Publications by authors named "Catherine Kettleborough"

22 Publications

  • Page 1 of 1

Fragment-based target screening as an empirical approach to prioritising targets: a case study on antibacterials.

Drug Discov Today 2020 Sep 10. Epub 2020 Sep 10.

Centre for Therapeutics Discovery, LifeArc, Accelerator Building, Open Innovation Campus, Stevenage, SG1 2FX, UK. Electronic address:

Here, we describe a novel workflow combining informatic and experimental approaches to enable evidence-based prioritising of targets from large sets in parallel. High-throughput protein production and biophysical fragment screening is used to identify those targets that are tractable and ligandable. As proof of concept we have applied this to a set of antibacterial targets comprising 146 essential genes. Of these targets, 51 were selected and 38 delivered results that allowed us to rank them by ligandability. The data obtained against these derisked targets have enabled rapid progression into structurally enabled drug discovery projects, demonstrating the practical value of the fragment-based target screening workflow.
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http://dx.doi.org/10.1016/j.drudis.2020.09.003DOI Listing
September 2020

Patient-derived explants (PDEs) as a powerful preclinical platform for anti-cancer drug and biomarker discovery.

Br J Cancer 2020 03 2;122(6):735-744. Epub 2020 Jan 2.

Leicester Cancer Research Centre, University of Leicester, Clinical Sciences Building, Leicester, LE2 7LX, UK.

Preclinical models that can accurately predict outcomes in the clinic are much sought after in the field of cancer drug discovery and development. Existing models such as organoids and patient-derived xenografts have many advantages, but they suffer from the drawback of not contextually preserving human tumour architecture. This is a particular problem for the preclinical testing of immunotherapies, as these agents require an intact tumour human-specific microenvironment for them to be effective. In this review, we explore the potential of patient-derived explants (PDEs) for fulfilling this need. PDEs involve the ex vivo culture of fragments of freshly resected human tumours that retain the histological features of original tumours. PDE methodology for anti-cancer drug testing has been in existence for many years, but the platform has not been widely adopted in translational research facilities, despite strong evidence for its clinical predictivity. By modifying PDE endpoint analysis to include the spatial profiling of key biomarkers by using multispectral imaging, we argue that PDEs offer many advantages, including the ability to correlate drug responses with tumour pathology, tumour heterogeneity and changes in the tumour microenvironment. As such, PDEs are a powerful model of choice for cancer drug and biomarker discovery programmes.
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http://dx.doi.org/10.1038/s41416-019-0672-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7078311PMC
March 2020

Potent bicyclic inhibitors of malarial cGMP-dependent protein kinase: approaches to combining improvements in cell potency, selectivity and structural novelty.

Bioorg Med Chem Lett 2019 10 9;29(19):126610. Epub 2019 Aug 9.

Centre for Therapeutics Discovery, LifeArc, Accelerator Building, Open Innovation Campus, Stevenage SG1 2FX, UK.

Focussed studies on imidazopyridine inhibitors of Plasmodium falciparum cyclic GMP-dependent protein kinase (PfPKG) have significantly advanced the series towards desirable in vitro property space. LLE-based approaches towards combining improvements in cell potency, key physicochemical parameters and structural novelty are described, and a structure-based design hypothesis relating to substituent regiochemistry has directed efforts towards key examples with well-balanced potency, ADME and kinase selectivity profiles.
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http://dx.doi.org/10.1016/j.bmcl.2019.08.014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6857626PMC
October 2019

Are academic drug discovery efforts receiving more recognition with declining industry efficiency?

Expert Opin Drug Discov 2019 07 26;14(7):605-607. Epub 2019 Mar 26.

b Faculty of Medicine , National Heart & Lung Institute, Imperial College , London , UK.

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http://dx.doi.org/10.1080/17460441.2019.1596080DOI Listing
July 2019

Potent inhibitors of malarial P. Falciparum protein kinase G: Improving the cell activity of a series of imidazopyridines.

Bioorg Med Chem Lett 2019 02 20;29(3):509-514. Epub 2018 Nov 20.

Centre for Therapeutics Discovery, LifeArc, Accelerator Building, Open Innovation Campus, Stevenage SG1 2FX, UK.

