• Flotillin-mediated membrane fluidity controls peptidoglycan synthesis and MreB movement.

      Zielińska, Aleksandra; Savietto, Abigail; de Sousa Borges, Anabela; Martinez, Denis; Berbon, Melanie; Roelofsen, Joël R; Hartman, Alwin M; de Boer, Rinse; Van der Klei, Ida J; Hirsch, Anna Kh; et al. (eLife Sciences Publications, Ltd., 2020-07-14)
      Every living cell is enclosed by a flexible membrane made of molecules known as phospholipids, which protects the cell from harmful chemicals and other threats. In bacteria and some other organisms, a rigid structure known as the cell wall sits just outside of the membrane and determines the cell’s shape. There are several proteins in the membrane of bacteria that allow the cell to grow by assembling new pieces of the cell wall. To ensure these proteins expand the cell wall at the right locations, another protein known as MreB moves and organizes them to the appropriate place in the membrane and controls their activity. Previous studies have found that another class of proteins called flotillins are involved in arranging proteins and phospholipid molecules within membranes. Bacteria lacking these proteins do not grow properly and are unable to maintain their normal shape. However, the precise role of the flotillins remained unclear. Here, Zielińska, Savietto et al. used microscopy approaches to study flotillins in a bacterium known as Bacillus subtilis. The experiments found that, in the presence of flotillins, MreB moved around the membrane more quickly (suggesting it was more active) than when no flotillins were present. Similar results were observed when bacterial cells lacking flotillins were treated with a chemical that made membranes more ‘fluid’ – that is, made it easier for the molecules within the membrane to travel around. Further experiments found that flotillins allowed the phospholipid molecules within an artificial membrane to move around more freely, which increases the fluidity of the membrane. These findings suggest that flotillins make the membranes of bacterial cells more fluid to help cells expand their walls and perform several other processes. Understanding how bacteria control the components of their membranes will further our understanding of how many currently available antibiotics work and may potentially lead to the design of new antibiotics in the future.
    • Fragment-Based Discovery of a Qualified Hit Targeting the Latency-Associated Nuclear Antigen of the Oncogenic Kaposi's Sarcoma-Associated Herpesvirus/Human Herpesvirus 8.

      Kirsch, Philine; Jakob, Valentin; Oberhausen, Kevin; Stein, Saskia C; Cucarro, Ivano; Schulz, Thomas F; Empting, Martin; HIPS, Helmholtz-Institut für Pharmazeutische Forschung Saarland, Universitätscampus E8.1 66123 Saarbrücken, Germany. (American Chemical Society, 2019-04-25)
      The latency-associated nuclear antigen (LANA) is required for latent replication and persistence of Kaposi's sarcoma-associated herpesvirus/human herpesvirus 8. It acts via replicating and tethering the virus episome to the host chromatin and exerts other functions. We conceived a new approach for the discovery of antiviral drugs to inhibit the interaction between LANA and the viral genome. We applied a biophysical screening cascade and identified the first LANA binders from small, structurally diverse compound libraries. Starting from a fragment-sized scaffold, we generated optimized hits via fragment growing using a dedicated fluorescence-polarization-based assay as the structure-activity-relationship driver. We improved compound potency to the double-digit micromolar range. Importantly, we qualified the resulting hit through orthogonal methods employing EMSA, STD-NMR, and MST methodologies. This optimized hit provides an ideal starting point for subsequent hit-to-lead campaigns providing evident target-binding, suitable ligand efficiencies, and favorable physicochemical properties.
    • François Diederich - In Memoriam*.

      Hof, Fraser; Hirsch, Anna K H; HIPS, Helmholtz-Institut für Pharmazeutische Forschung Saarland, Universitätscampus E8.1 66123 Saarbrücken, Germany. (Wiley-VCH, 2020-12-14)
      François Diederich - In Memoriam. In this Guest Editorial, Fraser Hof and Anna K. H. Hirsch help us remember the life and scientific legacy of Prof. François Diederich, a beloved mentor and inspiration to many, as well as an extraordinary scientist who made significant impacts in remarkably diverse areas.
    • From Wood to Tetrahydro-2-benzazepines in Three Waste-Free Steps: Modular Synthesis of Biologically Active Lignin-Derived Scaffolds.

