FMP Publications

Our publications are recorded in a searchable database since 2010, updates will be added regularly.

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Small-molecule inhibitors of AF6 PDZ-mediated protein-protein interactions
Vargas, C., Radziwill(*), G., Krause, G., Diehl, A., Keller, S., Kamdem, N., Czekelius(*), C., Kreuchwig, A., Schmieder, P., Doyle(*), D., Moelling(*), K., Hagen, V., Schade(*), M.; Oschkinat, H.
Chemmedchem, 9:1458-1462

Tags: NMR-Supported Structural Biology (Oschkinat), Solution NMR (Schmieder), Synthetic Organic Biochemistry (Hagen), Structural Bioinformatics and Protein Design (Krause, G.), Biophysics of Membrane Proteins (Keller), Synthetic Organic Biochemistry (Hagen)

Abstract: PDZ (PSD-95, Dlg, ZO-1) domains are ubiquitous interaction modules that are involved in many cellular signal transduction pathways. Interference with PDZ-mediated protein-protein interactions has important implications in disease-related signaling processes. For this reason, PDZ domains have gained attention as potential targets for inhibitor design and, in the long run, drug development. Herein we report the development of small molecules to probe the function of the PDZ domain from human AF6 (ALL1-fused gene from chromosome 6), which is an essential component of cell-cell junctions. These compounds bind to AF6 PDZ with substantially higher affinity than the peptide (Ile-Gln-Ser-Val-Glu-Val) derived from its natural ligand, EphB2. In intact cells, the compounds inhibit the AF6-Bcr interaction and interfere with epidermal growth factor (EGF)-dependent signaling.

Stereoselective Synthesis of Tricyclic Diproline Analogues that Mimic a PPII Helix: Structural Consequences of Ring-Size Variation
Soicke(*), A., Reuter(*), C., Winter(*), M., Neudörfl(*), J. M., Schlorer(*), N., Kühne, R.; Schmalz(*), H. G.
Eur J Org Chem, :6467-6480

Tags: Computational Chemistry and Protein Design (Kühne)

Abstract: Polycyclic proline-derived scaffolds (ProMs) have recently demonstrated their value as conformationally defined dipeptide analogs for the modular construction of secondary structure mimetics, specifically interfering with PPII helix-mediated protein-protein interactions. We disclose the stereoselective synthesis of two new tricyclic amino acid scaffolds (ProM-4 and ProM-8) that differ from the first generation scaffold ProM-1 by the size of ring A. Conformational preferences and subtle structural differences of the three homologous scaffolds were analyzed by X-ray crystallography, computational calculations, and NMR spectroscopy. N-tert-butoxycarbonyl(Boc)-3-(1-propenyl) azetidine-2-carboxylic acid was prepared from L-aspartic acid through beta-lactam intermediates. The corresponding piperidine-based building block rac-N-Boc-3-vinylpipecolic acid was synthesized by Cu-catalyzed 1,4-addition of vinyl-MgBr to methyl N-Boc-2,3-dehydropipecolate. Target molecules were prepared through peptide coupling of the respective ring A building blocks with cis-5-vinylproline tert-butyl ester and subsequent ring-closing metathesis. Selective deprotection of a tert-butyl carbamate (N-Boc protecting group) in the presence of a tert-butyl ester was achieved with trifluoroacetic acid at 0 degrees C.

Stereoselective Synthesis of Proline- Derived Dipeptide Scaffolds ( ProM-3 and ProM-7) Rigidified in a PPII Helix Conformation
Reuter(*), C., Kleczka(*), M., de Mazancourt(*), S., Neudörfl(*), J. M., Kühne, R.; Schmalz(*), H. G.
Eur J Org Chem, 2014:2664-2667

Tags: Computational Chemistry and Protein Design (Kühne)

Abstract: Following a peptide coupling/metathesis-based strategy, the two diastereomeric scaffolds ProM-3 and ProM-7 were stereoselectively synthesized (as 9-fluorenylmethoxycarbonyl derivatives), and their configuration was unambiguously proven by means of X-ray crystallography. The required dehydroisoleucine building blocks were prepared by applying the enantioselective Kazmaier-Claisen rearrangement. The target compounds represent dipeptide analogs rigidified in a PPII helix conformation, which are of interest for the development of new proteomimetics that selectively bind to protein domains specialized in the recognition of ligands adopting a PPII helix secondary structure.