Development of a class of bicyclic inhibitors of the Plasmodium falciparum cyclic GMP-dependent protein kinase (PfPKG), starting from known compounds with activity against a related parasite PKG orthologue, is reported. Examination of key sub-structural elements led to new compounds with good levels of inhibitory activity against the recombinant kinase and in vitro activity against the parasite. Key examples were shown to possess encouraging in vitro ADME properties, and computational analysis provided valuable insight into the origins of the observed activity profiles.
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http://dx.doi.org/10.1016/j.bmcl.2018.11.039DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6355318PMC
February 2019

Design of the LifeArc Index Set and Retrospective Review of Its Performance: A Collection for Sharing.

SLAS Discov 2019 03 5;24(3):332-345. Epub 2018 Oct 5.

1 LifeArc, Centre for Therapeutic Discovery, Stevenage, UK.

Building, curating, and maintaining a compound collection is an expensive operation, beyond the scope of most academic organizations. Here we describe the selection criteria used to compile the LifeArc diversity set from commercial suppliers and the process we undertook to generate our representative LifeArc index set. The aim was to avoid a "junk in, junk out" screen collection to increase chemical tractability going forward, while maximizing diversity. Using historical LifeArc screening data, we demonstrate that the index set was predictive of ligandability and that progressable hits could be identified by mining associated clusters within our larger diversity set. Indeed, a higher percentage of index-derived hit clusters were found to have been progressed into hit-to-lead programs, reflecting better drug-likeness. In practice, the library has been shared widely with academic groups and used routinely within LifeArc to assess the ligandability of novel targets. Its small size is well suited to meet the needs of medium-throughput screening in labs with either limited automation, limited precious or expensive reagents, or complex cellular assays. The strategy of screening a small set in combination with rapid hit analog follow-up has demonstrated the utility of finding active clusters for potential development against challenging targets.
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http://dx.doi.org/10.1177/2472555218803696DOI Listing
March 2019

Trisubstituted thiazoles as potent and selective inhibitors of Plasmodium falciparum protein kinase G (PfPKG).

Bioorg Med Chem Lett 2018 10 27;28(19):3168-3173. Epub 2018 Aug 27.

LifeArc, Accelerator Building, Open Innovation Campus, Stevenage SG1 2FX, UK.

A series of trisubstituted thiazoles have been identified as potent inhibitors of Plasmodium falciparum (Pf) cGMP-dependent protein kinase (PfPKG) through template hopping from known Eimeria PKG (EtPKG) inhibitors. The thiazole series has yielded compounds with improved potency, kinase selectivity and good in vitro ADME properties. These compounds could be useful tools in the development of new anti-malarial drugs in the fight against drug resistant malaria.
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http://dx.doi.org/10.1016/j.bmcl.2018.08.028DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6193536PMC
October 2018

Terbinafine is a novel and selective activator of the two-pore domain potassium channel TASK3.

Biochem Biophys Res Commun 2017 11 5;493(1):444-450. Epub 2017 Sep 5.

LifeArc, Accelerator Building, Open Innovation Campus, Stevenage, SG1 2FX, UK.

Two-pore domain potassium channels (K2Ps) are characterized by their four transmembrane domain and two-pore topology. They carry background (or leak) potassium current in a variety of cell types. Despite a number of important roles there is currently a lack of pharmacological tools with which to further probe K2P function. We have developed a cell-based thallium flux assay, using baculovirus delivered TASK3 (TWIK-related acid-sensitive K channel 3, KCNK9, K2P9.1) with the aim of identifying novel, selective TASK3 activators. After screening a library of 1000 compounds, including drug-like and FDA approved molecules, we identified Terbinafine as an activator of TASK3. In a thallium flux assay a pEC50 of 6.2 ( ±0.12) was observed. When Terbinafine was screened against TASK2, TREK2, THIK1, TWIK1 and TRESK no activation was observed in thallium flux assays. Several analogues of Terbinafine were also purchased and structure activity relationships examined. To confirm Terbinafine's activation of TASK3 whole cell patch clamp electrophysiology was carried out and clear potentiation observed in both the wild type channel and the pathophysiological, Birk-Barel syndrome associated, G236R TASK3 mutant. No activity at TASK1 was observed in electrophysiology studies. In conclusion, we have identified the first selective activator of the two-pore domain potassium channel TASK3.
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http://dx.doi.org/10.1016/j.bbrc.2017.09.002DOI Listing
November 2017

A potent series targeting the malarial cGMP-dependent protein kinase clears infection and blocks transmission.

