register interest

Dr Kilian Huber

Research Area: Drug Discovery
Technology Exchange: Crystallography, Drug discovery, Mass spectrometry and Protein interaction
Scientific Themes: Protein Science & Structural Biology and Cancer Biology
Keywords: Chemical Biology, Target Identification, Target Validation, Drug Discovery, Chemical Probes, Systems Pharmacology, Medicinal Chemistry and Proteomics
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Probing Biology with Small Molecules for Drug Target Discovery

The development of new medicines to treat diseases like cancer or inflammatory disorders is dependent on the identification of novel drug targets. Target selection requires an understanding of the functional relevance of a given protein in both physiological and pathophysiological conditions.

Chemical Biology combines chemistry and biology to generate small molecule tools, so-called “chemical probes”, that enable the functional exploration of cellular proteins with regard to their relevance for drug discovery. Candidate targets may originate from genetic studies linking the expression or mutation of a selected gene to a particular disease, in vitro genetic screens such as RNA-interference or genome-editing (e.g. CRISPR), compounds identified in phenotypic assays or drugs already in use.

To identify, explore and validate targets the Huber laboratory uses a variety of different discovery approaches such as small molecule screens, biochemical assays, protein X-ray crystallography, chemical and protein-protein interaction proteomics, medicinal chemistry, RNAi, genome-editing alongside classical molecular and cellular biology techniques aiming at the development of chemical probes that may provide leads for drug discovery.

Name Department Institution Country
Professor Benedikt M Kessler Target Discovery Institute Oxford University, NDM Research Building United Kingdom
Professor Stefan Knapp Structural Genomics Consortium Oxford University, NDM Research Building United Kingdom
Dr Alex Bullock Structural Genomics Consortium Oxford University, Old Road Campus Research Building United Kingdom
Professor Paul Brennan Target Discovery Institute Oxford University, NDM Research Building United Kingdom
Daniel Ebner Target Discovery Institute Oxford University, NDM Research Building United Kingdom
Dr Angela Russell (RDM) Chemistry University of Oxford United Kingdom
Prof Adrian L Harris FMedSci FRCP (RDM) Weatherall Institute of Molecular Medicine Oxford University, Weatherall Institute of Molecular Medicine United Kingdom
Professor Mads Gyrd-Hansen Oxford Ludwig Institute Oxford University, Old Road Campus Research Building United Kingdom
Professor Susan Lea Sir William Dunn School of Pathology University of Oxford United Kingdom
Dr Oleg Fedorov Target Discovery Institute Oxford University, NDM Research Building United Kingdom
Prof Zameel Cader MRCP (RDM) Weatherall Institute of Molecular Medicine Oxford University, Weatherall Institute of Molecular Medicine United Kingdom
Professor Frank von Delft Structural Genomics Consortium Oxford University, Old Road Campus Research Building United Kingdom
Prof Antony Galione FRS (RDM) Department of Pharmacology University of Oxford United Kingdom
Dr Akane Kawamura (RDM) Cardiovascular Medicine Oxford University, Chemistry United Kingdom
Artarini A, Meyer M, Shin YJ, Huber K, Hilz N, Bracher F, Eros D, Orfi L, Keri G, Goedert S et al. 2019. Regulation of influenza a virus mRNA splicing by CLK1. Antiviral Res, | Show Abstract | Read more

Influenza A virus carries eight negative single-stranded RNAs and uses spliced mRNAs to increase the number of proteins produced from them. Several genome-wide screens for essential host factors for influenza A virus replication revealed a necessity for splicing and splicing-related factors, including Cdc-like kinase 1 (CLK1). This CLK family kinase plays a role in alternative splicing regulation through phosphorylation of serine-arginine rich (SR) proteins. To examine the influence that modulation of splicing regulation has on influenza infection, we analyzed the effect of CLK1 knockdown and inhibition. CLK1 knockdown in A549 cells reduced influenza A/WSN/33 virus replication and increased the level of splicing of segment 7, encoding the viral M1 and M2 proteins. CLK1-/- mice infected with influenza A/England/195/2009 (H1N1pdm09) virus supported lower levels of virus replication than wild-type mice. Screening of newly developed CLK inhibitors revealed several compounds that have an effect on the level of splicing of influenza A gene segment M in different models and decrease influenza A/WSN/33 virus replication in A549 cells. The promising inhibitor KH-CB19, an indole-based enaminonitrile with unique binding mode for CLK1, and its even more selective analogue NIH39 showed high specificity towards CLK1 and had a similar effect on influenza mRNA splicing regulation. Taken together, our findings indicate that targeting host factors that regulate splicing of influenza mRNAs may represent a novel therapeutic approach.

Resnick E, Bradley A, Gan J, Douangamath A, Krojer T, Sethi R, Geurink PP, Aimon A, Amitai G, Bellini D et al. 2019. Rapid Covalent-Probe Discovery by Electrophile-Fragment Screening. J Am Chem Soc, 141 (22), pp. 8951-8968. | Show Abstract | Read more

Covalent probes can display unmatched potency, selectivity, and duration of action; however, their discovery is challenging. In principle, fragments that can irreversibly bind their target can overcome the low affinity that limits reversible fragment screening, but such electrophilic fragments were considered nonselective and were rarely screened. We hypothesized that mild electrophiles might overcome the selectivity challenge and constructed a library of 993 mildly electrophilic fragments. We characterized this library by a new high-throughput thiol-reactivity assay and screened them against 10 cysteine-containing proteins. Highly reactive and promiscuous fragments were rare and could be easily eliminated. In contrast, we found hits for most targets. Combining our approach with high-throughput crystallography allowed rapid progression to potent and selective probes for two enzymes, the deubiquitinase OTUB2 and the pyrophosphatase NUDT7. No inhibitors were previously known for either. This study highlights the potential of electrophile-fragment screening as a practical and efficient tool for covalent-ligand discovery.

Gadelha APR, Bravim B, Vidal J, Reignault LC, Cosme B, Huber K, Bracher F, de Souza W. 2019. Alterations on growth and cell organization of Giardia intestinalis trophozoites after treatment with KH-TFMDI, a novel class III histone deacetylase inhibitor. Int J Med Microbiol, 309 (2), pp. 130-142. | Show Abstract | Read more

Giardia trophozoites have developed resistance mechanisms to currently available compounds, leading to treatment failures. In this context, the development of new additional agents is mandatory. Sirtuins, which are class III NAD+-dependent histone deacetylases, have been considered important targets for the development of new anti-parasitic drugs. Here, we evaluated the activity of KH-TFMDI, a novel 3-arylideneindolin-2-one-type sirtuin inhibitor, on G. intestinalis trophozoites. This compound decreased the trophozoite growth presenting an IC50 value lower than nicotinamide, a moderately active inhibitor of yeast and human sirtuins. Light and electron microscopy analysis showed the presence of multinucleated cell clusters suggesting that the cytokinesis could be compromised in treated trophozoites. Cell rounding, concomitantly with the folding of the ventro-lateral flange and flagella internalization, was also observed. These cells eventually died by a mechanism which lead to DNA/nuclear damage, formation of multi-lamellar bodies and annexin V binding on the parasite surface. Taken together, these data show that KH-TFMDI has significant effects against G. intestinalis trophozoites proliferation and structural organization and suggest that histone deacetylation pathway should be explored on this protozoon as target for chemotherapy.

Scheer S, Ackloo S, Medina TS, Schapira M, Li F, Ward JA, Lewis AM, Northrop JP, Richardson PL, Kaniskan HÜ et al. 2019. A chemical biology toolbox to study protein methyltransferases and epigenetic signaling. Nat Commun, 10 (1), pp. 19. | Show Abstract | Read more

Protein methyltransferases (PMTs) comprise a major class of epigenetic regulatory enzymes with therapeutic relevance. Here we present a collection of chemical probes and associated reagents and data to elucidate the function of human and murine PMTs in cellular studies. Our collection provides inhibitors and antagonists that together modulate most of the key regulatory methylation marks on histones H3 and H4, providing an important resource for modulating cellular epigenomes. We describe a comprehensive and comparative characterization of the probe collection with respect to their potency, selectivity, and mode of inhibition. We demonstrate the utility of this collection in CD4+ T cell differentiation assays revealing the potential of individual probes to alter multiple T cell subpopulations which may have implications for T cell-mediated processes such as inflammation and immuno-oncology. In particular, we demonstrate a role for DOT1L in limiting Th1 cell differentiation and maintaining lineage integrity. This chemical probe collection and associated data form a resource for the study of methylation-mediated signaling in epigenetics, inflammation and beyond.

Vazquez-Rodriguez S, Wright M, Rogers CM, Cribbs AP, Velupillai S, Philpott M, Lee H, Dunford JE, Huber KVM, Robers MB et al. 2019. Design, Synthesis and Characterization of Covalent KDM5 Inhibitors. Angew Chem Int Ed Engl, 58 (2), pp. 515-519. | Show Abstract | Read more

Histone lysine demethylases (KDMs) are involved in the dynamic regulation of gene expression and they play a critical role in several biological processes. Achieving selectivity over the different KDMs has been a major challenge for KDM inhibitor development. Here we report potent and selective KDM5 covalent inhibitors designed to target cysteine residues only present in the KDM5 sub-family. The covalent binding to the targeted proteins was confirmed by MS and time-dependent inhibition. Additional competition assays show that compounds were non 2-OG competitive. Target engagement and ChIP-seq analysis showed that the compounds inhibited the KDM5 members in cells at nano- to micromolar levels and induce a global increase of the H3K4me3 mark at transcriptional start sites.