      Elangovan, Saravanakumar; Afanasenko, Anastasiia; Haupenthal, Jörg; Sun, Zhuohua; Liu, Yongzhuang; Hirsch, Anna K H; Barta, Katalin; HIPS, Helmholtz-Institut für Pharmazeutische Forschung Saarland, Universitätscampus E8.1 66123 Saarbrücken, Germany. (American Society for Chemistry, 2019-10-23)
      nherently complex, lignin-derived aromatic monomers comprising valuable structural moieties present in many pharmaceuticals would serve as ideal substrates for the construction of biologically active molecules. Here, we describe a strategy that incorporates all intrinsic functional groups present in platform chemicals obtained by lignin depolymerization into value-added amines, using sustainable catalytic methods and benign solvents. Our strikingly efficient protocol provides access to libraries of aminoalkyl-phenol derivatives and seven-membered N-heterocycles directly from wood in two, respectively three, waste-free steps. Several molecules in these libraries have shown promising antibacterial or anticancer activities, emphasizing the advantage of this modular synthetic strategy and the potential for drug discovery. The sustainable catalytic pathways presented here can lead to significant benefits for the pharmaceutical industry where reduction of hazardous waste is a prime concern, and the described strategies that lead to high-value products from non-edible biomass waste streams also markedly increase the economic feasibility of lignocellulosic biorefineries.
    • Heteroatom insertion into 3,4-dihydro-1H-quinolin-2-ones leads to potent and selective inhibitors of human and rat aldosterone synthase.

      Grombein, Cornelia M; Hu, Qingzhong; Rau, Sabrina; Zimmer, Christina; Hartmann, Rolf W; Helmholtz Institute for Pharmaceutical Research Saarland (HIPS) Campus C2 3, D-66123 Saarbrücken, Germany. (2015-01-27)
      Aldosterone synthase (CYP11B2) catalyzes the conversion of 11-deoxycorticosterone to aldosterone via corticosterone and 18-hydroxycorticosterone. CYP11B2 is regarded as a new target for several cardiovascular diseases which are associated with chronically elevated aldosterone levels such as hypertension, congestive heart failure and myocardial fibrosis. In this paper, we optimized heterocycle substituted 3,4-dihydropyridin-2(1H)-ones as CYP11B inhibitors by systematic introduction of heteroatoms and by bioisosteric exchange of the lactame moiety by a sultame moiety. The most promising compounds regarding inhibition of human CYP11B2 and selectivity versus human enzymes CYP11B1, CYP17, and CYP19 were tested for inhibition of rat CYP11B2. Thus, we discovered compounds 4 and 9 which show potent inhibition of hCYP11B2 (IC50 < 1 nM) and the corresponding rat enzyme (4: 64%, 9: 51% inhibition, at 2 μM).
    • Hit evaluation of an α-helical peptide: Ala-scan, truncation and sidechain-to-sidechain macrocyclization of an RNA polymerase Inhibitor.