Nat Commun 2017 09 5;8(1):430. Epub 2017 Sep 5.

LifeArc, Accelerator Building, Open Innovation Campus, Stevenage, SG1 2FX, UK.

To combat drug resistance, new chemical entities are urgently required for use in next generation anti-malarial combinations. We report here the results of a medicinal chemistry programme focused on an imidazopyridine series targeting the Plasmodium falciparum cyclic GMP-dependent protein kinase (PfPKG). The most potent compound (ML10) has an IC of 160 pM in a PfPKG kinase assay and inhibits P. falciparum blood stage proliferation in vitro with an EC of 2.1 nM. Oral dosing renders blood stage parasitaemia undetectable in vivo using a P. falciparum SCID mouse model. The series targets both merozoite egress and erythrocyte invasion, but crucially, also blocks transmission of mature P. falciparum gametocytes to Anopheles stephensi mosquitoes. A co-crystal structure of PvPKG bound to ML10, reveals intimate molecular contacts that explain the high levels of potency and selectivity we have measured. The properties of this series warrant consideration for further development to produce an antimalarial drug.Protein kinases are promising drug targets for treatment of malaria. Here, starting with a medicinal chemistry approach, Baker et al. generate an imidazopyridine that selectively targets Plasmodium falciparum PKG, inhibits blood stage parasite growth in vitro and in mice and blocks transmission to mosquitoes.
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http://dx.doi.org/10.1038/s41467-017-00572-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5585294PMC
September 2017

Structure of a Potential Therapeutic Antibody Bound to Interleukin-16 (IL-16): MECHANISTIC INSIGHTS AND NEW THERAPEUTIC OPPORTUNITIES.

J Biol Chem 2016 08 26;291(32):16840-8. Epub 2016 May 26.

From the Department of Molecular and Cell Biology, Henry Wellcome Building, University of Leicester, Leicester, LE1 9HN, United Kingdom,

Interleukin-16 (IL-16) is reported to be a chemoattractant cytokine and modulator of T-cell activation, and has been proposed as a ligand for the co-receptor CD4. The secreted active form of IL-16 has been detected at sites of TH1-mediated inflammation, such as those seen in autoimmune diseases, ischemic reperfusion injury (IRI), and tissue transplant rejection. Neutralization of IL-16 recruitment to its receptor, using an anti-IL16 antibody, has been shown to significantly attenuate inflammation and disease pathology in IRI, as well as in some autoimmune diseases. The 14.1 antibody is a monoclonal anti-IL-16 antibody, which when incubated with CD4(+) cells is reported to cause a reduction in the TH1-type inflammatory response. Secreted IL-16 contains a characteristic PDZ domain. PDZ domains are typically characterized by a defined globular structure, along with a peptide-binding site located in a groove between the αB and βB structural elements and a highly conserved carboxylate-binding loop. In contrast to other reported PDZ domains, the solution structure previously reported for IL-16 reveals a tryptophan residue obscuring the recognition groove. We have solved the structure of the 14.1Fab fragment in complex with IL-16, revealing that binding of the antibody requires a conformational change in the IL-16 PDZ domain. This involves the rotation of the αB-helix, accompanied movement of the peptide groove obscuring tryptophan residue, and consequent opening up of the binding site for interaction. Our study reveals a surprising mechanism of action for the antibody and identifies new opportunities for the development of IL-16-targeted therapeutics, including small molecules that mimic the interaction of the antibody.
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http://dx.doi.org/10.1074/jbc.M115.709303DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4974395PMC
August 2016

A High-Throughput Electrophysiology Assay Identifies Inhibitors of the Inwardly Rectifying Potassium Channel Kir7.1.

J Biomol Screen 2015 Jul 5;20(6):739-47. Epub 2015 Feb 5.

MRC Technology, Center for Therapeutics Discovery, London, UK.

