Raphaël Terreux

Delayed hypersensitivity to corticosteroids in a series of 315 patients: clinical data and patch test results

Background: Corticosteroids may cause immediate or delayed hypersensitivity. In 1989, based on structural and clinical characteristics, we put forward a classification of corticosteroids into four cross‐reacting groups, namely group A, B, C, and D, the latter later subdivided into two subgroups, i.e. D1 and D2. The constituents on the D‐ring of the corticosteroid‐molecule are considered to have a central role for binding to skin proteins and for cross‐reactions patterns; however, halogenation of the molecules is also interfering.

Substituted chromones as highly potent nontoxic inhibitors, specific for the breast cancer resistance protein.

A series of 13 disubstituted chromones was synthesized. Two types of substituents, on each side of the scaffold, contributed to both the potency of ABCG2 inhibition and the cytotoxicity. The best compound, 5-(4-bromobenzyloxy)-2-(2-(5-methoxyindolyl)ethyl-1-carbonyl)-4H-chromen-4-one (6g), displayed high-affinity inhibition and low cytotoxicity, giving a markedly high therapeutic index. The chromone derivative specifically inhibited ABCG2 versus other multidrug ABC transporters and was not transported. It constitutes a highly promising candidate for in vivo chemosensitization of ABCG2-expressing tumors.

Identification of structural and molecular determinants of the tyrosine-kinase Wzc and implications in capsular polysaccharide export

Capsular polysaccharides are well‐established virulence factors of pathogenic bacteria. Their biosynthesis and export are regulated within the transmembrane polysaccharide assembly machinery by the autophosphorylation of atypical tyrosine‐kinases, named BY‐kinases. However, the accurate functioning of these tyrosine‐kinases remains unknown. Here, we report the crystal structure of the non‐phosphorylated cytoplasmic domain of the tyrosine‐kinase Wzc from Escherichia coli in complex with ADP showing that it forms a ring‐shaped octamer. Mutational analysis demonstrates that a conserved EX2RX2R motif involved in subunit interactions is essential for polysaccharide export. We also elucidate the role of a putative internal regulatory tyrosine and we show that BY‐kinases from proteobacteria autophosphorylate on their C‐terminal tyrosine cluster via a single‐step intermolecular mechanism. This structure‐function analysis also allows us to demonstrate that two different parts of a conserved basic region called the RK‐cluster are essential for polysaccharide export and for kinase activity respectively. Based on these data, we revisit the dichotomy made between BY‐kinases from proteobacteria and firmicutes and we propose a unique process of oligomerization and phosphorylation. We also reassess the function of BY‐kinases in the capsular polysaccharide assembly machinery.

Corticosteroid cross‐reactivity: clinical and molecular modelling tools

To cite this article: Baeck M., Chemelle J.A., Goossens A., Nicolas J.F., Terreux R. Corticosteroid cross‐reactivity: clinical and molecular modelling tools. Allergy 2011; 66: 1367–1374.

Bacterial tyrosine-kinases: Structure–function analysis and therapeutic potential

Since the characterization of genes encoding Ser/Thr-kinases and Tyr-kinases in bacteria, in 1991 and 1997, respectively, a growing body of evidence has been reported showing the important role of these enzymes in the regulation of bacterial physiology. While most Ser/Thr-kinases share structural similarity with their eukaryotic counterparts, it seems that bacteria have developed their own Tyr-kinases to catalyze protein phosphorylation on tyrosine. Different types of Tyr-kinases have been identified in bacteria and a large number of them are similar to ATP-binding proteins with Walker motifs. These enzymes have been grouped in the same family (BY-kinases) and the crystal structures of two of them have been recently characterized. Phosphoproteome analysis suggest that BY-kinases are involved in several cellular processes and to date, the best-characterized role of BY-kinases concerns the control of extracellular polysaccharide synthesis. Knowing the role of these compounds in the virulence of bacterial pathogens, BY-kinases can be considered as promising targets to combat some diseases. Here, we review the current knowledge on BY-kinases and discuss their potential for the development of new antibiotics.