      Kamal, Ahmed Ashraf Moustafa; Habib, Monica; Haupenthal, Joerg; Hartmann, Rolf Wolfgang; Empting, Martin; HIPS, Helmholtz-Institut für Pharmazeutische Forschung Saarland, Universitätscampus E8.1 66123 Saarbrücken, Germany. (De Gruyter, 2019-02-25)
      RNA polymerase (RNAP) remains a relatively underexplored target with only rifampicin and fidaxomicin in clinical use. Hence, the concurrent rise in bacterial resistance rate urges the search for novel RNAP inhibitors with novel mode of action. In this work, we investigated the impact of several systematic modifications including sidechain-to-sidechain macrocylization in α-helical content and biological activity of a previously identified inhibitory sigma factor fragment. Ala-scan results, peptide truncation from both the N- and C- terminus, and modifications inspired by other RNAP inhibitors revealed novel structure activity relationships but did not yield a superior sequence. Additionally, four insertion points for non-natural amino acids bearing side chains required for macrocylization were explored. Linear precursors showed improved stabilization of α-helical content compared to the original sequence as demonstrated by CD spectroscopy. However, this increase in α-helicity did not translate into improved biological activity. Instead, complete abolishment of RNAP inhibitory activity occurred. We hypothesize three possible reasons for such discrepancy and offer basis for further optimization efforts for this peptidic RNAP inhibitor.
    • Hit-optimization using target-directed dynamic combinatorial chemistry: development of inhibitors of the anti-infective target 1-deoxy-d-xylulose-5-phosphate synthase.

      Jumde, Ravindra P; Guardigni, Melissa; Gierse, Robin M; Alhayek, Alaa; Zhu, Di; Hamid, Zhoor; Johannsen, Sandra; Elgaher, Walid A M; Neusens, Philipp J; Nehls, Christian; et al. (Royal Society of Chemistry, 2021-04-28)
      Target-directed dynamic combinatorial chemistry (tdDCC) enables identification, as well as optimization of ligands for un(der)explored targets such as the anti-infective target 1-deoxy-d-xylulose-5-phosphate synthase (DXPS). We report the use of tdDCC to first identify and subsequently optimize binders/inhibitors of the anti-infective target DXPS. The initial hits were also optimized for their antibacterial activity against E. coli and M. tuberculosis during subsequent tdDCC runs. Using tdDCC, we were able to generate acylhydrazone-based inhibitors of DXPS. The tailored tdDCC runs also provided insights into the structure-activity relationship of this novel class of DXPS inhibitors. The competition tdDCC runs provided important information about the mode of inhibition of acylhydrazone-based inhibitors. This approach holds the potential to expedite the drug-discovery process and should be applicable to a range of biological targets.
    • Hit-to-lead optimization of a latency-associated nuclear antigen inhibitor against Kaposi's sarcoma-associated herpesvirus infections.

      Kirsch, Philine; Stein, Saskia C; Berwanger, Aylin; Rinkes, Julia; Jakob, Valentin; Schulz, Thomas F; Empting, Martin; HIPS, Helmholtz-Institut für Pharmazeutische Forschung Saarland, Universitätscampus E8.1 66123 Saarbrücken, Germany. (Elsevier, 2020-06-28)
      The Latency-associated nuclear antigen (LANA) plays a central role for the latent persistence of the Kaposi's Sarcoma Herpesvirus (KSHV) in the human host and helps to establish lifelong infections. Herein, we report our efforts towards hit-to-lead generation starting from a previously discovered LANA-DNA inhibitor. By tethering the viral genome to the host nucleosomes, LANA ensures the segregation and persistence of the viral DNA during mitosis. LANA is also required for the replication of the latent viral episome during the S phase of the cell cycle. We aim to inhibit the interaction between LANA and the viral genome to prevent the latent persistence of KSHV in the host organism. Medicinal chemistry-driven optimization studies and structure-activity-relationship investigation led to the discovery of an improved LANA inhibitor. The functional activity of our compounds was evaluated using a fluorescence polarization (FP)-based interaction inhibition assay and electrophoretic mobility shift assay (EMSA). Even though a crystal structure of the ligand protein complex was not available, we successfully conducted hit optimization toward a low micromolar protein-nucleic acid-interaction inhibitor. Additionally, we applied STD-NMR studies to corroborate target binding and to gain insights into the binding orientation of our most potent inhibitor, providing opportunities for further rational design of more efficient LANA-targeting anti KSHV agents in future studies.
    • Hits identified in library screening demonstrate selective CYP17A1 lyase inhibition.