Design of a General-Purpose European Compound Screening Library for EU-OPENSCREEN
Horvath(*), D., Lisurek, M., Rupp, B., Kühne, R., Specker, E., von Kries, J., Rognan(*), D., Andersson(*), C. D., Almqvist(*), F., Elofsson(*), M., Enqvist(*), P. A., Gustavsson(*), A. L., Remez(*), N., Mestres(*), J., Marcou(*), G., Varnek(*), A., Hibert(*), M., Quintana(*), J.; Frank, R.
Chemmedchem, 9:2309-2326

Tags: Chemical Systems Biology (Frank), Screening Unit (von Kries), Computational Chemistry and Protein Design (Kühne)

Abstract: This work describes a collaborative effort to define and apply a protocol for the rational selection of a general-purpose screening library, to be used by the screening platforms affiliated with the EU-OPENSCREEN initiative. It is designed as a standard source of compounds for primary screening against novel biological targets, at the request of research partners. Given the general nature of the potential applications of this compound collection, the focus of the selection strategy lies on ensuring chemical stability, absence of reactive compounds, screening-compliant physicochemical properties, loose compliance to drug-likeness criteria (as drug design is a major, but not exclusive application), and maximal diversity/coverage of chemical space, aimed at providing hits for a wide spectrum of drugable targets. Finally, practical availability/cost issues cannot be avoided. The main goal of this publication is to inform potential future users of this library about its conception, sources, and characteristics. The outline of the selection procedure, notably of the filtering rules designed by a large committee of European medicinal chemists and chemoinformaticians, may be of general methodological interest for the screening/medicinal chemistry community. The selection task of 200K molecules out of a pre-filtered set of 1.4M candidates was shared by five independent European research groups, each picking a subset of 40K compounds according to their own in-house methodology and expertise. An in-depth analysis of chemical space coverage of the library serves not only to characterize the collection, but also to compare the various chemoinformatics-driven selection procedures of maximal diversity sets. Compound selections contributed by various participating groups were mapped onto general-purpose self-organizing maps (SOMs) built on the basis of marketed drugs and bioactive reference molecules. In this way, the occupancy of chemical space by the EU-OPENSCREEN library could be directly compared with distributions of known bioactives of various classes. This mapping highlights the relevance of the selection and shows how the consensus reached by merging the five different 40K selections contributes to achieve this relevance. The approach also allows one to readily identify subsets of target-or target-class-oriented compounds from the EU-OPENSCREEN library to suit the needs of the diverse range of potential users. The final EU-OPENSCREEN library, assembled by merging five independent selections of 40K compounds from various expert groups, represents an excellent example of a Europe-wide collaborative effort toward the common objective of building best-in-class European open screening platforms.

The specific monomer/dimer equilibrium of the corticotropin-releasing factor receptor type 1 is established in the endoplasmic reticulum
Teichmann, A., Gibert, A., Lampe, A., Grzesik, P., Rutz, C., Furkert, J., Schmoranzer, J., Krause, G., Wiesner, B.; Schülein, R.
J Biol Chem, 289:24250-24262

Tags: Protein Trafficking (Schülein), Cellular Imaging (Wiesner), Structural Bioinformatics and Protein Design (Krause, G.), Molecular Pharmacology and Cell Biology (Haucke)

Abstract: G protein-coupled receptors (GPCRs) represent the most important drug targets. Although the smallest functional unit of a GPCR is a monomer, it became clear in the past decades that the vast majority of the receptors form dimers. Only very recently, however, data were presented that some receptors may in fact be expressed as a mixture of monomers and dimers and that the interaction of the receptor protomers is dynamic. To date, equilibrium measurements were restricted to the plasma membrane due to experimental limitations. We have addressed the question as to where this equilibrium is established for the corticotropin-releasing factor receptor type 1. By developing a novel approach to analyze single molecule fluorescence cross-correlation spectroscopy data for intracellular membrane compartments, we show that the corticotropin-releasing factor receptor type 1 has a specific monomer/dimer equilibrium that is already established in the endoplasmic reticulum (ER). It remains constant at the plasma membrane even following receptor activation. Moreover, we demonstrate for seven additional GPCRs that they are expressed in specific but substantially different monomer/dimer ratios. Although it is well known that proteins may dimerize in the ER in principle, our data show that the ER is also able to establish the specific monomer/dimer ratios of GPCRs, which sheds new light on the functions of this compartment.

