Chemical Biology Publications 2015

Picaud S, Fedorov O, Thanasopoulou A, Leonards K, Jones K, Meier J, Olzscha H, Monteiro O, Martin S, Philpott M et al. 2015. Generation of a Selective Small Molecule Inhibitor of the CBP/p300 Bromodomain for Leukemia Therapy. Cancer Res, 75 (23), pp. 5106-5119. | Citations: 85 (Scopus) | Show Abstract | Read more

The histone acetyltransferases CBP/p300 are involved in recurrent leukemia-associated chromosomal translocations and are key regulators of cell growth. Therefore, efforts to generate inhibitors of CBP/p300 are of clinical value. We developed a specific and potent acetyl-lysine competitive protein-protein interaction inhibitor, I-CBP112, that targets the CBP/p300 bromodomains. Exposure of human and mouse leukemic cell lines to I-CBP112 resulted in substantially impaired colony formation and induced cellular differentiation without significant cytotoxicity. I-CBP112 significantly reduced the leukemia-initiating potential of MLL-AF9(+) acute myeloid leukemia cells in a dose-dependent manner in vitro and in vivo. Interestingly, I-CBP112 increased the cytotoxic activity of BET bromodomain inhibitor JQ1 as well as doxorubicin. Collectively, we report the development and preclinical evaluation of a novel, potent inhibitor targeting CBP/p300 bromodomains that impairs aberrant self-renewal of leukemic cells. The synergistic effects of I-CBP112 and current standard therapy (doxorubicin) as well as emerging treatment strategies (BET inhibition) provide new opportunities for combinatorial treatment of leukemia and potentially other cancers.

Ekambaram R, Manoharan GB, Enkvist E, Ligi K, Knapp S, Uri A. 2015. PIM kinase-responsive microsecond-lifetime photoluminescent probes based on selenium-containing heteroaromatic tricycle RSC ADVANCES, 5 (117), pp. 96750-96757. | Citations: 4 (Web of Science Lite) | Show Abstract | Read more

<p>Microsecond-lifetime binding-responsive organic photoluminescent probes for PIM kinases were developed based on selenium-comprising heteroaromatic tricycle.</p>

Müller S, Chaikuad A, Gray NS, Knapp S. 2015. The ins and outs of selective kinase inhibitor development. Nat Chem Biol, 11 (11), pp. 818-821. | Citations: 88 (Scopus) | Read more

Fedorov O, Castex J, Tallant C, Owen DR, Martin S, Aldeghi M, Monteiro O, Filippakopoulos P, Picaud S, Trzupek JD et al. 2015. Selective targeting of the BRG/PB1 bromodomains impairs embryonic and trophoblast stem cell maintenance. Sci Adv, 1 (10), pp. e1500723. | Citations: 32 (Scopus) | Show Abstract | Read more

Mammalian SWI/SNF [also called Brg/Brahma-associated factors (BAFs)] are evolutionarily conserved chromatin-remodeling complexes regulating gene transcription programs during development and stem cell differentiation. BAF complexes contain an ATP (adenosine 5'-triphosphate)-driven remodeling enzyme (either BRG1 or BRM) and multiple protein interaction domains including bromodomains, an evolutionary conserved acetyl lysine-dependent protein interaction motif that recruits transcriptional regulators to acetylated chromatin. We report a potent and cell active protein interaction inhibitor, PFI-3, that selectively binds to essential BAF bromodomains. The high specificity of PFI-3 was achieved on the basis of a novel binding mode of a salicylic acid head group that led to the replacement of water molecules typically maintained in other bromodomain inhibitor complexes. We show that exposure of embryonic stem cells to PFI-3 led to deprivation of stemness and deregulated lineage specification. Furthermore, differentiation of trophoblast stem cells in the presence of PFI-3 was markedly enhanced. The data present a key function of BAF bromodomains in stem cell maintenance and differentiation, introducing a novel versatile chemical probe for studies on acetylation-dependent cellular processes controlled by BAF remodeling complexes.

Arrowsmith CH, Audia JE, Austin C, Baell J, Bennett J, Blagg J, Bountra C, Brennan PE, Brown PJ, Bunnage ME et al. 2015. The promise and peril of chemical probes (vol 11, pg 536, 2015) NATURE CHEMICAL BIOLOGY, 11 (11), pp. 887-887. | Citations: 3 (Web of Science Lite) | Read more

Darby RAJ, Unsworth A, Knapp S, Kerr ID, Callaghan R. 2015. Overcoming ABCG2-mediated drug resistance with imidazo-[1,2-b]-pyridazine-based Pim1 kinase inhibitors. Cancer Chemother Pharmacol, 76 (4), pp. 853-864. | Citations: 4 (Web of Science Lite) | Show Abstract | Read more

PURPOSE: Multidrug efflux pumps such as ABCG2 confer drug resistance to a number of cancer types, leading to poor prognosis and outcome. To date, the strategy of directly inhibiting multidrug efflux pumps in order to overcome drug resistance in cancer has been unsuccessful. An alternative strategy is to target proteins involved in the regulation of multidrug efflux pump activity or expression. Pim1 kinase has been demonstrated to phosphorylate ABCG2, promote its oligomerisation and contribute to its ability to confer drug resistance. METHODS: In the present manuscript, imidazo-pyridazine-based inhibitors of Pim1 were examined for their ability to overcome ABCG2-mediated drug resistance. Drug efficacy was measured as a cytotoxic response or an effect on transport by ABCG2. Protein expression patterns were assessed using western immuno-blotting. RESULTS: The two Pim1 inhibitors increased the potency of flavopiridol, mitoxantrone, topotecan and doxorubicin, specifically in ABCG2-expressing cells. This effect was associated with an increase in the cellular accumulation of [(3)H]-mitoxantrone, suggesting direct impairment of the transporter. However, prolonged pre-incubation with the studied inhibitors greatly enhanced the effect on mitoxantrone accumulation. The inhibitors caused a significant time-dependent reduction in the expression of ABCG2 in the resistant cells, an effect that would improve drug efficacy. CONCLUSION: Consequently, it appears that the Pim1 inhibitors display a dual-mode effect on ABCG2-expressing cancer cells. This may provide a powerful new strategy in overcoming drug resistance by targeting proteins that regulate expression of efflux pumps.