Multidrug Resistance ABC Transporter Structure Predictions by Homology Modeling Approaches

Human multidrug resistance ABC transporters are ubiquitous membrane proteins responsible for the efflux of multiple, endogenous or exogenous, compounds out of the cells, and therefore they are involved in multi-drug resistance phenotype (MDR). They thus deeply impact the pharmacokinetic parameters and toxicity properties of drugs. A great pressure to develop inhibitors of these pumps is carried out, by either ligand-based drug design or (more ideally) structure-based drug design. In that goal, many biochemical studies have been carried out to characterize their transport functions, and many efforts have been spent to get high-resolution structures. Currently, beside the 3D-structures of bacterial ABC transporters Sav1866 and MsbA, only the mouse ABCB1 complete structure has been published at high-resolution, illustrating the tremendous difficulty in getting such information, taking into account that the human genome accounts for 48 ABC transporters encoding genes. Homology modeling is consequently a reasonable approach to overcome this obstacle. The present review describes, in the first part, the different approaches which have been published to set up human ABC pump 3D-homology models allowing the localization of binding sites for drug candidates, and the identification of critical residues therein. In a second part, the review proposes a more accurate strategy and practical keys to use such biological tools for initiating structure-based drug design.

6‐Halogenochromones Bearing Tryptamine: One‐Step Access to Potent and Highly Selective Inhibitors of Breast Cancer Resistance Protein

Most anticancer drugs are rendered less efficacious due to cell resistance to chemotherapy related to various mechanisms. A major mechanism is associated with the overexpression of ATP binding cassette (ABC) transporters, especially P-glycoprotein (Pgp/ABCB1), multidrug resistance-associated protein 1 (MRP1/ ABCC1) and breast cancer resistance protein (BCRP/ABCG2), which traffic chemotherapeutic agents out of cancer cells. ABCG2 was simultaneously discovered by three research groups and named ABCP for its abundance in placenta, BCRP for its identification in breast cancer cell lines, and MXR for its resistance to mitoxantrone. ABCG2 constitutes an important target for the design of efflux inhibitors that would, when co-administered with an anticancer agent, give increased intracellular drug concentrations and hence greater cytotoxicity. While several types of ABCG2 inhibitors have been evaluated in vitro, very few have entered preclinical trials. We recently discovered that some substituted chromones are selective and potent ABCG2 inhibitors. These compounds were synthesized in five steps, and the overall yields were quite low. In pursuing our efforts toward structurally simple and easily accessible specific inhibitors of BCRP, we investigated 6-halogenochromones linked to a tryptamine unit, obtained in only one step, as new potent inhibitors (Scheme 1). The choice of C-6 as the site of halogenation was motivated by a number of considerations: 1) the presence of a hydrophobic halogen at the C-6 position fulfills the previously identified need for a hydrophobic substituent in this part of the molecule; 2) halogens, especially bromine and iodine, have a positive contribution to inhibitory activity ; 3) halogens could open interesting opportunities for the generation of further potential inhibitors, as they can be easily replaced by a number of chemical entities. Access to target compounds 3–7 was achieved in one step by coupling 6-substituted-4-oxo-4H-chromene-2-carboxylic acid (1) with tryptamine (2) in the presence of bis(2-oxo-3-oxazolidinyl)phosphonic chloride (BOP-Cl) as the coupling agent (Scheme 2; full details are given in the Supporting Information). 6-Iodo-4-oxo-4H-chromene-2-carboxylic acid (R= I) was not commercially available, but was easily obtained by hydrolysis of the commercially available corresponding ethyl ester with sodium hydrogen carbonate (20% in water) at 80 8C. The test compounds were first screened by flow cytometry for their effects on the inhibition of mitoxantrone efflux in Scheme 1. Retrosynthetic rationale for the synthesis of targeted BCRP inhibitors, and the structures of the commercially available starting materials 1 and 2.

