FMP Publications

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

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References
Measurement of backbone hydrogen-deuterium exchange in the type III secretion system needle protein PrgI by solid-state NMR
Chevelkov, V., Giller(*), K., Becker(*), S.; Lange, A.
J Magn Reson, 283:110-116
(2017)

Tags: Molecular Biophysics (Lange, A.)

Abstract: In this report we present site-specific measurements of amide hydrogen-deuterium exchange rates in a protein in the solid state phase by MAS NMR. Employing perdeuteration, proton detection and a high external magnetic field we could adopt the highly efficient Relax-EXSY protocol previously developed for liquid state NMR. According to this method, we measured the contribution of hydrogen exchange on apparent 15N longitudinal relaxation rates in samples with differing D2O buffer content. Differences in the apparent T1 times allowed us to derive exchange rates for multiple residues in the type III secretion system needle protein.

Backbone assignment of perdeuterated proteins by solid-state NMR using proton detection and ultrafast magic-angle spinning
Fricke, P., Chevelkov, V., Zinke, M., Giller(*), K., Becker(*), S.; Lange, A.
Nat Protoc, 12:764-782
(2017)

Tags: Molecular Biophysics (Lange, A.)

Abstract: Solid-state NMR (ssNMR) is a technique that allows the study of protein structure and dynamics at atomic detail. In contrast to X-ray crystallography and cryo-electron microscopy, proteins can be studied under physiological conditions-for example, in a lipid bilayer and at room temperature (0-35 degrees C). However, ssNMR requires considerable amounts (milligram quantities) of isotopically labeled samples. In recent years, 1H-detection of perdeuterated protein samples has been proposed as a method of alleviating the sensitivity issue. Such methods are, however, substantially more demanding to the spectroscopist, as compared with traditional 13C-detected approaches. As a guide, this protocol describes a procedure for the chemical shift assignment of the backbone atoms of proteins in the solid state by 1H-detected ssNMR. It requires a perdeuterated, uniformly 13C- and 15N-labeled protein sample with subsequent proton back-exchange to the labile sites. The sample needs to be spun at a minimum of 40 kHz in the NMR spectrometer. With a minimal set of five 3D NMR spectra, the protein backbone and some of the side-chain atoms can be completely assigned. These spectra correlate resonances within one amino acid residue and between neighboring residues; taken together, these correlations allow for complete chemical shift assignment via a 'backbone walk'. This results in a backbone chemical shift table, which is the basis for further analysis of the protein structure and/or dynamics by ssNMR. Depending on the spectral quality and complexity of the protein, data acquisition and analysis are possible within 2 months.

Trictide, a tricellulin-derived peptide to overcome cellular barriers
Cording, J., Arslan, B., Staat, C., Dithmer, S., Krug(*), S. M., Krüger(*), A., Berndt, P., Günther, R., Winkler, L., Blasig, I. E.; Haseloff, R. F.
Annals of the New York Academy of Sciences,
(2017)

Tags: Molecular Cell Physiology (Blasig, I.E.)

Abstract: The majority of tight junction (TJ) proteins restrict the paracellular permeation of solutes via their extracellular loops (ECLs). Tricellulin tightens tricellular TJs (tTJs) and regulates bicellular TJ (bTJ) proteins. We demonstrate that the addition of recombinantly produced extracellular loop 2 (ECL2) of tricellulin opens cellular barriers. The peptidomimetic trictide, a synthetic peptide derived from tricellulin ECL2, increases the passage of ions, as well as of small and larger molecules up to 10 kDa, between 16 and 30 h after application to human epithelial colorectal adenocarcinoma cell line 2. Tricellulin and lipolysis-stimulated lipoprotein receptor relocate from tTJs toward bTJs, while the TJ proteins claudin-1 and occludin redistribute from bTJs to the cytosol. Analyzing the opening of the tricellular sealing tube by the peptidomimetic using super-resolution stimulated-emission depletion microscopy revealed a tricellulin-free area at the tricellular region. Cis-interactions (as measured by fluorescence resonance energy transfer) of tricellulin-tricellulin (tTJs), tricellulin-claudin-1, tricellulin-marvelD3, and occludin-occludin (bTJs) were strongly affected by trictide treatment. Circular dichroism spectroscopy and molecular modeling suggest that trictide adopts a beta-sheet structure, resulting in a peculiar interaction surface for its binding to tricellulin. In conclusion, trictide is a novel and promising tool for overcoming cellular barriers at bTJs and tTJs with the potential to transiently improve drug delivery.