Arrowsmith CH, Audia JE, Austin C, Baell J, Bennett J, Blagg J, Bountra C, Brennan PE, Brown PJ, Bunnage ME et al. 2015. Corrigendum: The promise and peril of chemical probes. Nat Chem Biol, 11 (11), pp. 887. | Citations: 4 (European Pubmed Central) | Read more

Huber KVM, Olek KM, Müller AC, Tan CSH, Bennett KL, Colinge J, Superti-Furga G. 2015. Proteome-wide drug and metabolite interaction mapping by thermal-stability profiling. Nat Methods, 12 (11), pp. 1055-1057. | Citations: 59 (Scopus) | Show Abstract | Read more

Thermal stabilization of proteins after ligand binding provides an efficient means to assess the binding of small molecules to proteins. We show here that in combination with quantitative mass spectrometry, the approach allows for the systematic survey of protein engagement by cellular metabolites and drugs. We profiled the targets of the drugs methotrexate and (S)-crizotinib and the metabolite 2'3'-cGAMP in intact cells and identified the 2'3'-cGAMP cognate transmembrane receptor STING, involved in immune signaling.

Grebien F, Vedadi M, Getlik M, Giambruno R, Grover A, Avellino R, Skucha A, Vittori S, Kuznetsova E, Smil D et al. 2015. Erratum: Pharmacological targeting of the Wdr5-MLL interaction in C/EBPα N-terminal leukemia. Nat Chem Biol, 11 (10), pp. 815. | Read more

Rouka E, Simister PC, Janning M, Kumbrink J, Konstantinou T, Muniz JRC, Joshi D, O'Reilly N, Volkmer R, Ritter B et al. 2015. Differential Recognition Preferences of the Three Src Homology 3 (SH3) Domains from the Adaptor CD2-associated Protein (CD2AP) and Direct Association with Ras and Rab Interactor 3 (RIN3). J Biol Chem, 290 (42), pp. 25275-25292. | Citations: 11 (Scopus) | Show Abstract | Read more

CD2AP is an adaptor protein involved in membrane trafficking, with essential roles in maintaining podocyte function within the kidney glomerulus. CD2AP contains three Src homology 3 (SH3) domains that mediate multiple protein-protein interactions. However, a detailed comparison of the molecular binding preferences of each SH3 remained unexplored, as well as the discovery of novel interactors. Thus, we studied the binding properties of each SH3 domain to the known interactor Casitas B-lineage lymphoma protein (c-CBL), conducted a peptide array screen based on the recognition motif PxPxPR and identified 40 known or novel candidate binding proteins, such as RIN3, a RAB5-activating guanine nucleotide exchange factor. CD2AP SH3 domains 1 and 2 generally bound with similar characteristics and specificities, whereas the SH3-3 domain bound more weakly to most peptide ligands tested yet recognized an unusually extended sequence in ALG-2-interacting protein X (ALIX). RIN3 peptide scanning arrays revealed two CD2AP binding sites, recognized by all three SH3 domains, but SH3-3 appeared non-functional in precipitation experiments. RIN3 recruited CD2AP to RAB5a-positive early endosomes via these interaction sites. Permutation arrays and isothermal titration calorimetry data showed that the preferred binding motif is Px(P/A)xPR. Two high-resolution crystal structures (1.65 and 1.11 Å) of CD2AP SH3-1 and SH3-2 solved in complex with RIN3 epitopes 1 and 2, respectively, indicated that another extended motif is relevant in epitope 2. In conclusion, we have discovered novel interaction candidates for CD2AP and characterized subtle yet significant differences in the recognition preferences of its three SH3 domains for c-CBL, ALIX, and RIN3.

Hammitzsch A, Tallant C, Fedorov O, O'Mahony A, Brennan PE, Hay DA, Martinez FO, Al-Mossawi MH, de Wit J, Vecellio M et al. 2015. CBP30, a selective CBP/p300 bromodomain inhibitor, suppresses human Th17 responses. Proc Natl Acad Sci U S A, 112 (34), pp. 10768-10773. | Citations: 74 (Web of Science Lite) | Show Abstract | Read more

Th17 responses are critical to a variety of human autoimmune diseases, and therapeutic targeting with monoclonal antibodies against IL-17 and IL-23 has shown considerable promise. Here, we report data to support selective bromodomain blockade of the transcriptional coactivators CBP (CREB binding protein) and p300 as an alternative approach to inhibit human Th17 responses. We show that CBP30 has marked molecular specificity for the bromodomains of CBP and p300, compared with 43 other bromodomains. In unbiased cellular testing on a diverse panel of cultured primary human cells, CBP30 reduced immune cell production of IL-17A and other proinflammatory cytokines. CBP30 also inhibited IL-17A secretion by Th17 cells from healthy donors and patients with ankylosing spondylitis and psoriatic arthritis. Transcriptional profiling of human T cells after CBP30 treatment showed a much more restricted effect on gene expression than that observed with the pan-BET (bromo and extraterminal domain protein family) bromodomain inhibitor JQ1. This selective targeting of the CBP/p300 bromodomain by CBP30 will potentially lead to fewer side effects than with the broadly acting epigenetic inhibitors currently in clinical trials.