Moustakim M, Christott T, Monteiro OP, Bennett J, Giroud C, Ward J, Rogers CM, Smith P, Panagakou I, Díaz-Sáez L et al. 2018. Discovery of an MLLT1/3 YEATS Domain Chemical Probe. Angew Chem Int Ed Engl, 57 (50), pp. 16302-16307. | Show Abstract | Read more

YEATS domain (YD) containing proteins are an emerging class of epigenetic targets in drug discovery. Dysregulation of these modified lysine-binding proteins has been linked to the onset and progression of cancers. We herein report the discovery and characterisation of the first small-molecule chemical probe, SGC-iMLLT, for the YD of MLLT1 (ENL/YEATS1) and MLLT3 (AF9/YEATS3). SGC-iMLLT is a potent and selective inhibitor of MLLT1/3-histone interactions. Excellent selectivity over other human YD proteins (YEATS2/4) and bromodomains was observed. Furthermore, our probe displays cellular target engagement of MLLT1 and MLLT3. The first small-molecule X-ray co-crystal structures with the MLLT1 YD are also reported. This first-in-class probe molecule can be used to understand MLLT1/3-associated biology and the therapeutic potential of small-molecule YD inhibitors.

Stefaniak J, Lewis AM, Conole D, Galan SRG, Bataille CJR, Wynne GM, Castaldi MP, Lundbäck T, Russell AJ, Huber KVM. 2018. Chemical Instability and Promiscuity of Arylmethylidenepyrazolinone-Based MDMX Inhibitors. ACS Chem Biol, 13 (10), pp. 2849-2854. | Show Abstract | Read more

Targeting the protein-protein interaction between p53 and MDM2/MDMX (MDM4) represents an attractive anticancer strategy for the treatment of p53-competent tumors. Several selective and potent MDM2 inhibitors have been developed and entered the clinic; however, the repertoire of MDMX antagonists is still limited. The arylmethylidenepyrazolinone SJ-172550 has been reported as a selective MDMX antagonist; yet, uncertainties about its mechanism of action have raised doubts about its use as a chemical probe. Here, we show that, in addition to its unclear mode of action, SJ-172550 is unstable in aqueous buffers, giving rise to side products of unknown biological activity. Using an SJ-172550-derived affinity probe, we observed promiscuous binding to cellular proteins whereas cellular thermal shift assays did not reveal a stabilizing effect on MDMX. Overall, our results raise further questions about the interpretation of data using SJ-172550 and related compounds to investigate cellular phenotypes.

Hrdinka M, Schlicher L, Dai B, Pinkas DM, Bufton JC, Picaud S, Ward JA, Rogers C, Suebsuwong C, Nikhar S et al. 2018. Small molecule inhibitors reveal an indispensable scaffolding role of RIPK2 in NOD2 signaling. EMBO J, 37 (17), pp. e99372-e99372. | Show Abstract | Read more

RIPK2 mediates inflammatory signaling by the bacteria-sensing receptors NOD1 and NOD2. Kinase inhibitors targeting RIPK2 are a proposed strategy to ameliorate NOD-mediated pathologies. Here, we reveal that RIPK2 kinase activity is dispensable for NOD2 inflammatory signaling and show that RIPK2 inhibitors function instead by antagonizing XIAP-binding and XIAP-mediated ubiquitination of RIPK2. We map the XIAP binding site on RIPK2 to the loop between β2 and β3 of the N-lobe of the kinase, which is in close proximity to the ATP-binding pocket. Through characterization of a new series of ATP pocket-binding RIPK2 inhibitors, we identify the molecular features that determine their inhibition of both the RIPK2-XIAP interaction, and of cellular and in vivoNOD2 signaling. Our study exemplifies how targeting of the ATP-binding pocket in RIPK2 can be exploited to interfere with the RIPK2-XIAP interaction for modulation of NOD signaling.

Rahm F, Viklund J, Trésaugues L, Ellermann M, Giese A, Ericsson U, Forsblom R, Ginman T, Günther J, Hallberg K et al. 2018. Creation of a Novel Class of Potent and Selective MutT Homologue 1 (MTH1) Inhibitors Using Fragment-Based Screening and Structure-Based Drug Design. J Med Chem, 61 (6), pp. 2533-2551. | Show Abstract | Read more

Recent literature has both suggested and questioned MTH1 as a novel cancer target. BAY-707 was just published as a target validation small molecule probe for assessing the effects of pharmacological inhibition of MTH1 on tumor cell survival, both in vitro and in vivo. (1) In this report, we describe the medicinal chemistry program creating BAY-707, where fragment-based methods were used to develop a series of highly potent and selective MTH1 inhibitors. Using structure-based drug design and rational medicinal chemistry approaches, the potency was increased over 10,000 times from the fragment starting point while maintaining high ligand efficiency and drug-like properties.

Scheer S, Ackloo S, Medina T, Schapira M, Li F, Ward J, Lewis A, Northrop J, Richardson P, Kaniskan HU et al. 2018. A Chemical Biology Toolbox for the Study of Protein Methyltransferases and Epigenetic Signaling | Show Abstract | Read more

Protein methyltransferases (PMTs) comprise a major class of epigenetic regulatory enzymes with therapeutic relevance. Here we present a collection of chemical probes and associated reagents and data to elucidate the function of human and murine PMTs in cellular studies. Our collection provides inhibitors and antagonists that together modulate most of the key regulatory methylation marks on histones H3 and H4, providing an important resource for modulating cellular epigenomes. We describe a comprehensive and comparative characterization of the probe collection with respect to their potency, selectivity, and mode of inhibition. We demonstrate the utility of this collection in CD4+ T cell differentiation assays revealing the remarkable potential of individual probes to alter multiple T cell subpopulations with important implications for T cell-mediated processes such as inflammation and immuno-oncology. In particular, we demonstrate a role for DOT1L in limiting Th1 cell differentiation and maintaining lineage integrity.

Fernández-Montalván AE, Berger M, Kuropka B, Koo SJ, Badock V, Weiske J, Puetter V, Holton SJ, Stöckigt D, Ter Laak A et al. 2017. Isoform-Selective ATAD2 Chemical Probe with Novel Chemical Structure and Unusual Mode of Action. ACS Chem Biol, 12 (11), pp. 2730-2736. | Show Abstract | Read more

ATAD2 (ANCCA) is an epigenetic regulator and transcriptional cofactor, whose overexpression has been linked to the progress of various cancer types. Here, we report a DNA-encoded library screen leading to the discovery of BAY-850, a potent and isoform selective inhibitor that specifically induces ATAD2 bromodomain dimerization and prevents interactions with acetylated histones in vitro, as well as with chromatin in cells. These features qualify BAY-850 as a chemical probe to explore ATAD2 biology.

Vasta JD, Corona CR, Wilkinson J, Zimprich CA, Hartnett JR, Ingold MR, Zimmerman K, Machleidt T, Kirkland TA, Huwiler KG et al. 2018. Quantitative, Wide-Spectrum Kinase Profiling in Live Cells for Assessing the Effect of Cellular ATP on Target Engagement. Cell Chem Biol, 25 (2), pp. 206-214.e11. | Show Abstract | Read more

For kinase inhibitors, intracellular target selectivity is fundamental to pharmacological mechanism. Although a number of acellular techniques have been developed to measure kinase binding or enzymatic inhibition, such approaches can fail to accurately predict engagement in cells. Here we report the application of an energy transfer technique that enabled the first broad-spectrum, equilibrium-based approach to quantitatively profile target occupancy and compound affinity in live cells. Using this method, we performed a selectivity profiling for clinically relevant kinase inhibitors against 178 full-length kinases, and a mechanistic interrogation of the potency offsets observed between cellular and biochemical analysis. For the multikinase inhibitor crizotinib, our approach accurately predicted cellular potency and revealed improved target selectivity compared with biochemical measurements. Due to cellular ATP, a number of putative crizotinib targets are unexpectedly disengaged in live cells at a clinically relevant drug dose.