Mechanism of partial agonism in AMPA-type glutamate receptors
Salazar, H., Eibl, C., Chebli, M.; Plested, A.
Nat Commun, 8:14327
(2017)

Tags: Molecular Neuroscience and Biophysics (Plested)

Abstract: Neurotransmitters trigger synaptic currents by activating ligand-gated ion channel receptors. Whereas most neurotransmitters are efficacious agonists, molecules that activate receptors more weakly-partial agonists-also exist. Whether these partial agonists have weak activity because they stabilize less active forms, sustain active states for a lesser fraction of the time or both, remains an open question. Here we describe the crystal structure of an alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptor (AMPAR) ligand binding domain (LBD) tetramer in complex with the partial agonist 5-fluorowillardiine (FW). We validate this structure, and others of different geometry, using engineered intersubunit bridges. We establish an inverse relation between the efficacy of an agonist and its promiscuity to drive the LBD layer into different conformations. These results suggest that partial agonists of the AMPAR are weak activators of the receptor because they stabilize multiple non-conducting conformations, indicating that agonism is a function of both the space and time domains.

Control of AMPA receptor activity by the extracellular loops of auxiliary proteins
Riva, I., Eibl, C., Volkmer, R., Carbone, A. L.; Plested, A. J.
Elife, 6
(2017)

Tags: Molecular Neuroscience and Biophysics (Plested)

Abstract: At synapses throughout the mammalian brain, AMPA receptors form complexes with auxiliary proteins, including TARPs. However, how TARPs modulate AMPA receptor gating remains poorly understood. We built structural models of TARP-AMPA receptor complexes for TARPs gamma2 and gamma8, combining recent structural studies and de novo structure predictions. These models, combined with peptide binding assays, provide evidence for multiple interactions between GluA2 and variable extracellular loops of TARPs. Substitutions and deletions of these loops had surprisingly rich effects on the kinetics of glutamate-activated currents, without any effect on assembly. Critically, by altering the two interacting loops of gamma2 and gamma8, we could entirely remove all allosteric modulation of GluA2, without affecting formation of AMPA receptor-TARP complexes. Likewise, substitutions in the linker domains of GluA2 completely removed any effect of gamma2 on receptor kinetics, indicating a dominant role for this previously overlooked site proximal to the AMPA receptor channel gate.

Cell-permeable nanobodies for targeted immunolabelling and antigen manipulation in living cells
Herce(*), H. D., Schumacher, D., Schneider, A. F. L., Ludwig(*), A. K., Mann, F. A., Fillies(*), M., Kasper, M. A., Reinke, S., Krause, E., Leonhardt(*), H., Cardoso(*), M. C.; Hackenberger, C. P. R.
Nature chemistry, 9:762-771
(2017)

Tags: Chemical Biology II (Hackenberger), Mass Spectrometry (Krause, E)

Abstract: Functional antibody delivery in living cells would enable the labelling and manipulation of intracellular antigens, which constitutes a long-thought goal in cell biology and medicine. Here we present a modular strategy to create functional cell-permeable nanobodies capable of targeted labelling and manipulation of intracellular antigens in living cells. The cell-permeable nanobodies are formed by the site-specific attachment of intracellularly stable (or cleavable) cyclic arginine-rich cell-penetrating peptides to camelid-derived single-chain VHH antibody fragments. We used this strategy for the non-endocytic delivery of two recombinant nanobodies into living cells, which enabled the relocalization of the polymerase clamp PCNA (proliferating cell nuclear antigen) and tumour suppressor p53 to the nucleolus, and thereby allowed the detection of protein-protein interactions that involve these two proteins in living cells. Furthermore, cell-permeable nanobodies permitted the co-transport of therapeutically relevant proteins, such as Mecp2, into the cells. This technology constitutes a major step in the labelling, delivery and targeted manipulation of intracellular antigens. Ultimately, this approach opens the door towards immunostaining in living cells and the expansion of immunotherapies to intracellular antigen targets.

A straightforward approach to N-substituted-2H-indazol-2-amines through reductive cyclization
Schöne, J., Abed, H. B., Christmann(*), M.; Nazare, M.
Tetrahedron Lett, 58:1633-1635
(2017)

Tags: Medicinal Chemistry (Nazare)

Abstract: A versatile two-step, one-pot reaction to access N-substituted-2H-indazol-2-amine derivatives has been elaborated. A diverse set of analogues was obtained by a sequential hydrazone formation and reductive cyclization in moderate to good yields from readily available starting materials. The strategy tolerates a broad range of substitutions pattern and functional groups allowing further derivatizations. (C) 2017 Elsevier Ltd. All rights reserved.