Interhelical loops within the bHLH domain are determinant in maintaining TWIST1–DNA complexes

The basic helix-loop-helix (bHLH) transcription factor TWIST1 is essential to embryonic development, and hijacking of its function contributes to the development of numerous cancer types. It forms either a homodimer or a heterodimeric complex with an E2A or HAND partner. These functionally distinct complexes display sometimes antagonistic functions during development, so that alterations in the balance between them lead to pronounced morphological alterations, as observed in mice and in Saethre–Chotzen syndrome patients. We, here, describe the structures of TWIST1 bHLH–DNA complexes produced in silico through molecular dynamics simulations. We highlight the determinant role of the interhelical loops in maintaining the TWIST1–DNA complex structures and provide a structural explanation for the loss of function associated with several TWIST1 mutations/insertions observed in Saethre–Chotzen syndrome patients. An animated interactive 3D complement (I3DC) is available in Proteopedia at http://proteopedia.org/w/Journal:JBSD:27

Candidate Molecule Selection Based on In Silico Predicted ADMET Properties of 12 Indenoindole Derivatives

For considering future in vivo assays, it is necessary to investigate pharmacokinetic and toxicity profile of new chemical entities to select the best candidate(s) for further evaluations. Physicochemical parameters and ADMET (Absorption, Distribution, Metabolism, Elimination and Toxicity) properties of 12 indenoindole derivatives – identified as potent inhibitors of the ABCG2 protein - were predicted in silico with the Molinspiration and the ACD/Percepta softwares. The evaluation of mutagenicity and carcinogenicity was achieved by using the QSAR Toolbox software. Based on the exercise, i) two phenolic derivatives should not be metabolically activated by CYP enzymes according to the QSAR Toolbox software leading to a lower mutagenic risk, ii) compounds 2b, 2c could be excluded from further studies because of clastogenic risks and again compound 2c for a relatively low oral bioavailability, iii) one compound for its blood toxicity and five because for their pulmonary toxicity. Finally, six out of the 12 derivatives (1a, 1b, 2a, 2d, 2e and 2g), were predicted, in terms of ADMET properties, to be good candidates for further in vivo investigations.

SuMo: A Tool for Protein Function Inference Based on 3D Structures Comparisons

The prediction of important residues for binding/recognition sites in protein 3D structures is still a matter of challenge. Indeed, binding sites recognition is generally based on geometry often combined with physico-chemical properties of the site since the conformation, size and chemical composition of the protein surface are all relevant for the interaction with a specific ligand. In our group, we designed an innovative bioinformatics method called SuMo in order to detect similar 3-dimensional (3D) sites in proteins (Jambon et al. Protein-Struct Funct Genet 52:137–145, 2003). This approach allowed the comparison of protein structures or substructures, and detected local spatial similarities: the main advantage of the method is its independence for both amino acid sequences and backbone structures. In contrast to already existing tools, the basis for this method is a representation of the protein structure by a set of stereo chemical groups that are defined independently from the notion of amino acid. An efficient heuristics for finding similarities has been developed which uses graphs of triangles of chemical groups to represent the protein structures. The SuMo (Surfing the Molecules) program allows the dynamic definition of chemical groups, the selection of sites in the proteins, and the management and screening of databases. The basic principle of SuMo has been used in several recent studies (Sperandio et al. J Cheml Inf Model 47:1097–1110, 2007) (Doppelt-Azeroual et al. Protein Sci 19:847–867, 2010). In order to give access to the SuMo tool, we proposed a web server (Jambon et al. Bioinformatics 21:3929–3930, 2005) reachable at http://sumo-pbil.ibcp.fr. This chapter will describe the main rationale we initially took for designing the first release of SuMo. In addition, we propose a completely new set of parameters best suitable for proteins and finally, we illustrate its power with several biological examples. Two of them dealing with serine proteases and lectins are given for a comparison purpose. The first two examples illustrate the capability of SuMo to deal with completely opposite modes of evolution i.e. convergence and divergence. A new biological application dealing with betalactame binding protein PBB molecules is also presented.