Hadzijusufovic E, Albrecht-Schgoer K, Huber K, Hoermann G, Grebien F, Eisenwort G, Schgoer W, Herndlhofer S, Kaun C, Theurl M et al. 2017. Nilotinib-induced vasculopathy: identification of vascular endothelial cells as a primary target site. Leukemia, 31 (11), pp. 2388-2397. | Show Abstract | Read more

The BCR/ABL1 inhibitor Nilotinib is increasingly used to treat patients with chronic myeloid leukemia (CML). Although otherwise well-tolerated, Nilotinib has been associated with the occurrence of progressive arterial occlusive disease (AOD). Our objective was to determine the exact frequency of AOD and examine in vitro and in vivo effects of Nilotinib and Imatinib on endothelial cells to explain AOD-development. In contrast to Imatinib, Nilotinib was found to upregulate pro-atherogenic adhesion-proteins (ICAM-1, E-selectin, VCAM-1) on human endothelial cells. Nilotinib also suppressed endothelial cell proliferation, migration and tube-formation and bound to a distinct set of target-kinases, relevant to angiogenesis and atherosclerosis, including angiopoietin receptor-1 TEK, ABL-2, JAK1 and MAP-kinases. Nilotinib and siRNA against ABL-2 also suppressed KDR expression. In addition, Nilotinib augmented atherosclerosis in ApoE-/- mice and blocked reperfusion and angiogenesis in a hindlimb-ischemia model of arterial occlusion, whereas Imatinib showed no comparable effects. Clinically overt AOD-events were found to accumulate over time in Nilotinib-treated patients. After a median observation-time of 2.0 years, the AOD-frequency was higher in these patients (29.4%) compared to risk factor- and age-matched controls (<5%). Together, Nilotinib exerts direct pro-atherogenic and anti-angiogenic effects on vascular endothelial cells, which may contribute to development of AOD in patients with CML.

Verçoza BRF, Godinho JLP, de Macedo-Silva ST, Huber K, Bracher F, de Souza W, Rodrigues JCF. 2017. KH-TFMDI, a novel sirtuin inhibitor, alters the cytoskeleton and mitochondrial metabolism promoting cell death in Leishmania amazonensis. Apoptosis, 22 (9), pp. 1169-1188. | Show Abstract | Read more

Treatment of leishmaniasis involves the use of antimonials, miltefosine, amphotericin B or pentamidine. However, the side effects of these drugs and the reports of drug-resistant parasites demonstrate the need for new treatments that are safer and more efficacious. Histone deacetylase inhibitors are a new class of compounds with potential to treat leishmaniasis. Herein, we evaluated the effects of KH-TFMDI, a novel histone deacetylase inhibitor, on Leishmania amazonensis promastigotes and intracellular amastigotes. The IC50 values of this compound for promastigotes and intracellular amastigotes were 1.976 and 1.148 μM, respectively, after 72 h of treatment. Microscopic analyses revealed that promastigotes became elongated and thinner in response to KH-TFMDI, indicating changes in cytoskeleton organization. Immunofluorescence microscopy, western blotting and flow cytometry using an anti-acetylated tubulin antibody revealed an increase in the expression of acetylated tubulin. Furthermore, transmission electron microscopy revealed several ultrastructural changes, such as (a) mitochondrial swelling, followed by the formation of many vesicles inside the matrix; (b) presence of lipid bodies randomly distributed through the cytoplasm; (c) abnormal chromatin condensation; and (d) formation of blebs on the plasma membrane. Physiological studies for mitochondrial function, flow cytometry with propidium iodide and TUNEL assay confirmed the alterations in the mitochondrial metabolism, cell cycle, and DNA fragmentation, respectively, which could result to cell death by mechanisms related to apoptosis-like. All these together indicate that histone deacetylases are promising targets for the development of new drugs to treat Leishmania, and KH-TFMDI is a promising drug candidate that should be tested in vivo.

Radic-Sarikas B, Halasz M, Huber KVM, Winter GE, Tsafou KP, Papamarkou T, Brunak S, Kolch W, Superti-Furga G. 2017. Lapatinib potentiates cytotoxicity of  YM155 in neuroblastoma via inhibition of the ABCB1 efflux transporter. Sci Rep, 7 (1), pp. 3091. | Show Abstract | Read more

Adverse side effects of cancer agents are of great concern in the context of childhood tumors where they can reduce the quality of life in young patients and cause life-long adverse effects. Synergistic drug combinations can lessen potential toxic side effects through lower dosing and simultaneously help to overcome drug resistance. Neuroblastoma is the most common cancer in infancy and extremely heterogeneous in clinical presentation and features. Applying a systematic pairwise drug combination screen we observed a highly potent synergy in neuroblastoma cells between the EGFR kinase inhibitor lapatinib and the anticancer compound YM155 that is preserved across several neuroblastoma variants. Mechanistically, the synergy was based on a lapatinib induced inhibition of the multidrug-resistance efflux transporter ABCB1, which is frequently expressed in resistant neuroblastoma cells, which allowed prolonged and elevated cytotoxicity of YM155. In addition, the drug combination (i.e. lapatinib plus YM155) decreased neuroblastoma tumor size in an in vivo model.

Vladimer GI, Snijder B, Krall N, Bigenzahn JW, Huber KVM, Lardeau C-H, Sanjiv K, Ringler A, Berglund UW, Sabler M et al. 2017. Global survey of the immunomodulatory potential of common drugs. Nat Chem Biol, 13 (6), pp. 681-690. | Show Abstract | Read more

Small-molecule drugs may complement antibody-based therapies in an immune-oncology setting, yet systematic methods for the identification and characterization of the immunomodulatory properties of these entities are lacking. We surveyed the immumomodulatory potential of 1,402 small chemical molecules, as defined by their ability to alter the cell-cell interactions among peripheral mononuclear leukocytes ex vivo, using automated microscopy and population-wide single-cell image analysis. Unexpectedly, ∼10% of the agents tested affected these cell-cell interactions differentially. The results accurately recapitulated known immunomodulatory drug classes and revealed several clinically approved drugs that unexpectedly harbor the ability to modulate the immune system, which could potentially contribute to their physiological mechanism of action. For instance, the kinase inhibitor crizotinib promoted T cell interactions with monocytes, as well as with cancer cells, through inhibition of the receptor tyrosine kinase MSTR1 and subsequent upregulation of the expression of major histocompatibility complex molecules. The approach offers an attractive platform for the personalized identification and characterization of immunomodulatory therapeutics.

Bouché L, Christ CD, Siegel S, Fernández-Montalván AE, Holton SJ, Fedorov O, Ter Laak A, Sugawara T, Stöckigt D, Tallant C et al. 2017. Benzoisoquinolinediones as Potent and Selective Inhibitors of BRPF2 and TAF1/TAF1L Bromodomains. J Med Chem, 60 (9), pp. 4002-4022. | Show Abstract | Read more

Bromodomains (BD) are readers of lysine acetylation marks present in numerous proteins associated with chromatin. Here we describe a dual inhibitor of the bromodomain and PHD finger (BRPF) family member BRPF2 and the TATA box binding protein-associated factors TAF1 and TAF1L. These proteins are found in large chromatin complexes and play important roles in transcription regulation. The substituted benzoisoquinolinedione series was identified by high-throughput screening, and subsequent structure-activity relationship optimization allowed generation of low nanomolar BRPF2 BD inhibitors with strong selectivity against BRPF1 and BRPF3 BDs. In addition, a strong inhibition of TAF1/TAF1L BD2 was measured for most derivatives. The best compound of the series was BAY-299, which is a very potent, dual inhibitor with an IC50 of 67 nM for BRPF2 BD, 8 nM for TAF1 BD2, and 106 nM for TAF1L BD2. Importantly, no activity was measured for BRD4 BDs. Furthermore, cellular activity was evidenced using a BRPF2- or TAF1-histone H3.3 or H4 interaction assay.

Bataille CJR, Brennan MB, Byrne S, Davies SG, Durbin M, Fedorov O, Huber KVM, Jones AM, Knapp S, Liu G et al. 2017. Thiazolidine derivatives as potent and selective inhibitors of the PIM kinase family. Bioorg Med Chem, 25 (9), pp. 2657-2665. | Show Abstract | Read more

The PIM family of serine/threonine kinases have become an attractive target for anti-cancer drug development, particularly for certain hematological malignancies. Here, we describe the discovery of a series of inhibitors of the PIM kinase family using a high throughput screening strategy. Through a combination of molecular modeling and optimization studies, the intrinsic potencies and molecular properties of this series of compounds was significantly improved. An excellent pan-PIM isoform inhibition profile was observed across the series, while optimized examples show good selectivity over other kinases. Two PIM-expressing leukemic cancer cell lines, MV4-11 and K562, were employed to evaluate the in vitro anti-proliferative effects of selected inhibitors. Encouraging activities were observed for many examples, with the best example (44) giving an IC50 of 0.75μM against the K562 cell line. These data provide a promising starting point for further development of this series as a new cancer therapy through PIM kinase inhibition.

Huber KVM. 2017. Target engagement: Shining a light. Nat Chem Biol, 13 (2), pp. 133-134. | Read more

Moustakim M, Clark PGK, Trulli L, Fuentes de Arriba AL, Ehebauer MT, Chaikuad A, Murphy EJ, Mendez-Johnson J, Daniels D, Hou C-FD et al. 2017. Discovery of a PCAF Bromodomain Chemical Probe. Angew Chem Int Ed Engl, 56 (3), pp. 827-831. | Show Abstract | Read more

The p300/CBP-associated factor (PCAF) and related GCN5 bromodomain-containing lysine acetyl transferases are members of subfamily I of the bromodomain phylogenetic tree. Iterative cycles of rational inhibitor design and biophysical characterization led to the discovery of the triazolopthalazine-based L-45 (dubbed L-Moses) as the first potent, selective, and cell-active PCAF bromodomain (Brd) inhibitor. Synthesis from readily available (1R,2S)-(-)-norephedrine furnished L-45 in enantiopure form. L-45 was shown to disrupt PCAF-Brd histone H3.3 interaction in cells using a nanoBRET assay, and a co-crystal structure of L-45 with the homologous Brd PfGCN5 from Plasmodium falciparum rationalizes the high selectivity for PCAF and GCN5 bromodomains. Compound L-45 shows no observable cytotoxicity in peripheral blood mononuclear cells (PBMC), good cell-permeability, and metabolic stability in human and mouse liver microsomes, supporting its potential for in vivo use.