Emerin self-assembly mechanism: role of the LEM domain
Samson(*), C., Celli(*), F., Hendriks, K., Zinke, M., Essawy(*), N., Herrada(*), I., Arteni(*), A. A., Theillet(*), F. X., Alpha-Bazin(*), B., Armengaud(*), J., Coirault(*), C., Lange, A.; Zinn-Justin(*), S.
Febs J, 284:338-352
(2017)

Tags: Molecular Biophysics (Lange, A.)

Abstract: At the nuclear envelope, the inner nuclear membrane protein emerin contributes to the interface between the nucleoskeleton and the chromatin. Emerin is an essential actor of the nuclear response to a mechanical signal. Genetic defects in emerin cause Emery-Dreifuss muscular dystrophy. It was proposed that emerin oligomerization regulates nucleoskeleton binding, and impaired oligomerization contributes to the loss of function of emerin disease-causing mutants. We here report the first structural characterization of emerin oligomers. We identified an N-terminal emerin region from amino acid 1 to amino acid 132 that is necessary and sufficient for formation of long curvilinear filaments. In emerin monomer, this region contains a globular LEM domain and a fragment that is intrinsically disordered. Solid-state nuclear magnetic resonance analysis identifies the LEM beta-fragment as part of the oligomeric structural core. However, the LEM domain alone does not self-assemble into filaments. Additional residues forming a beta-structure are observed within the filaments that could correspond to the unstructured region in emerin monomer. We show that the delK37 mutation causing muscular dystrophy triggers LEM domain unfolding and increases emerin self-assembly rate. Similarly, inserting a disulfide bridge that stabilizes the LEM folded state impairs emerin N-terminal region self-assembly, whereas reducing this disulfide bridge triggers self-assembly. We conclude that the LEM domain, responsible for binding to the chromatin protein BAF, undergoes a conformational change during self-assembly of emerin N-terminal region. The consequences of these structural rearrangement and self-assembly events on emerin binding properties are discussed.

Helical Polyisocyanopeptides as Lyotropic Liquid Crystals for Measuring Residual Dipolar Couplings
Li(*), G. W., Cao(*), J. M., Zong(*), W., Hu(*), L., Hu(*), M. L., Lei(*), X., Sun, H.; Tan(*), R. X.
Chemistry, 23:7653-7656
(2017)

Tags: Computational Chemistry and Protein Design (Kühne)

Abstract: Residual dipolar couplings (RDC) emerged to be an important structural parameter for organic and biomolecules. Herein, a new helical polyisocyanopeptide (l,l-PIAF-OBn) that forms lyotropic liquid crystals (LLC) in CDCl3 is proposed as a novel weakly orienting medium for acquiring residual dipolar couplings (RDCs) of organic molecules. We demonstrate its application for the structural elucidation of strychnine and triptolide.

Establishment of a Human Blood-Brain Barrier Co-culture Model Mimicking the Neurovascular Unit Using Induced Pluri- and Multipotent Stem Cells
Appelt-Menzel(*), A., Cubukova(*), A., Günther(*), K., Edenhofer(*), F., Piontek(*), J., Krause, G., Stüber(*), T., Walles(*), H., Neuhaus(*), W.; Metzger(*), M.
Stem cell reports, 8:894-906
(2017)

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

Abstract: In vitro models of the human blood-brain barrier (BBB) are highly desirable for drug development. This study aims to analyze a set of ten different BBB culture models based on primary cells, human induced pluripotent stem cells (hiPSCs), and multipotent fetal neural stem cells (fNSCs). We systematically investigated the impact of astrocytes, pericytes, and NSCs on hiPSC-derived BBB endothelial cell function and gene expression. The quadruple culture models, based on these four cell types, achieved BBB characteristics including transendothelial electrical resistance (TEER) up to 2,500 Omega cm2 and distinct upregulation of typical BBB genes. A complex in vivo-like tight junction (TJ) network was detected by freeze-fracture and transmission electron microscopy. Treatment with claudin-specific TJ modulators caused TEER decrease, confirming the relevant role of claudin subtypes for paracellular tightness. Drug permeability tests with reference substances were performed and confirmed the suitability of the models for drug transport studies.

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Leibniz-Forschungsinstitut für Molekulare Pharmakologie im Forschungsverbund Berlin e.V. (FMP)
Campus Berlin-Buch
Robert-Roessle-Str. 10
13125 Berlin, Germany
+4930 94793 - 100 
+4930 94793 - 109 (Fax)
info(at)fmp-berlin.de

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