      Krug, Sebastian J; Hu, Qingzhong; Hartmann, Rolf W; Pharmaceutical and Medicinal Chemistry, Saarland University, Campus C2.3, 66123 Saarbrücken, Germany. (2013-03)
      A screening of structurally different steroid hormone synthesis inhibitors was performed in order to find a starting point for the development of a new inhibitor of the bifunctional steroidogenic enzyme CYP17A1. Emphasis was placed on determination of selectivity between the two catalytic steps, namely 17α-hydroxylase and C(17,20)-lyase. For that purpose a new inhibition assay has been developed. Hits identified within this novel assay demonstrated selective inhibition of CYP17A1 lyase activity, and thus mark the basis for the development of selective C(17,20)-lyase inhibitors for the treatment of prostate cancer.
    • Hydroxybenzothiazoles as new nonsteroidal inhibitors of 17β-hydroxysteroid dehydrogenase type 1 (17β-HSD1).

      Spadaro, Alessandro; Negri, Matthias; Marchais-Oberwinkler, Sandrine; Bey, Emmanuel; Frotscher, Martin; Pharmaceutical and Medicinal Chemistry, Saarland University, Saarbrücken, Germany. (2012)
      17β-estradiol (E2), the most potent estrogen in humans, known to be involved in the development and progession of estrogen-dependent diseases (EDD) like breast cancer and endometriosis. 17β-HSD1, which catalyses the reduction of the weak estrogen estrone (E1) to E2, is often overexpressed in breast cancer and endometriotic tissues. An inhibition of 17β-HSD1 could selectively reduce the local E2-level thus allowing for a novel, targeted approach in the treatment of EDD. Continuing our search for new nonsteroidal 17β-HSD1 inhibitors, a novel pharmacophore model was derived from crystallographic data and used for the virtual screening of a small library of compounds. Subsequent experimental verification of the virtual hits led to the identification of the moderately active compound 5. Rigidification and further structure modifications resulted in the discovery of a novel class of 17β-HSD1 inhibitors bearing a benzothiazole-scaffold linked to a phenyl ring via keto- or amide-bridge. Their putative binding modes were investigated by correlating their biological data with features of the pharmacophore model. The most active keto-derivative 6 shows IC₅₀-values in the nanomolar range for the transformation of E1 to E2 by 17β-HSD1, reasonable selectivity against 17β-HSD2 but pronounced affinity to the estrogen receptors (ERs). On the other hand, the best amide-derivative 21 shows only medium 17β-HSD1 inhibitory activity at the target enzyme as well as fair selectivity against 17β-HSD2 and ERs. The compounds 6 and 21 can be regarded as first benzothiazole-type 17β-HSD1 inhibitors for the development of potential therapeutics.
    • Identification of 4-(4-nitro-2-phenethoxyphenyl)pyridine as a promising new lead for discovering inhibitors of both human and rat 11β-Hydroxylase.

      Hu, Qingzhong; Kunde, Jessica; Hanke, Nina; Hartmann, Rolf W; Pharmaceutical and Medicinal Chemistry, Saarland University, Campus C2.3, D-66123 Saarbrücken, Germany. (2015-05-26)
      The inhibition of 11β-hydroxylase is a promising strategy for the treatment of Cushing's syndrome, in particular for the recurrent and subclinical cases. To achieve proof of concept in rats, efforts were paid to identify novel lead compounds inhibiting both human and rat CYP11B1. Modifications on a potent promiscuous inhibitor of hCYP11B1, hCYP11B2 and hCYP19 (compound IV) that exhibited moderate rCYP11B1 inhibition led to compound 8 as a new promising lead compound. Significant improvements compared to starting point IV were achieved regarding inhibitory potency against both human and rat CYP11B1 (IC50 values of 2 and 163 nM, respectively) as well as selectivity over hCYP19 (IC50 = 1900 nM). Accordingly, compound 8 was around 7- and 28-fold more potent than metyrapone regarding the inhibition of human and rat CYP11B1 and exhibited a comparable selectivity over hCYP11B2 (SF of 3.5 vs 4.9). With further optimizations on this new lead compound 8, drug candidates with satisfying profiles are expected to be discovered.
    • Identification of a 1-deoxy-D-xylulose-5-phosphate synthase (DXS) mutant with improved crystallographic properties.

