FMP Publications

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

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Small-molecule screening identifies modulators of aquaporin-2 trafficking
Bogum, J., Faust(*), D., Zühlke, K., Eichhorst, J., Moutty, M. C., Furkert, J., Eldahshan(*), A., Neuenschwander, M., von Kries, J. P., Wiesner, B., Trimpert(*), C., Deen(*), P. M., Valenti(*), G., Rosenthal(*), W.; Klussmann(*), E.
Journal of the American Society of Nephrology : JASN, 24:744-758

Tags: Cellular Imaging (Wiesner), Screening Unit (von Kries), Anchored Signaling (Klussmann)

Abstract: In the principal cells of the renal collecting duct, arginine vasopressin (AVP) stimulates the synthesis of cAMP, leading to signaling events that culminate in the phosphorylation of aquaporin-2 water channels and their redistribution from intracellular domains to the plasma membrane via vesicular trafficking. The molecular mechanisms that control aquaporin-2 trafficking and the consequent water reabsorption, however, are not completely understood. Here, we used a cell-based assay and automated immunofluorescence microscopy to screen 17,700 small molecules for inhibitors of the cAMP-dependent redistribution of aquaporin-2. This approach identified 17 inhibitors, including 4-acetyldiphyllin, a selective blocker of vacuolar H(+)-ATPase that increases the pH of intracellular vesicles and causes accumulation of aquaporin-2 in the Golgi compartment. Although 4-acetyldiphyllin did not inhibit forskolin-induced increases in cAMP formation and downstream activation of protein kinase A (PKA), it did prevent cAMP/PKA-dependent phosphorylation at serine 256 of aquaporin-2, which triggers the redistribution to the plasma membrane. It did not, however, prevent cAMP-induced changes to the phosphorylation status at serines 261 or 269. Last, we identified the fungicide fluconazole as an inhibitor of cAMP-mediated redistribution of aquaporin-2, but its target in this pathway remains unknown. In conclusion, our screening approach provides a method to begin dissecting molecular mechanisms underlying AVP-mediated water reabsorption, evidenced by our identification of 4-acetyldiphyllin as a modulator of aquaporin-2 trafficking.

Culturing Primary Rat Inner Medullary Collecting Duct Cells
Faust(*), D., Geelhaar(*), A., Eisermann(*), B., Eichhorst, J., Wiesner, B., Rosenthal(*), W.; Klussmann(*), E.
Jove-J Vis Exp,

Tags: Cellular Imaging (Wiesner)

Abstract: Arginine-vasopressin (AVP) facilitates water reabsorption by renal collecting duct principal cells and thereby fine-tunes body water homeostasis. AVP binds to vasopressin V2 receptors (V2R) on the surface of the cells and thereby induces synthesis of cAMP. This stimulates cellular signaling processes leading to changes in the phosphorylation of the water channel aquaporin-2 (AQP2). Protein kinase A phoshorylates AQP2 and thereby triggers the translocation of AQP2 from intracellular vesicles into the plasma membrane facilitating water reabsorption from primary urine. Aberrations of AVP release from the pituitary or AVP-activated signaling in principal cells can cause central or nephrogenic diabetes insipidus, respectively; an elevated blood plasma AVP level is associated with cardiovascular diseases such as chronic heart failure and the syndrome of inappropriate antidiuretic hormone secretion. Here, we present a protocol for cultivation of primary rat inner medullary collecting duct (IMCD) cells, which express V2R and AQP2 endogenously. The cells are suitable for elucidating molecular mechanisms underlying the control of AQP2 and thus to discover novel drug targets for the treatment of diseases associated with dysregulation of AVP-mediated water reabsorption. IMCD cells are obtained from rat renal inner medullae and are used for experiments six to eight days after seeding. IMCD cells can be cultured in regular cell culture dishes, flasks and micro-titer plates of different formats, the procedure only requires a few hours, and is appropriate for standard cell culture laboratories.

Combinatorial approach to drastically enhance the monoclonal antibody efficacy in targeted tumor therapy.
Gilabert-Oriol(*), R., Thakur(*), M., von Mallinckrodt(*), B., Hug(*), T., Wiesner, B., Eichhorst, J., Melzig(*), M. F., Fuchs(*), H.; Weng(*), A.
Mol Cancer Ther, 12

Tags: Cellular Imaging (Wiesner)

Modified Trastuzumab and Cetuximab Mediate Efficient Toxin Delivery While Retaining Antibody-Dependent Cell-Mediated Cytotoxicity in Target Cells
Gilabert-Oriol(*), R., Thakur(*), M., von Mallinckrodt(*), B., Hug(*), T., Wiesner, B., Eichhorst, J., Melzig(*), M. F., Fuchs(*), H.; Weng(*), A.
Mol Pharmaceut, 10:4347-4357

Tags: Cellular Imaging (Wiesner)