Radic-Sarikas B, Tsafou KP, Emdal KB, Papamarkou T, Huber KVM, Mutz C, Toretsky JA, Bennett KL, Olsen JV, Brunak S et al. 2017. Combinatorial Drug Screening Identifies Ewing Sarcoma-specific Sensitivities. Mol Cancer Ther, 16 (1), pp. 88-101. | Show Abstract | Read more

Improvements in survival for Ewing sarcoma pediatric and adolescent patients have been modest over the past 20 years. Combinations of anticancer agents endure as an option to overcome resistance to single treatments caused by compensatory pathways. Moreover, combinations are thought to lessen any associated adverse side effects through reduced dosing, which is particularly important in childhood tumors. Using a parallel phenotypic combinatorial screening approach of cells derived from three pediatric tumor types, we identified Ewing sarcoma-specific interactions of a diverse set of targeted agents including approved drugs. We were able to retrieve highly synergistic drug combinations specific for Ewing sarcoma and identified signaling processes important for Ewing sarcoma cell proliferation determined by EWS-FLI1 We generated a molecular target profile of PKC412, a multikinase inhibitor with strong synergistic propensity in Ewing sarcoma, revealing its targets in critical Ewing sarcoma signaling routes. Using a multilevel experimental approach including quantitative phosphoproteomics, we analyzed the molecular rationale behind the disease-specific synergistic effect of simultaneous application of PKC412 and IGF1R inhibitors. The mechanism of the drug synergy between these inhibitors is different from the sum of the mechanisms of the single agents. The combination effectively inhibited pathway crosstalk and averted feedback loop repression, in EWS-FLI1-dependent manner. Mol Cancer Ther; 16(1); 88-101. ©2016 AACR.

Martins R, Maier J, Gorki A-D, Huber KVM, Sharif O, Starkl P, Saluzzo S, Quattrone F, Gawish R, Lakovits K et al. 2016. Heme drives hemolysis-induced susceptibility to infection via disruption of phagocyte functions. Nat Immunol, 17 (12), pp. 1361-1372. | Show Abstract | Read more

Hemolysis drives susceptibility to bacterial infections and predicts poor outcome from sepsis. These detrimental effects are commonly considered to be a consequence of heme-iron serving as a nutrient for bacteria. We employed a Gram-negative sepsis model and found that elevated heme levels impaired the control of bacterial proliferation independently of heme-iron acquisition by pathogens. Heme strongly inhibited phagocytosis and the migration of human and mouse phagocytes by disrupting actin cytoskeletal dynamics via activation of the GTP-binding Rho family protein Cdc42 by the guanine nucleotide exchange factor DOCK8. A chemical screening approach revealed that quinine effectively prevented heme effects on the cytoskeleton, restored phagocytosis and improved survival in sepsis. These mechanistic insights provide potential therapeutic targets for patients with sepsis or hemolytic disorders.

Li J, Casteels T, Frogne T, Ingvorsen C, Honoré C, Courtney M, Huber KVM, Schmitner N, Kimmel RA, Romanov RA et al. 2017. Artemisinins Target GABAA Receptor Signaling and Impair α Cell Identity. Cell, 168 (1-2), pp. 86-100.e15. | Show Abstract | Read more

Type 1 diabetes is characterized by the destruction of pancreatic β cells, and generating new insulin-producing cells from other cell types is a major aim of regenerative medicine. One promising approach is transdifferentiation of developmentally related pancreatic cell types, including glucagon-producing α cells. In a genetic model, loss of the master regulatory transcription factor Arx is sufficient to induce the conversion of α cells to functional β-like cells. Here, we identify artemisinins as small molecules that functionally repress Arx by causing its translocation to the cytoplasm. We show that the protein gephyrin is the mammalian target of these antimalarial drugs and that the mechanism of action of these molecules depends on the enhancement of GABAA receptor signaling. Our results in zebrafish, rodents, and primary human pancreatic islets identify gephyrin as a druggable target for the regeneration of pancreatic β cell mass from α cells.

Sdelci S, Lardeau C-H, Tallant C, Klepsch F, Klaiber B, Bennett J, Rathert P, Schuster M, Penz T, Fedorov O et al. 2016. Mapping the chemical chromatin reactivation landscape identifies BRD4-TAF1 cross-talk. Nat Chem Biol, 12 (7), pp. 504-510. | Show Abstract | Read more

Bromodomain-containing proteins of the BET family recognize histone lysine acetylation and mediate transcriptional activation of target genes such as the MYC oncogene. Pharmacological inhibitors of BET domains promise therapeutic benefits in a variety of cancers. We performed a high-diversity chemical compound screen for agents capable of modulating BRD4-dependent heterochromatization of a generic reporter in human cells. In addition to known and new compounds targeting BRD4, we identified small molecules that mimic BRD4 inhibition without direct engagement. One such compound was a potent inhibitor of the second bromodomain of TAF1. Using this inhibitor, we discovered that TAF1 synergizes with BRD4 to control proliferation of cancer cells, making TAF1 an attractive epigenetic target in cancers driven by MYC.

Huber KVM, Superti-Furga G. 2016. Profiling of Small Molecules by Chemical Proteomics. Methods Mol Biol, 1394 pp. 211-218. | Show Abstract | Read more

Chemical proteomics provides a powerful means to gain systems-level insight into the mode of action of small molecules and/or natural products. In contrast to high-throughput screening efforts which only interrogate selected subproteomes such as kinases and often only consider individual domains, the methodology presented herein allows for the determination of the molecular targets of small molecules or drugs in a more relevant physiological setting. As such, the compound of interest is exposed to the entire variety of cellular proteins considering all naturally occurring posttranslational modifications and activation states. Samples prepared according to the procedures described in this protocol are compatible with lysates from cultured cell lines, primary cells, or samples from biopsies. In combination with state-of-the-art mass spectrometry techniques this approach grants access to a comprehensive view of small molecule-target protein interactions.

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. | Read more

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. | 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. | 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

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. | 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.

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. | 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.

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. | 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.

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. | 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.

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. | 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.

Hadzijusufovic E, Albrecht-Schgoer K, Huber K, Grebien F, Eisenwort G, Schgoer W, Kaun C, Herndlhofer S, Theurl M, Cerny-Reiterer S et al. 2014. Further Evaluation of Pro-Atherogenic and Anti-Angiogenic Effects of Nilotinib in Mice and in Patients with Ph-Chromosome plus CML BLOOD, 124 (21),

Hadzijusufovic E, Albrecht-Schgoer K, Huber K, Grebien F, Eisenwort G, Schgoer W, Ghanim V, Sadovnik I, Kaun C, Herndlhofer S et al. 2014. Nilotinib exerts proatherogenic and growth-inhibitory effects on endothelial cells: a potential mechanism underlying drug-related vasculopathy in Ph plus CML ONCOLOGY RESEARCH AND TREATMENT, 37 pp. 300-300.

Kern S, Agarwal S, Huber K, Gehring AP, Strödke B, Wirth CC, Brügl T, Abodo LO, Dandekar T, Doerig C et al. 2014. Inhibition of the SR protein-phosphorylating CLK kinases of Plasmodium falciparum impairs blood stage replication and malaria transmission. PLoS One, 9 (9), pp. e105732. | Show Abstract | Read more

Cyclin-dependent kinase-like kinases (CLKs) are dual specificity protein kinases that phosphorylate Serine/Arginine-rich (SR) proteins involved in pre-mRNA processing. Four CLKs, termed PfCLK-1-4, can be identified in the human malaria parasite Plasmodium falciparum, which show homology with the yeast SR protein kinase Sky1p. The four PfCLKs are present in the nucleus and cytoplasm of the asexual blood stages and of gametocytes, sexual precursor cells crucial for malaria parasite transmission from humans to mosquitoes. We identified three plasmodial SR proteins, PfSRSF12, PfSFRS4 and PfSF-1, which are predominantly present in the nucleus of blood stage trophozoites, PfSRSF12 and PfSF-1 are further detectable in the nucleus of gametocytes. We found that recombinantly expressed SR proteins comprising the Arginine/Serine (RS)-rich domains were phosphorylated by the four PfCLKs in in vitro kinase assays, while a recombinant PfSF-1 peptide lacking the RS-rich domain was not phosphorylated. Since it was hitherto not possible to knock-out the pfclk genes by conventional gene disruption, we aimed at chemical knock-outs for phenotype analysis. We identified five human CLK inhibitors, belonging to the oxo-β-carbolines and aminopyrimidines, as well as the antiseptic chlorhexidine as PfCLK-targeting compounds. The six inhibitors block P. falciparum blood stage replication in the low micromolar to nanomolar range by preventing the trophozoite-to-schizont transformation. In addition, the inhibitors impair gametocyte maturation and gametogenesis in in vitro assays. The combined data show that the four PfCLKs are involved in phosphorylation of SR proteins with essential functions for the blood and sexual stages of the malaria parasite, thus pointing to the kinases as promising targets for antimalarial and transmission blocking drugs.