Molecular and structural transmembrane determinants critical for embedding claudin-5 into tight junctions reveal a distinct four-helix bundle arrangement
Rossa, J., Protze, J., Kern, C., Piontek, A., Günzel(*), D., Krause, G.; Piontek(*), J.
Biochem J, 464:49-60

Tags: Structural Bioinformatics and Protein Design (Krause, G.)

Abstract: The mechanism of TJ (tight junction) assembly and the structure of TJ strand-forming Cldns (claudins) are unclear. To identify determinants of assembly of blood-brain barrier-related Cldn3 and Cldn5, chimaeric mutants were analysed by cellular reconstitution of TJ strands and live-cell imaging. On the basis of the rescue of mutants deficient for strand formation, we identified Cldn5 residues (Cys128, Ala132, Ile142, Ala163, Ile166 and Leu174) involved in Cldn folding and assembly. Experimental results were combined with structural bioinformatics approaches. Initially the experimentally validated previous model of the ECL2 (extracellular loop 2) of Cldn5 was extended to the flanking transmembrane segments (TM3/TM4). A coiled-coil interface probably caused by alternating small and large residues is supported by concomitant knob-into-hole interactions including Cldn5-specific residues identified in the present paper. To address arrangement of the TMs in a four-helix bundle, data from evolutionary sequence couplings and comparative modelling of intramolecular interfaces in the transmembrane region of Cldns led to a complete Cldn5 model. Our suggested Cldn subtype-specific intramolecular interfaces that are formed by conserved coiled-coil motifs and non-conserved residues in distinct TM positions were confirmed by the recently released crystal structure of Cldn15. The identified molecular and structural determinants essentially contribute to assembly of Cldns into TJ strands.

Claudin-3 and claudin-5 protein folding and assembly into the tight junction are controlled by non-conserved residues in the transmembrane 3 (TM3) and extracellular loop 2 (ECL2) segments
Rossa, J., Ploeger, C., Vorreiter, F., Saleh, T., Protze, J., Günzel, D., Wolburg, H., Krause, G.; Piontek, J.
J Biol Chem, 289:7641-7653

Tags: Structural Bioinformatics and Protein Design (Krause, G.)

Abstract: The mechanism of tight junction (TJ) assembly and the structure of claudins (Cldn) that form the TJ strands are unclear. This limits the molecular understanding of paracellular barriers and strategies for drug delivery across tissue barriers. Cldn3 and Cldn5 are both common in the blood-brain barrier but form TJ strands with different ultrastructures. To identify the molecular determinants of folding and assembly of these classic claudins, Cldn3/Cldn5 chimeric mutants were generated and analyzed by cellular reconstitution of TJ strands, live cell confocal imaging, and freeze-fracture electron microscopy. A comprehensive screening was performed on the basis of the rescue of mutants deficient for strand formation. Cldn3/Cldn5 residues in transmembrane segment 3, TM3 (Ala-127/Cys-128, Ser-136/Cys-137, Ser-138/Phe-139), and the transition of TM3 to extracellular loop 2, ECL2 (Thr-141/Ile-142) and ECL2 (Asn-148/Asp-149, Leu-150/Thr-151, Arg-157/Tyr-158), were identified to be involved in claudin folding and/or assembly. Blue native PAGE and FRET assays revealed 1% n-dodecyl beta-d-maltoside-resistant cis-dimerization for Cldn5 but not for Cldn3. This homophilic interaction was found to be stabilized by residues in TM3. The resulting subtype-specific cis-dimer is suggested to be a subunit of polymeric TJ strands and contributes to the specific ultrastructure of the TJ detected by freeze-fracture electron microscopy. In particular, the Cldn5-like exoplasmic face-associated and particle-type strands were found to be related to cis-dimerization. These results provide new insight into the mechanisms of paracellular barrier formation by demonstrating that defined non-conserved residues in TM3 and ECL2 of classic claudins contribute to the formation of TJ strands with differing ultrastructures.