Grebien F, Vedadi M, Getlik M, Giambruno R, Grover A, Avellino R, Skucha A, Vittori S, Kuznetsova E, Smil D et al. 2015. Pharmacological targeting of the Wdr5-MLL interaction in C/EBPα N-terminal leukemia. Nat Chem Biol, 11 (8), pp. 571-578. | Citations: 70 (Scopus) | Show Abstract | Read more

The CEBPA gene is mutated in 9% of patients with acute myeloid leukemia (AML). Selective expression of a short (30-kDa) CCAAT-enhancer binding protein-α (C/EBPα) translational isoform, termed p30, represents the most common type of CEBPA mutation in AML. The molecular mechanisms underlying p30-mediated transformation remain incompletely understood. We show that C/EBPα p30, but not the normal p42 isoform, preferentially interacts with Wdr5, a key component of SET/MLL (SET-domain/mixed-lineage leukemia) histone-methyltransferase complexes. Accordingly, p30-bound genomic regions were enriched for MLL-dependent H3K4me3 marks. The p30-dependent increase in self-renewal and inhibition of myeloid differentiation required Wdr5, as downregulation of the latter inhibited proliferation and restored differentiation in p30-dependent AML models. OICR-9429 is a new small-molecule antagonist of the Wdr5-MLL interaction. This compound selectively inhibited proliferation and induced differentiation in p30-expressing human AML cells. Our data reveal the mechanism of p30-dependent transformation and establish the essential p30 cofactor Wdr5 as a therapeutic target in CEBPA-mutant AML.

Chaikuad A, Knapp S, von Delft F. 2015. Defined PEG smears as an alternative approach to enhance the search for crystallization conditions and crystal-quality improvement in reduced screens. Acta Crystallogr D Biol Crystallogr, 71 (Pt 8), pp. 1627-1639. | Citations: 12 (Scopus) | Show Abstract | Read more

The quest for an optimal limited set of effective crystallization conditions remains a challenge in macromolecular crystallography, an issue that is complicated by the large number of chemicals which have been deemed to be suitable for promoting crystal growth. The lack of rational approaches towards the selection of successful chemical space and representative combinations has led to significant overlapping conditions, which are currently present in a multitude of commercially available crystallization screens. Here, an alternative approach to the sampling of widely used PEG precipitants is suggested through the use of PEG smears, which are mixtures of different PEGs with a requirement of either neutral or cooperatively positive effects of each component on crystal growth. Four newly defined smears were classified by molecular-weight groups and enabled the preservation of specific properties related to different polymer sizes. These smears not only allowed a wide coverage of properties of these polymers, but also reduced PEG variables, enabling greater sampling of other parameters such as buffers and additives. The efficiency of the smear-based screens was evaluated on more than 220 diverse recombinant human proteins, which overall revealed a good initial crystallization success rate of nearly 50%. In addition, in several cases successful crystallizations were only obtained using PEG smears, while various commercial screens failed to yield crystals. The defined smears therefore offer an alternative approach towards PEG sampling, which will benefit the design of crystallization screens sampling a wide chemical space of this key precipitant.

Gato-Cañas M, Martinez de Morentin X, Blanco-Luquin I, Fernandez-Irigoyen J, Zudaire I, Liechtenstein T, Arasanz H, Lozano T, Casares N, Chaikuad A et al. 2015. A core of kinase-regulated interactomes defines the neoplastic MDSC lineage. Oncotarget, 6 (29), pp. 27160-27175. | Citations: 15 (Scopus) | Show Abstract | Read more

Myeloid-derived suppressor cells (MDSCs) differentiate from bone marrow precursors, expand in cancer-bearing hosts and accelerate tumor progression. MDSCs have become attractive therapeutic targets, as their elimination strongly enhances anti-neoplastic treatments. Here, immature myeloid dendritic cells (DCs), MDSCs modeling tumor-infiltrating subsets or modeling non-cancerous (NC)-MDSCs were compared by in-depth quantitative proteomics. We found that neoplastic MDSCs differentially expressed a core of kinases which controlled lineage-specific (PI3K-AKT and SRC kinases) and cancer-induced (ERK and PKC kinases) protein interaction networks (interactomes). These kinases contributed to some extent to myeloid differentiation. However, only AKT and ERK specifically drove MDSC differentiation from myeloid precursors. Interfering with AKT and ERK with selective small molecule inhibitors or shRNAs selectively hampered MDSC differentiation and viability. Thus, we provide compelling evidence that MDSCs constitute a distinct myeloid lineage distinguished by a "kinase signature" and well-defined interactomes. Our results define new opportunities for the development of anti-cancer treatments targeting these tumor-promoting immune cells.

Arrowsmith CH, Audia JE, Austin C, Baell J, Bennett J, Blagg J, Bountra C, Brennan PE, Brown PJ, Bunnage ME et al. 2015. The promise and peril of chemical probes. Nat Chem Biol, 11 (8), pp. 536-541. | Citations: 276 (Scopus) | Show Abstract | Read more

© 2015 Nature America, Inc. All rights reserved. Chemical probes are powerful reagents with increasing impacts on biomedical research. However, probes of poor quality or that are used incorrectly generate misleading results. To help address these shortcomings, we will create a community-driven wiki resource to improve quality and convey current best practice.