Winter GE, Radic B, Mayor-Ruiz C, Blomen VA, Trefzer C, Kandasamy RK, Huber KVM, Gridling M, Chen D, Klampfl T et al. 2014. The solute carrier SLC35F2 enables YM155-mediated DNA damage toxicity. Nat Chem Biol, 10 (9), pp. 768-773. | Show Abstract | Read more

Genotoxic chemotherapy is the most common cancer treatment strategy. However, its untargeted generic DNA-damaging nature and associated systemic cytotoxicity greatly limit its therapeutic applications. Here, we used a haploid genetic screen in human cells to discover an absolute dependency of the clinically evaluated anticancer compound YM155 on solute carrier family member 35 F2 (SLC35F2), an uncharacterized member of the solute carrier protein family that is highly expressed in a variety of human cancers. YM155 generated DNA damage through intercalation, which was contingent on the expression of SLC35F2 and its drug-importing activity. SLC35F2 expression and YM155 sensitivity correlated across a panel of cancer cell lines, and targeted genome editing verified SLC35F2 as the main determinant of YM155-mediated DNA damage toxicity in vitro and in vivo. These findings suggest a new route to targeted DNA damage by exploiting tumor and patient-specific import of YM155.

Colinge J, César-Razquin A, Huber K, Breitwieser FP, Májek P, Superti-Furga G. 2014. Building and exploring an integrated human kinase network: global organization and medical entry points. J Proteomics, 107 pp. 113-127. | Show Abstract | Read more

UNLABELLED: Biological matter is organized in functional networks of different natures among which kinase-substrate and protein-protein interactions play an important role. Large public data collections allowed us to compile an important corpus of interaction data around human protein kinases. One of the most interesting observations analyzing this network is that coherence in kinase functional activity relies on kinase substrate interactions primarily and not on which protein complexes are formed around them. Further dissecting the two types of interactions at the level of kinase groups (CMGCs, Tyrosine kinases, etc.) we show a prevalence of intra-group interconnectivity, which we can naturally relate to current scenarios of evolution of biological networks. Tracking publication dates we observe high correlation of kinase interaction research focus with general kinase research. We find a similar bias in the targets of kinase inhibitors that feature high redundancy. Finally, intersecting kinase inhibitor specificity with sets of kinases located at specific positions in the kinase network, we propose alternative options for future therapeutic strategies using these compounds. BIOLOGICAL SIGNIFICANCE: Despite its importance for cellular regulation and the fact that protein kinases feature prominent targets of modern therapeutic approaches, the structure and logic of the global, integrated protein phosphorylation network have not been investigated intensively. To focus on the regulatory skeleton of the phosphorylation network, we contemplated a network consisting of kinases, their substrates, and publicly available physical protein interactions. Analysis of this network at multiple levels allowed establishing a series of interesting properties such as prevalence of kinase substrate interactions as opposed to general protein-protein interactions for establishing a holistic control over kinases activities. Kinases controlling many or a few only other kinases, in addition to non-kinases, were distributed in cellular compartments differently. They were also targeted by kinase inhibitors with distinct success rates. Non-kinases tightly regulated by a large number of kinases were involved in biological processes both specific and shared with their regulators while being preferably localized in the nucleus. Collectively, these observations may provide for a new perspective in the elaboration of pharmacological intervention strategies. We complemented our study of kinase interactions with a perspective of how this type of data is generated in comparison with general research about those enzymes. Namely, what was the temporal evolution of the research community attention for interaction versus non-interaction-based kinase experiments. This article is part of a Special Issue entitled: "20years of Proteomics" in memory of Viatliano Pallini" Guest Editors: Luca Bini, Juan J. Calvete, Natacha Turck, Denis Hochstrasser and Jean-Charles Sanchez.

Giansanti P, Preisinger C, Huber KVM, Gridling M, Superti-Furga G, Bennett KL, Heck AJR. 2014. Evaluating the promiscuous nature of tyrosine kinase inhibitors assessed in A431 epidermoid carcinoma cells by both chemical- and phosphoproteomics. ACS Chem Biol, 9 (7), pp. 1490-1498. | Show Abstract | Read more

Deregulation of protein tyrosine kinase signaling has been linked to many diseases, most notably cancer. As a consequence, small molecule inhibitors of protein tyrosine kinases may provide powerful strategies for treatment. Following the successful introduction of imatinib in the treatment of chronic myelogenous leukemia, such drugs are also now evaluated for other types of cancer. However, many developed kinase inhibitors are not very target-specific and therefore may induce side effects. The importance of such side effects is certainly cell-proteome dependent. Understanding the all-inclusive action of a tyrosine kinase inhibitor on each individual cell-type entails the identification of potential targets, combined with monitoring the downstream effects revealing the signaling networks involved. Here, we explored a multilevel quantitative mass spectrometry-based proteomic strategy to identify the direct targets and downstream signaling effect of four tyrosine kinase inhibitors (imatinib, dasatinib, bosutinib, and nilotinib) in epidermoid carcinoma cells, as a model system for skin-cancer. More than 25 tyrosine kinases showed affinity to the drugs, with imatinib and nilotinib displaying a high specificity, especially when compared to dasatinib and bosutinib. Consequently, the latter two drugs showed a larger effect on downstream phosphotyrosine signaling. Many of the proteins affected are key regulators in cell adhesion and invasion. Our data represents a multiplexed view on the promiscuous action of certain tyrosine kinase inhibitors that needs to be taking into consideration prior to the application of these drugs in the treatment of different forms of cancer.

Veiga-Santos P, Reignault LC, Huber K, Bracher F, De Souza W, De Carvalho TMU. 2014. Inhibition of NAD+-dependent histone deacetylases (sirtuins) causes growth arrest and activates both apoptosis and autophagy in the pathogenic protozoan Trypanosoma cruzi. Parasitology, 141 (6), pp. 814-825. | Show Abstract | Read more

Chagas disease, which is caused by the parasite Trypanosoma cruzi, affects approximately 7-8 million people in Latin America. The drugs available to treat this disease are ineffective against chronic phase disease and are associated with toxic side effects. Therefore, the development of new compounds that can kill T. cruzi at low concentrations is critically important. Herein, we report the effects of a novel 3-arylideneindolin-2-one that inhibits sirtuins, which are highly conserved proteins that are involved in a variety of physiological processes. The compound KH-TFMDI was tested against the epimastigote, trypomastigote and amastigote forms of T. cruzi, and its effects were evaluated using flow cytometry, light and electron microscopy. KH-TFMDI inhibited the replication of T. cruzi intracellular amastigotes with an IC50 of 0.5 ± 0.2 μM, which is significantly lower than the IC50 of benznidazole. The compound also lysed the highly infectious bloodstream trypomastigotes (BST) with LC50 values of 0.8 ± 0.3 μM at 4 °C and 2.5 ± 1.1 μM at 37 °C. KH-TFMDI inhibited cytokinesis and induced several morphological changes in the parasite, leading to its death by apoptosis and autophagy. This study highlights sirtuins as a potential new target for Chagas disease therapy.

Huber KVM, Salah E, Radic B, Gridling M, Elkins JM, Stukalov A, Jemth A-S, Göktürk C, Sanjiv K, Strömberg K et al. 2014. Stereospecific targeting of MTH1 by (S)-crizotinib as an anticancer strategy. Nature, 508 (7495), pp. 222-227. | Show Abstract | Read more

Activated RAS GTPase signalling is a critical driver of oncogenic transformation and malignant disease. Cellular models of RAS-dependent cancers have been used to identify experimental small molecules, such as SCH51344, but their molecular mechanism of action remains generally unknown. Here, using a chemical proteomic approach, we identify the target of SCH51344 as the human mutT homologue MTH1 (also known as NUDT1), a nucleotide pool sanitizing enzyme. Loss-of-function of MTH1 impaired growth of KRAS tumour cells, whereas MTH1 overexpression mitigated sensitivity towards SCH51344. Searching for more drug-like inhibitors, we identified the kinase inhibitor crizotinib as a nanomolar suppressor of MTH1 activity. Surprisingly, the clinically used (R)-enantiomer of the drug was inactive, whereas the (S)-enantiomer selectively inhibited MTH1 catalytic activity. Enzymatic assays, chemical proteomic profiling, kinome-wide activity surveys and MTH1 co-crystal structures of both enantiomers provide a rationale for this remarkable stereospecificity. Disruption of nucleotide pool homeostasis via MTH1 inhibition by (S)-crizotinib induced an increase in DNA single-strand breaks, activated DNA repair in human colon carcinoma cells, and effectively suppressed tumour growth in animal models. Our results propose (S)-crizotinib as an attractive chemical entity for further pre-clinical evaluation, and small-molecule inhibitors of MTH1 in general as a promising novel class of anticancer agents.

