit for animal husbandry and assistance with in vivo experiments; the staff of the CRUK BI Histology core facility and William Clark of the NGS core facility; David McGarry, Rene Jackstadt, Jiska Van der Reest, Justin Bower and Heather McKinnon for many helpful discussions, and countless colleagues at the CRUK BI and Glasgow Institute of Cancer Sciences for support; Prem Premsrirut & Mirimus Inc. for design and generation of dox-inducible Nuak1 shRNA expressing mice Nathanael Gray for initial provision of NUAK1 inhibitors. Funding was provided by the University of Glasgow and the CRUK Beaton Institute. J.P. was supported by European Commission Marie Curie actions C.I.G. 618448 “SERPLUC” to D.J.M.; N.M. was supported through Worldwide Cancer (formerly AICR) grant 15-0279 to O.J.S. & D.J.M.; B.K. was funded through EC Marie Curie actions mobility award 705190 “NuSiCC”; T.M. was funded through British Lung Foundation grant APHD13-5. The laboratories of S.R.Z. (A12935), O.J.S. (A21139) and M.D. (A17096) are funded by Cancer Research UK. O.J.S. was additionally supported by European Research Council grant 311301 “ColoCan”.Peer reviewedPostprin