Huston A, Arrowsmith CH, Knapp S, Schapira M. 2015. Probing the epigenome. Nat Chem Biol, 11 (8), pp. 542-545. | Citations: 24 (Web of Science Lite) | Show Abstract | Read more

© 2015 Nature America, Inc. All rights reserved. Epigenetic chemical probes are having a strong impact in biological discovery and target validation. Systematic coverage of emerging epigenetic target classes with these potent, selective, cell-active chemical tools will profoundly influence understanding of the human biology and pathology of chromatintemplated mechanisms.

Alexander LT, Möbitz H, Drueckes P, Savitsky P, Fedorov O, Elkins JM, Deane CM, Cowan-Jacob SW, Knapp S. 2015. Type II Inhibitors Targeting CDK2. ACS Chem Biol, 10 (9), pp. 2116-2125. | Citations: 24 (Scopus) | Show Abstract | Read more

Kinases can switch between active and inactive conformations of the ATP/Mg(2+) binding motif DFG, which has been explored for the development of type I or type II inhibitors. However, factors modulating DFG conformations remain poorly understood. We chose CDK2 as a model system to study the DFG in-out transition on a target that was thought to have an inaccessible DFG-out conformation. We used site-directed mutagenesis of key residues identified in structural comparisons in conjunction with biochemical and biophysical characterization of the generated mutants. As a result, we identified key residues that facilitate the DFG-out movement, facilitating binding of type II inhibitors. However, surprisingly, we also found that wild type CDK2 is able to bind type II inhibitors. Using protein crystallography structural analysis of the CDK2 complex with an aminopyrimidine-phenyl urea inhibitor (K03861) revealed a canonical type II binding mode and the first available type II inhibitor CDK2 cocrystal structure. We found that the identified type II inhibitors compete with binding of activating cyclins. In addition, analysis of the binding kinetics of the identified inhibitors revealed slow off-rates. The study highlights the importance of residues that may be distant to the ATP binding pocket in modulating the energetics of the DFG-out transition and hence inhibitor binding. The presented data also provide the foundation for a new class of slow off-rate cyclin-competitive CDK2 inhibitors targeting the inactive DFG-out state of this important kinase target.

Harrington L, Alexander LT, Knapp S, Bayley H. 2015. Inside Cover: Pim Kinase Inhibitors Evaluated with a Single-Molecule Engineered Nanopore Sensor (Angew. Chem. Int. Ed. 28/2015) Angewandte Chemie International Edition, 54 (28), pp. 8002-8002. | Read more

Harrington L, Alexander LT, Knapp S, Bayley H. 2015. Pim Kinase Inhibitors Evaluated with a Single-Molecule Engineered Nanopore Sensor Angewandte Chemie - International Edition, 54 (28), pp. 8154-8159. | Citations: 2 (Scopus) | Show Abstract | Read more

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Protein kinases are critical therapeutic targets. Pim kinases are implicated in several leukaemias and cancers. Here, we exploit a protein nanopore sensor for Pim kinases that bears a pseudosubstrate peptide attached by an enhanced engineering approach. Analyte binding to the sensor peptide is measured through observation of the modulation of ionic current through a single nanopore. We observed synergistic binding of MgATP and kinase to the sensor, which was used to develop a superior method to evaluate Pim kinase inhibitors featuring label-free determination of inhibition constants. The procedure circumvents many sources of bias or false-positives inherent in current assays. For example, we identified a potent inhibitor missed by differential scanning fluorimetry. The approach is also amenable to implementation on high throughput chips.

Hay DA, Rogers CM, Fedorov O, Tallant C, Martin S, Monteiro OP, Mueller S, Knapp S, Schofield CJ, Brennan PE. 2015. Design and synthesis of potent and selective inhibitors of BRD7 and BRD9 bromodomains MEDCHEMCOMM, 6 (7), pp. 1381-1386. | Citations: 34 (Scopus) | Show Abstract | Read more

<p>We describe potent and selective inhibitors of the BRD7 and BRD9 bromodomains intended for use as chemical probes to elucidate the biological roles of BRD7 and BRD9 in cells.</p>

Harrington L, Alexander LT, Knapp S, Bayley H. 2015. Pim Kinase Inhibitors Evaluated with a Single-Molecule Engineered Nanopore Sensor. Angew Chem Int Ed Engl, 54 (28), pp. 8154-8159. | Citations: 9 (Web of Science Lite) | Show Abstract | Read more

Protein kinases are critical therapeutic targets. Pim kinases are implicated in several leukaemias and cancers. Here, we exploit a protein nanopore sensor for Pim kinases that bears a pseudosubstrate peptide attached by an enhanced engineering approach. Analyte binding to the sensor peptide is measured through observation of the modulation of ionic current through a single nanopore. We observed synergistic binding of MgATP and kinase to the sensor, which was used to develop a superior method to evaluate Pim kinase inhibitors featuring label-free determination of inhibition constants. The procedure circumvents many sources of bias or false-positives inherent in current assays. For example, we identified a potent inhibitor missed by differential scanning fluorimetry. The approach is also amenable to implementation on high throughput chips.