Kir7.1 is an inwardly rectifying potassium channel that has been implicated in controlling the resting membrane potential of the myometrium. Abnormal uterine activity in pregnancy plays an important role in postpartum hemorrhage, and novel therapies for this condition may lie in manipulation of membrane potential. This work presents an assay development and screening strategy for identifying novel inhibitors of Kir7.1. A cell-based automated patch-clamp electrophysiology assay was developed using the IonWorks Quattro (Molecular Devices, Sunnyvale, CA) system, and the iterative optimization is described. In total, 7087 compounds were tested, with a hit rate (>40% inhibition) of 3.09%. During screening, average Z' values of 0.63 ± 0.09 were observed. After chemistry triage, lead compounds were resynthesized and activity confirmed by IC50 determinations. The most potent compound identified (MRT00200769) gave rise to an IC50 of 1.3 µM at Kir7.1. Compounds were assessed for selectivity using the inwardly rectifying potassium channel Kir1.1 (ROMK) and hERG (human Ether-à-go-go Related Gene). Pharmacological characterization of known Kir7.1 inhibitors was also carried out and analogues of VU590 tested to assess selectivity at Kir7.1.
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http://dx.doi.org/10.1177/1087057115569156DOI Listing
July 2015

The inwardly rectifying K+ channel KIR7.1 controls uterine excitability throughout pregnancy.

EMBO Mol Med 2014 Sep;6(9):1161-74

Division of Reproductive Health, Clinical Sciences Research Laboratories, Warwick Medical School University of Warwick, Coventry, UK

Abnormal uterine activity in pregnancy causes a range of important clinical disorders, including preterm birth, dysfunctional labour and post-partum haemorrhage. Uterine contractile patterns are controlled by the generation of complex electrical signals at the myometrial smooth muscle plasma membrane. To identify novel targets to treat conditions associated with uterine dysfunction, we undertook a genome-wide screen of potassium channels that are enriched in myometrial smooth muscle. Computational modelling identified Kir7.1 as potentially important in regulating uterine excitability during pregnancy. We demonstrate Kir7.1 current hyper-polarizes uterine myocytes and promotes quiescence during gestation. Labour is associated with a decline, but not loss, of Kir7.1 expression. Knockdown of Kir7.1 by lentiviral expression of miRNA was sufficient to increase uterine contractile force and duration significantly. Conversely, overexpression of Kir7.1 inhibited uterine contractility. Finally, we demonstrate that the Kir7.1 inhibitor VU590 as well as novel derivative compounds induces profound, long-lasting contractions in mouse and human myometrium; the activity of these inhibitors exceeds that of other uterotonic drugs. We conclude Kir7.1 regulates the transition from quiescence to contractions in the pregnant uterus and may be a target for therapies to control uterine contractility.
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http://dx.doi.org/10.15252/emmm.201403944DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4197863PMC
September 2014

Cloxyquin (5-chloroquinolin-8-ol) is an activator of the two-pore domain potassium channel TRESK.

Biochem Biophys Res Commun 2013 Nov;441(2):463-8

TRESK is a two-pore domain potassium channel. Loss of function mutations have been linked to typical migraine with aura and due to TRESK’s expression pattern and role in neuronal excitability it represents a promising therapeutic target. We developed a cell based assay using baculovirus transduced U20S cells to screen for activators of TRESK. Using a thallium flux system to measure TRESK channel activity we identified Cloxyquin as a novel activator. Cloxyquin was shown to have an EC50 of 3.8 μM in the thallium assay and displayed good selectivity against other potassium channels tested. Activity was confirmed using whole cell patch electrophysiology, with Cloxyquin causing a near two fold increase in outward current. The strategy presented here will be used to screen larger compound libraries with the aim of identifying novel chemical series which may be developed into new migraine prophylactics.
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November 2013

A Casein kinase 1/Checkpoint kinase 1 pyrazolo-pyridine protein kinase inhibitor as novel activator of the p53 pathway.

Bioorg Med Chem Lett 2013 Oct 16;23(20):5578-85. Epub 2013 Aug 16.

p53 Signal Transduction Group, University of Edinburgh Cancer Research Centre in the Institute of Genetics and Molecular Medicine, Crewe Road South, Edinburgh EH4 2XR, United Kingdom.