      Gierse, Robin M; Reddem, Eswar R; Alhayek, Alaa; Baitinger, Dominik; Hamid, Zhoor; Jakobi, Harald; Laber, Bernd; Lange, Gudrun; Hirsch, Anna K H; Groves, Matthew R; et al. (Elsevier, 2021-01-05)
      In this report, we describe a truncated Deinococcus radiodurans 1-deoxy-D-xylulose-5-phosphate synthase (DXS) protein that retains enzymatic activity, while slowing protein degradation and showing improved crystallization properties. With modern drug-design approaches relying heavily on the elucidation of atomic interactions of potential new drugs with their targets, the need for co-crystal structures with the compounds of interest is high. DXS itself is a promising drug target, as it catalyzes the first reaction in the 2-C-methyl-D-erythritol 4-phosphate (MEP)-pathway for the biosynthesis of the universal precursors of terpenes, which are essential secondary metabolites. In contrast to many bacteria and pathogens, which employ the MEP pathway, mammals use the distinct mevalonate-pathway for the biosynthesis of these precursors, which makes all enzymes of the MEP-pathway potential new targets for the development of anti-infectives. However, crystallization of DXS has proven to be challenging: while the first X-ray structures from Escherichia coli and D. radiodurans were solved in 2004, since then only two additions have been made in 2019 that were obtained under anoxic conditions. The presented site of truncation can potentially also be transferred to other homologues, opening up the possibility for the determination of crystal structures from pathogenic species, which until now could not be crystallized. This manuscript also provides a further example that truncation of a variable region of a protein can lead to improved structural data.
    • The IGF2 mRNA binding protein p62/IGF2BP2-2 induces fatty acid elongation as a critical feature of steatosis.

      Laggai, Stephan; Kessler, Sonja M; Boettcher, Stefan; Lebrun, Valérie; Gemperlein, Katja; Lederer, Eva; Leclercq, Isabelle A; Mueller, Rolf; Hartmann, Rolf W; Haybaeck, Johannes; et al. (2014-04-22)
      Liver-specific overexpression of the insulin-like growth factor 2 (IGF2) mRNA binding protein p62/IGF2BP2-2 induces a fatty liver, which highly expresses IGF2. Because IGF2 expression is elevated in patients with steatohepatitis, the aim of our study was to elucidate the role and interconnection of p62 and IGF2 in lipid metabolism. Expression of p62 and IGF2 highly correlated in human liver disease. p62 induced an elevated ratio of C18:C16 and increased fatty acid elongase 6 (ELOVL6) protein, the enzyme catalyzing the elongation of C16 to C18 fatty acids and promoting nonalcoholic steatohepatitis in mice and humans. The p62 overexpression induced the activation of the ELOVL6 transcriptional activator sterol regulatory element binding transcription factor 1 (SREBF1). Recombinant IGF2 induced the nuclear translocation of SREBF1 and a neutralizing IGF2 antibody reduced ELOVL6 and mature SREBF1 protein levels. Concordantly, p62 and IGF2 correlated with ELOVL6 in human livers. Decreased palmitoyl-CoA levels, as found in p62 transgenic livers, can explain the lipogenic action of ELOVL6. Accordingly, p62 represents an inducer of hepatic C18 fatty acid production via a SREBF1-dependent induction of ELOVL6. These findings underline the detrimental role of p62 in liver disease.
    • In-depth Profiling of MvfR-Regulated Small Molecules in Pseudomonas aeruginosa after Quorum Sensing Inhibitor Treatment.

