FMP Publications

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

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References
Clostridium difficile toxin B inhibits the secretory response of human mast cell line-1 (HMC-1) cells stimulated with high free-Ca(2)(+) and GTPgammaS
Balletta(*), A., Lorenz, D., Rummel(*), A., Gerhard(*), R., Bigalke(*), H.; Wegner(*), F.
Toxicology, 328:48-56
(2015)

Tags: Cellular Imaging (Wiesner)

Abstract: Clostridium difficile toxins A and B (TcdA and TcdB) belong to the class of large clostridial cytotoxins and inactivate by glucosylation some low molecular mass GTPases of the Rho-family (predominantly Rho, Rac and Cdc42), known as regulators of the actin cytoskeleton. TcdA and B also represent the main virulence factors of the anaerobic gram-positive bacterium that is the causal agent of pseudomembranous colitis. In our study, TcdB was chosen instead of TcdA for the well-known higher cytotoxic potency. Inactivation of Rho-family GTPases by this toxin in our experimental conditions induced morphological changes and reduction of electron-dense mast cell-specific granules in human mast cell line-1 (HMC-1) cells, but not cell death or permeabilisation of plasma-membranes. Previously reported patch-clamp dialysis experiments revealed that high intracellular free-Ca(2+) and GTPgammaS concentrations are capable of inducing exocytosis as indicated by significant membrane capacitance (Cm) increases in HMC-1 cells. In this study, we investigated the direct effects of TcdB upon HMC-1 cell "stimulated" Cm increase, as well as on "constitutive" secretion of hexosaminidase and interleukin-16 (IL-16). Compared to untreated control cells, HMC-1 cells incubated with TcdB for 3-24h exhibited a significant reduction of the mean absolute and relative Cm increase in response to free-Ca(2+) and GTPgammaS suggesting an inhibition of secretory processes by TcdB. In conclusion, the HMC-1 cell line represents a suitable model for the study of direct effects of C. difficile toxins on human mast cell secretory activity.

Redox Regulation of Cell Contacts by Tricellulin and Occludin: Redox-Sensitive Cysteine Sites in Tricellulin Regulate Both Tri- and Bicellular Junctions in Tissue Barriers as Shown in Hypoxia and Ischemia
Cording, J., Günther, R., Vigolo(*), E., Tscheik, C., Winkler, L., Schlattner, I., Lorenz, D., Haseloff, R. F., Schmidt-Ott(*), K. M., Wolburg(*), H.; Blasig, I. E.
Antioxid Redox Signal, 23:1035-1049
(2015)

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

Abstract: UNLABELLED: Tight junctions (TJs) seal paracellular clefts in epithelia/endothelia and form tissue barriers for proper organ function. TJ-associated marvel proteins (TAMPs; tricellulin, occludin, marvelD3) are thought to be relevant to regulation. Under normal conditions, tricellulin tightens tricellular junctions against macromolecules. Traces of tricellulin occur in bicellular junctions. AIMS: As pathological disturbances have not been analyzed, the structure and function of human tricellulin, including potentially redox-sensitive Cys sites, were investigated under reducing/oxidizing conditions at 3- and 2-cell contacts. RESULTS: Ischemia, hypoxia, and reductants redistributed tricellulin from 3- to 2-cell contacts. The extracellular loop 2 (ECL2; conserved Cys321, Cys335) trans-oligomerized between three opposing cells. Substitutions of these residues caused bicellular localization. Cys362 in transmembrane domain 4 contributed to bicellular heterophilic cis-interactions along the cell membrane with claudin-1 and marvelD3, while Cys395 in the cytosolic C-terminal tail promoted homophilic tricellullar cis-interactions. The Cys sites included in homo-/heterophilic bi-/tricellular cis-/trans-interactions contributed to cell barrier tightness for small/large molecules. INNOVATION: Tricellulin forms TJs via trans- and cis-association in 3-cell contacts, as demonstrated electron and quantified fluorescence microscopically; it tightens 3- and 2-cell contacts. Tricellulin's ECL2 specifically seals 3-cell contacts redox dependently; a structural model is proposed. CONCLUSIONS: TAMP ECL2 and claudins' ECL1 share functionally and structurally similar features involved in homo-/heterophilic tightening of cell-cell contacts. Tricellulin is a specific redox sensor and sealing element at 3-cell contacts and may compensate as a redox mediator for occludin loss at 2-cell contacts in vivo and in vitro. Molecular interaction mechanisms were proposed that contribute to tricellulin's function. In conclusion, tricellulin is a junctional redox regulator for ischemia-related alterations.