Reactivation of the wild-type p53 pathway is one key goal aimed at developing targeted therapeutics in the cancer research field. Although most p53 protein kinases form 'p53-activating' signals, there are few kinases whose action can contribute to the inhibition of p53, as Casein kinase 1 (CK1) and Checkpoint kinase 1 (CHK1). Here we report on a pyrazolo-pyridine analogue showing activity against both CK1 and CHK1 kinases that lead to p53 pathway stabilisation, thus having pharmacological similarities to the p53-activator Nutlin-3. These data demonstrate the emerging potential utility of multivalent kinase inhibitors.
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http://dx.doi.org/10.1016/j.bmcl.2013.08.046DOI Listing
October 2013

Identification of small-molecule inhibitors of the ribonuclease H2 enzyme.

J Biomol Screen 2013 Jun 20;18(5):610-20. Epub 2013 Feb 20.

MRC Human Genetics Unit, MRC IGMM, University of Edinburgh, Edinburgh, UK.

Ribonuclease H2 (RNase H2) is a nuclease that specifically hydrolyzes RNA residues in RNA-DNA hybrids. Mutations in the RNase H2 enzyme complex have been identified in the genetic disorder Aicardi-Goutières syndrome (AGS), which has similarities to the autoimmune disease systemic lupus eryrthrematosis (SLE). The RNase H2 enzyme has also been recently implicated as a key genome surveillance enzyme. Therefore, small-molecule modulators of RNase H2 activity may have utility in therapeutics and as tools to investigate the cellular functions of RNase H2. A fluorescent quench assay, measuring cleavage of an RNA-DNA duplex substrate by recombinant RNase H2, was developed into a high-throughput format and used to screen a 48 560 compound library. A hit validation strategy was subsequently employed, leading to the identification of two novel inhibitor compounds with in vitro nanomolar range inhibition of RNase H2 activity and >100-fold selectivity compared with RNase H type 1. These compounds are the first small-molecule inhibitors of RNase H2 to be reported. They and their derivatives should provide the basis for the development of tool compounds investigating the cellular functions of the RNase H2 enzyme, and, potentially, for pharmacological manipulation of nucleic acid-mediated immune responses.
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http://dx.doi.org/10.1177/1087057113476550DOI Listing
June 2013

Screening β-arrestin recruitment for the identification of natural ligands for orphan G-protein-coupled receptors.

J Biomol Screen 2013 Jun 8;18(5):599-609. Epub 2013 Feb 8.

Medical Research Council Technology, Centre for Therapeutic Discovery, London, UK.

A variety of G-protein-coupled receptor (GPCR) screening technologies have successfully partnered a number of GPCRs with their cognate ligands. GPCR-mediated β-arrestin recruitment is now recognized as a distinct intracellular signaling pathway, and ligand-receptor interactions may show a bias toward β-arrestin over classical GPCR signaling pathways. We hypothesized that the failure to identify native ligands for the remaining orphan GPCRs may be a consequence of biased β-arrestin signaling. To investigate this, we assembled 10 500 candidate ligands and screened 82 GPCRs using PathHunter β-arrestin recruitment technology. High-quality screening assays were validated by the inclusion of liganded receptors and the detection and confirmation of these established ligand-receptor pairings. We describe a candidate endogenous orphan GPCR ligand and a number of novel surrogate ligands. However, for the majority of orphan receptors studied, measurement of β-arrestin recruitment did not lead to the identification of cognate ligands from our screening sets. β-Arrestin recruitment represents a robust GPCR screening technology, and ligand-biased signaling is emerging as a therapeutically exploitable feature of GPCR biology. The identification of cognate ligands for the orphan GPCRs and the extent to which receptors may exist to preferentially signal through β-arrestin in response to their native ligand remain to be determined.
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http://dx.doi.org/10.1177/1087057113475480DOI Listing
June 2013

A high-throughput assay for modulators of NNT activity in permeabilized yeast cells.

J Biomol Screen 2011 Aug 20;16(7):734-43. Epub 2011 May 20.

Medical Research Council, Mammalian Genetics Unit, Harwell Science and Innovation Campus, Oxfordshire, United Kingdom.