      Allegretta, Giuseppe; Maurer, Christine K; Eberhard, Jens; Maura, Damien; Hartmann, Rolf W; Rahme, Laurence; Empting, Martin; Helmholtz-Institute for Pharmaceutical Research Saarland (HIPS),Saarland 9 University, 66123 Saarbrücken, Germany. (2017)
      Pseudomonas aeruginosa is a Gram-negative bacterium, which causes opportunistic infections in immuno-compromised individuals. Due to its multiple resistances toward antibiotics, the development of new drugs is required. Interfering with Quorum Sensing (QS), a cell-to-cell communication system, has shown to be highly efficient in reducing P. aeruginosa pathogenicity. One of its QS systems employs Pseudomonas Quinolone Signal (PQS) and 4-hydroxy-2-heptylquinoline (HHQ) as signal molecules. Both activate the transcriptional regulator MvfR (Multiple Virulence Factor Regulator), also called PqsR, driving the production of QS molecules as well as toxins and biofilm formation. The aim of this work was to elucidate the effects of QS inhibitors (QSIs), such as MvfR antagonists and PqsBC inhibitors, on the biosynthesis of the MvfR-regulated small molecules 2'-aminoacetophenone (2-AA), dihydroxyquinoline (DHQ), HHQ, PQS, and 4-hydroxy-2-heptylquinoline-N-oxide (HQNO). The employed synthetic MvfR antagonist fully inhibited pqs small molecule formation showing expected sigmoidal dose-response curves for 2-AA, HQNO, HHQ and PQS. Surprisingly, DHQ levels were enhanced at lower antagonist concentrations followed by a full suppression at higher QSI amounts. This particular bi-phasic profile hinted at the accumulation of a biosynthetic intermediate resulting in the observed overproduction of the shunt product DHQ. Additionally, investigations on PqsBC inhibitors showed a reduction of MvfR natural ligands, while increased 2-AA, DHQ and HQNO levels compared to the untreated cells were detected. Moreover, PqsBC inhibitors did not show any significant effect in PA14 pqsC mutant demonstrating their target selectivity. As 2-AA is important for antibacterial tolerance, the QSIs were evaluated in their capability to attenuate persistence. Indeed, persister cells were reduced along with 2-AA inhibition resulting from MvfR antagonism, but not from PqsBC inhibition. In conclusion, antagonizing MvfR using a dosage capable of fully suppressing this QS system will lead to a favorable therapeutic outcome as DHQ overproduction is avoided and bacterial persistence is reduced.
    • Inhibition of 17β-HSD1: SAR of bicyclic substituted hydroxyphenylmethanones and discovery of new potent inhibitors with thioether linker.

      Abdelsamie, Ahmed S; Bey, Emmanuel; Hanke, Nina; Empting, Martin; Hartmann, Rolf W; Frotscher, Martin (2014-07-23)
      Estradiol is the most potent estrogen in humans. It is known to be involved in the development and proliferation of estrogen dependent diseases such as breast cancer and endometriosis. The last step of its biosynthesis is catalyzed by 17β-hydroxysteroid dehydrogenase type 1 (17β- HSD1) which consequently is a promising target for the treatment of these diseases. Recently, we reported on bicyclic substituted hydroxyphenylmethanones as potent inhibitors of 17β-HSD1. The present study focuses on rational structural modifications in this compound class with the aim of gaining more insight into its structure-activity relationship (SAR). (4-Hydroxyphenyl)-(5-(3-hydroxyphenylsulfanyl)-thiophen-2-yl)methanone (25) was discovered as a member of a novel potent class of human 17β-HSD1 inhibitors. Computational methods were used to elucidate its interactions with the target protein. The compound showed activity also towards the murine 17β-HSD1 enzyme and thus is a starting point for the design of compounds suitable for evaluation in an animal disease model.
    • Inhibition of aldosterone synthase (CYP11B2) by torasemide prevents atrial fibrosis and atrial fibrillation in mice.