Is transmission electron microscopy (TEM) a promising approach for qualitative and quantitative investigations of polymyxin B and miconazole interactions with cellular and subcellular structures of Staphylococcus pseudintermedius, Escherichia coli, Pseudomonas aeruginosa and Malassezia pachydermatis?
Voget(*), M., Lorenz, D., Lieber-Tenorio(*), E., Hauck(*), R., Meyer(*), M.; Cieslicki(*), M.
Veterinary microbiology, 181:261-270
(2015)

Tags: Cellular Imaging (Wiesner)

Abstract: Antimicrobial therapy using a combination of polymyxin B and miconazole is effective against the main bacterial pathogens associated with otitis externa in dogs, and a synergistic effect of both drugs has been shown previously. The objective of the present investigation was to visualize ultrastructural changes after exposure of Escherichia coli, Pseudomonas aeruginosa, Staphylococcus pseudintermedius and Malassezia pachydermatis to polymyxin B and miconazole by transmission electron microscopic (TEM). For this, cultures of E. coli, P. aeruginosa, S. pseudintermedius and M. pachydermatis were exposed to polymyxin B and miconazole, alone or in combination for 24 h. Ultrastructural changes were observed most frequently in the cell envelope of the four microorganisms. Exposure to polymyxin B seemed to cause more damage than miconazole within the range of concentrations applied. Treatment resulted in changes of the cell size: in E. coli, cell size increased significantly after treatment with either compound alone; in P. aeruginosa, cell size decreased significantly after treatment with polymyxin B and with miconazole; exposure of S. pseudintermedius to miconazole caused a decrease in cell size; in M. pachydermatis, cell size increased significantly after treatment with polymyxin B.; in E.coli, S. pseudintermedius and M. pachydermatis, cell size changed highly significant, in P. aeruginosa significantly after exposure to the combination of both compounds. In conclusion, by using a different approach than previous investigations, this study confirmed a clear combinatory effect of polymyxin B and miconazole against the tested microorganisms involved in canine otitis externa. It is the first time that visualization technologies were applied to compare the effect of single drugs to their combinatory effects on cellular and subcellular entities of selected bacterial and yeast species.

Anchoring dipalmitoyl phosphoethanolamine to nanoparticles boosts cellular uptake and fluorine-19 magnetic resonance signal
Waiczies(*), S., Lepore(*), S., Sydow, K., Drechsler(*), S., Ku(*), M. C., Martin(*), C., Lorenz, D., Schütz, I., Reimann(*), H. M., Purfurst(*), B., Dieringer(*), M. A., Waiczies(*), H., Dathe, M., Pohlmann(*), A.; Niendorf(*), T.
Sci Rep, 5:8427
(2015)

Tags: Peptide-Lipid-Interaction/ Peptide Transport (Dathe), Molecular Pharmacology and Cell Biology (Haucke), Cellular Imaging (Wiesner)

Abstract: Magnetic resonance (MR) methods to detect and quantify fluorine ((19)F) nuclei provide the opportunity to study the fate of cellular transplants in vivo. Cells are typically labeled with (19)F nanoparticles, introduced into living organisms and tracked by (19)F MR methods. Background-free imaging and quantification of cell numbers are amongst the strengths of (19)F MR-based cell tracking but challenges pertaining to signal sensitivity and cell detection exist. In this study we aimed to overcome these limitations by manipulating the aminophospholipid composition of (19)F nanoparticles in order to promote their uptake by dendritic cells (DCs). As critical components of biological membranes, phosphatidylethanolamines (PE) were studied. Both microscopy and MR spectroscopy methods revealed a striking (at least one order of magnitude) increase in cytoplasmic uptake of (19)F nanoparticles in DCs following enrichment with 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE). The impact of enriching (19)F nanoparticles with PE on DC migration was also investigated. By manipulating the nanoparticle composition and as a result the cellular uptake we provide here one way of boosting (19)F signal per cell in order to overcome some of the limitations related to (19)F MR signal sensitivity. The boost in signal is ultimately necessary to detect and track cells in vivo.

Structural heterogeneity in microcrystalline ubiquitin studied by solid-state NMR
Fasshuber, H. K., Lakomek(*), N. A., Habenstein(*), B., Loquet(*), A., Shi, C., Giller(*), K., Wolff(*), S., Becker(*), S.; Lange, A.
Protein Sci, 24:592-598
(2015)

Tags: Molecular Biophysics (Lange, A.)

Abstract: By applying [1-(13) C]- and [2-(13) C]-glucose labeling schemes to the folded globular protein ubiquitin, a strong reduction of spectral crowding and increase in resolution in solid-state NMR (ssNMR) spectra could be achieved. This allowed spectral resonance assignment in a straightforward manner and the collection of a wealth of long-range distance information. A high precision solid-state NMR structure of microcrystalline ubiquitin was calculated with a backbone rmsd of 1.57 to the X-ray structure and 1.32 A to the solution NMR structure. Interestingly, we can resolve structural heterogeneity as the presence of three slightly different conformations. Structural heterogeneity is most significant for the loop region beta1-beta2 but also for beta-strands beta1, beta2, beta3, and beta5 as well as for the loop connecting alpha1 and beta3. This structural polymorphism observed in the solid-state NMR spectra coincides with regions that showed dynamics in solution NMR experiments on different timescales.

Hybrid Structure of the Type 1 Pilus of Uropathogenic Escherichia coli
Habenstein(*), B., Loquet(*), A., Hwang, S., Giller(*), K., Vasa(*), S. K., Becker(*), S., Habeck(*), M.; Lange, A.
Angew Chem Int Ed Engl, 54:11691-11695
(2015)

Tags: Molecular Biophysics (Lange, A.)