Dürnberger G, Bürckstümmer T, Huber K, Giambruno R, Doerks T, Karayel E, Burkard TR, Kaupe I, Müller AC, Schönegger A et al. 2013. Experimental characterization of the human non-sequence-specific nucleic acid interactome. Genome Biol, 14 (7), pp. R81. | Show Abstract | Read more

BACKGROUND: The interactions between proteins and nucleic acids have a fundamental function in many biological processes, including gene transcription, RNA homeostasis, protein translation and pathogen sensing for innate immunity. While our knowledge of the ensemble of proteins that bind individual mRNAs in mammalian cells has been greatly augmented by recent surveys, no systematic study on the non-sequence-specific engagement of native human proteins with various types of nucleic acids has been reported. RESULTS: We designed an experimental approach to achieve broad coverage of the non-sequence-specific RNA and DNA binding space, including methylated cytosine, and tested for interaction potential with the human proteome. We used 25 rationally designed nucleic acid probes in an affinity purification mass spectrometry and bioinformatics workflow to identify proteins from whole cell extracts of three different human cell lines. The proteins were profiled for their binding preferences to the different general types of nucleic acids. The study identified 746 high-confidence direct binders, 139 of which were novel and 237 devoid of previous experimental evidence. We could assign specific affinities for sub-types of nucleic acid probes to 219 distinct proteins and individual domains. The evolutionarily conserved protein YB-1, previously associated with cancer and drug resistance, was shown to bind methylated cytosine preferentially, potentially conferring upon YB-1 an epigenetics-related function. CONCLUSIONS: The dataset described here represents a rich resource of experimentally determined nucleic acid-binding proteins, and our methodology has great potential for further exploration of the interface between the protein and nucleic acid realms.

Weirauch U, Beckmann N, Thomas M, Grünweller A, Huber K, Bracher F, Hartmann RK, Aigner A. 2013. Functional role and therapeutic potential of the pim-1 kinase in colon carcinoma. Neoplasia, 15 (7), pp. 783-794. | Show Abstract | Read more

PURPOSE: The provirus integration site for Moloney murine leukemia virus 1 (Pim-1) kinase is overexpressed in various tumors and has been linked to poor prognosis. Its role as proto-oncogene is based on several Pim-1 target proteins involved in pivotal cellular processes. Here, we explore the functional relevance of Pim-1 in colon carcinoma. EXPERIMENTAL DESIGN: RNAi-based knockdown approaches, as well as a specific small molecule inhibitor, were used to inhibit Pim-1 in colon carcinoma cells. The effects were analyzed regarding proliferation, apoptosis, sensitization toward cytostatic treatment, and overall antitumor effect in vitro and in mouse tumor models in vivo. RESULTS: We demonstrate antiproliferative, proapoptotic, and overall antitumor effects of Pim-1 inhibition. The sensitization to 5-fluorouracil (5-FU) treatment upon Pim-1 knockdown offers new possibilities for combinatorial treatment approaches. Importantly, this also antagonizes a 5-FU-triggered Pim-1 up-regulation, which is mediated by decreased levels of miR-15b, a microRNA we newly identify to regulate Pim-1. The analysis of the molecular effects of Pim-1 inhibition reveals a complex regulatory network, with therapeutic Pim-1 repression leading to major changes in oncogenic signal transduction with regard to p21(Cip1/WAF1), STAT3, c-jun-N-terminal kinase (JNK), c-Myc, and survivin and in the levels of apoptosis-related proteins Puma, Bax, and Bcl-xL. CONCLUSIONS: We demonstrate that Pim-1 plays a pivotal role in several tumor-relevant signaling pathways and establish the functional relevance of Pim-1 in colon carcinoma. Our results also substantiate the RNAi-mediated Pim-1 knockdown based on polymeric polyethylenimine/small interfering RNA nanoparticles as a promising therapeutic approach.

Eisenreich A, Zakrzewicz A, Huber K, Thierbach H, Pepke W, Goldin-Lang P, Schultheiss H-P, Pries A, Rauch U. 2013. Regulation of pro-angiogenic tissue factor expression in hypoxia-induced human lung cancer cells. Oncol Rep, 30 (1), pp. 462-470. | Show Abstract | Read more

Alternative splicing is a key regulatory mechanism for cellular metabolism controlling cell proliferation and angiogenesis, both of which are crucial processes for tumorigenesis under hypoxia. Human cells express two tissue factor (TF) isoforms, alternatively spliced TF (asTF) and 'full length' TF (flTF). flTF is the major source of thrombogenicity whereas, the function of soluble asTF, particularly in cancer, is widely unknown. In the present study, we examined the impact of alternative splicing on the pro-angiogenic potential and the TF expression pattern of A549 cells under hypoxia. We focused our efforts toward alternative splicing factors, such as Clk1, and pro-angiogenic proliferation-regulating factors, such as Cyr61. We further examined the influence of asTF overexpression on the expression of MCP-1, Cyr61 and VEGF, as well as on cell number and pro-angiogenic properties of A549 cells. Notably, we found hypoxia to induce the expression of alternative splicing factors (Clk1 and Clk4) as well as proliferation- and angiogenesis-promoting factors (Cyr61 and flTF). asTF overexpression in A549 cells also increased both cell number and tube formation. These effects were mediated by the induction of Cyr61, MCP-1 and VEGF, as well as by integrin α(v)β(3). Taken together, our results suggest that the pro-angiogenic potential of A549 lung cancer cells is modulated under hypoxic conditions via modulation of TF isoform expression which in turn is controlled by alternative splicing.

Huber K, Brault L, Fedorov O, Gasser C, Filippakopoulos P, Bullock AN, Fabbro D, Trappe J, Schwaller J, Knapp S, Bracher F. 2012. 7,8-dichloro-1-oxo-β-carbolines as a versatile scaffold for the development of potent and selective kinase inhibitors with unusual binding modes. J Med Chem, 55 (1), pp. 403-413. | Show Abstract | Read more

Development of both potent and selective kinase inhibitors is a challenging task in modern drug discovery. The innate promiscuity of kinase inhibitors largely results from ATP-mimetic binding to the kinase hinge region. We present a novel class of substituted 7,8-dichloro-1-oxo-β-carbolines based on the distinct structural features of the alkaloid bauerine C whose kinase inhibitory activity does not rely on canonical ATP-mimetic hinge interactions. Intriguingly, cocrystal structures revealed an unexpected inverted binding mode and the presence of halogen bonds with kinase backbone residues. The compounds exhibit excellent selectivity over a comprehensive panel of human protein kinases while inhibiting selected kinases such as the oncogenic PIM1 at low nanomolar concentrations. Together, our biochemical and structural data suggest that this scaffold may serve as a valuable template for the design and development of specific inhibitors of various kinases including the PIM family of kinases, CLKs, DAPK3 (ZIPK), BMP2K (BIKE), and others.

Huber K, Superti-Furga G. 2011. After the grape rush: sirtuins as epigenetic drug targets in neurodegenerative disorders. Bioorg Med Chem, 19 (12), pp. 3616-3624. | Show Abstract | Read more

Class III histone deacetylases (sirtuins) are becoming increasingly recognized as important epigenetic drug targets in cancer and metabolic disorders. As key regulators involved in numerous cellular signalling pathways, sirtuins are also emerging as potential targets in various neurodegenerative diseases such as Alzheimer, Parkinson's disease and others, thus suggesting modulation of sirtuin activity could provide an interesting and novel therapeutic option. In particular, much attention has been raised by neuroprotective effects attributed to SIRT1 activation due to genetically induced sirtuin overexpression or administration of resveratrol, a natural compound found in the skin of red grapes and also in wine. Similarly, also sirtuin inhibitors display benefits in various neuropathologic disease models. In light of the growing interest in sirtuin modulation and with regard to the lack of conclusive data on small molecule activators of sirtuins this review recapitulates the known facts about sirtuins and their relevance in neurodegenerative diseases.

Fedorov O, Huber K, Eisenreich A, Filippakopoulos P, King O, Bullock AN, Szklarczyk D, Jensen LJ, Fabbro D, Trappe J et al. 2011. Specific CLK inhibitors from a novel chemotype for regulation of alternative splicing. Chem Biol, 18 (1), pp. 67-76. | Show Abstract | Read more

There is a growing recognition of the importance of protein kinases in the control of alternative splicing. To define the underlying regulatory mechanisms, highly selective inhibitors are needed. Here, we report the discovery and characterization of the dichloroindolyl enaminonitrile KH-CB19, a potent and highly specific inhibitor of the CDC2-like kinase isoforms 1 and 4 (CLK1/CLK4). Cocrystal structures of KH-CB19 with CLK1 and CLK3 revealed a non-ATP mimetic binding mode, conformational changes in helix αC and the phosphate binding loop and halogen bonding to the kinase hinge region. KH-CB19 effectively suppressed phosphorylation of SR (serine/arginine) proteins in cells, consistent with its expected mechanism of action. Chemical inhibition of CLK1/CLK4 generated a unique pattern of splicing factor dephosphorylation and had at low nM concentration a profound effect on splicing of the two tissue factor isoforms flTF (full-length TF) and asHTF (alternatively spliced human TF).