      Adam, Oliver; Zimmer, Christina; Hanke, Nina; Hartmann, Rolf W; Klemmer, Birgit; Böhm, Michael; Laufs, Ulrich; Helmholtz Institute for Pharmaceutical Research Saarland (HIPS);Saarland University, Building A4.1, 66123 Saarbruecken, Germany. (2015-08)
      Loop diuretics are used for fluid control in patients with heart failure. Furosemide and torasemide may exert differential effects on myocardial fibrosis. Here, we studied the effects of torasemide and furosemide on atrial fibrosis and remodeling during atrial fibrillation. In primary neonatal cardiac fibroblasts, torasemide (50μM, 24h) but not furosemide (50μM, 24h) reduced the expression of connective tissue growth factor (CTGF; 65±6%) and the pro-fibrotic miR-21 (44±23%), as well as the expression of lysyl oxidase (LOX; 57±8%), a regulator of collagen crosslinking. Mineralocorticoid receptor (MR) expression and activity were not altered. Torasemide but not furosemide inhibited human aldosterone synthase (CYP11B2) activity in transfected lung fibroblasts (V79MZ cells) by 75±1.8%. The selective CYP11B2 inhibitor SL242 mimicked the torasemide effects. Mice with cardiac overexpression of Rac1 GTPase (RacET), which develop atrial fibrosis and spontaneous AF with aging, were treated long-term (8months) with torasemide (10mg/kg/day), furosemide (40mg/kg/day) or vehicle. Treatment with torasemide but not furosemide prevented atrial fibrosis in RacET as well as the up-regulation of CTGF, LOX, and miR-2, whereas MR expression and activity remained unaffected. These effects correlated with a reduced prevalence of atrial fibrillation (33% RacET+Tora vs. 80% RacET). Torasemide but not furosemide inhibits CYP11B2 activity and reduces the expression of CTGF, LOX, and miR-21. These effects are associated with prevention of atrial fibrosis and a reduced prevalence of atrial fibrillation in mice.
    • Inhibitors of 17β-hydroxysteroid dehydrogenase type 1, 2 and 14: Structures, biological activities and future challenges.

      Salah, Mohamed; Abdelsamie, Ahmed S; Frotscher, Martin; HIPS, Helmholtz-Institut füt Pharmazeutische Forschung Saarland, Universitätscampus E8.1 66123 Saarbrücken, Germany. (2018-10-15)
      During the past 25 years, the modulation of estrogen action by inhibition of 17β-hydroxysteroid dehydrogenase types 1 and 2 (17β-HSD1 and 17β-HSD2), respectively, has been pursued intensively. In the search for novel treatment options for estrogen-dependent diseases (EDD) and in order to explore estrogenic signaling pathways, a large number of steroidal and nonsteroidal inhibitors of these enzymes has been described in the literature. The present review gives a survey on the development of inhibitor classes as well as the structural formulas and biological properties of their most interesting representatives. In addition, rationally designed dual inhibitors of both 17β-HSD1 and steroid sulfatase (STS) as well as the first inhibitors of 17β-HSD14 are covered.
    • Interfering with Bacterial Quorum Sensing.

      Reuter, Kerstin; Steinbach, Anke; Helms, Volkhard; Helmholtz Institute for Pharmaceutical Research Saarland (HIPS);Saarland University, Building A4.1, 66123 Saarbruecken, Germany. (2016)
      Quorum sensing (QS) describes the exchange of chemical signals in bacterial populations to adjust the bacterial phenotypes according to the density of bacterial cells. This serves to express phenotypes that are advantageous for the group and ensure bacterial survival. To do so, bacterial cells synthesize autoinducer (AI) molecules, release them to the environment, and take them up. Thereby, the AI concentration reflects the cell density. When the AI concentration exceeds a critical threshold in the cells, the AI may activate the expression of virulence-associated genes or of luminescent proteins. It has been argued that targeting the QS system puts less selective pressure on these pathogens and should avoid the development of resistant bacteria. Therefore, the molecular components of QS systems have been suggested as promising targets for developing new anti-infective compounds. Here, we review the QS systems of selected gram-negative and gram-positive bacteria, namely, Vibrio fischeri, Pseudomonas aeruginosa, and Staphylococcus aureus, and discuss various antivirulence strategies based on blocking different components of the QS machinery.
    • The interferon-stimulated gene product oligoadenylate synthetase-like protein enhances replication of Kaposi's sarcoma-associated herpesvirus (KSHV) and interacts with the KSHV ORF20 protein.