Clark PGK, Vieira LCC, Tallant C, Fedorov O, Singleton DC, Rogers CM, Monteiro OP, Bennett JM, Baronio R, Müller S et al. 2015. LP99: Discovery and Synthesis of the First Selective BRD7/9 Bromodomain Inhibitor. Angew Chem Int Ed Engl, 54 (21), pp. 6217-6221. | Citations: 67 (Web of Science Lite) | Show Abstract | Read more

The bromodomain-containing proteins BRD9 and BRD7 are part of the human SWI/SNF chromatin-remodeling complexes BAF and PBAF. To date, no selective inhibitor for BRD7/9 has been reported despite its potential value as a biological tool or as a lead for future therapeutics. The quinolone-fused lactam LP99 is now reported as the first potent and selective inhibitor of the BRD7 and BRD9 bromodomains. Development of LP99 from a fragment hit was expedited through balancing structure-based inhibitor design and biophysical characterization against tractable chemical synthesis: Complexity-building nitro-Mannich/lactamization cascade processes allowed for early structure-activity relationship studies whereas an enantioselective organocatalytic nitro-Mannich reaction enabled the synthesis of the lead scaffold in enantioenriched form and on scale. This epigenetic probe was shown to inhibit the association of BRD7 and BRD9 to acetylated histones in vitro and in cells. Moreover, LP99 was used to demonstrate that BRD7/9 plays a role in regulating pro-inflammatory cytokine secretion.

Clark PGK, Vieira LCC, Tallant C, Fedorov O, Singleton DC, Rogers CM, Monteiro OP, Bennett JM, Baronio R, Müller S et al. 2015. LP99: Discovery and Synthesis of the First Selective BRD7/9 Bromodomain Inhibitor. Angew Chem Weinheim Bergstr Ger, 127 (21), pp. 6315-6319. | Citations: 7 (European Pubmed Central) | Show Abstract | Read more

The bromodomain-containing proteins BRD9 and BRD7 are part of the human SWI/SNF chromatin-remodeling complexes BAF and PBAF. To date, no selective inhibitor for BRD7/9 has been reported despite its potential value as a biological tool or as a lead for future therapeutics. The quinolone-fused lactam LP99 is now reported as the first potent and selective inhibitor of the BRD7 and BRD9 bromodomains. Development of LP99 from a fragment hit was expedited through balancing structure-based inhibitor design and biophysical characterization against tractable chemical synthesis: Complexity-building nitro-Mannich/lactamization cascade processes allowed for early structure-activity relationship studies whereas an enantioselective organocatalytic nitro-Mannich reaction enabled the synthesis of the lead scaffold in enantioenriched form and on scale. This epigenetic probe was shown to inhibit the association of BRD7 and BRD9 to acetylated histones in vitro and in cells. Moreover, LP99 was used to demonstrate that BRD7/9 plays a role in regulating pro-inflammatory cytokine secretion.

Fauster A, Rebsamen M, Huber KVM, Bigenzahn JW, Stukalov A, Lardeau C-H, Scorzoni S, Bruckner M, Gridling M, Parapatics K et al. 2015. A cellular screen identifies ponatinib and pazopanib as inhibitors of necroptosis. Cell Death Dis, 6 (5), pp. e1767. | Citations: 54 (Scopus) | Show Abstract | Read more

Necroptosis is a form of regulated necrotic cell death mediated by receptor-interacting serine/threonine-protein kinase 1 (RIPK1) and RIPK3. Necroptotic cell death contributes to the pathophysiology of several disorders involving tissue damage, including myocardial infarction, stroke and ischemia-reperfusion injury. However, no inhibitors of necroptosis are currently in clinical use. Here we performed a phenotypic screen for small-molecule inhibitors of tumor necrosis factor-alpha (TNF-α)-induced necroptosis in Fas-associated protein with death domain (FADD)-deficient Jurkat cells using a representative panel of Food and Drug Administration (FDA)-approved drugs. We identified two anti-cancer agents, ponatinib and pazopanib, as submicromolar inhibitors of necroptosis. Both compounds inhibited necroptotic cell death induced by various cell death receptor ligands in human cells, while not protecting from apoptosis. Ponatinib and pazopanib abrogated phosphorylation of mixed lineage kinase domain-like protein (MLKL) upon TNF-α-induced necroptosis, indicating that both agents target a component upstream of MLKL. An unbiased chemical proteomic approach determined the cellular target spectrum of ponatinib, revealing key members of the necroptosis signaling pathway. We validated RIPK1, RIPK3 and transforming growth factor-β-activated kinase 1 (TAK1) as novel, direct targets of ponatinib by using competitive binding, cellular thermal shift and recombinant kinase assays. Ponatinib inhibited both RIPK1 and RIPK3, while pazopanib preferentially targeted RIPK1. The identification of the FDA-approved drugs ponatinib and pazopanib as cellular inhibitors of necroptosis highlights them as potentially interesting for the treatment of pathologies caused or aggravated by necroptotic cell death.

Martin E, Knapp S, Engh RA, Moebitz H, Varin T, Roux B, Meiler J, Berdini V, Baumann A, Vieth M. 2015. Perspective on computational and structural aspects of kinase discovery from IPK2014. Biochim Biophys Acta, 1854 (10 Pt B), pp. 1595-1604. | Citations: 2 (Web of Science Lite) | Show Abstract | Read more

Recent advances in understanding the activity and selectivity of kinase inhibitors and their relationships to protein structure are presented. Conformational selection in kinases is studied from empirical, data-driven and simulation approaches. Ligand binding and its affinity are, in many cases, determined by the predetermined active and inactive conformation of kinases. Binding affinity and selectivity predictions highlight the current state of the art and advances in computational chemistry as it applies to kinase inhibitor discovery. Kinome wide inhibitor profiling and cell panel profiling lead to a better understanding of selectivity and allow for target validation and patient tailoring hypotheses. This article is part of a Special Issue entitled: Inhibitors of Protein Kinases.