Huber K, Kast O, Bracher F. 2010. A Versatile Synthesis of 3-Substituted 4-Cyano-1,2,3,4-tetrahydro-1-oxo-beta-carbolines SYNTHESIS-STUTTGART, 2010 (22), pp. 3849-3854. | Show Abstract | Read more

In a project aimed at the synthesis of analogues of the cytotoxic -carboline alkaloid bauerine C with more advantageous solubility properties, a 3-amino analogue was prepared by treating ethyl 3-(cyanomethyl)indole-2- carboxylate with ammonia. Upon addition of aldehydes or ketones to the reaction mixture, 3-substituted 4-cyano-1,2,3,4-tetrahydro-1-oxo - carbolines were obtained in a one-pot condensation. When cyclic ketones are used, the procedure allows a convenient synthesis of tetracyclic spiro compounds. © Georg Thieme Verlag Stuttgart · New York.

Brault L, Gasser C, Bracher F, Huber K, Knapp S, Schwaller J. 2010. PIM serine/threonine kinases in the pathogenesis and therapy of hematologic malignancies and solid cancers. Haematologica, 95 (6), pp. 1004-1015. | Show Abstract | Read more

The identification as cooperating targets of Proviral Integrations of Moloney virus in murine lymphomas suggested early on that PIM serine/threonine kinases play an important role in cancer biology. Whereas elevated levels of PIM1 and PIM2 were mostly found in hematologic malignancies and prostate cancer, increased PIM3 expression was observed in different solid tumors. PIM kinases are constitutively active and their activity supports in vitro and in vivo tumor cell growth and survival through modification of an increasing number of common as well as isoform-specific substrates including several cell cycle regulators and apoptosis mediators. PIM1 but not PIM2 seems also to mediate homing and migration of normal and malignant hematopoietic cells by regulating chemokine receptor surface expression. Knockdown experiments by RNA interference or dominant-negative acting mutants suggested that PIM kinases are important for maintenance of a transformed phenotype and therefore potential therapeutic targets. Determination of the protein structure facilitated identification of an increasing number of potent small molecule PIM kinase inhibitors with in vitro and in vivo anticancer activity. Ongoing efforts aim to identify isoform-specific PIM inhibitors that would not only help to dissect the kinase function but hopefully also provide targeted therapeutics. Here, we summarize the current knowledge about the role of PIM serine/threonine kinases for the pathogenesis and therapy of hematologic malignancies and solid cancers, and we highlight structural principles and recent progress on small molecule PIM kinase inhibitors that are on their way into first clinical trials.

Huber K, Schemies J, Uciechowska U, Wagner JM, Rumpf T, Lewrick F, Süss R, Sippl W, Jung M, Bracher F. 2010. Novel 3-arylideneindolin-2-ones as inhibitors of NAD+ -dependent histone deacetylases (sirtuins). J Med Chem, 53 (3), pp. 1383-1386. | Show Abstract | Read more

Class III histone deacetylases (sirtuins) play pivotal roles in many cellular processes. They are linked to extended lifespan and to the pathogenesis of cancer and neuronal disorders. We present novel sirtuin inhibitors based on a 6,7-dichloro-2-oxindole scaffold with low micromolar activity. In vitro activity was rationalized by docking studies, and hyperacetylation of sirtuin targets could be demonstrated in cell culture.

Huber K, Bracher F. 2007. Cytotoxic hybrids between the aromatic alkaloids bauerine C and rutaecarpine ZEITSCHRIFT FUR NATURFORSCHUNG SECTION B-A JOURNAL OF CHEMICAL SCIENCES, 62 (10), pp. 1313-1316. | Show Abstract | Read more

<jats:p>Two hybrids between the alkaloids bauerine C and rutaecarpine were prepared. Screening for cytotoxic activity revealed that introduction of two chlorine substituents to the quinazolinocarboline core of rutaecarpine strongly enhances cytotoxic activity, whereas methylation at the indole nitrogen is detrimental to activity.</jats:p>

Resnick E, Bradley A, Gan J, Douangamath A, Krojer T, Sethi R, Geurink PP, Aimon A, Amitai G, Bellini D et al. 2019. Rapid Covalent-Probe Discovery by Electrophile-Fragment Screening. J Am Chem Soc, 141 (22), pp. 8951-8968. | Show Abstract | Read more

Covalent probes can display unmatched potency, selectivity, and duration of action; however, their discovery is challenging. In principle, fragments that can irreversibly bind their target can overcome the low affinity that limits reversible fragment screening, but such electrophilic fragments were considered nonselective and were rarely screened. We hypothesized that mild electrophiles might overcome the selectivity challenge and constructed a library of 993 mildly electrophilic fragments. We characterized this library by a new high-throughput thiol-reactivity assay and screened them against 10 cysteine-containing proteins. Highly reactive and promiscuous fragments were rare and could be easily eliminated. In contrast, we found hits for most targets. Combining our approach with high-throughput crystallography allowed rapid progression to potent and selective probes for two enzymes, the deubiquitinase OTUB2 and the pyrophosphatase NUDT7. No inhibitors were previously known for either. This study highlights the potential of electrophile-fragment screening as a practical and efficient tool for covalent-ligand discovery.

Scheer S, Ackloo S, Medina TS, Schapira M, Li F, Ward JA, Lewis AM, Northrop JP, Richardson PL, Kaniskan HÜ et al. 2019. A chemical biology toolbox to study protein methyltransferases and epigenetic signaling. Nat Commun, 10 (1), pp. 19. | Show Abstract | Read more

Protein methyltransferases (PMTs) comprise a major class of epigenetic regulatory enzymes with therapeutic relevance. Here we present a collection of chemical probes and associated reagents and data to elucidate the function of human and murine PMTs in cellular studies. Our collection provides inhibitors and antagonists that together modulate most of the key regulatory methylation marks on histones H3 and H4, providing an important resource for modulating cellular epigenomes. We describe a comprehensive and comparative characterization of the probe collection with respect to their potency, selectivity, and mode of inhibition. We demonstrate the utility of this collection in CD4+ T cell differentiation assays revealing the potential of individual probes to alter multiple T cell subpopulations which may have implications for T cell-mediated processes such as inflammation and immuno-oncology. In particular, we demonstrate a role for DOT1L in limiting Th1 cell differentiation and maintaining lineage integrity. This chemical probe collection and associated data form a resource for the study of methylation-mediated signaling in epigenetics, inflammation and beyond.

Moustakim M, Christott T, Monteiro OP, Bennett J, Giroud C, Ward J, Rogers CM, Smith P, Panagakou I, Díaz-Sáez L et al. 2018. Discovery of an MLLT1/3 YEATS Domain Chemical Probe. Angew Chem Int Ed Engl, 57 (50), pp. 16302-16307. | Show Abstract | Read more

YEATS domain (YD) containing proteins are an emerging class of epigenetic targets in drug discovery. Dysregulation of these modified lysine-binding proteins has been linked to the onset and progression of cancers. We herein report the discovery and characterisation of the first small-molecule chemical probe, SGC-iMLLT, for the YD of MLLT1 (ENL/YEATS1) and MLLT3 (AF9/YEATS3). SGC-iMLLT is a potent and selective inhibitor of MLLT1/3-histone interactions. Excellent selectivity over other human YD proteins (YEATS2/4) and bromodomains was observed. Furthermore, our probe displays cellular target engagement of MLLT1 and MLLT3. The first small-molecule X-ray co-crystal structures with the MLLT1 YD are also reported. This first-in-class probe molecule can be used to understand MLLT1/3-associated biology and the therapeutic potential of small-molecule YD inhibitors.

Stefaniak J, Lewis AM, Conole D, Galan SRG, Bataille CJR, Wynne GM, Castaldi MP, Lundbäck T, Russell AJ, Huber KVM. 2018. Chemical Instability and Promiscuity of Arylmethylidenepyrazolinone-Based MDMX Inhibitors. ACS Chem Biol, 13 (10), pp. 2849-2854. | Show Abstract | Read more

Targeting the protein-protein interaction between p53 and MDM2/MDMX (MDM4) represents an attractive anticancer strategy for the treatment of p53-competent tumors. Several selective and potent MDM2 inhibitors have been developed and entered the clinic; however, the repertoire of MDMX antagonists is still limited. The arylmethylidenepyrazolinone SJ-172550 has been reported as a selective MDMX antagonist; yet, uncertainties about its mechanism of action have raised doubts about its use as a chemical probe. Here, we show that, in addition to its unclear mode of action, SJ-172550 is unstable in aqueous buffers, giving rise to side products of unknown biological activity. Using an SJ-172550-derived affinity probe, we observed promiscuous binding to cellular proteins whereas cellular thermal shift assays did not reveal a stabilizing effect on MDMX. Overall, our results raise further questions about the interpretation of data using SJ-172550 and related compounds to investigate cellular phenotypes.

Hrdinka M, Schlicher L, Dai B, Pinkas DM, Bufton JC, Picaud S, Ward JA, Rogers C, Suebsuwong C, Nikhar S et al. 2018. Small molecule inhibitors reveal an indispensable scaffolding role of RIPK2 in NOD2 signaling. EMBO J, 37 (17), pp. e99372-e99372. | Show Abstract | Read more

RIPK2 mediates inflammatory signaling by the bacteria-sensing receptors NOD1 and NOD2. Kinase inhibitors targeting RIPK2 are a proposed strategy to ameliorate NOD-mediated pathologies. Here, we reveal that RIPK2 kinase activity is dispensable for NOD2 inflammatory signaling and show that RIPK2 inhibitors function instead by antagonizing XIAP-binding and XIAP-mediated ubiquitination of RIPK2. We map the XIAP binding site on RIPK2 to the loop between β2 and β3 of the N-lobe of the kinase, which is in close proximity to the ATP-binding pocket. Through characterization of a new series of ATP pocket-binding RIPK2 inhibitors, we identify the molecular features that determine their inhibition of both the RIPK2-XIAP interaction, and of cellular and in vivoNOD2 signaling. Our study exemplifies how targeting of the ATP-binding pocket in RIPK2 can be exploited to interfere with the RIPK2-XIAP interaction for modulation of NOD signaling.