      Bussey, Kendra A; Lau, Ulrike; Schumann, Sophie; Gallo, Antonio; Osbelt, Lisa; Stempel, Markus; Arnold, Christine; Wissing, Josef; Gad, Hans Henrik; Hartmann, Rune; et al. (2018-03)
      Kaposi's sarcoma-associated herpesvirus (KSHV) is one of the few oncogenic human viruses known to date. Its large genome encodes more than 85 proteins and includes both unique viral proteins as well as proteins conserved amongst herpesviruses. KSHV ORF20 is a member of the herpesviral core UL24 family, but the function of ORF20 and its role in the viral life cycle is not well understood. ORF20 encodes three largely uncharacterized isoforms, which we found were localized predominantly in the nuclei and nucleoli. Quantitative affinity purification coupled to mass spectrometry (q-AP-MS) identified numerous specific interacting partners of ORF20, including ribosomal proteins and the interferon-stimulated gene product (ISG) oligoadenylate synthetase-like protein (OASL). Both endogenous and transiently transfected OASL co-immunoprecipitated with ORF20, and this interaction was conserved among all ORF20 isoforms and multiple ORF20 homologs of the UL24 family in other herpesviruses. Characterization of OASL interacting partners by q-AP-MS identified a very similar interactome to that of ORF20. Both ORF20 and OASL copurified with 40S and 60S ribosomal subunits, and when they were co-expressed, they associated with polysomes. Although ORF20 did not have a global effect on translation, ORF20 enhanced RIG-I induced expression of endogenous OASL in an IRF3-dependent but IFNAR-independent manner. OASL has been characterized as an ISG with antiviral activity against some viruses, but its role for gammaherpesviruses was unknown. We show that OASL and ORF20 mRNA expression were induced early after reactivation of latently infected HuARLT-rKSHV.219 cells. Intriguingly, we found that OASL enhanced infection of KSHV. During infection with a KSHV ORF20stop mutant, however, OASL-dependent enhancement of infectivity was lost. Our data have characterized the interaction of ORF20 with OASL and suggest ORF20 usurps the function of OASL to benefit KSHV infection.
    • Inverting Small Molecule-Protein Recognition by the Fluorine Gauche Effect: Selectivity Regulated by Multiple H→F Bioisosterism.

      Bentler, Patrick; Bergander, Klaus; Daniliuc, Constantin G; Mück-Lichtenfeld, Christian; Jumde, Ravindra P; Hirsch, Anna K H; Gilmour, Ryan; HIPS, Helmholtz-Institut für Pharmazeutische Forschung Saarland, Universitätscampus E8.1 66123 Saarbrücken, Germany (Wiley-VCH, 2019-08-05)
      Fluorinated motifs have a venerable history in drug discovery, but as C(sp3 )-F-rich 3D scaffolds appear with increasing frequency, the effect of multiple bioisosteric changes on molecular recognition requires elucidation. Herein we demonstrate that installation of a 1,3,5-stereotriad, in the substrate for a commonly used lipase from Pseudomonas fluorescens does not inhibit recognition, but inverts stereoselectivity. This provides facile access to optically active, stereochemically well-defined organofluorine compounds (up to 98 % ee). Whilst orthogonal recognition is observed with fluorine, the trend does not hold for the corresponding chlorinated substrates or mixed halogens. This phenomenon can be placed on a structural basis by considering the stereoelectronic gauche effect inherent to F-C-C-X systems (σ→σ*). Docking reveals that this change in selectivity (H versus F) with a common lipase results from inversion in the orientation of the bound substrate being processed as a consequence of conformation. This contrasts with the stereochemical interpretation of the biogenetic isoprene rule, whereby product divergence from a common starting material is also a consequence of conformation, albeit enforced by two discrete enzymes.