Nicotinamide nucleotide transhydrogenase (NNT) mutant mice show glucose intolerance with impaired insulin secretion during glucose tolerance tests. Uncoupling of the β cell mitochondrial metabolism due to such mutations makes NNT a novel target for therapeutics in the treatment of pathologies such as type 2 diabetes. The authors propose that increasing NNT activity would help reduce deleterious buildup of reactive oxygen species in the inner mitochondrial matrix. They have expressed human Nnt cDNA for the first time in Saccharomyces cerevisiae, and transhydrogenase activity in mitochondria isolated from these cells is six times greater than is seen in wild-type mitochondria. The same mitochondria have partially uncoupled respiration, and the cells have slower growth rates compared to cells that do not express NNT. The authors have used NNT's role as a redox-driven proton pump to develop a robust fluorimetric assay in permeabilized yeast. Screening in parallel a library of known pharmacologically active compounds (National Institute of Neurological Disorders and Stroke collection) against NNT ± cells, they demonstrate a robust and reproducible assay suitable for expansion into larger and more diverse compound sets. The identification of NNT activators may help in the elucidation of the role of NNT in mammalian cells and assessing its potential as a therapeutic target for insulin secretion disorders.
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http://dx.doi.org/10.1177/1087057111408088DOI Listing
August 2011

Effective inhibitors of the essential kinase PknB and their potential as anti-mycobacterial agents.

Tuberculosis (Edinb) 2011 Jul 11;91(4):277-86. Epub 2011 Apr 11.

Division of Mycobacterial Research, MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London, NW7 1AA, United Kingdom.

PknB is an essential serine/threonine kinase of Mycobacterium tuberculosis with possible roles in a number of signalling pathways involved in cell division and metabolism. We screened a library of >50,000 compounds for inhibitors of the in vitro phosphorylation of GarA (Rv1827) by PknB and identified a number of inhibitors. A program of synthetic medicinal chemistry was subsequently conducted around one class of inhibitors and was successful in generating ATP competitive inhibitors with potency in the nanomolar range. Compounds in this class showed cross-reactivity with the related M. tuberculosis kinase, PknF, but not with PknG in an in vitro autophosphorylation assay. These synthesised inhibitors were able to prevent the growth of M. tuberculosis in an Alamar blue assay and in an intracellular model of infection, but only in the micromolar range. We attempted to determine if cell wall permeability was an explanation for the discrepancy between the potent in vitro compared with relatively poor in vivo activity, but found no evidence that the activity of the inhibitors could be improved by weakening the cell wall. Despite a number of drug discovery efforts attempting to develop inhibitors against PknB, it is yet to be reported that any such inhibitors prevent mycobacterial growth at submicromolar concentrations.
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http://dx.doi.org/10.1016/j.tube.2011.03.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3158675PMC
July 2011

Subcellular discharge of a serine protease mediates release of invasive malaria parasites from host erythrocytes.

Cell 2007 Dec;131(6):1072-83

Division of Parasitology, National Institute for Medical Research, Mill Hill, London NW7 1AA, UK.

The most virulent form of malaria is caused by waves of replication of blood stages of the protozoan pathogen Plasmodium falciparum. The parasite divides within an intraerythrocytic parasitophorous vacuole until rupture of the vacuole and host-cell membranes releases merozoites that invade fresh erythrocytes to repeat the cycle. Despite the importance of merozoite egress for disease progression, none of the molecular factors involved are known. We report that, just prior to egress, an essential serine protease called PfSUB1 is discharged from previously unrecognized parasite organelles (termed exonemes) into the parasitophorous vacuole space. There, PfSUB1 mediates the proteolytic maturation of at least two essential members of another enzyme family called SERA. Pharmacological blockade of PfSUB1 inhibits egress and ablates the invasive capacity of released merozoites. Our findings reveal the presence in the malarial parasitophorous vacuole of a regulated, PfSUB1-mediated proteolytic processing event required for release of viable parasites from the host erythrocyte.
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http://dx.doi.org/10.1016/j.cell.2007.10.049DOI Listing
December 2007

Academia-industry partnerships in drug discovery.

Expert Opin Drug Discov 2006 Jun;1(1):1-6

Medical Research Council Technology, 20 Park Crescent, London W1B 1AL, UK.