Fernández-Montalván AE, Berger M, Kuropka B, Koo SJ, Badock V, Weiske J, Puetter V, Holton SJ, Stöckigt D, Ter Laak A et al. 2017. Isoform-Selective ATAD2 Chemical Probe with Novel Chemical Structure and Unusual Mode of Action. ACS Chem Biol, 12 (11), pp. 2730-2736. | Show Abstract | Read more

ATAD2 (ANCCA) is an epigenetic regulator and transcriptional cofactor, whose overexpression has been linked to the progress of various cancer types. Here, we report a DNA-encoded library screen leading to the discovery of BAY-850, a potent and isoform selective inhibitor that specifically induces ATAD2 bromodomain dimerization and prevents interactions with acetylated histones in vitro, as well as with chromatin in cells. These features qualify BAY-850 as a chemical probe to explore ATAD2 biology.

Vasta JD, Corona CR, Wilkinson J, Zimprich CA, Hartnett JR, Ingold MR, Zimmerman K, Machleidt T, Kirkland TA, Huwiler KG et al. 2018. Quantitative, Wide-Spectrum Kinase Profiling in Live Cells for Assessing the Effect of Cellular ATP on Target Engagement. Cell Chem Biol, 25 (2), pp. 206-214.e11. | Show Abstract | Read more

For kinase inhibitors, intracellular target selectivity is fundamental to pharmacological mechanism. Although a number of acellular techniques have been developed to measure kinase binding or enzymatic inhibition, such approaches can fail to accurately predict engagement in cells. Here we report the application of an energy transfer technique that enabled the first broad-spectrum, equilibrium-based approach to quantitatively profile target occupancy and compound affinity in live cells. Using this method, we performed a selectivity profiling for clinically relevant kinase inhibitors against 178 full-length kinases, and a mechanistic interrogation of the potency offsets observed between cellular and biochemical analysis. For the multikinase inhibitor crizotinib, our approach accurately predicted cellular potency and revealed improved target selectivity compared with biochemical measurements. Due to cellular ATP, a number of putative crizotinib targets are unexpectedly disengaged in live cells at a clinically relevant drug dose.

Vladimer GI, Snijder B, Krall N, Bigenzahn JW, Huber KVM, Lardeau C-H, Sanjiv K, Ringler A, Berglund UW, Sabler M et al. 2017. Global survey of the immunomodulatory potential of common drugs. Nat Chem Biol, 13 (6), pp. 681-690. | Show Abstract | Read more

Small-molecule drugs may complement antibody-based therapies in an immune-oncology setting, yet systematic methods for the identification and characterization of the immunomodulatory properties of these entities are lacking. We surveyed the immumomodulatory potential of 1,402 small chemical molecules, as defined by their ability to alter the cell-cell interactions among peripheral mononuclear leukocytes ex vivo, using automated microscopy and population-wide single-cell image analysis. Unexpectedly, ∼10% of the agents tested affected these cell-cell interactions differentially. The results accurately recapitulated known immunomodulatory drug classes and revealed several clinically approved drugs that unexpectedly harbor the ability to modulate the immune system, which could potentially contribute to their physiological mechanism of action. For instance, the kinase inhibitor crizotinib promoted T cell interactions with monocytes, as well as with cancer cells, through inhibition of the receptor tyrosine kinase MSTR1 and subsequent upregulation of the expression of major histocompatibility complex molecules. The approach offers an attractive platform for the personalized identification and characterization of immunomodulatory therapeutics.

Bouché L, Christ CD, Siegel S, Fernández-Montalván AE, Holton SJ, Fedorov O, Ter Laak A, Sugawara T, Stöckigt D, Tallant C et al. 2017. Benzoisoquinolinediones as Potent and Selective Inhibitors of BRPF2 and TAF1/TAF1L Bromodomains. J Med Chem, 60 (9), pp. 4002-4022. | Show Abstract | Read more

Bromodomains (BD) are readers of lysine acetylation marks present in numerous proteins associated with chromatin. Here we describe a dual inhibitor of the bromodomain and PHD finger (BRPF) family member BRPF2 and the TATA box binding protein-associated factors TAF1 and TAF1L. These proteins are found in large chromatin complexes and play important roles in transcription regulation. The substituted benzoisoquinolinedione series was identified by high-throughput screening, and subsequent structure-activity relationship optimization allowed generation of low nanomolar BRPF2 BD inhibitors with strong selectivity against BRPF1 and BRPF3 BDs. In addition, a strong inhibition of TAF1/TAF1L BD2 was measured for most derivatives. The best compound of the series was BAY-299, which is a very potent, dual inhibitor with an IC50 of 67 nM for BRPF2 BD, 8 nM for TAF1 BD2, and 106 nM for TAF1L BD2. Importantly, no activity was measured for BRD4 BDs. Furthermore, cellular activity was evidenced using a BRPF2- or TAF1-histone H3.3 or H4 interaction assay.

Huber KVM. 2017. Target engagement: Shining a light. Nat Chem Biol, 13 (2), pp. 133-134. | Read more

Martins R, Maier J, Gorki A-D, Huber KVM, Sharif O, Starkl P, Saluzzo S, Quattrone F, Gawish R, Lakovits K et al. 2016. Heme drives hemolysis-induced susceptibility to infection via disruption of phagocyte functions. Nat Immunol, 17 (12), pp. 1361-1372. | Show Abstract | Read more

Hemolysis drives susceptibility to bacterial infections and predicts poor outcome from sepsis. These detrimental effects are commonly considered to be a consequence of heme-iron serving as a nutrient for bacteria. We employed a Gram-negative sepsis model and found that elevated heme levels impaired the control of bacterial proliferation independently of heme-iron acquisition by pathogens. Heme strongly inhibited phagocytosis and the migration of human and mouse phagocytes by disrupting actin cytoskeletal dynamics via activation of the GTP-binding Rho family protein Cdc42 by the guanine nucleotide exchange factor DOCK8. A chemical screening approach revealed that quinine effectively prevented heme effects on the cytoskeleton, restored phagocytosis and improved survival in sepsis. These mechanistic insights provide potential therapeutic targets for patients with sepsis or hemolytic disorders.

Li J, Casteels T, Frogne T, Ingvorsen C, Honoré C, Courtney M, Huber KVM, Schmitner N, Kimmel RA, Romanov RA et al. 2017. Artemisinins Target GABAA Receptor Signaling and Impair α Cell Identity. Cell, 168 (1-2), pp. 86-100.e15. | Show Abstract | Read more

Type 1 diabetes is characterized by the destruction of pancreatic β cells, and generating new insulin-producing cells from other cell types is a major aim of regenerative medicine. One promising approach is transdifferentiation of developmentally related pancreatic cell types, including glucagon-producing α cells. In a genetic model, loss of the master regulatory transcription factor Arx is sufficient to induce the conversion of α cells to functional β-like cells. Here, we identify artemisinins as small molecules that functionally repress Arx by causing its translocation to the cytoplasm. We show that the protein gephyrin is the mammalian target of these antimalarial drugs and that the mechanism of action of these molecules depends on the enhancement of GABAA receptor signaling. Our results in zebrafish, rodents, and primary human pancreatic islets identify gephyrin as a druggable target for the regeneration of pancreatic β cell mass from α cells.

Drug Target Identification Using Chemoproteomic Approaches

Many cell-active compounds exert their phenotype by modulating the activity of several proteins at the same time – a phenomenon known as “polypharmacology”. Considering the number and complexity of expressed proteins in every cell it is not surprising that many bioactive compounds bind to multiple target proteins. Knowledge about these targets is important to understand the mechanism by which the drug exhibits its phenotype and can provide so-called biomarkers that can help to ensure that only ...

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Structure and Function of AAA ATPases

ATPases Associated with diverse cellular Activities (AAA) represent a diverse family of enzymes involved in a variety of fundamental cellular processes such as signal transduction and gene expression. AAA ATPases utilise the energy generated by nucleotide hydrolysis to remodel the structure of macromolecules or translocate proteins. Several AAA members are linked to the modulation of immunomodulatory processes and cancer progression. As such, these highly conserved proteins are of great ...

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Understanding the Role of Vitamin B6 Homeostasis in Health and Disease

The active form of vitamin B6, namely pyridoxal 5’-phosphate (PLP), is a versatile enzyme catalyst with a double-edged sword. On one hand PLP is an essential cofactor for >4% of all enzymes. On the other, PLP imbalance in the cell is the cause of several inherited epilepsy disorders, and is associated with increased risk in cancer, cardiovascular and other common diseases. The cellular level of PLP therefore needs to be tightly controlled. How this homeostasis is achieved is an important, yet ...

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