Horne GA, Stewart HJS, Dickson J, Knapp S, Ramsahoye B, Chevassut T. 2015. Nanog requires BRD4 to maintain murine embryonic stem cell pluripotency and is suppressed by bromodomain inhibitor JQ1 together with Lefty1. Stem Cells Dev, 24 (7), pp. 879-891. | Citations: 26 (Web of Science Lite) | Show Abstract | Read more

Embryonic stem cells (ESCs) are maintained in an undifferentiated state through expression of the core transcriptional factors Nanog, Oct4, and Sox2. However, the epigenetic regulation of pluripotency is poorly understood. Differentiation of ESCs is accompanied by a global reduction of panacetylation of histones H3 and H4 suggesting that histone acetylation plays an important role in maintenance of ESC pluripotency. Acetylated lysine residues on histones are read by members of the bromodomain family that includes BET (bromodomain and extraterminal domain) proteins for which highly potent and selective inhibitors have been developed. In this study we demonstrate that the pan-BET bromodomain inhibitor JQ1 induces rapid spontaneous differentiation of murine ESCs by inducing marked transcriptional downregulation of Nanog as well as the stemness markers Lefty1 and Lefty2, but not Myc, often used as a marker of BET inhibitor activity in cancer. We show that the effects of JQ1 are recapitulated by knockdown of the BET family member BRD4 implicating this protein in Nanog regulation. These data are also supported by chromatin immunoprecipitation experiments which confirm BRD4 binding at the Nanog promoter that is known to require acetylation by the histone acetyltransferase MOF for transcriptional activity. In further support of our findings, we show that JQ1 antagonizes the stem cell-promoting effects of the histone deacetylase inhibitors sodium butyrate and valproic acid. Our data suggest that BRD4 is critical for the maintenance of ESC pluripotency and that this occurs primarily through the maintenance of Nanog expression.

Babak MV, Meier SM, Huber KVM, Reynisson J, Legin AA, Jakupec MA, Roller A, Stukalov A, Gridling M, Bennett KL et al. 2015. Target profiling of an antimetastatic RAPTA agent by chemical proteomics: relevance to the mode of action. Chem Sci, 6 (4), pp. 2449-2456. | Citations: 61 (Scopus) | Show Abstract | Read more

The clinical development of anticancer metallodrugs is often hindered by the elusive nature of their molecular targets. To identify the molecular targets of an antimetastatic ruthenium organometallic complex based on 1,3,5-triaza-7-phosphaadamantane (RAPTA), we employed a chemical proteomic approach. The approach combines the design of an affinity probe featuring the pharmacophore with mass-spectrometry-based analysis of interacting proteins found in cancer cell lysates. The comparison of data sets obtained for cell lysates from cancer cells before and after treatment with a competitive binder suggests that RAPTA interacts with a number of cancer-related proteins, which may be responsible for the antiangiogenic and antimetastatic activity of RAPTA complexes. Notably, the proteins identified include the cytokines midkine, pleiotrophin and fibroblast growth factor-binding protein 3. We also detected guanine nucleotide-binding protein-like 3 and FAM32A, which is in line with the hypothesis that the antiproliferative activity of RAPTA compounds is due to induction of a G2/M arrest and histone proteins identified earlier as potential targets.

Kovackova S, Chang L, Bekerman E, Neveu G, Barouch-Bentov R, Chaikuad A, Heroven C, Šála M, De Jonghe S, Knapp S et al. 2015. Selective Inhibitors of Cyclin G Associated Kinase (GAK) as Anti-Hepatitis C Agents. J Med Chem, 58 (8), pp. 3393-3410. | Citations: 19 (Scopus) | Show Abstract | Read more

Cyclin G associated kinase (GAK) emerged as a promising drug target for the treatment of viral infections. However, no potent and selective GAK inhibitors have been reported in the literature to date. This paper describes the discovery of isothiazolo[5,4-b]pyridines as selective GAK inhibitors, with the most potent congeners displaying low nanomolar binding affinity for GAK. Cocrystallization experiments revealed that these compounds behaved as classic type I ATP-competitive kinase inhibitors. In addition, we have demonstrated that these compounds exhibit a potent activity against hepatitis C virus (HCV) by inhibiting two temporally distinct steps in the HCV life cycle (i.e., viral entry and assembly). Hence, these GAK inhibitors represent chemical probes to study GAK function in different disease areas where GAK has been implicated (including viral infection, cancer, and Parkinson's disease).

Rebsamen M, Pochini L, Stasyk T, de Araújo MEG, Galluccio M, Kandasamy RK, Snijder B, Fauster A, Rudashevskaya EL, Bruckner M et al. 2015. SLC38A9 is a component of the lysosomal amino acid sensing machinery that controls mTORC1. Nature, 519 (7544), pp. 477-481. | Citations: 232 (Scopus) | Show Abstract | Read more

Cell growth and proliferation are tightly linked to nutrient availability. The mechanistic target of rapamycin complex 1 (mTORC1) integrates the presence of growth factors, energy levels, glucose and amino acids to modulate metabolic status and cellular responses. mTORC1 is activated at the surface of lysosomes by the RAG GTPases and the Ragulator complex through a not fully understood mechanism monitoring amino acid availability in the lysosomal lumen and involving the vacuolar H(+)-ATPase. Here we describe the uncharacterized human member 9 of the solute carrier family 38 (SLC38A9) as a lysosomal membrane-resident protein competent in amino acid transport. Extensive functional proteomic analysis established SLC38A9 as an integral part of the Ragulator-RAG GTPases machinery. Gain of SLC38A9 function rendered cells resistant to amino acid withdrawal, whereas loss of SLC38A9 expression impaired amino-acid-induced mTORC1 activation. Thus SLC38A9 is a physical and functional component of the amino acid sensing machinery that controls the activation of mTOR.