AhR sensing of bacterial pigments regulates antibacterial defence
Moura-Alves(*), P., Fae(*), K., Houthuys(*), E., Dorhoi(*), A., Kreuchwig, A., Furkert, J., Barison(*), N., Diehl, A., Munder(*), A., Constant, P., Skrahina(*), T., Guhlich-Bornhof(*), U., Klemm(*), M., Koehler(*), A. B., Bandermann(*), S., Goosmann(*), C., Mollenkopf(*), H. J., Hurwitz(*), R., Brinkmann(*), V., Fillatreau(*), S., Daffe(*), M., Tummler, B., Kolbe(*), M., Oschkinat, H., Krause, G.; Kaufmann(*), S. H.
Nature, 512:387-392

Tags: Structural Bioinformatics and Protein Design (Krause, G.), NMR-Supported Structural Biology (Oschkinat), Protein Trafficking (Schülein)

Abstract: The aryl hydrocarbon receptor (AhR) is a highly conserved ligand-dependent transcription factor that senses environmental toxins and endogenous ligands, thereby inducing detoxifying enzymes and modulating immune cell differentiation and responses. We hypothesized that AhR evolved to sense not only environmental pollutants but also microbial insults. We characterized bacterial pigmented virulence factors, namely the phenazines from Pseudomonas aeruginosa and the naphthoquinone phthiocol from Mycobacterium tuberculosis, as ligands of AhR. Upon ligand binding, AhR activation leads to virulence factor degradation and regulated cytokine and chemokine production. The relevance of AhR to host defence is underlined by heightened susceptibility of AhR-deficient mice to both P. aeruginosa and M. tuberculosis. Thus, we demonstrate that AhR senses distinct bacterial virulence factors and controls antibacterial responses, supporting a previously unidentified role for AhR as an intracellular pattern recognition receptor, and identify bacterial pigments as a new class of pathogen-associated molecular patterns.

Differences between lutropin-mediated and choriogonadotropin-mediated receptor activation
Grzesik, P., Teichmann, A., Furkert, J., Rutz, C., Wiesner, B., Kleinau(*), G., Schülein, R., Gromoll(*), J.; Krause, G.
Febs J, 281:1479-1492

Tags: Structural Bioinformatics and Protein Design (Krause, G.), Protein Trafficking (Schülein), Cellular Imaging (Wiesner)

Abstract: The human lutropin/choriogonadotropin receptor (hLHR) for the gonadotropic hormones human luteinizing hormone (hLH; lutropin) and human choriogonadotropin (hCG) is crucial for normal sexual development and fertility. We aimed to unravel differences between the two hLHR hormones in molecular activation mechanisms at hLHR. We utilized a specific hLHR variant that lacks exon 10 (hLHR-delExon10), which maintains full cAMP signaling by hCG, but decreases hLH-induced receptor signaling, resulting in a pathogenic phenotype. Exon 10 encodes 27 amino acids within the hinge region, which is an extracellular segment that is important for signaling and hormone interaction. Initially, we assumed that the lack of exon 10 might disturb intermolecular trans-activation of hLH, a mechanism that has been reported for hCG at hLHR. Coexpression of signaling-deficient hLHR and binding-deficient hLHR can be used to examine the mechanisms of receptor signaling, in particular intermolecular cooperation and intramolecular cis-activation. Therefore, hLHR-delExon10 was combined with the hLHR Lys605-->Glu mutant, in which signaling is abolished, and the hLHR mutant Cys131-->Arg, in which binding is deficient. We found that hCG signaling was partially rescued, indicating trans-activation. However, the hLH signal could not be restored via forced trans-activation with any construct. Fluorescence cross-correlation spectroscopy detected oligomerization in all combinations, indicating that these functional differences cannot be explained by monomerization of hLHR-delExon10. Thus, our data demonstrate not only that the different behavior of hLH at hLHR-delExon10 is unlikely to be related to modified intermolecular receptor activation, but also that hLH may exclusively stimulate the targeted hLHR by cis-activation, whereas hCG is also capable of inducing trans-activation.

A novel twist in membrane dePHormation
Krauss, M.; Haucke, V.
Dev Cell, 31:3-4

Tags: Molecular Pharmacology and Cell Biology (Haucke)

Abstract: Bin-Amphiphysin-Rvs (BAR) domain-containing proteins form oligomeric assemblies that aid membrane remodeling. In this issue of Developmental Cell, Pang et al. (2014) show that the BAR domain of ACAP1, although architecturally similar to other BAR domains, cooperates with its neighboring pleckstrin homology domain to deform membranes and facilitate endosomal recycling.

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Leibniz-Forschungsinstitut für Molekulare Pharmakologie im Forschungsverbund Berlin e.V. (FMP)
Campus Berlin-Buch
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