The movement of ideas and innovation from academia into the world of business has a long and fruitful history. Ironically, it might be argued that the recent pressure put on universities and basic research organisations to protect and exploit their intellectual property has, in many ways, created a less conducive environment to successful commercialisation than existed 30 years ago. This movement has been concurrent with the drift of the Pharmaceutical industry towards a more risk-averse R&D strategy in which it has increasingly concentrated its resources on a reductionist drug discovery process and later stage clinical development. In effect, these two strategies have created a discontinuity between academic scientific output and industry at a time when academia as a source of innovation is perhaps more important to industry than ever.
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http://dx.doi.org/10.1517/17460441.1.1.1DOI Listing
June 2006

Suramin and suramin analogues inhibit merozoite surface protein-1 secondary processing and erythrocyte invasion by the malaria parasite Plasmodium falciparum.

J Biol Chem 2003 Nov 17;278(48):47670-7. Epub 2003 Sep 17.

Medical Research Council Technology, 1-3 Burtonhole Lane, Mill Hill, London NW7 1AD, United Kingdom.

Malarial merozoites invade erythrocytes; and as an essential step in this invasion process, the 42-kDa fragment of Plasmodium falciparum merozoite surface protein-1 (MSP142) is further cleaved to a 33-kDa N-terminal polypeptide (MSP133) and an 19-kDa C-terminal fragment (MSP119) in a secondary processing step. Suramin was shown to inhibit both merozoite invasion and MSP142 proteolytic cleavage. This polysulfonated naphthylurea bound directly to recombinant P. falciparum MSP142 (Kd = 0.2 microM) and to Plasmodium vivax MSP142 (Kd = 0.3 microM) as measured by fluorescence enhancement in the presence of the protein and by isothermal titration calorimetry. Suramin bound only slightly less tightly to the P. vivax MSP133 (Kd = 1.5 microM) secondary processing product (fluorescence measurements), but very weakly to MSP119 (Kd approximately 15 mM) (NMR measurements). Several residues in MSP119 were implicated in the interaction with suramin using NMR measurements. A series of symmetrical suramin analogues that differ in the number of aromatic rings and substitution patterns of the terminal naphthylamine groups was examined in invasion and processing assays. Two classes of analogue with either two or four bridging rings were found to be active in both assays, whereas two other classes without bridging rings were inactive. We propose that suramin and related compounds inhibit erythrocyte invasion by binding to MSP1 and by preventing its cleavage by the secondary processing protease. The results indicate that enzymatic events during invasion are suitable targets for drug development and validate the novel concept of an inhibitor binding to a macromolecular substrate to prevent its proteolysis by a protease.
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http://dx.doi.org/10.1074/jbc.M306603200DOI Listing
November 2003

A single malaria merozoite serine protease mediates shedding of multiple surface proteins by juxtamembrane cleavage.

J Biol Chem 2003 Jun 9;278(26):23890-8. Epub 2003 Apr 9.

Division of Protein Structure, National Institute for Medical Research, Mill Hill, London NW7 1AA, United Kingdom.

Erythrocyte invasion by the malaria merozoite is accompanied by the regulated discharge of apically located secretory organelles called micronemes. Plasmodium falciparum apical membrane antigen-1 (PfAMA-1), which plays an indispensable role in invasion, translocates from micronemes onto the parasite surface and is proteolytically shed in a soluble form during invasion. We have previously proposed, on the basis of incomplete mass spectrometric mapping data, that PfAMA-1 shedding results from cleavage at two alternative positions. We now show conclusively that the PfAMA-1 ectodomain is shed from the merozoite solely as a result of cleavage at a single site, just 29 residues away from the predicted transmembrane-spanning sequence. Remarkably, this cleavage is mediated by the same membrane-bound parasite serine protease as that responsible for shedding of the merozoite surface protein-1 (MSP-1) complex, an abundant, glycosylphosphatidylinositol-anchored multiprotein complex. Processing of MSP-1 is essential for invasion. Our results indicate the presence on the merozoite surface of a multifunctional serine sheddase with a broad substrate specificity. We further demonstrate that translocation and shedding of PfAMA-1 is an actin-independent process.
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http://dx.doi.org/10.1074/jbc.M302160200DOI Listing
June 2003