Falke H, Chaikuad A, Becker A, Loaëc N, Lozach O, Abu Jhaisha S, Becker W, Jones PG, Preu L, Baumann K et al. 2015. 10-iodo-11H-indolo[3,2-c]quinoline-6-carboxylic acids are selective inhibitors of DYRK1A. J Med Chem, 58 (7), pp. 3131-3143. | Citations: 30 (Web of Science Lite) | Show Abstract | Read more

The protein kinase DYRK1A has been suggested to act as one of the intracellular regulators contributing to neurological alterations found in individuals with Down syndrome. For an assessment of the role of DYRK1A, selective synthetic inhibitors are valuable pharmacological tools. However, the DYRK1A inhibitors described in the literature so far either are not sufficiently selective or have not been tested against closely related kinases from the DYRK and the CLK protein kinase families. The aim of this study was the identification of DYRK1A inhibitors exhibiting selectivity versus the structurally and functionally closely related DYRK and CLK isoforms. Structure modification of the screening hit 11H-indolo[3,2-c]quinoline-6-carboxylic acid revealed structure-activity relationships for kinase inhibition and enabled the design of 10-iodo-substituted derivatives as very potent DYRK1A inhibitors with considerable selectivity against CLKs. X-ray structure determination of three 11H-indolo[3,2-c]quinoline-6-carboxylic acids cocrystallized with DYRK1A confirmed the predicted binding mode within the ATP binding site.

Edwards AM, Arrowsmith CH, Bountra C, Bunnage ME, Feldmann M, Knight JC, Patel DD, Prinos P, Taylor MD, Sundström M, SGC Open Source Target-Discovery Partnership. 2015. Preclinical target validation using patient-derived cells. Nat Rev Drug Discov, 14 (3), pp. 149-150. | Citations: 28 (Web of Science Lite) | Show Abstract | Read more

The Structural Genomics Consortium (SGC) and its clinical, industry and disease-foundation partners are launching open-source preclinical translational medicine studies.

Drouin L, McGrath S, Vidler LR, Chaikuad A, Monteiro O, Tallant C, Philpott M, Rogers C, Fedorov O, Liu M et al. 2015. Structure enabled design of BAZ2-ICR, a chemical probe targeting the bromodomains of BAZ2A and BAZ2B. J Med Chem, 58 (5), pp. 2553-2559. | Citations: 54 (Scopus) | Show Abstract | Read more

The bromodomain containing proteins BAZ2A/B play essential roles in chromatin remodeling and regulation of noncoding RNAs. We present the structure based discovery of a potent, selective, and cell active inhibitor 13 (BAZ2-ICR) of the BAZ2A/B bromodomains through rapid optimization of a weakly potent starting point. A key feature of the presented inhibitors is an intramolecular aromatic stacking interaction that efficiently occupies the shallow bromodomain pockets. 13 represents an excellent chemical probe for functional studies of the BAZ2 bromodomains in vitro and in vivo.

Martin E, Knapp S, Engh RA, Moebitz H, Varin T, Roux B, Meiler J, Berdini V, Baumann A, Vieth M. 2015. Perspective on computational and structural aspects of kinase discovery from IPK2014 Biochimica et Biophysica Acta - Proteins and Proteomics, 1854 (10), pp. 1595-1604. | Citations: 3 (Scopus) | Show Abstract | Read more

© 2015 Elsevier B.V. All rights reserved. Recent advances in understanding the activity and selectivity of kinase inhibitors and their relationships to protein structure are presented. Conformational selection in kinases is studied from empirical, data-driven and simulation approaches. Ligand binding and its affinity are, in many cases, determined by the predetermined active and inactive conformation of kinases. Binding affinity and selectivity predictions highlight the current state of the art and advances in computational chemistry as it applies to kinase inhibitor discovery. Kinome wide inhibitor profiling and cell panel profiling lead to a better understanding of selectivity and allow for target validation and patient tailoring hypotheses. This article is part of a Special Issue entitled: Inhibitors of Protein Kinases.

Kestav K, Lavogina D, Raidaru G, Chaikuad A, Knapp S, Uri A. 2015. Bisubstrate inhibitor approach for targeting mitotic kinase Haspin. Bioconjug Chem, 26 (2), pp. 225-234. | Citations: 6 (Web of Science Lite) | Show Abstract | Read more

During the past decade, the basophilic atypical kinase Haspin has emerged as a key player in mitosis responsible for phosphorylation of Thr3 residue of histone H3. Here, we report the construction of conjugates comprising an aromatic fragment targeted to the ATP-site of Haspin and a peptide mimicking the N-terminus of histone H3. The combination of effective solid phase synthesis procedures and a high throughput binding/displacement assay with fluorescence anisotropy readout afforded the development of inhibitors with remarkable subnanomolar affinity toward Haspin. The selectivity profiles of novel conjugates were established by affinity studies with a model basophilic kinase (catalytic subunit of cAMP-dependent protein kinase) and by a commercial 1-point inhibition assay with 43 protein kinases.