Abstract: Monoclonal antibody-based therapy is one of the most successful strategies for treatment of cancer. However, the insufficient cell killing activity of monoclonal antibodies limits their therapeutic potential. These limitations can be overcome by the application of immunotoxins, which consist of a monoclonal antibody that specifically delivers a toxin into the cancer cell. An ideal immunotoxin combines the functionality of the monoclonal antibody (antagonistic binding to targeted receptors and interaction with the innate immune system) with the cell-killing activity of the toxic moiety. In addition, it should be sensitive for certain triterpenoid saponins that are known to lead to a tremendous augmentation of the antitumoral efficacy of the immunotoxin. In this study, the monoclonal antibodies trastuzumab (Herceptin) and cetuximab (Erbitux) were conjugated via cleavable disulfide bonds to the plant derived toxin saporin. The ability of the modified tumor-specific therapeutic antibodies to deliver their toxic payload into the target cells was investigated by impedance-based real-time viability assays and confocal live cell imaging. We further provide evidence that the immunotoxins retained their ability to trigger antibody-dependent cell-mediated cytotoxicity. They specifically bound to their target cell receptor, and their cell-killing activity was drastically augmented in the presence of triterpenoid saponins. Further mechanistic studies indicated a specific saponin-mediated endo/lysosomal release of the toxin moiety. These results open a promising avenue to overcome the present limitations of therapeutic antibodies and to achieve a higher antitumoral efficacy in cancer therapy.

Structural insights into the mechanism of GTPase activation in the GIMAP family
Schwefel(*), D., Arasu(*), B. S., Marino(*), S. F., Lamprecht(*), B., Kochert(*), K., Rosenbaum(*), E., Eichhorst, J., Wiesner, B., Behlke(*), J., Rocks(*), O., Mathas(*), S.; Daumke(*), O.
Structure (London, England : 1993), 21:550-559

Tags: Cellular Imaging (Wiesner)

Abstract: GTPases of immunity-associated proteins (GIMAPs) are regulators of lymphocyte survival and homeostasis. We previously determined the structural basis of GTP-dependent GIMAP2 scaffold formation on lipid droplets. To understand how its GTP hydrolysis is activated, we screened for other GIMAPs on lipid droplets and identified GIMAP7. In contrast to GIMAP2, GIMAP7 displayed dimerization-stimulated GTP hydrolysis. The crystal structure of GTP-bound GIMAP7 showed a homodimer that assembled via the G domains, with the helical extensions protruding in opposite directions. We identified a catalytic arginine that is supplied to the opposing monomer to stimulate GTP hydrolysis. GIMAP7 also stimulated GTP hydrolysis by GIMAP2 via an analogous mechanism. Finally, we found GIMAP2 and GIMAP7 expression differentially regulated in several human T cell lymphoma lines. Our findings suggest that GTPase activity in the GIMAP family is controlled by homo- and heterodimerization. This may have implications for the differential roles of some GIMAPs in lymphocyte survival.

Macromolecular interactions of triterpenoids and targeted toxins: Role of saponins charge
Thakur(*), M., Weng(*), A., Pieper(*), A., Mergel(*), K., von Mallinckrodt(*), B., Gilabert-Oriol(*), R., Gorick(*), C., Wiesner, B., Eichhorst, J., Melzig(*), M. F.; Fuchs(*), H.
Int J Biol Macromol, 61:285-294

Tags: Cellular Imaging (Wiesner)

Abstract: Macromolecular interaction of protein toxins with certain plant triterpenoids holds potential for application in tumor therapy. The ability of only certain saponins to enhance the endosomal escape of toxins specifically in tumor cells was evaluated and set into correlation with the electrophoretic mobility. Saponins from Saponaria officinalis Linn, were selected as a lead to understand this evolutionarily conserved principle in detail. Agarose gel electrophoresis was utilized to procure pure saponin fractions with different electrophoretic mobility, which were tested for their ability to enhance the toxicity by live cell monitoring. Five fractions (SOG1-SOG5) were isolated with a relative electrophoretic mobility of (-0.05, 0.41, 0.59, 0.75 and 1.00) and evaluated using thin layer chromatography, HPLC, and mass spectroscopic analysis. Cytotoxicity experiments revealed highest effectiveness with SOG3. Live cell imaging experiments with SOG3 revealed that this saponin with a specific REM of 0.59 could assist in the lyso/endosomal release of the toxic payload without affecting the integrity of plasma membrane and could lead to the induction of apoptosis. This charge dependent enhancement was also found to be highly specific to type I ribosome inactivating proteins compared to bacterial toxins. Charge interaction of plant toxins and saponins with tumor cells, plays a major role in toxin specific modulation of response. The finding opens up newer ways of finding protein saponin interaction conserved evolutionarily and to test their role in endosomal escape of therapeutic molecules. (C) 2013 Elsevier B.V. All rights reserved.