Abstract: Type 1 pili are filamentous protein assemblies on the surface of Gram-negative bacteria that mediate adhesion to host cells during the infection process. The molecular structure of type 1 pili remains elusive on the atomic scale owing to their insolubility and noncrystallinity. Herein we describe an approach for hybrid-structure determination that is based on data from solution-state NMR spectroscopy on the soluble subunit and solid-state NMR spectroscopy and STEM data on the assembled pilus. Our approach is based on iterative modeling driven by structural information extracted from different sources and provides a general tool to access pseudo atomic structures of protein assemblies with complex subunit folds. By using this methodology, we determined the local conformation of the FimA pilus subunit in the context of the assembled type 1 pilus, determined the exact helical pilus architecture, and elucidated the intermolecular interfaces contributing to pilus assembly and stability with atomic detail.

Perspectives for sensitivity enhancement in proton-detected solid-state NMR of highly deuterated proteins by preserving water magnetization
Chevelkov, V., Xiang(*), S. Q., Giller(*), K., Becker(*), S., Lange, A.; Reif(*), B.
J. Biomol. NMR, 61:151-160
(2015)

Tags: Molecular Biophysics (Lange, A.)

Abstract: In this work, we show how the water flip-back approach that is widely employed in solution-state NMR can be adapted to proton-detected MAS solid-state NMR of highly deuterated proteins. The scheme allows to enhance the sensitivity of the experiment by decreasing the recovery time of the proton longitudinal magnetization. The method relies on polarization transfer from non-saturated water to the protein during the inter-scan delay.

Specific 13C labeling of leucine, valine and isoleucine methyl groups for unambiguous detection of long-range restraints in protein solid-state NMR studies
Fasshuber, H. K., Demers, J. P., Chevelkov, V., Giller(*), K., Becker(*), S.; Lange, A.
J Magn Reson, 252:10-19
(2015)

Tags: Molecular Biophysics (Lange, A.)

Abstract: Here we present an isotopic labeling strategy to easily obtain unambiguous long-range distance restraints in protein solid-state NMR studies. The method is based on the inclusion of two biosynthetic precursors in the bacterial growth medium, alpha-ketoisovalerate and alpha-ketobutyrate, leading to the production of leucine, valine and isoleucine residues that are exclusively (13)C labeled on methyl groups. The resulting spectral simplification facilitates the collection of distance restraints, the verification of carbon chemical shift assignments and the measurement of methyl group dynamics. This approach is demonstrated on the type-three secretion system needle of Shigella flexneri, where 49 methyl-methyl and methyl-nitrogen distance restraints including 10 unambiguous long-range distance restraints could be collected. By combining this labeling scheme with ultra-fast MAS and proton detection, the assignment of methyl proton chemical shifts was achieved.

Strategies for solid-state NMR investigations of supramolecular assemblies with large subunit sizes
Fricke, P., Chevelkov, V., Shi, C.; Lange, A.
J Magn Reson, 253:2-9
(2015)

Tags: Molecular Biophysics (Lange, A.)

Abstract: Solid-state NMR is a versatile tool to study structure and dynamics of insoluble and non-crystalline biopolymers. Supramolecular protein assemblies are formed by self-association of multiple copies of single small-sized proteins. Because of their high degree of local order, solid-state NMR spectra of such systems exhibit an unusually high level of resolution, rendering them an ideal target for solid-state NMR investigations. Recently, our group has solved the structure of one particular supramolecular assembly, the type-iii-secretion-system needle. The needle subunit comprises around 80 residues. Many interesting supramolecular assemblies with unknown structure have subunits larger in size, which requires development of tailored solid-state NMR strategies to address their structures. In this "Perspective" article, we provide a view on different approaches to enhance sensitivity and resolution in biological solid-state NMR with a focus on the possible application to supramolecular assemblies with large subunit sizes.

Solid-state NMR, electrophysiology and molecular dynamics characterization of human VDAC2
Gattin(*), Z., Schneider(*), R., Laukat(*), Y., Giller(*), K., Maier(*), E., Zweckstetter(*), M., Griesinger(*), C., Benz(*), R., Becker(*), S.; Lange, A.
J. Biomol. NMR, 61:311-320
(2015)

Tags: Molecular Biophysics (Lange, A.)

Abstract: The voltage-dependent anion channel (VDAC) is the most abundant protein of the outer mitochondrial membrane and constitutes the major pathway for the transport of ADP, ATP, and other metabolites. In this multidisciplinary study we combined solid-state NMR, electrophysiology, and molecular dynamics simulations, to study the structure of the human VDAC isoform 2 in a lipid bilayer environment. We find that the structure of hVDAC2 is similar to the structure of hVDAC1, in line with recent investigations on zfVDAC2. However, hVDAC2 appears to exhibit an increased conformational heterogeneity compared to hVDAC1 which is reflected in broader solid-state NMR spectra and less defined electrophysiological profiles.

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Leibniz-Forschungsinstitut für Molekulare Pharmakologie im Forschungsverbund Berlin e.V. (FMP)
Campus Berlin-Buch
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13125 Berlin, Germany
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