Homan KT, Larimore KM, Elkins JM, Szklarz M, Knapp S, Tesmer JJG. 2015. Identification and structure-function analysis of subfamily selective G protein-coupled receptor kinase inhibitors. ACS Chem Biol, 10 (1), pp. 310-319. | Citations: 29 (Web of Science Lite) | Show Abstract | Read more

Selective inhibitors of individual subfamilies of G protein-coupled receptor kinases (GRKs) would serve as useful chemical probes as well as leads for therapeutic applications ranging from heart failure to Parkinson's disease. To identify such inhibitors, differential scanning fluorimetry was used to screen a collection of known protein kinase inhibitors that could increase the melting points of the two most ubiquitously expressed GRKs: GRK2 and GRK5. Enzymatic assays on 14 of the most stabilizing hits revealed that three exhibit nanomolar potency of inhibition for individual GRKs, some of which exhibiting orders of magnitude selectivity. Most of the identified compounds can be clustered into two chemical classes: indazole/dihydropyrimidine-containing compounds that are selective for GRK2 and pyrrolopyrimidine-containing compounds that potently inhibit GRK1 and GRK5 but with more modest selectivity. The two most potent inhibitors representing each class, GSK180736A and GSK2163632A, were cocrystallized with GRK2 and GRK1, and their atomic structures were determined to 2.6 and 1.85 Å spacings, respectively. GSK180736A, developed as a Rho-associated, coiled-coil-containing protein kinase inhibitor, binds to GRK2 in a manner analogous to that of paroxetine, whereas GSK2163632A, developed as an insulin-like growth factor 1 receptor inhibitor, occupies a novel region of the GRK active site cleft that could likely be exploited to achieve more selectivity. However, neither compound inhibits GRKs more potently than their initial targets. This data provides the foundation for future efforts to rationally design even more potent and selective GRK inhibitors.

Wilbek TS, Skovgaard T, Sorrell FJ, Knapp S, Berthelsen J, Strømgaard K. 2015. Identification and characterization of a small-molecule inhibitor of death-associated protein kinase 1. Chembiochem, 16 (1), pp. 59-63. | Citations: 8 (Web of Science Lite) | Read more

Toi M, Pillai MR, Gupta S, Badwe R, Carmo-Fonseca M, Costa L, Chow LWC, Knapp S, Kumar R. 2015. The global cancer genomics consortium’s symposium: New era of molecular medicine and epigenetic cancer medicine - Cross section of genomics and epigenetics Genes and Cancer, 6 (1-2), pp. 1-8. | Show Abstract

© 2015, Impact Journals LLC. All rights reserved. The Global Cancer Genomics Consortium (GCGC) colleagues continue to function together as an interactive multidisciplinary team of cancer biologists and oncologists with interests in genomics and building a bidirectional bridge between cancer clinics and laboratories while taking advantage of shared resources among its member scientists. The GCGC includes member scientists from six institutions in Lisbon, United Kingdom, Japan, India and United States, and was formed in December 2010 for a period of five years. Driven by valuable lessons learned from the previous symposiums, the fourth GCGC Symposium focused on a cross section of genomic and epigenetic cancer medicine and it’s for this reason we chose the conference theme - New Era of Molecular Medicine and Epigenetic Cancer Medicine: Cross Section of Genomics and Epigenetics. This year’s symposium was co-organized by the Organization for Oncology and Translational Research (OOTR) at the Shiran Hall, Kyoto University, Kyoto, Japan, from November 14 and 15, 2014. The symposium attracted around 80 participants from 14 countries, and counted with 23 invited platform speakers. Scientific sessions included eight platform sessions and one poster session, and three plenary lectures. The symposium focused on cancer stem cells and self-renewal, cancer transcriptome, tumor heterogeneity, tumor biology, breast cancer genomics, targeted therapeutics and personalized medicine. The issues of cancer stem cells and tumor heterogeneity were echoed in most of the scientific presentations. The meeting concluded with an oral presentation by the best poster awardee and closing remarks by meeting co-chairs.

Tallant C, Valentini E, Fedorov O, Overvoorde L, Ferguson FM, Filippakopoulos P, Svergun DI, Knapp S, Ciulli A. 2015. Molecular basis of histone tail recognition by human TIP5 PHD finger and bromodomain of the chromatin remodeling complex NoRC. Structure, 23 (1), pp. 80-92. | Citations: 25 (Web of Science Lite) | Show Abstract | Read more

Binding of the chromatin remodeling complex NoRC to RNA complementary to the rDNA promoter mediates transcriptional repression. TIP5, the largest subunit of NoRC, is involved in recruitment to rDNA by interactions with promoter-bound TTF-I, pRNA, and acetylation of H4K16. TIP5 domains that recognize posttranslational modifications on histones are essential for recruitment of NoRC to chromatin, but how these reader modules recognize site-specific histone tails has remained elusive. Here, we report crystal structures of PHD zinc finger and bromodomains from human TIP5 and BAZ2B in free form and bound to H3 and/or H4 histones. PHD finger functions as an independent structural module in recognizing unmodified H3 histone tails, and the bromodomain prefers H3 and H4 acetylation marks followed by a key basic residue, KacXXR. Further low-resolution analyses of PHD-bromodomain modules provide molecular insights into their trans histone tail recognition, required for nucleosome recruitment and transcriptional repression of the NoRC complex.

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