A Well-Defined Pd Hybrid Material for the Z-Selective Semihydrogenation of Alkynes Characterized at the Molecular Level by DNP SENS
Conley(*), M. P., Drost(*), R. M., Baffert(*), M., Gajan(*), D., Elsevier(*), C., Franks, W. T., Oschkinat, H., Veyre(*), L., Zagdoun(*), A., Rossini(*), A., Lelli(*), M., Lesage(*), A., Casano(*), G., Ouari(*), O., Tordo(*), P., Emsley(*), L., Coperet(*), C.; Thieuleux(*), C.
Chem-Eur J, 19:12234-12238

Tags: NMR-Supported Structural Biology (Oschkinat)

Improved Dynamic Nuclear Polarization Surface-Enhanced NMR Spectroscopy through Controlled Incorporation of Deuterated Functional Groups
Zagdoun(*), A., Rossini(*), A. J., Conley(*), M. P., Grüning(*), W. R., Schwarzwälder(*), M., Lelli(*), M., Franks, W. T., Oschkinat, H., Coperet(*), C., Emsley(*), L.; Lesage(*), A.
Angew Chem Int Edit, 52:1222-1225

Tags: NMR-Supported Structural Biology (Oschkinat)

NMR spectroscopy reveals unexpected structural variation at the protein-protein interface in MHC class I molecules
Beerbaum, M., Ballaschk, M., Erdmann, N., Schnick(*), C., Diehl, A., Uchanska-Ziegler(*), B., Ziegler(*), A.; Schmieder, P.
J Biomol NMR, 57:167-178

Tags: Solution NMR (Schmieder)

Abstract: beta2-Microglobulin (beta2m) is a small, monomorphic protein non-covalently bound to the heavy chain (HC) in polymorphic major histocompatibility complex (MHC) class I molecules. Given the high evolutionary conservation of structural features of beta2m in various MHC molecules as shown by X-ray crystallography, beta2m is often considered as a mere scaffolding protein. Using nuclear magnetic resonance (NMR) spectroscopy, we investigate here whether beta2m residues at the interface to the HC exhibit changes depending on HC polymorphisms and the peptides bound to the complex in solution. First we show that human beta2m can effectively be produced in deuterated form using high-cell-density-fermentation and we employ the NMR resonance assignments obtained for triple-labeled beta2m bound to the HLA-B*27:09 HC to examine the beta2m-HC interface. We then proceed to compare the resonances of beta2m in two minimally distinct subtypes, HLA-B*27:09 and HLA-B*27:05, that are differentially associated with the spondyloarthropathy Ankylosing Spondylitis. Each of these subtypes is complexed with four distinct peptides for which structural information is already available. We find that only the resonances at the beta2m-HC interface show a variation of their chemical shifts between the different complexes. This indicates the existence of an unexpected plasticity that enables beta2m to accommodate changes that depend on HC polymorphism as well as on the bound peptide through subtle structural variations of the protein-protein interface.

Potentiation of the Transient Receptor Potential Vanilloid 1 Channel Contributes to Pruritogenesis in a Rat Model of Liver Disease
Belghiti(*), M., Estevez-Herrera(*), J., Gimenez-Garzo(*), C., Gonzalez-Usano(*), A., Montoliu(*), C., Ferrer-Montiel(*), A., Felipo(*), V.; Planells-Cases, R.
Journal of Biological Chemistry, 288:9675-9685

Tags: Physiology and Pathology of Ion Transport (Jentsch)

Abstract: Persistent pruritus is a common disabling dermatologic symptom associated with different etiologic factors. These include primary skin conditions, as well as neuropathic, psychogenic, or systemic disorders like chronic liver disease. Defective clearance of potential pruritogenic substances that activate itch-specific neurons innervating the skin is thought to contribute to cholestatic pruritus. However, because the underlying disease-specific pruritogens and itch-specific neuronal pathways and mechanism(s) are unknown, symptomatic therapeutic intervention often leads to no or only limited success. In the current study, we aimed to first validate rats with bile duct ligation (BDL) as a model for hepatic pruritus and then to evaluate the contribution of inflammation, peripheral neuronal sensitization, and specific signaling pathways and subpopulations of itch-responsive neurons to scratching behavior and thermal hypersensitivity. Chronic BDL rats displayed enhanced scratching behavior and thermal hyperalgesia indicative of peripheral neuroinflammation. BDL-induced itch and hypersensitivity involved a minor contribution of histaminergic/serotonergic receptors, but significant activation of protein-activated receptor 2 (PAR(2)) receptors, prostaglandin PGE(2) formation, and potentiation of transient receptor potential vanilloid 1 (TRPV1) channel activity. The sensitization of dorsal root ganglion nociceptors in BDL rats was associated with increased surface expression of PAR(2) and TRPV1 proteins and an increase in the number of PAR(2)-and TRPV1-expressing peptidergic neurons together with a shift of TRPV1 receptor expression to medium sized dorsal root ganglion neurons. These results suggest that pruritus and hyperalgesia in chronic cholestatic BDL rats are associated with neuroinflammation and involve PAR(2)-induced TRPV1 sensitization. Thus, pharmacological modulation of PAR2 and/or TRPV1 may be a valuable therapeutic approach for patients with chronic liver pruritus refractory to conventional treatments.

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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)

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